X-ray reflectivity measurement of interdiffusion in metallic multilayers during rapid heating

DOE PAGES

Liu, J. P.; Kirchhoff, J.; Zhou, L.; ...

2017-06-15

A technique for measuring interdiffusion in multilayer materials during rapid heating using X-ray reflectivity is described. In this technique the sample is bent to achieve a range of incident angles simultaneously, and the scattered intensity is recorded on a fast high-dynamic-range mixed-mode pixel array detector. Heating of the multilayer is achieved by electrical resistive heating of the silicon substrate, monitored by an infrared pyrometer. As an example, reflectivity data from Al/Ni heated at rates up to 200 K s -1 are presented. At short times the interdiffusion coefficient can be determined from the rate of decay of the reflectivity peaks,more » and it is shown that the activation energy for interdiffusion is consistent with a grain boundary diffusion mechanism. At longer times the simple analysis no longer applies because the evolution of the reflectivity pattern is complicated by other processes, such as nucleation and growth of intermetallic phases.« less

Interdiffusion between the L1(2) trialuminides Al66Ti25Mn9 and Al67Ti25Cr8

NASA Technical Reports Server (NTRS)

Kumar, K. S.; Whittenberger, J. D.

1992-01-01

Concentration-distance profiles obtained from Al66Ti25Mn9/Al67Ti25Cr8 diffusion couples are used to determine the interdiffusion coeffients in the temperature range 1373-1073 K. The couples are treated as pseudobinaries, and the diffusion coefficients are determined using the Matano approach. The results are then used to compute the activation energies for diffusion, and a comparison is made with some existing data for the activation energy for creep of Al22Ti8Fe3.

Interdiffusion in a ? superlattice: an exploratory nuclear magnetic resonance study

NASA Astrophysics Data System (ADS)

Li, Y.; Ross, J. W.; McCausland, M. A. H.; Bunbury, D. St. P.; Ward, R. C. C.; Wells, M. R.

1997-07-01

We have carried out an exploratory NMR study of interdiffusion at interfaces between epitaxially grown laminae of rare-earth metals. The system investigated was a terbium - yttrium superlattice grown by molecular-beam epitaxy at 0953-8984/9/29/015/img10. The NMR spectrum of 0953-8984/9/29/015/img11 shows satellites associated with Tb ions with different numbers of Y neighbours and therefore provides information about the yttrium concentration profile resulting from interdiffusion. Our data are interpreted in terms of a model based on thermally activated diffusion and which allows for the progressive decrease in 0953-8984/9/29/015/img12, the RMS diffusion length, from the lowest to the highest interface. The diffusion coefficient, provisionally assumed to be independent of composition, is found to be 0953-8984/9/29/015/img13 at the growth temperature.

Interdiffusion and stress development in single-crystalline Pd/Ag bilayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noah, Martin A., E-mail: m.noah@is.mpg.de; Flötotto, David; Wang, Zumin

Interdiffusion and stress evolution in single-crystalline Pd/single-crystalline Ag thin films were investigated by Auger electron spectroscopy sputter-depth profiling and in-situ X-ray diffraction, respectively. The concentration-dependent chemical diffusion coefficient, as well as the impurity diffusion coefficient of Ag in Pd could be determined in the low temperature range of 356 °C–455 °C. As a consequence of the similarity of the strong concentration-dependences of the intrinsic diffusion coefficients, the chemical diffusion coefficient varies only over three orders of magnitude over the whole composition range, despite the large difference of six orders of magnitude of the self-diffusion coefficients of Ag in Ag and Pd inmore » Pd. It is shown that the Darken-Manning treatment should be adopted for interpretation of the experimental data; the Nernst-Planck treatment yielded physically unreasonable results. Apart from the development of compressive thermal stress, the development of stress in both sublayers separately could be ascribed to compositional stress (tensile in the Ag sublayer and compressive in the Pd sublayer) and dominant relaxation processes, especially in the Ag sublayer. The effect of these internal stresses on the values determined for the diffusion coefficients is shown to be negligible.« less

The effect of polymer architecture on the interdiffusion in thin polymer films

NASA Astrophysics Data System (ADS)

Caglayan, Ayse; Yuan, Guangcui; Satija, Sushil K.; Uhrig, David; Hong, Kunlun; Akgun, Bulent

Branched polymer chains have been traditionally used in industrial applications as additives. Recently they have found applications in electrochromic displays, lithography, biomedical coatings and targeting multidrug resistant bacteria. In some of these applications where they are confined in thin layers, it is important to understand the relation between the mobility and polymer chain architecture to optimize the processing conditions. Earlier interdiffusion measurements on linear and cyclic polymer chains demonstrated the key role of chain architecture on mobility. We have determined the vertical diffusion coefficients of the star polystyrene chains in thin films as a function of number of polymer arms, molecular weight per arm, and film thickness using neutron reflectivity (NR) and compare our results with linear chains of identical total molecular weight. Bilayer samples of 4-arm and 8-arm protonated polystyrenes (hPS) and deuterated polystyrenes (dPS) were used to elucidate the effect of polymer chain architecture on polymer diffusion. NR measurements indicate that the mobility of polymer chains in thin films get faster as the number of polymer arms increases and the arm molecular weight decreases. Both star polymers showed faster interdiffusion compared to their linear analog. Diffusion coefficient of branched PS chains has a weak dependence on the film thickness.

Inter-Diffusion in the Presence of Free Convection

NASA Technical Reports Server (NTRS)

Gupta, Prabhat K.

1999-01-01

Because of their technological importance, establishment of the precise values of interdiffusion coefficients is important in multicomponent fluid systems. Such values are not available because diffusion is influenced by free convection due to compositionally induced density variations. In this project, earth based diffusion experiments are being performed in a viscous fluid system PbO-SiO2 at temperatures between 500-1000 C. This system is chosen because it shows a large variation in density with small changes in composition and is expected to show a large free convection effect. Infinite diffusion couples at different temperatures and times are being studied with different orientations with respect to gravity. Composition fields will be measured using an Electron Microprobe Analyzer and will be compared with the results of a complementary modeling study to extract the values of the true diffusion coefficient from the measured diffusion profiles.

Experimental Determination of Fe-Mg Interdiffusion Coefficients in Orthopyroxene Using Pulsed Laser Ablation and Nanoscale Thin Films

NASA Astrophysics Data System (ADS)

Ter Heege, J. H.; Dohmen, R.; Becker, H.; Chakraborty, S.

2006-12-01

Fe-Mg interdiffusion in silicate minerals is of interest in petrological studies for determining the closure temperature of geothermometers and for determining cooling rates from compositional profiles. It is also relevant for studies of the physical properties of silicates, such as rheology or electrical conductivity, because knowledge of its dependence on oxygen fugacity can aid in the understanding of point defect chemistry. Compositionally zoned orthopyroxenes are common in meteorites, mantle rocks, lower crustal rocks and a variety of plutonic and volcanic igneous rocks. However, experimental difficulties have precluded direct determination of Fe-Mg diffusion rates in orthopyroxenes so far and the available information comes from (1) Mg tracer diffusion coefficients obtained from isotope tracer studies using enriched ^{25}MgO films [1], (2) calculations of interdiffusion rates based on the (diffusion-controlled) order-disorder kinetics measured in orthopyroxene [2], and (3) indirect estimates from the comparison of diffusion widths in coexisting garnets and olivines, in which Fe-Mg diffusion rates are relatively well known [e.g., 3]. We have directly measured Fe-Mg interdiffusion coefficients parallel to the [001] direction in two natural orthopyroxene single crystals (approximately En95Fs5 and En90Fs10) using diffusion couples consisting of an olivine thin film (Fo30Fa70, typically 20 - 50 nm thick) deposited under vacuum on pre-heated, polished and oriented pyroxene single crystals using a pulsed laser ablation deposition technique. Samples were annealed for 4 - 337 hours at 800 - 1100 °C under atmospheric pressure in a continuous flow of CO + CO2 to control the oxygen fugacity between 10-16 and 10^{-12} bar within the stability field of pyroxene. Film thickness and compositional profiles were measured using Rutherford backscattering Spectroscopy (RBS) on reference and annealed samples, and Fe concentration depth profiles were extracted from the RBS spectra and fitted numerically. At an oxygen fugacity of 10-16 bar, Fe-Mg interdiffusion coefficients in the Fs richer orthopyroxene vary between 4.10^{-22} m2/s and 2.10^{-20} m2/s for temperatures between 800 and 1000°C. Diffusion coefficients decrease by a factor of ~ 4 with decreasing oxygen fugacity between 10^{-12} and 10-16 bar at 1000 °C. Comparison of our data with other Fe-Mg diffusion data shows that these diffusion coefficients are (1) similar to Mg tracer diffusion coefficients measured in orthopyroxene at somewhat more reducing (e.g. fO2 = 10-16 to 10^{-19} bar) conditions at the same temperatures [1], (2) similar to Mg tracer diffusion in garnets measured at higher pressures of 10 kbar at an oxygen fugacity corresponding to the C-O equilibrium in graphite present systems [4], and (3) slower than Fe-Mg diffusion rates in olivine by a factor of ~10 at the same oxygen fugacities [5]. Further experiments to quantify the dependence on composition, temperature and oxygen fugacity are in progress. References: [1] Schwandt et al. (1998), Contr. Mineral. Petrol. 130: 390-396; [2] Ganguly and Tazzoli (1994), Am. Mineral. 79: 930-937; [3] Smith and Barron (1991), Am. Mineral. 76: 1950-1963; [4] Ganguly et al. (1998), Contr. Mineral. Petrol. 131: 171-180; [5] Chakraborty (1997), J. Geoph. Res. 102: 12317-12331.

On the accuracy of the interdiffusion coefficient measurements of high-temperature binary mixtures under ISS conditions

NASA Astrophysics Data System (ADS)

Saez, Núria; Ruiz, Xavier; Pallarés, Jordi; Shevtsova, Valentina

2013-04-01

An accelerometric record from the IVIDIL experiment (ESA Columbus module) has exhaustively been studied. The analysis involved the determination of basic statistical properties as, for instance, the auto-correlation and the power spectrum (second-order statistical analyses). Also, and taking into account the shape of the associated histograms, we address another important question, the non-Gaussian nature of the time series using the bispectrum and the bicoherence of the signals. Extrapolating the above-mentioned results, a computational model of a high-temperature shear cell has been performed. A scalar indicator has been used to quantify the accuracy of the diffusion coefficient measurements in the case of binary mixtures involving photovoltaic silicon or liquid Al-Cu binary alloys. Three different initial arrangements have been considered, the so-called interdiffusion, centred thick layer and the lateral thick layer. Results allow us to conclude that, under the conditions of the present work, the diffusion coefficient is insensitive to the environmental conditions, that is to say, accelerometric disturbances and initial shear cell arrangement.

Measurement of the diffusion coefficient of acetone in succinonitrile at its melting point

NASA Technical Reports Server (NTRS)

Chopra, M. A.; Glicksman, M. E.; Singh, N. B.

1988-01-01

The diffusion coefficient of acetone in liquid succinonitrile at 331.1 K was determined using the method of McBain and Dawson (1935). Only dilute mixtures of SCN-acetone were studied. The interdiffusion constant was determined to be 0.0000127 sq cm/s and was essentially independent of the acetone concentration over the range investigated (0.5 to 18 mol pct acetone).

A Study of Interdiffusion in the Fe-C/Ti System Under Equilibrium and Nonequilibrium Conditions

NASA Astrophysics Data System (ADS)

Prasanthi, T. N.; Sudha, C.; Saroja, S.

2017-04-01

In the present study, diffusion behavior under equilibrium and nonequilibrium conditions in a Fe-C/Ti system is studied in the temperature range of 773 K to 1073 K (500 °C to 800 °C). A defect-free weld joint between mild steel (MS) (Fe-0.14 pct C) and Ti Grade 2 obtained by friction welding is diffusion annealed for various durations to study the interdiffusion behavior under equilibrium conditions, while an explosive clad joint is used to study interdiffusion under nonequilibrium conditions. From the elemental concentration profiles obtained across the MS-Ti interface using electron-probe microanalysis and imaging of the interface, the formation of distinct diffusion zones as a function of temperature and time is established. Concentration and temperature dependence of the interdiffusion coefficients ( D( c)) and activation energies are determined. Under equilibrium conditions, the change in molar volume with concentration shows a close match with the ideal Vegard's law, whereas a negative deviation is observed for nonequilibrium conditions. This deviation can be attributed to the formation of secondary phases, which, in turn, alters the D( c) values of diffusing species. Calculations showed that the D 0 and activation energy for interdiffusion under equilibrium is on the order of 10-11 m2/s and 147 kJ/mol, whereas it is far lower in the nonequilibrium case (10-10 m2/s and 117 kJ/mol) in the compositional range of 40 to 50 wt pct Fe, which also manifests as accelerated growth kinetics of the different diffusion zones.

Stress, deformation and diffusion interactions in solids - A simulation study

NASA Astrophysics Data System (ADS)

Fischer, F. D.; Svoboda, J.

2015-05-01

Equations of diffusion treated in the frame of Manning's concept, are completed by equations for generation/annihilation of vacancies at non-ideal sources and sinks, by conservation laws, by equations for generation of an eigenstrain state and by a strain-stress analysis. The stress-deformation-diffusion interactions are demonstrated on the evolution of a diffusion couple consisting of two thin layers of different chemical composition forming a free-standing plate without external loading. The equations are solved for different material parameters represented by the values of diffusion coefficients of individual components and by the intensity of sources and sinks for vacancies. The results of simulations indicate that for low intensity of sources and sinks for vacancies a significant eigenstress state can develop and the interdiffusion process is slowed down. For high intensity of sources and sinks for vacancies a significant eigenstrain state can develop and the eigenstress state quickly relaxes. If the difference in the diffusion coefficients of individual components is high, then the intensity of sources and sinks for vacancies influences the interdiffusion process considerably. For such systems their description only by diffusion coefficients is insufficient and must be completed by a microstructure characterization.

Calculation of Transport Coefficients in Dense Plasma Mixtures

NASA Astrophysics Data System (ADS)

Haxhimali, T.; Cabot, W. H.; Caspersen, K. J.; Greenough, J.; Miller, P. L.; Rudd, R. E.; Schwegler, E. R.

2011-10-01

We use classical molecular dynamics (MD) to estimate species diffusivity and viscosity in mixed dense plasmas. The Yukawa potential is used to describe the screened Coulomb interaction between the ions. This potential has been used widely, providing the basis for models of dense stellar materials, inertial confined plasmas, and colloidal particles in electrolytes. We calculate transport coefficients in equilibrium simulations using the Green- Kubo relation over a range of thermodynamic conditions including the viscosity and the self - diffusivity for each component of the mixture. The interdiffusivity (or mutual diffusivity) can then be related to the self-diffusivities by using a generalization of the Darken equation. We have also employed non-equilibrium MD to estimate interdiffusivity during the broadening of the interface between two regions each with a high concentration of either species. Here we present results for an asymmetric mixture between Ar and H. These can easily be extended to other plasma mixtures. A main motivation for this study is to develop accurate transport models that can be incorporated into the hydrodynamic codes to study hydrodynamic instabilities. We use classical molecular dynamics (MD) to estimate species diffusivity and viscosity in mixed dense plasmas. The Yukawa potential is used to describe the screened Coulomb interaction between the ions. This potential has been used widely, providing the basis for models of dense stellar materials, inertial confined plasmas, and colloidal particles in electrolytes. We calculate transport coefficients in equilibrium simulations using the Green- Kubo relation over a range of thermodynamic conditions including the viscosity and the self - diffusivity for each component of the mixture. The interdiffusivity (or mutual diffusivity) can then be related to the self-diffusivities by using a generalization of the Darken equation. We have also employed non-equilibrium MD to estimate interdiffusivity during the broadening of the interface between two regions each with a high concentration of either species. Here we present results for an asymmetric mixture between Ar and H. These can easily be extended to other plasma mixtures. A main motivation for this study is to develop accurate transport models that can be incorporated into the hydrodynamic codes to study hydrodynamic instabilities. This work was performed under the auspices of the US Dept. of Energy by Lawrence Livermore National Security, LLC under Contract DE-AC52-07NA27344.

Influence of compositional complexity on interdiffusion in Ni-containing concentrated solid-solution alloys

DOE PAGES

Jin, Ke; Zhang, Chuan; Zhang, Fan; ...

2018-03-07

To investigate the compositional effects on thermal-diffusion kinetics in concentrated solid-solution alloys, interdiffusion in seven diffusion couples with alloys from binary to quinary is systematically studied. The alloys with higher compositional complexity exhibit in general lower diffusion coefficients against homologous temperature, however, an exception is found that diffusion in NiCoFeCrPd is faster than in NiCoFeCr and NiCoCr. While the derived diffusion parameters suggest that diffusion in medium and high entropy alloys is overall more retarded than in pure metals and binary alloys, they strongly depend on specific constituents. The comparative features are captured by computational thermodynamics approaches using a self-consistentmore » database.« less

Reaction diffusion in the nickel-chromium-aluminum and cobalt-chromium-aluminum systems

NASA Technical Reports Server (NTRS)

Levine, S. R.

1977-01-01

The effects of MCrAl coating-substrate interdiffusion on oxidation life and the general mutliphase, multicomponent diffusion problem were examined. Semi-infinite diffusion couples that had sources representing coatings and sinks representing gas turbine alloys were annealed at 1,000, 1,095, 1,150, or 1,205 C for as long as 500 hours. The source and sink aluminum and chromium contents and the base metal (cobalt or nickel) determined the parabolic diffusion rate constants of the couples and predicted finite coating lives. The beta source strength concept provided a method (1) for correlating beta recession rate constants with composition; (2) for determining reliable average total, diffusion, and constitutional activation energies; and (3) for calculating interdiffusion coefficients.

Interdiffusion of NaSi—CaAl in peristerite

NASA Astrophysics Data System (ADS)

Yund, Richard A.

1986-01-01

The ‘average’ interdiffusion coefficient (bar D) for NaSi—CaAl exchange in plagioclase for the interval from An0 to An26 was estimated from experimentally determined homogenization times for peristerite exsolution lamellae. The average spacing between adjacent (unlike) lamellae is 554±77 Å. Dry heating in air at 1,100°C for 98 days produced no change in the exsolution microstructure; thus bar D(dry)<10-17 cm2/s. This limit is consistent with the recently reported ‘average’ bar D(dry) values for the Huttenlocher interval (An70 90) at this temperature. At 1.5 GPa with about 0.2 weight percent water added the ‘average’ diffusion coefficient from 1,100°C to 900°C is given by: bar D(wet)=18{-15/+108}(cm2/s) exp (-97±5 (kcal/mol)/RT), where R is the gas constant, and T is °K. This bar D(wet) at 1,100°C is more than three orders of magnitude greater than bar D(dry) for Na- and Ca-rich plagioclases.

Effect of concentration dependence of the diffusion coefficient on homogenization kinetics in multiphase binary alloy systems

NASA Technical Reports Server (NTRS)

Tenney, D. R.; Unnam, J.

1978-01-01

Diffusion calculations were performed to establish the conditions under which concentration dependence of the diffusion coefficient was important in single, two, and three phase binary alloy systems. Finite-difference solutions were obtained for each type of system using diffusion coefficient variations typical of those observed in real alloy systems. Solutions were also obtained using average diffusion coefficients determined by taking a logarithmic average of each diffusion coefficient variation considered. The constant diffusion coefficient solutions were used as reference in assessing diffusion coefficient variation effects. Calculations were performed for planar, cylindrical, and spherical geometries in order to compare the effect of diffusion coefficient variations with the effect of interface geometries. In most of the cases considered, the diffusion coefficient of the major-alloy phase was the key parameter that controlled the kinetics of interdiffusion.

Ion-Exchange Interdiffusion Model with Potential Application to Long-Term Nuclear Waste Glass Performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neeway, James Joseph; Kerisit, Sebastien N.; Liu, Jia

2016-05-05

Abstract: Ion exchange is an integral mechanism influencing the corrosion of glasses. Due to the formation of alteration layers in aqueous conditions, it is difficult to conclusively deconvolute the process of ion exchange from other processes, principally dissolution of the glass matrix. Therefore, we have developed a method to isolate alkali diffusion that involves contacting glass coupons with a solution of 6LiCl dissolved in functionally inert dimethyl sulfoxide. We employ the method at temperatures ranging from 25 to 150 °C with various glass formulations. Glass compositions include simulant nuclear waste glasses, such as SON68 and the international simple glass (ISG),more » glasses in which the nature of the alkali element was varied, and glasses that contained more than one alkali element. An interdiffusion model based on Fick’s second law was developed and applied to all experiments to extract diffusion coefficients. The model expands established models of interdiffusion to the case where multiple types of alkali sites are present in the glass. Activation energies for alkali ion exchange were calculated and the results are in agreement with those obtained in glass strengthening experiments but are nearly five times higher than values reported for diffusion-controlled processes in nuclear waste glass corrosion experiments. A discussion of the root causes for this apparent discrepancy is provided. The interdiffusion model derived from laboratory experiments is expected to be useful for modeling glass corrosion in a geological repository when the silicon concentration is high.« less

Diffusion and phase transformation behavior in poly-synthetically-twinned (PST) titanium-aluminum/titanium diffusion couple

NASA Astrophysics Data System (ADS)

Pan, Ling

Motivated by the great potential applications of gamma titanium aluminide based alloys and the important effect of diffusion on the properties of gamma-TiAl/alpha2-Ti3Al two-phase lamellar structure, we conduct this thesis research to explore the microstructural evolution and interdiffusion behavior, and their correlations in multi-phase solid state diffusion couples made up of pure titanium and polysynthetically-twinned (PST) Ti-49.3 at.% Al "single" crystal, in the temperature range of 973--1173 K. The diffusion couples are prepared by high vacuum hot-pressing, with the diffusion direction parallel to the lamellar planes. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) are employed to observe the microstructure at various interfaces/interphases. A reaction zone (RZ) of polycrystalline alpha 2-Ti3Al phase forms along the PST Ti-Al/Ti bonding interface having a wavy interface with the PST crystal and exhibits deeper penetration in alpha2 lamellae, consisting of many fine alpha2 and secondary gamma laths, than in primary gamma lamellae. Direct measurement of the RZ thickness on SEM back-scattered electron images reveals a parabolic growth of the RZ, indicating a macroscopically diffusion-controlled growth. Concentration profiles from Ti, through the RZ, into the alpha2 lamellae of the PST crystal are measured by quantitative energy-dispersive x-ray spectroscopy (EDS) in a scanning transmission electron microscope (STEM). A plateau of composition adjacent to the RZ/(mixed alpha2 lath in PST) interface forms in the deeply penetrated RZ grains, implying a diffusion barrier crossing the interface and some extent of interface control in the RZ grain growth. The interdiffusion coefficient is evaluated both independent of composition and as a function of composition. No significant concentration dependence of the interdiffusion coefficients is observed using Boltzmann-Matano analysis. The temperature dependence of the interdiffusion coefficients obeys the Arrhenius relationship with a pre-exponential factor of D 0 = (7.56 +/- 7.14) x 10-5 m2/s and an activation enthalpy of Q = 255.6+8.9-8.3 kJ/mol = (2.65 +/- 0.09) eV/atom. The initial nucleation stage of the RZ grains plays an important role in the later microstructural evolution as does the local mass balance. The interfacial energy and the strain energy in the deeply penetrated RZ grains are possible reasons for the plateau.

COSIM: A Finite-Difference Computer Model to Predict Ternary Concentration Profiles Associated With Oxidation and Interdiffusion of Overlay-Coated Substrates

NASA Technical Reports Server (NTRS)

Nesbitt, James A.

2001-01-01

A finite-difference computer program (COSIM) has been written which models the one-dimensional, diffusional transport associated with high-temperature oxidation and interdiffusion of overlay-coated substrates. The program predicts concentration profiles for up to three elements in the coating and substrate after various oxidation exposures. Surface recession due to solute loss is also predicted. Ternary cross terms and concentration-dependent diffusion coefficients are taken into account. The program also incorporates a previously-developed oxide growth and spalling model to simulate either isothermal or cyclic oxidation exposures. In addition to predicting concentration profiles after various oxidation exposures, the program can also be used to predict coating life based on a concentration dependent failure criterion (e.g., surface solute content drops to 2%). The computer code is written in FORTRAN and employs numerous subroutines to make the program flexible and easily modifiable to other coating oxidation problems.

Reaction diffusion in the NiCrAl and CoCrAl systems

NASA Technical Reports Server (NTRS)

Levine, S. R.

1978-01-01

The paper assesses the effect of overlay coating and substrate composition on the kinetics of coating depletion by interdiffusion. This is accomplished by examining the constitution, kinetics and activation energies for a series of diffusion couples primarily of the NiCrAl/Ni-10Cr or CoCrAl/Ni-10Cr type annealed at temperatures in the range 1000-1205 C for times up to 500 hr. A general procedure is developed for analyzing diffusion in multicomponent multiphase systems. It is shown that by introducing the concept of beta-source strength, which can be determined from appropriate phase diagrams, the Wagner solution for consumption of a second phase in a semiinfinite couple is successfully applied to the analysis of MCrAl couples. Thus, correlation of beta-recession rate constants with couple composition, total and diffusional activation energies, and interdiffusion coefficients are determined.

Au/Ti resistors used for Nb/Pb-alloy Josephson junctions. II. Thermal stability

NASA Astrophysics Data System (ADS)

Murakami, Masanori; Kim, K. K.

1984-10-01

In the preceding paper bilayered Au/Ti resistors were found to have excellent electrical stability during storage at room temperature after preannealing at an elevated temperature, which is essential to design logic and memory circuits of Nb/Pb-alloy Josephson junction devices. The resistors could contact directly with the Pb-alloy control lines in which Pb and In atoms which are known to intermix easily with Au atoms are contained. Since Pb and In atoms in the control lines are separated from Au atoms of the resistors by thin Ti layers, thermal stability at the contacts is a major concern for use of the Au/Ti resistor material in the Josephson devices. In the present study, surface morphology change and diffusion mechanism at the resistor/control-line contacts were studied using x-ray diffraction and scanning electron microscopy for square-shaped Au/Ti resistors covered by Pb-In layers. The samples were isothermally annealed at temperatures ranging from 353 to 423 K. The diffusion did not occur immediately after annealing at these temperatures. After the incubation period, the interdiffusion was observed to initiate at the edges of the resistors facing to the center of the cathode. Significant amounts of the In atoms in the Pb-In layers were observed to diffuse into the Au layers of the resistors, forming AuIn2 compounds under the Ti layers. By measuring growth rates of the AuIn2 layers, the diffusion coefficients and the activation energy for the layer growth were determined. Also, by analyzing changes in the In concentration in the Pb-In layers during annealing, interdiffusion coefficients of In atoms in the Pb-In layers were determined using a computer simulation technique. The activation energy was about 1.1 eV. Since these diffusion coefficients were found to be very close to those determined previously in bulk materials, the diffusion kinetics is believed to be controlled by the lattice diffusion. Based on the present results, several methods to reduce the interdiffusion between Pb-alloy and Au/Ti resistors were proposed.

Interdiffusion in nanometer-scale multilayers investigated by in situ low-angle x-ray diffraction

NASA Astrophysics Data System (ADS)

Wang, Wei-Hua; Bai, Hai Yang; Zhang, Ming; Zhao, J. H.; Zhang, X. Y.; Wang, W. K.

1999-04-01

An in situ low-angle x-ray diffraction technique is used to investigate interdiffusion phenomena in various metal-metal and metal-amorphous Si nanometer-scale compositionally modulated multilayers (ML's). The temperature-dependent interdiffusivities are obtained by accurately monitoring the decay of the first-order modulation peak as a function of annealing time. Activation enthalpies and preexponential factors for the interdiffusion in the Fe-Ti, Ag-Bi, Fe-Mo, Mo-Si, Ni-Si, Nb-Si, and Ag-Si ML's are determined. Activation enthalpies and preexponential factors for the interdiffusion in the ML's are very small compared with that in amorphous alloys and crystalline solids. The relation between the atomic-size difference and interdiffusion in the ML's are investigated. The observed interdiffusion characteristics are compared with that in amorphous alloys and crystalline α-Zr, α-Ti, and Si. The experimental results suggest that a collective atomic-jumping mechanism govern the interdiffusion in the ML's, the collective proposal involving 8-15 atoms moving between extended nonequilibrium defects by thermal activation. The role of the interdiffusion in the solid-state reaction in the ML's is also discussed.

On the role of structure-dynamic relationship in determining the excess entropy of mixing and chemical ordering in binary square-well liquid alloys

NASA Astrophysics Data System (ADS)

Lalneihpuii, R.; Shrivastava, Ruchi; Mishra, Raj Kumar

2018-05-01

Using statistical mechanical model with square-well (SW) interatomic potential within the frame work of mean spherical approximation, we determine the composition dependent microscopic correlation functions, interdiffusion coefficients, surface tension and chemical ordering in Ag-Cu melts. Further Dzugutov universal scaling law of normalized diffusion is verified with SW potential in binary mixtures. We find that the excess entropy scaling law is valid for SW binary melts. The partial and total structure factors in the attractive and repulsive regions of the interacting potential are evaluated and then Fourier transformed to get partial and total radial distribution functions. A good agreement between theoretical and experimental values for total structure factor and the reduced radial distribution function are observed, which consolidates our model calculations. The well-known Bhatia-Thornton correlation functions are also computed for Ag-Cu melts. The concentration-concentration correlations in the long wavelength limit in liquid Ag-Cu alloys have been analytically derived through the long wavelength limit of partial correlation functions and apply it to demonstrate the chemical ordering and interdiffusion coefficients in binary liquid alloys. We also investigate the concentration dependent viscosity coefficients and surface tension using the computed diffusion data in these alloys. Our computed results for structure, transport and surface properties of liquid Ag-Cu alloys obtained with square-well interatomic interaction are fully consistent with their corresponding experimental values.

Solution processable broadband transparent mixed metal oxide nanofilm optical coatings via substrate diffusion doping.

PubMed

Glynn, Colm; Aureau, Damien; Collins, Gillian; O'Hanlon, Sally; Etcheberry, Arnaud; O'Dwyer, Colm

2015-12-21

Devices composed of transparent materials, particularly those utilizing metal oxides, are of significant interest due to increased demand from industry for higher fidelity transparent thin film transistors, photovoltaics and a myriad of other optoelectronic devices and optics that require more cost-effective and simplified processing techniques for functional oxides and coatings. Here, we report a facile solution processed technique for the formation of a transparent thin film through an inter-diffusion process involving substrate dopant species at a range of low annealing temperatures compatible with processing conditions required by many state-of-the-art devices. The inter-diffusion process facilitates the movement of Si, Na and O species from the substrate into the as-deposited vanadium oxide thin film forming a composite fully transparent V0.0352O0.547Si0.4078Na0.01. Thin film X-ray diffraction and Raman scattering spectroscopy show the crystalline component of the structure to be α-NaVO3 within a glassy matrix. This optical coating exhibits high broadband transparency, exceeding 90-97% absolute transmission across the UV-to-NIR spectral range, while having low roughness and free of surface defects and pinholes. The production of transparent films for advanced optoelectronic devices, optical coatings, and low- or high-k oxides is important for planar or complex shaped optics or surfaces. It provides opportunities for doping metal oxides to ternary, quaternary or other mixed metal oxides on glass, encapsulants or other substrates that facilitate diffusional movement of dopant species.

COSIM: A Finite-Difference Computer Model to Predict Ternary Concentration Profiles Associated with Oxidation and Interdiffusion of Overlay-Coated Substrates

NASA Technical Reports Server (NTRS)

Nesbitt, James A.

2000-01-01

A finite-difference computer program (COSIM) has been written which models the one-dimensional, diffusional transport associated with high-temperature oxidation and interdiffusion of overlay-coated substrates. The program predicts concentration profiles for up to three elements in the coating and substrate after various oxidation exposures. Surface recession due to solute loss is also predicted. Ternary cross terms and concentration-dependent diffusion coefficients are taken into account. The program also incorporates a previously-developed oxide growth and spalling model to simulate either isothermal or cyclic oxidation exposures. In addition to predicting concentration profiles after various oxidation exposures, the program can also be used to predict coating fife based on a concentration dependent failure criterion (e.g., surface solute content drops to two percent). The computer code, written in an extension of FORTRAN 77, employs numerous subroutines to make the program flexible and easily modifiable to other coating oxidation problems.

The determination of extinction coefficient of CuInS2, and ZnCuInS3 multinary nanocrystals.

PubMed

Qin, Lei; Li, Dongze; Zhang, Zhuolei; Wang, Kefei; Ding, Hong; Xie, Renguo; Yang, Wensheng

2012-10-21

A pioneering work for determining the extinction coefficient of colloidal semiconductor nanocrystals (NCs) has been cited over 1500 times (W. Yu, W. Guo, X. G. Peng, Chem. Mater., 2003, 15, 2854-2860), indicating the importance of calculating NC concentration for further research and applications. In this study, the size-dependent nature of the molar extinction coefficient of "greener" CuInS(2) and ZnCuInS(3) NCs with emission covering the whole visible to near infrared (NIR) is presented. With the increase of NC size, the resulting quantitative values of the extinction coefficients of ternary CuInS(2) and quaternary ZnCuInS(3) NCs are found to follow a power function with exponents of 2.1 and 2.5, respectively. Obviously, a larger value of extinction coefficient is observed in quaternary NCs for the same size of particles. The difference of the extinction coefficient from both samples is clearly demonstrated due to incorporating ZnS with a much larger extinction coefficient into CuInS(2) NCs.

High Performance Brittle Matrices and Brittle Matrix Composites. Book 1

DTIC Science & Technology

1989-12-31

Intermetallic Alloys II, p . 27- 38, Stoloft, Koch, Liu, and Izumi (Eds.), MRS, 1986. [6] Cahn, R.W., Siemers, P.A., Geiger, J.E., Bardhan , P ., as-reported in ref...diagram were also useful in determining the interdiffusion coefficients of Ta and Al in the P phase. This information has been used for the studies on...from supercooling of the liquid droplets. This hypothesis was supported by the cross- over of the calculated T0 curves for the a, p and y phases in the

Surface and grain boundary interdiffusion in nanometer-scale LSMO/BFO bilayer

NASA Astrophysics Data System (ADS)

Kumar, Virendra; Gaur, Anurag; Choudhary, R. J.; Gupta, Mukul

2016-05-01

Epitaxial 150 nm thick LSMO/BFO bilayer is deposited on STO (100) substrate by pulsed laser deposition, to study magnetoelectric effect. Unexpected low value of room temperature magnetization in bilayer indicates towards the possibility of interdiffusion. Further, sharp fall in the value of TC (53 K) also added our anxiety towards possible interdiffusion in BFO/LSMO system. Low-angle x-ray diffraction technique is used to investigate interdiffusion phenomena, and the temperature-dependent interdiffusivity is obtained by accurately monitoring the decay of the first-order modulation peak as a function of annealing time. It has been found that the diffusivity at different temperatures follows Arrhenius-type behavior. X-ray reflection (XRR) pattern obtained for the bilayer could not be fitted in the Parratt's formalism, which confirms the interdiffusion in it. Depth profiles of 209Bi, 56Fe ions measured by secondary ion mass spectroscope (SIMS) further substantiate the diffusion of these ions from upper BFO layer into lower LSMO layer.

Glide twinning and pseudotwinning in peristerite: Si,Al diffusional stabilization and implications for the peristerite solvus

NASA Astrophysics Data System (ADS)

Brown, William L.

1989-07-01

Albite glide pseudotwins related to grain-boundary stresses have been observed in an exsolved peristerite (Brown 1989). The glide operation transposes the pre-existing periodic oligoclase/albite lamellae and interfaces into a position rotated by only ˜0.5° in the pseudotwins, but transforms the indices from (1bar 80) outside to ( 081) inside the pseudotwin. The pseudotwin is anti-ordered with respect to Al and Si and both it and the transposed interface are unstable. They should revert to the initial state on stress removal. If however the stresses are maintained for a sufficiently long time, the pseudotwins are stabilized by inversion of Si,Al order and re-orientation of the interface by an angle of about 30° into a position close to \\underline {(1bar 80)} . The continuous lamellae break up into a series of discs by diffusion of NaSi and CaAl, the minimum diffusion path being about the same as the thickness of the lamellae. On extrapolating available interdiffusion data in Ab-rich plagioclases to low temperatures, possible diffusion times may be calculated. The calculated times are long so that either the peristerite miscibility gap must be at a higher temperature than previously supposed or the low-temperature interdiffusion coefficients must be higher than the extrapolated experimental ones, or both. From recent data on ordering in albite, the crest of the gap is estimated to lie close to 650 625° C at low pressure and it is possible that interdiffusion under natural conditions is facilitated by hydrogen (protons) in feldspars.

High-fidelity plasma codes for burn physics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cooley, James; Graziani, Frank; Marinak, Marty

Accurate predictions of equation of state (EOS), ionic and electronic transport properties are of critical importance for high-energy-density plasma science. Transport coefficients inform radiation-hydrodynamic codes and impact diagnostic interpretation, which in turn impacts our understanding of the development of instabilities, the overall energy balance of burning plasmas, and the efficacy of self-heating from charged-particle stopping. Important processes include thermal and electrical conduction, electron-ion coupling, inter-diffusion, ion viscosity, and charged particle stopping. However, uncertainties in these coefficients are not well established. Fundamental plasma science codes, also called high-fidelity plasma codes, are a relatively recent computational tool that augments both experimental datamore » and theoretical foundations of transport coefficients. This paper addresses the current status of HFPC codes and their future development, and the potential impact they play in improving the predictive capability of the multi-physics hydrodynamic codes used in HED design.« less

D/H diffusion in serpentine

NASA Astrophysics Data System (ADS)

Pilorgé, Hélène; Reynard, Bruno; Remusat, Laurent; Le Floch, Sylvie; Montagnac, Gilles; Cardon, Hervé

2017-04-01

Interactions between aqueous fluids and ultrabasic rocks are essential processes in a broad range of contexts including hydrothermal alteration on the parent body of carbonaceous chondrites, at mid-oceanic ridge, and in subduction zones. Tracking these processes and understanding reaction kinetics require knowledge of the diffusion of water in rocks, and of isotope fractionation in major minerals forming under hydrous conditions, such as serpentines. We present a study of D/H inter-diffusion in antigorite, a common variety of serpentine. High-temperature (HT) experiments were performed in a belt apparatus at 540˚ C and 3.0 GPa on natural antigorite powders saturated with interstitial D2O. A low-temperature (LT) experiment was performed in diamond anvil cell at 350˚ C and 2.5 GPa on an antigorite single-crystal loaded with pure D2O. D/(D+H) ratios were mapped using Raman spectroscopy for the HT experiment and NanoSIMS for the LT experiment. As antigorite is a phyllosilicate, diffusion coefficients were obtained for crystallographic directions parallel and perpendicular to the antigorite layers (perpendicular and parallel to the c∗-axis, respectively). The equations of D/H inter-diffusion coefficients were determined to be DD/H (m2/s) = 5.04 x 10-5 x exp(-170(±53) (kJ/mol) / RT) and DD/H (m2/s) = 1.52 x 10-7 x exp(-157(±32) (kJ/mol) / RT) perpendicular and along the c∗-axis, respectively, and DD/H (m2/s) = 7.29 x 10-6 x exp(-166(±14) (kJ/mol) / RT) for the bulk diffusivity. These results are similar to those obtained on chlorite, in agreement with the similar crystallographic structures and atomic bonds in the two minerals. Assuming D/H inter-diffusion coefficients for antigorite are the same for all serpentine species, closure temperature and diffusion durations are applied to hydrothermal fields and in CI, CM and CR chondrites. Closure temperatures lie below 300˚ C for terrestrial hydrothermal alteration and depend on serpentine variety because they have different typical grain sizes. They lie below 130˚ C for carbonaceous chondrites, indicating that D/H isotopic exchange may have persisted down to very low temperatures on their parent bodies. D/H isotopic composition may be associated with grain size heterogeneities in carbonaceous chondrites due to protracted alteration of fine-grained material with the lowest closure temperatures (ca 50˚ C).

D/H diffusion in serpentine

NASA Astrophysics Data System (ADS)

Pilorgé, Hélène; Reynard, Bruno; Remusat, Laurent; Le Floch, Sylvie; Montagnac, Gilles; Cardon, Hervé

2017-08-01

Interactions between aqueous fluids and ultrabasic rocks are essential processes in a broad range of contexts including hydrothermal alteration on the parent body of carbonaceous chondrites, at mid-oceanic ridge, and in subduction zones. Tracking these processes and understanding reaction kinetics require knowledge of the diffusion of water in rocks, and of isotope fractionation in major minerals forming under hydrous conditions, such as serpentines. We present a study of D/H inter-diffusion in antigorite, a common variety of serpentine. Experiments were performed in a belt apparatus at 315 °C, 450 °C and 540 °C and at 3.0 GPa on natural antigorite powders saturated with interstitial D2O. An experiment was performed in a diamond anvil cell at 350 °C and 2.5 GPa on an antigorite single-crystal loaded with pure D2O. D/(D + H) ratios were mapped using Raman spectroscopy for the experiments at 315 °C, 450 °C and 540 °C and by NanoSIMS for the experiment at 350 °C. As antigorite is a phyllosilicate, diffusion coefficients were obtained for crystallographic directions parallel and perpendicular to the silicate layers (perpendicular and parallel to the c∗-axis, respectively). Arrhenius relations for D/H inter-diffusion coefficients were determined to be DD/H (m2/s) = 4.71 × 10-2 × exp(-207(-33/+58) (kJ/mol)/RT) and DD/H (m2/s) = 1.61 × 10-4 × exp(-192(-34/+93) (kJ/mol)/RT) perpendicular and parallel to the c∗-axis, respectively, and DD/H (m2/s) = 7.09 × 10-3 × exp(-202(-33/+70) (kJ/mol)/RT) for the bulk diffusivity. Assuming D/H inter-diffusion coefficients for antigorite are the same for all serpentine species, closure temperature and diffusion durations are applied to hydrothermal alteration in the oceanic lithosphere, and in CI, CM and CR chondrites. Closure temperatures lie below 300 °C for terrestrial hydrothermal alteration and depend on serpentine variety because they have different typical grain sizes. Closure temperatures lie below 160 °C for carbonaceous chondrites, indicating that D/H isotopic exchange may have persisted down to very low temperatures in their parent bodies. Local D/H isotopic compositions may be associated with grain size heterogeneities in carbonaceous chondrites due to protracted alteration of fine-grained material with the lowest closure temperatures (ca 80 °C).

Transport, Structural and Mechanical Properties of Quaternary FeVTiAl Alloy

NASA Astrophysics Data System (ADS)

Bhat, Tahir Mohiuddin; Gupta, Dinesh C.

2016-11-01

The electronic, structural, magnetic and transport properties of FeVTiAl quaternary alloy have been investigated within the framework of density functional theory. The material is a completely spin-polarized half-metallic ferromagnet in its ground state with F-43m structure. The structural stability was further confirmed by elastic constants in the cubic phase with high Young's modulus and brittle nature. The present study predicts an energy band gap of 0.72 eV in a localized minority spin channel at equilibrium lattice parameter of 6.00 Å. The transport properties of the material are discussed based on the Seebeck coefficient, and electrical and thermal conductivity coefficients. The alloy presents large values of Seebeck coefficients, ~39 μV K-1 at room temperature (300 K), and has an excellent thermoelectric performance with ZT = ~0.8.

Multicomponent phase-field model for extremely large partition coefficients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Welland, Michael J.; Wolf, Dieter; Guyer, Jonathan E.

2014-01-01

We develop a multicomponent phase-field model specially formulated to robustly simulate concentration variations from molar to atomic magnitudes across an interlace, i.e., partition coefficients in excess of 10±23 such as may be the case with species which are predominant in one phase and insoluble in the other. Substitutional interdiffusion on a normal lattice and concurrent interstitial diffusion are included. The composition in the interlace follows the approach of Kim. Kim, and Suzuki [Phys. Rev. E 60, 7186 (1999)] and is compared to that of Wheeler, Boettinger, and McFadden [Phys. Rev. A 45, 7424 (1992)] in the context of large partitioning.more » The model successfully reproduces analytical solutions for binary diffusion couples and solute trapping for the demonstrated cases of extremely large partitioning.« less

Polymer/fullerene photovoltaic devices: Nanoscale control of the interface by thermally-controlled interdiffusion

NASA Astrophysics Data System (ADS)

Drees, Martin

In this thesis, the interface between the electron donor polymer and the electron acceptor fullerene in organic photovoltaic devices is studied. Starting from a bilayer system of donor and acceptor materials, the proximity of polymer and fullerene throughout the bulk of the devices is improved by inducing an interdiffusion of the two materials by heating the devices in the vicinity of the glass transition temperature of the polymer. In this manner, a concentration gradient of polymer and fullerene throughout the bulk is created. The proximity of a fullerene within 10 nm of any photoexcitation in the polymer ensures that the efficient charge separation occurs. Measurements of the absorption, photoluminescence, and photocurrent spectra as well as I--V characteristics are used to study the interdiffusion and its influence on the efficiency of the photovoltaic devices. In addition, the film morphology is studied on a microscopic level with transmission electron microscopy and with Auger spectroscopy combined with ion beam milling to create a depth profile of the polymer concentration in the film. Initial studies to induce an interdiffusion were done on poly(2-methoxy-5-(2 '-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) as the electron donor polymer and the buckminsterfullerene C60 as the electron acceptor. Interdiffused devices show an order of magnitude photoluminescence quenching with concomitant increase in the photocurrents by an order of magnitude. Variation of the polymer layer thickness shows that the photocurrents increase with decreasing thickness down to 70 nm due to charge transport limitation. The choice of layer thickness in organic photovoltaic devices is critical for optimization of the efficiency. The interdiffusion process is also monitored in situ and a permanent increase in photocurrents is observed during the heat treatment. Transmission electron microscopy (TEM) studies on cross sections of the film reveal that C60 interdiffuses into the MEH-PPV bulk in the form of >10 nm clusters. This clustering of C60 is a result of its tendency to crystallize and the low miscibility of C 60 in MEH-PPV, leading to strong phase separation. To improve the interdiffusion process, the donor polymer is replaced by poly(3-octylthiophene-2,5-diyl) (P3OT), which has a better miscibility with C60. Again, the photocurrents of the interdiffused devices are improved significantly. A monochromatic power conversion efficiency of 1.5% is obtained for illumination of 3.8 mW/cm2 at 470 nm. The polymer concentration in unheated and interdiffused films is studied with Auger spectroscopy in combination with ion beam milling. The concentration profile shows a distinct interface between P3OT and C60 in unheated films and a slow rise of the P3OT concentration throughout a large cross-section of the interdiffused film. TEM studies on P3OT/C60 films show that C60 still has some tendency to form clusters. The results of this thesis demonstrate that thermally-controlled interdiffusion is a viable approach for fabrication of efficient photovoltaic devices through nanoscale control of composition and morphology. These results are also used to draw conclusions about the influence of film morphology on the photovoltaic device efficiency and to identify important issues related to materials choice for the interdiffusion process. Prospective variations in materials choice are suggested to achieve better film morphologies.

Self-diffusivity and interdiffusivity of molten aluminum-copper alloys under pressure, derived from molecular dynamics.

PubMed

Rudd, Robert E; Cabot, William H; Caspersen, Kyle J; Greenough, Jeffrey A; Richards, David F; Streitz, Frederick H; Miller, Paul L

2012-03-01

We use molecular dynamics (MD) to simulate diffusion in molten aluminum-copper (AlCu) alloys. The self-diffusivities and Maxwell-Stefan diffusivities are calculated for AlCu mixtures using the Green-Kubo formulas at temperatures from 1000 to 4000 K and pressures from 0 to 25 GPa, along with additional points at higher temperatures and pressures. The diffusivities are corrected for finite-size effects. The Maxwell-Stefan diffusivity is compared to the diffusivity calculated from the self-diffusivities using a generalization of the Darken equation. We find that the effects of cross-correlation are small. Using the calculated self-diffusivities, we have assessed whether dilute hard-sphere and dilute Lennard-Jones models apply to the molten mixture. Neither of the two dilute gas diffusivities describes the diffusivity in molten Al and Cu. We report generalized analytic models for the self-diffusivities and interdiffusivity (mutual diffusivity) that fit the MD results well. The MD-derived transport coefficients are in good agreement with the available experimental data. We also report MD calculations of the viscosity and an analytic fit to those results. The ionic thermal conductivity is discussed briefly.

Self-diffusivity and interdiffusivity of molten aluminum-copper alloys under pressure, derived from molecular dynamics

NASA Astrophysics Data System (ADS)

Rudd, Robert E.; Cabot, William H.; Caspersen, Kyle J.; Greenough, Jeffrey A.; Richards, David F.; Streitz, Frederick H.; Miller, Paul L.

2012-03-01

We use molecular dynamics (MD) to simulate diffusion in molten aluminum-copper (AlCu) alloys. The self-diffusivities and Maxwell-Stefan diffusivities are calculated for AlCu mixtures using the Green-Kubo formulas at temperatures from 1000 to 4000 K and pressures from 0 to 25 GPa, along with additional points at higher temperatures and pressures. The diffusivities are corrected for finite-size effects. The Maxwell-Stefan diffusivity is compared to the diffusivity calculated from the self-diffusivities using a generalization of the Darken equation. We find that the effects of cross-correlation are small. Using the calculated self-diffusivities, we have assessed whether dilute hard-sphere and dilute Lennard-Jones models apply to the molten mixture. Neither of the two dilute gas diffusivities describes the diffusivity in molten Al and Cu. We report generalized analytic models for the self-diffusivities and interdiffusivity (mutual diffusivity) that fit the MD results well. The MD-derived transport coefficients are in good agreement with the available experimental data. We also report MD calculations of the viscosity and an analytic fit to those results. The ionic thermal conductivity is discussed briefly.

Coupled CaAl-NaSi diffusion in plagioclase feldspar: Experiments and applications to cooling rate speedometry

NASA Astrophysics Data System (ADS)

Grove, Timothy L.; Baker, Michael B.; Kinzler, Rosamond J.

1984-10-01

The rate of CaAl-NaSi interdiffusion in plagioclase feldspar was determined under 1 atm anhydrous conditions over the temperature range 1400° to 1000°C in calcic plagioclase (An 80-81) by homogenizing coherent exsolution lamellae. The dependence of the average interdiffusion coefficient on temperature is given by the expression: D˜ = 10.99 ( cm 2/sec) exp (-123.4( kcal/mol)/RT), (T in °K). This value is for diffusion perpendicular to the (03 1¯) interface of the lamellae. CaAl-NaSi interdiffusion is 4 to 5 orders of magnitude slower than oxygen diffusion in the temperature range 1400° to 1200°C and possibly 10 orders of magnitude slower at subsolidus temperatures. The large differences in diffusion rates explain the apparent contradiction posed by the plagioclases of large layered intrusions ( e.g., the Skaergaard), which retain delicate Ca, Na compositional zoning profiles on the micron scale, but have undergone complete oxygen isotopic exchange with heated meteoric groundwater from the surrounding wall rocks. CaAl-NaSi diffusion is slow, the closure temperature is high (within the solidus-liquidus interval), and Ca-Na zoning is preserved. Oxygen diffusion is faster, the closure temperature is lower (350°-400°C) and the feldspars exchange oxygen with the low-temperature hydrothermal fluids. The complex micron-scale oscillatory zones in plagioclase can also be used as cooling rate speedometers for volcanic and plutonic plagioclase. Cooling histories typical of large mafic intrusions ( e.g. the Stillwater) are slow, begin at high initial temperatures (1200°C) and result in homogenization of oscillatory zones on the scale of 10 microns. The oscillatory zones found in the plagioclase of granodioritic plutons are preserved because cooling is initiated at a lower temperature (1000°C) limiting diffusion to submicron length scales despite the slow cooling rate of the intrusion.

Nanoscopic diffusion studies on III-V compound semiconductor structures: Experiment and theory

NASA Astrophysics Data System (ADS)

Gonzalez Debs, Mariam

The electronic structure of multilayer semiconductor heterostructures is affected by the detailed compositional profiles throughout the structure and at critical interfaces. The extent of interdiffusion across these interfaces places limits on both the processing time and temperatures for many applications based on the resultant compositional profile and associated electronic structure. Atomic and phenomenological methods were used in this work through the combination of experiment and theory to understand the nanoscopic mechanisms in complex heterostructures. Two principal studies were conducted. Tin diffusion in GaAs was studied by fitting complex experimental diffusion profiles to a phenomenological model which involved the diffusion of substitutional and interstitial dopant atoms. A methodology was developed combining both the atomistic model and the use of key features within these experimentally-obtained diffusion profiles to determine meaningful values of the transport and defect reaction rate parameters. Interdiffusion across AlSb/GaSb multi-quantum well interfaces was also studied. The chemical diffusion coefficient characterizing the AlSb/GaSb diffusion couple was quantitatively determined by fitting the observed photoluminescence (PL) peak shifts to the solution of the Schrodinger equation using a potential derived from the solution of the diffusion equation to quantify the interband transition energy shifts. First-principles calculations implementing Density Functional Theory were performed to study the thermochemistry of point defects as a function of local environment, allowing a direct comparison of interfacial and bulk diffusion phenomena within these nanoscopic structures. Significant differences were observed in the Ga and Al vacancy formation energies at the AlSb/GaSb interface when compared to bulk AlSb and GaSb with the largest change found for Al vacancies. The AlSb/GaSb structures were further studied using positron annihilation spectroscopy (PAS) to investigate the role of vacancies in the interdiffusion of Al and Ga in the superlattices. The PL and PAS experimental techniques together with the phenomenological and atomistic modeling allowed for the determination of the underlying mass transport mechanisms at the nanoscale.

The tracer diffusion coefficient of soft nanoparticles in a linear polymer matrix

DOE PAGES

Imel, Adam E.; Rostom, Sahar; Holley, Wade; ...

2017-03-09

The diffusion properties of nanoparticles in polymer nanocomposites are largely unknown and are often difficult to determine experimentally. To address this shortcoming, we have developed a novel method to determine the tracer diffusion coefficient of soft polystyrene nanoparticles in a linear polystyrene matrix. Monitoring the interdiffusion of soft nanoparticles into a linear polystyrene matrix provides the mutual diffusion coefficient of this system, from which the tracer diffusion coefficient of the soft nanoparticle can be determined using the slow mode theory. Utilizing this protocol, the role of nanoparticle molecular weight and rigidity on its tracer diffusion coefficient is provided. These resultsmore » demonstrate that the diffusive behavior of these soft nanoparticles differ from that of star polymers, which is surprising since our recent studies suggest that the nanoparticle interacts with a linear polymer similarly to that of a star polymer. It appears that these deformable nanoparticles mostly closely mimic the diffusive behavior of fractal macromolecular architectures or microgels, where the transport of the nanoparticle relies on the cooperative motion of neighboring linear chains. Finally, the less cross-linked, and thus more deformable, nanoparticles diffuse faster than the more highly crosslinked nanoparticles, presumably because the increased deformability allows the nanoparticle to distort and fit into available space.« less

First-principles investigation of thermodynamic and kinetic properties in titanium-hydrogen system and B2-nickel-alminum compound: Phase stability, point defect complexes and diffusion

NASA Astrophysics Data System (ADS)

Xu, Qingchuan

The purpose of this thesis is to show the technique of predicting thermodynamic and kinetic properties from first-principles using density functional theory (DFT) calculations, cluster expansion methods and Monte Carlo simulations instead of experiments. Two material systems are selected as examples: one is an interstitial system (Ti-H system) and another is a substitutional compound (B2-NiAl alloy). For Ti-H system, this thesis investigated hydride stability, exploring the role of configurational degrees of freedom, zero-point vibrational energy and coherency strains. The tetragonal gamma-TiH phase was predicted to be unstable relative to hcp alpha-Ti and fcc based delta-TiH2. Zero point vibrational energy makes the gamma phase even less stable. The coherency strains between hydride precipitates and alpha-Ti matrix stabilize gamma-TiH relative to alpha-Ti and delta-TiH2. We also found that hydrogen prefers octahedral sites at low hydrogen concentration and tetrahedral sites at high concentration. For B2-NiAl, this thesis investigated the point defects and various diffusion mechanisms. A low barrier collective hop was discovered that could mediate Al diffusion through the anti-structural-bridge (ASB) mechanism. We also found an alternative hop sequence for the migration of a triple defect and a six-jump-cycle than that proposed previously. Going beyond the mean field approximation, we found that the inclusion of interactions among point defects is crucial to predict the concentration of defect complexes. Accounting for interactions among defects and incorporating all diffusion mechanisms proposed for B2-NiAl in Monte Carlo simulation, we calculated tracer diffusion coefficients. For the first time, the relative importance of various diffusion mechanisms is revealed. The ASB hop is the dominant mechanism for Ni in Ni-rich alloy and for Al diffusion in Al-rich alloys. Other mechanisms also play a role to various extents. We also calculated the self and interdiffusion coefficients for B2-NiAl. We found in Al-rich alloys that the thermodynamic factor of Al is much greater than that of Ni while in Ni-rich alloys they are very similar. This difference in thermodynamic factors results in a much higher self-diffusion coefficient of Al compared to that of Ni in Al-rich alloys and also causes two different interdiffusion coefficients.

InGaAs/GaAs Quantum Dots: Effects of Ensemble Interactions, Interdiffusion, Segregation and Proton Irradiation

NASA Technical Reports Server (NTRS)

Leon, R.

2000-01-01

A sumary or recent experimental findings on the effects of interdiffusion, segregation, strained ensemble interactions and proton irradiation on the optical properties of InGaAs/GaAs quantum dots (QDs) are presented.

Annealing effects in plated-wire memory elements. I - Interdiffusion of copper and Permalloy.

NASA Technical Reports Server (NTRS)

Knudson, C. I.; Kench, J. R.

1971-01-01

Results of investigations using X-ray diffraction and electron-beam microprobe techniques have shown that copper and Permalloy platings interdiffuse at low temperatures when plated-wire memory elements are annealed for times as short as 50 hr. Measurable interdiffusion between Permalloy platings and gold substrates does not occur in similar conditions. Both magnetic and compositional changes during aging are found to occur by a thermally activated process with activation energies around 38 kcal/mol. It is shown, however, that copper-diffusion and magnetic-dispersion changes during aging are merely concurrent processes, neither being the other's cause.

Interdiffusion of Polycarbonate in Fused Deposition Modeling Welds

NASA Astrophysics Data System (ADS)

Seppala, Jonathan; Forster, Aaron; Satija, Sushil; Jones, Ronald; Migler, Kalman

2015-03-01

Fused deposition modeling (FDM), a now common and inexpensive additive manufacturing method, produces 3D objects by extruding molten polymer layer-by-layer. Compared to traditional polymer processing methods (injection, vacuum, and blow molding), FDM parts have inferior mechanical properties, surface finish, and dimensional stability. From a polymer processing point of view the polymer-polymer weld between each layer limits the mechanical strength of the final part. Unlike traditional processing methods, where the polymer is uniformly melted and entangled, FDM welds are typically weaker due to the short time available for polymer interdiffusion and entanglement. To emulate the FDM process thin film bilayers of polycarbonate/d-polycarbonate were annealed using scaled times and temperatures accessible in FDM. Shift factors from Time-Temperature Superposition, measured by small amplitude oscillatory shear, were used to calculate reasonable annealing times (min) at temperatures below the actual extrusion temperature. The extent of interdiffusion was then measured using neutron reflectivity. Analogous specimens were prepared to characterize the mechanical properties. FDM build parameters were then related to interdiffusion between welded layers and mechanical properties. Understating the relationship between build parameters, interdiffusion, and mechanical strength will allow FDM users to print stronger parts in an intelligent manner rather than using trial-and-error and build parameter lock-in.

The use of computational thermodynamics for the determination of surface tension and Gibbs-Thomson coefficient of multicomponent alloys

NASA Astrophysics Data System (ADS)

Ferreira, D. J. S.; Bezerra, B. N.; Collyer, M. N.; Garcia, A.; Ferreira, I. L.

2018-04-01

The simulation of casting processes demands accurate information on the thermophysical properties of the alloy; however, such information is scarce in the literature for multicomponent alloys. Generally, metallic alloys applied in industry have more than three solute components. In the present study, a general solution of Butler's formulation for surface tension is presented for multicomponent alloys and is applied in quaternary Al-Cu-Si-Fe alloys, thus permitting the Gibbs-Thomson coefficient to be determined. Such coefficient is a determining factor to the reliability of predictions furnished by microstructure growth models and by numerical computations of solidification thermal parameters, which will depend on the thermophysical properties assumed in the calculations. The Gibbs-Thomson coefficient for ternary and quaternary alloys is seldom reported in the literature. A numerical model based on Powell's hybrid algorithm and a finite difference Jacobian approximation has been coupled to a Thermo-Calc TCAPI interface to assess the excess Gibbs energy of the liquid phase, permitting liquidus temperature, latent heat, alloy density, surface tension and Gibbs-Thomson coefficient for Al-Cu-Si-Fe hypoeutectic alloys to be calculated, as an example of calculation capabilities for multicomponent alloys of the proposed method. The computed results are compared with thermophysical properties of binary Al-Cu and ternary Al-Cu-Si alloys found in the literature and presented as a function of the Cu solute composition.

Structural and Thermodynamic Factors of Suppressed Interdiffusion Kinetics in Multi-component High-entropy Materials

PubMed Central

Chang, Shou-Yi; Li, Chen-En; Huang, Yi-Chung; Hsu, Hsun-Feng; Yeh, Jien-Wei; Lin, Su-Jien

2014-01-01

We report multi-component high-entropy materials as extraordinarily robust diffusion barriers and clarify the highly suppressed interdiffusion kinetics in the multi-component materials from structural and thermodynamic perspectives. The failures of six alloy barriers with different numbers of elements, from unitary Ti to senary TiTaCrZrAlRu, against the interdiffusion of Cu and Si were characterized, and experimental results indicated that, with more elements incorporated, the failure temperature of the barriers increased from 550 to 900°C. The activation energy of Cu diffusion through the alloy barriers was determined to increase from 110 to 163 kJ/mole. Mechanistic analyses suggest that, structurally, severe lattice distortion strains and a high packing density caused by different atom sizes, and, thermodynamically, a strengthened cohesion provide a total increase of 55 kJ/mole in the activation energy of substitutional Cu diffusion, and are believed to be the dominant factors of suppressed interdiffusion kinetics through the multi-component barrier materials. PMID:24561911

Irradiation behavior of the interaction product of U-Mo fuel particle dispersion in an Al matrix

NASA Astrophysics Data System (ADS)

Kim, Yeon Soo; Hofman, G. L.

2012-06-01

Irradiation performance of U-Mo fuel particles dispersed in Al matrix is stable in terms of fuel swelling and is suitable for the conversion of research and test reactors from highly enriched uranium (HEU) to low enriched uranium (LEU). However, tests of the fuel at high temperatures and high burnups revealed obstacles caused by the interaction layers forming between the fuel particle and matrix. In some cases, fission gas filled pores grow and interconnect in the interdiffusion layer resulting in fuel plate failure. Postirradiation observations are made to examine the behavior of the interdiffusion layers. The interdiffusion layers show a fluid-like behavior characteristic of amorphous materials. In the amorphous interdiffusion layers, fission gas diffusivity is high and the material viscosity is low so that the fission gas pores readily form and grow. Based on the observations, a pore formation mechanism is proposed and potential remedies to suppress the pore growth are also introduced.

Mecanismes fondamentaux et dynamique d'interdiffusion dans les boites quantiques auto-assemblees InAs/InP

NASA Astrophysics Data System (ADS)

Dion, Carolyne

This thesis contributes both to the understanding of the fundamental mechanisms driving the intermixing process in the InAs/InP quantum dot (QD) system and to the development of effective intermixing techniques for the integration of these structures into the next generations of optoelectronic devices for optical telecommunications. More specifically, we study the interdiffusion occurring (i) during heterostructure growth and ( ii) under thermal annealing in structures subjected to grown-in defects (GID) introduced into epitaxial layer during growth at reduced temperatures, or damage created by low-energy phosphorus ion implantation (LEII). Interdiffusion is probed using photoluminescence (PL) spectroscopy in conjunction with calculations of optical transition energies obtained from a tight-binding model. These investigations are completed by structural analyses using transmission electron microscopy (TEM). The characterization of the self-assembled QDs produced from the heteroepitaxy of pure InAs on InP reveals that the structures are significantly interdiffused. All structures in a given sample have the same phosphorus concentration, with [P] varying from 6 to 10% depending on growth conditions. We suggest that such substantial P incorporation into InAs during heteroepitaxy results from the surface As/P exchange process as well as strain-driven alloying. We show that GID and LEII-mediated intermixing techniques are both promising for spatially selective band gap tuning of InAs/InP QDs, producing lower annealing temperature threshold for detectable PL modification and PL blueshifts up to ˜ 270 meV. Upon annealing, PL spectra from standard and GID samples exhibit progressive blueshifts without bandwidth broadening. In contrast, PL spectra from LEII samples show the rise of a high energy peak superimposed to the original spectrum, leading to an apparent overall blueshift with significant bandwidth broadening. On the other hand, as confirmed by TEM, the QD shape is found to convert from a truncated pyramid in the as-grown state into either a dome or double-convex lens in annealed GID and LEII samples, respectively. Based on the evolution of PL characteristics and QDs morphology, we demonstrate that thermally-induced intermixing and GID-enhanced intermixing are governed by the transport of group-V interstitials emanating from the InP epilayer, while LEII-enhanced intermixing is dominated by the motion of group-V vacancies released by the implantation damage. Finally, we determine the diffusion coefficients corresponding to these two atomistic diffusion mechanisms. Keywords: Semiconductors, InAs, InP, quantum dots, diffusion, intermixing, photoluminescence, transmission electron microscopy.

Ionic transport in high-energy-density matter

DOE PAGES

Stanton, Liam G.; Murillo, Michael S.

2016-04-08

Ionic transport coefficients for dense plasmas have been numerically computed using an effective Boltzmann approach. Here, we developed a simplified effective potential approach that yields accurate fits for all of the relevant cross sections and collision integrals. These results have been validated with molecular-dynamics simulations for self-diffusion, interdiffusion, viscosity, and thermal conductivity. Molecular dynamics has also been used to examine the underlying assumptions of the Boltzmann approach through a categorization of behaviors of the velocity autocorrelation function in the Yukawa phase diagram. By using a velocity-dependent screening model, we examine the role of dynamical screening in transport. Implications of thesemore » results for Coulomb logarithm approaches are discussed.« less

Supercritical fluid in the mantle transition zone deduced from H-D interdiffusion of wadsleyite

NASA Astrophysics Data System (ADS)

Sun, Wei; Yoshino, Takashi; Sakamoto, Naoya; Yurimoto, Hisayoshi

2018-02-01

Knowledge of the distribution of water in the Earth's mantle is key to understanding the mantle convection and geochemical evolution of the Earth. As wadsleyite and ringwoodite can incorporate large amounts of water in their crystal structures, proton conduction has been invoked to account for the widespread conductive anomalies observed in the mantle wedge, where descending slab stagnates at the transition zone. However, there is a lot of controversy on whether proton conduction by itself is able to explain such anomalies, because of large discrepancy in the extent of the water effect deduced from previous electrical conductivity measurements on hydrous polycrystalline wadsleyite and ringwoodite. Here we report the hydrogen self-diffusion coefficient obtained from H-D interdiffusion experiments in wadsleyite single-crystal couples. Our results demonstrate that the effect of water on the electrical conductivity of wadsleyite is limited and hydrous wadsleyite by itself is unable to explain conductive anomalies in the transition zone. In contrast, the expected hydrogen effective diffusion does not allow the wide propagation of water between the stagnant slab and surrounding mantle, probably leading to persistence of local water saturation and continuous release of supercritical fluids at the stagnant slab roof on geological time scales. This phenomenon provides an alternative explanation for both the high-conductivity and seismic-velocity anomalies observed in the mantle wedge at the transition-zone depth.

Interdiffusion behavior of tungsten or rhenium and group 5 and 6 elements and alloys of the periodic table, part 1. [at dissimilar metal joints

NASA Technical Reports Server (NTRS)

Arcella, F. G.

1974-01-01

Arc cast W, CVD W, CVD Re, and powder metallurgy Re materials were hot isostatically pressure welded to ten different refractory metals and alloys (Cb, Cb-1Zr, Ta, Ta-10W, T-111, ASTAR-811C, W-25Re, Mo-50Re, W-30Re-20Mo, ect.) and thermally aged at 10 to the minus 8th power torr at 1200, 1500, 1630, 1800, and 2000 C for 100 to 2000 hours. Electron beam microprobe analysis was used to characterize the interdiffusion zone width of each couple system as a function of age time and temperature. Extrapolations of interdiffusion zone thickness to 10,000 hours were made. Classic interdiffusion analysis was performed for several of the systems by Boltzmann-Matano analysis. A method of inhibiting Kirkendall voids from forming during thermal ageing of dissimilar metal junctions was devised and experimentally demonstrated. An electron beam weld study of Cb-1Zr to Re and W-25Re demonstrated the limited acceptability of these welds.

Comparison of GPS and Quaternary slip rates: Insights from a new Quaternary fault database for Central Asia

NASA Astrophysics Data System (ADS)

Mohadjer, Solmaz; Ehlers, Todd; Bendick, Rebecca; Mutz, Sebastian

2016-04-01

Previous studies related to the kinematics of deformation within the India-Asia collision zone have relied on slip rate data for major active faults to test kinematic models that explain the deformation of the region. The slip rate data, however, are generally disputed for many of the first-order faults in the region (e.g., Altyn Tagh and Karakorum faults). Several studies have also challenged the common assumption that geodetic slip rates are representative of Quaternary slip rates. What has received little attention is the degree to which geodetic slip rates relate to Quaternary slip rates for active faults in the India-Asia collision zone. In this study, we utilize slip rate data from a new Quaternary fault database for Central Asia to determine the overall relationship between Quaternary and GPS-derived slip rates for 18 faults. The preliminary analysis investigating this relationship uses weighted least squares and a re-sampling analysis to test the sensitivity of this relationship to different data point attributes (e.g., faults associated with data points and dating methods used for estimating Quaternary slip rates). The resulting sample subsets of data points yield a maximum possible Pearson correlation coefficient of ~0.6, suggesting moderate correlation between Quaternary and GPS-derived slip rates for some faults (e.g., Kunlun and Longmen Shan faults). Faults with poorly correlated Quaternary and GPS-derived slip rates were identified and dating methods used for the Quaternary slip rates were examined. Results indicate that a poor correlation between Quaternary and GPS-derived slip rates exist for the Karakorum and Chaman faults. Large differences between Quaternary and GPS slip rates for these faults appear to be connected to qualitative dating of landforms used in the estimation of the Quaternary slip rates and errors in the geomorphic and structural reconstruction of offset landforms (e.g., offset terrace riser reconstructions for Altyn Tagh fault). Other factors such as a low density in the GPS network (e.g., GPS rate based on data from a single station for the Karakorum fault) appear to also contribute to the mismatch observed between the slip rates. Taken together, these results suggest that GPS-derived slip rates are often (but not always) representative of Quaternary slip rates and that the dating methods and sampling approaches used to identify transients in a fault slip rate history should be heavily scrutinized before interpreting the seismic hazards for a region.

First-principles study of high spin-polarization and thermoelectric efficiency of ferromagnetic CoFeCrAs quaternary Heusler alloy

NASA Astrophysics Data System (ADS)

Bhat, Tahir Mohiuddin; Gupta, Dinesh C.

2018-03-01

The ground state properties along with thermodynamic and thermoelectric properties of quaternary CoFeCrAs alloy within the ordered LiMgPdSn-type structure have been investigated by employing first-principles calculations. The alloy offers half-metallic ferromagnet character with an indirect band gap of 1.12 eV in the minority spin state with total spin magnetic moment of 4μB and follows Slater-Pauling relation. Effects on various properties of the material has been studied by the variation of the pressure and temperature. CoFeCrAs tenders large value of the Grüneisen parameter and small value for the thermal expansion coefficient. The materials present high Seebeck coefficient and huge power factor with the room temperature value of ∼-40 μV/K and 18 (1014 μWcm-1 K-2 s-1) respectively, which make CoFeCrAs promising candidate for efficient thermoelectric material.

Kinetics of diffusional droplet growth in a liquid/liquid two-phase system

NASA Technical Reports Server (NTRS)

Baird, James K.; Cain, Judith B.

1993-01-01

This report contains experimental results for the interdiffusion coefficient of the system, succinonitrile plus water, at a number of compositions and temperatures in the single phase region of the phase diagram. The concentration and temperature dependence of the measured diffusion coefficient has been analyzed in terms of Landau - Ginzburg theory, which assumes that the Gibb free energy is an analytic function of its variables, and can be expanded in a Taylor series about any point in the phase diagram. At most points in the single phase region this is adequate. Near the consolute point (critical point of solution), however, the free energy is non-analytic, and the Landau - Ginzburg theory fails. The solution to this problem dictates that the Landau - Ginzburg form of the free energy be replaced by Widom scaling functions with irrational values for the scaling exponents. As our measurements of the diffusion coefficient near the critical point reflect this non-analytic character, we are preparing for publication in a refereed journal a separate analysis of some of the data contained herein as well as some additional measurements we have just completed. When published, reprints of this article will be furnished to NASA.

Contribution of atom-probe tomography to a better understanding of glass alteration mechanisms: Application to a nuclear glass specimen altered 25 years in a granitic environment

DOE PAGES

Gin, Stephane; Ryan, Joseph V.; Schreiber, Daniel K.; ...

2013-04-08

Here, we report and discuss results of atom probe tomography (APT) and energy-filtered transmission electron microscopy (EFTEM) applied to a borosilicate glass sample of nuclear interest altered for nearly 26 years at 90°C in a confined granitic medium in order to better understand the rate-limiting mechanisms under conditions representative of a deep geological repository for vitrified radioactive waste. The APT technique allows the 3D reconstruction of the elemental distribution at the reactive interphase with sub-nanometer precision. Profiles of the B distribution at pristine glass/hydrated glass interface obtained by different techniques are compared to show the challenge of accurate measurements ofmore » diffusion profiles at this buried interface on the nanometer length scale. Our results show that 1) Alkali from the glass and hydrogen from the solution exhibit anti-correlated 15 ± 3 nm wide gradients located between the pristine glass and the hydrated glass layer, 2) boron exhibits an unexpectedly sharp profile located just at the outside of the alkali/H interdiffusion layer; this sharp profile is more consistent with a dissolution front than a diffusion-controlled release of boron. The resulting apparent diffusion coefficients derived from the Li and H profiles are D Li = 1.5 × 10 -22 m 2.s -1 and D H = 6.8 × 10 -23 m 2.s -1. These values are around two orders of magnitude lower than those observed at the very beginning of the alteration process, which suggests that interdiffusion is slowed at high reaction progress by local conditions that could be related to the porous structure of the interphase. As a result, the accessibility of water to the pristine glass could be the rate-limiting step in these conditions. More generally, these findings strongly support the importance of interdiffusion coupled with hydrolysis reactions of the silicate network on the long-term dissolution rate, contrary to what has been suggested by recent interfacial dissolution-precipitation models for silicate minerals.« less

Nucleation of the Widmanstatten Pattern in Iron Meteorites

NASA Technical Reports Server (NTRS)

Yang, J.; Goldstein, J. I.

2004-01-01

The Widmanstatten pattern develops at low temperatures during the evolution of the asteroids. We have studied the origin of the Widmanstatten pattern in order to obtain metallographic cooling rates in the temperature range (approx. 700 to 300 deg C). This paper summarizes our recent evaluation of the various mechanisms for the formation of the Widmanstatten pattern. All chemical groups of the iron meteorites are considered. We also propose a new mechanism for the formation of the Widmanstatten pattern in the low P metal phase of iron, stony-iron and stony meteorites. The results of this evaluation enables us to more accurately determine metallographic cooling rates particularly when incorporated with other recent advances in Fe-Ni and Fe-Ni (P saturated) phase diagrams and interdiffusion coefficients.

Effect of interdiffusion and external magnetic field on electronic states and light absorption in Gaussian-shaped double quantum ring

NASA Astrophysics Data System (ADS)

Aziz-Aghchegala, V. L.; Mughnetsyan, V. N.; Kirakosyan, A. A.

2018-02-01

The effect of interdiffusion and magnetic field on confined states of electron and heavy hole as well as on interband absorption spectrum in a Ga1-xAlxAs/GaAs Gaussian-shaped double quantum ring are investigated. It is shown that both interdiffusion and magnetic field lead to the change of the charge carriers' quantum states arrangement by their energies. The oscillating behavior of the electron ground state energy as a function of magnetic field induction gradually disappears with the increase of diffusion parameter due to the enhanced tunneling of electron to the central region of the ring. For the heavy hole the ground state energy oscillations are not observable in the region of the values of magnetic field induction B = 0 - 10 T . For considered transitions both the magnetic field and the interdiffusion lead to a blue-shift of the absorption spectrum and to decreasing of the absorption intensity. The obtained results indicate on the opportunity of purposeful manipulation of energy states and absorption spectrum of a Gaussian-shaped double quantum ring by means of the post growth annealing and the external magnetic field.

Microstructure studies of interdiffusion behavior of U 3Si 2/Zircaloy-4 at 800 and 1000 °C

DOE PAGES

He, Lingfeng; Harp, Jason M.; Hoggan, Rita E.; ...

2017-01-22

Fuel swelling during normal reactor operations could lead to unfavorable chemical interactions when in contact with its cladding. As new fuel types are developed, it is crucial to understand the interaction behavior between fuel and its cladding. Diffusion experiments between U 3Si 2 and Zricaloy-4 (Zry-4) were conducted at 800 and 1000°C up to 100 hours. The microstructure of pristine U 3Si 2 and U 3Si 2/Zry-4 interdiffusion products were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) equipped with an energy dispersive X-ray spectroscopy (EDS) system. The primary interdiffusion product observed at 800°C is ZrSi 2,more » with secondary phases of U-Zr in the Zry-4, and Fe-Cr-W-Zr-Si phases at Zry-4/ZrSi 2 interface and Fe-Cr-U-Si phases at ZrSi 2/U-Si interface. As a result, the primary interdiffusion products at 1000°C were Zr 2Si, U-Zr-Fe-Ni, U, U-Zr, and a low melting point phase U 6Fe.« less

Multichannel Interdiffusion Driven FASnI3 Film Formation Using Aqueous Hybrid Salt/Polymer Solutions toward Flexible Lead-Free Perovskite Solar Cells.

PubMed

Xi, Jun; Wu, Zhaoxin; Jiao, Bo; Dong, Hua; Ran, Chenxin; Piao, Chengcheng; Lei, Ting; Song, Tze-Bin; Ke, Weijun; Yokoyama, Takamichi; Hou, Xun; Kanatzidis, Mercouri G

2017-06-01

Tin (Sn)-based perovskites are increasingly attractive because they offer lead-free alternatives in perovskite solar cells. However, depositing high-quality Sn-based perovskite films is still a challenge, particularly for low-temperature planar heterojunction (PHJ) devices. Here, a "multichannel interdiffusion" protocol is demonstrated by annealing stacked layers of aqueous solution deposited formamidinium iodide (FAI)/polymer layer followed with an evaporated SnI 2 layer to create uniform FASnI 3 films. In this protocol, tiny FAI crystals, significantly inhibited by the introduced polymer, can offer multiple interdiffusion pathways for complete reaction with SnI 2 . What is more, water, rather than traditional aprotic organic solvents, is used to dissolve the precursors. The best-performing FASnI 3 PHJ solar cell assembled by this protocol exhibits a power conversion efficiency (PCE) of 3.98%. In addition, a flexible FASnI 3 -based flexible solar cell assembled on a polyethylene naphthalate-indium tin oxide flexible substrate with a PCE of 3.12% is demonstrated. This novel interdiffusion process can help to further boost the performance of lead-free Sn-based perovskites. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stuffed MO layer as a diffusion barrier in metallizations for high temperature electronics

NASA Technical Reports Server (NTRS)

Boah, J. K.; Russell, V.; Smith, D. P.

1981-01-01

Auger electron spectroscopy was employed to characterize the diffusion barrier properties of molybdenum in the CrSi2/Mo/Au metallization system. The barrier action of Mo was demonstrated to persist even after 2000 hours annealing time at 300 C in a nitrogen ambient. At 340 C annealing temperature, however, rapid interdiffusion was observed to have occurred between the various metal layers after only 261 hours. The presence of controlled amounts of oxygen in the Mo layer is believed to be responsible for suppressing the short circuit interdiffusion between the thin film layers. Above 340 C, its is believed that the increase in the oxygen mobility led to deterioration of its stuffing action, resulting in the rapid interdiffusion of the thin film layers along grain boundaries.

Thermally Induced Interdiffusion and Precipitation in a Ni/Ni 3 Al System

DOE PAGES

Sun, C.; Martinez, E.; Aguiar, J. A.; ...

2015-05-20

Ordered Ni 3Al intermetallic precipitates constitute the main hardening sources of Ni-based superalloys. Here, we report the interdiffusion and precipitation behavior in a Ni/Ni3Al model system. The deposition of Ni3Al on a pure Ni layer at 500°C generated L12-structured γ' (Ni3Al) precipitates, preferentially at the interface. After annealing at 800°C for 1 h, interdiffusion between Ni and Ni3Al layers occurred, and the γ' precipitates that grew near the parent Ni/Ni 3Al interface are ~2.8 times larger in size than those formed in the matrix. In conclusion, Monte Carlo simulations indicate that vacancies preferentially diffuse along the Ni/Ni 3Al interface, increasingmore » the probability of precipitation.« less

High temperature XRD of Cu2.1Zn0.9SnSe4

NASA Astrophysics Data System (ADS)

Chetty, Raju; Mallik, Ramesh Chandra

2014-04-01

Quaternary compound with chemical composition Cu2.1Zn0.9SnSe4 is prepared by solid state synthesis. High temperature XRD (X-Ray Diffraction) of this compound is used in studying the effect of temperature on lattice parameters and thermal expansion coefficients. Thermal expansion coefficient is one of the important quantities in evaluating the Grüneisen parameter which further useful in determining the lattice thermal conductivity of the material. The high temperature XRD of the material revealed that the lattice parameters as well as thermal expansion coefficients of the material increased with increase in temperature which confirms the presence of anharmonicty.

Characterization and Modeling of Indium Gallium Antimonide Avalanche Photodiode and of Indium Gallium Arsenide Two-band Detector

NASA Technical Reports Server (NTRS)

2006-01-01

A model of the optical properties of Al(x)Ga(1-x)As(y)Sb(1-y) and In(x)Ga(1-x)As(y)Sb(1-y) is presented, including the refractive, extinction, absorption and reflection coefficients in terms of the optical dielectric function of the materials. Energy levels and model parameters for each binary compound are interpolated to obtain the needed ternaries and quaternaries for various compositions. Bowing parameters are considered in the interpolation scheme to take into account the deviation of the calculated ternary and quaternary values from experimental data due to lattice disorders. The inclusion of temperature effects is currently being considered.

The Controversial Role of Inter-diffusion in Glass Alteration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gin, Stephane; Neill, Lindsay; Fournier, M.

2016-11-15

Current kinetic models for nuclear waste glasses (e.g. GM2001, GRAAL) are based on a set of mechanisms that have been generally agreed upon within the international waste glass community. These mechanisms are: hydration of the glass, ion exchange reactions (the two processes are referred as inter-diffusion), hydrolysis of the silicate network, and condensation/precipitation of partly or completely hydrolyzed species that produces a porous and amorphous layer and crystalline phases on surface of the altered glass. Recently, a new idea with origins in the mineral dissolution community has been proposed that excludes inter-diffusion process as a potential rate-limiting mechanism. To understandmore » how the so-called interfacial dissolution/precipitation model can change the current understanding of glass behavior, a key experiment used to account for this model was replicated to further revisit the interpretation. This experiment was performed at 50°C, with SON68 glass, in static mode, deionized water and S/V ratio of 10 m-1 for 6 months. It turn out that glass alters in an intermediate kinetic regime between the forward and the residual rate. According to previous and new solid characterizations, it is concluded that neither a simple inter-diffusion model nor the interfacial dissolution precipitation model can account for the observed elemental profiles within the alteration layer. More generally, far and close-to-saturation conditions must be distinguished and literature provides evidences that inter-diffusion takes place in slightly acidic conditions and far from saturation. However, closer to saturation, when a sufficiently dense layer is formed, a new approach is proposed requiring a full description of chemical reactions taking place within the alteration layer and involving water molecules as it is thought that water accessibility to the pristine glass is the rate-limiting process.« less

Magnetotransport and interdiffusion characteristics of magnetic tunnel junctions comprising nano-oxide layers upon exposure to postdeposition annealing

NASA Astrophysics Data System (ADS)

Chu, In Chang; Song, Min Sung; Chun, Byong Sun; Lee, Seong Rae; Kim, Young Keun

2005-08-01

Magnetic tunnel junction (MTJ) structures based on underlayer (CoNbZr)/bufferlayer (CoFe)/antiferromagnet (IrMn)/pinned layer (CoFe)/tunnel barrier (AlO x)/free layer (CoFe)/capping (CoNbZr) have been prepared to investigate thermal degradation of magnetoresistive responses. Some junctions possess a nano-oxide layer (NOL) inside either in the underlayer or bufferlayer. The main purpose of the NOL inclusion was to control interdiffusion path of Mn from the antiferromagnet so that improved thermal stability could be achieved. The MTJs with NOLs were found to have reduced interfacial roughness, resulting in improved tunneling magnetoresistance (TMR) and reduced interlayer coupling field. We also confirmed that the NOL effectively suppressed the Mn interdiffusion toward the tunnel barrier by dragging Mn atoms toward NOL during annealing.

The Fe2(+)-Mg interdiffusion in orthopyroxene: Constraints from cation ordering and structural data and implications for cooling rates of meteorites

NASA Technical Reports Server (NTRS)

Ganguly, J.; Tazzoli, V.

1993-01-01

Orthopyroxene crystals in a number of meteorites exhibit compositional zoning of Fe and Mg, which provide important constraint on their cooling rates. However, attempts to model cooling rate of these crystals from Fe-Mg zoning profiles suffer from the lack of any measured or theoretically well constrained Fe-Mg interdiffusion data in OP(x) It has been assumed that Fe-Mg interdiffusion in OP(x) only slightly slower than that in olivine. The purpose of this paper is to (1) calculate the Fe-Mg fractionation, and (2) provide analytical formulation relating cooling rate to the length of the diffusion zone across the interface of the overgrowth of a mineral on itself with application to Mg diffusion profile across OP(x) growth on OP(x) in certain mesosiderites.

Influence of Si interdiffusion on carbon-induced growth of Ge quantum dots: a strategy for tuning island density.

PubMed

Bernardi, A; Ossó, J O; Alonso, M I; Goñi, A R; Garriga, M

2006-05-28

We have studied the epitaxial growth of self-assembled Ge quantum dots when a submonolayer of carbon is deposited on a Ge wetting layer (WL) prior to the growth of the dots. Using atomic-force microscopy combined with optical techniques like Raman and ellipsometry, we performed a systematic study of the role played by thermally activated Si interdiffusion on dot density, composition and morphology, by changing only the growth temperature T(WL) of the WL. Strikingly, we observe that higher dot densities and a narrower size distribution are achieved by increasing the deposition temperature T(WL), i.e. by enhancing Si interdiffusion from the substrate. We suggest a two-stage growth procedure for fine tuning of dot topography (density, shape and size) useful for possible optoelectronic applications.

Corrosion resistant coatings suitable for elevated temperature application

DOEpatents

Chan, Kwai S [San Antonio, TX; Cheruvu, Narayana Sastry [San Antonio, TX; Liang, Wuwei [Austin, TX

2012-07-31

The present invention relates to corrosion resistance coatings suitable for elevated temperature applications, which employ compositions of iron (Fe), chromium (Cr), nickel (Ni) and/or aluminum (Al). The compositions may be configured to regulate the diffusion of metals between a coating and a substrate, which may then influence coating performance, via the formation of an inter-diffusion barrier layer. The inter-diffusion barrier layer may comprise a face-centered cubic phase.

Physicochemical properties and solubility of alkyl-(2-hydroxyethyl)-dimethylammonium bromide.

PubMed

Domańska, Urszula; Bogel-Łukasik, Rafał

2005-06-23

Quaternary ammonium salts, which are precursors of ionic liquids, have been prepared from N,N-dimethylethanolamine as a substrate. The paper includes specific basic characterization of synthesized compounds via the following procedures: nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectra, water content, mass spectroscopy (MS) spectra, temperatures of decompositions, basic thermodynamic properties of pure ionic liquids (the melting point, enthalpy of fusion, enthalpy of solid-solid phase transition, glass transition), and the difference in the solute heat capacity between the liquid and solid at the melting temperature determined by differential scanning calorimetry (DSC). The (solid + liquid) phase equilibria of binary mixtures containing (quaternary ammonium salt + water, or + 1-octanol) has been measured by a dynamic method over wide range of temperatures, from 230 K to 560 K. These data were correlated by means of the UNIQUAC ASM and modified nonrandom two-liquid NRTL1 equations utilizing parameters derived from the (solid + liquid) equilibrium. The partition coefficient of ionic liquid in the 1-octanol/water binary system has been calculated from the solubility results. Experimental partition coefficients (log P) were negative at three temperatures.

PMN-PT based quaternary piezoceramics with enhanced piezoelectricity and temperature stability

NASA Astrophysics Data System (ADS)

Luo, Nengneng; Zhang, Shujun; Li, Qiang; Yan, Qingfeng; He, Wenhui; Zhang, Yiling; Shrout, Thomas R.

2014-05-01

The phase structure, piezoelectric, dielectric, and ferroelectric properties of (0.80 - x)PMN-0.10PFN-0.10PZ-xPT were investigated systematically. The morphotropic phase boundary (MPB) was confirmed to be 0.30 < x < 0.34. Both MPB compositions of x = 0.32 and x = 0.33 exhibit high piezoelectric coefficients d33 = 640 pC/N and 580 pC/N, electromechanical couplings kp of 0.53 and 0.52, respectively. Of particular importance is that the composition with x = 0.33 was found to process high field-induced piezoelectric strain coefficient d33* of 680 pm/V, exhibiting a minimal temperature-dependent behavior, being less than 8% in the temperature range of 25-165 °C, which can be further confirmed by d31, with a variation of less than 9%. The temperature-insensitive d33* values can be explained by the counterbalance of the ascending dielectric permittivity and descending polarization with increasing temperature. These features make the PMN-PT based quaternary MPB compositions promising for actuator applications demanding high temperature stability.

High temperature XRD of Cu{sub 2.1}Zn{sub 0.9}SnSe{sub 4}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chetty, Raju, E-mail: rcmallik@physics.iisc.ernet.in; Mallik, Ramesh Chandra, E-mail: rcmallik@physics.iisc.ernet.in

2014-04-24

Quaternary compound with chemical composition Cu{sub 2.1}Zn{sub 0.9}SnSe{sub 4} is prepared by solid state synthesis. High temperature XRD (X-Ray Diffraction) of this compound is used in studying the effect of temperature on lattice parameters and thermal expansion coefficients. Thermal expansion coefficient is one of the important quantities in evaluating the Grüneisen parameter which further useful in determining the lattice thermal conductivity of the material. The high temperature XRD of the material revealed that the lattice parameters as well as thermal expansion coefficients of the material increased with increase in temperature which confirms the presence of anharmonicty.

Surface morphology and interdiffusion of LiF in Alq3-based organic light-emitting devices.

PubMed

Lee, Young Joo; Li, Xiaolong; Kang, Da-Yeon; Park, Seong-Sik; Kim, Jinwoo; Choi, Jeong-Woo; Kim, Hyunjung

2008-09-01

Highly efficient organic light-emitting devices (OLEDs) have been realized by insertion of a thin insulating lithium fluoride (LiF) layer between aluminum (Al) cathode and an electron transport layer, tris-(8-hydroxyquinoline) aluminum (Alq(3)). In this paper, we study the surface morphology of LiF on Alq(3) by synchrotron X-ray scattering and atomic force microscopy (AFM) as a function of thickness of LiF. We also study the interdiffusion of LiF into Al cathode as well as into Alq(3) layer as a function of temperature. Initially, LiF molecules are distributed randomly as clusters on the Alq(3) layer and then gradually form a layer as increasing LiF thickness. The interdiffusion of LiF into Al occurs more actively than into Alq(3) in annealing process. LiF on Alq(3) induces the ordering of Al to (111) direction strongly with increasing LiF thickness.

Interdiffusion behavior between NiAlHf coating and Ni-based single crystal superalloy with different crystal orientations

NASA Astrophysics Data System (ADS)

Wang, Ruili; Gong, Xueyuan; Peng, Hui; Ma, Yue; Guo, Hongbo

2015-01-01

NiAlHf coatings were deposited onto Ni-based single crystal (SC) superalloy with different crystal orientations by electron beam physical vapor deposition (EB-PVD). The effects of the crystal orientations of the superalloy substrate on inter-diffusion behavior between the substrate and the NiAlHf coating were investigated. Substrate diffusion zone (SDZ) containing needle-like μ phases and interdiffusion zone (IDZ) mainly consisting of the ellipsoidal and rod-like μ phases were formed in the SC alloy after heat-treatment 10 h at 1100 °C. The thickness of secondary reaction zone (SRZ) formed in the SC alloy with (0 1 1) crystal orientation is about 14 μm after 50 h heat-treatment at 1100 °C, which is relatively thicker than that in the SC alloy with (0 0 1) crystal orientation, whereas the IDZ revealed similar thickness.

Study of molybdenum-aluminum interdiffusion kinetics and contact resistance for VLSI applications

NASA Astrophysics Data System (ADS)

Singh, R. N.; Brown, D. M.; Kim, M. J.; Smith, G. A.

1985-12-01

Interdiffusion barrier characteristics of molybdenum thin film with aluminum-1% Si is studied between 733 and 763 K via sheet and contact resistance measurements, Rutherford backscattering spectrometry, secondary ion mass spectrometry, and x-ray diffraction analysis. The results indicate that thermal annealing of Mo/Al-1% Si thin film couples leads to MoAl12 compound formation initially as a nonplanar front, but extensive annealing results in complete transformation of Al-1% Si to MoAl12 and a significant increase in contact resistance. The interdiffusion kinetics is diffusion controlled and shows parabolic time dependence, incubation periods, and extremely high activation energy value of 5.9 eV. The incubation periods and an high activation energy values are explained by the presence of silicon precipitates at the Mo/Al-1% Si interface. Implications of these observations to VLSI device characteristics are discussed and a safe time-temperature processing regime is proposed.

Interdiffusion behavior of tungsten or rhenium and group 5 and 6 elements and alloys of the periodic table. Part 2A: Appendices A-G

NASA Technical Reports Server (NTRS)

Arcella, F. G.

1974-01-01

Arc cast W, CVD, W, CVD Re, and powder metallurgy Re materials were hot isostatically pressure welded to ten different refractory metals and alloys and thermally aged at 10 to the minus 8th power torr at 1200 C, 1500 C, 1630 C, 1800 C, and 2000 C for 100 hours to 2000 hours. Electron beam microprobe analysis was used to characterize the interdiffusion zone width of each couple system as a function of age time and temperature. Each system was least squares fitted to the equation: In (delta X sq/t) = B/T + A, where delta X is net interdiffusion zone width, t is age time, and T is age temperature. Detailed descriptions of experimental and analytical procedures utilized in conducting the experimental program are provided. For Vol. 1, see N74-34046.

Effect of interfacial disorder on exchange anisotropy in nickel manganese/nickel epitaxial bilayers

NASA Astrophysics Data System (ADS)

Lund, Michael Shane

In this thesis, the influence of interdiffusion on the structural and magnetic properties of epitaxial Ni1-xMnx/Ni bilayers has been examined. Structural characterization shows (111) oriented epitaxial layers with a 35A interdiffused layer at the Ni47Mn 53/Ni interface. This interdiffused layer is a result of the annealing step (250 C anneal for 16 hours) that is typically needed to transform NiMn into the required antiferromagnetic (AF) phase. A comparison of polarized neutron reflectometry measurements at 300 K and at 10 K show two major features as the temperature is decreased; (i) The ferromagnetic (F) moment of the sample appears to decrease with decreasing temperature, and (ii) The F layer is effectively thinner at low temperatures, i.e. the magnetic interface between the F and underlying non-F layer has a temperature dependent location. These unexpected results are confirmed by measurements of the temperature dependence of the magnetization after cooling in a demagnetized state, then applying an external field while measuring the magnetization. The magnetization decreases with decreasing temperature, consistent with a decrease in the effective F layer thickness. The effective "motion" of the magnetic interface is explained by the increasing dominance of the AF exchange interactions in the interdiffused region as the temperature is lowered. This model is further supported by the existence of memory effects and glassy behavior, which are both consistent with competing AF and F interactions in the interdiffused region. Furthermore, this interdiffusion at the AF/F interface provides a unique opportunity to assess, in a single sample, the effect of uniaxial vs. biaxial anisotropy on phenomena such as training and reversal asymmetry. As predicted by recent theory it is shown that the existence of a strong training effect, and an accompanying reversal asymmetry, can be directly correlated with the presence of biaxial exchange induced anisotropy. Finally, the dependence of exchange bias on x in Ni1-xMnx/Ni bilayers has been studied. It is found that bilayers with x ˜ 0.58 have a maximum exchange coupling and that the maximum exchange bias is achieved with just a 2 hour anneal at 250 C. This is striking and suggests that the as-deposited Ni 1-xMnx is in the AF phase. Additionally, inverted unannealed bilayers exhibit exchange bias, providing clear evidence for spontaneous magnetic ordering of Ni1-xMnx layer. This is an important find since annealing results in interdiffusion at the AF/F interface, and a subsequent reduction in the exchange bias field, it would be technologically desirable to omit this step entirely.

Ge auto-doping and out-diffusion in InGaP grown on Ge substrate and their effects on the ordering of InGaP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Hong-Ming; Ho, Hao-I; Tsai, Shi-Jane

2016-03-21

We report on the Ge auto-doping and out-diffusion in InGaP epilayer with Cu-Pt ordering grown on 4-in. Ge substrate. Ge profiles determined from secondary ion mass spectrometry indicate that the Ge out-diffusion depth is within 100 nm. However, the edge of the wafer suffers from stronger Ge gas-phase auto-doping than the center, leading to ordering deterioration in the InGaP epilayer. In the edge, we observed a residual Cu-Pt ordering layer left beneath the surface, suggesting that the ordering deterioration takes place after the deposition rather than during the deposition and In/Ga inter-diffusion enhanced by Ge vapor-phase auto-doping is responsible for themore » deterioration. We thus propose a di-vacancy diffusion model, in which the amphoteric Ge increases the di-vacancy density, resulting in a Ge density dependent diffusion. In the model, the In/Ga inter-diffusion and Ge out-diffusion are realized by the random hopping of In/Ga host atoms and Ge atoms to di-vacancies, respectively. Simulation based on this model well fits the Ge out-diffusion profiles, suggesting its validity. By comparing the Ge diffusion coefficient obtained from the fitting and the characteristic time constant of ordering deterioration estimated from the residual ordering layer, we found that the hopping rates of Ge and the host atoms are in the same order of magnitude, indicating that di-vacancies are bound in the vicinity of Ge atoms.« less

Cr diffusion in MgAl2O4 synthetic spinels: preliminary results

NASA Astrophysics Data System (ADS)

Freda, C.; Celata, B.; Andreozzi, G.; Perinelli, C.; Misiti, V.

2012-04-01

Chromian spinel is an accessory phase common in crustal and mantle rocks, including peridotites, gabbros and basalts. Spinel, it has been identified as one of the most effective, sensible, and versatile petrogenetic indicator in mafic and ultramafic rock systems due to the strict interdependence between its physico-chemical properties (chemical composition, cation configuration etc.) and genetic conditions (temperature, pressure, and chemical characteristics of the system). In particular, studies on intra- and inter-crystalline Mg-Fe2+, Cr-Al exchange demonstrated the close relationship between spinel composition and both degree of partial melting and equilibrium temperature of spinel-peridotites. Moreover, studies focused on the chemical zoning of Mg-Fe2+ and/or Cr-Al components in spinel have been used, combined with a diffusion model, to provide quantitative information on peridotites and gabbros pressure-temperature paths and on deformation mechanisms. Although these potentials, most of the experimental studies have been performed on spinels hosting a limited content of divalent iron (sensu stricto, MgAl2O4), whereas the scarce studies on Cr-Al inter-diffusion coefficient have been performed at 3-7 GPa as pressure boundary condition. In order to contribute to the understanding of processes occurring in the lithospheric mantle, we have initiated an experimental research project aiming at determining the Cr-Al inter-diffusion in spinel at 2 GPa pressure and temperature ranging from 1100 to 1250 °C. The experiments were performed in a end-loaded piston cylinder by using a 19 mm assembly and graphite-Pt double capsules. As starting materials we used synthetic Mg-Al spinel (200-300 μm in size) and Cr2O3 powder. Microanalyses of experimental charge were performed on polished carbon-coated mounts by electronic microprobe. Line elemental analyses were made perpendicular to the contact surface between Cr2O3 powder and spinel, at interval of 2 μm. By processing these preliminary data, we have estimated a diffusion coefficient of chromium (D) of 7.6·10-15 m2s-1.

Interdiffusion behavior of U3Si2 with FeCrAl via diffusion couple studies

NASA Astrophysics Data System (ADS)

Hoggan, Rita E.; He, Lingfeng; Harp, Jason M.

2018-04-01

Uranium silicide (U3Si2) is a candidate to replace uranium oxide (UO2) as light water reactor (LWR) fuel because of its higher thermal conductivity and higher fissile density relative to the current standard, UO2. A class of Fe, Cr, Al alloys collectively known as FeCrAl alloys that have superior mechanical and oxidation resistance are being considered as an alternative to the standard Zirconium based LWR cladding. The interdiffusion behavior between FeCrAl and U3Si2 is investigated in this study. Commercially available FeCrAl, along with U3Si2 pellets were placed in diffusion couples. Individual tests were ran at temperatures ranging from 500 °C to 1000 °C for 30 h and 100 h. The interdiffusion was analyzed with an optical microscope, scanning electron microscope, and transmission electron microscope. Uniform and planar interdiffusion layers along the material interface were illustrated with backscatter electron micrographs and energy-dispersive X-ray spectroscopy. Electron diffraction was used to validate phases present in the system, including distinct U2Fe3Si/UFe2 and UFeSi layers at the material interface. U and Fe diffused far into the FeCrAl and U3Si2 matrix, respectively, in the higher temperature tests. No interaction was observed at 500 °C for 30 h.

Grain boundary diffusion in olivine (Invited)

NASA Astrophysics Data System (ADS)

Marquardt, K.; Dohmen, R.

2013-12-01

Olivine is the main constituent of Earth's upper mantle. The individual mineral grains are separated by grain boundaries that have very distinct properties compared to those of single crystals and strongly affect large-scale physical and chemical properties of rocks, e.g. viscosity, electrical conductivity and diffusivity. Knowledge on the grain boundary physical and chemical properties, their population and distribution in polycrystalline materials [1] is a prerequisite to understand and model bulk (rock) properties, including their role as pathways for element transport [2] and the potential of grain boundaries as storage sites for incompatible elements [3]. Studies on selected and well characterized single grain boundaries are needed for a detailed understanding of the influence of varying grain boundaries. For instance, the dependence of diffusion on the grain boundary structure (defined by the lattice misfit) and width in silicates is unknown [2, 4], but limited experimental studies in material sciences indicate major effects of grain boundary orientation on diffusion rates. We characterized the effect of grain boundary orientation and temperature on element diffusion in forsterite grain boundaries by transmission electron microscopy (TEM).The site specific TEM-foils were cut using the focused ion beam technique (FIB). To study diffusion we prepared amorphous thin-films of Ni2SiO4 composition perpendicular to the grain boundary using pulsed laser deposition. Annealing (800-1450°C) leads to crystallization of the thin-film and Ni-Mg inter-diffuse into the crystal volume and along the grain boundary. The inter-diffusion profiles were measured using energy dispersive x-ray spectrometry in the TEM, standardized using the Cliff-Lorimer equation and EMPA measurements. We obtain volume diffusion coefficients that are comparable to Ni-Mg inter-diffusion rates in forsterite determined in previous studies at comparable temperatures, with similar activation energies. Grain boundary diffusion perpendicular to the dislocation lines of the small angle grain boundaries proved to be about an order of magnitude faster than volume diffusion, whereas diffusion in high angle grain boundaries is several orders of magnitude faster. We will discuss the variation of element diffusion rates with grain boundary orientation and the temperature- and/or time-induced transition from one diffusion regime to the next regime. This is done using time series experiments and two-dimensional grain boundary diffusion simulations. Finally, we will debate the differences between our data and other data sets that result from different experimental setups, conditions and analyses.

Quantum well intermixing of indium gallium arsenide(phosphorus)/indium phosphorus heterostructures

NASA Astrophysics Data System (ADS)

Haysom, Joan E.

This thesis studies several aspects of the interdiffusion of InGaAs(P)/InP quantum well (QW) heterostructures, from the fundamental defect mechanisms, through optimization of processing parameters, to novel device applications. Conclusions from each of these areas have been drawn which further the scientific understanding and the manufacturability of the technique. The thermal stability of a series of different wafers is studied to highlight how poor quality of growth can cause increased interdiffusion, and to review the requirements for achieving repeatable annealing. Purposeful and controlled interdiffusion is accomplished through the introduction of excess defects into layers above the QWs, which during a subsequent anneal, diffuse through the QWs and enhance interdiffusion of atoms of the QWs with atoms of the barriers. These excess defects are introduced using two different techniques, via growth at low temperatures (LT) using chemical beam epitaxy (CBE), and via implantation of phosphorus ions. The CBE LT growth technique is new, and reported for the first time in this thesis. Characterization of the as-grown layers leads us to believe that they have an excess of phosphorus. The diffusion rate of the mobile defects which cause the intermixing is also measured, and the interdiffusion is shown to occur predominantly on the group-V sublattice. Due to many similarities between this and the results of the implantation technique, it is proposed that these mobile defects are the same for both intermixing approaches, and that the behaviour can be explained by a phosphorus interstitial mechanism. Annealing recipes for the implantation-induced technique are optimized, and the sample-to-sample reproducibility of the blueshift for this method was found to be quite good (standard deviations of ˜6 meV on blueshifts of ˜70 meV). The lateral selectivity and refractive index changes are characterized, and used in combination to create novel buried waveguide devices.

Control of interface reactions in SIC/TI composites

NASA Technical Reports Server (NTRS)

Houska, C. R.; Rao, V.

1982-01-01

The reaction between a 0.5 to 1.0 Al film and a thick Ti substrate to form TiAl3 occurs very rapidly on heating to 635 C and causes the Al to be confined to the surface region. After heating to 900 C Ti3Al is formed with little release of Al into alpha Ti. Further annealing at 900 C eventually causes the Ti3Al phase to decompose and a substantial amount of Al is released into alpha Ti. The interdiffusion coefficient for Al in alpha Ti at 900 C increases by less than one order of magnitude as Al is varied from 0 to 20 at %. These data were obtained from the (101) X-ray diffraction intensity band using polycrystalline samples. Improvements in the analysis of X-ray diffraction data for the determination of composition profiles are discussed.

Interdiffusion in the Ni/TD-NiCr and Cr/TD-NiCr systems

NASA Technical Reports Server (NTRS)

Pawar, A. V.; Tenney, D. R.

1974-01-01

The diffusion of Ni and Cr into TD-NiCr has been studied over the 900 to 1100 C temperature range. The diffusion couples were prepared by electroplating Cr and Ni on polished TD-NiCr wafers. Concentration profiles produced as a result of isothermal diffusion at 905, 1000, and 1100 C were determined by electron microprobe analysis. The Boltzmann-Matano analysis was used to determine concentration-dependent diffusion coefficients which were found to compare favorably with previously reported values. These data suggest that 2 vol % ThO2 distribution has no appreciable effect on the rates of diffusion in TD-NiCr with a large grain size. This supports the view that an inert dispersoid in an alloy matrix will not in itself lead to enhanced diffusion unless a short-circuit diffusion structure is stabilized.

Cobalt Modification of Thin Rutile Films Magnetron-Sputtered in Vacuum

NASA Astrophysics Data System (ADS)

Afonin, N. N.; Logacheva, V. A.

2018-04-01

Using X-ray phase analysis, atomic force microscopy, and secondary ion mass-spectrometry, the phase formation and component distribution in a Co-TiO2 film system have been investigated during magnetron sputtering of the metal on the oxide and subsequent vacuum annealing. It has been found that cobalt diffuses deep into titanium oxide to form complex oxides CoTi2O5 and CoTiO3. A mechanism behind their formation at grain boundaries throughout the thickness of the TiO2 film is suggested. It assumes the reactive diffusion of cobalt along grain boundaries in the oxide. A quantitative model of reactive interdiffusion in a bilayer polycrystalline metal-oxide film system with limited solubility of components has been developed. The individual diffusion coefficients of cobalt and titanium have been determined in the temperature interval 923-1073 K.

Optical and electrical properties of bismuth-sulfide (Bi2S3) thin films prepared by thermal evaporation.

NASA Astrophysics Data System (ADS)

Mahmoud, Siham; Sharaf, Fouad

Thin films of Bi2S3, of thickness in the range 300 to 500 nm, were produced by thermal evaporation technique. The reaction consisted in depositing the two elements (bismuth and sulfur) from a boat source and allowing their atoms to interdiffuse to form the compound during the deposition on quartz substrates. The material has been characterized by X-ray studies, optical and electrical measurements. When these films were annealed at 353 K, 393 K and 453 K for 5 hours, a nearly amorphous to polycrystalline transition was observed. The absorption coefficient revealed the existence of an allowed direct transition with Eg = 1.56 eV. The activation energies for electrical conduction in low and high temperature regions are 0.28 eV and 0.73 eV, respectively.

Effect of plasma nitriding on the structural stability and hydrogen absorption capability of Pd-coated Nb during thermal treatment

NASA Astrophysics Data System (ADS)

Ohtsu, Naofumi; Kozuka, Taro; Shibata, Yuga; Yamane, Misao

2017-11-01

Plasma nitriding was explored for improving the thermal stability of a composite hydrogen permeable membrane comprising a Pd coating on Nb substrate. A NbN intermediate layer was formed on the Nb substrate, and the progress of interdiffusion and deterioration of hydrogen absorption behavior after a thermal treatment at 573 and 773 K, respectively, were investigated. The intermediate layer significantly suppressed the interdiffusion between the coating and the substrate. Furthermore, an increase in the NbN concentration of the intermediate layer enhanced the suppression efficiency. However, the hydrogen permeability of the intermediate layer was significantly low, and hence, an increase in NbN concentration further decreased the hydrogen permeability. We concluded that the nitride layer with a high NbN content was unsuitable as an intermediate layer owing to its low hydrogen permeability, while the partial nitride layer with a low NbN content was inefficient in suppressing the interdiffusion.

Sodium enhances indium-gallium interdiffusion in copper indium gallium diselenide photovoltaic absorbers.

PubMed

Colombara, Diego; Werner, Florian; Schwarz, Torsten; Cañero Infante, Ingrid; Fleming, Yves; Valle, Nathalie; Spindler, Conrad; Vacchieri, Erica; Rey, Germain; Guennou, Mael; Bouttemy, Muriel; Manjón, Alba Garzón; Peral Alonso, Inmaculada; Melchiorre, Michele; El Adib, Brahime; Gault, Baptiste; Raabe, Dierk; Dale, Phillip J; Siebentritt, Susanne

2018-02-26

Copper indium gallium diselenide-based technology provides the most efficient solar energy conversion among all thin-film photovoltaic devices. This is possible due to engineered gallium depth gradients and alkali extrinsic doping. Sodium is well known to impede interdiffusion of indium and gallium in polycrystalline Cu(In,Ga)Se 2 films, thus influencing the gallium depth distribution. Here, however, sodium is shown to have the opposite effect in monocrystalline gallium-free CuInSe 2 grown on GaAs substrates. Gallium in-diffusion from the substrates is enhanced when sodium is incorporated into the film, leading to Cu(In,Ga)Se 2 and Cu(In,Ga) 3 Se 5 phase formation. These results show that sodium does not decrease per se indium and gallium interdiffusion. Instead, it is suggested that sodium promotes indium and gallium intragrain diffusion, while it hinders intergrain diffusion by segregating at grain boundaries. The deeper understanding of dopant-mediated atomic diffusion mechanisms should lead to more effective chemical and electrical passivation strategies, and more efficient solar cells.

Measuring Diffusion of Liquids by Common-Path Interferometry

NASA Technical Reports Server (NTRS)

Rashidnia, Nasser

2003-01-01

A method of observing the interdiffusion of a pair of miscible liquids is based on the use of a common-path interferometer (CPI) to measure the spatially varying gradient of the index refraction in the interfacial region in which the interdiffusion takes place. Assuming that the indices of refraction of the two liquids are different and that the gradient of the index of refraction of the liquid is proportional to the gradient in the relative concentrations of either liquid, the diffusivity of the pair of liquids can be calculated from the temporal variation of the spatial variation of the index of refraction. This method yields robust measurements and does not require precise knowledge of the indices of refraction of the pure liquids. Moreover, the CPI instrumentation is compact and is optomechanically robust by virtue of its common- path design. The two liquids are placed in a transparent rectangular parallelepiped test cell. Initially, the interface between the liquids is a horizontal plane, above which lies pure liquid 2 (the less-dense liquid) and below which lies pure liquid 1 (the denser liquid). The subsequent interdiffusion of the liquids gives rise to a gradient of concentration and a corresponding gradient of the index of refraction in a mixing layer. For the purpose of observing the interdiffusion, the test cell is placed in the test section of the CPI, in which a collimated, polarized beam of light from a low-power laser is projected horizontally through a region that contains the mixing layer.

THE EFFECT OF ALKYL AMINE TYPE ON THE EXTRACTION OF NITRIC ACID AND NITROSYLRUTHENIUM NITRATO COMPLEXES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Timmins, T.H.; Mason, E.A.

1963-04-01

An investigation of the solvent extraction characteristics of nitric acid and the nitrato complexes of nitrosylruthenium was conducted, using alkyl amines as extractants. The alkyl amines used were a primary amine Primene JMT, a tertiary amine trilaurylamine (TLA), and a quaternary amine Aliquat 336. The organic phase concentrations of HNO/sub 3/ resulting during extraction by alkyl amines were found to correlate well on the basis of the undissociated aqueous HNO/ sub 3/ activity for both salted (NaNO/sub 3/) and unsalted aqueous phases. The distribution ratios for Ru extraction showed better correlation on this basis than on the basis of aqueousmore » phase nitrate and nitric acid. The order of decreasing Ru extraction at low HNO/sub 3/ concentration (2N) was found to be Aliquat 336, TLA, and Primene JMT. At high HNO/sub 3/ concentration (9N). Primene JMT had the highest Ru extractability. Hapid dilution experiments were utilized to determine the number and aqueous phase concentrations of the extractable species of Ru, and the amine partition coefficients for the species. It was found that two Ru species are extractable, and the more extractable species is present in the aqueous phase at lower concentration than the less extractable species. The mole fractions of both species were found to increase with increasing HNO/sub 3/ concentration. The TLA partition coefficients for the extractable species were found to decrease with increasing HNO/sub 3/ concentration. The quaternary amine, Aliquat 336, was found to have partition coefficients an order of magnitude greater than the tertiary amine, TLA. Equations for the mole fractions and TLA partition coefficients in the region of HNO/sub 3/ concentration investigated were developed. (auth)« less

Experimental characterization and modelization of ion exchange kinetics for a carboxylic resin in infinite solution volume conditions. Application to monovalent-trivalent cations exchange.

PubMed

Picart, Sébastien; Ramière, Isabelle; Mokhtari, Hamid; Jobelin, Isabelle

2010-09-02

This study is devoted to the characterization of ion exchange inside a microsphere of carboxylic resin. It aims at describing the kinetics of this exchange reaction which is known to be controlled by interdiffusion in the particle. The fractional attainment of equilibrium function of time depends on the concentration of the cations in the resin which can be modelized by the Nernst-Planck equation. A powerful approach for the numerical resolution of this equation is introduced in this paper. This modeling is based on the work of Helfferich but involves an implicit numerical scheme which reduces the computational cost. Knowing the diffusion coefficients of the cations in the resin and the radius of the spherical exchanger, the kinetics can be hence completely determined. When those diffusion parameters are missing, they can be deduced by fitting experimental data of fractional attainment of equilibrium. An efficient optimization tool coupled with the implicit resolution has been developed for this purpose. A monovalent/trivalent cation exchange had been experimentally characterized for a carboxylic resin. Diffusion coefficients and concentration profiles in the resin were then deduced through this new model.

Substitutional and Interstitial Diffusion in alpha2-Ti3Al(O)

NASA Technical Reports Server (NTRS)

Copland, Evan; Young, David J.; Gleeson, Brian; Jacobson, Nathan

2007-01-01

The reaction between Al2O3 and alpha2-Ti3Al was studied with a series of Al2O3/alpha2-Ti3Al multiphase diffusion couples annealed at 900, 1000 and 1100 C. The diffusion-paths were found to strongly depend on alpha2- Ti3Al(O) composition. For alloys with low oxygen concentrations the reaction involved the reduction of Al2O3, the formation of a gamma-TiAl reaction-layer and diffusion of Al and O into the alpha2-Ti3Al substrate. Measured concentration profiles across the interaction-zone showed "up-hill" diffusion of O in alpha2-Ti3Al(O) indicating a significant thermodynamic interaction between O and Al, Ti or both. Diffusion coefficients for the interstitial O in alpha2-Ti3Al(O) were determined independently from the interdiffusion of Ti and Al on the substitutional lattice. Diffusion coefficients are reported for alpha2-Ti3Al(O) as well as gamma-TiAl. Interpretation of the results were aided with the subsequent measurement of the activities of Al, Ti and O in alpha 2-Ti3Al(O) by Knudsen effusion-cell mass spectrometry.

Impact ionisation in Al0.9Ga0.1As0.08Sb0.92 for Sb-based avalanche photodiodes

NASA Astrophysics Data System (ADS)

Collins, X.; Craig, A. P.; Roblin, T.; Marshall, A. R. J.

2018-01-01

We report the impact ionisation coefficients of the quaternary alloy Al0.9Ga0.1As0.08Sb0.92 lattice matched to GaSb substrates within the field range of 150 to 550 kV cm-1 using p-i-n and n-i-p diodes of various intrinsic thicknesses. The coefficients were found with an evolutionary fitting algorithm using a non-local recurrence based multiplication model and a variable electric field profile. These coefficients indicate that an avalanche photodiode not only can be designed to be a function in the mid-wave infrared but also can be operated at lower voltages. This is due to the high magnitude of the impact ionisation coefficients at relatively low fields compared to other III-V materials typically used in avalanche multiplication regions.

Scaling behavior of nonisothermal phase separation.

PubMed

Rüllmann, Max; Alig, Ingo

2004-04-22

The phase separation process in a critical mixture of polydimethylsiloxane and polyethylmethylsiloxane (PDMS/PEMS, a system with an upper critical solution temperature) was investigated by time-resolved light scattering during continuous quenches from the one-phase into the two-phase region. Continuous quenches were realized by cooling ramps with different cooling rates kappa. Phase separation kinetics is studied by means of the temporal evolution of the scattering vector qm and the intensity Im at the scattering peak. The curves qm(t) for different cooling rates can be shifted onto a single mastercurve. The curves Im(t) show similar behavior. As shift factors, a characteristic length Lc and a characteristic time tc are introduced. Both characteristic quantities depend on the cooling rate through power laws: Lc approximately kappa(-delta) and tc approximately kappa(-rho). Scaling behavior in isothermal critical demixing is well known. There the temporal evolutions of qm and Im for different quench depths DeltaT can be scaled with the correlation length xi and the interdiffusion coefficient D, both depending on DeltaT through critical power laws. We show in this paper that the cooling rate scaling in nonisothermal demixing is a consequence of the quench depth scaling in the isothermal case. The exponents delta and rho are related to the critical exponents nu and nu* of xi and D, respectively. The structure growth during nonisothermal demixing can be described with a semiempirical model based on the hydrodynamic coarsening mechanism well known in the isothermal case. In very late stages of nonisothermal phase separation a secondary scattering maximum appears. This is due to secondary demixing. We explain the onset of secondary demixing by a competition between interdiffusion and coarsening. (c) 2004 American Institute of Physics

Interface modification based ultrashort laser microwelding between SiC and fused silica.

PubMed

Zhang, Guodong; Bai, Jing; Zhao, Wei; Zhou, Kaiming; Cheng, Guanghua

2017-02-06

It is a big challenge to weld two materials with large differences in coefficients of thermal expansion and melting points. Here we report that the welding between fused silica (softening point, 1720°C) and SiC wafer (melting point, 3100°C) is achieved with a near infrared femtosecond laser at 800 nm. Elements are observed to have a spatial distribution gradient within the cross section of welding line, revealing that mixing and inter-diffusion of substances have occurred during laser irradiation. This is attributed to the femtosecond laser induced local phase transition and volume expansion. Through optimizing the welding parameters, pulse energy and interval of the welding lines, a shear joining strength as high as 15.1 MPa is achieved. In addition, the influence mechanism of the laser ablation on welding quality of the sample without pre-optical contact is carefully studied by measuring the laser induced interface modification.

Experimental study of copper-alkali ion exchange in glass

NASA Astrophysics Data System (ADS)

Gonella, F.; Caccavale, F.; Bogomolova, L. D.; D'Acapito, F.; Quaranta, A.

1998-02-01

Copper-alkali ion exchange was performed by immersing different silicate glasses (soda-lime and BK7) in different molten eutectic salt baths (CuSO4:Na2SO4 and CuSO4:K2SO4). The obtained optical waveguides were characterized by m-lines spectroscopy for the determination of refractive index profiles, and by secondary ion mass spectrometry for the concentration profiles of the ion species involved in the exchange process. The different oxidation states of copper inside the glass structure were studied by electron paramagnetic resonance and x-ray absorption techniques. Interdiffusion copper coefficients were also determined. The Cu-alkali exchange was observed to give rise to local structural rearrangement of the atoms in the glass matrix. The Cu+ ion was found to mainly govern the exchange process, while competition between Cu-Na and K-Na exchanges occurred when a potassium sulfate bath was used. In this case, significant waveguide modal birefringence was observed.

Enhanced Thermoelectric Properties of Cu 2ZnSnSe 4 with Ga-doping

DOE PAGES

Wei, Kaya; Beauchemin, Laura; Wang, Hsin; ...

2015-08-10

Gallium doped Cu 2ZnSnSe 4 quaternary chalcogenides with and without excess Cu were synthesized by elemental reaction and densified using hot pressing in order to investigate their high temperature thermoelectric properties. The resistivity, , and Seebeck coefficient, S, for these materials decrease with increased Ga-doping while both mobility and effective mass increase with Ga doping. The power factor (S 2/ρ) therefore increases with Ga-doping. The highest thermoelectric figure of merit (ZT = 0.39 at 700 K) was obtained for the composition that had the lowest thermal conductivity. Our results suggest an approach to achieving optimized thermoelectric properties and are partmore » of the continuing effort to explore different quaternary chalcogenide compositions and structure types, as this class of materials continues to be of interest for thermoelectrics applications.« less

Determination of the quaternary phase diagram of the water-ethylene glycol-sucrose-NaCl system and a comparison between two theoretical methods for synthetic phase diagrams

PubMed Central

Han, Xu; Liu, Yang; Critser, John K.

2010-01-01

Characterization of the thermodynamic properties of multi-solute aqueous solutions is of critical importance for biological and biochemical research. For example, the phase diagrams of aqueous systems, containing salts, saccharides, and plasma membrane permeating solutes, are indispensible in the field of cryobiology and pharmacology. However, only a few ternary phase diagrams are currently available for these systems. In this study, an auto-sampler differential scanning calorimeter (DSC) was used to determine the quaternary phase diagram of the water-ethylene glycol-sucrose-NaCl system. To improve the accuracy of melting point measurement, a “mass redemption” method was also applied for the DSC technique. Base on the analyses of these experimental data, a comparison was made between the two practical approaches to generate phase diagrams of multi-solute solutions from those of single-solute solutions: the summation of cubic polynomial melting point equations versus the use of osmotic virial equations with cross coefficients. The calculated values of the model standard deviations suggested that both methods are satisfactory for characterizing this quaternary system. PMID:20447385

Role of Si on the Diffusional Interactions Between U-Mo and Al-Si Alloys at 823 K (550 °C)

NASA Astrophysics Data System (ADS)

Perez, Emmanuel; Sohn, Yong-Ho; Keiser, Dennis D.

2013-01-01

U-Mo dispersions in Al-alloy matrix and monolithic fuels encased in Al-alloy are under development to fulfill the requirements for research and test reactors to use low-enriched molybdenum stabilized uranium alloy fuels. Significant interaction takes place between the U-Mo fuel and Al during manufacturing and in-reactor irradiation. The interaction products are Al-rich phases with physical and thermal characteristics that adversely affect fuel performance and result in premature failure. Detailed analysis of the interdiffusion and microstructural development of this system was carried through diffusion couples consisting of U-7 wt pct Mo, U-10 wt pct Mo and U-12 wt pct Mo in contact with pure Al, Al-2 wt pct Si, and Al-5 wt pct Si, annealed at 823 K (550 °C) for 1, 5 and 20 hours. Scanning electron microscopy and transmission electron microscopy were employed for the analysis. Diffusion couples consisting of U-Mo in contact with pure Al contained UAl3, UAl4, U6Mo4Al43, and UMo2Al20 phases. Additions of Si to the Al significantly reduced the thickness of the interdiffusion zone. The interdiffusion zones developed Al- and Si-enriched regions, whose locations and size depended on the Si and Mo concentrations in the terminal alloys. In these couples, the (U,Mo)(Al,Si)3 phase was observed throughout the interdiffusion zone, and the U6Mo4Al43 and UMo2Al20 phases were observed only where the Si concentrations were low.

Evaluation of the efficiency of continuous wavelet transform as processing and preprocessing algorithm for resolution of overlapped signals in univariate and multivariate regression analyses; an application to ternary and quaternary mixtures

NASA Astrophysics Data System (ADS)

Hegazy, Maha A.; Lotfy, Hayam M.; Mowaka, Shereen; Mohamed, Ekram Hany

2016-07-01

Wavelets have been adapted for a vast number of signal-processing applications due to the amount of information that can be extracted from a signal. In this work, a comparative study on the efficiency of continuous wavelet transform (CWT) as a signal processing tool in univariate regression and a pre-processing tool in multivariate analysis using partial least square (CWT-PLS) was conducted. These were applied to complex spectral signals of ternary and quaternary mixtures. CWT-PLS method succeeded in the simultaneous determination of a quaternary mixture of drotaverine (DRO), caffeine (CAF), paracetamol (PAR) and p-aminophenol (PAP, the major impurity of paracetamol). While, the univariate CWT failed to simultaneously determine the quaternary mixture components and was able to determine only PAR and PAP, the ternary mixtures of DRO, CAF, and PAR and CAF, PAR, and PAP. During the calculations of CWT, different wavelet families were tested. The univariate CWT method was validated according to the ICH guidelines. While for the development of the CWT-PLS model a calibration set was prepared by means of an orthogonal experimental design and their absorption spectra were recorded and processed by CWT. The CWT-PLS model was constructed by regression between the wavelet coefficients and concentration matrices and validation was performed by both cross validation and external validation sets. Both methods were successfully applied for determination of the studied drugs in pharmaceutical formulations.

Polymer Disentanglement during 3D Printing

NASA Astrophysics Data System (ADS)

McIlroy, Claire; Olmsted, Peter D.

Although 3D printing has the potential to transform manufacturing processes, improving the strength of printed parts to rival that of traditionally-manufactured parts remains an underlying issue. The most common method, fused filament fabrication (FFF), involves melting a thermoplastic, followed by layer-by-layer filament extrusion to fabricate a 3D object. The key to ensuring strength at the weld between layers is successful inter-diffusion and re-entanglement of the melt across the interface. Under typical printing conditions the melt experiences high strain rates within the nozzle, which can significantly stretch and orient the polymers. Consequently, inter-diffusion does not occur from an equilibrium state. The printed layer also cools towards the glass transition, which limits inter-diffusion time. We employ a continuum polymer model (Rolie-Poly) that incorporates flow-induced changes in the entanglement density to predict how an amorphous polymer melt is deformed during FFF. The deformation is dominated by the deposition process, which involves a 90 degree turn and transformation from circular to elliptical geometry. Polymers become highly stretched and aligned with the flow direction, which significantly disentangles the melt via convective constraint release.

Magnetic moments, coupling, and interface interdiffusion in Fe/V(001) superlattices

NASA Astrophysics Data System (ADS)

Schwickert, M. M.; Coehoorn, R.; Tomaz, M. A.; Mayo, E.; Lederman, D.; O'brien, W. L.; Lin, Tao; Harp, G. R.

1998-06-01

Epitaxial Fe/V(001) multilayers are studied both experimentally and by theoretical calculations. Sputter-deposited epitaxial films are characterized by x-ray diffraction, magneto-optical Kerr effect, and x-ray magnetic circular dichroism. These results are compared with first-principles calculations modeling different amounts of interface interdiffusion. The exchange coupling across the V layers is observed to oscillate, with antiferromagnetic peaks near the V layer thicknesses tV~22, 32, and 42 Å. For all films including superlattices and alloys, the average V magnetic moment is antiparallel to that of Fe. The average V moment increases slightly with increasing interdiffusion at the Fe/V interface. Calculations modeling mixed interface layers and measurements indicate that all V atoms are aligned with one another for tV<~15 Å, although the magnitude of the V moment decays toward the center of the layer. This ``transient ferromagnetic'' state arises from direct (d-d) exchange coupling between V atoms in the layer. It is argued that the transient ferromagnetism suppresses the first antiferromagnetic coupling peak between Fe layers, expected to occur at tV~12 Å.

Thermal expansion of quaternary nitride coatings

NASA Astrophysics Data System (ADS)

Tasnádi, Ferenc; Wang, Fei; Odén, Magnus; Abrikosov, Igor A.

2018-04-01

The thermal expansion coefficient of technologically relevant multicomponent cubic nitride alloys are predicted using the Debye model with ab initio elastic constants calculated at 0 K and an isotropic approximation for the Grüneisen parameter. Our method is benchmarked against measured thermal expansion of TiN and Ti(1-x)Al x N as well as against results of molecular dynamics simulations. We show that the thermal expansion coefficients of Ti(1-x-y)X y Al x N (X  =  Zr, Hf, Nb, V, Ta) solid solutions monotonously increase with the amount of alloying element X at all temperatures except for Zr and Hf, for which they instead decrease for y≳ 0.5 .

Evaluation of the efficiency of continuous wavelet transform as processing and preprocessing algorithm for resolution of overlapped signals in univariate and multivariate regression analyses; an application to ternary and quaternary mixtures.

PubMed

Hegazy, Maha A; Lotfy, Hayam M; Mowaka, Shereen; Mohamed, Ekram Hany

2016-07-05

Wavelets have been adapted for a vast number of signal-processing applications due to the amount of information that can be extracted from a signal. In this work, a comparative study on the efficiency of continuous wavelet transform (CWT) as a signal processing tool in univariate regression and a pre-processing tool in multivariate analysis using partial least square (CWT-PLS) was conducted. These were applied to complex spectral signals of ternary and quaternary mixtures. CWT-PLS method succeeded in the simultaneous determination of a quaternary mixture of drotaverine (DRO), caffeine (CAF), paracetamol (PAR) and p-aminophenol (PAP, the major impurity of paracetamol). While, the univariate CWT failed to simultaneously determine the quaternary mixture components and was able to determine only PAR and PAP, the ternary mixtures of DRO, CAF, and PAR and CAF, PAR, and PAP. During the calculations of CWT, different wavelet families were tested. The univariate CWT method was validated according to the ICH guidelines. While for the development of the CWT-PLS model a calibration set was prepared by means of an orthogonal experimental design and their absorption spectra were recorded and processed by CWT. The CWT-PLS model was constructed by regression between the wavelet coefficients and concentration matrices and validation was performed by both cross validation and external validation sets. Both methods were successfully applied for determination of the studied drugs in pharmaceutical formulations. Copyright © 2016 Elsevier B.V. All rights reserved.

The effect of the averaged structural and energetic features on the cohesive energy of nanocrystals

NASA Astrophysics Data System (ADS)

Ali Safaei

2010-03-01

The size dependency of the cohesive energy of nanocrystals is obtained in terms of their averaged structural and energetic properties, which are in direct proportion with their cohesive energies. The significance of the effect of the geometrical shape of nanoparticles on their thermal stability has been discussed. The model has been found to have good prediction for the case of Cu and Al nanoparticles, with sizes in the ranges of 1-22 nm and 2-22 nm, respectively. Defining a new parameter, named as the surface-to-volume energy-contribution ratio, the relative thermal stabilities of different nanoclusters and their different surface-crystalline faces are discussed and compared to the molecular dynamic (MD) simulation results of copper nanoclusters. Finally, based on the size dependency of the cohesive energy, a formula for the size-dependent diffusion coefficient has been presented which includes the structural and energetic effects. Using this formula, the faster-than-expected interdiffusion/alloying of Au(core)-Ag(shell) nanoparticles with the core-shell structure, the Au-core diameter of 20 nm and the Ag-shell thickness of 2.91 nm, has been discussed and the calculated diffusion coefficient has been found to be consistent with its corresponding experimental value.

A study of interdiffusion in beta + gamma/gamma + gamma prime Ni-Cr-Al. M.S. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Carol, L. A.

1985-01-01

Ternary diffusion in the NiCrAl system at 1200 C was studied with beta + gamma/gamma + gamma prime infinite diffusion couples. Interdiffusion resulted in the formation of complex, multiphase diffusion zones. Concentration/distance profiles for Cr and Al in the phases present in the diffusion zone were measured after 200 hr. The Ni-rich portion of the NiCrAl phase diagram (1200 C) was also determined. From these data, bulk Cr and Al profiles were calculated and translated to diffusion paths on the ternary isotherm. Growth layer kinetics of the layers present in the diffusion zone were also measured.

Radiation effects on interface reactions of U/Fe, U/(Fe+Cr), and U/(Fe+Cr+Ni)

DOE PAGES

Shao, Lin; Chen, Di; Wei, Chaochen; ...

2014-10-01

We study the effects of radiation damage on interdiffusion and intermetallic phase formation at the interfaces of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni) diffusion couples. Magnetron sputtering is used to deposit thin films of Fe, Fe + Cr, or Fe + Cr + Ni on U substrates to form the diffusion couples. One set of samples are thermally annealed under high vacuum at 450 C or 550 C for one hour. A second set of samples are annealed identically but with concurrent 3.5 MeV Fe++ ion irradiation. The Fe++ ion penetration depth is sufficient to reachmore » the original interfaces. Rutherford backscattering spectrometry analysis with high fidelity spectral simulations is used to obtain interdiffusion profiles, which are used to examine differences in U diffusion and intermetallic phase formation at the buried interfaces. For all three diffusion systems, Fe++ ion irradiations enhance U diffusion. Furthermore, the irradiations accelerate the formation of intermetallic phases. In U/Fe couples, for example, the unirradiated samples show typical interdiffusion governed by Fick’s laws, while the irradiated ones show step-like profiles influenced by Gibbs phase rules.« less

A modelling study of the inter-diffusion layer formation in U-Mo/Al dispersion fuel plates at high power

NASA Astrophysics Data System (ADS)

Ye, B.; Hofman, G. L.; Leenaers, A.; Bergeron, A.; Kuzminov, V.; Van den Berghe, S.; Kim, Y. S.; Wallin, H.

2018-02-01

Post irradiation examinations of full-size U-Mo/Al dispersion fuel plates fabricated with ZrN- or Si- coated U-Mo particles revealed that the reaction rate of irradiation-induced U-Mo-Al inter-diffusion, an important microstructural change impacting the performance of this type of fuel, transited at a threshold temperature/fission rate. The existing inter-diffusion layer (IL) growth correlation, which does not describe the transition behavior of IL growth, was modified by applying a temperature-dependent multiplication factor that transits around a threshold fission rate. In-pile irradiation data from four tests in the BR2 reactors, including FUTURE, E-FUTURE, SELEMIUM, and SELEMIUM-1a, were utilized to determine and validate the updated IL growth correlation. Irradiation behavior of the plates was simulated with the DART-2D computational code. The general agreement between the calculated and measured fuel meat swelling and constituent volume fractions as a function of fission density demonstrated the plausibility of the updated IL growth correlation. The simulation results also suggested the temperature dependence of the IL growth rate, similar to the temperature dependence of the inter-mixing rate in ion-irradiated bi-layer systems.

New Pb(Mg1/3Nb2/3)O3-Pb(In1/2Nb1/2)O3-PbZrO3-PbTiO3 Quaternary Ceramics: Morphotropic Phase Boundary Design and Electrical Properties.

PubMed

Luo, Nengneng; Zhang, Shujun; Li, Qiang; Xu, Chao; Yang, Zhanlue; Yan, Qingfeng; Zhang, Yiling; Shrout, Thomas R

2016-06-22

Four series of Pb(Mg1/3Nb2/3)O3-Pb(In1/2Nb1/2)O3-PbZrO3-PbTiO3 (PMN-PIN-PZ-PT) quaternary ceramics with compositions located at the morphotropic phase boundary (MPB) regions were prepared. The MPBs of the multicomponent system were predicted using a linear combination rule and experimentally confirmed by X-ray powder diffraction and electrical measurement. The positions of MPBs in multicomponent systems were found in linear correlation with the tolerance factor and ionic radii of non-PT end-members. The phase structure, piezoelectric coefficient, electromechanical coupling coefficient, unipolar strains, and dielectric properties of as-prepared ceramics were systematically investigated. The largest d33s were obtained at S36.8, L37.4, M39.6, and N35.8, with the corresponding values of 580, 450, 420, and 530 pC/N, respectively, while the largest kps were found at S34.8, L37.4, M39.6, and N35.8, with the respective values of 0.54, 0.50, 0.47, and 0.53. The largest unipolar strain Smax and high-field piezoelectric strain coefficients d33* were also observed around the respective MPB regions. The rhombohedral-to-tetragonal phase transition temperature Trt increased with increasing PIN and PZ contents. Of particular importance is that high Trt of 140-197 °C was achieved in the M series with PZ and PIN contents being around 0.208 and 0.158, which will broaden the temperature usage range.

Effects of Sn Layer Orientation on the Evolution of Cu/Sn Interfaces

NASA Astrophysics Data System (ADS)

Sun, Menglong; Zhao, Zhangjian; Hu, Fengtian; Hu, Anmin; Li, Ming; Ling, Huiqin; Hang, Tao

2018-03-01

The effects of Sn layer orientation on the evolution of Cu/Sn joint interfaces were investigated. Three Sn layers possessing (112), (321) and (420) orientations were electroplated on polycrystalline Cu substrates respectively. The orientations of Sn layer preserved during reflowing at 250 °C for 10 s. After aging at 150 °C for different time, the interfacial microstructures were observed from the cross-section and top-view. The alignment between the c-axis of Sn and Cu diffusion direction significantly sped up the Cu diffusion, leading to the thickest intermetallic compound layer formed in (112) joint. Two types of voids, namely, intracrystalline voids and grain islanding caused intercrystalline voids generated at Cu/Cu3Sn interfaces due to the different interdiffusion coefficients of Cu and Sn (112) oriented Sn/Cu joint produced many more voids than (321) joint, and no voids were detected in (420) joint. Therefore, to enhance the reliability of solder joints, using (420) oriented Sn as solder layer could be an efficient way.

Generalized Cahn-Hilliard equation for solutions with drastically different diffusion coefficients. Application to exsolution in ternary feldspar

NASA Astrophysics Data System (ADS)

Petrishcheva, E.; Abart, R.

2012-04-01

We address mathematical modeling and computer simulations of phase decomposition in a multicomponent system. As opposed to binary alloys with one common diffusion parameter, our main concern is phase decomposition in real geological systems under influence of strongly different interdiffusion coefficients, as it is frequently encountered in mineral solid solutions with coupled diffusion on different sub-lattices. Our goal is to explain deviations from equilibrium element partitioning which are often observed in nature, e.g., in a cooled ternary feldspar. To this end we first adopt the standard Cahn-Hilliard model to the multicomponent diffusion problem and account for arbitrary diffusion coefficients. This is done by using Onsager's approach such that flux of each component results from the combined action of chemical potentials of all components. In a second step the generalized Cahn-Hilliard equation is solved numerically using finite-elements approach. We introduce and investigate several decomposition scenarios that may produce systematic deviations from the equilibrium element partitioning. Both ideal solutions and ternary feldspar are considered. Typically, the slowest component is initially "frozen" and the decomposition effectively takes place only for two "fast" components. At this stage the deviations from the equilibrium element partitioning are indeed observed. These deviations may became "frozen" under conditions of cooling. The final equilibration of the system occurs on a considerably slower time scale. Therefore the system may indeed remain unaccomplished at the observation point. Our approach reveals the intrinsic reasons for the specific phase separation path and rigorously describes it by direct numerical solution of the generalized Cahn-Hilliard equation.

A modelling study of the inter-diffusion layer formation in U-Mo/Al dispersion fuel plates at high power

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, B.; Hofman, G. L.; Leenaers, A.

Post irradiation examinations of full-size U-Mo/Al dispersion fuel plates fabricated with ZrN- or Sicoated U-Mo particles revealed that the reaction rate of irradiation-induced U-Mo-Al inter-diffusion, an important microstructural change impacting the performance of this type of fuel, is temperature and fission-rate dependent. In order to simulate the U-Mo/Al inter-diffusion layer (IL) growth behavior in full-size dispersion fuel plates, the existing IL growth correlation was modified with a temperaturedependent multiplication factor that transits around a threshold fission rate. In-pile irradiation data from four tests in the BR2 reactors, including FUTURE, E-FUTURE, SELEMIUM, and SELEMIUM-1a, were utilized to determine and validate themore » updated IL growth correlation. Irradiation behavior of the plates was simulated with the DART-2D computational code. The general agreement between the calculated and measured fuel meat swelling and constituent volume fractions as a function of fission density demonstrated the plausibility of the updated IL growth correlation. The simulation results also suggested the temperature dependence of the IL growth rate, similar to the temperature dependence of the intermixing rate in ion-irradiated bi-layer systems.« less

Interfacial sharpness and intermixing in a Ge-SiGe multiple quantum well structure

NASA Astrophysics Data System (ADS)

Bashir, A.; Gallacher, K.; Millar, R. W.; Paul, D. J.; Ballabio, A.; Frigerio, J.; Isella, G.; Kriegner, D.; Ortolani, M.; Barthel, J.; MacLaren, I.

2018-01-01

A Ge-SiGe multiple quantum well structure created by low energy plasma enhanced chemical vapour deposition, with nominal well thickness of 5.4 nm separated by 3.6 nm SiGe spacers, is analysed quantitatively using scanning transmission electron microscopy. Both high angle annular dark field imaging and electron energy loss spectroscopy show that the interfaces are not completely sharp, suggesting that there is some intermixing of Si and Ge at each interface. Two methods are compared for the quantification of the spectroscopy datasets: a self-consistent approach that calculates binary substitutional trends without requiring experimental or computational k-factors from elsewhere and a standards-based cross sectional calculation. Whilst the cross section approach is shown to be ultimately more reliable, the self-consistent approach provides surprisingly good results. It is found that the Ge quantum wells are actually about 95% Ge and that the spacers, whilst apparently peaking at about 35% Si, contain significant interdiffused Ge at each side. This result is shown to be not just an artefact of electron beam spreading in the sample, but mostly arising from a real chemical interdiffusion resulting from the growth. Similar results are found by use of X-ray diffraction from a similar area of the sample. Putting the results together suggests a real interdiffusion with a standard deviation of about 0.87 nm, or put another way—a true width defined from 10%-90% of the compositional gradient of about 2.9 nm. This suggests an intrinsic limit on how sharp such interfaces can be grown by this method and, whilst 95% Ge quantum wells (QWs) still behave well enough to have good properties, any attempt to grow thinner QWs would require modifications to the growth procedure to reduce this interdiffusion, in order to maintain a composition of ≥95% Ge.

Temperature and pressure dependent structural and thermo-physical properties of quaternary CoVTiAl alloy

NASA Astrophysics Data System (ADS)

Yousuf, Saleem; Gupta, Dinesh C.

2017-09-01

Investigation of band structure and thermo-physical response of new quaternary CoVTiAl Heusler alloy within the frame work of density functional theory has been analyzed. 100% spin polarization with ferromagnetic stable ground state at the optimized lattice parameter of 6.01 Å is predicted for the compound. Slater-Pauling rule for the total magnetic moment of 3 μB and an indirect semiconducting behavior is also seen for the compound. In order to perfectly analyze the thermo-physical response, the lattice thermal conductivity and thermodynamic properties have been calculated. Thermal effects on some macroscopic properties of CoVTiAl are predicted using the quasi-harmonic Debye model, in which the lattice vibrations are taken into account. The variations of the lattice constant, volume expansion coefficient, heat capacities, and Debye temperature with pressure and temperature in the ranges of 0 GPa to 15 GPa and 0 K to 800 K have been obtained.

Coherent assembly of heterostructures in ternary and quaternary carbonitrides

NASA Astrophysics Data System (ADS)

Caicedo, J. C.; Aperador, W.; Saldarriaga, W.

2018-05-01

In this study, ternary and quaternary carbonitride heterostructure systems were grown on silicon (100) substrates in order to investigate coherent assembly in TiCN/TiNbCN. The heterostructure films were grown using the reactive r. f. magnetron sputtering technique by systematically varying the bilayer period (Λ) and the bilayer number (n), while maintaining a constant total coating thickness (∼3 μm). The heterostructures were characterized by high angle X-ray diffraction (HA-XRD) and low angle X-ray diffraction, while the TiCN and TiNbCN layers were analyzed by X-ray photoelectron spectroscopy and transmission electron microscopy. The HA-XRD results indicated preferential growth in the face-centered cubic (111) crystal structure for the [TiCN/TiNbCN]n heterostructures. The maximum coherent assembly was observed with the presence of satellite peaks. Thus, ternary and quaternary carbonitride films were designed and deposited on Si (100) substrates with bilayer periods (Λ) in a broad range from nanometers to hundreds of nanometers in order to study the structural evolution and coherent assembly progress as the bilayer thickness decreased. We determined physical properties comprising the critical angle (θc) (0.362°), electronic density (ρe) (0.521 × 1033 el/m3), dispersion coefficient (δ) (0.554 el/m3), and refractive index (n) (0.999944) as functions of the number of bilayers (n).

The electronic and optical properties of quaternary GaAs1-x-y N x Bi y alloy lattice-matched to GaAs: a first-principles study.

PubMed

Ma, Xiaoyang; Li, Dechun; Zhao, Shengzhi; Li, Guiqiu; Yang, Kejian

2014-01-01

First-principles calculations based on density functional theory have been performed for the quaternary GaAs1-x-y N x Bi y alloy lattice-matched to GaAs. Using the state-of-the-art computational method with the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional, electronic, and optical properties were obtained, including band structures, density of states (DOSs), dielectric function, absorption coefficient, refractive index, energy loss function, and reflectivity. It is found that the lattice constant of GaAs1-x-y N x Bi y alloy with y/x =1.718 can match to GaAs. With the incorporation of N and Bi into GaAs, the band gap of GaAs1-x-y N x Bi y becomes small and remains direct. The calculated optical properties indicate that GaAs1-x-y N x Bi y has higher optical efficiency as it has less energy loss than GaAs. In addition, it is also found that the electronic and optical properties of GaAs1-x-y N x Bi y alloy can be further controlled by tuning the N and Bi compositions in this alloy. These results suggest promising applications of GaAs1-x-y N x Bi y quaternary alloys in optoelectronic devices.

Thermodynamic properties and solidification kinetics of intermetallic Ni{sub 7}Zr{sub 2} alloy investigated by electrostatic levitation technique and theoretical calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, L. H.; Hu, L.; Yang, S. J.

2016-01-21

The thermodynamic properties, including the density, volume expansion coefficient, ratio of specific heat to emissivity of intermetallic Ni{sub 7}Zr{sub 2} alloy, have been measured using the non-contact electrostatic levitation technique. These properties vary linearly with temperature at solid and liquid states, even down to the obtained maximum undercooling of 317 K. The enthalpy, glass transition, diffusion coefficient, shear viscosity, and surface tension were obtained by using molecular dynamics simulations. Ni{sub 7}Zr{sub 2} has a relatively poor glass forming ability, and the glass transition temperature is determined as 1026 K. The inter-diffusivity of Ni{sub 7}Zr{sub 2} alloy fitted by Vogel–Fulcher–Tammann law yields amore » fragility parameter of 8.49, which indicates the fragile nature of this alloy. Due to the competition of increased thermodynamic driving force and decreased atomic diffusion, the dendrite growth velocity of Ni{sub 7}Zr{sub 2} compound exhibits double-exponential relationship to the undercooling. The maximum growth velocity is predicted to be 0.45 m s{sup −1} at the undercooling of 335 K. Theoretical analysis reveals that the dendrite growth is a diffusion-controlled process and the atomic diffusion speed is only 2.0 m s{sup −1}.« less

The effect of silicon on the oxidation behavior of NiAlHf coating system

NASA Astrophysics Data System (ADS)

Dai, Pengchao; Wu, Qiong; Ma, Yue; Li, Shusuo; Gong, Shengkai

2013-04-01

Two types of NiAlHf coatings doped with different content of Si (1 at.% and 2 at.%) were deposited on a Ni3Al based single crystal superalloy IC32 by electron beam physical vapor deposition (EB-PVD) method, respectively. For comparison, NiAlHf coating with 0 at.% Si was also prepared. The oxidation tests were carried out at 1423 K in air. At the initial stage of oxidation, large amount of flake-like θ-Al2O3 was found on NiAlHf coating surface. However, no θ-Al2O3 was observed in 2 at.% Si doped NiAlHf coating except α-Al2O3. It revealed that the Si additions could contribute to the transformation from θ-Al2O3 to α-Al2O3. When oxidation time prolonged to 100 h, it was found that the degradation of NiAlHf coating was very severe with no residual β-phase, which was due to the serious inter-diffusion between the coating and substrate. In contrast, the inter-diffusion in Si-doped coating was reduced with some residual β-phase and R-Ni(Mo, Re) precipitates. The presence of Si could retard the inter-diffusion of elements between coating and substrate, indicating a barrier diffusion effect. As a result, the oxidation resistance of NiAlHf coating was improved significantly.

Interdiffusion effect on strained La0.8Ba0.2MnO3 thin films by off-axis sputtering on SrTiO3 (100) substrates

NASA Astrophysics Data System (ADS)

Chou, Hsiung; Hsu, S. G.; Lin, C. B.; Wu, C. B.

2007-02-01

Strained La0.8Ba0.2MnO3 thin films on SrTiO3 (100) substrate are grown by an off-axis sputtering technique. It is found that the ferromagnetic temperature TC increases for thinner films. Secondary ion mass spectroscopy indicates that Sr diffuses partially into the film, making it structurally nonuniform. The region close to the film/substrate interface acts as La1-x(SryBa1-y)xMnO3 with a near negligible y for the as grown film and a non-negligible amount of y for the high-temperature postannealed film. The enhancement of TC is attributed to the combination of the strain and interdiffusion effects.

Study of surfactant mediated growth of Ni/V superlattices

NASA Astrophysics Data System (ADS)

Amir, S. M.; Gupta, Mukul; Potdar, Satish; Gupta, Ajay; Stahn, Jochen

2013-07-01

The Ni/V multilayers are useful as soft x-ray mirrors, polarizers, and phase retarders. For these applications, it is necessary that the interfaces roughness and interdiffusion must be as small as possible. The V-on-Ni and Ni-on-V interfaces are asymmetric due to the difference in the surface free energy of Ni and V. In this work, we report Ag surfactant mediated growth of Ni/V superlattices prepared using ion beam sputter deposition technique. These superlattices were studied using x-ray and neutron scattering techniques. It was found that when added in an optimum amount, Ag surfactant results in reduced interface roughness and interdiffusion across the interfaces. Obtained results can be understood with the surfactant floating-off mechanism leading to a balance in the surface free energy of Ni and V.

Low-temperature lithium diffusion in simulated high-level boroaluminosilicate nuclear waste glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neeway, James J.; Kerisit, Sebastien N.; Gin, Stephane

2014-12-01

Ion exchange is recognized as an integral, if underrepresented, mechanism influencing glass corrosion. However, due to the formation of various alteration layers in the presence of water, it is difficult to conclusively deconvolute the mechanisms of ion exchange from other processes occurring simultaneously during corrosion. In this work, an operationally inert non-aqueous solution was used as an alkali source material to isolate ion exchange and study the solid-state diffusion of lithium. Specifically, the experiments involved contacting glass coupons relevant to the immobilization of high-level nuclear waste, SON68 and CJ-6, which contained Li in natural isotope abundance, with a non-aqueous solutionmore » of 6LiCl dissolved in dimethyl sulfoxide at 90 °C for various time periods. The depth profiles of major elements in the glass coupons were measured using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Lithium interdiffusion coefficients, D Li, were then calculated based on the measured depth profiles. The results indicate that the penetration of 6Li is rapid in both glasses with the simplified CJ-6 glass (D 6Li ≈ 4.0-8.0 × 10 -21 m 2/s) exhibiting faster exchange than the more complex SON68 glass (D Li ≈ 2.0-4.0 × 10 -21 m 2/s). Additionally, sodium ions present in the glass were observed to participate in ion exchange reactions; however, different diffusion coefficients were necessary to fit the diffusion profiles of the two alkali ions. Implications of the diffusion coefficients obtained in the absence of alteration layers to the long-term performance of nuclear waste glasses in a geological repository system are also discussed.« less

Novel Quaternary Quantum Decoder, Multiplexer and Demultiplexer Circuits

NASA Astrophysics Data System (ADS)

Haghparast, Majid; Monfared, Asma Taheri

2017-05-01

Multiple valued logic is a promising approach to reduce the width of the reversible or quantum circuits, moreover, quaternary logic is considered as being a good choice for future quantum computing technology hence it is very suitable for the encoded realization of binary logic functions through its grouping of 2-bits together into quaternary values. The Quaternary decoder, multiplexer, and demultiplexer are essential units of quaternary digital systems. In this paper, we have initially designed a quantum realization of the quaternary decoder circuit using quaternary 1-qudit gates and quaternary Muthukrishnan-Stroud gates. Then we have presented quantum realization of quaternary multiplexer and demultiplexer circuits using the constructed quaternary decoder circuit and quaternary controlled Feynman gates. The suggested circuits in this paper have a lower quantum cost and hardware complexity than the existing designs that are currently used in quaternary digital systems. All the scales applied in this paper are based on Nanometric area.

Effect of ten quaternary ammonium cations on tetrachloromethane sorption to clay from water

USGS Publications Warehouse

Smith, J.A.

1990-01-01

The mineral surface of Wyoming bentonite (clay) was modified by replacing inorganic ions by each of 10 quaternary ammonium compounds, and tetrachloromethane sorption to the modified sorbents from water was studied. Tetrachloromethane sorption from solution to clay modified with tetramethyl-, tetraethyl-, benzyltrimethyl-, or benzyltriethylammonium cations generally is characterized by relatively high solute uptake, isotherm nonlinearity, and competitive sorption (with trichloroethene as the competing sorbate). For these sorbents, the ethyl functional groups yield reduced sorptive capacity relative to methyl groups, whereas the benzyl group appears to have a similar effect on sorbent capacity as the methyl group. Sorption of tetrachloromethane to clay modified with dodecyldimethyl(2-phenoxyethyl)-, dodecyltrimethyl-, tetradecyltrimethyl-, hexadecyltrimethyl-, or benzyldimethylhexadecylammonium bromide is characterized by relatively low solute uptake, isotherm linearity, and noncompetitive sorption. For these sorbents, an increase in the size of the nonpolar functional group(s) causes an increase in the organic carbon normalized sorption coefficient (Koc). No measurable uptake of tetrachloromethane sorption by the unmodified clay or clay modified by ammonium bromide was observed. ?? 1990 American Chemical Society.

Solid-state diffusion-controlled growth of the phases in the Au-Sn system

NASA Astrophysics Data System (ADS)

Baheti, Varun A.; Kashyap, Sanjay; Kumar, Praveen; Chattopadhyay, Kamanio; Paul, Aloke

2018-01-01

The solid state diffusion-controlled growth of the phases is studied for the Au-Sn system in the range of room temperature to 200 °C using bulk and electroplated diffusion couples. The number of product phases in the interdiffusion zone decreases with the decrease in annealing temperature. These phases grow with significantly high rates even at the room temperature. The growth rate of the AuSn4 phase is observed to be higher in the case of electroplated diffusion couple because of the relatively small grains and hence high contribution of the grain boundary diffusion when compared to the bulk diffusion couple. The diffraction pattern analysis indicates the same equilibrium crystal structure of the phases in these two types of diffusion couples. The analysis in the AuSn4 phase relating the estimated tracer diffusion coefficients with grain size, crystal structure, the homologous temperature of experiments and the concept of the sublattice diffusion mechanism in the intermetallic compounds indicate that Au diffuses mainly via the grain boundaries, whereas Sn diffuses via both the grain boundaries and the lattice.

Effect of V2O5 on SrO-ZnO-B2O3-SiO2 glass-ceramics for high temperature sealant application

NASA Astrophysics Data System (ADS)

Tiwari, Babita; Bhatacharya, S.; Dixit, A.; Gadkari, S. C.; Kothiyal, G. P.

2012-06-01

Glasses in the SrO-ZnO-B2O3-SiO2 (SZBS) system with and without V2O5 were prepared by melt-quench method and transformed into glass-ceramics by controlled crystallization. Investigated glasses and glass-ceramics have thermal expansion coefficients (TEC) in the range of 95-120 × 10-7/°C (30-600 °C), which match closely with TEC of other components of solid oxide fuel cell (SOFC). Study of thermo-physical properties of SZBS glasses revealed the network modifying effect of V2O5. Addition of V2O5 increases the TEC and decreases the viscosity of the glass which is beneficial for making seal with Crofer-22-APU. Microstructural investigations have shown good bonding of SZBS glasses with Crofer-22-APU. Elemental line scans indicate that inter-diffusion of Fe, Cr and Si across interface, which is thought to be responsible for good bonding with Crofer-22-APU.

Diffusion phenomenon at the interface of Cu-brass under a strong gravitational field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ogata, Yudai; Tokuda, Makoto; Januszko, Kamila

2015-03-28

To investigate diffusion phenomenon at the interface between Cu and brass under a strong gravitational field generated by ultracentrifuge apparatus, we performed gravity experiments on samples prepared by electroplating with interfaces normal and parallel to the direction of gravity. For the parallel-mode sample, for which sedimentation cannot occur thorough the interface, the concentration change was significant within the lower gravity region; many pores were observed in this region. Many vacancies arising from crystal strain due to the strong gravitational field moved into the lower gravity region, and enhanced the atoms mobilities. For the two normal-mode samples, which have interface normalmore » to the direction of gravity, the composition gradient of the brass-on-Cu sample was steeper than that for Cu-on-brass. This showed that the atoms of denser Cu diffuse in the direction of gravity, whereas Zn atoms diffuse in the opposite direction by sedimentation. The interdiffusion coefficients became higher in the Cu-on-brass sample, and became lower in the brass-on-Cu sample. This rise may be related to the behavior of the vacancies.« less

Joining Dental Ceramic Layers With Glass

PubMed Central

Saied, MA; Lloyd, IK; Haller, WK; Lawn, BR

2011-01-01

Objective Test the hypothesis that glass-bonding of free-form veneer and core ceramic layers can produce robust interfaces, chemically durable and aesthetic in appearance and, above all, resistant to delamination. Methods Layers of independently produced porcelains (NobelRondo™ Press porcelain, Nobel BioCare AB and Sagkura Interaction porcelain, Elephant Dental) and matching alumina or zirconia core ceramics (Procera alumina, Nobel BioCare AB, BioZyram yttria stabilized tetragonal zirconia polycrystal, Cyrtina Dental) were joined with designed glasses, tailored to match thermal expansion coefficients of the components and free of toxic elements. Scanning electron microprobe analysis was used to characterize the chemistry of the joined interfaces, specifically to confirm interdiffusion of ions. Vickers indentations were used to drive controlled corner cracks into the glass interlayers to evaluate the toughness of the interfaces. Results The glass-bonded interfaces were found to have robust integrity relative to interfaces fused without glass, or those fused with a resin-based adhesive. Significance The structural integrity of the interfaces between porcelain veneers and alumina or zirconia cores is a critical factor in the longevity of all-ceramic dental crowns and fixed dental prostheses. PMID:21802131

Interconnect mechanisms in microelectronic packaging

NASA Astrophysics Data System (ADS)

Roma, Maria Penafrancia C.

Global economic, environmental and market developments caused major impact in the microelectronics industry. Astronomical rise of gold metal prices over the last decade shifted the use of copper and silver alloys as bonding wires. Environmental legislation on the restriction of the use of Pb launched worldwide search for lead-free solders and platings. Finally, electrical and digital uses demanded smaller, faster and cheaper devices. Ultra-fine pitch bonding, decreasing bond wire sizes and hard to bond substrates have put the once-robust stitch bond in the center of reliability issues due to stitch bond lift or open wires .Unlike the ball bond, stitch bonding does not lead to intermetallic compound formation but adhesion is dependent on mechanical deformation, interdiffusion, solid solution formation, void formation and mechanical interlocking depending on the wire material, bond configuration, substrate type , thickness and surface condition. Using Au standoff stitch bonds on NiPdAu plated substrates eliminated stitch bond lift even when the Au and Pd layers are reduced. Using the Matano-Boltzmann analysis on a STEM (Scanning Transmission Analysis) concentration profile the interdiffusion coefficient is measured to be 10-16 cm 2/s. Wire pull strength data showed that the wire pull strength is 0.062N and increases upon stress testing. Meanwhile, coating the Cu wire with Pd, not only increases oxidation resistance but also improved adhesion due to the formation of a unique interfacial adhesion layers. Adhesion strength as measured by pull showed the Cu wire bonded to Ag plated Cu substrate (0.132N) to be stronger than the Au wire bonded on the same substrate (0.124N). Ag stitch bonded to Au is predicted to be strong but surface modification made the adhesion stronger. However, on the Ag ball bonded to Al showed multiple IMC formation with unique morphology exposed by ion milling and backscattered scanning electron microscopy. Adding alloying elements in the Ag wire alloy showed differences in adhesion strength and IMC formation. Bond strength by wire pull testing showed the 95Ag alloy with higher values while shear bond testing showed the 88Ag higher bond strength. Use of Cu pillars in flip chips and eutectic bonding in wafer level chip scale packages are direct consequences of diminishing interconnect dimension as a result of the drive for miniaturization. The combination of Cu-Sn interdiffusion, Kirkendall mechanism and heterogeneous vacancy precipitation are the main causes of IMC and void formation in Cu pillar - Sn solder - Cu lead frame sandwich structure. However, adding a Ni barrier agent showed less porous IMC layer as well as void formation as a result of the modified Cu and Sn movement well as the void formation. Direct die to die bonding using Al-Ge eutectic bonds is necessary when 3D integration is needed to reduce the footprint of a package. Hermeticity and adhesion strength are a function of the Al/Ge thickness ratio, bonding pressure, temperature and time. Scanning Electron Microscope (SEM) and Focused Ion Beam (FIB) allowed imaging of interfacial microstructures, porosity, grain morphology while Scanning Transmission Electron microscope (STEM) provided diffusion profile and confirmed interdiffusion. Ion polishing technique provided information on porosity and when imaged using backscattered mode, grain structure confirmed mechanical deformation of the bonds. Measurements of the interfacial bond strength are made by wire pull tests and ball shear tests based on existing industry standard tests. However, for the Al-Ge eutectic bonds, no standard strength is available so a test is developed using the stud pull test method using the Dage 4000 Plus to yield consistent results. Adhesion strengths of 30-40 MPa are found for eutectic bonded packages however, as low as 20MPa was measured in low temperature bonded areas.

Limited-life cartridge primers

DOEpatents

Makowiecki, Daniel M.; Rosen, Robert S.

1998-01-01

A cartridge primer which utilizes an explosive that can be designed to become inactive in a predetermined period of time: a limited-life primer. The explosive or combustible material of the primer is an inorganic reactive multilayer (RML). The reaction products of the RML are sub-micron grains of non-corrosive inorganic compounds that would have no harmful effects on firearms or cartridge cases. Unlike use of primers containing lead components, primers utilizing RML's would not present a hazard to the environment. The sensitivity of an RML is determined by the physical structure and the stored interfacial energy. The sensitivity lowers with time due to a decrease in interfacial energy resulting from interdiffusion of the elemental layers. Time-dependent interdiffusion is predictable, thereby enabling the functional lifetime of an RML primer to be predetermined by the initial thickness and materials selection of the reacting layers.

Limited-life cartridge primers

DOEpatents

Makowiecki, Daniel M.; Rosen, Robert S.

2005-04-19

A cartridge primer which utilizes an explosive that can be designed to become inactive in a predetermined period of time: a limited-life primer. The explosive or combustible material of the primer is an inorganic reactive multilayer (RML). The reaction products of the RML are sub-micron grains of non-corrosive inorganic compounds that would have no harmful effects on firearms or cartridge cases. Unlike use of primers containing lead components, primers utilizing RML's would not present a hazard to the environment. The sensitivity of an RML is determined by the physical structure and the stored interfacial energy. The sensitivity lowers with time due to a decrease in interfacial energy resulting from interdiffusion of the elemental layers. Time-dependent interdiffusion is predictable, thereby enabling the functional lifetime of an RML primer to be predetermined by the initial thickness and materials selection of the reacting layers.

Transport properties of ultra-thin VO2 films on (001) TiO2 grown by reactive molecular-beam epitaxy

NASA Astrophysics Data System (ADS)

Paik, Hanjong; Moyer, Jarrett A.; Spila, Timothy; Tashman, Joshua W.; Mundy, Julia A.; Freeman, Eugene; Shukla, Nikhil; Lapano, Jason M.; Engel-Herbert, Roman; Zander, Willi; Schubert, Jürgen; Muller, David A.; Datta, Suman; Schiffer, Peter; Schlom, Darrell G.

2015-10-01

We report the growth of (001)-oriented VO2 films as thin as 1.5 nm with abrupt and reproducible metal-insulator transitions (MIT) without a capping layer. Limitations to the growth of thinner films with sharp MITs are discussed, including the Volmer-Weber type growth mode due to the high energy of the (001) VO2 surface. Another key limitation is interdiffusion with the (001) TiO2 substrate, which we quantify using low angle annular dark field scanning transmission electron microscopy in conjunction with electron energy loss spectroscopy. We find that controlling island coalescence on the (001) surface and minimization of cation interdiffusion by using a low growth temperature followed by a brief anneal at higher temperature are crucial for realizing ultrathin VO2 films with abrupt MIT behavior.

Effect of La2O3 addition on interface chemistry between 4YSZ top layer and Ni based alloy bond coat in thermal barrier coating by EB PVD.

PubMed

Park, Chan-Young; Yang, Young-Hwan; Kim, Seong-Won; Lee, Sung-Min; Kim, Hyung-Tae; Jang, Byung-Koog; Lim, Dae-Soon; Oh, Yoon-Suk

2014-11-01

The effect of a 5 mol% La2O3 addition on the forming behavior and compositional variation at interface between a 4 mol% Yttria (Y2O3) stabilized ZrO2 (4YSZ) top coat and bond coat (NiCrAlY) as a thermal barrier coating (TBC) has been investigated. Top coats were deposited by electron beam physical vapor deposition (EB PVD) onto a super alloy (Ni-Cr-Co-Al) substrate without pre-oxidation of the bond coat. Top coats are found to consist of dense columnar grains with a thin interdiffusion layer between metallic bond coats. In the as-received 4YSZ coating, a thin interdiffusion zone at the interface between the top and bond coats was found to consist of a Ni-Zr intermetallic compound with a reduced quantity of Y, Al or O elements. On the other hand, in the case of an interdiffusion area of 5 mol% La2O3-added 4YSZ coating, it was found that the complicated composition and structure with La-added YSZ and Ni-Al rich compounds separately. The thermal conductivity of 5 mol% La2O3-added 4YSZ coating (- 1.6 W/m x k at 1100 degrees C) was lower than a 4YSZ coating (- 3.2 W/m x k at 1100 degrees C) alone.

Formation of silicides in annealed periodic multilayers

NASA Astrophysics Data System (ADS)

Maury, H.; Jonnard, P.; Le Guen, K.; André, J.-M.

2009-05-01

Periodic multilayers of nanometric period are widely used as optical components for the X-ray and extreme UV (EUV) ranges, in X-ray space telescopes, X-ray microscopes, EUV photolithography or synchrotron beamlines for example. Their optical performances depend on the quality of the interfaces between the various layers: chemical interdiffusion or mechanical roughness shifts the application wavelength and can drastically decrease the reflectance. Since under high thermal charge interdiffusion is known to get enhanced, the study of the thermal stability of such structures is essential to understand how interfacial compounds develop. We have characterized X-ray and EUV siliconcontaining multilayers (Mo/Si, Sc/Si and Mg/SiC) as a function of the annealing temperature (up to 600°C) using two non-destructive methods. X-ray emission from the silicon atoms, describing the Si valence states, is used to determine the chemical nature of the compounds present in the interphases while X-ray reflectivity in the hard and soft X-ray ranges can be related to the optical properties. In the three cases, interfacial metallic (Mo, Sc, Mg) silicides are evidenced and the thickness of the interphase increases with the annealing temperature. For Mo/Si and Sc/Si multilayers, silicides are even present in the as-prepared multilayers. Characteristic parameters of the stacks are determined: composition of the interphases, thickness and roughness of the layers and interphases if any. Finally, we have evidenced the maximum temperature of application of these multilayers to minimize interdiffusion.

On the interdiffusion in multilayered silicide coatings for the vanadium-based alloy V-4Cr-4Ti

NASA Astrophysics Data System (ADS)

Chaia, N.; Portebois, L.; Mathieu, S.; David, N.; Vilasi, M.

2017-02-01

To provide protection against corrosion at high temperatures, silicide diffusion coatings were developed for the V-4Cr-4Ti alloy, which can be used as the fuel cladding in next-generation sodium-cooled fast breeder reactors. The multilayered coatings were prepared by halide-activated pack cementation using MgF2 as the transport agent and pure silicon (high activity) as the master alloy. Coated pure vanadium and coated V-4Cr-4Ti alloy were studied and compared as substrates. In both cases, the growth of the silicide layers (V3Si, V5Si3, V6Si5 and VSi2) was controlled exclusively by solid-state diffusion, and the growth kinetics followed a parabolic law. Wagner's analysis was adopted to calculate the integrated diffusion coefficients for all silicides. The estimated values of the integrated diffusion coefficients range from approximately 10-9 to 10-13 cm2 s-1. Then, a diffusion-based numerical approach was used to evaluate the growth and consumption of the layers when the coated substrates were exposed at critical temperatures. The estimated lifetimes of the upper VSi2 layer were 400 h and 280 h for pure vanadium and the V-4Cr-4Ti alloy, respectively. The result from the numeric simulation was in good agreement with the layer thicknesses measured after aging the coated samples at 1150 °C under vacuum.

Effect of on-site Coulomb interaction on electronic and transport properties of 100% spin polarized CoMnVAs

NASA Astrophysics Data System (ADS)

Bhat, Tahir Mohiuddin; Gupta, Dinesh C.

2017-08-01

The structural, electronic, magnetic and transport properties of a new quaternary Heusler alloy CoMnVAs have been investigated by employing generalized gradient approximation (GGA), modified Becke-Johnson (mBJ) and GGA with Hubbard U correction (GGA + U). The alloy is energetically more stable in ferromagnetic Y1 type structure. Elastic parameters reveal high anisotropy and ductile nature of the material. CoMnVAs shows half-metallic ferromagnet character with 100% spin polarization at Fermi level with band gap of 0.55 eV in the minority spin state. The alloy also possesses high electrical conductivity and Seebeck coefficients with 15 μVK-1 at room temperature, achieving a figure of merit of 0.65 at high temperatures. The high degree of ductility, 100% spin polarization and large Seebeck coefficient, makes it an attractive candidate to be used in spin voltage generators and thermoelectric materials.

Multicomponent homogeneous alloys and method for making same

DOEpatents

Dutta, Partha S.; Miller, Thomas R.

2003-09-02

The present application discloses a method for preparing a homogeneous ternary or quaternary alloy from a quaternary melt. The method includes providing a family of phase diagrams for the quaternary melt which shows (i) composition/temperature data, (ii) tie lines connecting equilibrium liquid and solid compositions, and (iii) isotherms representing boundaries of a miscibility gap. Based on the family of phase diagrams, a quaternary melt composition and an alloy growth temperature is selected. A quaternary melt having the selected quaternary melt composition is provided and a ternary or quaternary alloy is grown from the quaternary melt at the selected alloy growth temperature. A method for making homogeneous ternary or quaternary alloy from a ternary or quaternary melt is also disclosed, as are homogeneous quaternary single-crystal alloys which are substantially free from crystal defects and which have the formula A.sub.x B.sub.1-x C.sub.y D.sub.1-y, x and y being the same or different and in the range of 0.001 to 0.999.

Novel Optical Fiber Materials With Engineered Brillouin Gain Coefficients SSL 1: Novel Fiber Lasers

DTIC Science & Technology

2015-12-29

strontium aluminosilicate glasses . A zero-p12 composition is calculated to be at a SiO2 content of about 41.5 mol%, SrO content of about 22.5 mol...ternary, glasses that are needed for this program. These include the BaO- SiO2 system as an example binary glass , and the MgO-Al2O3- SiO2 and BaO-Al2O3... SiO2 systems as example ternary glasses (with the addition of a rare earth 16 resulting in a quaternary glass ). Complex ternary compositions were

Comparative analyses of quaternary arrangements in homo-oligomeric proteins in superfamilies: Functional implications.

PubMed

Sudha, Govindarajan; Srinivasan, Narayanaswamy

2016-09-01

A comprehensive analysis of the quaternary features of distantly related homo-oligomeric proteins is the focus of the current study. This study has been performed at the levels of quaternary state, symmetry, and quaternary structure. Quaternary state and quaternary structure refers to the number of subunits and spatial arrangements of subunits, respectively. Using a large dataset of available 3D structures of biologically relevant assemblies, we show that only 53% of the distantly related homo-oligomeric proteins have the same quaternary state. Considering these homologous homo-oligomers with the same quaternary state, conservation of quaternary structures is observed only in 38% of the pairs. In 36% of the pairs of distantly related homo-oligomers with different quaternary states the larger assembly in a pair shows high structural similarity with the entire quaternary structure of the related protein with lower quaternary state and it is referred as "Russian doll effect." The differences in quaternary state and structure have been suggested to contribute to the functional diversity. Detailed investigations show that even though the gross functions of many distantly related homo-oligomers are the same, finer level differences in molecular functions are manifested by differences in quaternary states and structures. Comparison of structures of biological assemblies in distantly and closely related homo-oligomeric proteins throughout the study differentiates the effects of sequence divergence on the quaternary structures and function. Knowledge inferred from this study can provide insights for improved protein structure classification and function prediction of homo-oligomers. Proteins 2016; 84:1190-1202. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Effect of oxygen-to-metal flux ratio on incorporation of metal species into quaternary BeMgZnO grown by plasma-assisted molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Toporkov, M.; Ullah, M. B.; Demchenko, D. O.; Avrutin, V.; Morkoç, H.; Özgür, Ü.

2017-06-01

Owing to its large bandgap covering the UV region of the optical spectrum, the quaternary BeMgZnO is of interest, particularly the collective effect Be and Mg fluxes on the solid composition. Incorporation of Be, Mg, and Zn in the wurtzite BeMgZnO quaternary alloy was found to depend strongly on the reactive-oxygen to metal flux ratio during growth by plasma-assisted molecular beam epitaxy under metal-rich conditions. For a given set of metal fluxes, reducing the VI/II (oxygen to metal flux) ratio from 1.0 to 0.6 increased the bandgap from 4.0 eV to 4.5 eV and decreased the c lattice parameter from 5.08 Å to 5.02 Å. The corresponding change in composition from Be0.07Mg0.21Zn0.72O to Be0.10Mg0.34Zn0.56O was consistent with a systematic reduction in the Zn incorporation coefficient from 0.23 to 0.12, while those of Be and Mg remained at ∼1. This behavior was explained by the substantially lower formation enthalpies of wurtzite BeO and MgO, -5.98 eV and -5.64 eV, respectively, compared to that of ZnO, -3.26 eV, determined using first principles calculations, as well as the high equilibrium vapor pressure of Zn, which results in re-evaporation of excessive Zn from the growing surface, details of which are the topic of this manuscript.

Quaternary ammonium-functionalized silica sorbents for the solid-phase extraction of aromatic amines under normal phase conditions.

PubMed

Vidal, Lorena; Robin, Orlane; Parshintsev, Jevgeni; Mikkola, Jyri-Pekka; Riekkola, Marja-Liisa

2013-04-12

Quaternary ammonium-functionalized silica materials were synthesized and applied for solid-phase extraction (SPE) of aromatic amines, which are classified as priority pollutants by US Environmental Protection Agency. Hexamethylenetetramine used for silica surface modification for the first time was employed as SPE sorbent under normal phase conditions. Hexaminium-functionalized silica demonstrated excellent extraction efficiencies for o-toluidine, 4-ethylaniline and quinoline (recoveries 101-107%), while for N,N-dimethylaniline and N-isopropylaniline recoveries were from low to moderate (14-46%). In addition, the suitability of 1-alkyl-3-(propyl-3-sulfonate) imidazolium-functionalized silica as SPE sorbent was tested under normal phase conditions. The recoveries achieved for the five aromatic amines ranged from 89 to 99%. The stability of the sorbent was evaluated during and after 150 extractions. Coefficients of variation between 4.5 and 10.2% proved a high stability of the synthesized sorbent. Elution was carried out using acetonitrile in the case of hexaminium-functionalized silica and water for 1-alkyl-3-(propyl-3-sulfonate) imidazolium-functionalized silica sorbent. After the extraction the analytes were separated and detected by liquid chromatography ultraviolet detection (LC-UV). The retention mechanism of the materials was primarily based on polar hydrogen bonding and π-π interactions. Comparison made with activated silica proved the quaternary ammonium-functionalized materials to offer different selectivity and better extraction efficiencies for aromatic amines. Finally, 1-alkyl-3-(propyl-3-sulfonate) imidazolium-functionalized silica sorbent was successfully tested for the extraction of wastewater and soil samples. Copyright © 2013 Elsevier B.V. All rights reserved.

METAL SHEATHED BODIES

DOEpatents

Finniston, H.M.; Wyatt, L.M.; Plail, O.S.

1961-06-27

An aluminum-cased uranium fuel element is patented for use in nuclear reactors. A layer of a substance such as graphite or a metallic film, preferably of relatively low thermal-neutron capture cross section, between the uranium and aluminum prevents their interdiffusion.

Limited-life cartridge primers

DOEpatents

Makowiecki, D.M.; Rosen, R.S.

1998-06-30

A cartridge primer is described which utilizes an explosive that can be designed to become inactive in a predetermined period of time: a limited-life primer. The explosive or combustible material of the primer is an inorganic reactive multilayer (RML). The reaction products of the RML are sub-micron grains of non-corrosive inorganic compounds that would have no harmful effects on firearms or cartridge cases. Unlike use of primers containing lead components, primers utilizing RML`s would not present a hazard to the environment. The sensitivity of an RML is determined by the physical structure and the stored interfacial energy. The sensitivity lowers with time due to a decrease in interfacial energy resulting from interdiffusion of the elemental layers. Time-dependent interdiffusion is predictable, thereby enabling the functional lifetime of an RML primer to be predetermined by the initial thickness and materials selection of the reacting layers. 10 figs.

Oxygen influencing the photocarriers lifetime of CH3NH3PbI3-xClx film grown by two-step interdiffusion method and its photovoltaic performance

NASA Astrophysics Data System (ADS)

Yuan, Shuai; Qiu, Zhiwen; Zhang, Hailiang; Gong, Haibo; Hao, Yufeng; Cao, Bingqiang

2016-01-01

During the growth of CH3NH3PbI3-xClx (MAPbI3-xClx) perovskite films by the two-step inter-diffusion method, the presence of a trace amount of oxygen gas is critical to their physical properties and photovoltaic performance. As the oxygen concentration increases, poor film morphologies and incomplete surface coverage are observed. Moreover, by XRD, Raman scattering, and photoluminescence measurements, we find that MAPbI3-xClx grains become more distorted and the electron-hole recombination rate dramatically increases. Higher oxygen concentration triggers a sharp decrease in the current density and the fill factor of corresponding solar cells, which degrades device performance, on average, from 14.3% to 4.4%. This work proves the importance of controlling the oxygen atmosphere in the fabrication of high-performance perovskite solar cells.

Strain dynamics during La{sub 2}O{sub 3}/Lu{sub 2}O{sub 3} superlattice and alloy formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Proessdorf, André; Niehle, Michael; Grosse, Frank

The dynamics of strain relaxation and intermixing during molecular beam epitaxy of La{sub 2}O{sub 3} and Lu{sub 2}O{sub 3} superlattices and alloys consisting of both binaries on Si(111) have been studied by real-time in situ grazing incidence x-ray diffraction and high resolution transmission electron microscopy. The presence of both hexagonal and cubic polymorphs of La{sub 2}O{sub 3} influences the epitaxial formation within the superlattice. The process of strain relaxation is closely related to the presence of a (La,Lu){sub 2}O{sub 3} alloy adopting a cubic symmetry. It is formed by interdiffusion of La and Lu atoms reducing internal lattice mismatch withinmore » the superlattice. An interface thickness dominated by interdiffusion regions of about 3 monolayers is determined by high-angle annular dark field scanning transmission electron microscopy.« less

Transport properties of ultra-thin VO{sub 2} films on (001) TiO{sub 2} grown by reactive molecular-beam epitaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paik, Hanjong; Tashman, Joshua W.; Moyer, Jarrett A.

2015-10-19

We report the growth of (001)-oriented VO{sub 2} films as thin as 1.5 nm with abrupt and reproducible metal-insulator transitions (MIT) without a capping layer. Limitations to the growth of thinner films with sharp MITs are discussed, including the Volmer-Weber type growth mode due to the high energy of the (001) VO{sub 2} surface. Another key limitation is interdiffusion with the (001) TiO{sub 2} substrate, which we quantify using low angle annular dark field scanning transmission electron microscopy in conjunction with electron energy loss spectroscopy. We find that controlling island coalescence on the (001) surface and minimization of cation interdiffusion bymore » using a low growth temperature followed by a brief anneal at higher temperature are crucial for realizing ultrathin VO{sub 2} films with abrupt MIT behavior.« less

Interdiffusion and reactions between U-Mo and Zr at 650 °C as a function of time

NASA Astrophysics Data System (ADS)

Park, Y.; Keiser, D. D.; Sohn, Y. H.

2015-01-01

Development of monolithic U-Mo alloy fuel (typically U-10 wt.%Mo) for the Reduced Enrichment for Research and Test Reactors (RERTR) program entails a use of Zr diffusion barrier to eliminate the interdiffusion-reactions between the fuel alloy and Al-alloy cladding. The application of Zr barrier to the U-Mo fuel system requires a co-rolling process that utilizes a soaking temperature of 650 °C, which represents the highest temperature the fuel system is exposed to during both fuel manufacturing and reactor application. Therefore, in this study, development of phase constituents, microstructure and diffusion kinetics of U-10 wt.%Mo and Zr was examined using solid-to-solid diffusion couples annealed at 650 °C for 240, 480 and 720 h. Phase constituents and microstructural development were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Concentration profiles were mapped as diffusion paths on the isothermal ternary phase diagram. Within the diffusion zone, single-phase layers of β-Zr and β-U were observed along with a discontinuous layer of Mo2Zr between the β-Zr and β-U layers. In the vicinity of Mo2Zr phase, islands of α-Zr phases were also found. In addition, acicular α-Zr and U6Zr3Mo phases were observed within the γ-U(Mo) terminal alloy. Growth rate of the interdiffusion-reaction zone was determined to be 7.75 (± 5.84) × 10-16 m2/s at 650 °C, however with an assumption of a certain incubation period.

Electrochemically influenced cation inter-diffusion and Co 3O 4 formation on La 0.6Sr 0.4CoO 3 infiltrated into SOFC cathodes

DOE PAGES

Song, Xueyan; Lee, Shiwoo; Chen, Yun; ...

2015-06-18

Nanosized LSC electrocatalyst was infiltrated into a porous scaffold cathode composed of Sm 2O 3-doped CeO 2 (SDC) and La 0.6Sr 0.4Co 0.2Fe 0.8O 3-δ (LSCF) in a commercial button solid oxide fuel cell (SOFC). To understand the stability of cathodes infiltrated with LSC, the infiltrated composite cells were subjected to both electrochemical operating and thermal aging states at 750 °C for 1500 h. Nanostructure and local chemistry evolution of La 0.6Sr 0.4CoO 3 (LSC) infiltrated cathodes upon operation and aging were investigated by transmission electron microscopy. After operation, the LSC remained a cubic perovskite, and the crystal grains exhibitmore » comparable size to as-infiltrated LSC grains. Inter-diffusion of Fe from the LSCF to a Fe-incorporated LSC layer developed on the LSCF backbone. However, only sharp interfaces were observed between LSC and SDC backbone in the as-infiltrated cathode and such interfaces remain after operation. The infiltrated LSC on the SDC backbone also retains granular particle morphology. Furthermore, newly grown Co 3O 4 nanocrystals were found in the operated cathode. After thermal aging, on the other hand, cation inter-diffusion across the interfaces of the infiltrate particles and the cathode backbones is less than that from the operated cells. Lastly, the following hypothesis is proposed: Co 3O 4 forms on LSC arising from local charge balancing between cobalt and oxygen vacancies.« less

Permeability and electrical properties of planar lipid membranes from thylakoid lipids.

PubMed Central

Fuks, B; Homblé, F

1994-01-01

Electrical measurements were carried out on planar lipid membranes from thylakoid lipids. The specific capacitance of membranes formed from decane-containing monogalactosyldiacylglycerol (MGDG), which accounts for 57% of the total lipid content of thylakoids, showed that it adopted a bilayer structure. Solvent-free bilayers of MGDG were not formed, with very rare exceptions, indicating that decane is required to stabilize the planar conformation. However, this cone-shaped lipid produces bilayer structures in combination with other cylindrical thylakoid lipids even in the absence of organic solvent. We compared the properties of solvent-free and decane-containing bilayers from MGDG, soybean lecithin, and the quaternary mixture of lipids similar to that found in vivo. The conductance of decane-MGDG was 26 times higher than that of decane-lecithin. The flux through the decane-lecithin bilayer was found to be slightly dependent on pH, whereas the decane-MGDG membrane was not. The specific conductance of bilayers formed from the quaternary mixture of lipids was 5 to 10 times larger than lecithin (with alkane or not). Further experiments with bilayers made in the presence of a KCl gradient showed that decane-MGDG, decane-MGDG/DGDG/SQDG/PG, and solvent-free MGDG/DGDG/SQDG/PG were cation-selective. The permeability coefficient for potassium ranged from 4.9 to 8.3 x 10(-11) cm s-1. The permeability coefficient for protons in galactolipids, however, was determined to be about six orders of magnitude higher than the value for potassium ions. The HCl permeation mechanism through the lipid membranes was determined from diffusion potentials measured in HCl gradients. Our results suggest that HCl was not transported as neutral molecules. The data is discussed with regard to the function of galactolipids in the ion transport through thylakoid membranes. PMID:8061192

Thermoelectric Properties of In-Doped Cu2ZnGeSe4

NASA Astrophysics Data System (ADS)

Chetty, R.; Bali, A.; Femi, O. E.; Chattopadhyay, K.; Mallik, R. C.

2016-03-01

Recently, much research has been focused on finding new thermoelectric materials. Cu-based quaternary chalcogenides that belong to A2BCD4 (A = Cu; B = Zn, Cd; C = Sn, Ge; D = S, Se, Te) are wide band gap materials and one of the potential thermoelectric materials due to their complex crystal structures. In this study, In-doped quaternary compounds Cu2ZnGe1- x In x Se4 ( x = 0, 0.025, 0.05, 0.075, 0.1) were prepared by a solid state synthesis method. Powder x-ray diffraction patterns of all the samples showed a tetragonal crystal structure (space group I- 42m) of the main phase with a trace amount of impurity phases, which was further confirmed by Rietveld analysis. The elemental composition of all the samples showed a slight deviation from the nominal composition with the presence of secondary phases. All the transport properties were measured in the temperature range 373-673 K. The electrical resistivity of all the samples initially decreased up to ˜470 K and then increased with increase in temperature upto 673 K, indicating the transition from semiconducting to metallic behavior. Positive Seebeck coefficients for all the samples revealed that holes are the majority carriers in the entire temperature range. The substitution of In3+ on Ge4+ introduces holes and results in the decrease of resistivity as well as the Seebeck coefficient, thereby leading to the optimization of the power factor. The lattice thermal conductivity of all the samples decreased with increasing temperature, indicating the presence of phonon-phonon scattering. As a result, the thermoelectric figure of merit ( zT) of the doped sample showed an increase as compared to the undoped compound.

Effect of High Pressure and Temperature on Structural, Thermodynamic and Thermoelectric Properties of Quaternary CoFeCrAl Alloy

NASA Astrophysics Data System (ADS)

Bhat, Tahir Mohiuddin; Gupta, Dinesh C.

2018-03-01

Employing first-principles based on density functional theory we have investigated the structural, magneto-electronic, thermoelectric and thermodynamic properties of quaternary Heusler alloy CoFeCrAl. Electronic band structure displays that CoFeCrAl is an indirect band gap semiconductor in spin-down state with the band gap value of 0.65 eV. Elastic constants reveal CoFeCrAl is a mechanically stable structure having a Debye temperature of 648 K along with a high melting temperature (2130 K). The thermoelectric properties in the temperature range 50-800 K have been calculated. CoFeCrAl possesses a high Seebeck coefficient of - 46 μV/K at room temperature along with the huge power factor of ˜ 4.8 (1012 μW cm-1 K-2 s-1) which maximizes the figure-of-merit up to ˜ 0.75 at 800 K temperature and suggesting CoFeCrAl as potential thermoelectric material. The effect of high pressure and high temperature on the thermal expansion, Grüneisen parameter and heat capacity were also studied by using the quasi-harmonic Debye model.

Numerical study of the electronic structure, elastic and optical properties of defect quaternary semiconductor CuGaSnSe4

NASA Astrophysics Data System (ADS)

Shen, Kesheng; Lu, Hai; Zhang, Xianzhou; Jiao, Zhaoyong

2018-06-01

The electronic structure, elastic and optical properties of the defect quaternary semiconductor CuGaSnSe4 in I 4 bar structure are systematically investigated using first-principles calculations. We summarize and discuss some of the studies on CuGaSnSe4 in partially ordered chalcopyrite structure and find that there are three atomic arrangements so far, but it is still uncertain which is the most stable. Through detailed simulation and comparison with the corresponding literature, we get three models and predict that M1 model should be the most stable. The band structure and optical properties of compound CuGaSnSe4, including dielectric constant, refractive index and absorption spectrum, are drawn for a more intuitive understanding. The elastic constants are also calculated, which not only prove that CuGaSnSe4 in I 4 bar structure is stable naturally but also help solve the problem of no data to accurately predict axial thermal expansion coefficients. The calculated values of the zero frequency dielectric constant and refractive index are comparable to those of the corresponding chalcopyrite structure but slightly larger.

Diffusion of Sites versus Polymers in Polyelectrolyte Complexes and Multilayers.

PubMed

Fares, Hadi M; Schlenoff, Joseph B

2017-10-18

It has long been assumed that the spontaneous formation of materials such as complexes and multilayers from charged polymers depends on (inter)diffusion of these polyelectrolytes. Here, we separately examine the mass transport of polymer molecules and extrinsic sites-charged polyelectrolyte repeat units balanced by counterions-within thin films of polyelectrolyte complex, PEC, using sensitive isotopic labeling techniques. The apparent diffusion coefficients of these sites within PEC films of poly(diallyldimethylammonium), PDADMA, and poly(styrenesulfonate), PSS, are at least 2 orders of magnitude faster than the diffusion of polyelectrolytes themselves. This is because site diffusion requires only local rearrangements of polyelectrolyte repeat units, placing far fewer kinetic limitations on the assembly of polyelectrolyte complexes in all of their forms. Site diffusion strongly depends on the salt concentration (ionic strength) of the environment, and diffusion of PDADMA sites is faster than that of PSS sites, accounting for the asymmetric nature of multilayer growth. Site diffusion is responsible for multilayer growth in the linear and into the exponential regimes, which explains how PDADMA can mysteriously "pass through" layers of PSS. Using quantitative relationships between site diffusion coefficient and salt concentration, conditions were identified that allowed the diffusion length to always exceed the film thickness, leading to full exponential growth over 3 orders of magnitude thickness. Both site and polymer diffusion were independent of molecular weight, suggesting that ion pairing density is a limiting factor. Polyelectrolyte complexes are examples of a broader class of dynamic bulk polymeric materials that (self-) assemble via the transport of cross-links or defects rather than actual molecules.

Thermochemical and kinetic aspects of the sulfurization of Cu-Sb and Cu-Bi thin films

NASA Astrophysics Data System (ADS)

Colombara, Diego; Peter, Laurence M.; Rogers, Keith D.; Hutchings, Kyle

2012-02-01

CuSbS2 and Cu3BiS3 are being investigated as part of a search for new absorber materials for photovoltaic devices. Thin films of these chalcogenides were produced by conversion of stacked and co-electroplated metal precursor layers in the presence of elemental sulfur vapour. Ex-situ XRD and SEM/EDS analyses of the processed samples were employed to study the reaction sequence with the aim of achieving compact layer morphologies. A new “Time-Temperature-Reaction” (TTR) diagram and modified Pilling-Bedworth coefficients have been introduced for the description and interpretation of the reaction kinetics. For equal processing times, the minimum temperature required for CuSbS2 to appear is substantially lower than for Cu3BiS3, suggesting that interdiffusion across the interfaces between the binary sulfides is a key step in the formation of the ternary compounds. The effects of the heating rate and sulfur partial pressure on the phase evolution as well as the potential losses of Sb and Bi during the processes have been investigated experimentally and the results related to the equilibrium pressure diagrams obtained via thermochemical computation.

Impedance and magnetoelectric characteristics of (1 - x)BaTiO3- xLa0.7Sr0.3MnO3 ( x = 0.1 and 0.3) nano-composites

NASA Astrophysics Data System (ADS)

Nayek, C.; Murugavel, P.; Dinesh Kumar, S.; Subramanian, V.

2015-08-01

We have synthesized the phase-pure (1 - x)BaTiO3- xLa0.7Sr0.3MnO3 ( x = 0.1 and 0.3) magnetoelectric composites without interdiffusion among the existing phases. The magnetic measurements revealed an anomaly at the ferroelectric Curie temperature (393 K) of BaTiO3, and the dielectric data revealed an anomaly at the ferromagnetic transition temperature (360 K) of La0.7Sr0.3MnO3 ascertaining the magnetoelectric coupling in the composite. Impedance analysis indicated dipolar polarization contributions to the dielectric spectrum with two non-Debye-type relaxations. Both the grain and grain boundary contributions were present in the system with dominant grain boundary effect in all the composites. The composites show semiconducting behavior with the barrier hopping-type conducting mechanism. To avoid the free charge carrier and the space charge contributions, the magnetoelectric response was measured at high frequency range. The maximum values of magnetoelectric voltage coefficient measured at 100 kHz were 221 and 219 mV/Oe-cm for x = 0.1 and 0.3 samples, respectively.

Simulation of thermally induced processes of diffusion and phase formation in layered binary metallic systems

NASA Astrophysics Data System (ADS)

Rusakov, V. S.; Sukhorukov, I. A.; Zhankadamova, A. M.; Kadyrzhanov, K. K.

2010-05-01

Results of the simulation of thermally induced processes of diffusion and phase formation in model and experimentally investigated layered binary metallic systems are presented. The physical model is based on the Darken phenomenological theory and on the mechanism of interdiffusion of components along the continuous diffusion channels of phases in the two-phase regions of the system. The simulation of processes in the model systems showed that the thermally stabilized concentration profiles in two-layer binary metallic systems are virtually independent of the partial diffusion coefficients; for the systems with the average concentration of components that is the same over the sample depth, the time of the thermal stabilization of the structural and phase state inhomogeneous over the depth grows according to a power law with increasing thickness of the system in such a manner that the thicknesses of the surface layers grow, while the thickness of the intermediate layer approaches a constant value. The results of the simulation of the processes of diffusion and phase formation in experimentally investigated layered binary systems Fe-Ti and Cu-Be upon sequential isothermal and isochronous annealings agree well with the experimental data.

Atomistic modeling of metallic thin films by modified embedded atom method

NASA Astrophysics Data System (ADS)

Hao, Huali; Lau, Denvid

2017-11-01

Molecular dynamics simulation is applied to investigate the deposition process of metallic thin films. Eight metals, titanium, vanadium, iron, cobalt, nickel, copper, tungsten, and gold, are chosen to be deposited on the aluminum substrate. The second nearest-neighbor modified embedded atom method potential is adopted to predict their thermal and mechanical properties. When quantifying the screening parameters of the potential, the error for Young's modulus and coefficient of thermal expansion between the simulated results and the experimental measurements is less than 15%, demonstrating the reliability of the potential to predict metallic behaviors related to thermal and mechanical properties. A set of potential parameters which governs the interactions between aluminum and other metals in a binary system is also generated from ab initio calculation. The details of interfacial structures between the chosen films and substrate are successfully simulated with the help of these parameters. Our results indicate that the preferred orientation of film growth depends on the film crystal structure, and the inter-diffusion at the interface is correlated the cohesive energy parameter of potential for the binary system. Such finding provides an important basis to further understand the interfacial science, which contributes to the improvement of the mechanical properties, reliability and durability of films.

Diffusion Barrier Selection from Refractory Metals (Zr, Mo and Nb) via Interdiffusion Investigation for U-Mo RERTR Fuel Alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

K. Huang; C. Kammerer; D. D. Keiser, Jr.

2014-04-01

U-Mo alloys are being developed as low enrichment monolithic fuel under the Reduced Enrichment for Research and Test Reactor (RERTR) Program. Diffusional interactions between the U-Mo fuel alloy and Al-alloy cladding within the monolithic fuel plate construct necessitate incorporation of a barrier layer. Fundamentally, a diffusion barrier candidate must have good thermal conductivity, high melting point, minimal metallurgical interaction, and good irradiation performance. Refractory metals, Zr, Mo, and Nb are considered based on their physical properties, and the diffusion behavior must be carefully examined first with U-Mo fuel alloy. Solid-to-solid U-10wt.%Mo vs. Mo, Zr, or Nb diffusion couples were assembledmore » and annealed at 600, 700, 800, 900 and 1000 degrees C for various times. The interdiffusion microstructures and chemical composition were examined via scanning electron microscopy and electron probe microanalysis, respectively. For all three systems, the growth rate of interdiffusion zone were calculated at 1000, 900 and 800 degrees C under the assumption of parabolic growth, and calculated for lower temperature of 700, 600 and 500 degrees C according to Arrhenius relationship. The growth rate was determined to be about 10 3 times slower for Zr, 10 5 times slower for Mo and 10 6 times slower for Nb, than the growth rates reported for the interaction between the U-Mo fuel alloy and pure Al or Al-Si cladding alloys. Zr, however was selected as the barrier metal due to a concern for thermo- mechanical behavior of UMo/Nb interface observed from diffusion couples, and for ductile-to-brittle transition of Mo near room temperature.« less

Low resistance AL2O3 magnetic tunnel junctions optimized through in situ conductance measurements

NASA Astrophysics Data System (ADS)

Wolfman, J.; Mauri, D.; Lin, T.; Yang, J.; Chen, T.

2005-06-01

In situ electrical conductance is used to monitor the growth and natural oxidation of aluminum on top of a CoFe electrode. Light oxidation is found to enhance the electron specular scattering of the CoFe/vacuum interface. Aluminum deposited onto CoFe intermixes to a depth of a few atomic layers, however, subsequent natural oxidation tends to reverse this interdiffusion through oxygen-driven A1 segregation. At the right A1 thickness, natural oxidation creates a clean and specular CoFe /AlOx interface very similar to the best achievable CoFe/vacuum interface. For thicker A1, natural oxidation leaves behind underoxidized AlOx and most importantly an interdiffused CoFe /Al interface. Using 2Torr×150-s natural oxidation, we have fabricated magnetic tunnel junctions (MTJs) with a peak tunnel magnetoresistance (TMR) of 18% for a resistance area product of 7Ωμm2, at the A1 metal thickness of 6 Å. With the same oxidation process TMR drops to only 8% when A1 is increased to 9 Å. Contrary to the accepted view, we do not attribute this TMR drop to A1 underoxidation, but primarily to the interdiffusion at the CoFe /Al interface. This assertion is strongly supported by a second set of MTJs differing only by the insertion of a nano-oxide layer (NOL) on top of CoFe. In this case when Al is increased from 6 to 9 Å, the TMR does not drop but increases from 16% to 27%. This is significant because NOL is found to effectively prevent Al diffusion into CoFe. NOL is also found to act as a reservoir of oxygen, which is subsequently consumed by Al.

Superconductivity in Bi/Ni bilayer system: Clear role of superconducting phases found at Bi/Ni interface

NASA Astrophysics Data System (ADS)

Liu, L. Y.; Xing, Y. T.; Merino, I. L. C.; Micklitz, H.; Franceschini, D. F.; Baggio-Saitovitch, E.; Bell, D. C.; Solórzano, I. G.

2018-01-01

Bi/Ni bilayers with varying Bi and Ni layer thicknesses have been prepared by (a) pulsed-laser deposition (PLD) at 300 K and (b) thermal evaporation at 4.2 K. A two-step superconducting transition appears on the electrical transport measurements in the samples prepared by PLD. High-resolution transmission and scanning transmission electron microscopy, supported by energy-dispersive x-ray spectroscopy (EDXS) analysis, reveal that two superconducting intermetallic alloys, namely NiBi and NiBi3, are formed by interdiffusion, if the bilayers are prepared at 300 K. The Tc of the two phases behaves very differently in an external magnetic field and the upper critical magnetic fields at zero temperature [Bc 2(0 ) ] were estimated as 1.1 and 7.4 T, respectively. The lower value corresponds to the Bc 2(0) of NiBi3 phase and the higher one is supposed to be of NiBi. These alloys are responsible for the superconductivity and the two-step transition appearing in the Bi/Ni bilayer system. Surprisingly, the Bi-rich phase (NiBi3) is formed near the Ni layer, while the Ni-rich phase (NiBi) is formed far from the Ni layer. The EDXS analysis at nanometer scale clearly shows an unusual increase of Ni concentration near the interface of Bi/substrate. The limited thickness of Bi layer in the interdiffusion process results in an unexpected distribution of Ni concentration. Samples prepared at 4.2 K after annealing at 300 K do not show any superconductivity, which indicates that a nonepitaxial Bi/Ni interface does not induce superconductivity in the case interdiffusion does not occur. These results offer a deeper understanding of the superconductivity in the Bi/Ni bilayer system.

A novel route to recognizing quaternary ammonium cations using electrospray mass spectrometry.

PubMed

Shackman, Holly M; Ding, Wei; Bolgar, Mark S

2015-01-01

Characterizing and elucidating structures is a commonplace and necessary activity in the pharmaceutical industry with mass spectrometry and NMR being the primary tools for analysis. Although many functional groups are readily identifiable, quaternary ammonium cations have proven to be difficult to unequivocally identify using these techniques. Due to the lack of an N-H bond, quaternary ammonium groups can only be detected in the (1)H NMR spectra by weak signals generated from long-range (14)N-H coupling, which by themselves are inconclusive evidence of a quaternary ammonium functional group. Due to their low intensity, these signals are frequently not detected. Additionally, ions cannot be differentiated in a mass spectrum as an M(+) or [M + H](+) ion without prior knowledge of the compound's structure. In order to utilize mass spectrometry as a tool for determining this functionality, ion cluster formation of quaternary ammonium cations and non-quaternary amines was studied using electrospray ionization. Several mobile phase modifiers were compared; however, the addition of small amounts of trifluoroacetic acid proved superior in producing characteristic and intense [M +2TFA](-) clusters for compounds containing quaternary ammonium cations when using negative electrospray. By fragmenting this characteristic ion using CID, nearly all compounds studied could be unambiguously identified as containing a quaternary ammonium cation or a non-quaternary amine attributable to the presence (non-quaternary amine) or absence (quaternary ammonium cation) of the resulting [2TFA + H](-) ion in the product spectra. This method of analysis provides a rapid, novel, and reliable technique for indicating the presence of quaternary ammonium cations in order to aid in structural elucidation.

Atomistic modeling and simulation of the role of Be and Bi in Al diffusion in U-Mo fuel

NASA Astrophysics Data System (ADS)

Hofman, G. L.; Bozzolo, G.; Mosca, H. O.; Yacout, A. M.

2011-07-01

Within the RERTR program, previous experimental and modeling studies identified Si as the alloying addition to the Al cladding responsible for inhibiting Al interdiffusion in the UMo fuel. However, difficulties with reprocessing have rendered this choice inappropriate, leading to the need to study alternative elements. In this work, we discuss the results of an atomistic modeling effort which allows for the systematic study of several possible alloying additions. Based on the behavior observed in the phase diagrams, beryllium or bismuth additions suggest themselves as possible options to replace Si. The results of temperature-dependent simulations using the Bozzolo-Ferrante-Smith (BFS) method for the energetics for varying concentrations of either element are shown, indicating that Be could have a substantial effect in stopping Al interdiffusion, while Bi does not. Details of the calculations and the dependence of the role of each alloying addition as a function of temperature and concentration (of beryllium or bismuth in Al) are shown.

Polycrystalline silicon on tungsten substrates

NASA Technical Reports Server (NTRS)

Bevolo, A. J.; Schmidt, F. A.; Shanks, H. R.; Campisi, G. J.

1979-01-01

Thin films of electron-beam-vaporized silicon were deposited on fine-grained tungsten substrates under a pressure of about 1 x 10 to the -10th torr. Mass spectra from a quadrupole residual-gas analyzer were used to determine the partial pressure of 13 residual gases during each processing step. During separate silicon depositions, the atomically clean substrates were maintained at various temperatures between 400 and 780 C, and deposition rates were between 20 and 630 A min. Surface contamination and interdiffusion were monitored by in situ Auger electron spectrometry before and after cleaning, deposition, and annealing. Auger depth profiling, X-ray analysis, and SEM in the topographic and channeling modes were utilized to characterize the samples with respect to silicon-metal interface, interdiffusion, silicide formation, and grain size of silicon. The onset of silicide formation was found to occur at approximately 625 C. Above this temperature tungsten silicides were formed at a rate faster than the silicon deposition. Fine-grain silicon films were obtained at lower temperatures.

Enhanced water vapour flow in silica microchannels and interdiffusive water vapour flow through anodic aluminium oxide (AAO) membranes

NASA Astrophysics Data System (ADS)

Lei, Wenwen; McKenzie, David R.

2015-12-01

Enhanced liquid water flows through carbon nanotubes reinvigorated the study of moisture permeation through membranes and micro- and nano-channels. The study of water vapour through micro-and nano-channels has been neglected even though water vapour is as important as liquid water for industry, especially for encapsulation of electronic devices. Here we measure moisture flow rates in silica microchannels and interdiffusive water vapour flows in anodic aluminium oxide (AAO) membrane channels for the first time. We construct theory for the flow rates of the dominant modes of water transport through four previously defined standard configurations and benchmark it against our new measurements. The findings show that measurements of leak behaviour made using other molecules, such as helium, are not reliable. Single phase water vapour flow is overestimated by a helium measurement, while Washburn or capillary flow is underestimated or for all channels when boundary slip applies, to an extent that depends on the slip length for the liquid phase flows.

Biobased, self-healable, high strength rubber with tunicate cellulose nanocrystals.

PubMed

Cao, Liming; Yuan, Daosheng; Xu, Chuanhui; Chen, Yukun

2017-10-19

Cellulose nanocrystals represent a promising and environmentally friendly reinforcing nanofiller for polymers, especially for rubbers and elastomers. Here, a simple approach via latex mixing is used to fabricate biobased, healable rubber with high strength based on epoxidized natural rubber (ENR). Tunicate cellulose nanocrystals (t-CNs) isolated from marine biomass with a high aspect ratio are used to improve both mechanical properties and self-healing behavior of the material. By introducing dynamic hydrogen bond supramolecular networks between oxygenous groups of ENR and hydroxyl groups on the t-CN surface, together with chain interdiffusion in permanently but slightly cross-linked rubber, self-healing and mechanical properties are facilitated significantly in the resulting materials. Macroscopic tensile healing behavior and microscopic morphology analyses are carried out to evaluate the performance of the materials. Both t-CN content and healing time have significant influence on healing behavior. The results indicate that a synergistic effect between molecular interdiffusion and dynamic hydrogen bond supramolecular networks leads to the improved self-healing behavior.

Microstructural development from interdiffusion and reaction between Usbnd Mo and AA6061 alloys annealed at 600° and 550 °C

NASA Astrophysics Data System (ADS)

Perez, E.; Keiser, D. D.; Sohn, Y. H.

2016-08-01

The U.S. Material Management and Minimization Reactor Conversion Program is developing low enrichment fuel systems encased in Al-alloy for use in research and test reactors. Monolithic fuel plates have local regions where the Usbnd Mo fuel plate may come into contact with the Al-alloy 6061 (AA6061) cladding. This results in the development of interdiffusion zones with complex microstructures with multiple phases. In this study, the microstructural development of diffusion couples, Usbnd 7 wt%Mo, Usbnd 10 wt%Mo, and Usbnd 12 wt%Mo vs. AA6061, annealed at 600 °C for 24 h and at 550 °C for 1, 5, and 20 h, were analyzed by scanning electron microscopy with x-ray energy dispersive spectroscopy. The microstructural development and kinetics were compared to diffusion couples Usbnd Mo vs. high purity Al and binary Alsbnd Si alloys. The diffusion couples developed complex interaction regions where phase development was influenced by the alloying additions of the AA6061.

Aluminum silicide microparticles transformed from aluminum thin films by hypoeutectic interdiffusion

PubMed Central

2014-01-01

Aluminum silicide microparticles with oxidized rough surfaces were formed on Si substrates through a spontaneous granulation process of Al films. This microparticle formation was caused by interdiffusion of Al and Si atoms at hypoeutectic temperatures of Al-Si systems, which was driven by compressive stress stored in Al films. The size, density, and the composition of the microparticles could be controlled by adjusting the annealing temperature, time, and the film thickness. High-density microparticles of a size around 10 μm and with an atomic ratio of Si/Al of approximately 0.8 were obtained when a 90-nm-thick Al film on Si substrate was annealed for 9 h at 550°C. The microparticle formation resulted in a rapid increase of the sheet resistance, which is a consequence of substantial consumption of Al film. This simple route to size- and composition-controllable microparticle formation may lay a foundation stone for the thermoelectric study on Al-Si alloy-based heterogeneous systems. PMID:24994964

Aluminum silicide microparticles transformed from aluminum thin films by hypoeutectic interdiffusion.

PubMed

Noh, Jin-Seo

2014-01-01

Aluminum silicide microparticles with oxidized rough surfaces were formed on Si substrates through a spontaneous granulation process of Al films. This microparticle formation was caused by interdiffusion of Al and Si atoms at hypoeutectic temperatures of Al-Si systems, which was driven by compressive stress stored in Al films. The size, density, and the composition of the microparticles could be controlled by adjusting the annealing temperature, time, and the film thickness. High-density microparticles of a size around 10 μm and with an atomic ratio of Si/Al of approximately 0.8 were obtained when a 90-nm-thick Al film on Si substrate was annealed for 9 h at 550°C. The microparticle formation resulted in a rapid increase of the sheet resistance, which is a consequence of substantial consumption of Al film. This simple route to size- and composition-controllable microparticle formation may lay a foundation stone for the thermoelectric study on Al-Si alloy-based heterogeneous systems.

Electronic, structural and chemical properties of GaAs/ZnSe heterovalent interfaces as dependent on MBE growth conditions and ex situ annealing

NASA Astrophysics Data System (ADS)

Komissarova, T. A.; Lebedev, M. V.; Sorokin, S. V.; Klimko, G. V.; Sedova, I. V.; Gronin, S. V.; Komissarov, K. A.; Calvet, W.; Drozdov, M. N.; Ivanov, S. V.

2017-04-01

A study of electronic, structural and chemical properties of GaAs/ZnSe heterovalent interfaces (HI) in dependence on molecular beam epitaxy (MBE) growth conditions and post-growth annealing was performed. Initial GaAs surface reconstructions ((2 × 4)As or c(4 × 4)As) and ZnSe growth mode (MBE or migration-enhanced epitaxy (MEE)) were varied for different undoped and n-doped heterovalent structures. Although all the structures have low extended defect density (less than 106 cm-2) and rather small (less than 5 nm) atomic interdiffusion at the HI, the structural, chemical and electronic properties of the near-interface area (short-distance interdiffusion effects, dominant chemical bonds, and valence band offset values) as well as electrical properties of the n-GaAs/n-ZnSe heterovalent structures were found to be influenced strongly by the MBE growth conditions and post-growth annealing.

Effects of MAR-M247 substrate (modified) composition on coating oxidation coating/substrate interdiffusion. M.S. Thesis. Final Report; [protective coatings for hot section components of gas turbine engines

NASA Technical Reports Server (NTRS)

Pilsner, B. H.

1985-01-01

The effects of gamma+gamma' Mar-M247 substrate composition on gamma+beta Ni-Cr-Al-Zr coating oxidation and coating/substrate interdiffusion were evaluated. These results were also compared to a prior study for a Ni-Cr-Al-Zr coated gamma Ni-Cr-Al substrate with equivalent Al and Cr atomic percentages. Cyclic oxidation behavior at 1130 C was investigated using change in weight curves. Concentration/distance profiles were measured for Al, Cr, Co, W, and Ta. The surface oxides were examined by X-ray diffraction and scanning electron microscopy. The results indicate that variations of Ta and C concentrations in the substrate do not affect oxidation resistance, while additions of grain boundary strengthening elements (Zr, Hf, B) increase oxidation resistance. In addition, the results indicate that oxidation phenomena in gamma+beta/gamma+gamma' Mar-M247 systems have similar characteristics to the l gamma+beta/gamma Ni-Cr-Al system.

S–Te Interdiffusion within Grains and Grain Boundaries in CdTe Solar Cells

DOE PAGES

Li, C.; Poplawsky, J.; Paudel, N.; ...

2014-09-19

At the CdTe/CdS interface, a significant Te-S interdiffusion has been found a few nanometers into the grain interiors with scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS). S substitution at Te sites has been directly resolved in CdTe with STEM Z-contrast images. Moreover, when enough S substitutes for Te, a structural transformation from zinc-blende to wurtzite has been observed. Cl segregation has also been found at the interface. STEM electron-beam-induced current (EBIC) shows that the p-n junction occurs a few nm into the CdTe grains, which is consistent with the S diffusion range we observe. The shiftmore » of the p-n junction suggests a buried homo-junction which would help reduce non-radiative recombination at the junction. Meanwhile, long-range S diffusion in CdTe grain boundaries (GBs) has been detected, as well as Te and Cl diffusion in CdS GBs.« less

Quaternary and Geomorphology.

ERIC Educational Resources Information Center

Andrews, J. T.; Graf, W. L.

1983-01-01

Highlights conferences and meetings of organizations involved with quaternary geology and geomorphology, including International Union of Quaternary Research Conference held in Moscow. The impetus of a revision of "The Quaternary of the United States" resulted from this conference. Includes activities/aims of "Friends of the…

21 CFR 172.165 - Quaternary ammonium chloride combination.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Quaternary ammonium chloride combination. 172.165... HUMAN CONSUMPTION Food Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used in food in accordance with the...

Quaternary prevention: reviewing the concept.

PubMed

Martins, Carlos; Godycki-Cwirko, Maciek; Heleno, Bruno; Brodersen, John

2018-12-01

According to the Wonca International Dictionary for General/Family Practice Quaternary Prevention is defined as: 'Action taken to identify patient at risk of overmedicalization, to protect him from new medical invasion, and to suggest to him interventions, which are ethically acceptable.' The concept of quaternary prevention was initially proposed by Marc Jamoulle and the targets were mainly patients with illness but without a disease. The purpose of this opinion article is to open the debate around a new possible definition and a new conceptual model of quaternary prevention based on the belief that quaternary prevention should be present in physicians' minds for every intervention they suggest to a patient. The debate around quaternary prevention is vital in the context of contemporary medicine and has expanded worldwide. The human being may suffer harm from medical interventions from conception, during their childhood, during their entire healthy lifetime as well as during a self-limited disease, a chronic disease, or a terminal disease. The current definition of quaternary prevention has limitations because it excludes patients and medical interventions where a quaternary prevention perspective would be needed and useful to protect patients from harm. In this context, a new definition and conceptual model of quaternary prevention is proposed. In this new proposal, quaternary prevention is defined as an 'action taken to protect individuals (persons/patients) from medical interventions that are likely to cause more harm than good.'

Variable diffusion rates during exsolution coarsening in the presence of fluids.

NASA Astrophysics Data System (ADS)

Putnis, Andrew; Prent, Alexander

2017-04-01

The scale of exsolution textures in mineral solid solutions has long been used as an indicator of thermal history during cooling. The theory of spinodal decomposition in an anisotropic solid and subsequent coarsening of exsolution textures as a function of temperature and cooling rate is well developed (see Petrishcheva et al., 2009 and Abart et al., 2009 for a review of the Cahn-Hilliard theory). For the case of exsolution in the alkali feldspar solid solution [(Na,K)AlSi3O8] the characteristic texture shows compositional fluctuations in Na,K with a wavelength that depends on the cooling rate. The cooling rate is determined from knowledge of the Na-K interdiffusion coefficient, assuming that the unmixing is simply due to the interdiffusion of Na and K in an otherwise fixed tetrahedral Al,Si framework. Cryptoperthites and mesoperthites with a periodic lamellar microstructure are considered to be the end-result of such a solid-state exsolution process. Later-stage fluid infiltration results in patch perthites that are formed at a sharp replacement front by a dissolution-precipitation mechanism (Parsons et al., 2015). Patch perthites have an easily recognizable texture and are clear indicators of a reaction with an aqueous solution. The distinction is thus drawn between crypto- and meso-perthite showing periodic lamellae, associated with a solid-state exsolution process, and the patch perthite showing irregular domains of Na-rich and K-rich feldspars associated with a fluid mediated reprecipitation process. However, the presence of fluids can also enhance the coarsening of lamellar exsolution textures, retaining an apparently solid-state microstructure but with a length scale that is dependent on local recrystallization driven by fluid infiltration. Examples will be given from alkali feldspars in granitic rocks where it is clearly demonstrable that cooling rates cannot be inferred from such exsolution textures. The variability in Na,K diffusion rates and thus different length scales of exsolution are likely to be due to the efficiency of diffusional transport through a fluid phase, which is influenced by differences in fluid-induced micro- and nano-porosity. Abart R. et al. (2009) Am. J. Sci. 309, 450-475. Petrishcheva E. and Abart R. (2009) Am. J. Sci, 309, 431-449. Parsons I. et al., (2015) Am. Min. 100, 1277-1303.

Designing Novel Quaternary Quantum Reversible Subtractor Circuits

NASA Astrophysics Data System (ADS)

Haghparast, Majid; Monfared, Asma Taheri

2018-01-01

Reversible logic synthesis is an important area of current research because of its ability to reduce energy dissipation. In recent years, multiple valued logic has received great attention due to its ability to reduce the width of the reversible circuit which is a main requirement in quantum technology. Subtractor circuits are between major components used in quantum computers. In this paper, we will discuss the design of a quaternary quantum reversible half subtractor circuit using quaternary 1-qudit, 2-qudit Muthukrishnan-Stroud and 3-qudit controlled gates and a 2-qudit Generalized quaternary gate. Then a design of a quaternary quantum reversible full subtractor circuit based on the quaternary half subtractor will be presenting. The designs shall then be evaluated in terms of quantum cost, constant input, garbage output, and hardware complexity. The proposed quaternary quantum reversible circuits are the first attempt in the designing of the aforementioned subtractor.

Revealing the optoelectronic and thermoelectric properties of the Zintl quaternary arsenides ACdGeAs{sub 2} (A = K, Rb)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Azam, Sikander; Khan, Saleem Ayaz; Goumri-Said, Souraya, E-mail: Souraya.Goumri-Said@chemistry.gatech.edu

Highlights: • Zintl tetragonal phase ACdGeAs{sub 2} (A = K, Rb) are chalcopyrite and semiconductors. • Their direct band gap is suitable for PV, optolectronic and thermoelectric applications. • Combination of DFT and Boltzmann transport theory is employed. • The present arsenides are found to be covalent materials. - Abstract: Chalcopyrite semiconductors have attracted much attention due to their potential implications in photovoltaic and thermoelectric applications. First principle calculations were performed to investigate the electronic, optical and thermoelectric properties of the Zintl tetragonal phase ACdGeAs{sub 2} (A = K, Rb) using the full potential linear augmented plane wave method andmore » the Engle–Vosko GGA (EV–GGA) approximation. The present compounds are found semiconductors with direct band gap and covalent bonding character. The optical transitions are investigated via the dielectric function (real and imaginary parts) along with other related optical constants including refractive index, reflectivity and energy-loss spectrum. Combining results from DFT and Boltzmann transport theory, we reported the thermoelectric properties such as the Seebeck’s coefficient, electrical and thermal conductivity, figure of merit and power factor as function of temperatures. The present chalcopyrite Zintl quaternary arsenides deserve to be explored for their potential applications as thermoelectric materials and for photovoltaic devices.« less

QuEChERS-based purification method coupled to ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to determine six quaternary ammonium compounds (QACs) in dairy products.

PubMed

Xian, Yanping; Dong, Hao; Wu, Yuluan; Guo, Xindong; Hou, Xiangchang; Wang, Bin

2016-12-01

QuEChERS-based purification coupled with UPLC-MS/MS method, was developed for six quaternary ammonium compounds (QACs) determination in dairy products. Powder samples were firstly dispersed by water. Protein in liquid milk was precipitated and sample solution was extracted by acetonitrile. QuEChERS-based purification was used to purify the solution. QACs were finally separated by HILIC column and detected in MRM mode of MS/MS under ESI(+). The stable isotope benzyl-2,3,4,5,6-d5-dimethyltetradecylammonium bromide (C14-BAC-d5) was used as an internal standard. This method was validated in terms of linearity, sensitivity, precision, accuracy. Linear relations were favorable for QACs over the selected concentration ranges of 0.2-50μg/L, with correlation coefficients greater than 0.999. The limits of detection (LODs) were in the range of 0.4-14.5μg/kg. Recoveries were between 91.2% and 115% with RSDs of 2.8-7.5% for intra-day precision and 3.7-6.7% for inter-day precision. This validated method was successfully applied to determine the QACs concentrations in dairy products. Copyright © 2016 Elsevier Ltd. All rights reserved.

Quaternary prevention: reviewing the concept

PubMed Central

Martins, Carlos; Godycki-Cwirko, Maciek; Heleno, Bruno; Brodersen, John

2018-01-01

Abstract Background: According to the Wonca International Dictionary for General/Family Practice Quaternary Prevention is defined as: ‘Action taken to identify patient at risk of overmedicalization, to protect him from new medical invasion, and to suggest to him interventions, which are ethically acceptable.’ The concept of quaternary prevention was initially proposed by Marc Jamoulle and the targets were mainly patients with illness but without a disease. Objectives: The purpose of this opinion article is to open the debate around a new possible definition and a new conceptual model of quaternary prevention based on the belief that quaternary prevention should be present in physicians’ minds for every intervention they suggest to a patient. Discussion: The debate around quaternary prevention is vital in the context of contemporary medicine and has expanded worldwide. The human being may suffer harm from medical interventions from conception, during their childhood, during their entire healthy lifetime as well as during a self-limited disease, a chronic disease, or a terminal disease. The current definition of quaternary prevention has limitations because it excludes patients and medical interventions where a quaternary prevention perspective would be needed and useful to protect patients from harm. In this context, a new definition and conceptual model of quaternary prevention is proposed. Conclusion: In this new proposal, quaternary prevention is defined as an ‘action taken to protect individuals (persons/patients) from medical interventions that are likely to cause more harm than good.’ PMID:29384397

ms 2: A molecular simulation tool for thermodynamic properties, release 3.0

NASA Astrophysics Data System (ADS)

Rutkai, Gábor; Köster, Andreas; Guevara-Carrion, Gabriela; Janzen, Tatjana; Schappals, Michael; Glass, Colin W.; Bernreuther, Martin; Wafai, Amer; Stephan, Simon; Kohns, Maximilian; Reiser, Steffen; Deublein, Stephan; Horsch, Martin; Hasse, Hans; Vrabec, Jadran

2017-12-01

A new version release (3.0) of the molecular simulation tool ms 2 (Deublein et al., 2011; Glass et al. 2014) is presented. Version 3.0 of ms 2 features two additional ensembles, i.e. microcanonical (NVE) and isobaric-isoenthalpic (NpH), various Helmholtz energy derivatives in the NVE ensemble, thermodynamic integration as a method for calculating the chemical potential, the osmotic pressure for calculating the activity of solvents, the six Maxwell-Stefan diffusion coefficients of quaternary mixtures, statistics for sampling hydrogen bonds, smooth-particle mesh Ewald summation as well as the ability to carry out molecular dynamics runs for an arbitrary number of state points in a single program execution.

Etude des interdiffusions en phase solide dans le contact Er/GaAs

NASA Astrophysics Data System (ADS)

Députier, S.; Guivarc'h, A.; Caulet, J.; Minier, M.; Guérin, R.

1994-05-01

Solid state interdiffusions between a thin film of erbium deposited under vacuum conditions and (001) and (111) GaAs substrates were investigated in the temperature range 350-800 ^{circ}C. Complementary analysis methods (RBS, X-ray diffraction) allow us to point out, according to annealing temperatures, successives steps of the interaction corresponding to different mixtures of phases, essentially binaries. These steps are strongly depending on the GaAs substrate orientation, especially the final step of the interdiffusions. On (001) GaAs, only two steps have been observed : no visible interaction is noticed between erbium and GaAs before 600 ^{circ}C ; the interaction begins at 600 ^{circ}C, evolves slightly and leads at 800 ^{circ}C to the nominal composition " Er{10}GaAs " which corresponds to a mixture of several phases Er5Ga3, Er and ErAs. On (111) GaAs, several steps of interaction have been found ; first of all, erbium reacts with the substrate at 400 ^{circ}C (Er5Ga3 + Er mixture), then the reaction is continuing at 600 ^{circ}C (Er5Ga3 + Er + ErAs mixture) before reaching at 800 ^{circ}C the nominal composition " Er{1,5}GaAs ", which is in fact a mixture of the three binaries ErAs + ErGa2 + Er3Ga5. It can be noticed that the 800 ^{circ}C annealing is not sufficient to reach the mixture of the phases ErAs + Ga which, according to the ternary phase diagram, should be the final stage of the interaction Er/GaAs. The analysis of the Er/GaAs interdiffusions shows that ErAs is the " key " compound around which the interaction progresses. This compound appears as an ideal candidate to realize epitaxial ErAs/GaAs heterostructures. Les interdiffusions en phase solide entre une couche mince d'erbium déposée dans des conditions d'ultra-vide et des substrats de GaAs orientés (001) et (111) ont été étudiées après des traitements thermiques d'une heure entre 350 et 800 ^{circ}C. L'utilisation de techniques complémentaires d'analyse (RBS, diffraction X) a permis de mettre en évidence, en fonction de la température de recuit, plusieurs étapes successives d'interaction correspondant à des mélanges de phases, essentiellement des binaires. Elles dépendent fortement de l'orientation du substrat de GaAs, en particulier l'étape finale des interactions. Sur GaAs (001), seules deux étapes ont été observées : avant 600 ^{circ}C, il n'y a pas d'interaction visible de l'erbium avec le substrat ; celle-ci ne s'amorce qu'à 600 ^{circ}C pour n'évoluer ensuite que faiblement et conduire, à 800 ^{circ}C, à une composition nominale " Er{10}GaAs ", mélange des phases Er5Ga3 + Er + ErAs. Sur GaAs (111), plusieurs étapes d'interaction sont observées : l'erbium réagit avec le substrat dès 400 ^{circ}C (mélange des phases Er5Ga3 + Er), puis l'interaction se poursuit à 600 ^{circ}C (mélange Er5Ga3 + Er + ErAs) avant d'atteindre à 800 ^{circ}C la composition nominale " Er{1,5}GaAs ", constituée d'un mélange de grains des trois binaires ErAs + ErGa2 + Er3Ga5. Il faut noter que le recuit à 800 ^{circ}C n'est pas suffisant pour atteindre le mélange de phases Ga + ErAs qui, selon le diagramme ternaire, devrait être le stade ultime de l'interaction Er/GaAs. L'analyse des interdiffusions Er/GaAs montre que ErAs est le composé " clé " autour duquel pivote l'interaction Er/GaAs. Ce composé apparaît comme un candidat idéal pour la réalisation d'hétérostructures épitaxiées ErAs/GaAs.

Publications - MP 141 | Alaska Division of Geological & Geophysical Surveys

Science.gov Websites

DGGS MP 141 Publication Details Title: Quaternary faults and folds in Alaska: A digital database Combellick, R.A., 2012, Quaternary faults and folds in Alaska: A digital database, in Koehler, R.D Quaternary faults, scale 1:3,700,000 (63.0 M) Digital Geospatial Data Digital Geospatial Data Quaternary

Optimization of chemical vapor deposition diamond films growth on steel: correlation between mechanical properties, structure, and composition.

PubMed

Laikhtman, A; Rapoport, L; Perfilyev, V; Moshkovich, A; Akhvlediani, R; Hoffman, A

2011-09-01

In the present work we perform optimization of mechanical and crystalline properties of CVD microcrystalline diamond films grown on steel substrates. A chromium-nitride (Cr-N) interlayer had been previously proposed to serve as a buffer for carbon and iron inter-diffusion and as a matching layer for the widely differing expansion coefficients of diamond and steel. However, adhesion and wear as well as crystalline perfection of diamond films are strongly affected by conditions of both Cr-N interlayer preparation and CVD diamond deposition. In this work we assess the effects of two parameters. The first one is the temperature of the Cr-N interlayer preparation: temperatures in the range of 500 degrees C-800 degrees C were used. The second one is diamond film thickness in the 0.5 microm-2 microm range monitored through variation of the deposition time from approximately 30 min to 2 hours. The mechanical properties of so deposited diamond films were investigated. For this purpose, scratch tests were performed at different indentation loads. The friction coefficient and wear loss were assessed. The mechanical and tribological properties were related to structure, composition, and crystalline perfection of diamond films which were extensively analyzed using different microscopic and spectroscopic techniques. It was found that relatively thick diamond film deposited on the Cr-N interlayer prepared at the temperature similar to that of the CVD process has the best mechanical and adhesion strength. This film was stable without visible cracks around the wear track during all scratch tests with different indentation loads. In other cases, cracking and delamination of the films took place at low to moderate indentation loads.

13C NMR and XPS characterization of anion adsorbent with quaternary ammonium groups prepared from rice straw, corn stalk and sugarcane bagasse

NASA Astrophysics Data System (ADS)

Cao, Wei; Wang, Zhenqian; Zeng, Qingling; Shen, Chunhua

2016-12-01

Despite amino groups modified crop straw has been intensively studied as new and low-cost adsorbent for removal of anionic species from water, there is still a lack of clear characterization for amino groups, especially quaternary ammonium groups in the surface of crop straw. In this study, we used 13C NMR and XPS technologies to characterize adsorbents with quaternary ammonium groups prepared from rice straw, corn stalk and sugarcane bagasse. 13C NMR spectra clearly showed the presence of quaternary ammonium groups in lignocelluloses structure of modified crop straw. The increase of nitrogen observed in XPS survey spectra also indicated the existence of quaternary ammonium group in the surface of the adsorbents. The curve fitting of high-resolution XPS N1s and C1s spectra were conducted to probe the composition of nitrogen and carbon contained groups, respectively. The results showed the proportion of quaternary ammonium group significantly increased in the prepared adsorbent's surface that was dominated by methyl/methylene, hydroxyl, quaternary ammonium, ether and carbonyl groups. This study proved that 13C NMR and XPS could be successfully utilized for characterization of quaternary ammonium modified crop straw adsorbents.

Microstructural development from interdiffusion and reaction between U–Mo and AA6061 alloys annealed at 600° and 550 °C

DOE PAGES

Perez, E.; Keiser, D. D.; Sohn, Y. H.

2016-05-10

The U.S. Material Management and Minimization Reactor Conversion Program is developing low enrichment fuel systems encased in Al-alloy for use in research and test reactors. Monolithic fuel plates have local regions where the Usingle bondMo fuel plate may come into contact with the Al-alloy 6061 (AA6061) cladding. This results in the development of interdiffusion zones with complex microstructures with multiple phases. In this study, the microstructural development of diffusion couples, U–7 wt%Mo, U–10 wt%Mo, and U–12 wt%Mo vs. AA6061, annealed at 600 °C for 24 h and at 550 °C for 1, 5, and 20 h, were analyzed by scanningmore » electron microscopy with x-ray energy dispersive spectroscopy. The microstructural development and kinetics were compared to diffusion couples U–Mo vs. high purity Al and binary Al–Si alloys. As a result, the diffusion couples developed complex interaction regions where phase development was influenced by the alloying additions of the AA6061.« less

Vanadium diffusion coating on HT-9 cladding for mitigating the fuel cladding chemical interactions

NASA Astrophysics Data System (ADS)

Lo, Wei-Yang; Yang, Yong

2014-08-01

Fuel cladding chemical interaction (FCCI) has been identified as one of the crucial issues for developing Ferritic/Martensitic (F/M) stainless steel claddings for metallic fuels in a fast reactor. The anticipated elevated temperature and high neutron flux can significantly aggravate the FCCI, in terms of formation of inter-diffusion and lower melting point eutectic phases. To mitigate the FCCI, vanadium carbide coating as a diffusion barrier was deposited on the HT-9 substrate using a pack cementation diffusion coating (PCDC) method, and the processing temperature was optimized down to 730 °C. A solid metallurgical bonding between the coating layer and substrate was achieved, and the coating is free from through depth cracks. The microstructural characterizations using SEM and TEM show a nanostructured grain structure. EDS/WDS and XRD analysis confirm the phase of coating layer as V2C. Diffusion couple tests at 660 °C for 100 h demonstrate that V2C layer with a thickness of less than 5 μm can effectively eliminate the inter-diffusion between the lanthanide cerium and HT-9 steel.

Solid Liquid Interdiffusion Bonding of Zn4Sb3 Thermoelectric Material with Cu Electrode

NASA Astrophysics Data System (ADS)

Lin, Y. C.; Lee, K. T.; Hwang, J. D.; Chu, H. S.; Hsu, C. C.; Chen, S. C.; Chuang, T. H.

2016-10-01

The ZnSb intermetallic compound may have thermoelectric applications because it is low in cost and environmentally friendly. In this study, a Zn4Sb3 thermoelectric element coated with a Ni barrier layer and a Ag reaction layer was bonded with a Ag-coated Cu electrode using a Ag/Sn/Ag solid-liquid interdiffusion bonding process. The results indicated that a Ni5Zn21 intermetallic phase formed easily at the Zn4Sb3/Ni interface, leading to sound adhesion. In addition, Sn film was found to react completely with the Ag layer to form a Ag3Sn intermetallic layer having a melting point of 480°C. The resulting Zn4Sb3 thermoelectric module can be applied at the optimized operation temperature (400°C) of Zn4Sb3 material as a thermoelectric element. The bonding strengths ranged from 14.9 MPa to 25.0 MPa, and shear tests revealed that the Zn4Sb3/Cu-joints fractured through the interior of the thermoelectric elements.

Overlay coating degradation by simultaneous oxidation and coating/substrate interdiffusion. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Nesbitt, J. A.

1983-01-01

Degradation of NiCrAlZr overlay coatings on various NiCrAl substrates was examined after cyclic oxidation. Concentration/distance profiles were measured in the coating and substrate after various oxidation exposures at 1150 C. For each stubstrate, the Al content in the coating decreased rapidly. The concentration/distance profiles, and particularly that for Al, reflected the oxide spalling resistance of each coated substrate. A numerical model was developed to simulate diffusion associated with overlay-coating degradation by oxidation and coating/substrate interdiffusion. Input to the numerical model consisted of the Cr and Al content of the coating and substrate, ternary diffusivities, and various oxide spalling parameters. The model predicts the Cr and Al concentrations in the coating and substrate after any number of oxidation/thermal cycles. The numerical model also predicts coating failure based on the ability of the coating to supply sufficient Al to the oxide scale. The validity of the model was confirmed by comparison of the predicted and measured concentration/distance profiles. The model was subsequently used to identify the most critical system parameters affecting coating life.

Reduction-oxidation Enabled Glass-ceramics to Stainless Steel Bonding Part I: screening of doping oxidants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dai, Steve Xunhu

Lithium silicate-based glass-ceramics with high coefficients of thermal expansion, designed to form matched hermetic seals in 304L stainless steel housing, show little evidence of interfacial chemical bonding, despite extensive inter-diffusion at the glass-ceramic-stainless steel (GC-SS) interface. A series of glass-ceramic compositions modified with a variety of oxidants, AgO, FeO, NiO, PbO, SnO, CuO, CoO, MoO 3 and WO 3, are examined for the feasibility of forming bonding oxides through reduction-oxidation (redox) at the GC-SS interface. The oxidants were selected according to their Gibbs free energy to allow for oxidation of Cr/Mn/Si from stainless steel, and yet to prevent a reductionmore » of P2O5 in the glass-ceramic where the P 2O 5 is to form Li 3PO 4 nuclei for growth of high expansion crystalline SiO 2 phases. Other than the CuO and CoO modified glass-ceramics, bonding from interfacial redox reactions were not achieved in the modified glass-ceramics, either because of poor wetting on the stainless steel or a reduction of the oxidants at the surface of glass-ceramic specimens rather than the GC-SS interface.« less

Fluid mechanical consequences of pendular activity, segmentation and pyloric outflow in the proximal duodenum of the rat and the guinea pig

PubMed Central

de Loubens, Clément; Lentle, Roger G.; Love, Richard J.; Hulls, Corrin; Janssen, Patrick W. M.

2013-01-01

We conducted numerical experiments to study the influence of non-propagating longitudinal and circular contractions, i.e. pendular activity and segmentation, respectively, on flow and mixing in the proximal duodenum. A lattice-Boltzmann numerical method was developed to simulate the fluid mechanical consequences for each of 22 randomly selected sequences of high-definition video of real longitudinal and radial contractile activity in the isolated proximal duodenum of the rat and guinea pig. During pendular activity in the rat duodenum, the flow was characterized by regions of high shear rate. Mixing was so governed by shearing deformation of the fluid that increased the interface between adjacent domains and accelerated their inter-diffusion (for diffusion coefficients approx. less than 10−8 m² s−1). When pendular activity was associated with a slow gastric outflow characteristic of post-prandial period, the dispersion was also improved, especially near the walls. Mixing was not promoted by isolated segmentative contractions in the guinea pig duodenum and not notably influenced by pylorus outflow. We concluded that pendular activity generates mixing of viscous fluids ‘in situ’ and accelerates the diffusive mass transfer, whereas segmentation may be more important in mixing particulate suspensions with high solid volume ratios. PMID:23536539

Fluid mechanical consequences of pendular activity, segmentation and pyloric outflow in the proximal duodenum of the rat and the guinea pig.

PubMed

de Loubens, Clément; Lentle, Roger G; Love, Richard J; Hulls, Corrin; Janssen, Patrick W M

2013-06-06

We conducted numerical experiments to study the influence of non-propagating longitudinal and circular contractions, i.e. pendular activity and segmentation, respectively, on flow and mixing in the proximal duodenum. A lattice-Boltzmann numerical method was developed to simulate the fluid mechanical consequences for each of 22 randomly selected sequences of high-definition video of real longitudinal and radial contractile activity in the isolated proximal duodenum of the rat and guinea pig. During pendular activity in the rat duodenum, the flow was characterized by regions of high shear rate. Mixing was so governed by shearing deformation of the fluid that increased the interface between adjacent domains and accelerated their inter-diffusion (for diffusion coefficients approx. less than 10(-8) m² s(-1)). When pendular activity was associated with a slow gastric outflow characteristic of post-prandial period, the dispersion was also improved, especially near the walls. Mixing was not promoted by isolated segmentative contractions in the guinea pig duodenum and not notably influenced by pylorus outflow. We concluded that pendular activity generates mixing of viscous fluids 'in situ' and accelerates the diffusive mass transfer, whereas segmentation may be more important in mixing particulate suspensions with high solid volume ratios.

Effect of Load on Friction-Wear Behavior of HVOF-Sprayed WC-12Co Coatings

NASA Astrophysics Data System (ADS)

Yifu, Jin; Weicheng, Kong; Tianyuan, Sheng; Ruihong, Zhang; Dejun, Kong

2017-07-01

A WC-12Co coating was sprayed on AISI H13 hot work mold steel using a high-velocity oxygen fuel. The morphologies, phase compositions, and distributions of chemical elements of the obtained coatings were analyzed using a field emission scanning electron microscope, x-ray diffraction, and energy-dispersive spectroscope (EDS), respectively. The friction-wear behaviors under different loads were investigated using a reciprocating wear tester; the morphologies and distributions of the chemical elements of worn tracks were analyzed using a SEM and its configured EDS, respectively. The results show the reunited grains of WC are held together by the Co binder; the primary phases of the coating are WC, Co, and a small amount of W2C and W, owing to the oxidation and decarburization of WC. Inter-diffusion of Fe and W between the coating and the substrate is shown, which indicates a good coating adhesion. The values of the average coefficient of friction under the loads of 40, 80, and 120 N are 0.29, 0.31, and 0.49, respectively. The WC grains are pulled out of the coating during the sliding wear test, but the coating maintains its integrity, suggesting that the coating is intact and continuously protects the substrate from wearing.

Diffusion of Magnetized Binary Ionic Mixtures at Ultracold Plasma Conditions

NASA Astrophysics Data System (ADS)

Vidal, Keith R.; Baalrud, Scott D.

2017-10-01

Ultracold plasma experiments offer an accessible means to test transport theories for strongly coupled systems. Application of an external magnetic field might further increase their utility by inhibiting heating mechanisms of ions and electrons and increasing the temperature at which strong coupling effects are observed. We present results focused on developing and validating a transport theory to describe binary ionic mixtures across a wide range of coupling and magnetization strengths relevant to ultracold plasma experiments. The transport theory is an extension of the Effective Potential Theory (EPT), which has been shown to accurately model correlation effects at these conditions, to include magnetization. We focus on diffusion as it can be measured in ultracold plasma experiments. Using EPT within the framework of the Chapman-Enskog expansion, the parallel and perpendicular self and interdiffusion coefficients for binary ionic mixtures with varying mass ratios are calculated and are compared to molecular dynamics simulations. The theory is found to accurately extend Braginskii-like transport to stronger coupling, but to break down when the magnetization strength becomes large enough that the typical gyroradius is smaller than the interaction scale length. This material is based upon work supported by the Air Force Office of Scientific Research under Award Number FA9550-16-1-0221.

Tungsten Incorporation into Gallium Oxide: Crystal Structure, Surface and Interface Chemistry, Thermal Stability and Interdiffusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rubio, E. J.; Mates, T. E.; Manandhar, S.

Tungsten (W) incorporated gallium oxide (Ga2O3) (GWO) thin films were deposited by radio-frequency magnetron co-sputtering of W-metal and Ga2O3-ceramic targets. Films were produced by varying sputtering power applied to the W-target in order to achieve variable W-content (0-12 at%) into Ga2O3 while substrate temperature was kept constant at 500 °C. Chemical composition, chemical valence states, microstructure and crystal structure of as-deposited and annealed GWO films were evaluated as a function of W-content. The structural and chemical analyses indicate that the samples deposited without any W-incorporation are stoichiometric, nanocrystalline Ga2O3 films, which crystallize in β-phase monoclinic structure. While GWO films alsomore » crystallize in monoclinic β-Ga2O3 phase, W-incorporation induces surface amorphization as revealed by structural studies. The chemical valence state of Ga ions probed by X-ray photoelectron spectroscopic (XPS) analyses is characterized by the highest oxidation state i.e., Ga3+. No changes in Ga chemical state are noted for variable W-incorporation in the range of 0-12 at%. Rutherford backscattering spectrometry (RBS) analyses indicate the uniform distribution of W-content in the GWO films. However, XPS analyses indicate the formation of mixed valence states for W ions, which may be responsible for surface amorphization in GWO films. GWO films were stable up to 900 oC, at which point thermally induced secondary phase (W-oxide) formation was observed. A transition to mesoporous structure coupled with W interdiffusion occurs due to thermal annealing as derived from the chemical analyses at the GWO films’ surface as well as depth-profiling towards the GWO-Si interface. A model has been formulated to account for the mechanism of W-incorporation, thermal stability and interdiffusion via pore formation in GWO films.« less

Interface effects in ultra-thin films: Magnetic and chemical properties

NASA Astrophysics Data System (ADS)

Park, Sungkyun

When the thickness of a magnetic layer is comparable to (or smaller than) the electron mean free path, the interface between magnetic and non-magnetic layers becomes very important factor to determine magnetic properties of the ultra-thin films. The quality of interface can enhance (or reduce) the desired properties. Several interesting physical phenomena were studied using these interface effects. The magnetic anisotropy of ultra-thin Co films is studied as function of non-magnetic underlayer thickness and non- magnetic overlayer materials using ex situ Brillouin light scattering (BLS). I observed that perpendicular magnetic anisotropy (PMA) increases with underlayer thickness and saturates after 5 ML. This saturation can be understood as a relaxation of the in-plane lattice parameter of Au(111) on top of Cu(111) to its bulk value. For the overlayer study, Cu, Al, and Au are used. An Au overlayer gives the largest PMA due to the largest in-plane lattice mismatch between Co and Au. An unusual effect was found by adding an additional layer on top of the Au overlayer. An additional Al capping layer on top of the Au overlayer reduces the PMA significantly. The possible explanation is that the misfit strain at the interface between the Al and the Au can be propagated through the Au layer to affect the magnetic properties of Co even though the in- plane lattice mismatch is less than 1%. Another interesting problem in interface interdiffusion and thermal stability in magnetic tunnel junction (MTJ) structures is studied using X-ray photoelectron spectroscopy (XPS). Since XPS is a very chemically sensitive technique, it allows us to monitor interface interdiffusion of the MTJ structures as-deposited and during post-deposition processing. For the plasma- oxidized samples, Fe only participates in the oxidation reduction process. In contrast to plasma-oxidized samples, there were no noticeable chemical shifts as- deposited and during post-deposition processing in air- oxidized samples. However, peak intensity variations were observed due to interface interdiffusion.

Characterization of Iridium Coated Rhenium Used in High-Temperature, Radiation-Cooled Rocket Thrusters

NASA Technical Reports Server (NTRS)

Stulen, R. H.; Boehme, D. R.; Clift, W. M.; McCarty, K. F.

1990-01-01

Materials used for radiation-cooled rocket thrusters must be capable of surviving under extreme conditions of high-temperatures and oxidizing environments. While combustion efficiency is optimized at high temperatures, many refractory metals are unsuitable for thruster applications due to rapid material loss from the formation of volatile oxides. This process occurs during thruster operation by reaction of the combustion products with the material surface. Aerojet Technical Systems has developed a thruster cone chamber constructed of Re coated with Ir on the inside surface where exposure to the rocket exhaust occurs. Re maintains its structural integrity at high temperature and the Ir coating is applied as an oxidation barrier. Ir also forms volatile oxide species (IrO2 and IrO3) but at a considerably slower rate than Re. In order to understand the performance limits of Ir-coated Re thrusters, we are investigating the interdiffusion and oxidation kinetics of Ir/Re. The formation of iridium and rhenium oxides has been monitored in situ by Raman spectroscopy during high temperature exposure to oxygen. For pure Ir, the growth of oxide films as thin as approximately 200 A could be easily detected and the formation of IrO2 was observed at temperatures as low as 600 C. Ir/Re diffusion test specimens were prepared by magnetron sputtering of Ir on Re substrates. Concentration profiles were determined by sputter Auger depth profiles of the heat treated specimens. Significant interdiffusion was observed at temperatures as low as 1000 C. Measurements of the activation energy suggest that below 1350 C, the dominant diffusion path is along defects, most likely grain boundaries, rather than bulk diffusion through the grains. The phases that form during interdiffusion have been examined by x ray diffraction. Analysis of heated test specimens indicates that the Ir-Re reaction produces a solid solution phase of Ir dissolved in the HCP structure of Re.

A review on the synthesis, crystal growth, structure and physical properties of rare earth based quaternary intermetallic compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mumbaraddi, Dundappa; Sarkar, Sumanta; Peter, Sebastian C., E-mail: sebastiancp@jncasr.ac.in

2016-04-15

This review highlights the synthesis and crystal growth of quaternary intermetallic compounds based on rare earth metals. In the first part of this review, we highlight briefly about intermetallics and their versatile properties in comparison to the constituent elements. In the next part, we have discussed about various synthesis techniques with more focus on the metal flux technique towards the well shaped crystal growth of novel compounds. In the subsequent parts, several disordered quaternary compounds have been reviewed and then outlined most known ordered quaternary compounds with their complex structure. A special attention has been given to the ordered compoundsmore » with structural description and relation to the parent binary and ternary compounds. The importance of electronic and structural feature is highlighted as the key roles in designing these materials for emerging applications. - Graphical abstract: Rare earth based quaternary intermetallic compounds crystallize in complex novel crystal structures. The diversity in the crystal structure may induce unique properties and can be considered them as future materials. - Highlights: • Crystal growth and crystal structure of quaternary rare earth based intermetallics. • Structural complexity of quaternary compounds in comparison to the parent compounds. • Novel quaternary compounds display unique crystal structure.« less

Gamma rays shielding parameters for white metal alloys

NASA Astrophysics Data System (ADS)

Kaur, Taranjot; Sharma, Jeewan; Singh, Tejbir

2018-05-01

In the present study, an attempt has been made to check the feasibility of white metal alloys as gamma rays shielding materials. Different combinations of cadmium, lead, tin and zinc were used to prepare quaternary alloys Pb60Sn20ZnxCd20-x (where x = 5, 10, 15) using melt quench technique. These alloys were also known as white metal alloys because of its shining appearance. The density of prepared alloys has been measured using Archimedes Principle. Gamma rays shielding parameters viz. mass attenuation coefficient (µm), effective atomic number (Zeff), electron density (Nel), Mean free path (mfp), Half value layer (HVL) and Tenth value layer (TVL) has been evaluated for these alloys in the wide energy range from 1 keV to 100 GeV. The WinXCom software has been used for obtaining mass attenuation coefficient values for the prepared alloys in the given energy range. The effective atomic number (Zeff) has been assigned to prepared alloys using atomic to electronic cross section ratio method. Further, the variation of various shielding parameters with photon energy has been investigated for the prepared white metal alloys.

PRN 88-2: Clustering of Quaternary Ammonium Compounds

EPA Pesticide Factsheets

This Notice announces that EPA has clustered the Quaternary Ammonium Compounds into four groups for the purpose of testing chemicals to build a database that will support continued registration of the entire family of quaternary ammonium compounds

Ultrasensitive quantification of endogenous brassinosteroids in milligram fresh plant with a quaternary ammonium derivatization reagent by pipette-tip solid-phase extraction coupled with ultra-high-performance liquid chromatography tandem mass spectrometry.

PubMed

Deng, Ting; Wu, Dapeng; Duan, Chunfeng; Guan, Yafeng

2016-07-22

Determination of endogenous brassinosteroids (BRs) in limited sample amount is vital to elucidating their tissue- and even local tissue-specific signaling pathway and physiological effects on plant growth and development. In this work, an ultra-sensitive quantification method was established for endogenous BRs in milligram fresh plant by using pipette-tip solid-phase extraction coupled with ultra-performance liquid chromatography tandem mass spectrometry (PT-SPE-UPLC-MS/MS), in which a quaternary ammonium phenyl boronic acid, 4-borono-N,N,N-trimethylbenzenaminium iodide (BTBA) was first developed for chemical derivatization of BRs. Due to the cationic quaternary ammonium group of BTBA, the ionization efficiencies of the BRs chelates with BTBA (BTBA-BRs) were enhanced by 1190-448785 times, which is the highest response enhancement factor among all derivatization reagents reported for BRs. In addition, PT-SPE packed with C18 sorbent was first used for purifying BRs from plant extracts, so the required sample amount was minimized, and recoveries higher than 91% were achieved. Under the optimized conditions, the minimal detectable amounts (MDA) of five target BRs were in the range of 27-94 amol, and the correlation coefficients (R(2)) were >0.9985 over four orders of magnitude. The relative recoveries of 75.8-104.9% were obtained with the intra- and inter-day relative standard deviations (RSDs) less than 18.7% and 19.6%, respectively. Finally, three BRs were successfully quantified in only 5mg fresh rice plant samples, and 24-epiBL can even be detected in only 0.5mg FW rice leaf segments. It is the first time that the BRs content in sub-milligram fresh plant sample has been quantified. Copyright © 2016 Elsevier B.V. All rights reserved.

Improvement of lipophilicity and membrane transport of cefuroxime using in vitro models.

PubMed

Mrestani, Yahya; Mrestani-Klaus, Carmen; Bretschneider, Beate; Neubert, Reinhard H H

2004-11-01

Most beta-lactam antibiotics cannot be absorbed orally and, therefore, must be administered intravenously (i.v.) or intramuscularly (i.m.). Because of the obvious drawbacks of drug delivery by injection, the development of alternatives with enhanced oral bioavailability is receiving much attention in pharmaceutical research. Cefuroxime exhibiting significant advantages in the parental treatment of common infections, was used as model drug in the present study. The effect of the cationic absorption enhancers (four quaternary ammonium salts) on the lipophilicity of cefuroxime was investigated by means of the n-octanol/water system. The results on partitioning coefficients in the n-octanol/buffer system were confirmed using an in vitro transport model with artificial (dodecanol collodium membrane) and biological membranes (Charles-River guinea pig).

OMVPE Growth of Quaternary (Al,Ga,In)N for UV Optoelectronics (title change from A)

DOE Office of Scientific and Technical Information (OSTI.GOV)

HAN,JUNG; FIGIEL,JEFFREY J.; PETERSEN,GARY A.

We report the growth and characterization of quaternary AlGaInN. A combination of photoluminescence (PL), high-resolution x-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) characterizations enables us to explore the contours of constant PL peak energy and lattice parameter as functions of the quaternary compositions. The observation of room temperature PL emission at 351nm (with 20% Al and 5% In) renders initial evidence that the quaternary could be used to provide confinement for GaInN (and possibly GaN). AlGaInN/GrdnN MQW heterostructures have been grown; both XRD and PL measurements suggest the possibility of incorporating this quaternary into optoelectronic devices.

Database and Map of Quaternary Faults and Folds in Peru and its Offshore Region

USGS Publications Warehouse

Machare, Jose; Fenton, Clark H.; Machette, Michael N.; Lavenu, Alain; Costa, Carlos; Dart, Richard L.

2003-01-01

This publication consists of a main map of Quaternary faults and fiolds of Peru, a table of Quaternary fault data, a region inset map showing relative plate motion, and a second inset map of an enlarged area of interest in southern Peru. These maps and data compilation show evidence for activity of Quaternary faults and folds in Peru and its offshore regions of the Pacific Ocean. The maps show the locations, ages, and activity rates of major earthquake-related features such as faults and fault-related folds. These data are accompanied by text databases that describe these features and document current information on their activity in the Quaternary.

Quaternary Geologic Map of Connecticut and Long Island Sound Basin

USGS Publications Warehouse

Stone, Janet Radway; Schafer, John P.; London, Elizabeth Haley; DiGiacomo-Cohen, Mary L.; Lewis, Ralph S.; Thompson, Woodrow B.

2005-01-01

The Quaternary geologic map (sheet 1) and explanatory figures and cross sections (sheet 2) portray the geologic features formed in Connecticut during the Quaternary Period, which includes the Pleistocene (glacial) and Holocene (postglacial) Epochs. The Quaternary Period has been a time of development of many details of the landscape and of all the surficial deposits. At least twice in the late Pleistocene, continental ice sheets swept across Connecticut. Their effects are of pervasive importance to the present occupants of the land. The Quaternary geologic map illustrates the geologic history and the distribution of depositional environments during the emplacement of glacial and postglacial surficial deposits and the landforms resulting from those events.

Formation of a bioconjugate composed of hemin, smectite, and quaternary ammonium chloride that is soluble and active in hydrophobic media.

PubMed

Kurosawa, Masaru; Itoh, Tetsuji; Kodera, Yoh; Matsushima, Ayako; Hiroto, Misao; Nishimura, Hiroyuki; Inada, Yuji

2002-01-01

Hemin (Fe(3+)) was adsorbed onto synthetic smectite (clay mineral) intercalated with a quaternary alkenylammonium compound, dioleyldimethylammonium chloride (DOA), to form a hemin-smectite-DOA conjugate. The hemin-smectite-DOA conjugate was soluble in organic solvents such as benzene and toluene to form a transparent colloidal solution with a light yellow color. Its absorption spectrum in benzene showed two bands, 600 and 568 nm, in the visible region and a sharp Soret band at 400 nm with the molar extinction coefficient of 7.5 x 10(4) M(-1) cm(-1). The formation of the conjugate of smectite and DOA was confirmed by X-ray diffraction analysis: the basal spacing, d(001), of hemin-smectite-DOA conjugate was 19 A which is an expansion of the interlayer space by 5 A based upon the basal spacing of smectite of 14 A. Hemin-smectite-DOA conjugate catalyzed the peroxidase-like reaction in organic solvents using benzoyl peroxide as the hydrogen acceptor and leucocrystal violet as the hydrogen donor. The temperature-dependent peroxidase-like activity of the conjugate was compared with peroxidase activity of horseradish peroxidase. The hemin-smectite-DOA conjugate exhibited higher activity as the temperature was increased from 30 to 70 degrees C, while horseradish peroxidase activity was reduced as the temperature was increased.

Synthesis and anticoagulant activity of the quaternary ammonium chitosan sulfates.

PubMed

Fan, Lihong; Wu, Penghui; Zhang, Jinrong; Gao, Song; Wang, Libo; Li, Mingjia; Sha, Mingming; Xie, Weiguo; Nie, Min

2012-01-01

Quaternary ammonium chitosan sulfates with diverse degrees of substitution (DS) ascribed to sulfate groups between 0.52 and 1.55 were synthesized by reacting quaternary ammonium chitosan with an uncommon sulfating agent (N(SO(3)Na)(3)) that was prepared from sodium bisulfite (NaHSO(3)) through reaction with sodium nitrite (NaNO(2)) in the aqueous system homogeneous. The structures of the derivatives were characterized by FTIR, (1)H NMR and (13)C NMR. The factors affecting DS of quaternary ammonium chitosan sulfates which included the molar ratio of NaNO(2) to quaternary ammonium chitosan, sulfated temperature, sulfated time and pH of sulfated reaction solution were investigated in detail. Its anticoagulation activity in vitro was determined by an activated partial thromboplastin time (APTT) assay, a thrombin time (TT) assay and a prothrombin time (PT) assay. Results of anticoagulation assays showed quaternary ammonium chitosan sulfates significantly prolonged APTT and TT, but not PT, and demonstrated that the introduction of sulfate groups into the quaternary ammonium chitosan structure improved its anticoagulant activity obviously. The study showed its anticoagulant properties strongly depended on its DS, concentration and molecular weight. Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.

Antimicrobial Polymeric Materials with Quaternary Ammonium and Phosphonium Salts

PubMed Central

Xue, Yan; Xiao, Huining; Zhang, Yi

2015-01-01

Polymeric materials containing quaternary ammonium and/or phosphonium salts have been extensively studied and applied to a variety of antimicrobial-relevant areas. With various architectures, polymeric quaternary ammonium/phosphonium salts were prepared using different approaches, exhibiting different antimicrobial activities and potential applications. This review focuses on the state of the art of antimicrobial polymers with quaternary ammonium/phosphonium salts. In particular, it discusses the structure and synthesis method, mechanisms of antimicrobial action, and the comparison of antimicrobial performance between these two kinds of polymers. PMID:25667977

Mapping Neogene and Quaternary sedimentary deposits in northeastern Brazil by integrating geophysics, remote sensing and geological field data

NASA Astrophysics Data System (ADS)

Andrades-Filho, Clódis de Oliveira; Rossetti, Dilce de Fátima; Bezerra, Francisco Hilario Rego; Medeiros, Walter Eugênio; Valeriano, Márcio de Morisson; Cremon, Édipo Henrique; Oliveira, Roberto Gusmão de

2014-12-01

Neogene and late Quaternary sedimentary deposits corresponding respectively to the Barreiras Formation and Post-Barreiras Sediments are abundant along the Brazilian coast. Such deposits are valuable for reconstructing sea level fluctuations and recording tectonic reactivation along the passive margin of South America. Despite this relevance, much effort remains to be invested in discriminating these units in their various areas of occurrence. The main objective of this work is to develop and test a new methodology for semi-automated mapping of Neogene and late Quaternary sedimentary deposits in northeastern Brazil integrating geophysical and remote sensing data. The central onshore Paraíba Basin was selected due to the recent availability of a detailed map based on the integration of surface and subsurface geological data. We used airborne gamma-ray spectrometry (i.e., potassium-K and thorium-Th concentration) and morphometric data (i.e., relief-dissection, slope and elevation) extracted from the digital elevation model (DEM) generated by the Shuttle Radar Topography Mission (SRTM). The procedures included: (a) data integration using geographic information systems (GIS); (b) exploratory statistical analyses, including the definition of parameters and thresholds for class discrimination for a set of sample plots; and (c) development and application of a decision-tree classification. Data validation was based on: (i) statistical analysis of geochemical and airborne gamma-ray spectrometry data consisting of K and Th concentrations; and (ii) map validation with the support of a confusion matrix, overall accuracy, as well as quantity disagreement and allocation disagreement for accuracy assessment based on field points. The concentration of K successfully separated the sedimentary units of the basin from Precambrian basement rocks. The relief-dissection morphometric variable allowed the discrimination between the Barreiras Formation and the Post-Barreiras Sediments. In addition, two units of the latter (i.e., PB1 and PB2) previously mapped in the field were promptly separated based on Th concentration. A regression analysis indicated that the relationship between geophysical and geochemical values obtained for the PB1, PB2 and Barreiras Formation is significant (R-squared = 0.91; p-value <0.05). Map validation presented a high overall accuracy of 84%, with a coefficient of quantity disagreement of 12% and a coefficient of allocation disagreement of 8%. These results indicate that the methodology applied in the central onshore Paraíba Basin can be successfully used for mapping the Barreiras Formation and Post-Barreiras Sediments in other areas of the Brazilian coast. The ability to rapidly and precisely map these units using such methodology could reveal their geographic distribution along the northeastern coast of Brazil.

The role of Quaternary environmental change in plant macroevolution: the exception or the rule?

PubMed Central

Willis, Katherine J; Niklas, Karl J

2004-01-01

The Quaternary has been described as an important time for genetic diversification and speciation. This is based on the premise that Quaternary climatic conditions fostered the isolation of populations and, in some instances, allopatric speciation. However, the 'Quaternary Ice-Age speciation model' rests on two key assumptions: (i) that biotic responses to climate change during the Quaternary were significantly different from those of other periods in Earth's history; and (ii) that the mechanisms of isolation during the Quaternary were sufficient in time and space for genetic diversification to foster speciation. These assumptions are addressed by examining the plant fossil record for the Quaternary (in detail) and for the past 410 Myr, which encompasses previous intervals of icehouse Earth. Our examination of the Quaternary record indicates that floristic responses to climate changes during the past 1.8 Myr were complex and that a distinction has to be made between those plants that were able to withstand the extremes of glacial conditions and those that could not. Generation times are also important as are different growth forms (e.g. herbaceous annuals and arborescent perennials), resulting in different responses in terms of genetic divergence rates during isolation. Because of these variations in the duration of isolation of populations and genomic diversification rates, no canonical statement about the predominant floristic response to climatic changes during the Quaternary (i.e. elevated rates of speciation or extinction, or stasis) is currently possible. This is especially true because of a sampling bias in terms of the fossil record of tree species over that of species with non-arborescent growth forms. Nevertheless, based on the available information, it appears that the dominant response of arborescent species during the Quaternary was extinction rather than speciation or stasis. By contrast, our examination of the fossil record of vascular plants for the past 410 Myr indicates that speciation rates often increased during long intervals of icehouse Earth (spanning up to 50 Myr). Therefore, longer periods of icehouse Earth than those occurring during the Quaternary may have isolated plant populations for sufficiently long periods of time to foster genomic diversification and allopatric speciation. Our results highlight the need for more detailed study of the fossil record in terms of finer temporal and spatial resolution than is currently available to examine the significance of intervals of icehouse Earth. It is equally clear that additional and detailed molecular studies of extant populations of Quaternary species are required in order to determine the extent to which these 'relic' species have genomically diversified across their current populations. PMID:15101573

Enhanced calculation of eigen-stress field and elastic energy in atomistic interdiffusion of alloys

NASA Astrophysics Data System (ADS)

Cecilia, José M.; Hernández-Díaz, A. M.; Castrillo, Pedro; Jiménez-Alonso, J. F.

2017-02-01

The structural evolution of alloys is affected by the elastic energy associated to eigen-stress fields. However, efficient calculations of the elastic energy in evolving geometries are actually a great challenge in promising atomistic simulation techniques such as Kinetic Monte Carlo (KMC) methods. In this paper, we report two complementary algorithms to calculate the eigen-stress field by linear superposition (a.k.a. LSA, Lineal Superposition Algorithm) and the elastic energy modification in atomistic interdiffusion of alloys (the Atom Exchange Elastic Energy Evaluation (AE4) Algorithm). LSA is shown to be appropriated for fast incremental stress calculation in highly nanostructured materials, whereas AE4 provides the required input for KMC and, additionally, it can be used to evaluate the accuracy of the eigen-stress field calculated by LSA. Consequently, they are suitable to be used on-the-fly with KMC. Both algorithms are massively parallel by their definition and thus well-suited for their parallelization on modern Graphics Processing Units (GPUs). Our computational studies confirm that we can obtain significant improvements compared to conventional Finite Element Methods, and the utilization of GPUs opens up new possibilities for the development of these methods in atomistic simulation of materials.

Reassessment of Atomic Mobilities in fcc Cu-Ag-Sn System Aiming at Establishment of an Atomic Mobility Database in Sn-Ag-Cu-In-Sb-Bi-Pb Solder Alloys

NASA Astrophysics Data System (ADS)

Xu, Huixia; Zhang, Lijun; Cheng, Kaiming; Chen, Weimin; Du, Yong

2017-04-01

To establish an accurate atomic mobility database in solder alloys, a reassessment of atomic mobilities in the fcc (face centered cubic) Cu-Ag-Sn system was performed as reported in the present work. The work entailed initial preparation of three fcc Cu-Sn diffusion couples, which were used to determine the composition-dependent interdiffusivities at 873 K, 923 K, and 973 K, to validate the literature data and provide new experimental data at low temperatures. Then, atomic mobilities in three boundary binaries, fcc Cu-Sn, fcc Ag-Sn, and fcc Cu-Ag, were updated based on the data for various experimental diffusivities obtained from the literature and the present work, together with the available thermodynamic database for solder alloys. Finally, based on the large number of interdiffusivities recently measured from the present authors, atomic mobilities in the fcc Cu-Ag-Sn ternary system were carefully evaluated. A comprehensive comparison between various calculated/model-predicted diffusion properties and the experimental data was used to validate the reliability of the obtained atomic mobilities in ternary fcc Cu-Ag-Sn alloys.

Tailoring characteristic thermal stability of Ni-Au binary nanocrystals via structure and composition engineering: theoretical insights into structural evolution and atomic inter-diffusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Bangquan; Wang, Hailong; Xing, Guozhong

We report on the structural evolution and atomic inter-diffusion characteristics of the bimetallic Ni-Au nanocrystals (NCs) by molecular dynamics simulations studies. Our results reveal that the thermal stability dynamics of Ni-Au NCs strongly depends on the atomic configurations. By engineering the structural construction with Ni:Au = 1:1 atomic composition, compared with core-shell Au@Ni and alloy NCs, the melting point of core-shell Ni@Au NCs is significantly enhanced up to 1215 K. Unexpectedly, with atomic ratio of Au:Ni= 1:9, the melting process initiates from the atoms in the shell of Ni@Au and alloy NCs, while starts from the core of Au@Ni NCs.more » The corresponding features and evolution process of structural motifs, mixing and segregation are illustrated via a series of dynamic simulations videos. Moreover, our results revealed that the face centered cubic phase Au{sub 0.75}Ni{sub 0.25} favorably stabilizes in NCs form but does not exist in the bulk counterpart, which elucidates the anomalies of previously reported experimental results on such bimetallic NCs.« less

Electronic structure of uranium overlayers on magnesium and aluminium

NASA Astrophysics Data System (ADS)

Gouder, T.

1997-06-01

We studied U overlayers on polycrystalline Mg and Al by X-ray and ultra-violet photoelectron spectroscopies (XPS and UPS, respectively), and compared the mode of growth and the evolution of the electronic structure as a function of coverage. The goal of this work was to detect localization, or at least correlation effects, in U overlayers and U substrate near surface alloys, which were expected to occur because of the reduced U 5f bandwidth in these systems. On Mg, U deposits as a pure overlayer without any interdiffusion, while on Al spontaneous interdiffusion takes place. The U 4f spectra of {U}/{Mg} show only weak correlation satellites. Nevertheless, the asymmetrical shape of the U 4f peak indicates 5f band narrowing. On Al, strong correlation satellites are observed in addition to plasmon loss features. It seems that U-substrate interactions promote correlation effects, while the reduced coordination in overlayers plays a less important role. UPS valence-band (VB) spectra of the two systems look remarkably similar. They do not show any correlation satellites. With decreasing overlayer thickness the 5f peak narrows, which is attributed to 5f band narrowing at the surface.

The Microstructural Evolution of Vacuum Brazed 1Cr18Ni9Ti Using Various Filler Metals

PubMed Central

Chen, Yunxia; Cui, Haichao; Lu, Binfeng; Lu, Fenggui

2017-01-01

The microstructures and weldability of a brazed joint of 1Cr18Ni9Ti austenitic stainless steel with BNi-2, BNi82CrSiBFe and BMn50NiCuCrCo filler metals in vacuum were investigated. It can be observed that an interdiffusion region existed between the filler metal and the base metal for the brazed joint of Ni-based filler metals. The width of the interdiffusion region was about 10 μm, and the microstructure of the brazed joint of BNi-2 filler metal was dense and free of obvious defects. In the case of the brazed joint of BMn50NiCuCrCo filler metal, there were pits, pores and crack defects in the brazing joint due to insufficient wettability of the filler metal. Crack defects can also be observed in the brazed joint of BNi82CrSiBFe filler metal. Compared with BMn50NiCuCrCo and BNi82CrSiBFe filler metals, BNi-2 filler metal is the best material for 1Cr18Ni9Ti austenitic stainless steel vacuum brazing because of its distinct weldability. PMID:28772745

The isothermal-oxidation behavior of several nickel-base single-crystal superalloys with and without coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goebel, M.; Rahmel, A.; Schuetze, M.

1993-04-01

Several commercial single-crystal superalloys (CMSX-2, CMSX-3, CMSX-4, CMSX-6, SRR 99) and some laboratory versions of one of them (CMSX-4) with various Y-additions were investigated concerning their oxidation resistance in air at temperatures between 800 and 1,200[degrees]C. The investigations also included two materials (CMSX-6, SRR 99) with an RT-22 coating. Weight change was recorded for times of up to 1,000 hr (in some cases up to 1,600 hr). Oxidized coatings and substrates were characterized by metallography, SEM, and microprobe analysis. Most of the alloys showed good oxidation resistance up to 1,000[degrees]C, while there was complete spalling during cooling after oxidation atmore » 1,150[degrees]C and 1,200[degrees]C for the uncoated and Y-free alloys. Coated alloys were superior, however the best behavior was shown by a laboratory version of CMSX-4 containing between 10 and 60 ppm Y. Interdiffusion at 1,000[degrees]C is tolerable for the coated alloys, but there was extremely rapid degradation of the coating by interdiffusion at 1,200[degrees]C. 20 refs., 26 figs., 6 tabs.« less

Influences of Indium Tin Oxide Layer on the Properties of RF Magnetron-Sputtered (BaSr)TiO3 Thin Films on Indium Tin Oxide-Coated Glass Substrate

NASA Astrophysics Data System (ADS)

Kim, Tae Song; Oh, Myung Hwan; Kim, Chong Hee

1993-06-01

Nearly stoichiometric ((Ba+Sr)/Ti=1.08-1.09) and optically transparent (BaSr)TiO3 thin films were deposited on an indium tin oxide (ITO)-coated glass substrate by means of rf magnetron sputtering for their application to the insulating layer of an electroluminescent flat panel display. The influence of the ITO layer on the properties of (BaSr)TiO3 thin films deposited on the ITO-coated substrate was investigated. The ITO layer did not affect the crystallographic orientation of (BaSr)TiO3 thin film, but enhanced the grain growth. Another effect of the ITO layer on (BaSr)TiO3 thin films was the interdiffusion phenomenon, which was studied by means of secondary ion mass spectrometry (SIMS). As the substrate temperature increased, interdiffusion intensified at the interface not only between the grown film and ITO layer but also between the ITO layer and base glass substrate. The refractive index (nf) of (BaSr)TiO3 thin film deposited on a bare glass substrate was 2.138-2.286, as a function of substrate temperature.

SE Great Basin Play Fairway Analysis

DOE Data Explorer

Adam Brandt

2015-11-15

Within this submission are multiple .tif images with accompanying metadata of magnetotelluric conductor occurrence, fault critical stress composite risk segment (CRS), permeability CRS, Quaternary mafic extrusions, Quaternary fault density, and Quaternary rhyolite maps. Each of these contributed to a final play fairway analysis (PFA) for the SE Great Basin study area.

Attitudes, perceptions and awareness concerning quaternary prevention among family doctors working in the Social Security System, Peru: a cross-sectional descriptive study.

PubMed

Cuba Fuentes, María Sofía; Zegarra Zamalloa, Carlos Orlando; Reichert, Sonja; Gill, Dawn

2016-04-27

Quaternary Prevention is defined as the action taken to identify patients at risk of overtreatment, to protect them from additional medical treatments, and to suggest interventions that are ethically acceptable. Many countries and organizations have joined in the efforts to practice quaternary prevention. These countries started a campaign called Choosing Wisely that implements recommendations in order to avoid harming patients. To determine the attitudes, perceptions and awareness towards Quaternary Prevention and the practice of “Choosing Wisely Canada Recommendations” among family doctors working in the Social Security System in Peru. A questionnaire was developed after reviewing the literature and contacting experts in the field and was sent by email to all 64 family physicians in the Social Security System (Essalud) in Lima Peru. Responses were received from 40 participants. The response rate was 64%. Approximately 95% reported that they understand the concept of quaternary prevention. Agreement with all the recommendations was 90% or higher. In most of the recommendations the applicability was more than 80%. The most important barriers perceived for the practice of Quaternary Prevention were patients’ expectations (33%). There are positive perceptions towards Quaternary Preventions and Choosing Wisely recommendations in the family doctors of social security in Lima Peru.

Recent Progress on the Stereoselective Synthesis of Cyclic Quaternary α-Amino Acids

PubMed Central

Cativiela, Carlos; Ordóñez, Mario

2010-01-01

The most recent papers describing the stereoselective synthesis of cyclic quaternary α-amino acids are collected in this review. The diverse synthetic approaches are classified according to the size of the ring and taking into account the bond that is formed to complete the quaternary skeleton. PMID:20300486

The ichthyofauna of limnic systems in Quaternary deposits of extreme southern Brazil

PubMed Central

Assumpção, Cindy M.; Quintela, Fernando M.; Corrêa, Fabiano; Loebmann, Daniel

2016-01-01

Abstract The Quaternary in the state of Rio Grande do Sul (RS), southern Brazil, is geologically represented by the coastal plain and was originated by successive events of Pleistocene-Holocene marine transgressions and the occurrence of alluvial deposits. This paper aimed to characterize the fish assemblage occurring in a swampy Quaternary area adjacent to Lagoa Pequena, a lacustrine system connected to the west margin of the Laguna dos Patos estuary. A checklist is also provided of the ichthyofauna so far recorded in limnic systems of Quaternary deposits in the state of Rio Grande do Sul. A total of 42 species was recorded, distributed in nine orders, 18 families and 31 genera. Characidae and Cichlidae were the most representative families, comprising 15 and 4 species respectively. A bibliographic revision associated to our sample data revealed the occurrence of 156 species in limnic systems inserted in RS Quaternary deposits (114 limnic, 15 marine/estuarine/limnic, ten marine/estuarine, nine estuarine/limnic and eight marine). Characiformes and Siluriformes are the most diverse orders, corroborating the Neotropical pattern. Seven species can be considered endemic to RS Quaternary deposits. PMID:28174498

Analysis of multiple quaternary ammonium compounds in the brain using tandem capillary column separation and high resolution mass spectrometric detection.

PubMed

Falasca, Sara; Petruzziello, Filomena; Kretz, Robert; Rainer, Gregor; Zhang, Xiaozhe

2012-06-08

Endogenous quaternary ammonium compounds are involved in various physiological processes in the central nervous system. In the present study, eleven quaternary ammonium compounds, including acetylcholine, choline, carnitine, acetylcarnitine and seven other acylcarnitines of low polarity, were analyzed from brain extracts using a two dimension capillary liquid chromatography-Fourier transform mass spectrometry method. To deal with their large difference in hydrophobicities, tandem coupling between reversed phase and hydrophilic interaction chromatography columns was used to separate all the targeted quaternary ammonium compounds. Using high accuracy mass spectrometry in selected ion monitoring mode, all the compounds could be detected from each brain sample with high selectivity. The developed method was applied for the relative quantification of these quaternary ammonium compounds in three different brain regions of tree shrews: prefrontal cortex, striatum, and hippocampus. The comparative analysis showed that quaternary ammonium compounds were differentially distributed across the three brain areas. The analytical method proved to be highly sensitive and reliable for simultaneous determination of all the targeted analytes from brain samples. Copyright © 2012 Elsevier B.V. All rights reserved.

Origin and late quaternary tectonism of a western Canadian continental shelf trough

NASA Astrophysics Data System (ADS)

Moslow, Thomas F.; Luternauer, John L.; Rohr, Kristin

1991-08-01

Analyses of high resolution and multi-channel seismic profiles from the central continental shelf of western Canada ascribe a late Quaternary glacial origin to large-scale troughs. Along the margins of Moresby Trough, one of three large-scale cross-shelf bathymetric depressions in Queen Charlotte Sound, seismic profiles within Quaternary sediments show a divergence of reflectors, thickening and folding of seismic units, and concavity of reflectors suggestive of drag. Compactional subsidence, growth faulting, and compaction faulting are also observed. Fault traces commonly terminate below the seabed. Deformation of Quaternary sediments due to faulting is plastic in nature and maximum offset of reflectors is 2.5 m. The observed Quaternary deformation appears to be a product of rapid deposition, loading and subsidence of late Quaternary sediment, which is unrelated to seismic activity. In addition, Quaternary faulting was probably activated by post-glacial loading and isostatic rebound of consolidated Tertiary strata along the margins of continental shelf troughs. The presence of mass movement (slump or debris flow) deposits overlying lithified Tertiary strata along the flanks of Moresby Trough provides the only evidence of seismic activity in the study area. The lack of a mud drape over these deposits implies a late Holocene age for the timing of their emplacement. The Quaternary troughs are incised into Tertiary-aged sedimentary fill of the Queen Charlotte basin. Previous workers had interpreted seafloor escarpments paralleling the trough margins to indicate that the location of Moresby Trough was controlled by renewed or continued activity on Tertiary-aged faults. A multi-channel seismic line across Moresby Trough shows that such an escarpment on the seafloor does not correlate to faults either in the Tertiary basin fill or the underlying basement. Tertiary reflectors are continuous underneath Moresby Trough; the seafloor escarpment is an erosional feature and was not created by reactivation of Tertiary structures. Trough erosion and subsequent fill (up to 175 m thick) are entirely of Quaternary age.

Efficiency improvement of green light-emitting diodes by employing all-quaternary active region and electron-blocking layer

NASA Astrophysics Data System (ADS)

Usman, Muhammad; Saba, Kiran; Han, Dong-Pyo; Muhammad, Nazeer

2018-01-01

High efficiency of green GaAlInN-based light-emitting diode (LED) has been proposed with peak emission wavelength of ∼510 nm. By introducing quaternary quantum well (QW) along with the quaternary barrier (QB) and quaternary electron blocking layer (EBL) in a single structure, an efficiency droop reduction of up to 29% has been achieved in comparison to the conventional GaN-based LED. The proposed structure has significantly reduced electrostatic field in the active region. As a result, carrier leakage has been minimized and spontaneous emission rate has been doubled.

Quaternary complexes composed of plasmid DNA/protamine/fish sperm DNA/stearic acid grafted chitosan oligosaccharide micelles for gene delivery.

PubMed

Du, Yong-Zhong; Lu, Ping; Yuan, Hong; Zhou, Jian-Ping; Hu, Fu-Qiang

2011-01-01

Quaternary complexes with condensed core of plasmid DNA, protamine, fish sperm DNA and shell of stearic acid grafted chitosan oligosaccharide (CSO-SA), were prepared. The CSO-SA could self-assemble to form nano-sized micelles in aqueous solution and demonstrated excellent internalization ability of tumor cells. Dynamic light scattering (DLS) measurement and transmission electrostatic microscope (TEM) images showed that quaternary complexes had spherical shape with about 25 nm number average diameter, and the size of quaternary complexes was smaller than that of CSO-SA micelles and CSO-SA micelles/plasmid DNA binary complexes. The transfection efficiencies of quaternary complexes on HEK293 and MCF-7 cells increased with incubation time, and were significantly higher than that of CSO-SA micelles/plasmid DNA binary complexes. The optimal transfection efficiency of quaternary complexes on HEK293 and MCF-7 cells measured by flow cytometer after 96 h was 23.82% and 41.43%, respectively. Whereas, the transfection efficiency of Lipofectamine™ 2000 on HEK293 and MCF-7 cells after 96 h was 32.45% and 33.23%, respectively. The data of luciferease activity measurement showed that the optimal ratio of plasmid DNA:fish sperm DNA:protamine:CSO-SA was 1:1:5:5. The results indicated that the present quaternary complexes were potential non-viral gene delivery system. Copyright © 2010 Elsevier B.V. All rights reserved.

Layer Structure of a Refractory Multilayer Ti/Al Composite After Pressure Diffusion Welding

NASA Astrophysics Data System (ADS)

Karpov, M. I.; Korzhov, V. P.; Zheltyakova, I. S.

2016-05-01

A composite refractory material with layer structure obtained by the method of pressure diffusion welding of multilayer Ti/Al packets composed of Ti- and Al-foils is studied. The welding temperature of the packets does not exceed 1200 - 1250°C. A layer structure forms in the process of interdiffusion of titanium and aluminum during welding of the packets.

Plasmonic-Enhanced Catalysis

DTIC Science & Technology

2012-05-30

shifts that cannot be merely explained hydride formation. These unexpected LSPR shifts may be explained by Au/Pd interdiffusion or silicide formation...photocurrent on a chemically modified gold thin film of metal -semiconductor (TiO2) Schottky diodes. • Intrinsic correlation between the hot electron flow...reaction to study catalyst nanoparticles at the single particle level. As hydrogen gas dissociates and intercalates into Pd, Pd changes from a metal to

Article having an improved platinum-aluminum-hafnium protective coating

NASA Technical Reports Server (NTRS)

Nagaraj, Bangalore Aswatha (Inventor); Williams, Jeffrey Lawrence (Inventor)

2005-01-01

An article protected by a protective coating has a substrate and a protective coating having an outer layer deposited upon the substrate surface and a diffusion zone formed by interdiffusion of the outer layer and the substrate. The protective coating includes platinum, aluminum, no more than about 2 weight percent hafnium, and substantially no silicon. The outer layer is substantially a single phase.

Sub-micrometer yttrium iron garnet LPE films with low ferromagnetic resonance losses

NASA Astrophysics Data System (ADS)

Dubs, Carsten; Surzhenko, Oleksii; Linke, Ralf; Danilewsky, Andreas; Brückner, Uwe; Dellith, Jan

2017-05-01

Using a liquid phase epitaxy (LPE) technique (1 1 1) yttrium iron garnet (YIG) films with thicknesses of  ≈100 nm and surface roughnesses as low as 0.3 nm have been grown on (1 1 1) gadolinium gallium garnet (GGG) substrates as a basic material for spin-wave propagation experiments in microstructured waveguides. The continuously strained films exhibit nearly perfect crystallinity without significant mosaicity and with effective lattice misfits of Δ {{a}\\bot}/{{a}s}≈ {{10}-4} and below. The film/substrate interface is extremely sharp without broad interdiffusion layer formation. All LPE films exhibit a nearly bulk-like saturation magnetization of (1800+/- 20 ) Gs and an ‘easy cone’ anisotropy type with extremely small in-plane coercive fields  <0.2 Oe. There is a rather weak in-plane magnetic anisotropy with a pronounced six-fold symmetry observed for the saturation field  <1.5 Oe. No significant out-of-plane anisotropy is observed, but a weak dependence of the effective magnetization on the lattice misfit is detected. The narrowest ferromagnetic resonance linewidth is determined to be 1.4 Oe @ 6.5 GHz which is the lowest value reported so far for YIG films of 100 nm thicknesses and below. The Gilbert damping coefficient for investigated LPE films is estimated to be close to 1× {{10}-4} .

Very large scale heterogeneous integration (VLSHI) and wafer-level vacuum packaging for infrared bolometer focal plane arrays

NASA Astrophysics Data System (ADS)

Forsberg, Fredrik; Roxhed, Niclas; Fischer, Andreas C.; Samel, Björn; Ericsson, Per; Hoivik, Nils; Lapadatu, Adriana; Bring, Martin; Kittilsland, Gjermund; Stemme, Göran; Niklaus, Frank

2013-09-01

Imaging in the long wavelength infrared (LWIR) range from 8 to 14 μm is an extremely useful tool for non-contact measurement and imaging of temperature in many industrial, automotive and security applications. However, the cost of the infrared (IR) imaging components has to be significantly reduced to make IR imaging a viable technology for many cost-sensitive applications. This paper demonstrates new and improved fabrication and packaging technologies for next-generation IR imaging detectors based on uncooled IR bolometer focal plane arrays. The proposed technologies include very large scale heterogeneous integration for combining high-performance, SiGe quantum-well bolometers with electronic integrated read-out circuits and CMOS compatible wafer-level vacuum packing. The fabrication and characterization of bolometers with a pitch of 25 μm × 25 μm that are arranged on read-out-wafers in arrays with 320 × 240 pixels are presented. The bolometers contain a multi-layer quantum well SiGe thermistor with a temperature coefficient of resistance of -3.0%/K. The proposed CMOS compatible wafer-level vacuum packaging technology uses Cu-Sn solid-liquid interdiffusion (SLID) bonding. The presented technologies are suitable for implementation in cost-efficient fabless business models with the potential to bring about the cost reduction needed to enable low-cost IR imaging products for industrial, security and automotive applications.

Alternatives for joining Si wafers to strain-accommodating Cu for high-power electronics

NASA Astrophysics Data System (ADS)

Faust, Nicholas; Messler, Robert W.; Khatri, Subhash

2001-10-01

Differences in the coefficients of thermal expansion (CTE) between silicon wafers and underlying copper electrodes have led to the use of purely mechanical dry pressure contacts for primary electrical and thermal connections in high-power solid-state electronic devices. These contacts are limited by their ability to dissipate I2R heat from within the device and by their thermal fatigue life. To increase heat dissipation and effectively deal with the CTE mismatch, metallurgical bonding of the silicon to a specially-structured, strain-accommodating copper electrode has been proposed. This study was intended to seek alternative methods for and demonstrate the feasibility of bonding Si to structured Cu in high-power solid-state devices. Three different but fundamentally related fluxless approaches identified and preliminarily assessed were: (1) conventional Sn-Ag eutectic solder; (2) a new, commercially-available active solder based on the Sn-Ag eutectic; and (3) solid-liquid interdiffusion bonding using the Au-In system. Metallurgical joints were made with varying quality levels (according to nonde-structive ultrasonic C-scan mapping, SEM, and electron microprobe) using each approach. Mechanical shear testing resulted in cohesive failure within the Si or the filler alloys. The best approach, in which eutectic Sn-Ag solder in pre-alloyed foil form was employed on Si and Cu substrates metallized (from the substrate outward) with Ti, Ni and Au, exhibited joint thermal conduction 74% better than dry pressure contacts.

Numerical simulation of plagioclase rim growth during magma ascent at Bezymianny Volcano, Kamchatka

NASA Astrophysics Data System (ADS)

Gorokhova, N. V.; Melnik, O. E.; Plechov, P. Yu.; Shcherbakov, V. D.

2013-08-01

Slow CaAl-NaSi interdiffusion in plagioclase crystals preserves chemical zoning of plagioclase in detail, which, along with strong dependence of anorthite content in plagioclase on melt composition, pressure, and temperature, make this mineral an important source of information on magma processes. A numerical model of zoned crystal growth is developed in the paper. The model is based on equations of multicomponent diffusion with diagonal cross-component diffusion terms and accounts for mass conservation on the melt-crystal interface and growth rate controlled by undercooling. The model is applied to the data of plagioclase rim zoning from several recent Bezymianny Volcano (Kamchatka) eruptions. We show that an equilibrium growth model cannot explain crystallization of naturally observed plagioclase during magma ascent. The developed non-equilibrium model reproduced natural plagioclase zoning and allowed magma ascent rates to be constrained. Matching of natural and simulated zoning suggests ascent from 100 to 50 MPa during 15-20 days. Magma ascent rate from 50 MPa to the surface varies from eruption to eruption: plagioclase zoning from the December 2006 eruption suggests ascent to the surface in less than 1 day, whereas plagioclase zoning from March 2000 and May 2007 eruptions are better explained by magma ascent over periods of more than 30 days). Based on comparison of diffusion coefficients for individual elements a mechanism of atomic diffusion during plagioclase crystallization is proposed.

Polarized Infrared Reflectance Studies of Quaternary In0.04Al0.06Ga0.90N

NASA Astrophysics Data System (ADS)

Bakhori, S. K. Mohd; Lee, S. C.; Ahmad, M. A.; Ng, S. S.; Hassan, H. Abu

2010-07-01

Group III-nitride has re-gained considerable interest recently as wide direct band gap semiconductor materials for opto-electronic and high power devices. The quaternary InAlGaN have great flexibility in tailoring their band gap profile while maintaining their lattice-matching and structural integrity. In this study, we report for the first time the polarized infrared (IR) reflectance studies of quaternary In0.04Al0.06Ga0.90N by using Fourier transform infrared spectroscopy of Perkin-Elmer. The quaternary In0.04Al0.06Ga0.90N epilayers was grown on sapphire by molecular beam epitaxy. The polarized IR reflectance spectra obtained at incident angle of 15° were then compared with modeling spectrum of damped harmonic oscillator. Through this study, the transverse and longitudinal optical phonon modes of quaternary In0.04Al0.06Ga0.90N epilayers were obtained.

Thermally Reduced Graphene Oxide Electrochemically Activated by Bis-Spiro Quaternary Alkyl Ammonium for Capacitors.

PubMed

He, Tieshi; Meng, Xiangling; Nie, Junping; Tong, Yujin; Cai, Kedi

2016-06-08

Thermally reduced graphene oxide (RGO) electrochemically activated by a quaternary alkyl ammonium-based organic electrolytes/activated carbon (AC) electrode asymmetric capacitor is proposed. The electrochemical activation process includes adsorption of anions into the pores of AC in the positive electrode and the interlayer intercalation of cations into RGO in the negative electrode under high potential (4.0 V). The EA process of RGO by quaternary alkyl ammonium was investigated by X-ray diffraction and electrochemical measurements, and the effects of cation size and structure were extensively evaluated. Intercalation by quaternary alkyl ammonium demonstrates a small degree of expansion of the whole crystal lattice (d002) and a large degree of expansion of the partial crystal lattice (d002) of RGO. RGO electrochemically activated by bis-spiro quaternary alkyl ammonium in propylene carbonate/AC asymmetric capacitor exhibits good activated efficiency, high specific capacity, and stable cyclability.

Multi-valued logic gates based on ballistic transport in quantum point contacts.

PubMed

Seo, M; Hong, C; Lee, S-Y; Choi, H K; Kim, N; Chung, Y; Umansky, V; Mahalu, D

2014-01-22

Multi-valued logic gates, which can handle quaternary numbers as inputs, are developed by exploiting the ballistic transport properties of quantum point contacts in series. The principle of a logic gate that finds the minimum of two quaternary number inputs is demonstrated. The device is scalable to allow multiple inputs, which makes it possible to find the minimum of multiple inputs in a single gate operation. Also, the principle of a half-adder for quaternary number inputs is demonstrated. First, an adder that adds up two quaternary numbers and outputs the sum of inputs is demonstrated. Second, a device to express the sum of the adder into two quaternary digits [Carry (first digit) and Sum (second digit)] is demonstrated. All the logic gates presented in this paper can in principle be extended to allow decimal number inputs with high quality QPCs.

Geology and ground-water resources of the Cockfield Formation in western Tennessee

USGS Publications Warehouse

Parks, W.S.; Carmichael, J.K.

1990-01-01

The Cockfield Formation of the Claiborne Group of Tertiary age underlies approximately 4,000 sq mi in western Tennessee. The formation consists primarily of lenticular beds of very fine to coarse sand, silt, clay, and lignite. The Cockfield Formation has been extensively eroded, and the original thickness is preserved only in a few areas where the formation ranges from 235 to 270 ft in thickness. Recharge to the Cockfield aquifer is from precipitation on sparse outcrops or by downward infiltration of water from the overlying fluvial deposits of Tertiary and Quaternary age and alluvium of Quaternary age or, where present, the overlying Jackson Formation of Tertiary age. Data from two observation wells indicate that water levels have risen at average rates of about 0.5 and 0.7 ft/year during the period 1980-85. Water from the Cockfield aquifer is a calcium bicarbonate type that contains low concentrations of most major constituents, and generally is suitable for most uses. Dissolved-solids concentrations range from 44 to 218 mg/L. Data from two aquifer tests indicate transmissivities of 2,500 and 6 ,000 sq ft/day and storage coefficients of 0.0003 and 0.0007, respectively. The Cockfield aquifer presently provides small to moderate quantities of water for several public and industrial water supplies and small quantities to numerous domestic and farm wells. Withdrawals for public and industrial supplies in 1983 averaged about 3.3 million gal/day. (USGS)

Analysis of La Dehesa paleo-landslide. Central Pre-Andes of Argentina

NASA Astrophysics Data System (ADS)

Tapia Baldis, Carla; Rothis, Luis Martín; Perucca, Laura; Esper Angillieri, María; Vargas, Horacio; Ponce, David; Allis, Carlos

2018-04-01

The main objective of this paper is to consider the influence of Quaternary faults as likely triggering factor for rockslides occurrence in the Central Pre-Andes, a region with intense shallow seismic activity. A rockslide deposit was selected as study case, placed in the western flank of La Dehesa and Talacasto (DT) range (31°3‧37″ S and 68°46‧ 8″ W). Applied methodology includes the characterization of main discontinuities, reconstruction of the topography using a high-resolution digital elevation model, safety factor calculation along the sliding surface and, Newmark displacements estimation for three different hypothetical seismic scenarios, recreated from existing neotectonic local information. Equilibrium-limit method's results confirm that study case, La Dehesa rockslide (LDR), had a stable and safe slope's configuration under static conditions. However, a seismic horizontal coefficient between 0.2 and 0.3 decreases safety factor below the safety threshold. Newmark's displacements for different seismic reconstructed scenarios varies between 4.1 and 15.9 cm, values that agreed with a coherent failure process, likely triggered by Pleistocene to Holocene seismogenic sources in Central Pre-Andes. LDR trigger could be assigned mainly to an earthquake related to La Dehesa Quaternary fault (LDF) activity; however, similar movements produced by neighboring faults should not be discarded. LDR triggering related to climatic conditions is despised. Finally, the methodology presented in this work is easy to reproduce and may be applied to other rockslides located in the mountainous areas of the Central Pre-Andes of Argentina.

Structural, electronic, magnetic, half-metallic, mechanical, and thermodynamic properties of the quaternary Heusler compound FeCrRuSi: A first-principles study.

PubMed

Wang, Xiaotian; Khachai, Houari; Khenata, Rabah; Yuan, Hongkuan; Wang, Liying; Wang, Wenhong; Bouhemadou, Abdelmadjid; Hao, Liyu; Dai, Xuefang; Guo, Ruikang; Liu, Guodong; Cheng, Zhenxiang

2017-11-23

In this paper, we have investigated the structural, electronic, magnetic, half-metallic, mechanical, and thermodynamic properties of the equiatomic quaternary Heusler (EQH) compound FeCrRuSi using the density functional theory (DFT) and the quasi-harmonic Debye model. Our results reveal that FeCrRuSi is a half-metallic material (HMM) with a total magnetic moment of 2.0 μ B in agreement with the well-known Slater-Pauling rule M t  = Z t  - 24. Furthermore, the origin of the half-metallic band gap in FeCrRuSi is well studied through a schematic diagram of the possible d-d hybridization between Fe, Cr and Ru elements. The half-metallic behavior of FeCrRuSi can be maintained in a relatively wide range of variations of the lattice constant (5.5-5.8 Å) under uniform strain and the c/a ratio (0.96-1.05) under tetragonal distortion. The calculated phonon dispersion, cohesive and formation energies, and mechanical properties reveal that FeCrRuSi is stable with an EQH structure. Importantly, the compound of interest has been prepared and is found to exist in an EQH type structure with the presence of some B2 disorder. Moreover, the thermodynamic properties, such as the thermal expansion coefficient α, the heat capacity C V , the Grüneisen constant γ, and the Debye temperature Θ D are calculated.

Deformation and Quaternary Faulting in Southeast Missouri across the Commerce Geophysical Lineament

USGS Publications Warehouse

Stephenson, W.J.; Odum, J.K.; Williams, R.A.; Pratt, T.L.; Harrison, R.W.; Hoffman, D.

1999-01-01

High-resolution seismic-reflection data acquired at three sites along the surface projection of the Commerce geophysical lineament in southeast Missouri reveal a complex history of post-Cretaceous faulting that has continued into the Quaternary. Near Qulin, Missouri, approximately 20 m of apparent vertical fault displacement has occurred in the Quaternary. Reflection data collected at Idalia Hill, about 45 km to the northeast, reveal a series of reverse and possibly right-lateral strike-slip faults with Quaternary displacement. In the Benton Hills, 45 km northeast of Idalia Hill, seismic data image a complicated series of anticlinal and synclinal fault-bounded blocks immediately north of the Commerce fault. We infer that most of the deformation imaged in the upper 400 m of these three data sets occurred since post-Cretaceous time, and a significant portion of it occurred during Quaternary time. Collectively, these seismic data along with geomorphic and surface-geologic evidence suggest (1) the existence of at least one potential seismogenic structure in southeastern Missouri outside the main zones of New Madrid seismicity, and (2) these structures have been active during the Quaternary. The geographic location of the imaged deformation suggests it is related to structures along with the Commerce geophysical lineament.

Versatile methods for synthesizing organic acid salts of quaternary berberine-type alkaloids as anti-ulcerative colitis agents.

PubMed

Zhang, Zhi-Hui; Li, Jing; Zhang, Hai-Jing; Deng, An-Jun; Wu, Lian-Qiu; Li, Zhi-Hong; Song, Hong-Rui; Wang, Wen-Jie; Qin, Hai-Lin

2016-06-01

Two versatile methods to synthesize kinds of organic acid salts of quaternary berberine-type alkaloids were investigated in order to determine which is more efficient to improve the liposolubility of the target compounds and to explore the efficacy of the target compounds as anti-ulcerative colitis (UC) agents. Overall evaluation according to the reaction results and yields of the final products indicated that the synthetic method using tertiary (±)-8-acylmethyldihydroberberine-type alkaloids as key intermediates is superior to that of using tertiary dihydroberberine-type alkaloids as intermediates. Ten target compounds were synthesized using quaternary berberine chloride and quaternary coptisine chloride as starting materials, respectively, and the anti-UC activity of some target compounds was evaluated in an in vitro x-box-binding protein 1 (XBP1) transcriptional activity assay using dual luciferase reporter detection. At 10 μM, the tested compounds were found to activate the transcription of XBP1 target at almost the same level as that of quaternary coptisine chloride. The synthesized target compounds were also found to share higher liposolubility than the inorganic acid salts of quaternary berberine-type alkaloid.

Quaternary extensional growth folding beneath Reno, Nevada, imaged by urban seismic profiling

USGS Publications Warehouse

Stephenson, William J.; Frary, Roxy N.; Louie, John; Odum, Jackson K.

2013-01-01

We characterize shallow subsurface faulting and basin structure along a transect through heavily urbanized Reno, Nevada, with high‐resolution seismic reflection imaging. The 6.8 km of P‐wave data image the subsurface to approximately 800 m depth and delineate two subbasins and basin uplift that are consistent with structure previously inferred from gravity modeling in this region of the northern Walker Lane. We interpret two primary faults that bound the uplift and deform Quaternary deposits. The dip of Quaternary and Tertiary strata in the western subbasin increases with greater depth to the east, suggesting recurrent fault motion across the westernmost of these faults. Deformation in the Quaternary section of the western subbasin is likely evidence of extensional growth folding at the edge of the Truckee River through Reno. This deformation is north of, and on trend with, previously mapped Quaternary fault strands of the Mt. Rose fault zone. In addition to corroborating the existence of previously inferred intrabasin structure, these data provide evidence for an active extensional Quaternary fault at a previously unknown location within the Truckee Meadows basin that furthers our understanding of both the seismotectonic framework and earthquake hazards in this urbanized region.

Sequential character of low-energy ternary and quaternary nuclear fission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kadmensky, S. G., E-mail: kadmensky@phys.vsu.ru; Bulychev, A. O.

2016-09-15

An analysis of low-energy true ternary (quaternary) nuclear fission leads to the conclusion that these fission modes have a sequential two-step (three-step) character such that the emission of a third particle (third and fourth particles) and the separation of fission fragments occur at distinctly different instants, in contrast to the simultaneous emergence of all fission products in the case of onestep ternary (quaternary) fission. This conclusion relies on the following arguments. First, the emission of a third particle (third and fourth particles) from a fissile nucleus is due to a nonevaporative mechanism associated with a nonadiabatic character of the collectivemore » deformation motion of this nucleus at the stages preceding its scission. Second, the axial symmetry of the deformed fissile compound nucleus and the direction of its symmetry axis both remain unchanged at all stages of ternary (quaternary) fission. This circumstancemakes it possible to explain themechanism of the appearance of observed anisotropies and T — odd asymmeries in the angular distributions of products of ternary (quaternary) nuclear fission. Third, the T —odd asymmetry discovered experimentally in ternary nuclear fission induced by cold polarized neutrons obeys the T —invariance condition only in the case of a sequential two-step (three-step) character of true ternary (quaternary) nuclear fission. At the same time, this asymmetry is not a T —invariant quantity in the case of the simultaneous emission of products of true ternary (quaternary) nuclear fission from the fissile compound nucleus.« less

Two-Oxide Disequilibrium: A New Geospeedometer Based on Diffusion in Ilmenite

NASA Astrophysics Data System (ADS)

Williams, K. B.; Krawczynski, M. J.; Van Orman, J. A.

2016-12-01

Diffusion-annealing experiments were conducted in a 0.5" piston cylinder apparatus to investigate diffusivity of Fe2+, Mg2+, and Mn2+ in ilmenite solid solutions between 800ºC and 1000ºC. Polycrystalline ilmenite (FeTiO3) was juxtaposed against either an oriented geikielite (MgTiO3) single crystal or polycrystalline Mn-bearing (5 mol% Mn) ilmenite, in a "diffusion-couple" geometry. Geikielite single crystals were synthesized at Los Alamos National Laboratory, cut into 1 mm edge-length cubes, and polished either perpendicular or parallel to the c-axis. Polycrystalline ilmenite starting materials were synthesized by mixing high purity reagent-grade oxides (FeO, MnO, and TiO2) and sintering in a piston cylinder apparatus, then cut into wafers and polished. Experimental run products were analyzed by electron microprobe at Washington University in St. Louis. Microprobe analyses were obtained perpendicularly across the diffusion interface for each experiment. Experimental diffusion profiles create smooth curves that, when fit with an error function, define Fe-Mg and Fe-Mn interdiffusion coefficients in ilmenite. The diffusion coefficients do not appear compositionally dependent, but do show significant anisotropy. Preliminary results suggest diffusion activation energies are lower in ilmenite than in titanomagnetite [1]. Ilmenite-titanomagnetite equilibria define pre-eruptive temperatures and oxygen fugacities. However, oxides often exist out of equilibrium [2]. We use the cation diffusion data for ilmenite and existing data on titanomagnetite to establish two-oxide disequilibrium as a geospeedometer. Our data constrain oxide-oxide re-equilibration timescales at Mt. Unzen to months, consistent with estimates from zoned, single crystals of magnetite [3,4]. Future experiments will examine the effect of oxygen fugacity on diffusivity in ilmenite solid solutions. References:[1] Van Orman & Crispin (2010) RiMG 72, 757-825.[2] Bacon & Hirschmann (1988) Am. Min. 73, 57-61.[3] Nakamura (1995) Geology 23, 807-810.[4] Venezky & Rutherford (1999) J. Volc. Geo. Res. 89, 213-230.

Improved method estimating bioconcentration/bioaccumulation factor from octanol/water partition coefficient

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meylan, W.M.; Howard, P.H.; Aronson, D.

1999-04-01

A compound`s bioconcentration factor (BDF) is the most commonly used indicator of its tendency to accumulate in aquatic organisms from the surrounding medium. Because it is expensive to measure, the BCF is generally estimated from the octanol/water partition coefficient (K{sub ow}), but currently used regression equations were developed from small data sets that do not adequately represent the wide range of chemical substances now subject to review. To develop and improved method, the authors collected BCF data in a file that contained information on measured BCFs and other key experimental details for 694 chemicals. Log BCF was then regressed againstmore » log K{sub ow} and chemicals with significant deviations from the line of best fit were analyzed by chemical structure. The resulting algorithm classifies a substance as either nonionic or ionic, the latter group including carboxylic acids, sulfonic acids and their salts, and quaternary N compounds. Log BCF for nonionics is estimated from log K{sub ow} and a series of correction factors if applicable; different equations apply for log K{sub ow} 1.0 to 7.0 and >7.0. For ionics, chemicals are categorized by log K{sub ow} and a log BCF in the range 0.5 to 1.75 is assigned. Organometallics, nonionics with long alkyl chains, and aromatic azo compounds receive special treatment. The correlation coefficient and mean error for log BCF indicate that the new method is a significantly better fit to existing data than other methods.« less

Development of Ag-Pd-Au-Cu alloy for multiple dental applications. Part 1. Effects of Pd and Cu contents, and addition of Ga or Sn on physical properties and bond with ultra-low fusing ceramic.

PubMed

Goto, S; Miyagawa, Y; Ogura, H

2000-09-01

Ag-Pd-Au-Cu quaternary alloys consisting of 30-50% Ag, 20-40% Pd, 10-20% Cu and 20% Au (mother alloys) were prepared. Then 5% Sn or 5% Ga was added to the mother alloy compositions, and another two alloy systems (Sn-added alloys and Ga-added alloys) were also prepared. The bond between the prepared alloys and an ultra-low fusing ceramic as well as their physical properties such as the solidus point, liquidus point and the coefficient of thermal expansion were evaluated. The solidus point and liquidus point of the prepared alloys ranged from 802 degrees C to 1142 degrees C and from 931 degrees C to 1223 degrees C, respectively. The coefficient of thermal expansion ranged from 14.6 to 17.1 x 10(-6)/degrees C for the Sn- and Ga-added alloys. In most cases, the Pd and Cu contents significantly influenced the solidus point, liquidus point and coefficient of thermal expansion. All Sn- and Ga-added alloys showed high area fractions of retained ceramic (92.1-100%), while the mother alloy showed relatively low area fractions (82.3%) with a high standard deviation (20.5%). Based on the evaluated properties, six Sn-added alloys and four Ga-added alloys among the prepared alloys were suitable for the application of the tested ultra-low fusing ceramic.

Phosphate-based glasses: Prediction of acoustical properties

NASA Astrophysics Data System (ADS)

El-Moneim, Amin Abd

2016-04-01

In this work, a comprehensive study has been carried out to predict the composition dependence of bulk modulus and ultrasonic attenuation coefficient in the phosphate-based glass systems PbO-P2O5, Li2O-TeO2-B2O3-P2O5, TiO2-Na2O-CaO-P2O5 and Cr2O3-doped Na2O-ZnO-P2O5 at room temperature. The prediction is based on (i) Makishima-Mackenzie theory, which correlates the bulk modulus with packing density and dissociation energy per unit volume, and (ii) Our recently presented semi-empirical formulas, which correlate the ultrasonic attenuation coefficient with the oxygen density, mean atomic ring size, first-order stretching force constant and experimental bulk modulus. Results revealed that our recently presented semi-empirical formulas can be applied successfully to predict changes of ultrasonic attenuation coefficient in binary PbO-P2O5 glasses at 10 MHz frequency and in quaternary Li2O-TeO2-B2O3-P2O5, TiO2-Na2O-CaO-P2O5 and Cr2O3-Na2O-ZnO-P2O5 glasses at 5 MHz frequency. Also, Makishima-Mackenzie theory appears to be valid for the studied glasses if the effect of the basic structural units that present in the glass network is taken into account.

Synthesis and Characterization of Perfluoro Quaternary Ammonium Anion Exchange Membranes

DTIC Science & Technology

2012-01-01

study, new alkaline exchange membranes were prepared from the perfluorinated 3M ionomer with various quaternary ammonium cations attached with...ammonium anion exchange membranes Report Title ABSTRACT In this study, new alkaline exchange membranes were prepared from the perfluorinated 3M ionomer...exchange membranes were prepared from the perfluorinated 3M ionomer with vari- ous quaternary ammonium cations attached with sulfonamide linkage. The

Self-Assembly of Helical Ribbons

DTIC Science & Technology

1999-07-01

detergent, a phosphatidylcholine or a fatty acid , and a steroid analog of cholesterol. In almost all systems, two different pitch types of helical...quater- nary sterol systems (QSS), on a quaternary fatty acid system (QFAS), and on two lipid concentrate systems, as defined below. In addition to high...lipid concentrate; QSS, quaternary sterol systems; QFAS, quaternary fatty acid system; NaTC, sodium taurocholate; DOPC, 1,2-dioleoyl-glycero- 3

Quaternary paleoceanography of the deep Arctic Ocean based on quantitative analysis of Ostracoda

USGS Publications Warehouse

Cronin, T. M.; Holtz, T.R.; Whatley, R.C.

1994-01-01

Ostracodes were studied from deep Arctic Ocean cores obtained during the Arctic 91 expedition of the Polarstern to the Nansen, Amundsen and Makarov Basins, the Lomonosov Ridge, Morris Jesup Rise and Yermak Plateau, in order to investigate their distribution in Arctic Ocean deep water (AODW) and apply these data to paleoceanographic reconstruction of bottom water masses during the Quaternary. Analyses of coretop assemblages from Arctic 91 boxcores indicate the following: ostracodes are common at all depths between 1000 and 4500 m, and species distribution is strongly influenced by water mass characteristics and bathymetry; quantitative analyses comparing Eurasian and Canada Basin assemblages indicate that distinct assemblages inhabit regions east and west of the Lomonosov Ridge, a barrier especially important to species living in lower AODW; deep Eurasian Basin assemblages are more similar to those living in Greenland Sea deep water (GSDW) than those in Canada Basin deep water; two upper AODW assemblages were recognized throughout the Arctic Ocean, one living between 1000 and 1500 m, and the other, having high species diversity, at 1500-3000 m. Downcore quantitative analyses of species' abundances and the squared chord distance coefficient of similarity reveals a distinct series of abundance peaks in key indicator taxa interpreted to signify the following late Quaternary deep water history of the Eurasian Basin. During the Last Glacial Maximum (LGM), a GSDW/AODW assemblage, characteristic of cold, well oxygenated deep water > 3000 m today, inhabited the Lomonosov Ridge to depths as shallow as 1000 m, perhaps indicating the influence of GSDW at mid-depths in the central Arctic Ocean. During Termination 1, a period of high organic productivity associated with a strong inflowing warm North Atlantic layer occurred. During the mid-Holocene, several key faunal events indicate a period of warming and/or enhanced flow between the Canada and Eurasian Basins. A long-term record of ostracode assemblages from kastenlot core PS2200-5 (1073 m water depth) from the Morris Jesup Rise indicates a quasi-cyclic pattern of water mass changes during the last 300 kyr. Interglacial ostracode assemblages corresponding to oxygen isotope stages 1, 5, and 7 indicate rapid changes in dissolved oxygen and productivity during glacial-interglacial transitions. ?? 1994.

Reactive Brazing of Carbon-Carbon Composites to Titanium

NASA Technical Reports Server (NTRS)

Shpargel, Tarah; Singh, M.; Morscher, Gregory; Asthana, Rajiv

2004-01-01

The Ti-metal/C-C composite joints were formed by reactive brazing with three commercial brazes, namely, Cu-ABA, TiCuNi, and TiCuSil. The joint microstructures were examined using optical microscopy, and scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS). The results of the microstructure analysis indicate solute redistribution across the joint and possible metallurgical bond formation via interdiffusion, which led to good wetting and spreading.

Viscosity and viscoelasticity of two-phase systems having diffuse interfaces

NASA Technical Reports Server (NTRS)

Hopper, R. W.

1976-01-01

The equilibrium stability criterion for diffuse interfaces in a two-component solution with a miscibility gap requires that the interdiffusion flux vanish. If the system is continuously deformed, convective fluxes disrupt the equilibrium in the interface regions and induce a counter diffusive flux, which is dissipative and contributes to the apparent viscosity of the mixture. Chemical free energy is recoverably stored, causing viscoelastic phenomena. Both effects are significant.

Void Formation during Diffusion - Two-Dimensional Approach

NASA Astrophysics Data System (ADS)

Wierzba, Bartek

2016-06-01

The final set of equations defining the interdiffusion process in solid state is presented. The model is supplemented by vacancy evolution equation. The competition between the Kirkendall shift, backstress effect and vacancy migration is considered. The proper diffusion flux based on the Nernst-Planck formula is proposed. As a result, the comparison of the experimental and calculated evolution of the void formation in the Fe-Pd diffusion couple is shown.

Active Metal Brazing of Carbon-Carbon Composites to Titanium

NASA Technical Reports Server (NTRS)

Singh, M.; Shpargel, T. P.; Morscher, G.; Asthana, R.

2004-01-01

The Ti-metal/C-C composite joints were formed by reactive brazing with three commercial brazes, namely, Cu-ABA, TiCuNi, and TiCuSil. The joint microstructures were examined using optical microscopy, and scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS). The results of the microstructure analysis indicate solute redistribution across the joint which led to good wetting, spreading, and metallurgical bond formation via interdiffusion.

Composite construction for nuclear fuel containers

DOEpatents

Cheng, Bo-Ching [Fremont, CA; Rosenbaum, Herman S [Fremont, CA; Armijo, Joseph S [Saratoga, CA

1987-01-01

An improved method for producing nuclear fuel containers of a composite construction having components providing therein a barrier system for resisting destructive action by volatile fission products or impurities and also interdiffusion of metal constituents, and the product thereof. The composite nuclear fuel containers of the method comprise a casing of zirconium or alloy thereof with a layer of copper overlying an oxidized surface portion of the zirconium or alloy thereof.

TEM and TED investigation of Ag/PbTe thin film bilayers.

NASA Astrophysics Data System (ADS)

Mandrino, Đorđe; Marinković, V.

Morphology and phase structure of Ag/PbTe thin film bilayers were investigated. This system was of particular interest because of interfacial reaction observed previously in an analogous Ag/SnTe system. Reaction products due to the interdiffusion of Ag with the substrate were determined as well as their orientations. They were discussed in view of the reaction products' structural relations to the PbTe.

The Influence of the Coating Deposition Process on the Interdiffusion Behavior Between Nickel-Based Superalloys and MCrAlY Bond Coats

NASA Astrophysics Data System (ADS)

Elsaß, M.; Frommherz, M.; Oechsner, M.

2018-02-01

In this work, interdiffusion between two nickel-based superalloys and two MCrAlY bond coats is investigated. The MCrAlY bond coats were applied using two different spraying processes, high velocity oxygen fuel spraying (HVOF) and low-pressure plasma spraying. Of primary interest is the evolution of Kirkendall porosity, which can form at the interface between substrate and bond coat and depends largely on the chemical compositions of the coating and substrate. Experimental evidence further suggested that the formation of Kirkendall porosity depends on the coating deposition process. Formation of porosity at the interface causes a degradation of the bonding strength between substrate and coating. After coating deposition, the samples were annealed at 1050 °C for up to 2000 h. Microstructural and compositional analyses were performed to determine and evaluate the Kirkendall porosity. The results reveal a strong influence of both the coating deposition process and the chemical compositions. The amount of Kirkendall porosity formed, as well as the location of appearance, is largely influenced by the coating deposition process. In general, samples with bond coats applied by means of HVOF show accelerated element diffusion. It is hypothesized that recrystallization of the substrate material is a main root cause for these observations.

Deterioration of reflecting coatings by intermetallic diffusion.

PubMed

Hunter, W R; Mikes, T L; Hass, G

1972-07-01

Gold diffraction gratings overcoated with Al + MgF(2) to increase their efficiency in the vacuum ultraviolet suffered a severe loss in efficiency within six months to a year after coating; for example, from 50% to 2% at lambda1216 A. The cause of this loss was assumed to be interdiffusion of Au and Al; therefore, a more complete study of Au-Al film combinations was performed. The coatings were aged at room and elevated temperatures. Reflectance measurements were made in the visible and vacuum ultraviolet spectral regions. For wavelengths longer than lambda900 A, the measurements show very little change until the diffusion boundary reaches the penetration depth of the radiation. If Al is the first surface layer, however, reflectance measurements at lambda584 A permit measuring the progress of the diffusion boundary toward the Al surface because of the low absorptance of Al at this wavelength. Interdiffusion can be effectively eliminated by the use of thin dielectric layers uch as SiO and the natural oxide of Al. Such protected coatings have been exposed for one week at a temperature of 170 degrees C with no visible sign of diffusion, whereas a similar coating without the barrier layer would become useless in less than 1 h. Some preliminary studies have been made with Pt-Al film combinations.

Effect of Gold on the Microstructural Evolution and Integrity of a Sintered Silver Joint

NASA Astrophysics Data System (ADS)

Muralidharan, Govindarajan; Leonard, Donovan N.; Meyer, Harry M.

2017-07-01

There is a need for next-generation, high-performance power electronic packages and systems employing wide-bandgap devices to operate at high temperatures in automotive and electric grid applications. Sintered silver joints are currently being evaluated as an alternative to Pb-free solder joints. Of particular interest is the development of joints based on silver paste consisting of nano- or micron-scale particles that can be processed without application of external pressure. The microstructural evolution at the interface of a pressureless-sintered silver joint formed between a SiC die with Ti/Ni/Au metallization and an active metal brazed (AMB) substrate with Ag metallization at 250°C has been evaluated using scanning electron microscopy (SEM), x-ray microanalysis, and x-ray photoelectron spectroscopy (XPS). Results from focused ion beam (FIB) cross-sections show that, during sintering, pores in the sintered region near to the Au layer tend to be narrow and elongated with long axis oriented parallel to the interface. Further densification results in formation of many small, relatively equiaxed pores aligned parallel to the interface, creating a path for easy crack propagation. X-ray microanalysis results confirm interdiffusion between Au and Ag and that a region with poor mechanical strength is formed at the edge of this region of interdiffusion.

Improvement of band gap profile in Cu(InGa)Se{sub 2} solar cells through rapid thermal annealing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, D.S.; College of Mathematics and Physics, Shanghai University of Electric Power, Shanghai, 200090; Yang, J.

Highlights: • Proper RTA treatment can effectively optimize band gap profile to more expected level. • Inter-diffusion of atoms account for the improvement of the graded band gap profile. • The variation of the band gap profile created an absolute gain in the efficiency by 1.22%. - Abstract: In the paper, the effect of rapid thermal annealing on non-optimal double-graded band gap profiles was investigated by using X-ray photoelectron spectroscopy and capacitance–voltage measurement techniques. Experimental results revealed that proper rapid thermal annealing treatment can effectively improve band gap profile to more optimal level. The annealing treatment could not only reducemore » the values of front band gap and minimum band gap, but also shift the position of the minimum band gap toward front electrode and enter into space charge region. In addition, the thickness of Cu(InGa)Se{sub 2} thin film decreased by 25 nm after rapid thermal annealing treatment. All of these modifications were attributed to the inter-diffusion of atoms during thermal treatment process. Simultaneously, the variation of the band gap profile created an absolute gain in the efficiency by 1.22%, short-circuit current density by 2.16 mA/cm{sup 2} and filled factor by 3.57%.« less

High-performance electrodes for reduced temperature solid oxide fuel cells with doped lanthanum gallate electrolyte. II. La(Sr)CoO 3 cathode

NASA Astrophysics Data System (ADS)

Inagaki, Toru; Miura, Kazuhiro; Yoshida, Hiroyuki; Maric, Radenka; Ohara, Satoshi; Zhang, Xinge; Mukai, Kazuo; Fukui, Takehisa

The reduced temperature solid oxide fuel cell (SOFC) with 0.5 mm thick La 0.9Sr 0.1Ga 0.8Mg 0.2O 3- α (LSGM) electrolyte, La 0.6Sr 0.4CoO 3- δ (LSCo) cathode, and Ni-(CeO 2) 0.8(SmO 1.5) 0.2 (SDC) cermet anode showed an excellent initial performance, and high maximum power density, 0.47 W/cm 2, at 800°C. The results were comparable to those for the conventional SOFC with yttria-stabilized zirconia (YSZ) electrolyte, La(Sr)MnO 3-YSZ cathode and Ni-YSZ cermet anode at 1000°C. Using an LSCo powder prepared by spray pyrolysis, and selecting appropriate sintering temperatures, the lowest cathodic polarization of about 25 mV at 300 mA/cm 2 was measured for a cathode prepared by sintering at 1000°C. Life time cell test results, however, showed that the polarization of the LSCo cathode increased with operating time. From EPMA results, this behavior was considered to be related to the interdiffusion of the elements at the cathode/electrolyte interface. Calcination of LSCo powder could be a possible way to suppress this interdiffusion at the interface.

Solid Liquid Interdiffusion Bonding of (Pb, Sn)Te Thermoelectric Modules with Cu Electrodes Using a Thin-Film Sn Interlayer

NASA Astrophysics Data System (ADS)

Chuang, T. H.; Lin, H. J.; Chuang, C. H.; Yeh, W. T.; Hwang, J. D.; Chu, H. S.

2014-12-01

A (Pb, Sn)Te thermoelectric element plated with a Ni barrier layer and a Ag reaction layer has been joined with a Cu electrode coated with Ag and Sn thin films using a solid-liquid interdiffusion bonding method. This method allows the interfacial reaction between Ag and Sn such that Ag3Sn intermetallic compounds form at low temperature and are stable at high temperature. In this study, the bonding strength was about 6.6 MPa, and the specimens fractured along the interface between the (Pb, Sn)Te thermoelectric element and the Ni barrier layer. Pre-electroplating a film of Sn with a thickness of about 1 μm on the thermoelectric element and pre-heating at 250°C for 3 min ensures the adhesion between the thermoelectric material and the Ni barrier layer. The bonding strength is thus increased to a maximal value of 12.2 MPa, and most of the fractures occur inside the thermoelectric material. During the bonding process, not only the Ag3Sn intermetallics but also Cu6Sn5 forms at the Ag3Sn/Cu interface, which transforms into Cu3Sn with increases in the bonding temperature or bonding time.

Dynamic covalent chemistry enables formation of antimicrobial peptide quaternary assemblies in a completely abiotic manner

NASA Astrophysics Data System (ADS)

Reuther, James F.; Dees, Justine L.; Kolesnichenko, Igor V.; Hernandez, Erik T.; Ukraintsev, Dmitri V.; Guduru, Rusheel; Whiteley, Marvin; Anslyn, Eric V.

2018-01-01

Naturally occurring peptides and proteins often use dynamic disulfide bonds to impart defined tertiary/quaternary structures for the formation of binding pockets with uniform size and function. Although peptide synthesis and modification are well established, controlling quaternary structure formation remains a significant challenge. Here, we report the facile incorporation of aryl aldehyde and acyl hydrazide functionalities into peptide oligomers via solid-phase copper-catalysed azide-alkyne cycloaddition (SP-CuAAC) click reactions. When mixed, these complementary functional groups rapidly react in aqueous media at neutral pH to form peptide-peptide intermolecular macrocycles with highly tunable ring sizes. Moreover, sequence-specific figure-of-eight, dumbbell-shaped, zipper-like and multi-loop quaternary structures were formed selectively. Controlling the proportions of reacting peptides with mismatched numbers of complementary reactive groups results in the formation of higher-molecular-weight sequence-defined ladder polymers. This also amplified antimicrobial effectiveness in select cases. This strategy represents a general approach to the creation of complex abiotic peptide quaternary structures.

Viscosities of nonelectrolyte liquid mixtures. III. Selected binary and quaternary mixtures

NASA Astrophysics Data System (ADS)

Wakefield, D. L.

1988-05-01

This paper is the final in a series of three viscosity and density studies of pure n-alkanes and selected binary and quaternary mixtures. A standard U-tube viscometer was used for viscosity measurements, and a Pyrex flask-type pycnometer was used for density determinations. Results are given here for pure alkane and selected binary mixtures of n-tetradecane + n-octane, for selected quaternary mixtures of n-hexadecane + n-dodecane + n-decane + n-hexane, and for pure and selected quaternary mixtures of n-hexadecane + n-dodecane + n-nonane + n-heptane at 303.16 and 308.16 K. The principle of congruence was tested, as was the Grunberg and Nissan equation, as they have been shown to be useful as prediction techniques for other n-alkane binary mixtures. Comparisons were made between the two groups of quaternary alkane mixtures and the binary n-tetradecane + n-octane mixtures of the same “pseudo” composition to understand better the dependence of mixture viscosities on the composition parameter.

Evaluation of chitosan quaternary ammonium salt-modified resin denture base material.

PubMed

Song, Rong; Zhong, Zhaohua; Lin, Lexun

2016-04-01

Chitosan quaternary ammonium salt displays good antioxidant and antibacterial characteristics and it shows appreciable solubility in water. When added to the traditional denture material to form a resin base, it could promote good oral health by improving the oral environment. In this study, chitosan quaternary ammonium salt was added to the denture material following two different methods. After three months of immersion in artificial saliva, the specimens were tested for tensile strength and were scanned by electron microscope. The murine fibroblast cytotoxicity and antibacterial properties were also tested. The result showed no significant differences in the tensile strength and in the proliferation of murine L929 fibroblast cells. The two structures of chitosan quaternary ammonium salt-modified denture material had different degrees of corrosion resistance and antimicrobial properties. These results indicate that chitosan quaternary ammonium salt-modified resin denture base material has the potential to become a new generation oral denture composite material. Copyright © 2015 Elsevier B.V. All rights reserved.

The competition of charge remote and charge directed fragmentation mechanisms in quaternary ammonium salt derivatized peptides--an isotopic exchange study.

PubMed

Cydzik, Marzena; Rudowska, Magdalena; Stefanowicz, Piotr; Szewczuk, Zbigniew

2011-12-01

Derivatization of peptides as quaternary ammonium salts (QAS) is a promising method for sensitive detection by electrospray ionization tandem mass spectrometry (Cydzik et al. J. Pept. Sci. 2011, 17, 445-453). The peptides derivatized by QAS at their N-termini undergo fragmentation according to the two competing mechanisms - charge remote (ChR) and charge directed (ChD). The absence of mobile proton in the quaternary salt ion results in ChR dissociation of a peptide bond. However, Hofmann elimination of quaternary salt creates an ion with one mobile proton leading to the ChD fragmentation. The experiments on the quaternary ammonium salts with deuterated N-alkyl groups or amide NH bonds revealed that QAS derivatized peptides dissociate according to the mixed ChR-ChD mechanism. The isotopic labeling allows differentiation of fragments formed according to ChR and ChD mechanisms. © The Author(s) 2011. This article is published with open access at Springerlink.com

Poly(3,4-ethylenedioxythiophene)-Poly(styrenesulfonate) Interlayer Insertion Enables Organic Quaternary Memory.

PubMed

Cheng, Xue-Feng; Hou, Xiang; Qian, Wen-Hu; He, Jing-Hui; Xu, Qing-Feng; Li, Hua; Li, Na-Jun; Chen, Dong-Yun; Lu, Jian-Mei

2017-08-23

Herein, for the first time, quaternary resistive memory based on an organic molecule is achieved via surface engineering. A layer of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) was inserted between the indium tin oxide (ITO) electrode and the organic layer (squaraine, SA-Bu) to form an ITO/PEDOT-PSS/SA-Bu/Al architecture. The modified resistive random-access memory (RRAM) devices achieve quaternary memory switching with the highest yield (∼41%) to date. Surface morphology, crystallinity, and mosaicity of the deposited organic grains are greatly improved after insertion of a PEDOT-PSS interlayer, which provides better contacts at the grain boundaries as well as the electrode/active layer interface. The PEDOT-PSS interlayer also reduces the hole injection barrier from the electrode to the active layer. Thus, the threshold voltage of each switching is greatly reduced, allowing for more quaternary switching in a certain voltage window. Our results provide a simple yet powerful strategy as an alternative to molecular design to achieve organic quaternary resistive memory.

Progress report. Task 1 - quaternary tectonics, 1 October 1991--30 September 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1992-09-30

Progress is reported on a study concerned with the quaternary tectonics of Yucca Mountain, the proposed site for an underground disposal facility for high-level radioactive wastes. Refinement and revision of crater Flat Quaternary stratigraphy continued and consisted of several activities: revision of rock varnish cation leaching curve; sample comparison of RV manganese;,iron microlaminations;and correlation of Crater Flat allostratigraphic units with regional chronologies.

Removal of Zn or Cd and cyanide from cyanide electroplating wastes

DOEpatents

Moore, Fletcher L.

1977-05-31

A method is described for the efficient stripping of stable complexes of a selected quaternary amine and a cyanide of Zn or Cd. An alkali metal hydroxide solution such as NaOH or KOH will quantitatively strip a pregnant extract of the quaternary ammonium complex of its metal and cyanide content and regenerate a quaternary ammonium hydroxide salt which can be used for extracting further metal cyanide values.

INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Simple formula for the thermal conductivity of a quaternary solid solution

NASA Astrophysics Data System (ADS)

Nakwaski, W.

1988-11-01

An analysis is made of the thermal conductivity of quaternary solid solutions (alloys) allowing for their disordered structure on the basis of a phenomenological analysis proposed by Abeles. This method is applied to a quaternary solid solution In1 - xGaxAsyP1 - y. A simple analytic expression is derived for the thermal conductivity of this material.

Advances in the synthesis of α-quaternary α-ethynyl α-amino acids.

PubMed

Boibessot, Thibaut; Bénimélis, David; Meffre, Patrick; Benfodda, Zohra

2016-09-01

α-Quaternary α-ethynyl α-amino acids are an important class of non-proteinogenic amino acids that play an important role in the development of peptides and peptidomimetics as therapeutic agents and in the inhibition of enzyme activities. This review provides an overview of the literature concerning synthesis and applications of α-quaternary α-ethynyl α-amino acids covering the period from 1977 to 2015.

Classification of protein quaternary structure by functional domain composition

PubMed Central

Yu, Xiaojing; Wang, Chuan; Li, Yixue

2006-01-01

Background The number and the arrangement of subunits that form a protein are referred to as quaternary structure. Quaternary structure is an important protein attribute that is closely related to its function. Proteins with quaternary structure are called oligomeric proteins. Oligomeric proteins are involved in various biological processes, such as metabolism, signal transduction, and chromosome replication. Thus, it is highly desirable to develop some computational methods to automatically classify the quaternary structure of proteins from their sequences. Results To explore this problem, we adopted an approach based on the functional domain composition of proteins. Every protein was represented by a vector calculated from the domains in the PFAM database. The nearest neighbor algorithm (NNA) was used for classifying the quaternary structure of proteins from this information. The jackknife cross-validation test was performed on the non-redundant protein dataset in which the sequence identity was less than 25%. The overall success rate obtained is 75.17%. Additionally, to demonstrate the effectiveness of this method, we predicted the proteins in an independent dataset and achieved an overall success rate of 84.11% Conclusion Compared with the amino acid composition method and Blast, the results indicate that the domain composition approach may be a more effective and promising high-throughput method in dealing with this complicated problem in bioinformatics. PMID:16584572

Atomic-scale properties of Ni-based FCC ternary, and quaternary alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tamm, Artur; Aabloo, Alvo; Klintenberg, Mattias

2015-08-26

The aim of our study is to characterize some atomic-scale properties of Ni-based FCC multicomponent alloys. For this purpose, we use Monte Carlo method combined with density functional theory calculations to study short-range order (SRO), atomic displacements, electronic density of states, and magnetic moments in equimolar ternary NiCrCo, and quaternary NiCrCoFe alloys. The salient features for the ternary alloy are a negative SRO parameter between Ni Cr and a positive between Cr Cr pairs as well as a weakly magnetic state. For the quaternary alloy we predict negative SRO parameter for Ni Cr and Ni Fe pairs and positive formore » Cr Cr and Fe Fe pairs. Atomic displacements for both ternary and quaternary alloys are negligible. In contrast to the ternary, the quaternary alloy shows a complex magnetic structure. The electronic structure of the ternary and quaternary alloys shows differences near the Fermi energy between a random solid solution and the predicted structure with SRO. Despite that, the calculated EXAFS spectra does not show enough contrast to discriminate between random and ordered structures. Finally, the predicted SRO has an impact on point-defect energetics, electron phonon coupling and thermodynamic functions and thus, SRO should not be neglected when studying properties of these two alloys.« less

Mapping the North Sea base-Quaternary: using 3D seismic to fill a gap in the geological record

NASA Astrophysics Data System (ADS)

Lamb, Rachel; Huuse, Mads; Stewart, Margaret; Brocklehurst, Simon H.

2014-05-01

The identification and mapping of the base-Quaternary boundary in the central parts of the North Sea is problematic due to the change from an unconformable transition between Pliocene and Pleistocene deltaic deposits in the southern North Sea to a conformable one further north (Sejrup et al 1991; Gatliff et al 1994). The best estimates of the transition use seismic reflection data to identify a 'crenulated reflector' (Buckley 2012), or rely on correlating sparse biostratigraphy (Cameron et al 1987). Recent integration of biostratigraphy, pollen analysis, paleomagnetism and amino acid analysis in the Dutch and Danish sectors (Rasmussen et al 2005; Kuhlmann et al 2006) allows greater confidence in the correlation to a regional 3D seismic dataset and show that the base-Quaternary can be mapped across the entire basin. The base-Quaternary has been mapped using the PGS MegaSurvey dataset from wells in the Danish Sector along the initially unconformable horizon and down the delta front into the more conformable basin giving a high degree of confidence in the horizon pick. The mapped horizon is presented here alongside the difference between this new interpretation and the previously interpreted base-Quaternary (Buckley 2012). The revised base-Quaternary surface reaches a depth of 1248 ms TWT or approximately 1120 m (assuming average velocity of 1800 m/s) showing an elongate basin shape that follows the underlying structure of the Central Graben. The difference between the revised base-Quaternary and the traditional base-Quaternary reaches a maximum of over 600 ms TWT or approximately 540 m in the south-west with over 300 ms TWT or approximately 270 m at the Josephine well (56° 36.11'N, 2° 27.09'E) in the centre of the basin. Mapping this new base-Quaternary allows for the interpretation of the paleo-envionrment during the earliest Quaternary. Seismic attribute analysis indicates a deep water basin with sediment deposition from multiple deltas and redistribution by deep water currents. This has strong implications for both the Quaternary climate archive and petroleum systems in the North Sea. Key Words: base-Quaternary; chronostratigraphy: seismic interpretation; paleoenvironments References Buckley, F.A., (2012) 'An Early Pleistocene grounded ice sheet in the Central North Sea' From: Huuse, M., Redfern, J., Le Heron, D.P., Dixon, R.J., Moscariello, A., Craig, J. (eds) 'Glaciogenic reservoirs and Hydrocarbon Systems' Geological Society, London, Special Publications, 368 Cameron, T.D.J., Stoker, M.S., Long, D., (1987) 'The history of Quaternary sedimentation in the UK sector of the North Sea Basin' Journal of the Geological Society, 144, 43-58 Gatliff, R.W, Richards, P.C, Smith, K, Graham, C.C, McCormac, M, Smith, N.J.P, Long, D, Cameron, T.D.J, Evans, D, Stevenson, A.G, Bulat, J, Ritchie, J.D, (1994) 'United Kingdom offshore regional report: the geology of the central North Sea.' London: HMSO for the British Geological Survey Kulhmann, G., Langereis C.G., Munsterman, D., van Leeuwen, R.-J., Verreussel, R., Meulenkamp, J.E., Wong, Th.E., 2006 'Intergrated chronostratigraphy of the Pliocene-Pliestocene interval and its relation to the regional stratigraphical stages in the Southern North Sea region' Netherlands Journal of Geosciences 85(1), 29-45 Rasmussen, E.A., Vejb?k O.V., Bidstrup, T., Piasecki, S., Dybkj?r, K., 2005 'Late Cenozoic depositional history of the Danish North Sea Basin: implications for the petroleum systems in the Kraka, Halfdan, Siri and Nini fields', Petroleum Geology Conference series 6, 1347-1358 Sejrup, H.P., Aareseth, I., Haflidason, H., 1991 'The Quaternary succession in the northern North Sea' Marine Geology 101 103-111

[The action of quaternary ammonium derivatives on respiration and nitrate reduction in Pseudomonas aeruginosa].

PubMed

Bievskiĭ, A N

1994-01-01

It was revealed that the same dosages of quaternary ammonium derivatives, such as decamethoxin and cetyltrimethylammonium bromide, inhibited the respiratory chains and caused destruction of Pseudomonas aeruginosa under aerobic conditions more effectively than under anaerobic ones when anions of nitric acid were the terminal acceptors of electrons. It was also registered that Pseudomonas were able to dissimilatory nitrate reduction in the media under the polysaccharide layer that was produced by these bacteria: this fact possibly proves the possibility of survival of denitrifying bacteria in solutions with high concentrations of quaternary ammonium salts. The data obtained permit supposing that inhibitors of respiratory chains and oxidizers may be used as potentiators of the antimicrobial action of quaternary ammonium derivatives.

Derivatization of peptides as quaternary ammonium salts for sensitive detection by ESI-MS.

PubMed

Cydzik, Marzena; Rudowska, Magdalena; Stefanowicz, Piotr; Szewczuk, Zbigniew

2011-06-01

A series of model peptides in the form of quaternary ammonium salts at the N-terminus was efficiently prepared by the solid-phase synthesis. Tandem mass spectrometric analysis of the peptide quaternary ammonium derivatives was shown to provide sequence confirmation and enhanced detection. We designed the 2-(1,4-diazabicyclo[2.2.2] octylammonium)acetyl quaternary ammonium group which does not suffer from neutral losses during MS/MS experiments. The presented quaternization of 1,4-diazabicyclo[2.2.2]octane (DABCO) by iodoacetylated peptides is relatively easy and compatible with standard solid-phase peptide synthesis. This methodology offers a novel sensitive approach to analyze peptides and other compounds. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.

Dual-Color Emission in Hybrid III-Nitride/ZnO Light Emitting Diodes

NASA Astrophysics Data System (ADS)

Namkoong, Gon; Trybus, Elaissa; Cheung, Maurice C.; Doolittle, W. Alan; Cartwright, Alexander N.; Ferguson, Ian; Seong, Tae-Yeon; Nause, Jeff

2010-02-01

We report dual-color production of the blue and green regions using hybrid nitride/ZnO light emitting diode (LED) structures grown on ZnO substrates. The blue emission is ascribed to the near-band edge transition in InGaN while green emission is related to Zn-related defect levels formed by the unintentional interdiffusion of Zn into the InGaN active layer from the ZnO substrates.

Composite construction for nuclear fuel containers

DOEpatents

Cheng, B. C.; Rosenbaum, H. S.; Armijo, J. S.

1987-04-21

Disclosed is an improved method for producing nuclear fuel containers of a composite construction having components providing therein a barrier system for resisting destructive action by volatile fission products or impurities and also interdiffusion of metal constituents, and the product thereof. The composite nuclear fuel containers of the method comprise a casing of zirconium or alloy thereof with a layer of copper overlying an oxidized surface portion of the zirconium or alloy thereof. 1 fig.

Quaternary dinoflagellate cysts in the Arctic Ocean: Potential and limitations for stratigraphy and paleoenvironmental reconstructions

NASA Astrophysics Data System (ADS)

Matthiessen, Jens; Schreck, Michael; De Schepper, Stijn; Zorzi, Coralie; de Vernal, Anne

2018-07-01

The Arctic Ocean is a siliciclastic depositional environment which lacks any rock-forming biogenic calcareous and siliceous components during large parts of its Quaternary history. These hemipelagic sediments are nevertheless suitable for the study of organic-walled microfossils of which the fossil remains of dinoflagellates - dinoflagellate cysts - are the most important group. Dinoflagellate cysts have become an important tool in paleoceanography of the high northern latitudes, but their potential for Quaternary biostratigraphy has remained largely unexplored. Dinoflagellate cysts are the dominant marine palynomorph group which is more continuously present in the marginal seas (e.g. Barents Sea, Bering Sea) than in the Arctic Ocean itself throughout the Quaternary. Most species have long stratigraphic ranges, are temporary absent and show abundance variations on glacial-interglacial timescales. Of the more than 30 taxa recorded, only Habibacysta tectata and Filisphaera filifera became extinct in the Pleistocene. The highest persistent occurrence of H. tectata at ca. 2.0 Ma and the top of F. filifera acme at ca. 1.8 Ma can be used for supra-regional stratigraphic correlation between the Arctic Ocean and adjacent basins. These events corroborate a slow sedimentation rate model for the Quaternary section on the central Lomonosov Ridge, but a combination of different methods will have to be applied to provide a detailed chronostratigraphy. The occurrence of cysts of phototrophic dinoflagellates in certain stratigraphic intervals on Lomonosov Ridge supports published evidence of episodic opening of the multiyear Arctic sea ice cover during the Quaternary probably related to a stronger inflow of Atlantic water. This contradicts the hypothesis of a permanently ice covered central Arctic Ocean in the Quaternary.

Surface modification and antimicrobial properties of cellulose nanocrystals

NASA Astrophysics Data System (ADS)

Bespalova, Yulia A.

Surface modification of cellulose nanocrystals (CNC) was performed by acetylation and subsequent reaction with various tertiary amines with different lengths of alkyl groups. Chloroacetic anhydride (95%) was used for acetylation. The acetylation of CNC was confirmed using IR spectroscopy. The bands associated with C=0 stretching (1740 cm-1) and C-Cl stretching (793 cm -1) was present in the acetylated CNC but they were absent in the neat CNC. It has been suggested that the primary hydroxyl groups of CNC are substituted by chloro acetyl groups during acetylation reaction. Subsequent reaction of chloro acetylated CNC with N, N - Dimethyl ethylamine, N, N - Dimethyl hexylamine, N, N - Dimethyl dodecylamine, N, N - Dimethyl hexadecylamine and N, N - Dimethyl decylamine formed quaternary ammonium salts. These quaternary ammonium salts were characterized by FTIR and solid state13C NMR spectroscopy. FTIR spectra of five types of quaternary ammonium salts of CNC are similar and they showed infrared bands at 2905 -1 and 2850 cm-1, attributed to symmetrical and unsymmetrical C-H stretching vibration. The absence of C-Cl band at 793 cm-1 proves that quaternary salt formation was successful. The 13C NMR spectrum of quaternary ammonium modified CNC with N, N - Dimethyl dodecylamine shows several additional resonances ranging from 14.5 ppm to 58.0 ppm when compared to 13C NMR spectrum of pure CNC. This evidence proves that long alkyl chains have been added to the pure CNC. The disc diffusion method confirmed that quaternary ammonium modified CNCs with a chain longer than ten carbons are effective antimicrobial agents against Staphylococcus aureus and E. coli bacteria. Pure CNC and quaternary ammonium modified CNCs with an alkyl chain length of ten or less were not able to inhibit bacteria growth.

A novel assay to measure tertiary and quaternary amines in wastewater: An indicator for NDMA wastewater precursors.

PubMed

Woods-Chabane, Gwen C; Glover, Caitlin M; Marti, Erica J; Dickenson, Eric R V

2017-07-01

This study examined the potential of using a novel bulk amine assay as an approximation for the tertiary and quaternary amine load in wastewaters and surface water samples, and this approximation was compared to N-nitrosodimethylamine (NDMA) formation potential using chloramines. An existing colorimetric method was examined and optimized for the detection of amines in environmental water samples. The method consists of liquid-liquid extraction followed by a catalyzed reaction to form a yet-undefined product that is known to be both a strong chromophore and fluorophore. Previous work verified that this reaction was effectively catalyzed by a number of compounds containing tertiary and quaternary amine moieties. Many tertiary and quaternary compounds are also efficient producers of NDMA under chloramination conditions, and a linear correlation was consequently derived from the bulk amine signals vs. NDMA formation potential in various wastewater samples (R 2  = 0.74; n = 24; p-value < 0.05). The results provide evidence that approximately 2% of the tertiary and quaternary amines measured can form NDMA and an estimated 0.01-1.3% of nitrogen in dissolved organic nitrogen originates from these bulk amines. The normalization of NDMA concentration by the amine measurement revealed that ozone effectively destroyed those tertiary and quaternary amine structures more likely to form NDMA in treated wastewater samples. This bulk amine assay illustrates that proxy measurements of tertiary and quaternary amines can be linked to the NDMA formation potential of a given sample, and this approach may prove useful as a characterizing tool for NDMA precursors in wastewater. Copyright © 2017 Elsevier Ltd. All rights reserved.

Curare-Like Activity of Mono-Quaternary Salts Containing Adamantyl Residue at the Nitrogen Atom

DTIC Science & Technology

As shown in previous works, mono-quaternary salts of alkamine esters of benzoic and cinnamic acids types and exhibit a pronounced curare like action...A series of methiodides of alkamine esters of benzoic and cinnamic acids were synthesized, containing at the quaternary nitrogen atom a 1-adamantyl...adamantyl causes a change of the substance’s mechanism of action, this applying both to the benzoic acid derivatives and to the cinnamic acid derivatives

Quaternary vertebrate faunas from Sumba, Indonesia: implications for Wallacean biogeography and evolution

PubMed Central

Crees, Jennifer J.; Hansford, James; Jeffree, Timothy E.; Crumpton, Nick; Kurniawan, Iwan; Setiyabudi, Erick; Paranggarimu, Umbu; Dosseto, Anthony; van den Bergh, Gerrit D.

2017-01-01

Historical patterns of diversity, biogeography and faunal turnover remain poorly understood for Wallacea, the biologically and geologically complex island region between the Asian and Australian continental shelves. A distinctive Quaternary vertebrate fauna containing the small-bodied hominin Homo floresiensis, pygmy Stegodon proboscideans, varanids and giant murids has been described from Flores, but Quaternary faunas are poorly known from most other Lesser Sunda Islands. We report the discovery of extensive new fossil vertebrate collections from Pleistocene and Holocene deposits on Sumba, a large Wallacean island situated less than 50 km south of Flores. A fossil assemblage recovered from a Pleistocene deposit at Lewapaku in the interior highlands of Sumba, which may be close to 1 million years old, contains a series of skeletal elements of a very small Stegodon referable to S. sumbaensis, a tooth attributable to Varanus komodoensis, and fragmentary remains of unidentified giant murids. Holocene cave deposits at Mahaniwa dated to approximately 2000–3500 BP yielded extensive material of two new genera of endemic large-bodied murids, as well as fossils of an extinct frugivorous varanid. This new baseline for reconstructing Wallacean faunal histories reveals that Sumba's Quaternary vertebrate fauna, although phylogenetically distinctive, was comparable in diversity and composition to the Quaternary fauna of Flores, suggesting that similar assemblages may have characterized Quaternary terrestrial ecosystems on many or all of the larger Lesser Sunda Islands. PMID:28855367

Variation in Inflammatory/Regulatory Cytokines in Secondary, Tertiary, and Quaternary Challenges with Dengue Virus

PubMed Central

Sierra, Beatriz; Pérez, Ana B.; Alvarez, Mayling; García, Gissel; Vogt, Katrin; Aguirre, Eglys; Schmolke, Kathrin; Volk, Hans-Dieter; Guzmán, María G.

2012-01-01

Secondary heterologous dengue infection is a risk factor for severe disease manifestations because of the immune-enhancement phenomenon. Succeeding clinical infections are seldom reported, and the clinical course of tertiary and quaternary dengue infections is not clear. Cuba represents a unique environment to study tertiary/quaternary dengue infections in a population with known clinical and serologic dengue markers and no dengue endemicity. We took advantage of this exceptional epidemiologic condition to study the effect of primary, secondary, tertiary, and quaternary dengue infection exposure on the expression of pro-inflammatory and regulatory cytokines, critical in dengue infection pathogenesis, by using a dengue infection ex vivo model. Whereas secondary exposure induced a high cytokine response, we found a significantly lower expression of tumor necrosis factor-α, interferon-γ, interleukin-10, and tumor growth factor-β after tertiary and quaternary infectious challenge. Significant differences in expression of the cytokines were seen between the dengue immune profiles, suggesting that the sequence in which the immune system encounters serotypes may be important in determining the nature of the immune response to subsequent infections. PMID:22802438

A study of Quaternary structures in the Qom region, West Central Iran

NASA Astrophysics Data System (ADS)

Babaahmadi, A.; Safaei, H.; Yassaghi, A.; Vafa, H.; Naeimi, A.; Madanipour, S.; Ahmadi, M.

2010-12-01

West Central Iran comprises numerous Quaternary faults. Having either strike-slip or thrust mechanisms, these faults are potentially active and therefore capable of creating destructive earthquakes. In this paper, we use satellite images as well as field trips to identify these active faults in the Qom region. The Qom and Indes faults are the main NW-trending faults along which a Quaternary restraining step-over zone has formed. Kamarkuh, Mohsen Abad, and Ferdows anticlines are potentially active structures that formed in this restraining step-over zone. There are some thrusts and anticlines, such as the Alborz anticline and Alborz fault, which are parallel to strike-slip faults such as the Qom fault, indicating deformation partitioning in the area. In addition to NW-trending structures, there is an important NE-trending fault known as the Qomrud fault that has deformed Quaternary deposits and affected Kushk-e-Nosrat fault, Alborz anticline, and Qomrud River. The results of this study imply that the major Quaternary faults of West Central Iran and their restraining step-over zones are potentially active.

Ancient dna from pleistocene fossils: Preservation, recovery, and utility of ancient genetic information for quaternary research

NASA Astrophysics Data System (ADS)

Yang, Hong

Until recently, recovery and analysis of genetic information encoded in ancient DNA sequences from Pleistocene fossils were impossible. Recent advances in molecular biology offered technical tools to obtain ancient DNA sequences from well-preserved Quaternary fossils and opened the possibilities to directly study genetic changes in fossil species to address various biological and paleontological questions. Ancient DNA studies involving Pleistocene fossil material and ancient DNA degradation and preservation in Quaternary deposits are reviewed. The molecular technology applied to isolate, amplify, and sequence ancient DNA is also presented. Authentication of ancient DNA sequences and technical problems associated with modern and ancient DNA contamination are discussed. As illustrated in recent studies on ancient DNA from proboscideans, it is apparent that fossil DNA sequence data can shed light on many aspects of Quaternary research such as systematics and phylogeny. conservation biology, evolutionary theory, molecular taphonomy, and forensic sciences. Improvement of molecular techniques and a better understanding of DNA degradation during fossilization are likely to build on current strengths and to overcome existing problems, making fossil DNA data a unique source of information for Quaternary scientists.

Novel BTlGaN semiconducting materials for infrared opto-electronic devices

NASA Astrophysics Data System (ADS)

Assali, Abdenacer; Bouslama, M'hamed

2017-03-01

BTlGaN quaternary alloys are proposed as new semiconductor materials for infrared opto-electronic applications. The structural and opto-electronic properties of zinc blende BxTlyGa1-x-yN alloys lattice matched to GaN with (0 ⩽ x and y ⩽ 0.187) are studied using density functional theory (DFT) within full-potential linearized augmented plane wave (FP-LAPW) method. The calculated structural parameters such as lattice constant a0 and bulk modulus B0 are found to be in good agreement with experimental data using the new form of generalized gradient approximation (GGA-WC). The band gaps of the compounds are also found very close to the experimental results using the recently developed Tran-Blaha-modified Becke-Johnson (TB-mBJ) exchange potential. A quaternary BxTlyGa1-x-yN is expected to be lattice matched to the GaN substrate with concentrations x = 0.125 and y = 0.187 allows to produce high interface layers quality. It has been found that B incorporation into BTlGaN does not significantly affect the band gap, while the addition of dilute Tl content leads to induce a strong reduction of the band gap, which in turn increases the emission wavelengths to the infrared region. The refractivity, reflectivity and absorption coefficient of these alloys were investigated. BTlGaN/GaN is an interesting new material to be used as active layer/barriers in quantum wells suitable for realizing advanced Laser Diodes and Light-Emitting Diodes as new sources of light emitting in the infrared spectrum region.

Palladium-Catalyzed Asymmetric Alkylation in the Synthesis of Cyclopentanoid and Cycloheptanoid Core Structures Bearing All-Carbon Quaternary Stereocenters

PubMed Central

Hong, Allen Y.; Bennett, Nathan B.; Krout, Michael R.; Jensen, Thomas; Harned, Andrew. M.

2011-01-01

General catalytic asymmetric routes toward cyclopentanoid and cycloheptanoid core structures embedded in numerous natural products have been developed. The central stereoselective transformation in our divergent strategies is the enantioselective decarboxylative alkylation of seven-membered β-ketoesters to form α-quaternary vinylogous esters. Recognition of the unusual reactivity of β-hydroxyketones resulting from the addition of hydride or organometallic reagents enabled divergent access to γ-quaternary acylcyclopentenes through a ring contraction pathway or γ-quaternary cycloheptenones through a carbonyl transposition pathway. Synthetic applications of these compounds were explored through the preparation of mono-, bi-, and tricyclic derivatives that can serve as valuable intermediates for the total synthesis of complex natural products. This work complements our previous work with cyclohexanoid systems. PMID:22347731

Quaternary Tectonic and Climatic Processes shaping the Central Andean hyperarid forearc (southern Peru)

NASA Astrophysics Data System (ADS)

Audin, Laurence; Benavente, Carlos; Zerathe, Swann; Saillard, Marianne; Hall, Sarah R.; Farber, Daniel L.

2015-04-01

Understanding the forearc structure and processes related to Quaternary evolution and uplift of the Western Andean Cordillera remains an outstanding scientific issue. Models of Andean Plateau evolution based on Tertiary volcanic stratigraphy since 5Ma suggest that the deformation was focused along the eastern margin of the plateau and that minimal uplift occurred along the Pacific margin. On the contrary, new tectonic data and Quaternary surface 10Be dating highlight the presence of recently active deformation, incision and alluvial processes within the upper Andean forearc together with a regional uplift of the coastal zone. Additionally, the high obliquity observed in the northern Arica Bend region makes it an ideal target to discuss whether partitioning of the oblique convergence is accommodated by the neotectonic features that dissect the Quaternary forearc. Our goals are both to decipher the Quaternary tectonic and climatic processes shaping the hyperarid forearc along strike and across strike. Finally, we aim to quantify the respective influence of these factors in the overall uplift of the Western Andes. Indeed, sequences of pediment surfaces, landslide products, paleolake deposits and marine terraces found along the oblique Peruvian margin are a unique set of datable markers that can be used to quantify the rates of Quaternary processes. In this study, we focus on the southern Peru hyperarid Atacama area where regional surfaces and tectonic markers (scarps, folds, temporary streams and paleolake levels offsets…) are well preserved for the Quaternary timescale. Numerous landsliding events align on the major fault segments and reflect Plio-Pleistocene climatic and tectonic activity together with filled and strath terraces. As the present day sea-level is one of the highest levels recorded for Quaternary time span, any emerged marine terrace is preserved by tectonic coastal uplift. In particular, the geomorphic and chronologic correlation between marine and continental planation surfaces or terraces permit to deduce net vertical rates and suggests that the along strike uplift affected not only the coast but also the overall ~50 km-wide forearc of the Western Andes. We produced a chronology of remnant low-relief surfaces and a new neotectonic map of the Central Andean forearc between ~14° and 18°S based on detailed field mapping and 10Be cosmogenic dating. We address 1) the spatial and temporal correlations of various markers, and 2) the correlation of the surface abandonment ages to various regional climatic events and 3) the description of neotectonic activity accommodating both uplift and partitioning. Multiple markers yield 10Be surface abandonment ages that spanning 35 ka to >2 Ma. Erosion surfaces >2 Ma yield low erosion rates of <0.1mm/yr. However uplift rates of ~0.1-1mm/yr and multiple surfaces dated at ~35 ka suggest that the hyperarid forearc landscape has been recently modified through Quaternary surface uplift and climatic events, contradicting the Miocene fossil forearc hypothesis. Generally, surface abandonment ages and activated landslides periods tend to correlate with cold wet periods preceding Plio Pleistocene deglaciation on the Altiplano. Finally, neotectonic oblique faults connecting at depth participate to topography building in the Arica Bend region and suggest that Quaternary surface abandonment is the result of both surface uplift in the forearc and specific high-discharge climate periods in the high Andes. Obtained Quaternary regional uplift rates and individual slip-rates suggest that the Andean forearc may accommodate as much as 0.5 to 1 mm/yr of regional uplift for the Quaternary time period.

Experimental determination of water activity for binary aqueous cerium(III) ionic solutions: application to an assessment of the predictive capability of the binding mean spherical approximation model.

PubMed

Ruas, Alexandre; Simonin, Jean-Pierre; Turq, Pierre; Moisy, Philippe

2005-12-08

This work is aimed at a description of the thermodynamic properties of actinide salt solutions at high concentration. The predictive capability of the binding mean spherical approximation (BIMSA) theory to describe the thermodynamic properties of electrolytes is assessed in the case of aqueous solutions of lanthanide(III) nitrate and chloride salts. Osmotic coefficients of cerium(III) nitrate and chloride were calculated from other lanthanide(III) salts properties. In parallel, concentrated binary solutions of cerium nitrate were prepared in order to measure experimentally its water activity and density as a function of concentration, at 25 degrees C. Water activities of several binary solutions of cerium chloride were also measured to check existing data on this salt. Then, the properties of cerium chloride and cerium nitrate solutions were compared within the BIMSA model. Osmotic coefficient values for promethium nitrate and promethium chloride given by this theory are proposed. Finally, water activity measurements were made to examine the fact that the ternary system Ce(NO3)3/HNO3/H2O and the quaternary system Ce(NO3)3/HNO3/N2H5NO3/H2O may be regarded as "simple solutions" (in the sense of Zdanovskii and Mikulin).

Algicidal Activity of a Surface-Bonded Organosilicon Quaternary Ammonium Chloride

PubMed Central

Walters, P. A.; Abbott, E. A.; Isquith, A. J.

1973-01-01

The hydrolysis product of a quaternary amine-containing organosilicon salt, 3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride, was found to exhibit algicidal activity while chemically bonded to a variety of substrates. Six representative species of Chlorophyta, Cyanophyta, and Chrysophyta were used to evaluate the algicidal activity. Substrate-bonded 14C-labeled organosilicon quaternary ammonium salt when attached to nonwoven fibers was durable to repeated washings, and algicidal activity could not be attributed to slow release of the chemical. Images PMID:4632852

Map showing thickness of saturated Quaternary deposits, Sugar House quadrangle, Salt Lake County, Utah, February 1972

USGS Publications Warehouse

Mower, R.W.

1973-01-01

Saturated Quaternary deposits in the Sugar Horse quadrangle supply significant quantities of water to wells from which water is withdrawn for domestic, municipal, industrial, and irrigation uses. The deposits consist of clay, silt, sand, and gravel; individual beds range from a few inches to several tens of feet thick. The principal aquifer, which is almost completely within the Quaternary deposits, supplied about 4 percent, or 9,000 acre-feet, of the municipal and industrial water used annually in Salt Lake County during 1964-68.As a general rule, more water is stored and more water will be yielded to a well where aquifers are thicker. This map can be used as a general guide to those areas where greatest amounts of water are stored in the aquifer, and where yields to wells may be greater. Local variations in the ability of saturated deposits to transmit water can alter the general relationship between aquifer thickness and yield of wells.The thickness of saturated Quaternary deposits within the area of the Sugar Horse quadrangle ranges from zero to about 650 feet, as shown on the map. The thickest section of these deposits is near the southwestern corner of the quadrangle, and the thinnest section is along the mountain front adjacent to the approximate eastern limit of saturated Quaternary deposits.The thickness of saturated Quaternary deposits shown on this map is based on drillers’ logs for 55 deep wells (which show the thickness of the Quaternary deposits) and on water-level measurements made in February 1972 in wells in unconfined shallow aquifers.Reports in the following list of selected references contain other information about the saturated Quaternary deposits in this and adjacent parts of Jordan Valley, Utah. The basic-data reports and releases contain well logs, water-level measurements, and other types of basic ground-water data. The interpretive repots contain discussions of the occurrence of ground water, tests to determine hydraulic properties of the aquifer, and related information. Ground-water terms used in this report have been defined by Lohman and others (1972).

A major change in precipitation gradient on the Chinese Loess Plateau at the Pliocene-Quaternary boundary

NASA Astrophysics Data System (ADS)

Peng, Wenbin; Nie, Junsheng; Wang, Zhao; Qiang, Xiaoke; Garzanti, Eduardo; Pfaff, Katharina; Song, Yougui; Stevens, Thomas

2018-04-01

Spatiotemporal variations in East Asian Monsoon (EAM) precipitation during the Quaternary have been intensively studied. However, spatial variations in pre-Quaternary EAM precipitation remain largely uninvestigated, preventing a clear understanding of monsoon dynamics during a warmer climatic period. Here we compare the spatial differences in heavy mineral assemblages between Quaternary loess and pre-Quaternary Red Clay on the Chinese Loess Plateau (CLP) to analyze spatial patterns in weathering. Prior studies have revealed that unstable hornblende is the dominant (∼50%) heavy mineral in Chinese loess deposited over the past 500 ka, whereas hornblende content decreases to <10% in strata older than ∼1 Ma in the central CLP because of diagenesis. In the present study we found that hornblende is the dominant heavy mineral in 2-2.7 Ma loess on the northeastern CLP (at Jiaxian), which today receives little precipitation. Conversely, hornblende content in the upper Miocene-Pliocene Red Clay at Jiaxian is <10%, as in the central CLP. The early Quaternary abundance of hornblende at Jiaxian indicates that the current northwestward-decreasing precipitation pattern and consequent dry climate at Jiaxian must have been initiated since ∼2.7 Ma, preventing hornblende dissolution to amounts <10% as observed in the central CLP. By contrast, the 7 Ma and 3 Ma Jiaxian Red Clay hornblende content is significantly less than that of the Xifeng samples, despite the fact that today Xifeng receives more precipitation than Jiaxian, with expected enhanced hornblende weathering. This suggests that the northeastern CLP received more precipitation during the Late Miocene-Pliocene than at Xifeng, indicating that the precipitation gradient on the CLP was more east-west during the Late Miocene-Pliocene rather than northwest-southeast as it was in the Quaternary. A comparison of magnetic susceptibility records for these sections confirms this inference. We attribute this major change in climatic patterns at ∼2.7 Ma to decreased northward moisture transportation associated with Northern Hemisphere glaciation and cooling in the Quaternary. This study therefore demonstrates the potential usefulness of employing heavy mineral analysis in both paleoclimatic and paleooceanographic reconstructions.

Prevalence of IgE against neuromuscular blocking agents in hairdressers and bakers.

PubMed

Dong, S; Acouetey, D S; Guéant-Rodriguez, R-M; Zmirou-Navier, D; Rémen, T; Blanca, M; Mertes, P M; Guéant, J-L

2013-11-01

Allergic IgE-mediated reactions to neuromuscular blocking agents (NMBAs) are the main cause of immediate hypersensitivity reactions in anaesthesia; their predominant occurrence in the absence of previous exposure to NMBAs suggests a risk related to environmental exposure. To investigate the prevalence of specific IgE to quaternary ammonium ions in two populations professionally exposed to quaternary ammonium compounds, in the north-eastern France. The study had a retrospective follow-up design whereby apprentices were assessed after their 2-year training period as apprentices. The professionally exposed hairdresser populations (n = 128) were compared with baker/pastry makers (n = 108) and 'non-exposed' matched control subjects (n = 379). We observed a 4.6-fold higher frequency of positive IgE against quaternary ammonium ions in hairdressers (HD), compared with baker/pastry makers (BP) and control (C) groups. The competitive inhibition of quaternary ammonium Sepharose radioimmunoassay (QAS-IgE RIA) with succinylcholine was significantly higher in HD, compared with BP and C groups, with inhibition percentage of 66.2 ± 7.4, 39.7 ± 6.0 and 43.8 ± 9.9, respectively (P < 0.001). The specific IgE against quaternary ammonium ions recognized also two compounds widely used by hairdressers, benzalkonium chloride and polyquaternium-10, in competitive inhibition of IgE RIA. When considering the whole study population, hairdresser professional exposure and total IgE > 100 kU/L were the two significant predictors of IgE-sensitization against quaternary ammonium ions in the multivariate analysis of a model that included age, sex, professional exposure, increased concentration of total IgE (IgE > 100 kU/L) and positive IgE against prevalent allergens (Phadiatop(®) ; P = 0.019 and P = 0.001, respectively). The exposure to hairdressing professional occupational factors increases IgE-sensitization to NMBAs and quaternary ammonium ion compounds used in hairdressing. Besides the pholcodine hypothesis, our study suggests that repetitive exposure to quaternary ammonium compounds used in hairdressing is a risk factor for NMBAs sensitization. © 2013 John Wiley & Sons Ltd.

Investigation of gamma ray shielding, structural and dissolution rate properties of Bi2O3-BaO-B2O3-Na2O glass system

NASA Astrophysics Data System (ADS)

Dogra, Mridula; Singh, K. J.; Kaur, Kulwinder; Anand, Vikas; Kaur, Parminder; Singh, Prabhjot; Bajwa, B. S.

2018-03-01

In the present study, quaternary system of the composition (0.45 + x) Bi2O3-(0.25 - x) BaO-0.15 B2O3-0.15 Na2O (where 0 ≤ x ≤ 0.2 mol fraction) has been prepared by using melt-quenching technique for investigation of gamma ray shielding properties. Mass attenuation coefficients and half value layer parameters have been determined experimentally at 662 keV by using 137Cs source. It has been found that experimental results of these parameters hold good agreement with theoretical values. The density, molar volume, XRD, FTIR, Raman and UV-visible studies have been used to determine structural properties of the prepared glass samples. Dissolution rate of the samples has also been measured to check their utility as long term durable glasses.

Evaluation of the gamma radiation shielding parameters of bismuth modified quaternary glass system

NASA Astrophysics Data System (ADS)

Kaur, Parminder; Singh, K. J.; Thakur, Sonika

2018-05-01

Glasses modified with heavy metal oxides (HMO) are an interesting area of research in the field of gamma-ray shielding. Bismuth modified lithium-zinc-borate glasses have been studied whereby bismuth oxide is added from 0 to 50 mol%. The gamma ray shielding properties of the glasses were evaluated at photon energy 662 keV with the help of XMuDat computer program by using the Hubbell and Seltzer database. Various gamma ray shielding parameters such as attenuation coefficient, shield thickness in terms of half and tenth value layer, effective atomic number have been studied in this work. A useful comparison of this glass system has been made with standard radiation shielding concretes viz. ordinary, barite and iron concrete. The glass samples containing 20 to 50 mol% bismuth oxide have shown better gamma ray shielding properties and hence have the potential to become good radiation absorbers.

Interaction of pulsating and spinning waves in nonadiabatic flame propagation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Booty, M.R.; Margolis, S.B.; Matkowsky, B.J.

1987-12-01

The authors consider nonadiabatic premixed flame propagation in a long cylindrical channel. A steadily propagating planar flame exists for heat losses below a critical value. It is stable provided that the Lewis number and the volumetric heat loss coefficient are sufficiently small. At critical values of these parameters, bifurcated states, corresponding to time-periodic pulsating cellular flames, emanate from the steadily propagating solution. The authors analyze the problem in a neighborhood of a multiple primary bifurcation point. By varying the radius of the channel, they split the multiple bifurcation point and show that various types of stable periodic and quasi-periodic pulsatingmore » flames can arise as secondary, tertiary, and quaternary bifurcations. Their analysis describes several types of spinning and pulsating flame propagation which have been experimentally observed in nonadiabatic flames, and also describes additional quasi-periodic modes of burning which have yet to be documented experimentally.« less

Material growth and characterization for solid state devices

NASA Technical Reports Server (NTRS)

Collis, Ward J.; Abul-Fadl, Ali; Iyer, Shanthi

1988-01-01

During the period of this research grant, the process of liquid phase electroepitaxy (LPEE) was used to grow ternary and quaternary alloy III-V semiconductor thin films. Selective area growth of InGaAs was performed on InP substrates using a patterned sputtered quartz or spin-on glass layer. The etch back and growth characteristics with respect to substrate orientation were investigated. The etch back behavior is somewhat different from wet chemical etching with respect to the sidewall profiles which are observed. LPEE was also employed to grow epitaxial layers of InGaAsP alloys on InP substrates. The behavior of Mn as an acceptor dopant was investigated with low temperature Hall coefficient and photoluminescence measurements. A metal-organic vapor phase epitaxy system was partially complete within the grant period. This atmospheric pressure system will be used to deposit III-V compound and alloy semiconductor layers in future research efforts.

Understanding the interdiffusion behavior and determining the long term stability of tungsten fiber reinforced niobium-base matrix composite systems

NASA Technical Reports Server (NTRS)

Tien, John K.

1990-01-01

The long term interdiffusional stability of tungsten fiber reinforced niobium alloy composites is addressed. The matrix alloy that is most promising for use as a high temperature structural material for reliable long-term space power generation is Nb1Zr. As an ancillary project to this program, efforts were made to assess the nature and kinetics of interphase reaction between selected beryllide intermetallics and nickel and iron aluminides.

Method for forming nuclear fuel containers of a composite construction and the product thereof

DOEpatents

Cheng, Bo-Ching; Rosenbaum, Herman S.; Armijo, Joseph S.

1984-01-01

An improved method for producing nuclear fuel containers of a composite construction having components providing therein a barrier system for resisting destructive action by volatile fission products or impurities and also interdiffusion of metal constituents, and the product thereof. The composite nuclear fuel containers of the method comprise a casing of zirconium or alloy thereof with a layer of copper overlying an oxidized surface portion of the zirconium or alloy thereof.

Orientation dependences of atomic structures in chemically heterogeneous Cu{sub 50}Ta{sub 50}/Ta glass-crystal interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Guiqin; Gao, Xiaoze; Li, Jinfu

2015-01-07

Molecular dynamics simulations based on an angular-dependent potential were performed to examine the structural properties of chemically heterogeneous interfaces between amorphous Cu{sub 50}Ta{sub 50} and crystalline Ta. Several phenomena, namely, layering, crystallization, intermixing, and composition segregation, were observed in the Cu{sub 50}Ta{sub 50} region adjacent to the Ta layers. These interfacial behaviors are found to depend on the orientation of the underlying Ta substrate: Layering induced by Ta(110) extends the farthest into Cu{sub 50}Ta{sub 50}, crystallization in the Cu{sub 50}Ta{sub 50} region is most significant for interface against Ta(100), while inter-diffusion is most pronounced for Ta(111). It turns out thatmore » the induced layering behavior is dominated by the interlayer distances of the underlying Ta layers, while the degree of inter-diffusion is governed by the openness of the Ta crystalline layers. In addition, composition segregations are observed in all interface models, corresponding to the immiscible nature of the Cu-Ta system. Furthermore, Voronoi polyhedra 〈0,5,2,6〉 and 〈0,4,4,6〉 are found to be abundant in the vicinity of the interfaces for all models, whose presence is believed to facilitate the structural transition between amorphous and body centered cubic.« less

Effects of hydrogen fugacity and confining pressure on the interdiffusion rate of NaSi-CaAl in plagioclase

NASA Astrophysics Data System (ADS)

Yund, Richard A.; Snow, Eleanour

1989-08-01

Average? values for NaSi-CaAl interdiffusion in the compositional interval from An0 to An26 have been determined at 1000°C by the method of lamellar homogenization. At 1500 MPa confining pressure (P), ? increases 1 order of magnitude (5.0×10-21 to 4.0×10-20 m2/s) for 4 orders of magnitude increase in hydrogen fugacity (0.029, Mn3O4-Mn2O3 buffer, to 197 MPa, FeO-Fe3O4 buffer). At constant hydrogen fugacity (fH2), ? increases rapidly at low pressure and becomes nearly independent of P above 1000 MPa. (For fH2 = 0.1 MPa, ? = 2.8 × 10-22 m2/s at P = 0.1 MPa, 5.0 × 10-21 at P = 500, 1.3×10-20 at P = 1000, and 1.4×10-20 at P = 1500). The dependence of ? on increasing pressure, when a hydrogen-related species is present, is believed to be due to an increase in the concentration of the structural defect associated with increase in the hydrogen impurity. In most crustal igneous rocks, which are internally buffered near quartz-fayalite-magnetite, the dependence of ? on fH2 is relatively minor compared to the effect of confining pressure.

Interdiffusion-driven synthesis of tetragonal chromium (III) oxide on BaTi O3

NASA Astrophysics Data System (ADS)

Asa, M.; Vinai, G.; Hart, J. L.; Autieri, C.; Rinaldi, C.; Torelli, P.; Panaccione, G.; Taheri, M. L.; Picozzi, S.; Cantoni, M.

2018-03-01

Interfaces play a crucial role in the study of novel phenomena emerging at heterostructures comprising metals and functional oxides. For this reason, attention should be paid to the interface chemistry, which can favor the interdiffusion of atomic species and, under certain conditions, lead to the formation of radically different compounds with respect to the original constituents. In this work, we consider Cr/BaTi O3 heterostructures grown on SrTi O3 (100) substrates. Chromium thin films (1-2 nm thickness) are deposited by molecular beam epitaxy on the BaTi O3 layer, and subsequently annealed in vacuum at temperatures ranging from 473 to 773 K. A disordered metallic layer is detected for annealing temperatures up to 573 K, whereas, at higher temperatures, we observe a progressive oxidation of chromium, which we relate to the thermally activated migration of oxygen from the substrate. The chromium oxidation state is +3 and the film shows a defective rocksalt structure, which grows lattice matched on the underlying BaTi O3 layer. One out of every three atoms of chromium is missing, producing an uncommon tetragonal phase with C r2O3 stoichiometry. Despite the structural difference with respect to the ordinary corundum α-C r2O3 phase, we demonstrate both experimentally and theoretically that the electronic properties of the two phases are, to a large extent, equivalent.

Growing Oxide Nanowires and Nanowire Networks by Solid State Contact Diffusion into Solution-Processed Thin Films.

PubMed

Glynn, Colm; McNulty, David; Geaney, Hugh; O'Dwyer, Colm

2016-11-01

New techniques to directly grow metal oxide nanowire networks without the need for initial nanoparticle seed deposition or postsynthesis nanowire casting will bridge the gap between bottom-up formation and top-down processing for many electronic, photonic, energy storage, and conversion technologies. Whether etched top-down, or grown from catalyst nanoparticles bottom-up, nanowire growth relies on heterogeneous material seeds. Converting surface oxide films, ubiquitous in the microelectronics industry, to nanowires and nanowire networks by the incorporation of extra species through interdiffusion can provide an alternative deposition method. It is shown that solution-processed thin films of oxides can be converted and recrystallized into nanowires and networks of nanowires by solid-state interdiffusion of ionic species from a mechanically contacted donor substrate. NaVO 3 nanowire networks on smooth Si/SiO 2 and granular fluorine-doped tin oxide surfaces can be formed by low-temperature annealing of a Na diffusion species-containing donor glass to a solution-processed V 2 O 5 thin film, where recrystallization drives nanowire growth according to the crystal habit of the new oxide phase. This technique illustrates a new method for the direct formation of complex metal oxide nanowires on technologically relevant substrates, from smooth semiconductors, to transparent conducting materials and interdigitated device structures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of Gold on the Microstructural Evolution and Integrity of a Sintered Silver Joint

DOE PAGES

Muralidharan, Govindarajan; Leonard, Donovan N.; Meyer, Harry M.

2017-01-05

There is a need for next-generation, high-performance power electronic packages and systems employing wide band gap devices to operate at high temperatures in automotive and electric grid applications. Sintered silver joints are currently being evaluated as an alternative to Pb-free solder joints. Of particular interest is the development of joints based on silver paste consisting of nanoscale or micron scale particles that can be processed without the application of an external pressure. Microstructural evolution at the interface of a pressureless sintered silver joint formed between a SiC die with a Ti/Ni/Au metallization and an Active Metal Brazed substrate with Agmore » metallization at 250 °C was evaluated using Scanning Electron Microscopy, X-ray microanalysis, and X-ray Photo Electron Spectroscopy. Results from Focused Ion Beam cross-sections show that during sintering, the pores in the sintered region close to the Au layer tend to be smaller and are oriented predominantly with their longer dimension oriented parallel to the interface. With further densification, this results in the alignment of small pores parallel to the interface, creating a path for easy crack propagation. Lastly, X-ray microchemical analyses results confirm interdiffusion between Au and Ag and that a region with poor mechanical strength is formed at the edge of this region of interdiffusion.« less

Compression behavior of quaternary and higher order solid-solution L1(2) trialuminides

NASA Technical Reports Server (NTRS)

Kumar, K. S.; Brown, S. A.

1992-01-01

Results from preliminary studies undertaken to evaluate the existence of single-phase L1(2) solid solutions between pairs of ternary L1(2) trialuminides are presented. Two-kilogram ingots of selected quaternary compositions were cast, homogenized and forged into pancakes; compression specimens were machined from the forgings and tested as a function of temperature. The results are compared against existing data for the ternary alloys. The ternary L1(2) trialuminides Al66Ti25Mn9, Al67Ti25Cr8, and Al22Ti8Fe3 were found to exhibit continuous solubility in one another. The quaternary Cr-Mn composition does not indicate any strength advantage over its ternary counterparts. The continuous replacement of Mn with Fe enhances the strength of the quaternary compound over the ternary Al66Ti25 Mn9.

Sex allocation and functional bias of quaternary and quinary flowers on same inflorescence in the hermaphrodite Ruta graveolens

NASA Astrophysics Data System (ADS)

Tang, Jing-Yu; Ren, Ming-Xun

2011-09-01

Intra-inflorescence variation in floral traits is important to understand the pollination function of an inflorescence and the real reproductive outputs of a plant. Ruta graveolens (Rutaceae) produce both quaternary (four petals and eight stamens) and quinary (five petals and ten stamens) flowers on the same cymes, while their pollination roles and the effects on the reproductive success remained unexplored. We experimentally examined the biomass of female versus male organs and pollen viability and stigma receptivity to explore the sex allocation patterns between the flowers. The breeding systems and reproductive outputs through either female function (seed set) or male function (pollen dispersal) were also studied for quinary and quaternary flowers to determine whether there was functional bias. The results showed that R. graveolens was protandrous, with a mixed mating system. Its stamens could slowly move one by one and only dehisce when positioning at the flower center, which could greatly enhance pollen dispersal. The first-opened quinary flower allocated significantly higher resources (dry biomass) in female organs while quaternary flowers allocated more resource in male organs. The quaternary flowers experienced higher pollen limitation in seed production but were more successful in pollen dispersal and the quinary flowers reproduced both through female and male functions. Our data suggested that quinary and quaternary flower on same inflorescence in R. graveolens functioned mainly as the sex role that most resources were allocated, which probably reflect an adaptation for floral phenology and pollination process in this plant.

Minimal erosion of Arctic alpine topography during late Quaternary glaciation

NASA Astrophysics Data System (ADS)

Gjermundsen, Endre F.; Briner, Jason P.; Akçar, Naki; Foros, Jørn; Kubik, Peter W.; Salvigsen, Otto; Hormes, Anne

2015-10-01

The alpine topography observed in many mountainous regions is thought to have formed during repeated glaciations of the Quaternary period. Before this time, landscapes had much less relief. However, the spatial patterns and rates of Quaternary exhumation at high latitudes--where cold-based glaciers may protect rather than erode landscapes--are not fully quantified. Here we determine the exposure and burial histories of rock samples from eight summits of steep alpine peaks in northwestern Svalbard (79.5° N) using analyses of 10Be and 26Al concentrations. We find that the summits have been preserved for at least the past one million years. The antiquity of Svalbard’s alpine landscape is supported by the preservation of sediments older than one million years along a fjord valley, which suggests that both mountain summits and low-elevation landscapes experienced very low erosion rates over the past million years. Our findings support the establishment of northwestern Svalbard’s alpine topography during the early Quaternary. We suggest that, as the Quaternary ice age progressed, glacial erosion in the Arctic became inefficient and confined to ice streams, and high-relief alpine landscapes were preserved by minimally erosive glacier armour.

The influence of climate on species distribution over time and space during the late Quaternary

NASA Astrophysics Data System (ADS)

Carotenuto, F.; Di Febbraro, M.; Melchionna, M.; Castiglione, S.; Saggese, F.; Serio, C.; Mondanaro, A.; Passaro, F.; Loy, A.; Raia, P.

2016-10-01

Understanding the effect of climate on the composition of communities and its change over time and space is one of the major aims in ecology and paleoecology. Herein, we tackled on this issue by studying late Quaternary large mammal paleocommunities of Eurasia. The late Quaternary was a period of strong environmental instability, especially characterized by the occurrence of the last glacial maximum (LGM). We used community phylogenetics and joint species distribution models in order to understand the factors determining paleocommunity composition in the late Quaternary. Our results support the existence of strong climatic selection operating on the LGM fauna, both through the disappearance of warm-adapted species such as Elephas antiquus, Hippopothamus amphibious, and Stephanorhinus hemitoechus, and by setting the stage for the existence of a community characterized by cold-adapted large mammals. Patterns of abundance in the fossil record, co-occurrence between species pairs, and the extent of climatic forcing on faunal composition, differ between paleocommunities, but not between extinct and extant species, which is consistent with the idea that climate change, rather than the presence of humans, exerted a major effect on the survival of the late Quaternary megafauna.

Analysis of residual products in triethylbenzylammonium chloride by HPLC. Study of the retention mechanism.

PubMed

Prieto-Blanco, M C; López-Mahía, P; Prada-Rodríguez, D

2006-04-01

The control of industrial products for minimization of their impact on the environment and human health requires the development of specific analysis methods. Information provided by these methods about toxic components, by-products, and other derivatives may also be useful to reduce the possible impact of industrial products. The studied compound in this paper, triethylbenzylammonium chloride (TEBA), is mainly used in industrial synthesis. This quaternary compound and its residual products coming from quaternization reaction (benzyl chloride, benzaldehyde, and benzyl alcohol) are analyzed by HPLC. The separation is based on control of the silanophilic contribution to TEBA retention because of the quaternary nature of this compound. The effect of the three buffers (sodium acetate, ammonium acetate, and sodium formate) and their concentrations in the chromatographic behavior of the quaternary compound is examined. The buffer cation and anion regulate TEBA retention. Also, the concentration of the quaternary compound is another parameter that had influence in some aspects of its chromatographic behavior (e.g., retention and symmetry). The proposed method is applied to TEBA synthesis along, with the formation and removal of impurities with the results compared with those obtained for the quaternary compound benzalkonium chloride.

A Systematic Investigation of Quaternary Ammonium Ions as Asymmetric Phase Transfer Catalysts. Synthesis of Catalyst Libraries and Evaluation of Catalyst Activity

PubMed Central

Denmark, Scott E.; Gould, Nathan D.; Wolf, Larry M.

2011-01-01

Despite over three decades of research into asymmetric phase transfer catalysis (APTC), a fundamental understanding of the factors that affect the rate and stereoselectivity of this important process are still obscure. This paper describes the initial stages of a long-term program aimed at elucidating the physical organic foundations of APTC employing a chemoinformatic analysis of the alkylation of a protected glycine imine with a libraries of enantiomerically enriched quaternary ammonium ions. The synthesis of the quaternary ammonium ions follows a diversity oriented approach wherein the tandem inter[4+2]/intra[3+2] cycloaddition of nitroalkenes serves as the key transformation. A two part synthetic strategy comprised of: (1) preparation of enantioenriched scaffolds and (2) development of parallel synthesis procedures is described. The strategy allows for the facile introduction of four variable groups in the vicinity of a stereogenic quaternary ammonium ion. The quaternary ammonium ions exhibited a wide range of activity and to a lesser degree enantioselectivity. Catalyst activity and selectivity are rationalized in a qualitative way based on the effective positive potential of the ammonium ion. PMID:21446721

Bactericidal Specificity and Resistance Profile of Poly(Quaternary Ammonium) Polymers and Protein-Poly(Quaternary Ammonium) Conjugates.

PubMed

Ji, Weihang; Koepsel, Richard R; Murata, Hironobu; Zadan, Sawyer; Campbell, Alan S; Russell, Alan J

2017-08-14

Antibacterial polymers are potentially powerful biocides that can destroy bacteria on contact. Debate in the literature has surrounded the mechanism of action of polymeric biocides and the propensity for bacteria to develop resistance to them. There has been particular interest in whether surfaces with covalently coupled polymeric biocides have the same mechanism of action and resistance profile as similar soluble polymeric biocides. We designed and synthesized a series of poly(quaternary ammonium) polymers, with tailorable molecular structures and architectures, to engineer their antibacterial specificity and their ability to delay the development of bacterial resistance. These linear poly(quaternary ammonium) homopolymers and block copolymers, generated using atom transfer radical polymerization, had structure-dependent antibacterial specificity toward Gram positive and negative bacterial species. When single block copolymers contained two polymer segments of differing antibacterial specificity, the polymer combined the specificities of its two components. Nanoparticulate human serum albumin-poly(quaternary ammonium) conjugates of these same polymers, synthesized via "grafting from" atom transfer radical polymerization, were strongly biocidal and also exhibited a marked decrease in the rate of bacterial resistance development relative to linear polymers. These protein-biocide conjugates mimicked the behavior of surface-presented polycationic biocides rather than their nonproteinaceous counterparts.

Catalytic Enantioselective Synthesis of Quaternary Carbon Stereocenters

PubMed Central

Quasdorf, Kyle W.; Overman, Larry E.

2015-01-01

Preface Quaternary carbon stereocenters–carbon atoms to which four distinct carbon substituents are attached–are common features of molecules found in nature. However, prior to recent advances in chemical catalysis, there were few methods available for constructing single stereoisomers of this important structural motif. Here we discuss the many catalytic enantioselective reactions developed during the past decade for synthesizing organic molecules containing such carbon atoms. This progress now makes it possible to selectively incorporate quaternary stereocenters in many high-value organic molecules for use in medicine, agriculture, and other areas. PMID:25503231

Thermodynamic Description of the Quaternary Ag-Bi-Cu-Sn System

NASA Astrophysics Data System (ADS)

Gierlotka, Wojciech

2018-01-01

Lead-free soldering is an important part of electronic devices production. New lead-free solders that replace classical Sn-37Pb solder are still under development. Thermodynamic modeling makes the development process faster, cheaper and more environmentally friendly due to predictions of phases stabilities and phases transformations. In this work, the thermodynamic description of quaternary Ag-Bi-Cu-Sn system is presented. The thermodynamic assessment of promising lead-free quaternary solder was prepared using the Calphad approach. A good agreement between available experimental data and calculation was found.

Quaternary ammonium promoted ultra selective and sensitive fluorescence detection of fluoride ion in water and living cells.

PubMed

Li, Long; Ji, Yuzhuo; Tang, Xinjing

2014-10-21

Highly selective and sensitive fluorescent probes with a quaternary ammonium moiety have been rationally designed and developed for fast and sensitive fluorescence detection of fluoride ion (F(-) from NaF, not TBAF) in aqueous solution and living cells. With the sequestration effect of quaternary ammonium, the detection time was less than 2 min and the detection limit of fluoride ion was as low as 0.57 ppm that is among the lowest detection limits in aqueous solutions of many fluoride fluorescence probes in the literature.

Spatiotemporal analysis of Quaternary normal faults in the Northern Rocky Mountains, USA

NASA Astrophysics Data System (ADS)

Davarpanah, A.; Babaie, H. A.; Reed, P.

2010-12-01

The mid-Tertiary Basin-and-Range extensional tectonic event developed most of the normal faults that bound the ranges in the northern Rocky Mountains within Montana, Wyoming, and Idaho. The interaction of the thermally induced stress field of the Yellowstone hot spot with the existing Basin-and-Range fault blocks, during the last 15 my, has produced a new, spatially and temporally variable system of normal faults in these areas. The orientation and spatial distribution of the trace of these hot-spot induced normal faults, relative to earlier Basin-and-Range faults, have significant implications for the effect of the temporally varying and spatially propagating thermal dome on the growth of new hot spot related normal faults and reactivation of existing Basin-and-Range faults. Digitally enhanced LANDSAT 7 Enhanced Thematic Mapper Plus (ETM+) and Landsat 4 and 5 Thematic Mapper (TM) bands, with spatial resolution of 30 m, combined with analytical GIS and geological techniques helped in determining and analyzing the lineaments and traces of the Quaternary, thermally-induced normal faults in the study area. Applying the color composite (CC) image enhancement technique, the combination of bands 3, 2 and 1 of the ETM+ and TM images was chosen as the best statistical choice to create a color composite for lineament identification. The spatiotemporal analysis of the Quaternary normal faults produces significant information on the structural style, timing, spatial variation, spatial density, and frequency of the faults. The seismic Quaternary normal faults, in the whole study area, are divided, based on their age, into four specific sets, which from oldest to youngest include: Quaternary (>1.6 Ma), middle and late Quaternary (>750 ka), latest Quaternary (>15 ka), and the last 150 years. A density map for the Quaternary faults reveals that most active faults are near the current Yellowstone National Park area (YNP), where most seismically active faults, in the past 1.6 my, are located. The GIS based autocorrelation method, applied to the trace orientation, length, frequency, and spatial distribution for each age-defined fault set, revealed spatial homogeneity for each specific set. The results of the method of Moran`sI and Geary`s C show no spatial autocorrelation among the trend of the fault traces and their location. Our results suggest that while lineaments of similar age define a clustered pattern in each domain, the overall distribution pattern of lineaments with different ages seems to be non-uniform (random). The directional distribution analysis reveals a distinct range of variation for fault traces of different ages (i.e., some displaying ellipsis behavior). Among the Quaternary normal fault sets, the youngest lineament set (i.e., last 150 years) defines the greatest ellipticity (eccentricity) and the least lineaments distribution variation. The frequency rose diagram for the entire Quaternary normal faults, shows four major modes (around 360o, 330o, 300o, and 270o), and two minor modes (around 235 and 205).

Coupling Geophysical, Geotechnical and Stratigraphic Data to Interpret the Genesis of Mega-Scale-Glacial-Lineations on the Yermak Plateau, Arctic Ocean

NASA Astrophysics Data System (ADS)

O'Regan, M. A.; Jakobsson, M.; Kirchner, N.; Dowdeswell, J. A.; Hogan, K.

2010-12-01

The recent collection and analysis of multi-beam bathymetry data has revealed Mega-Scale Glacial Lineations (MSGL) in up to 600 m present water depth on the Yermak Plateau (Dowdeswell et al., 2010; Jakobsson et al., 2010). This evidence for large-scale ice grounding in the region supports previous interpretations from side-scan sonar, high-resolution subbottom and multi-channel seismic data. Detailed integration with regional subbottom data illustrates that the formation of the MSGL occurred in the late Quaternary, around MIS6. This event is distinct from a middle Quaternary ice grounding in the same region, that was first recognized by the transition into heavily overconsolidated sediments at ~20 mbsf at Ocean Drilling Program Site 910. While the middle Quaternary ice grounding left an easily recognizable imprint on the geotechnical properties of the sediments, the imprint from the late Quaternary event is far subtler, and not formerly recognized by analysis of sediments from Site 910. Furthermore, stratigraphic information indicates that neither event was associated with significant erosion, implying that the observed stress state of the sediments arose from ice-loading. Coupled with the orientation of the late Quaternary MSGL, the available evidence argues against an active ice-stream being responsible for their formation, and that they were more likely formed by a very large tabular iceberg traversing the ridge. This lends considerable support to the argument that MSGL-like features are not exclusively associated with fast flowing ice-streams. References Jakobsson, M., et al., An Arctic Ocean iceshelf during MIS 6 constrained by new geophysical and geological data. Quaternary Science Reviews (2010), doi:10.1016/j.quascirev.2010.03.015. Dowdeswell, J. A., et al., High-resolution geophysical observations of the Yermak Plateau and northern Svalbard margin: implications for ice-sheet grounding and deep-keeled icebergs. Quaternary Science Reviews (2010), doi:10.1016/j.quascirev.2010.06.002

Map and data for Quaternary faults and folds in Washington state

USGS Publications Warehouse

Lidke, David J.; Johnson, Samuel Y.; McCrory, Patricia A.; Personius, Stephen F.; Nelson, Alan R.; Dart, Richard L.; Bradley, Lee-Ann; Haller, Kathleen M.; Machette, Michael N.

2004-01-01

The map shows faults and folds in Washington State that exhibit evidence of Quaternary deformation and includes data on timing of most recent movement, sense of movement, slip rate, and continuity of surface expression.

A solution-processed quaternary oxide system obtained at low-temperature using a vertical diffusion technique

PubMed Central

Yoon, Seokhyun; Kim, Si Joon; Tak, Young Jun; Kim, Hyun Jae

2017-01-01

We report a method for fabricating solution-processed quaternary In-Ga-Zn-O (IGZO) thin-film transistors (TFTs) at low annealing temperatures using a vertical diffusion technique (VDT). The VDT is a deposition process for spin-coating binary and ternary oxide layers consecutively and annealing at once. With the VDT, uniform and dense quaternary oxide layers were fabricated at lower temperatures (280 °C). Compared to conventional IGZO and ternary In-Zn-O (IZO) thin films, VDT IGZO thin film had higher density of the metal-oxide bonds and lower density of the oxygen vacancies. The field-effect mobility of VDT IGZO TFT increased three times with an improved stability under positive bias stress than IZO TFT due to the reduction in oxygen vacancies. Therefore, the VDT process is a simple method that reduces the processing temperature without any additional treatment for quaternary oxide semiconductors with uniform layers. PMID:28230088

A solution-processed quaternary oxide system obtained at low-temperature using a vertical diffusion technique

NASA Astrophysics Data System (ADS)

Yoon, Seokhyun; Kim, Si Joon; Tak, Young Jun; Kim, Hyun Jae

2017-02-01

We report a method for fabricating solution-processed quaternary In-Ga-Zn-O (IGZO) thin-film transistors (TFTs) at low annealing temperatures using a vertical diffusion technique (VDT). The VDT is a deposition process for spin-coating binary and ternary oxide layers consecutively and annealing at once. With the VDT, uniform and dense quaternary oxide layers were fabricated at lower temperatures (280 °C). Compared to conventional IGZO and ternary In-Zn-O (IZO) thin films, VDT IGZO thin film had higher density of the metal-oxide bonds and lower density of the oxygen vacancies. The field-effect mobility of VDT IGZO TFT increased three times with an improved stability under positive bias stress than IZO TFT due to the reduction in oxygen vacancies. Therefore, the VDT process is a simple method that reduces the processing temperature without any additional treatment for quaternary oxide semiconductors with uniform layers.

Mössbauer and XRD study of novel quaternary Sn-Fe-Co-Ni electroplated alloy

NASA Astrophysics Data System (ADS)

Kuzmann, E.; Sziráki, L.; Stichleutner, S.; Homonnay, Z.; Lak, G. B.; El-Sharif, M.; Chisholm, C. U.

2017-11-01

Constant current electrochemical deposition technique was used to obtain quaternary alloys of Sn-Fe-Co-Ni from a gluconate electrolyte, which to date have not been reported in the literature. For the characterization of electroplated alloys, 57Fe and 119Sn Conversion Electron Mössbauer Spectroscopy (CEMS), XRD and SEM/EDAX were used. XRD revealed the amorphous character of the novel Sn-Fe-Co-Ni electrodeposited alloys. 57Fe Mössbauer spectrum of quaternary deposit with composition of 37.0 at% Sn, 38.8 at% Fe, 16.8 at% Co and 7.4 at% Ni displayed a magnetically split sextet (B = 28.9T) with broad lines typical of iron bearing ferromagnetic amorphous alloys. Magnetically split 119Sn spectra reflecting a transferred hyperfine field (B = 2.3T) were also observed. New quaternary Sn-Fe-Co-Ni alloys were successfully prepared.

A solution-processed quaternary oxide system obtained at low-temperature using a vertical diffusion technique.

PubMed

Yoon, Seokhyun; Kim, Si Joon; Tak, Young Jun; Kim, Hyun Jae

2017-02-23

We report a method for fabricating solution-processed quaternary In-Ga-Zn-O (IGZO) thin-film transistors (TFTs) at low annealing temperatures using a vertical diffusion technique (VDT). The VDT is a deposition process for spin-coating binary and ternary oxide layers consecutively and annealing at once. With the VDT, uniform and dense quaternary oxide layers were fabricated at lower temperatures (280 °C). Compared to conventional IGZO and ternary In-Zn-O (IZO) thin films, VDT IGZO thin film had higher density of the metal-oxide bonds and lower density of the oxygen vacancies. The field-effect mobility of VDT IGZO TFT increased three times with an improved stability under positive bias stress than IZO TFT due to the reduction in oxygen vacancies. Therefore, the VDT process is a simple method that reduces the processing temperature without any additional treatment for quaternary oxide semiconductors with uniform layers.

Principles of assembly reveal a periodic table of protein complexes.

PubMed

Ahnert, Sebastian E; Marsh, Joseph A; Hernández, Helena; Robinson, Carol V; Teichmann, Sarah A

2015-12-11

Structural insights into protein complexes have had a broad impact on our understanding of biological function and evolution. In this work, we sought a comprehensive understanding of the general principles underlying quaternary structure organization in protein complexes. We first examined the fundamental steps by which protein complexes can assemble, using experimental and structure-based characterization of assembly pathways. Most assembly transitions can be classified into three basic types, which can then be used to exhaustively enumerate a large set of possible quaternary structure topologies. These topologies, which include the vast majority of observed protein complex structures, enable a natural organization of protein complexes into a periodic table. On the basis of this table, we can accurately predict the expected frequencies of quaternary structure topologies, including those not yet observed. These results have important implications for quaternary structure prediction, modeling, and engineering. Copyright © 2015, American Association for the Advancement of Science.

Tertiary and Quaternary Research with Remote Sensing Methods

NASA Technical Reports Server (NTRS)

Conel, J. E.

1985-01-01

Problems encountered in mapping the Quaternary section of the Wind River Region using remote sensing methods are discussed. Analysis of the stratigraphic section is a fundamental aspect of the geologic study of sedimentary basins. Stratigraphic analysis of post-Cretaceous rocks in the Wind River Basin encounters problems of a distinctly different character from those involved in studying the pre-Cretaceous section. The interior of the basin is predominantly covered by Tertiary and Quaternary sediments. These rocks, except on the basin margin to the north, are mostly flat lying or gently dipping. The Tertiary section consists of sandstones, siltstones, and tuffaceous sediments, some variegated, but in general poorly bedded and of great lithologic similarity. The Quaternary sediments consist of terrace, fan, and debris tongue deposits, unconsolidated alluvium occupying the bottoms of modern watercourses, deposits of eolian origin and tufa. Terrace and fan deposits are compositionally diverse and reflect the lithologic diversity of the source terranes.

Superconductive articles including cerium oxide layer

DOEpatents

Wu, X.D.; Muenchausen, R.E.

1993-11-16

A ceramic superconductor comprising a metal oxide substrate, a ceramic high temperature superconductive material, and a intermediate layer of a material having a cubic crystal structure, said layer situated between the substrate and the superconductive material is provided, and a structure for supporting a ceramic superconducting material is provided, said structure comprising a metal oxide substrate, and a layer situated over the surface of the substrate to substantially inhibit interdiffusion between the substrate and a ceramic superconducting material deposited upon said structure. 7 figures.

Proceedings of the Workshop on Compound Semiconductor Devices and Integrated Circuits (13th) Held in Cabourg, France on 10-12 May 1989

DTIC Science & Technology

1989-05-12

USA Resonant tunneling transistors and New III-V memory devices for new circuit architectures with reduced complexity F. Capasso, Bell. Murray Hill...the evaporation, or by selective oxidation of As, leaving metallic Ga clusters and b) the interdiffusive deterioration of metal contacts on GaAs...VEB (My) Resonant Tunneling Transistors and New III-V Memory Devices for New Circuit Architectures with Reduced Complexity . Invited: F. Capasso

BAKABLE ULTRA-HIGH VACUUM VALVE

DOEpatents

Mark, J.T.; Gantz, I.H.

1962-07-10

S>This patent relates to a valve useful in applications involving successively closing and opening a communication between a chamber evacuated to an ultra-high vacuum condition of the order of 10/sup -10/ millimeters of mercury and another chamber or the ambient. The valve is capable of withstanding extended baking at 450 deg C and repeated opening and closing without repiacement of the valve seat (approximately 200 cycle limit). The seal is formed by mutual interdiffusion weld, coerced by a pneumatic actuator. (AEC)

Programmable and electrically controllable light scattering from surface-polymer stabilized liquid crystals.

PubMed

Bédard-Arcand, Jean-Philippe; Galstian, Tigran

2012-08-01

We report the creation and study of a polarization independent light scattering material system based on surface-polymer stabilized liquid crystals. Originally isotropic cell substrates with thin nonpolymerized reactive mesogen layers are used for the alignment of pure nonreactive nematic liquid crystals. The partial interdiffusion of the two materials followed by the application of orienting external electric and magnetic fields and the photo polymerization of the reactive mesogen allow us the control of electro-optic scattering properties of obtained cells.

Ultrafast time-resolved spectroscopy of lead halide perovskite films

NASA Astrophysics Data System (ADS)

Idowu, Mopelola A.; Yau, Sung H.; Varnavski, Oleg; Goodson, Theodore

2015-09-01

Recently, lead halide perovskites which are organic-inorganic hybrid structures, have been discovered to be highly efficient as light absorbers. Herein, we show the investigation of the excited state dynamics and emission properties of non-stoichiometric precursor formed lead halide perovskites grown by interdiffusion method using steady-state and time-resolved spectroscopic measurements. The influence of the different ratios of the non-stoichiometric precursor solution was examined. The observed photoluminescence properties were correlated with the femtosecond transient absorption measurements.

Superconductive articles including cerium oxide layer

DOEpatents

Wu, Xin D.; Muenchausen, Ross E.

1993-01-01

A ceramic superconductor comprising a metal oxide substrate, a ceramic high temperature superconductive material, and a intermediate layer of a material having a cubic crystal structure, said layer situated between the substrate and the superconductive material is provided, and a structure for supporting a ceramic superconducting material is provided, said structure comprising a metal oxide substrate, and a layer situated over the surface of the substrate to substantially inhibit interdiffusion between the substrate and a ceramic superconducting material deposited upon said structure.

Missing in Action? Evaluating the Putative Absence of Impacts by Large Asteroids and Comets during the Quaternary Period

NASA Astrophysics Data System (ADS)

Masse, W.; Weaver, R.; Abbott, D.; Gusiakov, V.; Bryant, E.

The Quaternary period represents the interval of oscillating climatic extremes (glacial and interglacial periods) beginning about 2.6 million years ago to the present. Based on modeling by the Near Earth Object (NEO) community of planetary scientists, the known and validated record of Quaternary impact on Earth by comets and asteroids is seemingly depauperate in terms of larger impactors of 10,000+ Mt (roughly equal to or larger than about 500 m in diameter). Modeling suggests that an average of between 2-3 and perhaps as many as 5 globally catastrophic (ca. 1,000,000+ Mt) impacts by asteroids and comets could have occurred on Earth during this period of time, each having catastrophic regional environmental effects and moderate to severe continental and global effects. A slightly larger number of substantive but somewhat less than globally catastrophic impacts in the 10,000-100,000 Mt range would also be predicted to have occurred during the Quaternary. However, databases of validated impact structures on Earth, contain only two examples of Quaternary period impacts in the 10,000-100,000 Mt range (Zhamanshin, Bosumtwi), dating to around a million years ago, while no examples of Quaternary period globally catastrophic impact structures have been yet identified. In addition, all of the 27 validated Quaternary period impact structures are terrestrial--no Quaternary period oceanic impacts have been yet validated. Two likely globally catastrophic probable oceanic impacts events, Eltanin (ca. 1,000,000 Mt at around 2.5 mya), and that associated with the Australasian tektite strewn field (> 1,000,000 Mt at around 0.8 mya), are known due to their debris fields for which craters have not yet been identified and validated. These and the 8-km diameter Bolivian Iturralde candidate impact structure (ca. 10,000 Mt at around 20 kya) round out our list of likely large Quaternary impact structures. This suggests that one or more Quaternary period globally catastrophic impacts and several events in the 10,000-100,000 Mt range occurred in oceanic settings and have not yet been identified. At issue here is the default position of the NEO community that no large impacts have occurred during the past 15,000 years and that there is little evidence for human death by impacts during the past 5000 years of recorded history. This bias, deriving largely from reliance on stochastic models and by selectively ignoring physical, anthropological, and archaeological evidence in support of such impacts, is apparent in the messages being given to the media and general public, and in the general lack of grant support and other assistance to scientists and scholars wishing to conduct fieldwork on impacts that may date to the past 15,000 years. Such a position has a chilling effect on what should otherwise be an important arena of inquiry into the risks and effects of cosmic impact on human society. It potentially limits advancement in our understanding of the recent record and flux of cosmic impact, and diverts attention away from significant research questions such as the possible role of impact in Quaternary period climate change and biological and cultural evolution and process. LA-UR-07-2526.

Quaternary tectonic evolution of the Pamir-Tian Shan convergence zone, Northwest China

NASA Astrophysics Data System (ADS)

Thompson Jobe, Jessica Ann; Li, Tao; Chen, Jie; Burbank, Douglas W.; Bufe, Aaron

2017-12-01

The Pamir-Tian Shan collision zone in the western Tarim Basin, northwest China, formed from rapid and ongoing convergence in response to the Indo-Eurasian collision. The arid landscape preserves suites of fluvial terraces crossing structures active since the late Neogene that create fault and fold scarps recording Quaternary deformation. Using geologic and geomorphic mapping, differential GPS surveys of deformed terraces, and optically stimulated luminescence dating, we create a synthesis of the active structures that delineate the timing, rate, and migration of Quaternary deformation during ongoing convergence. New deformation rates on eight faults and folds, when combined with previous studies, highlight the spatial and temporal patterns of deformation within the Pamir-Tian Shan convergence zone during the Quaternary. Terraces spanning 130 to 8 ka record deformation rates between 0.1 and 5.6 mm/yr on individual structures. In the westernmost Tarim Basin, where the Pamir and Tian Shan are already juxtaposed, the fastest rates occur on actively deforming structures at the interface of the Pamir-Tian Shan orogens. Farther east, as the separation between the Pamir-Tian Shan orogens increases, the deformation has not been concentrated on a single structure, but rather has been concurrently distributed across a zone of faults and folds in the Kashi-Atushi fold-and-thrust belt and along the NE Pamir margin, where shortening rates vary on individual structures during the Quaternary. Although numerous structures accommodate the shortening and the locus of deformation shifts during the Quaternary, the total shortening across the western Tarim Basin has remained steady and approximately matches the current geodetic rate of 6-9 mm/yr.

Diversification dynamics, species sorting, and changes in the functional diversity of marine benthic gastropods during the Pliocene-Quaternary at temperate western South America.

PubMed

Rivadeneira, Marcelo M; Nielsen, Sven N

2017-01-01

Functional diversity based on species traits is a powerful tool to investigate how changes in species richness and composition affect ecosystem functioning. However, studies aimed at understanding changes in functional diversity over large temporal and spatial scales are still scant. Here we evaluate the combined effect of diversification and species sorting on functional diversity of fossil marine gastropods during the Pliocene-Quaternary transition in the Pacific coast of South America. We analyzed a total of 172 species in 29 Pliocene and 97 Quaternary sites. Each species was characterized according to six functional traits: body size, feeding type, mobility, attachment, life-habit, and larval mode. Functional diversity was estimated according to four indexes (functional richness, evenness, divergence and dispersion) based on functional traits measured. Extrapolated species richness showed a slight yet not significant decrease from the Pliocene to the Quaternary despite the fact that a large faunal turnover took place; furthermore, a large extinction of Pliocene species (61-76%) was followed by a high pulse of appearances (49-56%) during the Quaternary. Three out of four indices of functional diversity (evenness, divergence and dispersion) increased significantly towards the Quaternary which is more than expected under a random turnover of species. The increase in functional diversity is associated with a loss of large-sized carnivore forms, which tended to be replaced by small-sized grazers. Hence, this trait-selective species turnover, even in the absence of significant changes in species richness, likely had a large effect and has shaped the functional diversity of present-day assemblages.

Tetracalcium phosphate composite containing quaternary ammonium dimethacrylate with antibacterial properties

PubMed Central

Cheng, Lei; Weir, Michael D.; Limkangwalmongkol, Penwadee; Hack, Gary D.; Xu, Hockin H. K.; Chen, Qianming; Zhou, Xuedong

2012-01-01

Tooth caries is a carbohydrate-modified bacterial infectious disease, and recurrent caries is a frequent reason for restoration failure. The objective of this study was to develop a novel antibacterial composite using tetracalcium phosphate (TTCP) fillers and bis(2-methacryloyloxy-ethyl) dimethyl-ammonium bromide, which is a quaternary ammonium dimethacrylate (QADM). QADM was synthesized using 2-(N,N-dimethylamino)ethyl methacrylate and 2-bromoethyl methacrylate and incorporated into a resin. The resin was filled with 40% TTCP and 30% glass particles. The following QADM mass fractions in the composite were tested: 0%, 6%, 12%, and 18%. Streptococcus mutans biofilms were formed on the composites and the colony-forming units (CFUs), metabolic activity, and lactic acid production were measured. The TTCP-QADM composite had flexural strength and elastic modulus similar to those of two commercial composites (p > 0.1). Increasing the QADM content in TTCP composite greatly decreased the bacteria growth and biofilm matrix production. There were significantly more dead bacteria with increasing QADM content. TTCP composite containing 18% QADM had biofilm CFU, metabolic activity, and acid production about half of those without QADM. Inversely linear relationships were established between QADM mass fraction and S. mutans biofilm CFU, metabolic activity, and acid production, with correlation coefficients R2 ≥ 0.98. In conclusion, TTCP-QADM composites were developed and the effect of QADM mass fraction on the antibacterial properties of the composite was determined for the first time. The novel TTCP-QADM composites possessing a strong antibacterial capability, together with calcium phosphate ion release and good mechanical properties, are promising for dental restorations to reduce biofilm growth and recurrent caries. PMID:22190356

Estimation of F-3 and F-4 knock-limited performance ratings for ternary and quaternary blends containing triptane or other high-antiknock aviation-fuel blending agents

NASA Technical Reports Server (NTRS)

Barnett, Henry C

1948-01-01

Charts are presented that permit the estimation of F-3 and F-4 knock-limited performance ratings for certain ternary and quaternary fuel blends. Ratings for various ternary and quaternary blends estimated from these charts compare favorably with experimental F-3 and F-4 ratings. Because of the unusual behavior of some of the aromatic blends in the F-3 engine, the charts for aromatic-paraffinic blends are probably less accurate than the charts for purely paraffinic blends.

Stereoselective preparation of quaternary 2-vinyl sphingosines and ceramides and their effect on basal sphingolipid metabolism.

PubMed

Calderón, Raquel; Mercadal, Nerea; Abad, José Luis; Ariza, Xavier; Delgado, Antonio; Garcia, Jordi; Rodríguez, Aleix; Fabriàs, Gemma

2017-06-01

The dicyclohexylborane-mediated addition of allene 1 to (E)-2-tridecenal affords a quaternary protected 2-amino-2-vinyl-1,3-diol in good yield as a single diastereomer. This compound is readily transformed into the four stereoisomers of the quaternary (E)-2-vinyl analogs of sphingosine. The metabolic fate and the effect of these compounds on the basal sphingolipid metabolism in human A549 lung adenocarcinoma cells has been studied, together with the ceramide analog of the most relevant vinylsphingosine derivative. Copyright © 2017 Elsevier B.V. All rights reserved.

Using Generic and Pesticide DRASTIC GIS-based models for vulnerability assessment of the Quaternary aquifer at Sohag, Egypt

NASA Astrophysics Data System (ADS)

Ahmed, Ayman A.

2009-07-01

Groundwater resources in the Sohag area, Egypt are currently threatened by contamination from municipal and industrial activities, and agricultural pesticides. To cope with the growing population, there has been development in the desert zone on both sides of the Nile Valley including agricultural investment areas, wastewater disposal sites, new urban areas, and industry. Use of agrochemicals in the old cultivated and newly reclaimed lands and wastewater disposal sites in the study area represent the most hazardous contamination sources. Prevention of contamination and management of the Quaternary aquifer is urgently needed. To address vulnerability assessment of the Quaternary aquifer, the Generic and Pesticide DRASTIC GIS-based models have been used. The Generic DRASTIC index ranged between 94 and 189, and the Pesticide DRASTIC index ranged between 94 and 226. The results showed that 83% of the Quaternary aquifer is characterized by the high and very high vulnerability classes to municipal, industrial and agricultural pesticides contamination. It was found that nearly all the development projects are located in the very high vulnerability class areas. Management alternatives for the Quaternary aquifer may be improved by application of these models, allowing sensitive groundwater sources to be protected for continuing use in the future.

Water quality of the Quaternary and Ada-Vamoosa aquifers on the Osage Reservation, Osage County, Oklahoma, 1997

USGS Publications Warehouse

Abbott, Marvin M.

2000-01-01

The project was to provide information on the quality of ground water from rural-domestic-water wells within the Osage Reservation and compare the water-quality to proximity to oil wells. About 38,500 oil wells have been drilled in the Reservation since drilling began in 1896. About 1,480 square miles or 64 percent of the Reservation is within a quarter mile of an oil well. The unconfined Quaternary sand aquifer covers about 315 square miles or about 14 percent of the Reservation and the confined Ada-Vamoosa sandstone aquifer covers about 800 square miles or about 35 percent of the Reservation. Fifty-eight percent of the Quaternary aquifer and 69 percent of the outcrop area of the Ada-Vamoosa aquifer are within a quarter mile of an oil well . One hundred twenty domestic ground-water wells were sampled from the Quaternary and Ada-Vamoosa aquifers. Forty-nine percent of the Reservation is underlain by the aquifers. Ground-water quality is good on most of the Reservation, but the use of domestic water-supply wells tend to minimize water-quality problems. Existing water-supply wells commonly are located in areas that produce usable volumes of potable water. Several constituents in samples from the Ada-Vamoosa-aquifer within a quarter mile of an oil well were significantly greater than from the aquifer not near oil wells. The constituents include specific conductance, dissolved solids, sodium, sulfate, chloride, bromide, and silica. These ions are probably derived from brine water. In the Ada-Vamoosa aquifer subgroups, 57 percent of the samples near oil wells and 24 percent of the samples not near oil wells had dissolved-solids concentrations greater than 500 milligrams per liter. The water quality in the Quaternary and Ada-Vamoosa aquifers is similar in areas where no oil wells have been drilled but is significantly different for several constituents. Median concentrations of major constituents from the Ada-Vamoosa aquifer not near oil wells were less than or equal to values from the Quaternary aquifer. Sixty-four percent of the water-quality samples from the Quaternary and 51 percent from the Ada-Vamoosa aquifers have dissolved-solids concentrations less than the secondary drinking water regulations of 500 milligrams per liter. Fifty-nine percent of the aquifer samples in the Quaternary aquifer subgroups not near oil wells and 70 percent of the samples near oil wells had dissolved solids less than 500 milligrams per liter. Areas in the Ada-Vamoosa aquifer near Hominy, Pershing, and Hula Lake have dissolved-solids concentrations greater than the secondary drinking water regulations. Water-quality samples from the Quaternary aquifer in these areas also have dissolved-solids concentrations greater than 500 milligrams per liter.

40 CFR 721.655 - Ethoxylated alkyl quaternary ammonium compound.

Code of Federal Regulations, 2010 CFR

2010-07-01

...) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.655 Ethoxylated alkyl quaternary ammonium compound. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically...

Ternary and Quaternary Composition Diagrams: An Overview of the Subject.

ERIC Educational Resources Information Center

MacCarthy, Patrick

1983-01-01

Reviews graphical methods for representing ternary and quaternary systems, focusing on use of triangular composition diagrams. Examines some of the relevant geometry of triangles in general, showing that right isosceles triangles possess some very advantageous features for representing ternary systems. (JN)

Solubility limits in quaternary SnTe-based alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siol, Sebastian; Holder, Aaron; Ortiz, Brenden R.

2017-01-01

A combined theoretical and experimental approach was used to determine the equilibrium as well as non-equilibrium solubility lines in the quaternary Sn 1-yMn yTe 1-xSe xalloy space, revealing a large area of accessible metastable phase space.

Y0.08Sr0.88TiO3-CeO2 composite as a diffusion barrier layer for stainless-steel supported solid oxide fuel cell

NASA Astrophysics Data System (ADS)

Kim, Kun Joong; Kim, Sun Jae; Choi, Gyeong Man

2016-03-01

A new diffusion barrier layer (DBL) is proposed for solid oxide fuel cells (SOFCs) supported on stainless-steel where DBL prevents inter-diffusion of atoms between anode and stainless steel (STS) support during fabrication and operation of STS-supported SOFCs. Half cells consisting of dense yttria-stabilized zirconia (YSZ) electrolyte, porous Ni-YSZ anode layer, and ferritic STS support, with or without Y0.08Sr0.88TiO3-CeO2 (YST-CeO2) composite DBL, are prepared by tape casting and co-firing at 1250 and 1350 °C, respectively, in reducing (H2) atmosphere. The porous YST-CeO2 layer (t ∼ 60 μm) blocks inter-diffusion of Fe and Ni, and captures the evaporated Cr during cell fabrication (1350 °C). The cell with DBL and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode achieved a maximum power density of ∼220 mW cm-2 which is stable at 700 °C. In order to further improve the power performance, Ni coarsening in anode during co-firing must be prevented or alternative anode which is resistive to coarsening is suggested. This study demonstrates that the new YST-CeO2 layer is a promising as a DBL for stainless-steel-supported SOFCs fabricated with co-firing process.

Correlative tomography at the cathode/electrolyte interfaces of solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Wankmüller, Florian; Szász, Julian; Joos, Jochen; Wilde, Virginia; Störmer, Heike; Gerthsen, Dagmar; Ivers-Tiffée, Ellen

2017-08-01

This paper introduces a correlative tomography technique. It visualizes the spatial organization of primary and secondary phases at the interface of La0.58Sr0.4Co0.2Fe0.8O3-δ cathode/10 mol% Gadolinia doped Ceria/8 mol% Yttria stabilized Zirconia electrolyte. It uses focused ion beam/scanning electron microscope tomography (FIB/SEM), and combines data sets from Everhart-Thornley and Inlens detector differentiating four primary and two secondary material phases. In addition, grayscale information is correlated to elemental distribution gained by energy dispersive X-ray spectroscopy in a scanning transmission electron microscope. Interdiffusion of GDC into YSZ and SrZrO3 as secondary phases depend (in both amount and spatial organization) on the varied co-sintering temperature of the GDC/YSZ electrolyte. The ion-blocking SrZrO3 forms a continuous layer on top of the temperature-dependent GDC/YSZ interdiffusion zone (ID) at and below a co-sintering temperature of 1200 °C; above it becomes intermittent. 2D FIB/SEM images of primary and secondary phases at 1100, 1200, 1300 and 1400 °C were combined with a 3D FIB/SEM reconstruction (1300 °C). This reveals that ;preferred; oxygen ion transport pathways from the LSCF cathode through GDC and the ID into the YSZ electrolyte only exist in samples sintered above 1200 °C. The applied correlative technique expands our understanding of this multiphase cathode/electrolyte interface region.

Interfacial characterization of ceramic core materials with veneering porcelain for all-ceramic bi-layered restorative systems.

PubMed

Tagmatarchis, Alexander; Tripodakis, Aris-Petros; Filippatos, Gerasimos; Zinelis, Spiros; Eliades, George

2014-01-01

The aim of the study was to characterize the elemental distribution at the interface between all-ceramic core and veneering porcelain materials. Three groups of all-ceramic cores were selected: A) Glass-ceramics (Cergo, IPS Empress, IPS Empress 2, e-max Press, Finesse); B) Glass-infiltrated ceramics (Celay Alumina, Celay Zirconia) and C) Densely sintered ceramics (Cercon, Procera Alumina, ZirCAD, Noritake Zirconia). The cores were combined with compatible veneering porcelains and three flat square test specimens were produced for each system. The core-veneer interfaces were examined by scanning electron microscopy and energy dispersive x-ray microanalysis. The glass-ceramic systems showed interfacial zones reach in Si and O, with the presence of K, Ca, Al in core and Ca, Ce, Na, Mg or Al in veneer material, depending on the system tested. IPS Empress and IPS Empress 2 demonstrated distinct transitional phases at the core-veneer interface. In the glassinfiltrated systems, intermixing of core (Ce, La) with veneer (Na, Si) elements occurred, whereas an abrupt drop of the core-veneer elemental concentration was documented at the interfaces of all densely sintered ceramics. The results of the study provided no evidence of elemental interdiffusion at the core-veneer interfaces in densely sintered ceramics, which implies lack of primary chemical bonding. For the glass-containing systems (glassceramics and glass-infiltrated ceramics) interdiffusion of the glass-phase seems to play a critical role in establishing a primary bonding condition between ceramic core and veneering porcelain.

Concentration Gradient Immunoassay I. A Rapid Immunoassay Based on Interdiffusion and Surface Binding in a Microchannel

PubMed Central

Nelson, Kjell E.; Foley, Jennifer O.; Yager, Paul

2008-01-01

We describe a novel microfluidic immunoassay method based on the diffusion of a small molecule analyte into a parallel-flowing stream containing cognate antibody. This interdiffusion results in a steady-state gradient of antibody binding site occupancy transverse to convective flow. In contrast to the diffusion immunoassay (Hatch et al. Nature Biotechnology,19:461−465 (2001)), this antibody occupancy gradient is interrogated by a sensor surface coated with a functional analog of the analyte. Antibodies with at least one unoccupied binding site may specifically bind to this functionalized surface, leading to a quantifiable change in surface coverage by the antibody. SPR imaging is used to probe the spatial distribution of antibody binding to the surface and, therefore, the outcome of the assay. We show that the pattern of antibody binding to the SPR sensing surface correlates with the concentration of a model analyte (phenytoin) in the sample stream. Using an inexpensive disposable microfluidic device, we demonstrate assays for phenytoin ranging in concentration from 75 to 1000 nM in phosphate buffer. At a total volumetric flow rate of 90 nL/sec, the assays are complete within 10 minutes. Inclusion of an additional flow stream on the side of the antibody stream opposite to that of the sample enables simultaneous calibration of the assay. This assay method is suitable for rapid quantitative detection of low-molecular weight analytes for point-of-care diagnostic instrumentation. PMID:17437332

Pleistocene land bridges act as semipermeable agents of avian gene flow in Wallacea.

PubMed

Garg, Kritika M; Chattopadhyay, Balaji; Wilton, Peter R; Malia Prawiradilaga, Dewi; Rheindt, Frank E

2018-08-01

Cyclical periods of global cooling have been important drivers of biotic differentiation throughout the Quaternary. Ice age-induced sea level fluctuations can lead to changing patterns of land connections, both facilitating and disrupting gene flow. In this study, we test if species with differing life histories are differentially affected by Quaternary land connections. We used genome-wide SNPs in combination with mitochondrial gene sequences to analyse levels of divergence and gene flow between two songbird complexes across two Wallacean islands that have been repeatedly connected during glaciations. Although the two bird complexes are similar in ecological attributes, the forest and edge-inhabiting golden whistler Pachycephala pectoralis is comparatively flexible in its diet and niche requirements as compared to the henna-tailed jungle-flycatcher Cyornis colonus, which is largely restricted to the forest interior. Using population-genomic and coalescent approaches, we estimated levels of gene flow, population differentiation and divergence time between the two island populations. We observed higher levels of differentiation, an approximately two to four times deeper divergence time and near-zero levels of gene flow between the two island populations of the more forest-dependent henna-tailed jungle-flycatcher as compared to the more generalist golden whistler. Our results suggest that Quaternary land bridges act as semipermeable agents of gene flow in Wallacea, allowing only certain taxa to connect between islands while others remain isolated. Quaternary land bridges do not accommodate all terrestrial species equally, differing in suitability according to life history and species biology. More generalist species are likely to use Quaternary land connections as a conduit for gene flow between islands whereas island populations of more specialist species may continue to be reproductively isolated even during periods of Quaternary land bridges. Copyright © 2018 Elsevier Inc. All rights reserved.

Paleontology to policy: the Quaternary history of Southeast Asian tapirs (Tapiridae) in relation to large mammal species turnover, with a proposal for conservation of Malayan tapir by reintroduction to Borneo.

PubMed

Cranbrook, Earl Of; Piper, Philip J

2013-03-01

The Southeast Asian zoogeographical region is divided into Indochinese, Sundaic and Philippine subregions. Two clades of tapirs, Tapirus spp., have been recognized in Quaternary Southeast Asia. A review of sites at which they occurred shows that representatives of both clades, one of which was the ancestral Malayan tapir Tapirus indicus, co-existed with a diversity of other Pleistocene mammal megafauna. The process of replacement of archaic large mammals was progressive and prolonged through the Quaternary. Zooarcheological investigation has extended knowledge of the former occurrence and distribution of tapirs and other large mammals of the region, with discoveries beyond the outer limits of their previously known ranges. These large mammals were subjected to paleoenvironmental changes as a consequence of the Quaternary cycles of glacial and interglacial periods. Archeological evidence suggests that hunting pressure has intensified the effects of altered environments, leading ultimately to the local disappearance of the Malayan tapir in most of Southeast Asia, including Borneo. The survival of the Malayan tapir through the Quaternary until the present shows that the species is both resilient to environmental change and flexible in its ecological re'uirements and, given proper protection, could continue to inhabit tropical Southeast Asia. To assist the species conservation, reintroduction is proposed from the remaining range of Malayan tapir in the wild, to suitable sites of past occurrence in Borneo, where these ancient survivors of the Quaternary megafauna can be accommodated and safeguarded alongside other forms of land usage. © 2012 Wiley Publishing Asia Pty Ltd, ISZS and IOZ/CAS.

3D seismic evidence of buried iceberg ploughmarks from the mid-Norwegian continental margin reveals largely persistent North Atlantic Current through the Quaternary.

PubMed

Montelli, A; Dowdeswell, J A; Ottesen, D; Johansen, S E

2018-05-01

Over 7500 buried linear and curvilinear depressions interpreted as iceberg ploughmarks were identified within the Quaternary Naust Formation from an extensive three-dimensional seismic dataset that covers ~ 40,000 km 2 of the mid-Norwegian continental margin. The morphology and net orientation of ploughmarks were mapped and analysed. These features are up to 28 km long, 700 m wide and are incised up to 31 m deep. On average, ploughmarks are incised 5 m deep, with median width of 185 m and median lengths ranging from 1.2 to 2.7 km for individual palaeo-surfaces. Width to depth ratio ranges from 8:1 to 400:1 and is on average 36:1. The presence of ploughmarks buried deeply within some palaeo-slope surfaces implies the occasional presence of very large icebergs since the middle Quaternary, suggesting that thick ice-sheet margins with fast-flowing ice streams were present in order to calve icebergs of such dimensions into the Norwegian Sea. The wide geographical distribution of ploughmarks suggests unrestricted iceberg drift and an open Norwegian Sea during the periods of iceberg calving since the early Quaternary. Ploughmark trajectory analysis demonstrates that the ocean current circulation, now dominated by the northeasterly flowing Norwegian Atlantic Current (NwAC), has largely persisted throughout the Quaternary. Despite the overall strikingly consistent pattern of iceberg drift, ploughmark mapping also shows evidence for short-lived NwAC reductions possibly related to major phases of iceberg discharge and/or meltwater pulses from the Fennoscandian Ice Sheet during the middle and late Quaternary.

Ion-pair hollow-fiber liquid-phase microextraction of the quaternary ammonium surfactant dicocodimethylammonium chloride.

PubMed

Hultgren, Sofie; Larsson, Niklas; Nilsson, Bo F; Jönsson, Jan Ake

2009-02-01

A two-phase hollow-fiber (HF) liquid-phase microextraction (LPME) method was developed for determination of a quaternary ammonium compound surfactant, dicocodimethylammonium chloride, in aqueous samples. The porous HF was fixed on a metal rod support and was impregnated with approximately 6.6 microL of organic extractant, which was immobilized in the HF pores. Surfactant extraction was facilitated by addition of carboxylic acid to the sample forming neutral ion pairs with the quaternary ammonium compound. After extraction, the analyte was transferred from the organic extractant in the fiber pores by dissolving the 1-octanol into 100 microL methanol. The methanol extract was analyzed by liquid chromatography-mass spectrometry. The method was optimized (with optimized parameters in brackets) with regard to type of organic extractant (1-octanol), fiber length (2 cm), choice and concentration of anionic carrier (600 microg L(-1) octanoate), procedure of transfer to methanol (15-min sonication), sample volume (250 mL), extraction time (17 h), pH (10), and ionic strength (50 mM carbonate). Aspects influencing repeatability in LPME of (quaternary ammonium) surfactants are discussed. The enrichment factor achieved in 250-mL carbonate buffer was around 400. Due to matrix effects, the enrichment factors achieved when industrial process water was analyzed were 120 or about 30% of that in carbonate buffer. Detection limits of 0.3 microg L(-1) in carbonate buffer and 0.9 microg L(-1) in industrial process water were obtained. If the studied compound is seen as a model substance representing quaternary dialkylated dimethylated ammonium surfactants in general, the developed method may be applied to other quaternary ammonium surfactants.

Evaluating the Significance of Paleophylogeographic Species Distribution Models in Reconstructing Quaternary Range-Shifts of Nearctic Chelonians

PubMed Central

Flecks, Morris; Ahmadzadeh, Faraham; Dambach, Johannes; Engler, Jan O.; Habel, Jan Christian; Hartmann, Timo; Hörnes, David; Ihlow, Flora; Schidelko, Kathrin; Stiels, Darius; Polly, P. David

2013-01-01

The climatic cycles of the Quaternary, during which global mean annual temperatures have regularly changed by 5–10°C, provide a special opportunity for studying the rate, magnitude, and effects of geographic responses to changing climates. During the Quaternary, high- and mid-latitude species were extirpated from regions that were covered by ice or otherwise became unsuitable, persisting in refugial retreats where the environment was compatible with their tolerances. In this study we combine modern geographic range data, phylogeny, Pleistocene paleoclimatic models, and isotopic records of changes in global mean annual temperature, to produce a temporally continuous model of geographic changes in potential habitat for 59 species of North American turtles over the past 320 Ka (three full glacial-interglacial cycles). These paleophylogeographic models indicate the areas where past climates were compatible with the modern ranges of the species and serve as hypotheses for how their geographic ranges would have changed in response to Quaternary climate cycles. We test these hypotheses against physiological, genetic, taxonomic and fossil evidence, and we then use them to measure the effects of Quaternary climate cycles on species distributions. Patterns of range expansion, contraction, and fragmentation in the models are strongly congruent with (i) phylogeographic differentiation; (ii) morphological variation; (iii) physiological tolerances; and (iv) intraspecific genetic variability. Modern species with significant interspecific differentiation have geographic ranges that strongly fluctuated and repeatedly fragmented throughout the Quaternary. Modern species with low genetic diversity have geographic distributions that were highly variable and at times exceedingly small in the past. Our results reveal the potential for paleophylogeographic models to (i) reconstruct past geographic range modifications, (ii) identify geographic processes that result in genetic bottlenecks; and (iii) predict threats due to anthropogenic climate change in the future. PMID:24130664

Nanostructure and strain effects in active thin films for novel electronic device applications

NASA Astrophysics Data System (ADS)

Yuan, Zheng

2007-12-01

There are many potential applications of ferroelectric thin films that take advantage of their unique dielectric and piezoelectric properties, such as tunable microwave devices and thin-film active sensors for structural health monitoring (SHM). However, many technical issues still restrict practical applications of ferroelectric thin films, including high insertion loss, limited figure of merit, soft mode effect, large temperature coefficients, and others. The main theme of this thesis is the advanced technique developments, and the new ferroelectric thin films syntheses and investigations for novel device applications. A novel method of additional doping has been adopted to (Ba,Sr)TiO 3 (BSTO) thin films on MgO. By introducing 2% Mn into the stoichiometric BSTO, Mn:BSTO thin films have shown a greatly enhanced dielectric tunability and a reduced insertion loss at high frequencies (10-30 GHz). A new record of a large tunability of 80% with a high dielectric constant of 3800 and an extra low dielectric loss of 0.001 at 1 MHz at room-temperature was achieved. Meanwhile, the new highly epitaxial ferroelectric (Pb,Sr)TiO3 (PSTO) thin films have been synthesized on (001) MgO substrates. PSTO films demonstrated excellent high frequency dielectric properties with high dielectric constants above 1420 and large dielectric tunabilities above 34% at room-temperature up to 20 GHz. In addition, a smaller temperature coefficient from 80 K to 300 K was observed in PSTO films compared to BSTO films. These results indicate that the Mn:BSTO and PSTO films are both good candidates for developing room-temperature tunable microwave devices. Furthermore, crystalline ferroelectric BaTiO3 (BTO) thin films have been deposited directly on metal substrate Ni through a unique in-situ substrate pre-oxidation treatment. The highly oriented nanopillar structural BTO films were grown on the buffered layers created by the pre-oxidation treatment. No interdiffusion or reaction was observed at the interface. As-grown BTO films demonstrated good ferroelectric properties and an extremely large piezoelectric response of 130 (x 10-12 C/N). These excellent preliminary results enable the long-term perspective on the unobtrusive ferroelectric thin-film active sensors for SHM applications.

Syntheses, structures, and physical properties of CsRE(2)Ag(3)Te(5) (RE = Pr, Nd, Sm, Gd-Er) and RbR(2)Ag(3)Te(5) (RE = Sm, Gd-Dy).

PubMed

Meng, Chang-Yu; Chen, Hong; Wang, Peng

2014-07-07

A new series of quaternary CsRE2Ag3Te5 (RE = Pr, Nd, Sm, Gd-Er) and RbRE2Ag3Te5 (RE = Sm, Gd-Dy), which have been synthesized from the elemental mixtures in ACl flux (A = Rb, Cs) and crystallized in the orthorhombic space group Cmcm, with a = 4.620(2)-4.504(2) Å, b = 16.232(8)-16.027(8) Å, c = 18.84(1)-18.32(2) and Z = 4, are isostructural to RbSm2Ag3Se5. These isostructural ARE2Ag3Te5 feature a three-dimensional tunnel framework constructed by ionically bound RETe6 octahedron and covalently bound AgTe4 tetrahedron in which tunnels are filled by A. Typical semiconducting behavior is revealed by the electrical conductivity, Seebeck coefficient, optical band gap measurement, and the theoretical calculations. The undoped sintered polycrystalline pellets of CsRE2Ag3Te5 (containing 1.1-1.7% CsCl impurity) show very low electrical conductivity (σr.t. = 0.5-2.4 S/cm), very low thermal conductivity (kr,t = 0.66-0.53 W/(m·K)), and moderate Seebeck coefficient (160-200 μV/K at 700 K).

Non-site-specific allosteric effect of oxygen on human hemoglobin under high oxygen partial pressure

PubMed Central

Takayanagi, Masayoshi; Kurisaki, Ikuo; Nagaoka, Masataka

2014-01-01

Protein allostery is essential for vital activities. Allosteric regulation of human hemoglobin (HbA) with two quaternary states T and R has been a paradigm of allosteric structural regulation of proteins. It is widely accepted that oxygen molecules (O2) act as a “site-specific” homotropic effector, or the successive O2 binding to the heme brings about the quaternary regulation. However, here we show that the site-specific allosteric effect is not necessarily only a unique mechanism of O2 allostery. Our simulation results revealed that the solution environment of high O2 partial pressure enhances the quaternary change from T to R without binding to the heme, suggesting an additional “non-site-specific” allosteric effect of O2. The latter effect should play a complementary role in the quaternary change by affecting the intersubunit contacts. This analysis must become a milestone in comprehensive understanding of the allosteric regulation of HbA from the molecular point of view. PMID:24710521

Analysis of Predominance of Sexual Reproduction and Quadruplicity of Bases by Computer Simulation

NASA Astrophysics Data System (ADS)

Dasgupta, Subinay

We have presented elsewhere a model for computer simulation of a colony of individuals reproducing sexually, by meiotic parthenogenesis and by cloning. Our algorithm takes into account food and space restriction, and attacks of some diseases. Each individual is characterized by a string of L ``base'' units, each of which can be of four types (quaternary model) or two types (binary model). Our previous report was for the case of L=12 (quaternary model) and L=24 (binary model) and contained the result that the fluctuation of population was the lowest for sexual reproduction with four types of base units. The present communication reports that the same conclusion also holds for L=10 (quaternary model) and L=20 (binary model), and for L=8 (quaternary model) and L=16 (binary model). This model however, suffers from the drawback that it does not show the effect of aging. A modification of the model was attempted to remove this drawback, but the results were not encouraging.

Phase and Physicochemical Properties Diagrams of Quaternary System Li2B4O7 + Na2B4O7 + Mg2B6O11 + H2O

NASA Astrophysics Data System (ADS)

Wang, Shi-qiang; Du, Xue-min; Jing, Yan; Guo, Ya-fei; Deng, Tian-long

2017-12-01

The phase and physicochemical properties diagrams of the quaternary system (Li2B4O7 + Na2B4O7 + Mg2B6O11) at 288.15 K and 0.1 MPa were constructed using the solubilities, densities, and refractive indices measured. In the phase diagrams of the system there are one invariant point, three univariant isothermic dissolution curves, and three crystallization regions corresponding to Li2B4O7 · 3H2O, Na2B4O7 · 10H2O, and Mg2B6O11 · 15H2O, respectively. The solution density, refractive index of the quaternary system changes regularly with the increasing of Li2B4O7 concentration. The calculated values of density and refractive index using empirical equations of the quaternary system are in good agreement with the experimental values.

Hydrolysis of cellulose catalyzed by quaternary ammonium perrhenates in 1-allyl-3-methylimidazolium chloride.

PubMed

Wang, Jingyun; Zhou, Mingdong; Yuan, Yuguo; Zhang, Quan; Fang, Xiangchen; Zang, Shuliang

2015-12-01

Quaternary ammonium perrhenates were applied as catalyst to promote the hydrolysis of cellulose in 1-allyl-3-methylimidazolium chloride ([Amim]Cl). The quaternary ammonium perrhenates displayed good catalytic performance for cellulose hydrolysis. Water was also proven to be effective to promote cellulose hydrolysis. Accordingly, 97% of total reduced sugar (TRS) and 42% of glucose yields could be obtained under the condition of using 5mol% of tetramethyl ammonium perrhenate as catalyst, 70μL of water, ca. 0.6mmol of microcrystalline cellulose (MCC) and 2.0g of [Amim]Cl as solvent under microwave irradiation for 30min at 150°C (optimal conditions). The influence of quaternary ammonium cation on the efficiency of cellulose hydrolysis was examined based on different cation structures of perrhenates. The mechanism on perrhenate catalyzed cellulose hydrolysis is also discussed, whereas hydrogen bonding between ReO4 anion and hydroxyl groups of cellulose is assumed to be the key step for depolymerization of cellulose. Copyright © 2015. Published by Elsevier Ltd.

Anticholinesterase inhibitory activity of quaternary alkaloids from Tinospora crispa.

PubMed

Yusoff, Mashitah; Hamid, Hazrulrizawati; Houghton, Peter

2014-01-20

Quaternary alkaloids are the major alkaloids isolated from Tinospora species. A previous study pointed to the necessary presence of quaternary nitrogens for strong acetylcholinesterase (AChE) inhibitory activity in such alkaloids. Repeated column chromatography of the vine of Tinospora crispa extract led to the isolation of one new protoberberine alkaloid, 4,13-dihydroxy-2,8,9-trimethoxydibenzo[a,g]quinolizinium (1), along with six known alkaloids-dihydrodiscretamine (2), columbamine (3), magnoflorine (4), N-formylannonaine (5), N-formylnornuciferine (6), and N-trans-feruloyltyramine (7). The seven compounds were isolated and structurally elucidated by spectroscopic analysis. Two known alkaloids, namely, dihydrodiscretamine and columbamine are reported for the first time for this plant. The compounds were tested for AChE inhibitory activity using Ellman's method. In the AChE inhibition assay, only columbamine (3) showed strong activity with IC50 48.1 µM. The structure-activity relationships derived from these results suggest that the quaternary nitrogen in the skeleton has some effect, but that a high degree of methoxylation is more important for acetylcholinesterase inhibition.

Why is quaternary prevention important in prevention?

PubMed Central

Tesser, Charles Dalcanale

2017-01-01

ABSTRACT Quaternary prevention consists in the identification of persons at risk of excessive medicalization and their protection against new unnecessary interventions, avoiding iatrogenic damages. Here, we argue about the importance of quaternary prevention in specific primary and secondary prevention. The recent great development of preventive medicine, biomedicalization of risks and their treatment as if they were diseases, and the powerful influence of the commercial interests of pharmaceutical industries on the production of medical-sanitary knowledge alter classifications, create diseases and pre-diseases, lower cutoff points, and erase the distinction between prevention and healing. This situation converts larger amounts of asymptomatic persons into sick individuals and diverts clinical attention and resources from sick persons to the healthy, from older adults to young persons, and from the poor to the rich. Quaternary prevention facilitates and induces the development and systematization of operational knowledge and guidelines to contain hypermedicalization and the damages of preventive actions in professional care, especially in primary health care. PMID:29211199

Non-site-specific allosteric effect of oxygen on human hemoglobin under high oxygen partial pressure.

PubMed

Takayanagi, Masayoshi; Kurisaki, Ikuo; Nagaoka, Masataka

2014-04-08

Protein allostery is essential for vital activities. Allosteric regulation of human hemoglobin (HbA) with two quaternary states T and R has been a paradigm of allosteric structural regulation of proteins. It is widely accepted that oxygen molecules (O2) act as a "site-specific" homotropic effector, or the successive O2 binding to the heme brings about the quaternary regulation. However, here we show that the site-specific allosteric effect is not necessarily only a unique mechanism of O2 allostery. Our simulation results revealed that the solution environment of high O2 partial pressure enhances the quaternary change from T to R without binding to the heme, suggesting an additional "non-site-specific" allosteric effect of O2. The latter effect should play a complementary role in the quaternary change by affecting the intersubunit contacts. This analysis must become a milestone in comprehensive understanding of the allosteric regulation of HbA from the molecular point of view.

Seismic evidence of Quaternary faulting in the Benton Hills area, southeast Missouri

USGS Publications Warehouse

Palmer, J.R.; Shoemaker, M.; Hoffman, D.; Anderson, N.L.; Vaughn, J.D.; Harrison, R.W.

1997-01-01

Two reflection seismic profiles at English Hill, across the southern edge of the Benton Hills escarpment, southeast Missouri, establish that geologic structures at English Hill are of tectonic origin. The lowland area to the south of the escarpment is relatively undisturbed. The geology at English Hill is structurally complex, and reflection seismic and geologic data indicate extensive and episodic faulting of Paleozoic, Cretaceous, Tertiary, and Quaternary strata. The individual faults have near-vertical fault surfaces with maximum vertical separations on the order of 15 m. They appear to be clustered in north-northeast trending zones that essentially parallel one of the dominant Benton Hills structural trends. These observations suggest that previously mapped Quaternary faults at English Hill are deep-seated and tectonic in origin. This paper documents recent faulting at English Hill and is the first time late Quaternary, surface-rupture faulting has been recognized in the middle Mississippi River Valley region outside of the New Madrid seismic zone. This has important implications for earthquake assessment in the midcontinent.

Partitioning the Quaternary

NASA Astrophysics Data System (ADS)

Gibbard, Philip L.; Lewin, John

2016-11-01

We review the historical purposes and procedures for stratigraphical division and naming within the Quaternary, and summarize the current requirements for formal partitioning through the International Commission on Stratigraphy (ICS). A raft of new data and evidence has impacted traditional approaches: quasi-continuous records from ocean sediments and ice cores, new numerical dating techniques, and alternative macro-models, such as those provided through Sequence Stratigraphy and Earth-System Science. The practical usefulness of division remains, but there is now greater appreciation of complex Quaternary detail and the modelling of time continua, the latter also extending into the future. There are problems both of commission (what is done, but could be done better) and of omission (what gets left out) in partitioning the Quaternary. These include the challenge set by the use of unconformities as stage boundaries, how to deal with multiphase records in ocean and terrestrial sediments, what happened at the 'Early-Mid- (Middle) Pleistocene Transition', dealing with trends that cross phase boundaries, and the current controversial focus on how to subdivide the Holocene and formally define an 'Anthropocene'.

Improved Optical Transmittance and Crystal Characteristics of ZnS:TbOF Thin Film on Bi4Ti3O12/Indium Tin Oxide/Glass Substrate by Using a SiO2 Buffer Layer

NASA Astrophysics Data System (ADS)

Chia, Wei‑Kuo; Yokoyama, Meiso; Yang, Cheng‑Fu; Chiang, Wang‑Ta; Chen, Ying‑Chung

2006-07-01

Bi4Ti3O12 thin films are deposited on indium tin oxide (ITO)/glass substrates using RF magnetron sputtering technology and are annealed at 675 °C in a rapid thermal annealing furnace in an oxygen atmosphere. The resulting films have high optical transmittances and good crystalline characteristics. ZnS:TbOF films are then deposited on the Bi4Ti3O12 films, causing the originally highly transparent specimens to blacken and to resemble a glass surface coated with carbon powder. The optical transmittance of the specimen is less than 15% under the visible wavelength range, and neither a crystalline phase nor a distinct ZnS grain structure is evident in X-ray diffractometer (XRD) and scanning electronic microscope (SEM). Secondary ion mass spectrometer (SIMS) analysis reveals the occurrence of interdiffusion between the ZnS and Bi4Ti3O12 layers. This suggests that one or more unknown chemical reactions take place among the elements Bi, S, and O at the interface during the deposition of ZnS:TbOF film on a Bi4Ti3O12/ITO/glass substrate. These reactions cause the visible transmittance of the specimens to deteriorate dramatically. To prevent interdiffusion, a silicon dioxide (SiO2) buffer layer 100 nm thick was grown on the Bi4Ti3O12/ITO/glass substrate using plasma-enhanced chemical vapor deposition (PECVD), then the ZnS:TbOF film was grown on the SiO2 buffer layer. The transmittance of the resulting specimen is enhanced approximately 8-fold in the visible region. XRD patterns reveal the ZnS(111)-oriented phase is dominant. Furthermore, dense, crack-free ZnS:TbOF grains are observed by SEM. The results imply that the SiO2 buffer layer sandwiched between the ZnS:TbOF and Bi4Ti3O2 layers effectively separates the two layers. Therefore, interdiffusion and chemical reactions are prevented at the interface of the two layers, and the crystalline characteristics of the ZnS:TbOF layer and the optical transmittance of the specimen are improved as a result. Finally, the dielectric constant of the stacked structure is lower than that of the single layer structure without SiO2, but the dielectric breakdown strength is enhanced.

Data without Frontiers - the International Quaternary Map of Europe (IQUAME 2500)

NASA Astrophysics Data System (ADS)

Asch, Kristine

2017-04-01

The Federal German Geological Survey (Bundesanstalt für Geowissenschaften und Rohstoffe, BGR) is leading the review of the International Quaternary Map of Europe (IQUAME 2500) and its transformation into a geographical information system (GIS) under the umbrella of the CGMW and INQUA. It is a long-standing policy of BGR to lead international cooperation of European geological survey mapping projects. These particularly include projects under the umbrella of organisations including CGMW, UNESCO, INQUA, EGU and IUGS. The aim of IQUAME 2500 is to build a geological information system (GIS) of Europe's Quaternary geology where relevant information can be retrieved, combined and applied across international boundaries. Cross-border mapping poses specific challenges, in particular data harmonisation, for the presentation of regional geology. Overcoming these obstacles demands international cooperation with national geological survey organisations. Based on the previous BGR & UNESCO co-produced International Quaternary Map of Europe (at a 1 : 2,5 million scale; completed in 1995), revision was begun by BGR in 2011 to review the information available from an international group of experts from European geological survey organisations. This group is supported by an international academic Advisory Board. The work requires re-evaluation and digitization of the 14 paper sheets. For this purpose BGR developed a pragmatic procedure to classify, deliver and combine the reviewed Quaternary data in a harmonized and uniform manner. The project is applying the vocabularies and data model of the EC Directive INSPIRE Directive and is creating additional vocabularies and definitions for necessary features such as geomorphology (with the EMODnet project) and glaciogenic elements. An academic scientific advisory board is overseeing the process. Subjects of the map include: geological boundaries and classifications of Quaternary rocks, extension and boundaries of permafrost, last glacial maximum, genetic descriptions of the rocks, faults, key localities (geologically and palaeontologically significant sites, anthropological sites, impact craters, etc.) and more detailed off-shore geology (in cooperation with the EMODnet project). Ultimately, the IQUAME project will summarise the current status quo of European Quaternary geological research in a digitally available GIS synthesis and introduce practically applicable new vocabularies to describe the results and share those with the science community.

New evidence of the nonglaciated development of the northern part of the Western Siberian lowland in the Quaternary period

NASA Astrophysics Data System (ADS)

Sheinkman, V. S.; Melnikov, V. P.; Sedov, S. N.; Parnachev, V. P.

2017-12-01

To solve the controversially debated problem related to the areal extent of the ice sheet in Western Siberia in the Quaternary period, we have studied the development of cold born objects of this area estimating the relationships between them in terms of cryogenic diversity. We have obtained a field of new cross data related to the development of cryogenic and glacial phenomena, their relationship, and traces they left. The research showed that, in this area, the trend of rock freezing is clearly reflected in the Quaternary formations, but there were no conditions for ice sheet development even during the cryochrons.

Band gap depiction of quaternary FeMnTiAl alloy using Hubbard (U) potential

NASA Astrophysics Data System (ADS)

Bhat, Tahir Mohiuddin; Yousuf, Saleem; Khandy, Shakeel Ahmad; Gupta, Dinesh C.

2018-05-01

We have employed self-consistent ab-initio calculations to investigate new quaternary alloy FeMnTiAl by applying Hubbard potential (U). The alloy is found to be stable in ferromagnetic phase with cubic structure. The alloy shows half-metallic (HM) ferromagnet character. The values of minority band gap FeMnTiAl are found to be 0.33 eV respectively. Electronic charge density reveals that both types of bonds covalent as well as ionic are present in the alloy. Thus the new quaternary alloy can be proved as vital contender for spin valves and spin generator devices.

Viscosity and diffusivity in melts: from unary to multicomponent systems

NASA Astrophysics Data System (ADS)

Chen, Weimin; Zhang, Lijun; Du, Yong; Huang, Baiyun

2014-05-01

Viscosity and diffusivity, two important transport coefficients, are systematically investigated from unary melt to binary to multicomponent melts in the present work. By coupling with Kaptay's viscosity equation of pure liquid metals and effective radii of diffusion species, the Sutherland equation is modified by taking the size effect into account, and further derived into an Arrhenius formula for the convenient usage. Its reliability for predicting self-diffusivity and impurity diffusivity in unary liquids is then validated by comparing the calculated self-diffusivities and impurity diffusivities in liquid Al- and Fe-based alloys with the experimental and the assessed data. Moreover, the Kozlov model was chosen among various viscosity models as the most reliable one to reproduce the experimental viscosities in binary and multicomponent melts. Based on the reliable viscosities calculated from the Kozlov model, the modified Sutherland equation is utilized to predict the tracer diffusivities in binary and multicomponent melts, and validated in Al-Cu, Al-Ni and Al-Ce-Ni melts. Comprehensive comparisons between the calculated results and the literature data indicate that the experimental tracer diffusivities and the theoretical ones can be well reproduced by the present calculations. In addition, the vacancy-wind factor in binary liquid Al-Ni alloys with the increasing temperature is also discussed. What's more, the calculated inter-diffusivities in liquid Al-Cu, Al-Ni and Al-Ag-Cu alloys are also in excellent agreement with the measured and theoretical data. Comparisons between the simulated concentration profiles and the measured ones in Al-Cu, Al-Ce-Ni and Al-Ag-Cu melts are further used to validate the present calculation method.

40 CFR 721.9075 - Quaternary ammonium salt of fluorinated alkylaryl amide.

Code of Federal Regulations, 2010 CFR

2010-07-01

... fluorinated alkylaryl amide. 721.9075 Section 721.9075 Protection of Environment ENVIRONMENTAL PROTECTION... amide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as quaternary ammonium salt of fluorinated alkylaryl amide (PMN No. P-92-688) is...

Extracting lignins from mill wastes

NASA Technical Reports Server (NTRS)

Humphrey, M. F.

1977-01-01

Addition of quaternary ammonium compound and activated charcoal to pulp and mill wastes precipitates lignins in sludge mixture. Methanol dissolves lignins for separation from resulting slurry. Mineral acid reprecipitates lignins in filtered solution. Quaternary ammonium compound, activated charcoal, as well as water may be recovered and recycled from this process.

EVALUATION OF METHODS FOR THE ISOLATION OR CONCENTRATION OF ORGANIC SUBSTANCES FROM WATER USING XAD-4 QUATERNARY RESIN

EPA Science Inventory

A synthetic resin (Amberlite XAD-4 Quaternary in the OH- form) was evaluated as an adsorption medium for the concentration/isolation of acids, amines, aldehydes, carbohydrates, chlorobiphenyls, esters, hydrocarbons, ketones, phenols, polynuclear aromatic hydrocarbons, and trihalo...

Mid-infrared multiple quantum well lasers using digitally-grown aluminum indium arsenic antimonide barriers and strained indium arsenic antimonide wells

NASA Astrophysics Data System (ADS)

Vaughn, Leslie G.

2006-04-01

AlxIn(1-x)AsySb(1-y) quaternary alloys have been used in Type I midwave infrared (MWIR) laser structures as barrier materials with InAs and InAsSb quantum wells. However, growth of these alloys has limited the application because of a large miscibility gap. In this research, quaternary films with compositions well into the miscibility gap (0 ≤ x ≤ 0.50) have been grown for the first time by molecular beam epitaxy (MBE) using a digital alloy technique. These films, lattice-matched to GaSb, have been characterized using double crystal X-ray diffraction (DCXRD), transmission electron microscopy (TEM), and photoluminescence (PL). Results indicate uniform, single-phase, and highly crystalline films. Using PL data, the dependence of the quaternary bandgap on composition has been studied and fit to various theoretical models. Combining the quaternary bandgap equation with strain and quantum size effects, the wavelengths for strained InAsSb wells in AlInAsSb quaternary barriers are predicted and compared to measured values generated from PL experiments. The reasonable agreement of these experimental results with the theoretical model supports the assertion that the AlInAsSb/InAsSb material system is Type I and emits in the target wavelength range of 3.3-4.2 mum. PL spectra of AlInAsSb/InAsSb multiple quantum wells exhibit a substantial increase in intensity with increasing quaternary aluminum content. This is presumably due to increasing valence band offset and, therefore, to better hole confinement. A laser with this active region has been fabricated and tested. Under pulsed optical pumping conditions at 50K, the laser emitted light at ˜3.93 mum. Further work has been done using the digital alloy technique to add gallium to the quaternary alloy to produce an AlGaInAsSb quinary alloy lattice-matched to GaSb. This material is of specific interest for mid-infrared lasers because by adding the fifth element, gallium, the range of material properties is extended. There is some indication from PL testing that the addition of the fifth element may contribute to Auger recombination suppression and may lead to higher operating temperatures. DCXRD and TEM of these quinary alloys give results similar to the quaternary alloys. The stable, single-phase growth of these quinary alloys shows promise for improving the performance of MWIR lasers.

Sharing post-AML consolidation supportive therapy with local centers reduces patient travel burden without compromising outcomes.

PubMed

Hershenfeld, Samantha A; Maki, Kimberly; Rothfels, Lana; Murray, Cindy S; Nixon, Shannon; Schimmer, Aaron D; Doherty, Mary C

2017-08-01

Acute myeloid leukemia (AML) is frequently treated with induction and consolidation chemotherapy. Consolidation chemotherapy can be delivered on an ambulatory basis, requiring some patients to travel long distances for treatment at specialized centers. We developed a shared care model where patients receive consolidation chemotherapy at a quaternary center, but post-consolidation supportive care at local hospitals. To evaluate the impact of our model on patient travel and outcomes we conducted a retrospective analysis of AML and acute promyelocytic leukemia patients receiving consolidation over four years at our quaternary center. 73 patients received post-consolidation care locally, and 344 at the quaternary center. Gender, age and cytogenetic risk did not significantly differ between groups. Shared care patients saved mean round trip distance of 146.5km±99.6 and time of 96.7min±63.4 compared to travelling to quaternary center. There was no significant difference in overall survival between groups, and no increased hazard of death for shared care patients. 30, 60, and 90day survival from start of consolidation was 98.6%, 97.2%, and 95.9% for shared care and 98.8%, 97.1%, and 95.3% for quaternary center patients. Thus, a model utilizing regional partnerships for AML post-consolidation care reduces travel burden while maintaining safety. Copyright © 2017 Elsevier Ltd. All rights reserved.

Water resources of Teton County, Wyoming, exclusive of Yellowstone National Park

USGS Publications Warehouse

Nolan, B.T.; Miller, K.A.

1995-01-01

Surface- and ground-water data were collected and analyzed to describe the water resources of that part of Teton County, Wyoming located south of Yellowstone National Park. Wells and springs inventoried in the Teton County study area most commonly were completed in or issued from Quaternary unconsolidated deposits and Tertiary, Mesozoic, and Paleozoic rocks. The largest measured, reported, or estimated discharges were from Quaternary uncon- solidated deposits (3,000 gallons per minute), the Bacon Ridge Sandstone of Cretaceous age (800 gallons per minute), and the Madison Limestone of Mississippian age (800 gallons per minute). Dissolved-solids concentrations in water samples from Quaternary unconsolidated deposits and Tertiary, Mesozoic, and Paleozoic rocks ranged from 80 to 1,060 milligrams per liter. A time-domain electromagnetic survey of Jackson Hole indicated that the depth of Quaternary unconsolidated deposits ranged from about 380 feet in the northern part of Antelope Flats to about 2,400 feet near the Potholes area in Grand Teton National Park. A streamflow gain-and-loss study indicated that the ground-water discharge to the Snake River between gaging stations near Moran and south of the Flat Creek confluence, near Jackson, was 395 cubic feet per second. Water level contours generated from 137 water-level measurements and 118 stream altitudes indicated that water in Quaternary unconsolidated deposits flows southwest in the general direction of the Snake River.

New insights into the earliest Quaternary environments in the Central North Sea from 3D seismic

NASA Astrophysics Data System (ADS)

Lamb, Rachel; Huuse, Mads; Stewart, Margaret; Brocklehurst, Simon H.

2014-05-01

In the past the transition between an unconformable surface in the south to a conformable horizon towards the north has made identification and mapping the base-Quaternary in the central North Sea difficult (Sejrup et al 1991; Gatliff et al 1994). However recent integration of biostratigraphy, pollen analysis, paleomagnetism and amino acid analysis in the Dutch and Danish sectors (Rasmussen et al 2005; Kuhlmann et al 2006) has allowed greater confidence in the correlation to the region 3D seismic datasets and thus has allowed the base-Quaternary to be mapped across the entire basin. The base-Quaternary has been mapped using the PGS MegaSurvey dataset from wells in the Danish Sector along the initially unconformable horizon and down the delta front into the more conformable basin giving a high degree of confidence in the horizon pick. The revised base-Quaternary surface reaches a depth of 1248 ms TWT with an elongate basin shape which is significantly deeper than the traditionally mapped surface. Using RMS amplitudes and other seismic attributes the revised base-Quaternary has been investigated along the horizon and in time slice to interpret the environments of the earliest Quaternary prior to the onset of glaciation. Combined with analysis of aligned elongate furrows over 10 km long, 100 m wide and 100 m deep suggest a deep marine environment in an almost enclosed basin with persistent strong NW-SE bottom currents in the deepest parts. Pockmarks were formed by the escape of shallow gas on the sides of a small delta in the eastern part of the basin. The progradation of large deltas from both the north and south into the basin make up the majority of the deposition of sediment into the basin. Key Words: base-Quaternary; seismic interpretation; paleoenvironments References: Gatliff, R.W, Richards, P.C, Smith, K, Graham, C.C, McCormac, M, Smith, N.J.P, Long, D, Cameron, T.D.J, Evans, D, Stevenson, A.G, Bulat, J, Ritchie, J.D, (1994) 'United Kingdom offshore regional report: the geology of the central North Sea.' London: HMSO for the British Geological Survey Kuhlmann, G., Langereis C.G., Munsterman, D., van Leeuwen, R.-J., Verreussel, R., Meulenkamp, J.E., Wong, Th.E., 2006 'Intergrated chronostratigraphy of the Pliocene-Pliestocene interval and its relation to the regional stratigraphical stages in the Southern North Sea region' Netherlands Journal of Geosciences 85(1), 29-45 Rasmussen, E.A., Vejb?k O.V., Bidstrup, T., Piasecki, S., Dybkj?r, K., 2005 'Late Cenozoic depositional history of the Danish North Sea Basin: implications for the petroleum systems in the Kraka, Halfdan, Siri and Nini fields', Petroleum Geology Conference series 6, 1347-1358 Sejrup, H.P., Aareseth, I., Haflidason, H., 1991 'The Quaternary succession in the northern North Sea' Marine Geology 101 103-111

Effective construction of quaternary stereocenters by highly enantioselective α-amination of branched aldehydes.

PubMed

Fu, Ji-Ya; Xu, Xiao-Ying; Li, Yan-Chun; Huang, Qing-Chun; Wang, Li-Xin

2010-10-21

A highly efficient enantioselective α-amination of branched aldehydes with azadicarboxylates promoted by chiral proline-derived amide thiourea bifunctional catalysts was developed for the first time, affording the adducts bearing quaternary stereogenic centers with excellent yields (up to 99%) and enantioselectivities (up to 97% ee).

Efficient solar cells by space processing

NASA Technical Reports Server (NTRS)

Schmidt, F. A.; Campisi, G. J.; Bevolo, A.; Shanks, H. R.; Williams, D. E.

1979-01-01

Thin films of electron beam evaporated silicon were deposited on molybdenum, tantalum, tungsten and molybdenum disilicide under ultrahigh vacuum conditions. Mass spectra from a quadrapole residual gas analyzer were used to determine the partial pressure of 13 residual gases during each processing step. Surface contamination and interdiffusion were monitored by in situ Auger electron spectrometry. The presence of phosphorus in the silicon was responsible for attaining elevated temperatures with silicide formations. Heteroepitaxial silicon growth was sensitive to the presence of oxygen during deposition, the rate and length of deposition as well as the substrate orientation.

Chemical Bonding, Interdiffusion and Electronic Structure at InP, GaAs, and Si-Metal Interfaces.

DTIC Science & Technology

1984-01-15

1980) 420. 37. A. Hiraki , K. Shuts. F. Kim. W. Kammura. and W. Iwami, A\\ppl. Phys. Len. 31 (1977) 611, and references therein. 38. L.J. Brilison, C.F...and references therein. 5. A. Hiraki , M.A. Nicolet, and J.W. Mayer, Appi. Phys. Lett. !a, 178 (1971); A. Hiraki , K. Shuto, F. Kim, W. Kammura, and W...IZ, 1005 (1980) and references therein. 7. T. Narusawa, K. Kinoshita, W.M. Gibson, and A. Hiraki , J. Vac. Sci. Technol.. Ia. 872 (1981). 8. J

Sorption of dodecyltrimethylammonium chloride (DTAC) to agricultural soils.

PubMed

Xiang, Lei; Sun, Teng-Fei; Zheng, Mei-Jie; Li, Yan-Wen; Li, Hui; Wong, Ming-Hung; Cai, Quan-Ying; Mo, Ce-Hui

2016-08-01

Quaternary ammonium compounds (QACs) used as cationic surfactants are intensively released into environment to be pollutants receiving more and more concerns. Sorption of dodecyltrimethylammonium chloride (DTAC), one of commonly used alkyl QACs, to five types of agricultural soils at low concentrations (1-50mg/L) was investigated using batch experiments. DTAC sorption followed pseudo-second-order kinetics and reached reaction equilibrium within 120min. Both Freundlich model and Langmuir model fitted well with DTAC isotherm data with the latter better. DTAC sorption was spontaneous and favorable, presenting a physical sorption dominated by ion exchanges. Sorption distribution coefficient and sorption affinity demonstrated that soil clay contents acted as a predominant phase of DTAC sorption. DTAC could display a higher mobility and potential accumulation in crops in the soils with lower clay contents and lower pH values. Sorption of DTAC was heavily affected by ions in solution with anion promotion and cation inhibition. Copyright © 2016. Published by Elsevier B.V.

Lubrication studies of some type III deep eutectic solvents (DESs)

NASA Astrophysics Data System (ADS)

Ahmed, Essa. I.; Abbott, Andrew. P.; Ryder, Karl S.

2017-09-01

It has previously been shown that eutectic mixtures of quaternary ammonium salts and hydrogen bond donors form liquids with properties similar to ionic liquids [1; 2]. These so-called deep eutectic solvents (DESs) have been shown to have physical properties which would make them useful as base lubricants. The base lubricant needs to show specific properties, including high viscosity index (VI), low friction coefficient (μ), low pour point and corrosivity. To determine the applicability of DESs as base lubricants, physical properties, corrosion and lubrication properties for four type III DESs have been studied and the results have been compared with mineral base oil. The data show that the lubrication properties of DESs are superior to mineral base oil for short distances. All DESs assessed here have higher VI (191, 147, 121 for Ethaline, Glyceline and Reline respectively compared with 100 for mineral base oil), lower pour points than mineral base oil and most of the liquids studied have shown very low corrosion rates (< 3 µm year-1 for mild steel).

Study on the interaction between hematoporphyrin monomethyl ether and DNA and the determination of hematoporphyrin monomethyl ether using the resonance light scattering technique

NASA Astrophysics Data System (ADS)

Chen, Zhanguang; Song, Tianhe; Chen, Xi; Wang, Shaobin; Chen, Junhui

2010-10-01

The interaction between photosensitizer anticancer drug hematoporphyrin monomethyl ether (HMME) and ctDNA has been studied based on the decreased resonance light scattering (RLS) phenomenon. The RLS, UV-vis and fluorescence spectra characteristics of the HMME-ctDNA system were investigated. Besides, the phosphodiesters quaternary ammonium salt (PQAS), a kind of new gemini surfactant synthesized recently, was used to determine anticancer drug HMME based on the increasing RLS intensity. Under the optimum assay conditions, the enhanced RLS intensity was proportional to the concentration of HMME. The linear range was 0.8-8.4 μg mL -1, with correlation coefficient R2 = 0.9913. The detection limit was 0.014 μg mL -1. The human serum samples and urine samples were determined satisfactorily, which proved that this method was reliable and applicable in the determination of HMME in body fluid. The presented method was simple, sensitive and straightforward and could be a significant method in clinical analysis.

Synthesis of quaternary chalcogenide CZTS nanoparticles by a hydrothermal route

NASA Astrophysics Data System (ADS)

Das, S.; Sa, K.; Mahakul, P. C.; Raiguru, J.; Alam, I.; Subramanyam, BVRS; Mahanandia, P.

2018-03-01

Cu2ZnSnS4 (CZTS) has emerged as a potential absorber towards inorganic photovoltaic device application for its outstanding properties like non toxicity, earth abundancy nature, optimal band gap matched with solar spectrum (1.45- 1.65eV), high absorption coefficient (104cm‑1). Here, a low cost, environment friendly facile hydrothermal route to synthesize phase pure CZTS nanoparticles using Cu (II), Zn (II), Sn (II) inorganic metal salts and thiourea as Sulphur source in distilled water solution as precursor is reported. The as synthesized samples characterized by X-Ray diffraction (XRD) and RAMAN confirmed structure and phase of CZTS nanocrystals. The morphology of the prepared CZTS have been characterized by scanning electron microscopy (SEM). The particle size is found in the range 4-5 nm with crystalline nature have been characterized by transmission electron microscope (TEM). The optical band gap of the as prepared samples is calculated to be 1.65eV from UV-Visible analysis which proves it can be used towards photovoltaic applications.

The Andean orogenic front at Sierra de Las Peñas-Las Higueras, Mendoza, Argentina

NASA Astrophysics Data System (ADS)

Costa, Carlos H.; Gardini, Carlos E.; Diederix, Hans; Cortés, José M.

2000-07-01

The Sierra de Las Peñas-Las Higueras (Mendoza Province, Argentina, 32°15'S-32°45'S) presents one of the clearest and most continuous exposures of the Quaternary thrust front of the Precordilleran fold-and-thrust belt. It is characterized by an east-verging thrust that breaks the surface and causes Neogene sedimentary rocks to override Quaternary alluvial conglomerates. Monoclinal folds and progressive unconformities are characteristic of deformation in the upper part of the alluvial cover, indicating synchronous development of sedimentation and thrusting during the Quaternary. South of this range, ongoing deformation is by gentle warping of the piedmont alluvial plain, hiding blind thrusts at depth.

Resistance of alpha-crystallin quaternary structure to UV irradiation.

PubMed

Krivandin, A V; Muranov, K O; Yakovlev, F Yu; Poliansky, N B; Wasserman, L A; Ostrovsky, M A

2009-06-01

The damaging effect of UV radiation (lambda > 260 nm) on bovine alpha-crystallin in solution was studied by small-angle X-ray scattering, gel permeation chromatography, electrophoresis, absorption and fluorescence spectroscopy, and differential scanning calorimetry. The results obtained show that damage to even a large number of subunits within an alpha-crystallin oligomer does not cause significant rearrangement of its quaternary structure, aggregation of oligomers, or the loss of their solubility. Due to the high resistance of its quaternary structure, alpha-crystallin is able to prevent aggregation of destabilized proteins (especially of gamma- and beta-crystallins) and so to maintain lens transparency throughout the life of an animal (the chaperone-like function of alpha-crystallin).

INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: High-performance 1.3-μm InGaAsP/InP heterostructures formed by two-phase liquid epitaxy

NASA Astrophysics Data System (ADS)

Novotný, J.; Procházková, O.; Šrobár, F.; Zelinka, J.

1988-11-01

A description is given of a two-phase liquid epitaxy method used to grow InGaAsP/InP heterostructures intended for injection lasers emitting in the 1.3-μm range. A study was made of heterostructures of three types: double, with an additional quaternary layer (λ approx 1.1 μm) adjoining the active layer; with two quaternary layers between the active layer and the InP confining layers. The configuration with two flanking quaternary layers was found to be the best from the point of view of the threshold current density, optical output power, and reproducibility.

Site 765: Sediment Lithostratigraphy

USGS Publications Warehouse

,

1990-01-01

A 935-m-thick succession of Quaternary through Lower Cretaceous sediments was recovered at Site 765 (Fig. 10). A single core of Quaternary sediment was obtained from Hole 765A; drilling terminated and a new hole was drilled in an attempt to establish the mud line. Quaternary through middle Miocene sediments were cored in Hole 765B down to a depth of 395.6 mbsf. Middle Miocene through Lower Cretaceous sediments were cored in Hole 765C, after washing the interval between 0 and 350.2 mbsf. Exact lithologic correlation of the basal cores from Hole 765B with the upper cores from Hole 765C is not possible because of poor recovery; hence, correlation is based solely on matching sub-bottom depths.

Quaternary Glacial Mapping in Western Wisconsin Using Soil Survey Information

ERIC Educational Resources Information Center

Oehlke, Betsy M.; Dolliver, Holly A. S.

2011-01-01

The majority of soils in the western Wisconsin have developed from glacial sediments deposited during the Quaternary Period (2.6 million years before present). In many regions, multiple advances and retreats have left a complex landscape of diverse glacial sediments and landforms. The soils that have developed on these deposits reflect the nature…

40 CFR 721.8658 - Modified polymer of vinyl acetate and quaternary ammonium compound (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified polymer of vinyl acetate and... Significant New Uses for Specific Chemical Substances § 721.8658 Modified polymer of vinyl acetate and.... (1) The chemical substance identified generically as modified polymer of vinyl acetate and quaternary...

40 CFR 721.8658 - Modified polymer of vinyl acetate and quaternary ammonium compound (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Modified polymer of vinyl acetate and... Significant New Uses for Specific Chemical Substances § 721.8658 Modified polymer of vinyl acetate and.... (1) The chemical substance identified generically as modified polymer of vinyl acetate and quaternary...

Preparation of catalysts via ion-exchangeable coatings on supports

DOEpatents

Dosch, R.G.; Stephens, H.P.

1986-04-09

Disclosed are: new catalytic compositions which comprise an inert support coated with a hydrous alkali metal, alkaline earth metal, or quaternary ammonium titanate, niobate, zirconate, or tantalate, in which the alkali or alkaline earth metal or quaternary ammonium cations have been exchanged for a catalytically effective quantity of a catalytically effective metal.

40 CFR 721.8658 - Modified polymer of vinyl acetate and quaternary ammonium compound (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Modified polymer of vinyl acetate and... Significant New Uses for Specific Chemical Substances § 721.8658 Modified polymer of vinyl acetate and.... (1) The chemical substance identified generically as modified polymer of vinyl acetate and quaternary...

40 CFR 721.8658 - Modified polymer of vinyl acetate and quaternary ammonium compound (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Modified polymer of vinyl acetate and... Significant New Uses for Specific Chemical Substances § 721.8658 Modified polymer of vinyl acetate and.... (1) The chemical substance identified generically as modified polymer of vinyl acetate and quaternary...

40 CFR 721.8658 - Modified polymer of vinyl acetate and quaternary ammonium compound (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Modified polymer of vinyl acetate and... Significant New Uses for Specific Chemical Substances § 721.8658 Modified polymer of vinyl acetate and.... (1) The chemical substance identified generically as modified polymer of vinyl acetate and quaternary...

Design, synthesis of novel chitosan derivatives bearing quaternary phosphonium salts and evaluation of antifungal activity.

PubMed

Tan, Wenqiang; Zhang, Jingjing; Luan, Fang; Wei, Lijie; Chen, Yuan; Dong, Fang; Li, Qing; Guo, Zhanyong

2017-09-01

Two novel chitosan derivatives modified with quaternary phosphonium salts were successfully synthesized, including tricyclohexylphosphonium acetyl chitosan chloride (TCPACSC) and triphenylphosphonium acetyl chitosan chloride (TPPACSC), and characterized by FTIR, 1 H NMR, and 13 C NMR spectra. The degree of substitution was also calculated by elemental analysis results. Their antifungal activities against Colletotrichum lagenarium, Watermelon fusarium, and Fusarium oxysporum were investigated in vitro using the radial growth assay, minimal inhibitory concentration, and minimum bactericidal concentration assay. The fungicidal assessment revealed that the synthesized chitosan derivatives had superior antifungal activity compared with chitosan. Especially, TPPACSC exhibited the best antifungal property with inhibitory indices of over 75% at 1.0mg/mL. The results obviously showed that quaternary phosphonium groups could effectively enhance antifungal activity of the synthesized chitosan derivatives. Meanwhile, it was also found that their antifungal activity was influenced by electron-withdrawing ability of the quaternary phosphonium salts. The synthetic strategy described here could be utilized for the development of chitosan as antifungal biomaterials. Copyright © 2017 Elsevier B.V. All rights reserved.

Evaluation of Sintering Behaviors of Saprolitic Nickeliferous Laterite Based on Quaternary Basicity

NASA Astrophysics Data System (ADS)

Luo, Jun; Li, Guanghui; Rao, Mingjun; Zhang, Yuanbo; Peng, Zhiwei; Zhi, Qian; Jiang, Tao

2015-09-01

The sintering behaviors of saprolitic nickeliferous laterite with various quaternary basicities [(CaO + MgO)/(SiO2 + Al2O3) mass ratio] in a reductive atmosphere are investigated by simulative sintering and validated by sintering pot tests. The simulative sintering results show that the generation of diopside (CaMgSi2O6) with low melting point is the key reason for the decrease in characteristic fusion temperatures when the quaternary basicity increases from 0.5 to 0.8-1.0. Continuous increase of basicity leads to transformation of diopside (CaMgSi2O6) into akermanite (Ca2MgSi2O7), which adversely increases the characteristic fusion temperatures. These findings are confirmed by the sinter pot tests, which demonstrate that the sintering indexes including vertical sintering velocity (VSV), yield ( Y), and productivity ( P), can be improved by optimizing quaternary basicity. At basicity of 1.0, the VSV, Y, P, and ISO tumbling index reach 49.2 mm/min, 80.5%, 1.0 t/(h m2), and 66.5%, respectively.

Map and database of Quaternary faults in Venezuela and its offshore regions

USGS Publications Warehouse

Audemard, F.A.; Machette, M.N.; Cox, J.W.; Dart, R.L.; Haller, K.M.

2000-01-01

As part of the International Lithosphere Program’s “World Map of Major Active Faults,” the U.S. Geological Survey is assisting in the compilation of a series of digital maps of Quaternary faults and folds in Western Hemisphere countries. The maps show the locations, ages, and activity rates of major earthquake-related features such as faults and fault-related folds. They are accompanied by databases that describe these features and document current information on their activity in the Quaternary. The project is a key part of the Global Seismic Hazards Assessment Program (ILP Project II-0) for the International Decade for Natural Hazard Disaster Reduction.The project is sponsored by the International Lithosphere Program and funded by the USGS’s National Earthquake Hazards Reduction Program. The primary elements of the project are general supervision and interpretation of geologic/tectonic information, data compilation and entry for fault catalog, database design and management, and digitization and manipulation of data in †ARCINFO. For the compilation of data, we engaged experts in Quaternary faulting, neotectonics, paleoseismology, and seismology.

Protein Flexibility Facilitates Quaternary Structure Assembly and Evolution

PubMed Central

Marsh, Joseph A.; Teichmann, Sarah A.

2014-01-01

The intrinsic flexibility of proteins allows them to undergo large conformational fluctuations in solution or upon interaction with other molecules. Proteins also commonly assemble into complexes with diverse quaternary structure arrangements. Here we investigate how the flexibility of individual protein chains influences the assembly and evolution of protein complexes. We find that flexibility appears to be particularly conducive to the formation of heterologous (i.e., asymmetric) intersubunit interfaces. This leads to a strong association between subunit flexibility and homomeric complexes with cyclic and asymmetric quaternary structure topologies. Similarly, we also observe that the more nonhomologous subunits that assemble together within a complex, the more flexible those subunits tend to be. Importantly, these findings suggest that subunit flexibility should be closely related to the evolutionary history of a complex. We confirm this by showing that evolutionarily more recent subunits are generally more flexible than evolutionarily older subunits. Finally, we investigate the very different explorations of quaternary structure space that have occurred in different evolutionary lineages. In particular, the increased flexibility of eukaryotic proteins appears to enable the assembly of heteromeric complexes with more unique components. PMID:24866000

Pollen preservation and Quaternary environmental history in the southeastern United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delcourt, P.A.; Delcourt, H.R.

Reconstructions of Quaternary environmental history based upon modern pollen/vegetation/climate calibrations are more tenable if the factors responsible for variation in pollen assemblages are evaluated. Examination of the state of preservation of Quaternary palynomorphs provides quantitative data concerning the degree of information loss due to alteration of pollen assemblages by syndepositional and post-depositional deterioration. The percentage, concentration, and influx values for total indeterminable pollen are useful criteria in providing an objective and quantitative basis for evaluating the comparability of pollen spectra within and between sites. Supporting data concerning sediment particle-size distribution, organic matter content, and concentration, influx, and taxonomic composition ofmore » both determinable pollen and plant macrofossils aid in reconstructing past depositional environments. The potential is high for deterioration of pollen in sediments from the southeastern United States, although considerable variation is found in both kind and degree of deterioration between lacustrine and alluvial sites of different ages and in different latitudes. Modern analogs are a basis for late Quaternary environmental reconstructions when pollen deterioration has not significantly biased the information content of fossil pollen assemblages.« less

Cellular Membrane Phospholipids Act as a Depository for Quaternary Amine containing Drugs thus competing with the Acetylcholine / Nicotinic Receptor

PubMed Central

Barbacci, Damon; Jackson, Shelley N.; Muller, Ludovic; Egan, Thomas; Lewis, Ernest K.; Schultz, J. Albert; Woods, Amina S.

2014-01-01

We previously demonstrated that ammonium- or guanidinium- phosphate interactions are key to forming non-covalent complexes (NCXs) through salt bridge formation with G-protein coupled receptors (GPCR), which are immersed in the cell membrane's lipids. The present work highlights MALDI ion mobility coupled to orthogonal time-of-flight mass spectrometry (MALDI IM oTOF MS) as a method to determine qualitative and relative quantitative affinity of drugs to form NCXs with targeted GPCRs' epitopes in a model system using, bis-quaternary amine based drugs, α- and β- subunit epitopes of the nicotinic acetylcholine receptor' (nAChR) and phospholipids. Bis-quaternary amines proved to have a strong affinity for all nAChR epitopes and negatively charged phospholipids, even in the presence of the physiological neurotransmitter acetylcholine. Ion mobility baseline separated isobaric phosphatidyl ethanolamine and a matrix cluster, providing an accurate estimate for phospholipid counts. Overall this technique is a powerful method for screening drugs' interactions with targeted lipids and protein respectively containing quaternary amines and guanidinium moieties. PMID:22506649

Is Quaternary geology ready for the future?

NASA Astrophysics Data System (ADS)

Ritter, Dale F.

1996-07-01

Armed with a better understanding of process and an array of developing dating techniques, Quaternary geology is poised to achieve greater recognition in the general scientific community. This recognition however, will require some thought adjustment. Quaternary geologists will have to convince government, industry and a variety of scientific groups that they possess unique training and expertise that is needed as part of the thrust to fully understand and/or resolve major scientific problems. Therefore, future research and education efforts should not focus on developing a rigidly defined identity within geoscience, but instead should seek ways to be integrated with interdisciplinary teams that will investigate complex environmental and climate change problems. Such a scenaria creates and enermous dilemma for Quaternary geologists because they will derive greater intellectual stimulation from scientists working in discplines other than geology, and their scientific collaboratiors will most likely not be their academic colleagues. This outward expansion of our scientific network will require the development of interdsciplinary research collaboration and/or degree-granting programs at the graduate level. To accomplish such goals, universities must resist "turf protection", and funding agencies muts become more efficient at facilitating interdisciplinary research.

Hydrolysis of p-nitrophenyl esters promoted by semifluorinated quaternary ammonium polymer latexes and films.

PubMed

Kaur, Baljinder; McBride, Sean P; Paul, Abhijit; Ford, Warren T

2010-10-19

Semifluorinated polymer latexes were prepared by emulsion polymerization of 2.5-25% of a fluoroalkyl methacrylate, 25% chloromethylstyrene, 1% styrylmethyl(trimethyl)ammonium chloride, and the remainder 2-ethylhexyl methacrylate under surfactant-free conditions. The chloromethylstyrene units were converted to quaternary ammonium ions with trimethylamine. In aqueous dispersions at particle concentrations of less than 1 mg mL(-1) the quaternary ammonium ion latexes promoted hydrolyses of p-nitrophenyl hexanoate (PNPH) in pH 9.4 borate buffer and of diethyl p-nitrophenyl phosphate (Paraoxon) in 0.1 M NaOH at 30 °C with half-lives of less than 10 min. Thin 0.7-2 μm films of the latexes on glass promoted fast hydrolysis of Paraoxon but not of PNPH under the same conditions. Even after annealing the quaternary ammonium ion polymer films at temperatures well above their glass transition temperatures, AFM images of the film surfaces had textures of particles. Contact angle measurements of the annealed films against water and against hexadecane showed that the surfaces were not highly fluorinated.

Peptides derivatized with bicyclic quaternary ammonium ionization tags. Sequencing via tandem mass spectrometry.

PubMed

Setner, Bartosz; Rudowska, Magdalena; Klem, Ewelina; Cebrat, Marek; Szewczuk, Zbigniew

2014-10-01

Improving the sensitivity of detection and fragmentation of peptides to provide reliable sequencing of peptides is an important goal of mass spectrometric analysis. Peptides derivatized by bicyclic quaternary ammonium ionization tags: 1-azabicyclo[2.2.2]octane (ABCO) or 1,4-diazabicyclo[2.2.2]octane (DABCO), are characterized by an increased detection sensitivity in electrospray ionization mass spectrometry (ESI-MS) and longer retention times on the reverse-phase (RP) chromatography columns. The improvement of the detection limit was observed even for peptides dissolved in 10 mM NaCl. Collision-induced dissociation tandem mass spectrometry of quaternary ammonium salts derivatives of peptides showed dominant a- and b-type ions, allowing facile sequencing of peptides. The bicyclic ionization tags are stable in collision-induced dissociation experiments, and the resulted fragmentation pattern is not significantly influenced by either acidic or basic amino acid residues in the peptide sequence. Obtained results indicate the general usefulness of the bicyclic quaternary ammonium ionization tags for ESI-MS/MS sequencing of peptides. Copyright © 2014 John Wiley & Sons, Ltd.

Soft antimicrobial agents: synthesis and activity of labile environmentally friendly long chain quaternary ammonium compounds.

PubMed

Thorsteinsson, Thorsteinn; Másson, Már; Kristinsson, Karl G; Hjálmarsdóttir, Martha A; Hilmarsson, Hilmar; Loftsson, Thorsteinn

2003-09-11

A series of soft quaternary ammonium antimicrobial agents, which are analogues to currently used quaternary ammonium preservatives such as cetyl pyridinium chloride and benzalkonium chloride, were synthesized. These soft analogues consist of long alkyl chain connected to a polar headgroup via chemically labile spacer group. They are characterized by facile nonenzymatic and enzymatic degradation to form their original nontoxic building blocks. However, their chemical stability has to be adequate in order for them to have antimicrobial effects. Stability studies and antibacterial and antiviral activity measurements revealed relationship between activity, lipophilicity, and stability. Their minimum inhibitory concentration (MIC) was as low as 1 microg/mL, and their viral reduction was in some cases greater than 6.7 log. The structure-activity studies demonstrate that the bioactive compounds (i.e., MIC for Gram-positive bacteria of <10 microg/mL) have an alkyl chain length between 12 and 18 carbon atoms, with a polar headgroup preferably of a small quaternary ammonium group, and their acquired inactivation half-life must be greater than 3 h at 60 degrees C.

Physical, chemical and antimicrobial evaluation of a composite material containing quaternary ammonium salt for braces cementation.

PubMed

Sugii, Mari Miura; Ferreira, Fábio Augusto de Souza; Müller, Karina Cogo; Lima, Debora Alves Nunes Leite; Groppo, Francisco Carlos; Imasato, Hidetake; Rodrigues-Filho, Ubirajara Pereira; Aguiar, Flávio Henrique Baggio

2017-04-01

The antibiofilm effect of iodide quaternary ammonium methacryloxy silicate (IQAMS) in Transbond XT Light Cure Adhesive resin used for braces cementation was evaluated. Fourier Transform Infrared (FTIR) spectroscopy confirmed IQAMS formation and Scanning Electron Microscopy coupled to Energy-Dispersive X-ray Spectroscopy (SEM-EDS) revealed that as coating, the quaternary ammonium groups from IQAMS were homogeneously dispersed throughout the surface. When incorporated, the composite material presented homogeneous dispersion throughout the resin. Assays with Streptococcus mutans demonstrated enhanced antibiofilm effect for the IQAMS coated resin, with much lower colony-forming units (CFU), in comparison to incorporated IQAMS. Such a difference was assigned to low availability of quaternary ammonium groups at the surface of resin when IQAMS was incorporated, hindering its antibiofilm effect. Additionally, the incorporation of IQAMS led to slight decrease in ultimate bond strength (UBS) and shear bond strength (SBS), in comparison to the neat commercial resin. Thus, the synthesized IQAMS displays great potential as antibiofilm coating or sealant to prevent oral infections in brackets during orthodontic treatment. Copyright © 2016 Elsevier B.V. All rights reserved.

Spontaneous quaternary and tertiary T-R transitions of human hemoglobin in molecular dynamics simulation.

PubMed

Hub, Jochen S; Kubitzki, Marcus B; de Groot, Bert L

2010-05-06

We present molecular dynamics simulations of unliganded human hemoglobin (Hb) A under physiological conditions, starting from the R, R2, and T state. The simulations were carried out with protonated and deprotonated HC3 histidines His(beta)146, and they sum up to a total length of 5.6 micros. We observe spontaneous and reproducible T-->R quaternary transitions of the Hb tetramer and tertiary transitions of the alpha and beta subunits, as detected from principal component projections, from an RMSD measure, and from rigid body rotation analysis. The simulations reveal a marked asymmetry between the alpha and beta subunits. Using the mutual information as correlation measure, we find that the beta subunits are substantially more strongly linked to the quaternary transition than the alpha subunits. In addition, the tertiary populations of the alpha and beta subunits differ substantially, with the beta subunits showing a tendency towards R, and the alpha subunits showing a tendency towards T. Based on the simulation results, we present a transition pathway for coupled quaternary and tertiary transitions between the R and T conformations of Hb.

Spontaneous Quaternary and Tertiary T-R Transitions of Human Hemoglobin in Molecular Dynamics Simulation

PubMed Central

de Groot, Bert L.

2010-01-01

We present molecular dynamics simulations of unliganded human hemoglobin (Hb) A under physiological conditions, starting from the R, R2, and T state. The simulations were carried out with protonated and deprotonated HC3 histidines His(β)146, and they sum up to a total length of 5.6µs. We observe spontaneous and reproducible T→R quaternary transitions of the Hb tetramer and tertiary transitions of the α and β subunits, as detected from principal component projections, from an RMSD measure, and from rigid body rotation analysis. The simulations reveal a marked asymmetry between the α and β subunits. Using the mutual information as correlation measure, we find that the β subunits are substantially more strongly linked to the quaternary transition than the α subunits. In addition, the tertiary populations of the α and β subunits differ substantially, with the β subunits showing a tendency towards R, and the α subunits showing a tendency towards T. Based on the simulation results, we present a transition pathway for coupled quaternary and tertiary transitions between the R and T conformations of Hb. PMID:20463873

Extensive Quaternary glaciations in eastern Turkey

NASA Astrophysics Data System (ADS)

Yeşilyurt, Serdar; Akçar, Naki; Doǧan, Uǧur; Yavuz, Vural; Ivy-Ochs, Susan; Vockenhuber, Christof; Schlunegger, Fritz; Schlüchter, Christian

2016-04-01

During cold periods in the Quaternary, global ice volume increased and as a result valley glaciers advanced and the vice versa occurred during the warm periods. Quaternary glacier fluctuations had been also recorded in the Turkish mountains. Recently, the chronology of Late Quaternary advances in the northern and western Turkish mountains was reconstructed by surface exposure dating. However, these advances in the eastern Turkey are not dated yet. In this study, we investigated paleoglaciations in Kavuşşahap Mountains, which is located to the south of Lake Van in eastern Turkey. These mountains are one of the extensively glaciated areas in Turkey. Glacial activity is evidenced by more than 20 U-shaped valleys. For instance, one of the prominent and well-preserved glacial landscapes of Turkey is situated in the Narlıca valley system. Lateral and terminal moraines in the valley system indicate more than 10 glacial advances. To build their chronology, 39 erratic carbonaceous boulders were sampled for surface exposure dating with cosmogenic 36Cl. We also reconstructed the ice margin reconstruction of the Narlıca paleoglacier using the accumulation area ratio and area-altitude balance ratio approaches. We estimated an equilibrium line altitude (ELA) of ca. 2900 m above sea level based on the maximum ice extend, which implied ca. 800 m decrease in the ELA during the Late Quaternary in comparison to the lower bound of the modern ELA estimate. The first results of the surface exposure dating will be presented.

Plio-quaternary deposits in the Eastern Rharb (Nw Morocco): Electrosequential characterization

NASA Astrophysics Data System (ADS)

Al Mazini, Imane; Mridekh, Abdelaziz; Kili, Malika; El Mansouri, Bouâbid; El Bouhaddioui, Mohamed; Magrane, Bouchaib

2018-02-01

The Rharb basin, of which our study area is part, is located at the western extremity of the south Rif corridor. It corresponds to a subsiding zone that appeared in the Upper Miocene, between two major structural domains: the Rif to the north and east and the Meseta domain to the south. The eastern part of this basin is characterized by a Plio-Quaternary continental fill. Its geographical position and its structural and paleo-environmental contexts are reflected by a great facies heterogeneity. This work aims to image the subsurface structure and to characterize the distribution mode of Plio-Quaternary deposits of the eastern Rharb. The use of a database consisting of geo-electrical cross sections, hydrogeological drilling and wireline logging integrated in a Geographic Information System (GIS) allowed us to establish a new three-dimensional model of the top of the Mio-Pliocene substratum, new geo-electrical cross sections, as well as the isopach maps of lower, intermediate, upper and superficial geo-electric interval. This approach allowed us to characterize the Plio-Quaternary deposits of the study area and to highlight the effects of the tectonic regime and the relative sea level fluctuations on the sequential organization of these deposits. Our new model shows the development of prograding, aggrading and retrograding parasequences denoting the existence of autogenic mechanisms in the organization of plio-quaternary deposits of the eastern part of the Rharb basin. Therefore, it opens new perspectives for the exploration of water resources and monitoring their quality throughout the basin.

Specialization in Plant-Hummingbird Networks Is Associated with Species Richness, Contemporary Precipitation and Quaternary Climate-Change Velocity

PubMed Central

Dalsgaard, Bo; Magård, Else; Fjeldså, Jon; Martín González, Ana M.; Rahbek, Carsten; Olesen, Jens M.; Ollerton, Jeff; Alarcón, Ruben; Cardoso Araujo, Andrea; Cotton, Peter A.; Lara, Carlos; Machado, Caio Graco; Sazima, Ivan; Sazima, Marlies; Timmermann, Allan; Watts, Stella; Sandel, Brody; Sutherland, William J.; Svenning, Jens-Christian

2011-01-01

Large-scale geographical patterns of biotic specialization and the underlying drivers are poorly understood, but it is widely believed that climate plays an important role in determining specialization. As climate-driven range dynamics should diminish local adaptations and favor generalization, one hypothesis is that contemporary biotic specialization is determined by the degree of past climatic instability, primarily Quaternary climate-change velocity. Other prominent hypotheses predict that either contemporary climate or species richness affect biotic specialization. To gain insight into geographical patterns of contemporary biotic specialization and its drivers, we use network analysis to determine the degree of specialization in plant-hummingbird mutualistic networks sampled at 31 localities, spanning a wide range of climate regimes across the Americas. We found greater biotic specialization at lower latitudes, with latitude explaining 20–22% of the spatial variation in plant-hummingbird specialization. Potential drivers of specialization - contemporary climate, Quaternary climate-change velocity, and species richness - had superior explanatory power, together explaining 53–64% of the variation in specialization. Notably, our data provides empirical evidence for the hypothesized roles of species richness, contemporary precipitation and Quaternary climate-change velocity as key predictors of biotic specialization, whereas contemporary temperature and seasonality seem unimportant in determining specialization. These results suggest that both ecological and evolutionary processes at Quaternary time scales can be important in driving large-scale geographical patterns of contemporary biotic specialization, at least for co-evolved systems such as plant-hummingbird networks. PMID:21998716

Demographic stability and high historical connectivity explain the diversity of a savanna tree species in the Quaternary

PubMed Central

Telles, Mariana P. C.; Chaves, Lázaro J.; Lima-Ribeiro, Matheus S.; Collevatti, Rosane G.

2017-01-01

Abstract Background and Aims Cyclic glaciations were frequent throughout the Quaternary and this affected species distribution and population differentiation worldwide. The present study reconstructed the demographic history and dispersal routes of Eugenia dysenterica lineages and investigated the effects of Quaternary climate change on its spatial pattern of genetic diversity. Methods A total of 333 individuals were sampled from 23 populations and analysed by sequencing four regions of the chloroplast DNA and the internal transcribed spacer of the nuclear DNA. The analyses were performed using a multi-model inference approach based on ecological niche modelling and statistical phylogeography. Key Results Coalescent simulation showed that population stability through time is the most likely scenario. The palaeodistribution dynamics predicted by the ecological niche models revealed that the species was potentially distributed across a large area, extending over Central-Western Brazil through the last glaciation. The lineages of E. dysenterica dispersed from Central Brazil towards populations at the northern, western and south-eastern regions. A historical refugium through time may have favoured lineage dispersal and the maintenance of genetic diversity. Conclusions The results suggest that the central region of the Cerrado biome is probably the centre of distribution of E. dysenterica and that the spatial pattern of its genetic diversity may be the outcome of population stability throughout the Quaternary. The lower genetic diversity in populations in the south-eastern Cerrado biome is probably due to local climatic instability during the Quaternary. PMID:28115317

Geology and ground-water resources of the northern part of the Ranegras Plain area, Yuma County, Arizona

USGS Publications Warehouse

Metzger, Donald George

1951-01-01

The Ranegras Plain area is part of the Basin and Range province in west-central Arizona. The report discusses rocks of pre-Cambrian, pre-Cambrian (?), Paleozoic (?), Mesozoic (?), Cretaceous (?), Cretaceous and Tertiary, Tertiary (?), Quaternary (?), and Quaternary age. All the Paleozoic (?) and Cretaceous (?) rocks and parts of the Mesozoic (?),Cretaceous and Tertiary, and Tertiary (?) rocks have been mapped as a unit because they are so intensely faulted that detailed mapping was not practical. Rocks older than Quaternary form the mountain ranges bordering the Ranegras Plain. Quaternary alluvium underlies the broad, gently sloping valley floor to depths of generally a few hundred feet, locally more. Well logs indicate that the underlying Tertiary (?) alluvium exceeds 1,100 feet in thickness. The structure of the area is controlled by faulting typical of the Basin and Range province, but the major faults are covered by alluvium and are inferred from topographic features. Ground water occurs in Quaternary and Tertiary (?) alluvium and the best aquifers are in sand and gravel of the Quaternary alluvium. Ground-water movement is, in general, to the northwest. Recharge to the aquifers is predominantly from stream flow resulting from heavy rains. There is also minor or unevaluated recharge from underflow from Butler Valley to the east, andsince 1948seepage from irrigation. Discharge is by pumping and by natural processes of underflow and evapotranspiration. In addition to small domestic and stock wells, only two irrigation wells, in the vicinity of Utting, are in use. No accurate data on pumpage are available. The safe yield from the ground-water reservoir may be less than 5,000 acre-feet and probably does not exceed 10,000 to 15,000 acre-feet per year. The quality of ground water ranges from permissible to unsuitable for irrigation purposes. The fluoride content is generally too high for the water to be considered satisfactory for use by young children.

The southern Whidbey Island fault: An active structure in the Puget Lowland, Washington

USGS Publications Warehouse

Johnson, S.Y.; Potter, C.J.; Armentrout, J.M.; Miller, J.J.; Finn, C.; Weaver, C.S.

1996-01-01

Information from seismic-reflection profiles, outcrops, boreholes, and potential field surveys is used to interpret the structure and history of the southern Whidbey Island fault in the Puget Lowland of western Washington. This northwest-trending fault comprises a broad (as wide as 6-11 km), steep, northeast-dipping zone that includes several splays with inferred strike-slip, reverse, and thrust displacement. Transpressional deformation along the southern Whidbey Island fault is indicated by alongstrike variations in structural style and geometry, positive flower structure, local unconformities, out-of-plane displacements, and juxtaposition of correlative sedimentary units with different histories. The southern Whidbey Island fault represents a segment of a boundary between two major crustal blocks. The Cascade block to the northeast is floored by diverse assemblages of pre-Tertiary rocks; the Coast Range block to the southwest is floored by lower Eocene marine basaltic rocks of the Crescent Formation. The fault probably originated during the early Eocene as a dextral strike-slip fault along the eastern side of a continental-margin rift. Bending of the fault and transpressional deformation began during the late middle Eocene and continues to the present. Oblique convergence and clockwise rotation along the continental margin are the inferred driving forces for ongoing deformation. Evidence for Quaternary movement on the southern Whidbey Island fault includes (1) offset and disrupted upper Quaternary strata imaged on seismic-reflection profiles; (2) borehole data that suggests as much as 420 m of structural relief on the Tertiary-Quaternary boundary in the fault zone; (3) several meters of displacement along exposed faults in upper Quaternary sediments; (4) late Quaternary folds with limb dips of as much as ???9??; (5) large-scale liquefaction features in upper Quaternary sediments within the fault zone; and (6) minor historical seismicity. The southern Whidbey Island fault should be considered capable of generating large earthquakes (Ms ???7) and represents a potential seismic hazard to residents of the Puget Lowland.

The metal oxide fraction of pelagic sediment in the equatorial North Pacific Ocean: A source of metals in ferromanganese nodules

USGS Publications Warehouse

Piper, D.Z.

1988-01-01

Pelagic sediment recovered at DOMES Site A in the equatorial North Pacific (151??W, 9?? 15???N) consists of a surface homogeneous layer, approximately 10 cm thick, overlying a strongly mottled layer that is lighter in color. The radiolarian composition of both units is Quaternary. In areas where this sediment was only a few centimeters thick, the underlying sediment was early Tertiary. Clay mineralogy and major oxide composition of the two Quaternary sediments are uniform. Their similarity to continental shale suggests that the sediment has a terrigenous source. Clay mineralogy and major oxide composition of the Tertiary sediment also are uniform, although they differ markedly from the Quarternary sediment. In contrast to the major oxides, concentrations of Mn, Co, Cu, and Ni soluble in hydroxylamine hydrochlorideacetic acid are strongly different in the surface and subsurface Quaternary sediment. Mn and Ni exhibit pronounced depletions in the subsurface sediment, Ni slightly more than Mn. Cu is also depleted in the subsurface sediment, but less than Mn. It is also depleted in the subsurface Tertiary sediment, whereas the Mn concentration remains high. Concentration of Co relative to Mn increases into the subsurface Quaternary sediment to a constant Co:Mn ratio of 3 ?? 10-2. The trivalent REE (the REE exclusive of Ce) and Fe exhibit little down-core variation. Distribution of elements in these sediments is closely related to their concentration in associated surface ferromanganese nodules. The nodules are of two distinct types: those from the area where the Quaternary sediment is relatively thick have ??-MnO2 as the dominant manganese mineral. The ratios of Ni:Mn, Cu:Mn, and Fe:Mn in these nodules approximate the corresponding ratios of the soluble fraction of surface sediment. Todorokite is the dominant mineral of nodules recovered from areas where the Quaternary sediment is thin. Relatively high Cu/Mn, Ni/Mn, and low Fe/Mn ratios of these nodules mirror differences between the soluble fraction of surface and subsurface Quaternary sediment. These compositional trends of sediment and nodules at DOMES Site A reflect a diagenetic origin for the todorokite nodules and a predominantly hydrogenous origin for the ??-MnO2 nodules. ?? 1988.

Quantification of the Thermodynamically Linked Quaternary and Tertiary Structural Stabilities of Transthyretin and its Disease-Associated Variants–the Relationship between Stability and Amyloidosis†

PubMed Central

Hurshman Babbes, Amy R.; Powers, Evan T.; Kelly, Jeffery W.

2009-01-01

Urea denaturation studies were carried out as a function of transthyretin (TTR) concentration to quantify the thermodynamically linked quaternary and tertiary structural stability and to better understand the relationship between mutant folding energetics and amyloid disease phenotype. Urea denaturation of TTR involves at least two equilibria—dissociation of tetramers into folded monomers, and monomer unfolding. To deal with the thermodynamic linkage of these equilibria, we analyzed concentration-dependent denaturation data by global fitting to an equation that simultaneously accounts for the two-step denaturation process. Using this method, the quaternary and tertiary structural stabilities of well-behaved TTR sequences, wild type (WT) TTR and the disease-associated variant V122I, were scrutinized. The V122I variant is linked to late onset familial amyloid cardiomyopathy, the most common familial TTR amyloid disease. V122I TTR exhibits a destabilized quaternary structure and a stable tertiary structure relative to WT TTR. Three other variants of TTR were also examined, L55P, V30M, and A25T TTR. The L55P mutation is associated with the most aggressive familial TTR amyloid disease. L55P TTR has a complicated denaturation pathway that includes dimers and trimers, and so globally fitting its concentration-dependent urea denaturation data yielded error-laden estimates of stability parameters. Nevertheless, it is clear that L55P TTR is substantially less stable than WT TTR, primarily because its tertiary structure is unstable, although its quaternary structure is destabilized as well. V30M is the most common mutation associated with neuropathic forms of TTR amyloid disease. V30M TTR is certainly destabilized relative to WT TTR, but like L55P TTR it has a complex denaturation pathway that cannot be fit to the aforementioned two-step denaturation model. Literature data suggest that V30M TTR has stable quaternary structure but unstable tertiary structure. The A25T mutant, associated with central nervous system amyloidosis, is highly aggregation-prone and exhibits drastically reduced quaternary and tertiary structural stability. The observed differences in stability amongst the disease-associated TTR variants highlight the complexity and the heterogeneity of TTR amyloid disease, an observation having important implications for the treatment of these diseases. PMID:18537267

Data for Quaternary faults, liquefaction features, and possible tectonic features in the Central and Eastern United States, east of the Rocky Mountain Front

USGS Publications Warehouse

Crone, Anthony J.; Wheeler, Russell L.

2000-01-01

The USGS is currently leading an effort to compile published geological information on Quaternary faults, folds, and earthquake-induced liquefaction in order to develop an internally consistent database on the locations, ages, and activity rates of major earthquake-related features throughout the United States. This report is the compilation for such features in the Central and Eastern United States (CEUS), which for the purposes of the compilation, is defined as the region extending from the Rocky Mountain Front eastward to the Atlantic seaboard. A key objective of this national compilation is to provide a comprehensive database of Quaternary features that might generate strong ground motion and therefore, should be considered in assessing the seismic hazard throughout the country. In addition to printed versions of regional and individual state compilations, the database will be available on the World-Wide Web, where it will be readily available to everyone. The primary purpose of these compilations and the derivative database is to provide a comprehensive, uniform source of geological information that can by used to complement the other types of data that are used in seismic-hazard assessments. Within our CEUS study area, which encompasses more than 60 percent of the continuous U.S., we summarize the geological information on 69 features that are categorized into four classes (Class A, B, C, and D) based on what is known about the feature's Quaternary activity. The CEUS contains only 13 features of tectonic origin for which there is convincing evidence of Quaternary activity (Class A features). Of the remaining 56 features, 11 require further study in order to confidently define their potential as possible sources of earthquake-induced ground motion (Class B), whereas the remaining features either lack convincing geologic evidence of Quaternary tectonic faulting or have been studied carefully enough to determine that they do not pose a significant seismic hazard (Classes C and D). The correlation between historical seismicity and Quaternary faults and liquefaction features in the CEUS is generally poor, which probably reflects the long return times between successive movements on individual structures. Some Quaternary faults and liquefaction features are located in aseismic areas or where historical seismicity is sparse. These relations indicate that the record of historical seismicity does not identify all potential seismic sources in the CEUS. Furthermore, geological studies of some currently aseismic faults have shown that the faults have generated strong earthquakes in the geologically recent past. Thus, the combination of geological information and seismological data can provide better insight into potential earthquake sources and thereby, contribute to better, more comprehensive seismic-hazard assessments.

Origin, Extent, and Thickness of Quaternary Geologic Units in the Willamette Valley, Oregon

USGS Publications Warehouse

O'Connor, Jim E.; Sarna-Wojcicki, Andrei M.; Wozniak, Karl C.; Polette, Danial J.; Fleck, Robert J.

2001-01-01

Stratigraphic and chronologic information collected for Quaternary deposits in the Willamette Valley, Oregon, provides a revised stratigraphic framework that serves as a basis for a 1:250,000-scale map, as well as for thickness estimates of widespread Quaternary geologic units. We have mapped 11 separate Quaternary units that are differentiated on the basis of stratigraphic, topographic, pedogenic, and hydrogeologic properties. In summation, these units reflect four distinct episodes in the Quaternary geologic development of the Willamette Valley: 1) Fluvial sands and gravels that underlie terraces flanking lowland margins and tributary valleys were probably deposited between 2.5 and 0.5 million years ago. They are the oldest widespread surficial Quaternary deposits in the valley. Their present positions and preservation are undoubtedly due to postdepositional tectonic deformation - either by direct tectonic uplift of valley margins, or by regional tectonic controls on local base level. 2) Tertiary and Quaternary excavation or tectonic lowering of the Willamette Valley accommodated as much as 500 m (meters) of lacustrine and fluvial fill. Beneath the lowland floor, much of the upper 10 to 50 m of fill is Quaternary sand and gravel deposited by braided channel systems in subhorizontal sheets 2 to 10 m thick. These deposits grade to gravel fans 40 to 100 m thick where major Cascade Range rivers enter the valley and are traced farther upstream as much thinner valley trains of coarse gravel. The sand and gravel deposits have ages that range from greater than 420,000 to about 12,000 years old. A widely distributed layer of sand and gravel deposited at about 12 ka (kiloannum, thousands of years before the present) is looser and probably more permeable than older sand and gravel. Stratigraphic exposures and drillers' logs indicate that this late Pleistocene unit is mostly between 5 and 20 m thick where it has not been subsequently eroded by the Willamette River and its major tributaries. 3) Between 15,000 and 12,700 years ago, dozens of floods from Glacial Lake Missoula flowed up the Willamette Valley from the Columbia River, depositing up to 35 m of gravel, sand, silt, and clay. 4) Subsequent to 12,000 years ago, Willamette River sediment and flow regimes changed significantly: the Pleistocene braided river systems that had formed vast plains of sand and gravel evolved to incised and meandering rivers that are constructing today's fine-grained floodplains and gravelly channel deposits. Sub-surface channel facies of this unit are loose and unconsolidated and are highly permeable zones of substantial groundwater flow that is likely to be well connected to surface flow in the Willamette River and major tributaries. Stratigraphic exposures and drillers' logs indicate that this unit is mostly between 5 and 15 m thick.

Perpendicular Growth Characteristics of Cu-Sn Intermetallic Compounds at the Surface of 99Sn-1Cu/Cu Solder Interconnects

NASA Astrophysics Data System (ADS)

Chen, Zhiwen; Liu, Changqing; Wu, Yiping; An, Bing

2015-12-01

The growth of intermetallic compounds (IMCs) on the free surface of 99Sn-1Cu solder joints perpendicular to the interdiffusion direction has been investigated in this work. The specimens were specifically designed and polished to reveal a flat free surface at the solder/Cu interface for investigation. After aging at 175°C for progressively increased durations, the height of the perpendicular IMCs was examined and found to follow a parabolic law with aging duration that could be expressed as y = 0.11√ t, where t is the aging duration in hours and y is the height of the perpendicular IMCs in μm. For comparison, the planar growth of IMCs along the interdiffusion direction was also investigated in 99Sn-1Cu/Cu solder joints. After prolonged aging at 175°C, the thickness of the planar interfacial IMC layers also increased parabolically with aging duration and could be expressed as h_{{IMC}} = 0.27√ t + 4.6, where h is the thickness in μm and t is the time in hours. It was found that both the planar and perpendicular growth of the IMCs were diffusion-controlled processes, but the perpendicular growth of the IMCs was much slower than their planar growth due to the longer diffusion distance. It is proposed that Cu3Sn forms prior to the formation of Cu6Sn5 in the perpendicular IMCs, being the reverse order compared with the planar IMC growth.

Complete genome sequence of Campylobacter jejuni RM1246-ERRC that exhibits resistance to Quaternary Ammonium Compounds

USDA-ARS?s Scientific Manuscript database

Campylobacter jejuni strain RM1246-ERRC is a clinical isolate. In laboratory experiments RM1246-ERRC exhibited resistance to the antimicrobial effects of quaternary ammonium compounds (QACs) when compared to other C. jejuni strains. The chromosome of RM1246-ERRC was determined to be 1,659,694 bp w...

Synthesis of Quaternary Ammonium Salts of Tricyclic Cationic Drugs: A One-Pot Synthesis for the Bioorganic Chemistry Laboratory

ERIC Educational Resources Information Center

Brunauer, Linda S.; Mogannam, Abid C.; Hwee, Won B.; Chen, James Y.

2007-01-01

A one-pot conversion of tricyclic cationic drugs to their quaternary ammonium forms is described for a widely used bioactive drug: chlorpromazine, a phenothiazine-based antipsychotic. After conversion to its free base, the parent drug was methylated using substoichiometric amounts of methyl iodide dissolved in ether; the charged quaternary…

Quaternary geology and geomorphology of the lower Deschutes River Canyon, Oregon.

Treesearch

Jim E. O' Connor; Janet H. Curran; Robin A. Beebee; Gordon E. Grant; Andrei Sarna-Wojcicki

2003-01-01

The morphology of the Deschutes River canyon downstream of the Pelton-Round Butte dam complex is the product of the regional geologic history, the composition of the geologic units that compose the valley walls, and Quaternary processes and events. Geologic units within the valley walls and regional deformation patterns control overall valley morphology. Valley bottom...

Community ecology in a changing environment: Perspectives from the Quaternary

NASA Astrophysics Data System (ADS)

Jackson, Stephen T.; Blois, Jessica L.

2015-04-01

Community ecology and paleoecology are both concerned with the composition and structure of biotic assemblages but are largely disconnected. Community ecology focuses on existing species assemblages and recently has begun to integrate history (phylogeny and continental or intercontinental dispersal) to constrain community processes. This division has left a "missing middle": Ecological and environmental processes occurring on timescales from decades to millennia are not yet fully incorporated into community ecology. Quaternary paleoecology has a wealth of data documenting ecological dynamics at these timescales, and both fields can benefit from greater interaction and articulation. We discuss ecological insights revealed by Quaternary terrestrial records, suggest foundations for bridging between the disciplines, and identify topics where the disciplines can engage to mutual benefit.

Community ecology in a changing environment: Perspectives from the Quaternary

PubMed Central

Jackson, Stephen T.; Blois, Jessica L.

2015-01-01

Community ecology and paleoecology are both concerned with the composition and structure of biotic assemblages but are largely disconnected. Community ecology focuses on existing species assemblages and recently has begun to integrate history (phylogeny and continental or intercontinental dispersal) to constrain community processes. This division has left a “missing middle”: Ecological and environmental processes occurring on timescales from decades to millennia are not yet fully incorporated into community ecology. Quaternary paleoecology has a wealth of data documenting ecological dynamics at these timescales, and both fields can benefit from greater interaction and articulation. We discuss ecological insights revealed by Quaternary terrestrial records, suggest foundations for bridging between the disciplines, and identify topics where the disciplines can engage to mutual benefit. PMID:25901314

Local Bonding Influence on the Band Edge and Band Gap Formation in Quaternary Chalcopyrites.

PubMed

Miglio, Anna; Heinrich, Christophe P; Tremel, Wolfgang; Hautier, Geoffroy; Zeier, Wolfgang G

2017-09-01

Quaternary chalcopyrites have shown to exhibit tunable band gaps with changing anion composition. Inspired by these observations, the underlying structural and electronic considerations are investigated using a combination of experimentally obtained structural data, molecular orbital considerations, and density functional theory. Within the solid solution Cu 2 ZnGeS 4- x Se x , the anion bond alteration parameter changes, showing larger bond lengths for metal-selenium than for metal-sulfur bonds. The changing bonding interaction directly influences the valence and conduction band edges, which result from antibonding Cu-anion and Ge-anion interactions, respectively. The knowledge of the underlying bonding interactions at the band edges can help design properties of these quaternary chalcopyrites for photovoltaic and thermoelectric applications.

Survey of Portions of the Chromium-Cobalt-Nickel-Molybdenum Quaternary System at 1,200 Degrees C

NASA Technical Reports Server (NTRS)

Rideout, Sheldon Paul; Beck, Paul A

1953-01-01

A survey was made of portions of the chromium-cobalt-nickel-molybdenum quaternary system at 1,200 degrees c by means of microscopic and x-ray diffraction studies. Since the face-centered cubic (alpha) solid solutions form the matrix of almost all practically useful high-temperature alloys, the solid solubility limits of the quaternary alpha phase were determined up to 20 percent molybdenum. The component cobalt-nickel-molybdenum, chromium-cobalt-molybdenum, and chromium-nickel-molybdenum ternary systems were also studied. The survey of these systems was confined to the determination of the boundaries of the face-centered cubic (alpha) solid solutions and of the phases coexisting with alpha at 1,200 degrees c.

Process for purification of waste water produced by a Kraft process pulp and paper mill

NASA Technical Reports Server (NTRS)

Humphrey, M. F. (Inventor)

1979-01-01

The water from paper and pulp wastes obtained from a mill using the Kraft process is purified by precipitating lignins and lignin derivatives from the waste stream with quaternary ammonium compounds, removing other impurities by activated carbon produced from the cellulosic components of the water, and then separating the water from the precipitate and solids. The activated carbon also acts as an aid to the separation of the water and solids. If recovery of lignins is also desired, then the precipitate containing the lignins and quaternary ammonium compounds is dissolved in methanol. Upon acidification, the lignin is precipitated from the solution. The methanol and quaternary ammonium compound are recovered for reuse from the remainder.

Enantioselective Synthesis of All-Carbon Quaternary Centers Structurally Related to Amaryllidaceae Alkaloids.

PubMed

Mikušek, Jiří; Jansa, Petr; Jagtap, Pratap R; Vašíček, Tomáš; Císařová, Ivana; Matoušová, Eliška

2018-05-18

Enantioselective synthesis of all-carbon quaternary centers remains a considerable challenge for synthetic organic chemists. Here, we report a two-step protocol to synthesize such centers including tandem cyclization/Suzuki cross-coupling followed by halocarbocyclization. During this process, two rings, three new C-C bonds and a stereochemically defined all-carbon quaternary center are formed. The absolute configuration of this center is controlled by the stereochemistry of the adjacent stereocenter, which derives from an appropriate enantioenriched starting material. Using this method, we synthesized polycyclic compounds structurally similar to Amaryllidaceae alkaloids in high enantiomeric excesses. Because these products resemble naturally occurring compounds, our protocol can be used to synthesize various potentially bioactive compounds. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Community ecology in a changing environment: Perspectives from the Quaternary

USGS Publications Warehouse

Jackson, Stephen T.; Blois, Jessica L.

2015-01-01

Community ecology and paleoecology are both concerned with the composition and structure of biotic assemblages but are largely disconnected. Community ecology focuses on existing species assemblages and recently has begun to integrate history (phylogeny and continental or intercontinental dispersal) to constrain community processes. This division has left a “missing middle”: Ecological and environmental processes occurring on timescales from decades to millennia are not yet fully incorporated into community ecology. Quaternary paleoecology has a wealth of data documenting ecological dynamics at these timescales, and both fields can benefit from greater interaction and articulation. We discuss ecological insights revealed by Quaternary terrestrial records, suggest foundations for bridging between the disciplines, and identify topics where the disciplines can engage to mutual benefit.

Quaternary and quinary modifications of eutectic superalloys strengthened by delta Ni3Cb lamellae and gamma prime Ni3Al precipitates

NASA Technical Reports Server (NTRS)

Lemkey, F. D.; Mccarthy, G. P.

1975-01-01

By means of a compositional and heat treatment optimization program based on the quaternary gamma/gamma prime-delta, a tantalum modified gamma/gamma prime-delta alloy with improved shear and creep strength combined with better cyclic oxidation resistance was identified. Quinary additions, quaternary adjustments, and heat treatment were investigated. The tantalum modified gamma/gamma prime-delta alloy possessed a slightly higher liquidus temperature and exhibited rupture strength exceeding NASA VIA by approximately three and one-half Larson-Miller parameters (C = 20) above 1000 C. Although improvements in longitudinal mechanical properties were achieved, the shear and transverse strength property goals of the program were not met and present a continuing challenge to the alloy metallurgist.

Microtitration of various anions with quaternary ammonium halides using solid-state electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Selig, W.

1980-01-01

Many solid-state electrodes were found to respond as endpoint detectors in the potentiometric titration of large inorganic and organic anions with quaternary ammonium halides. The best response was obtained with the iodide and cyanide electrodes although practically any electrode can function as endpoint sensor. The titrants were hexadecylpyridinium chloride and hexadecyltrimethylammonium chloride; hexadecyltrimethylammonium bromide and Hyamine 1622 may also be used. Some inorganic anions thus titratable are perrhenate, persulfate, ferricyanide, hexafluorophosphate, and hexachloroplatinate. Examples of organic anions titratable are nitroform, tetraphenylborate, cyanotriphenylborate, picrate, long-chain sulfates and sulfonates, and some soaps. The reverse titration of quaternary ammonium halides vs dodecylsulfate ismore » also feasible. Some titrations are feasible in a partially nonaqueous medium.« less

Community ecology in a changing environment: Perspectives from the Quaternary.

PubMed

Jackson, Stephen T; Blois, Jessica L

2015-04-21

Community ecology and paleoecology are both concerned with the composition and structure of biotic assemblages but are largely disconnected. Community ecology focuses on existing species assemblages and recently has begun to integrate history (phylogeny and continental or intercontinental dispersal) to constrain community processes. This division has left a "missing middle": Ecological and environmental processes occurring on timescales from decades to millennia are not yet fully incorporated into community ecology. Quaternary paleoecology has a wealth of data documenting ecological dynamics at these timescales, and both fields can benefit from greater interaction and articulation. We discuss ecological insights revealed by Quaternary terrestrial records, suggest foundations for bridging between the disciplines, and identify topics where the disciplines can engage to mutual benefit.

Combined Hydrous Ferric Oxide and Quaternary Ammonium Surfactant Tailoring of Granular Activated Carbon for Concurrent Arsenate and Perchlorate Removal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jang, M.; Cannon, F; Parette, R

2009-01-01

Activated carbon was tailored with both iron and quaternary ammonium surfactants so as to concurrently remove both arsenate and perchlorate from groundwater. The iron (hydr)oxide preferentially removed the arsenate oxyanion but not perchlorate; while the quaternary ammonium preferentially removed the perchlorate oxyanion, but not the arsenate. The co-sorption of two anionic oxyanions via distinct mechanisms has yielded intriguing phenomena. Rapid small-scale column tests (RSSCTs) with these dually prepared media employed synthetic waters that were concurrently spiked with arsenate and perchlorate; and these trial results showed that the quaternary ammonium surfactants enhanced arsenate removal bed life by 25-50% when compared tomore » activated carbon media that had been preloaded merely with iron (hydr)oxide; and the surfactant also enhanced the diffusion rate of arsenate per the Donnan effect. The authors also employed natural groundwater from Rutland, MA which contained 60 microg/L As and traces of silica, and sulfate; and the authors spiked this with 40 microg/L perchlorate. When processing this water, activated carbon that had been tailored with iron and cationic surfactant could treat 12,500 bed volumes before 10 microg/L arsenic breakthrough, and 4500 bed volumes before 6 microg/L perchlorate breakthrough. Although the quaternary ammonium surfactants exhibited only a slight capacity for removing arsenate, these surfactants did facilitate a more favorably positively charged avenue for the arsenate to diffuse through the media to the iron sorption site (i.e. via the Donnan effect).« less

Synthesis, crystal structure and electrical properties of the tetrahedral quaternary chalcogenides CuM{sub 2}InTe{sub 4} (M=Zn, Cd)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nolas, George S., E-mail: gnolas@usf.edu; Hassan, M. Shafiq; Dong, Yongkwan

Quaternary chalcogenides form a large class of materials that continue to be of interest for energy-related applications. Certain compositions have recently been identified as possessing good thermoelectric properties however these materials typically have the kesterite structure type with limited variation in composition. In this study we report on the structural, optical and electrical properties of the quaternary chalcogenides CuZn{sub 2}InTe{sub 4} and CuCd{sub 2}InTe{sub 4} which crystallize in the modified zinc-blende crystal structure, and compare their properties with that of CuZn{sub 2}InSe{sub 4}. These p-type semiconductors have direct band gaps of about 1 eV resulting in relatively high Seebeck coefficientmore » and resistivity values. This work expands on the research into quaternary chalcogenides with new compositions and structure types in order to further the fundamental investigation of multinary chalcogenides for potential thermoelectrics applications. - Graphical abstract: The structural, optical and electrical properties of the quaternary chalcogenides CuZn{sub 2}InTe{sub 4} and CuCd{sub 2}InTe{sub 4} are reported for the first time. The unique crystal structure allows for relatively good electrical transports and therefore potential for thermoelectric applications. - Highlights: • The physical properties of CuZn{sub 2}InTe{sub 4} and CuCd{sub 2}InTe{sub 4} are reported for the first time. • These materials have potential for thermoelectric applications. • Their direct band gaps also suggest potential for photovoltaics applications.« less

Geographic and stratigraphic distribution of coastal Quaternary aminozones across the Cape Fear Arch, U. S. Atlantic Geology Coastal Plain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wehmiller, J.F.; York, L.L.; Krantz, D.E.

1992-01-01

The interpretation of the regional aminostratigraphy of Coastal Plain Quaternary units from North and South Carolina is potentially affected by sampling biases, variable preservation of coastal records, reoccupation of coastal environments by multiple transgressions, geochemical alteration of samples, variable thermal histories of specific samples, and intergeneric and interlaboratory differences in analytical results.Two primary models for the correlation of emergent Coastal Plain units diverge significantly in southeastern North Carolina. New data from fresh exposure (1990--1991) at emergent sites between Wilmington, NC and Charleston, SC, from previous onshore collections in this region, and from submergent samples between Cape Lookout, NC and Capemore » Romain, SC provide insight into the nature of these correlation issues. Although sampling of the area is not uniform, these results fill a major gap between regions of previous aminostratigraphy study. Inferred early-to-middle Pleistocene aminozones dominate the emergent coastal region between Cape Lookout and Romain, and late Pleistocene aminozones in this area are represented by subsurface samples beneath barrier islands or in shallow inner shelf cores, but have not been found onshore. A map view of the distribution of aminozones along the coast between northeastern NC and central SC mimics that of pre-Quaternary units that thin or disappear over the axis of the Cape Fear Arch, suggesting that the sampled Quaternary record reflects the combination of processes responsible for the preservation of the pre-Quaternary record. This perspective should provide a model for resolution of various geochronological controversies that have arisen because of limited stratigraphic or geochemical data.« less

Neotectonic reactivation of shear zones and implications for faulting style and geometry in the continental margin of NE Brazil

NASA Astrophysics Data System (ADS)

Bezerra, F. H. R.; Rossetti, D. F.; Oliveira, R. G.; Medeiros, W. E.; Neves, B. B. Brito; Balsamo, F.; Nogueira, F. C. C.; Dantas, E. L.; Andrades Filho, C.; Góes, A. M.

2014-02-01

The eastern continental margin of South America comprises a series of rift basins developed during the breakup of Pangea in the Jurassic-Cretaceous. We integrated high resolution aeromagnetic, structural and stratigraphic data in order to evaluate the role of reactivation of ductile, Neoproterozoic shear zones in the deposition and deformation of post-rift sedimentary deposits in one of these basins, the Paraíba Basin in northeastern Brazil. This basin corresponds to the last part of the South American continent to be separated from Africa during the Pangea breakup. Sediment deposition in this basin occurred in the Albian-Maastrichtian, Eocene-Miocene, and in the late Quaternary. However, our investigation concentrates on the Miocene-Quaternary, which we consider the neotectonic period because it encompasses the last stress field. This consisted of an E-W-oriented compression and a N-S-oriented extension. The basement of the basin forms a slightly seaward-tilted ramp capped by a late Cretaceous to Quaternary sedimentary cover ~ 100-400 m thick. Aeromagnetic lineaments mark the major steeply-dipping, ductile E-W- to NE-striking shear zones in this basement. The ductile shear zones mainly reactivated as strike-slip, normal and oblique-slip faults, resulting in a series of Miocene-Quaternary depocenters controlled by NE-, E-W-, and a few NW-striking faults. Faulting produced subsidence and uplift that are largely responsible for the present-day morphology of the valleys and tablelands in this margin. We conclude that Precambrian shear zone reactivation controlled geometry and orientation, as well as deformation of sedimentary deposits, until the Neogene-Quaternary.

Late Quaternary transgressive large dunes on the sediment-starved Adriatic shelf

USGS Publications Warehouse

Correggiari, A.; Field, M.E.; Trincardi, F.

1996-01-01

The Adriatic epicontinental basin is a low-gradient shelf where the late-Quaternary transgressive systems tract (TST) is composed of thin parasequences of backbarrier, shoreface and offshore deposits. The facies and internal architecture of the late-Quaternary TST in the Adriatic epicontinental basin changed consistently from early transgression to late transgression reflecting: (1) fluctuations in the balance between sediment supply and accommodation increase, and (2) a progressive intensification of the oceanographic regime, driven by the transgressive widening of the basin to as much as seven times its lowstand extent. One of the consequences of this trend is that high-energy marine bedforms such as sand ridges and sand waves characterize only areas that were flooded close to the end of the late-Quaternary sea-level rise, when the wind fetch was maximum and bigger waves and stronger storm currents could form. We studied the morphology, sediment composition and sequence-stratigraphical setting of a field of asymmetric bedforms (typically 3 m high and 600 m in wavelength) in 20-24 m water depth offshore the Venice Lagoon in the sediment-starved North Adriatic shelf. The sand that forms these large dunes derived from a drowned transgressive coastal deposit reworked by marine processes. Early cementation took place over most of the dune crests limiting their activity and preventing their destruction. Both the formation and deactivation of this field of sand dunes occurred over a short time interval close to the turn-around point that separates the late-Quaternary sea-level rise and the following highstand and reflect rapid changes in the oceanographic regime of the basin.

Surface protection overview

NASA Technical Reports Server (NTRS)

Levine, S. R.

1982-01-01

A first-cut integrated environmental attack life prediction methodology for hot section components is addressed. The HOST program is concerned with oxidation and hot corrosion attack of metallic coatings as well as their degradation by interdiffusion with the substrate. The effects of the environment and coatings on creep/fatigue behavior are being addressed through a joint effort with the Fatigue sub-project. An initial effort will attempt to scope the problem of thermal barrier coating life prediction. Verification of models will be carried out through benchmark rig tests including a 4 atm. replaceable blade turbine and a 50 atm. pressurized burner rig.

Summary of in situ epitaxial nucleation and growth measurements. [for semiconducting single crystal PbSe films

NASA Technical Reports Server (NTRS)

Poppa, H.; Moorhead, R. D.; Heinemann, K.

1974-01-01

In situ nucleation and growth measurements of Ag and Au on single-crystal PbSe thin films were made using a transmission electron microscope. Properties studied were polymorphism, crystalline perfection, and the stoichiometric composition of the initial and the autoepitaxially thickened PbSe substrates. The quantitative nucleation and cluster growth measurements were limited to low-saturation conditions. The epitaxial orientations are discussed, and evidence is presented as to the stage of deposition at which the epitaxial order for Ag is introduced. Strong substrate/overgrowth interaction manifested itself by alloying and interdiffusion.

Chemical Bonding, Interdiffusion and Electronic Structure at InP, GaAs, and Si-Metal Interfaces.

DTIC Science & Technology

1985-10-01

4. H.H. Wieder, J. Vac. Sci. Technol. 15, 1498 (1978). C. 5. W.E. Spicer, 1. Lindau, P. Skeath, C.Y. Su, and P. Chye , Phys. Rev. Lett. 44, 10 420...Spicer, Solid State Electron. 28 307 (1985). 25. N. Newman, K.K. Chin , W.G. Petro, T. Kendelewicz, M.D. Williams, C.E. McCants, and W.E. Spicer, J. Vac...Technol. 19, 661 (1981). 11. Y. Shapira, L.J. Brillson and A. Heller, J. Vac. Sci. U Technol., Al, 766 (1983). 12. P.W. Chye , I. Lindau, P. Pianetta, C.M

Nanocrystalline cerium oxide materials for solid fuel cell systems

DOEpatents

Brinkman, Kyle S

2015-05-05

Disclosed are solid fuel cells, including solid oxide fuel cells and PEM fuel cells that include nanocrystalline cerium oxide materials as a component of the fuel cells. A solid oxide fuel cell can include nanocrystalline cerium oxide as a cathode component and microcrystalline cerium oxide as an electrolyte component, which can prevent mechanical failure and interdiffusion common in other fuel cells. A solid oxide fuel cell can also include nanocrystalline cerium oxide in the anode. A PEM fuel cell can include cerium oxide as a catalyst support in the cathode and optionally also in the anode.

Oxidized Ni/Au Transparent Electrode in Efficient CH3 NH3 PbI3 Perovskite/Fullerene Planar Heterojunction Hybrid Solar Cells.

PubMed

Lai, Wei-Chih; Lin, Kun-Wei; Wang, Yuan-Ting; Chiang, Tsung-Yu; Chen, Peter; Guo, Tzung-Fang

2016-05-01

The successful application of a Ni/Au transparent electrode for fabricating efficient perovskite-based solar cells is demonstrated. Through interdiffusion of the Ni/Au bilayer, Au forms an interconnected metallic network structure as the transparent electrode. Ni diffuses to the bilayer surface and oxidizes into NiOx becoming an appropriate electrode interlayer. These ITO- and PSS-free devices have potential applications in the design of future cost-effective, low-weight, and stable solar cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cu-Sn Intermetallic Compound Joints for High-Temperature Power Electronics Applications

NASA Astrophysics Data System (ADS)

Lee, Byung-Suk; Yoon, Jeong-Won

2018-01-01

Cu-Sn solid-liquid interdiffusion (SLID) bonded joints were fabricated using a Sn-Cu solder paste and Cu for high-temperature power electronics applications. The interfacial reaction behaviors and the mechanical properties of Cu6Sn5 and Cu3Sn SLID-bonded joints were compared. The intermetallic compounds formed at the interfaces in the Cu-Sn SLID-bonded joints significantly affected the die shear strength of the joint. In terms of thermal and mechanical properties, the Cu3Sn SLID-bonded joint was superior to the conventional solder and the Cu6Sn5 SLID-bonded joints.

Fire performance and decay resistance of solid wood and plywood treated with quaternary ammonia compounds and common fire retardants

Treesearch

Evren Terzi; S. Nami Kartal; Robert White; Katsumi Shinoda; Yuji Imamura

2010-01-01

In this study, the fire performance and decay resistance of solid wood and plywood treated with quaternary ammonia compounds (didecyl dimethyl ammonium chloride (DDAC) and didecyl dimethyl ammonium tetrafluoroborate (DBF)) were compared with the performance of untreated control specimens and specimens treated with common fire retardants ((monoammonium phosphate (MAP),...

Integrating Quaternary science research in land management, restoration, and conservation

Treesearch

C.I. Millar; W.B. Woolfenden

2001-01-01

Most of us have come to expect that the general public will ignore the primary message of Quaternary science that change happens. A flurry, however, of recent media attention to 20th-century global warming and its anomalies from climates of the last millennium has brought climate science at least momentarily into popular focus. Similarly, public land-managing agencies...

Evaluating the corrosiveness of southern pine treated with several wood preservatives using electrochemical techniques

Treesearch

Samuel L. Zelinka; Douglas R. Rammer; Donald S. Stone

2009-01-01

Chromated copper arsenate (CCA), the most widely used wood preservative of the past 50 years, has been replaced for most uses with alkaline-copper systems such as alkaline copper quaternary (ACQ), copper azole (CuAz) and micronized copper quaternary (MCQ). Preliminary research using high-temperature, high-humidity environments have shown that some of these wood...

Construction of quaternary stereocenters: asymmetric α-amination of branched aldehydes catalyzed by monoimide substituted cyclohexane-1,2-diamines.

PubMed

Fu, Ji-Ya; Wang, Qi-Lin; Peng, Lin; Gui, Yong-Yuan; Xu, Xiao-Ying; Wang, Li-Xin

2013-10-01

A highly efficient enantioselective α-amination of branched aldehydes catalyzed by chiral imide monosubstituted 1,2-diamine derivatives was reported to afford the quaternary stereogenic centers in excellent yields (up to 99%) and enantioselectivities (up to 97% ee). Chirality 25:668-672, 2013. © 2013 Wiley Periodicals, Inc. © 2013 Wiley Periodicals, Inc.

Geology and ground-water resources of the Lake Dakota Plain area, South Dakota

USGS Publications Warehouse

Hopkins, William B.; Petri, Lester R.

1963-01-01

Unconsolidated deposits of Quaternary age mantle the Cretaceous rocks. Although they consist mostly of material that is too fine grained to yield water freely to wells, the Quaternary deposits contain bodies of moderately to highly permeable material that yield water copiously. Such bodies may be located only by exploratory drilling or, possibly, geophysical methods. The water differs widely in amount of mineralization and in chemical composition; the specific conductance of water from 322 wells ranged from 246 to 13,300 micromhos per centimeter. In most of the report area the water is of unsuitable quality for irrigation and domestic use. The principal source of recharge to the Quaternary deposits is infiltrating precipitation. Evapotranspiration accounts for nearly all the water discharged; the amount of water discharging into stream channels and withdrawn from wells is almost negligible by comparison. Irrigation of the area would increase the rate of recharge to the Quaternary deposits and would cause the water table to rise. Probably it would also cause an increase in the concentration of dissolved minerals in much of the ground water. Artificial drainage would be necessary to prevent waterlogging of cropland.

Determination of quaternary ammonium compounds by potentiometric titration with an ionic surfactant electrode: single-laboratory validation.

PubMed

Price, Randi; Wan, Ping

2010-01-01

A potentiometric titration for determining the quaternary ammonium compounds (QAC) commonly found in antimicrobial products was validated by a single laboratory. Traditionally, QACs were determined by using a biphasic (chloroform and water) manual titration procedure. Because of safety considerations regarding chloroform, as well as the subjectivity of color indicator-based manual titration determinations, an automatic potentiometric titration procedure was tested with quaternary nitrogen product formulations. By using the Metrohm Titrando system coupled with an ionic surfactant electrode and an Ag/AgCl reference electrode, titrations were performed with various QAC-containing formulation products/matrixes; a standard sodium lauryl sulfate solution was used as the titrant. Results for the products tested are sufficiently reproducible and accurate for the purpose of regulatory product enforcement. The robustness of the method was measured by varying pH levels, as well as by comparing buffered versus unbuffered titration systems. A quantitation range of 1-1000 ppm quaternary nitrogen was established. Eight commercially available antimicrobial products covering a variety of matrixes were assayed; the results obtained were comparable to those obtained by the manual titration method. Recoveries of 94 to 104% were obtained for spiked samples.

Synthesis of inulin derivatives with quaternary phosphonium salts and their antifungal activity.

PubMed

Chen, Yuan; Tan, Wenqiang; Li, Qing; Dong, Fang; Gu, Guodong; Guo, Zhanyong

2018-07-01

Inulin is a kind of renewable and biodegradable carbohydrate with good water solubility and numerous physiological functions. For further utilization of inulin, chemical modification can be applied to improve its bioactivities. In this paper, five novel inulin derivatives were synthesized via chemical modification with quaternary phosphonium salt. Their antifungal activity against three kinds of plant pathogens including Colletotrichum lagenarium, Phomopsis asparagi, and Fusarium oxysporum was assessed with radial growth assay in vitro. Results revealed that all the inulin derivatives exhibited improved antifungal activity compared with inulin. Particularly, inulin modified with triphenylphosphine (TPhPAIL) exhibited the best antifungal activity with inhibitory indices of 80.0%, 78.8%, and 87.4% against Colletotrichum lagenarium, Phomopsis asparagi, and Fusarium oxysporum at 1.0mg/mL respectively. The results clearly showed that chemical modification of inulin with quaternary phosphonium salt could efficiently improve derivatives' antifungal activity. Further analysis of results indicated that the antifungal activity was influenced by alkyl chain length or electron-withdrawing ability of the grafted quaternary phosphonium salts. Longer alkyl chain lengths or the stronger electron-withdrawing groups would lead to enhanced antifungal efficacy. Copyright © 2018 Elsevier B.V. All rights reserved.

Nanosecond Absorption Spectroscopy of Hemoglobin: Elementary Processes in Kinetic Cooperativity

NASA Astrophysics Data System (ADS)

Hofrichter, James; Sommer, Joseph H.; Henry, Eric R.; Eaton, William A.

1983-04-01

A nanosecond absorption spectrometer has been used to measure the optical spectra of hemoglobin between 3 ns and 100 ms after photolysis of the CO complex. The data from a single experiment comprise a surface, defined by the time-ordered set of 50-100 spectra. Singular value decomposition is used to represent the observed spectra in terms of a minimal set of basis spectra and the time course of their amplitudes. Both CO rebinding and conformational changes are found to be multiphasic. Prior to the quaternary structural change, two relaxations are observed that are assigned to geminate recombination followed by a tertiary structural change. These relaxations are interpreted in terms of a kinetic model that points out their potential role in kinetic cooperativity. The rapid escape of CO from the heme pocket compared with the rate of rebinding observed for both R and T quaternary states shows that the quaternary structure controls the overall dissociation rate by changing the rate at which the Fe--CO bond is broken. A comparable description of the control of the overall association rates must await a more complete experimental description of the kinetics of the quaternary T state.

Structural effect of quaternary ammonium chitin derivatives on their bactericidal activity and specificity.

PubMed

Morkaew, Tirut; Pinyakong, Onruthai; Tachaboonyakiat, Wanpen

2017-08-01

The effect of the quaternary ammonium chitin structure on the bactericidal activity and specificity against Escherichia coli and Staphylococcus aureus was investigated. Quaternary ammonium chitins were synthesized by the separate acylation of chitin (CT) with carboxymethyl trimethylammonium chloride (CMA), 3-carboxypropyl trimethylammonium chloride (CPA) and N-dodecyl-N,N-(dimethylammonio)butyrate (DDMAB). The successful acylation was confirmed by newly formed ester linkage. All three derivatives had a higher surface charge than chitin due to the additional positively charged quaternary ammonium groups. The N-short alkyl substituent (methyl) of CTCMA and CTCPA increased the hydrophilicity whilst the N-long alkyl substituent (dodecyl) of CTDDMAB increased the hydrophobicity compared to chitin. Chitin did not exhibit any bactericidal activity, while CTCMA and CTCPA completely killed E. coli and S. aureus in 30 and 60min, respectively, and CTDDMAB completely killed S. aureus in 10min but did not kill E. coli after a 2-h exposure. Therefore, the N-short alkyl substituent was more effective for killing E. coli and the N-long alkyl substituent conferred specific bactericidal activity against S. aureus. Copyright © 2017 Elsevier B.V. All rights reserved.

Quaternary geologic map of the Blue Ridge 4 degrees x 6 degrees quadrangle, United States

USGS Publications Warehouse

Howard, Alan D.; Behling, Robert E.; Wheeler, Walter H.; Daniels, Raymond B.; Swadley, W.C.; Richmond, Gerald M.; Goldthwait, Richard P.; Fullerton, David S.; Sevon, William D.; Miller, Robert A.; Bush, Charles A.; Richmond, Gerald M.; Fullerton, David S.; Christiansen, Ann Coe

1991-01-01

This map is part of the Quaternary Geologic Atlas of the United States (I-1420). It was first published as a printed edition in 1986. The geologic data have now been captured digitally and are presented here along with images of the printed map sheet and component parts as PDF files. The Quaternary Geologic Map of the Blue Ridge 4° x 6° Quadrangle was mapped as part of the Quaternary Geologic Atlas of the United States. The atlas was begun as an effort to depict the areal distribution of surficial geologic deposits and other materials that accumulated or formed during the past 2+ million years, the period that includes all activities of the human species. These materials are at the surface of the earth. They make up the "ground" on which we walk, the "dirt" in which we dig foundations, and the "soil" in which we grow crops. Most of our human activity is related in one way or another to these surface materials that are referred to collectively by many geologists as that overlies the bedrock foundation of the continent. The maps were compiled at 1:1,000,000 scale.

Quaternary geologic map of the Hatteras 4° x 6° quadrangle, United States

USGS Publications Warehouse

State compilations by Johnson, Gerald H.; Richmond, Gerald Martin; edited and integrated by Richmond, G. M.; Fullerton, D.S.; Weide, D.L.; Bush, Charles A.

1986-01-01

This map is part of the Quaternary Geologic Atlas of the United States (I-1420). It was first published as a printed edition in 1986. The geologic data have now been captured digitally and are presented here along with images of the printed map sheet and component parts as PDF files. The Quaternary Geologic Map of the Hatteras 4° x 6° Quadrangle was mapped as part of the Quaternary Geologic Atlas of the United States. The atlas was begun as an effort to depict the areal distribution of surficial geologic deposits and other materials that accumulated or formed during the past 2+ million years, the period that includes all activities of the human species. These materials are at the surface of the Earth. They make up the "ground" on which we walk, the "dirt" in which we dig foundations, and the "soil" in which we grow crops. Most of our human activity is related in one way or another to these surface materials that are referred to collectively by many geologists as regolith, the mantle of fragmental and generally unconsolidated material that overlies the bedrock foundation of the continent. The maps were compiled at 1:1,000,000 scale.

Quaternary laser devices: history and state of the art

NASA Astrophysics Data System (ADS)

Eliseev, Petr G.

1993-05-01

Quaternary alloys of semiconductor compounds are suitable materials for wide-spectrum optoelectronic applications. The most important property of these efficient luminescent materials is the opportunity to fit the lattice parameter in some range to a given value corresponding to another crystalline material. This leads to the method to construct defect-free and stress-free heterojunctions, which was used for the preparation of a number of laser and LED devices. Quaternaries of InGaAsP, InGaSbAs, InSbAsP, PbSnTeSe, and other alloys were introduced into practical usage particularly in diode laser devices. The alloy InGaAsP appears to be one of the most widely used in optoelectronic applications at present as it covers ranges near 1.3 and 1.55 micrometers wavelengths of fiber-optic communication. For the spectral range near 2 micrometers the alloy InGaSbAs seems to be most attractive, and cw-operating diode lasers at room temperature were demonstrated at 2.0 - 2.4 micrometers . The alloy PbSnTeSe was used to obtain a longest wave of diode laser emission 46 micrometers . Quaternaries played an important role in the development of the semiconductor optoelectronics during the last two decades.

Surface-modified nanoparticles as anti-biofilm filler for dental polymers

PubMed Central

Zaltsman, Nathan; Ionescu, Andrei C.; Weiss, Ervin I.; Brambilla, Eugenio; Beyth, Shaul

2017-01-01

The objective of the study was to synthesis silica nanoparticles modified with (i) a tertiary amine bearing two t-cinnamaldehyde substituents or (ii) dimethyl-octyl ammonium, alongside the well-studied quaternary ammonium polyethyleneimine nanoparticles. These were to be evaluated for their chemical and mechanical properties, as well for antibacterial and antibiofilm activity. Samples were incorporated in commercial dental resin material and the degree of monomer conversion, mechanical strength, and water contact angle were tested to characterize the effect of the nanoparticles on resin material. Antibacterial activity was evaluated with the direct contact test and the biofilm inhibition test against Streptococcus mutans. Addition of cinnamaldehyde-modified particles preserved the degree of conversion and compressive strength of the base material and increased surface hydrophobicity. Quaternary ammonium functional groups led to a decrease in the degree of conversion and to low compressive strength, without altering the hydrophilic nature of the base material. In the direct contact test and the anti-biofilm test, the polyethyleneimine particles exhibited the strongest antibacterial effect. The cinnamaldehyde-modified particles displayed antibiofilm activity, silica particles with quaternary ammonium were ineffective. Immobilization of t-cinnamaldehyde onto a solid surface via amine linkers provided a better alternative to the well-known quaternary ammonium bactericides. PMID:29244848

Origin of bonebeds in Quaternary tank deposits

NASA Astrophysics Data System (ADS)

Araújo-Júnior, Hermínio Ismael de; Porpino, Kleberson de Oliveira; Bergqvist, Lílian Paglarelli

2017-07-01

Tank deposits are an exceptional type of fossiliferous deposit and bear a remarkably fossil record of the Pleistocene megafauna of South America, particularly of Brazil. The taphonomy of vertebrate remains preserved in this type of environmental context was clearly driven by climate, similarly to most of the Quaternary continental fossil record. The formation of the vertebrates fossil record in tank deposits was influenced by the climate seasonality typical of arid climate. The taphonomic history of most tank deposits is a consequence of this seasonality and, as a result, the paleoecological data preserved in their fossil assemblages is reliable with respect to paleobiological and paleoenvironmental settings of the Quaternary ecosystems of the Brazilian Intertropical Region (BIR). Other tank deposits experienced an unusual taphonomic history that, besides climate, was affected by recurrent events of reworking produced by the depositional agents dominant in the surrounding alluvial plains. The conclusions obtained here concerning the main taphonomic settings and formative processes that characterize fossil vertebrate assemblages of tank deposits will help further studies aimed to recover information on the paleoecology of Quaternary fauna collected in such deposits by allowing a better understanding of their time and spatial resolutions and other potential biases.

Water-quality characteristics of quaternary unconsolidated-deposit aquifers and lower tertiary aquifers of the Bighorn Basin, Wyoming and Montana, 1999-2001

USGS Publications Warehouse

Bartos, Timothy T.; Eddy-Miller, Cheryl A.; Norris, Jody R.; Gamper, Merry E.; Hallberg, Laura L.

2004-01-01

As part of the Yellowstone River Basin National Water Quality Assessment study, ground-water samples were collected from Quaternary unconsolidated-deposit and lower Tertiary aquifers in the Bighorn Basin of Wyoming and Montana from 1999 to 2001. Samples from 54 wells were analyzed for physical characteristics, major ions, trace elements, nutrients, dissolved organic carbon, radionuclides, pesticide compounds, and volatile organic compounds (VOCs) to evaluate current water-quality conditions in both aquifers. Water-quality samples indicated that waters generally were suitable for most uses, and that natural conditions, rather than the effects of human activities, were more likely to limit uses of the waters. Waters in both types of aquifers generally were highly mineralized, and total dissolved-solids concentrations frequently exceeded the U.S. Environmental Protection Agency (USEPA) Secondary Maximum Contaminant Level (SMCL) of 500 milligrams per liter (mg/L). Because of generally high mineralization, waters from nearly one-half of the samples from Quaternary aquifers and more than one-half of the samples from lower Tertiary aquifers were not classified as fresh (dissolved-solids concentration were not less than 1,000 mg/L). The anions sulfate, fluoride, and chloride were measured in some ground-water samples at concentrations greater than SMCLs. Most waters from the Quaternary aquifers were classified as very hard (hardness greater than 180 mg/L), but hardness varied much more in waters from the lower Tertiary aquifers and ranged from soft (less than 60 mg/L) to very hard (greater than 180 mg/L). Major-ion chemistry varied with dissolved-solids concentrations. In both types of aquifers, the predominant anion changes from bicarbonate to sulfate with increasing dissolved-solids concentrations. Samples from Quaternary aquifers with fresh waters generally were calcium-bicarbonate, calcium-sodium-bicarbonate, and calcium-sodium-sulfate-bicarbonate type waters, whereas samples with larger concentrations generally were calcium-sodium-sulfate, calcium-sulfate, or sodium-sulfate-type waters. In the lower Tertiary aquifers, samples with fresh waters generally were sodium-bicarbonate or sodium-bicarbonate-sulfate type waters, whereas samples with larger concentrations were sodium-sulfate or calcium-sodium-sulfate types. Concentrations of most trace elements in both types of aquifers generally were small and most were less than applicable USEPA standards. The trace elements that most often did not meet USEPA secondary drinking-water standards were iron and manganese. In fact, the SMCL for manganese was the most frequently exceeded standard; 68 percent of the samples from the Quaternary aquifers and 31 percent of the samples from the lower Tertiary aquifers exceeded the manganese standard. Geochemical conditions may control manganese in both aquifers as concentrations in Quaternary aquifers were negatively correlated with dissolved oxygen concentrations and concentrations in lower Tertiary aquifers decreased with increasing pH. Elevated nitrate concentrations, in addition to detection of pesticides and VOCs in both aquifers, indicated some effects of human activities on ground-water quality. Nitrate concentrations in 36 percent of the wells in Quaternary aquifers and 28 percent of the wells in lower Tertiary aquifers were greater than 1 mg/L, which may indicate ground-water contamination from human sources. The USEPA drinking-water Maximum Contaminant Level (MCL) for nitrate, 10 mg/L, was exceeded in 8 percent of samples collected from Quaternary aquifers and 3 percent from lower Tertiary aquifers. Nitrate concentrations in Quaternary aquifers were positively correlated with the percentage of cropland and other agricultural land (non-cropland), and negatively correlated with rangeland and riparian land. In the lower Tertiary aquifers, nitrate concentrations only were correlated with the percentage of cropland. Concentratio

New quantum codes constructed from quaternary BCH codes

NASA Astrophysics Data System (ADS)

Xu, Gen; Li, Ruihu; Guo, Luobin; Ma, Yuena

2016-10-01

In this paper, we firstly study construction of new quantum error-correcting codes (QECCs) from three classes of quaternary imprimitive BCH codes. As a result, the improved maximal designed distance of these narrow-sense imprimitive Hermitian dual-containing quaternary BCH codes are determined to be much larger than the result given according to Aly et al. (IEEE Trans Inf Theory 53:1183-1188, 2007) for each different code length. Thus, families of new QECCs are newly obtained, and the constructed QECCs have larger distance than those in the previous literature. Secondly, we apply a combinatorial construction to the imprimitive BCH codes with their corresponding primitive counterpart and construct many new linear quantum codes with good parameters, some of which have parameters exceeding the finite Gilbert-Varshamov bound for linear quantum codes.

Novel immobilization of a quaternary ammonium moiety on keratin fibers for medical applications.

PubMed

Yu, Dan; Cai, Jackie Y; Liu, Xin; Church, Jeffrey S; Wang, Lijing

2014-09-01

This paper introduces a new approach for immobilizing a quaternary ammonium moiety on a keratinous substrate for enhanced medical applications. The method involves the generation of thiols by controlled reduction of cystine disulfide bonds in the keratin, followed by reaction with [2-(acryloyloxy)ethyl]trimethylammonium chloride through thiol-ene click chemistry. The modified substrate was characterized with Raman and infrared spectroscopy, and assessed for its antibacterial efficacy and other performance changes. The results have demonstrated that the quaternary ammonium moiety has been effectively attached onto the keratin structure, and the resultant keratin substrate exhibits a multifunctional effect including antibacterial and antistatic properties, improved liquid moisture management property, improved dyeability and a non-leaching characteristic of the treated substrate. Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

Viscosities of nonelectrolyte liquid mixtures. II. Binary and quaternary systems of some n-alkanes

NASA Astrophysics Data System (ADS)

Wakefield, D. L.; Marsh, K. N.; Zwolinski, B. J.

1988-01-01

This paper is the second in a series of viscosity and density studies on multicomponent mixtures of n-alkanes from 303 to 338 K. Reported here are the results of binary mixtures of n-tetracosane + n-octane as well as quaternary mixtures of n-tetracosane + n-octane + n-decane + n-hexane at 318.16, 328.16, and 338.16 K. Viscosities were determined using a standard U-tube Ostwald viscometer, and densities were determined using a flask-type pycnometer. Empirical relations tested include the Grunberg and Nissan equation and the method of corresponding states. In addition, comparisons were made regarding the behavior of this quaternary system and homologous binary mixtures of n-hexadecane + n-octane and n-tetracosane + n-octane at the same temperatures.

Constraining fault activity by investigating tectonically-deformed Quaternary palaeoshorelines using a synchronous correlation method: the Capo D'Orlando Fault as a case study (NE Sicily, Italy)

NASA Astrophysics Data System (ADS)

Meschis, Marco; Roberts, Gerald P.; Robertson, Jennifer

2016-04-01

Long-term curstal extension rates, accommodated by active normal faults, can be constrained by investigating Late Quaternary vertical movements. Sequences of marine terraces tectonically deformed by active faults mark the interaction between tectonic activity, sea-level changes and active faulting throughout the Quaternary (e.g. Armijo et al., 1996, Giunta et al, 2011, Roberts et al., 2013). Crustal deformation can be calculated over multiple seismic cycles by mapping Quaternary tectonically-deformed palaeoshorelines, both in the hangingwall and footwall of active normal faults (Roberts et al., 2013). Here we use a synchronous correlation method between palaeoshorelines elevations and the ages of sea-level highstands (see Roberts et al., 2013 for further details) which takes advantage of the facts that (i) sea-level highstands are not evenly-spaced in time, yet must correlate with palaeoshorelines that are commonly not evenly-spaced in elevation, and (ii) that older terraces may be destroyed and/or overprinted by younger highstands, so that the next higher or lower paleoshoreline does not necessarily correlate with the next older or younger sea-level highstand. We investigated a flight of Late Quaternary marine terraces deformed by normal faulting as a result of the Capo D'Orlando Fault in NE Sicily (e.g. Giunta et al., 2011). This fault lies within the Calabrian Arc which has experienced damaging seismic events such as the 1908 Messina Straits earthquake ~ Mw 7. Our mapping and previous mapping (Giunta et al. (2011) demonstrate that the elevations of marine terraces inner edges change along the strike the NE - SW oriented normal fault. This confirms active deformation on the Capo D'Orlando Fault, strongly suggesting that it should be added into the Database of Individual Seismogenic Sources (DISS, Basili et al., 2008). Giunta et al. (2011) suggested that uplift rates and hence faults lip-rates vary through time for this examples. We update the ages assigned to each palaeoshoreline from the initial work by Giunta et al., (2011) using synchronous correlation. This alternative approach suggests that uplift rates were constant through the Late Quaternary, suggesting that the fault slip-rate governing seismic hazard has also been constant. Reference Armijo, R., Meyer, B. G. C. P., King, G. C. P., Rigo, A., & Papanastassiou, D. (1996). Quaternary evolution of the Corinth Rift and its implications for the Late Cenozoic evolution of the Aegean. Geophysical Journal International, 126(1): 11 - 53. Basili R., Valensise, G., Vannoli, P., Burrato, P., Fracassi, U., Mariano, S., Tiberti, M.M., Boschi. E. (2008). The Database of Individual Seismogenic Sources (DISS), version 3: summarizing 20 years of research on Italy's earthquake geology, Tectonophysics, doi:10.1016/j.tecto.2007.04.014. Giunta, G., Gueli, A.M., Monaco, C., Orioli, S., Ristuccia, G.M., Stella, G., Troja, S.O. (2011). Middle-Late Pleistocene marine terraces and fault activity in the Sant'Agata di Militello coastal area (north-eastern Sicily). Journal of Geodynamics. 55, 32 - 40. Roberts, G. P., Meschis, M., Houghton, S., Underwood, C., & Briant, R. M. (2013). The implications of revised Quaternary palaeoshoreline chronologies for the rates of active extension and uplift in the upper plate of subduction zones.Quaternary Science Reviews, 78: 169 - 187.

Materiais a base de oxidos com estrutura do tipo perovskite e compositos como anodos de PCES: Propriedades Funcionais e Comportamento Eletroquimico em Celulas com Eletrolitos Solidos a Base de Galatos e Silicatos

NASA Astrophysics Data System (ADS)

Kolotygin, Vladislav

This work was focused on the analysis of transport, thermomechanical and electrochemical properties of a series of perovskite-like oxide materials and composites for potential applications as anodes of intermediate-temperature solid oxide fuel cells (SOFCs) with lanthanum gallate and silicate solid electrolytes. The primary attention was centered on A(Mn,Nb)O3-delta (A = Sr, Ca) and (La,Sr)(Mn,Ti)O3-based systems, lanthanum chromite substituted with acceptor-type and variable-valence cations, and various Ni-containing cermets. Emphasis was given to phase stability of the materials, their crystal structure, microstructure of porous electrode layers and dense ceramics, electronic conductivity, Seebeck coefficient, oxygen permeability, thermal and chemical induced expansion, and anodic overpotentials of the electrodes deposited onto (La,Sr)(Ga,Mg)O3- and La10(Si,Al)6O27-based electrolyte membranes. In selected cases, roles of oxygen diffusivity, states of the transition metal cations relevant for the electronic transport, catalytically active additives and doped ceria protective interlayers introduced in the model electrochemical cells were assessed. The correlations between transport properties of the electrode materials and electrochemical behavior of porous electrodes showed that the principal factors governing anode performance include, in particular, electronic conduction of the anode compositions and cation interdiffusion between the electrodes and solid electrolytes. The latter is critically important for the silicatebased electrolyte membranes, leading to substantially worse anode properties compared to the electrochemical cells with lanthanum gallate solid electrolyte. The results made it possible to select several anode compositions exhibiting lower area-specific electrode resistivity compared to known analogues, such as (La,Sr)(Cr,Mn)O3-delta.

Digital release of the Alaska Quaternary fault and fold database

NASA Astrophysics Data System (ADS)

Koehler, R. D.; Farrell, R.; Burns, P.; Combellick, R. A.; Weakland, J. R.

2011-12-01

The Alaska Division of Geological & Geophysical Surveys (DGGS) has designed a Quaternary fault and fold database for Alaska in conformance with standards defined by the U.S. Geological Survey for the National Quaternary fault and fold database. Alaska is the most seismically active region of the United States, however little information exists on the location, style of deformation, and slip rates of Quaternary faults. Thus, to provide an accurate, user-friendly, reference-based fault inventory to the public, we are producing a digital GIS shapefile of Quaternary fault traces and compiling summary information on each fault. Here, we present relevant information pertaining to the digital GIS shape file and online access and availability of the Alaska database. This database will be useful for engineering geologic studies, geologic, geodetic, and seismic research, and policy planning. The data will also contribute to the fault source database being constructed by the Global Earthquake Model (GEM), Faulted Earth project, which is developing tools to better assess earthquake risk. We derived the initial list of Quaternary active structures from The Neotectonic Map of Alaska (Plafker et al., 1994) and supplemented it with more recent data where available. Due to the limited level of knowledge on Quaternary faults in Alaska, pre-Quaternary fault traces from the Plafker map are shown as a layer in our digital database so users may view a more accurate distribution of mapped faults and to suggest the possibility that some older traces may be active yet un-studied. The database will be updated as new information is developed. We selected each fault by reviewing the literature and georegistered the faults from 1:250,000-scale paper maps contained in 1970's vintage and earlier bedrock maps. However, paper map scales range from 1:20,000 to 1:500,000. Fault parameters in our GIS fault attribute tables include fault name, age, slip rate, slip sense, dip direction, fault line type (i.e., well constrained, moderately constrained, or inferred), and mapped scale. Each fault is assigned a three-integer CODE, based upon age, slip rate, and how well the fault is located. This CODE dictates the line-type for the GIS files. To host the database, we are developing an interactive web-map application with ArcGIS for Server and the ArcGIS API for JavaScript from Environmental Systems Research Institute, Inc. (Esri). The web-map application will present the database through a visible scale range with each fault displayed at the resolution of the original map. Application functionality includes: search by name or location, identification of fault by manual selection, and choice of base map. Base map options include topographic, satellite imagery, and digital elevation maps available from ArcGIS on-line. We anticipate that the database will be publically accessible from a portal embedded on the DGGS website by the end of 2011.

Preliminary maps of Quaternary deposits and liquefaction susceptibility, nine-county San Francisco Bay region, California: a digital database

USGS Publications Warehouse

Knudsen, Keith L.; Sowers, Janet M.; Witter, Robert C.; Wentworth, Carl M.; Helley, Edward J.; Nicholson, Robert S.; Wright, Heather M.; Brown, Katherine H.

2000-01-01

This report presents a preliminary map and database of Quaternary deposits and liquefaction susceptibility for the nine-county San Francisco Bay region, together with a digital compendium of ground effects associated with past earthquakes in the region. The report consists of (1) a spatial database of fivedata layers (Quaternary deposits, quadrangle index, and three ground effects layers) and two text layers (a labels and leaders layer for Quaternary deposits and for ground effects), (2) two small-scale colored maps (Quaternary deposits and liquefaction susceptibility), (3) a text describing the Quaternary map, liquefaction interpretation, and the ground effects compendium, and (4) the databse description pamphlet. The nine counties surrounding San Francisco Bay straddle the San Andreas fault system, which exposes the region to serious earthquake hazard (Working Group on California Earthquake Probabilities, 1999). Much of the land adjacent to the Bay and the major rivers and streams is underlain by unconsolidated deposits that are particularly vulnerable to earthquake shaking and liquefaction of water-saturated granular sediment. This new map provides a modern and regionally consistent treatment of Quaternary surficial deposits that builds on the pioneering mapping of Helley and Lajoie (Helley and others, 1979) and such intervening work as Atwater (1982), Helley and others (1994), and Helley and Graymer (1997a and b). Like these earlier studies, the current mapping uses geomorphic expression, pedogenic soils, and inferred depositional environments to define and distinguish the map units. In contrast to the twelve map units of Helley and Lajoie, however, this new map uses a complex stratigraphy of some forty units, which permits a more realistic portrayal of the Quaternary depositional system. The two colored maps provide a regional summary of the new mapping at a scale of 1:275,000, a scale that is sufficient to show the general distribution and relationships of the map units but cannot distinguish the more detailed elements that are present in the database. The report is the product of years of cooperative work by the USGS National Earthquake Hazards Reduction Program (NEHRP) and National Cooperative Geologic Mapping Program, William Lettis and & Associates, Inc. (WLA) and, more recently, by the California Division of Mines and Geology as well. An earlier version was submitted to the Geological Survey by WLA as a final report for a NEHRP grant (Knudsen and others, 2000). The mapping has been carried out by WLA geologists under contract to the NEHRP Earthquake Program (Grants #14-08-0001-G2129, 1434-94-G-2499, 1434-HQ-97-GR-03121, and 99-HQ-GR-0095) and with other limited support from the County of Napa, and recently also by the California Division of Mines and Geology. The current map consists of this new mapping and revisions of previous USGS mapping.

Elastic stress interaction between faulting and volcanism in the Olacapato-San Antonio de Los Cobres area (Puna plateau, Argentina)

NASA Astrophysics Data System (ADS)

Bonali, F. L.; Corazzato, C.; Tibaldi, A.

2012-06-01

We describe the relationships between Plio-Quaternary tectonics, palaeoseismicity and volcanism along the NW-trending Calama-Olacapato-El Toro (COT) lineament that crosses the Andean chain and the Puna Plateau and continues within the eastern Cordillera at about 24° S. We studied in detail the area from the Chile-Argentina border to a few km east of the San Antonio del Los Cobres village. Satellite and field data revealed the presence of seven Quaternary NW-striking normal left-lateral fault segments in the southeastern part of the studied area and of a Plio-Quaternary N-S-striking graben structure in the northwestern part. The NW-striking Chorrillos fault (CF) segment shows the youngest motions, of late Pleistocene age, being marked by several fault scarps, sag ponds and offset Quaternary deposits and landforms. Offset lavas of 0.78 ± 0.1 Ma to 0.2 ± 0.08 Ma indicate fault kinematics characterised by a pitch angle of 20° to 27° SE, a total net displacement of 31 to 63.8 m, and a slip-rate of 0.16 to 0.08 mm/yr. This fault segment is 32 km long and terminates to the northwest near a set of ESE-dipping thrust faults affecting Tertiary strata, while to the southeast it terminates 10 km further from San Antonio. In the westernmost part of the examined area, in Chile at altitudes > 4000 m, recent N-S-striking normal fault scarps depict the 5-km-wide and 10-km-long graben structure. Locally, fault pitches indicate left-lateral normal kinematics. These faults affect deposits up to ignimbrites of Plio-Quaternary age. Scarp heights are from a few metres to 24 m. Despite that this area is located along the trace of the COT strike-slip fault system, which is reported as a continuous structure from Chile to Argentina in the literature, no evidence of NW-striking Plio-Quaternary strike-slip structures is present here. A series of numerical models were also developed in an elastic half-space with uniform isotropic elastic properties using the Coulomb 3.1 code. We studied the stress changes caused by slip along the various Quaternary COT fault segments, showing that the last motions occurred along the CF might promote in the future further displacement along nearby fault segments located to the northwest. Furthermore, slip along the NW-striking fault segments imparts normal stress changes on the nearby Tuzgle volcano feeding system.

Discovery of novel quaternary ammonium derivatives of (3R)-quinuclidinyl amides as potent and long acting muscarinic antagonists.

PubMed

Prat, Maria; Buil, María Antonia; Fernández, Maria Dolors; Tort, Laia; Monleón, Juan Manuel; Casals, Gaspar; Ferrer, Manuel; Castro, Jordi; Gavaldà, Amadeu; Miralpeix, Montserrat; Ramos, Israel; Vilella, Dolors; Huerta, Josep Maria; Espinosa, Sònia; Hernández, Begoña; Segarra, Victor; Córdoba, Mònica

2015-04-15

Novel quaternary ammonium derivatives of (3R)-quinuclidinyl amides have been identified as potent M3 muscarinic antagonists with a long duration of action in an in vivo model of bronchoconstriction. The synthesis, structure-activity relationships and biological evaluation of this series of compounds are reported. Copyright © 2015 Elsevier Ltd. All rights reserved.

Rhodium-catalyzed asymmetric construction of quaternary carbon stereocenters: ligand-dependent regiocontrol in the 1,4-addition to substituted maleimides.

PubMed

Shintani, Ryo; Duan, Wei-Liang; Hayashi, Tamio

2006-05-03

A rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to substituted maleimides has been described. The regioselectivity in this reaction is controlled by the choice of ligand (dienes or bisphosphines), and 1,4-adducts with a quaternary stereocenter can be obtained with high regio- and enantioselectivity by the use of (R)-H8-binap.

Development of an expedient intramolecular Pauson-Khand reaction approach to stereoselectively construct the trans-decalin with a C1 quaternary chiral center.

PubMed

Shi, Li-Li; Shen, Hong-Juan; Fang, Li-Chao; Huang, Jun; Li, Chuang-Chuang; Yang, Zhen

2013-10-09

Stereoselective synthesis of the trans-decalin subunit with a defined C1 quaternary chiral center has been achieved by the Pauson-Khand reaction (PKR) as a key step. The developed chemistry offers an alternative to the IMDA reaction that has been used for the syntheses of trans-decalin based biologically active natural products.

Characteristics of newly found Quaternary fault, southern Korea, and its tectonic implication

NASA Astrophysics Data System (ADS)

Lee, Y.; Kim, M. C.; Cheon, Y.; Ha, S.; Kang, H. C.; Choi, J. H.; Son, M.

2017-12-01

This study introduces the detailed geometry and kinematics of recently found Quaternary fault in southern Korea, named Seooe Fault, and discusses its tectonic implication through a synthetic analysis with previous studies. The N-S striking Seooe Fault shows a top-to-the-east thrust geometry and cuts the Cretaceous Goseong Formation and overlying Quaternary deposits, and its slip senses and associated minor folds in the hanging wall indicate an E-W compressional stress. The age of the lower part of the Quaternary deposits obtained by OSL dating indicates that the last movement of the fault occurred after 61 60 ka. Arcuate geometry of the main fault showing an upward decreasing dip-angle, reverse offset of the fault breccias, and reverse-sense indicators observed on neighboring N-S striking high-angle fractures indicate that this Quaternary fault was produced by the reactivation of pre-existing fault under E-W compressional stress field. Using the apparent vertical displacement of the fault and the attitudes of cutting slope and main fault surface, its minimum net displacement is calculated as 2.17 m. When the value is applied to the empirical equation of maximum displacement - moment earthquake magnitude (Mw), the magnitude is estimated to reach about 6.7, assuming that this displacement was due to one seismic event. Most of the Quaternary faults in southern Korea are observed along major inherited fault zones, and their geometry and kinematics indicate that they were reactivated under ENE-WSW or E-W compressional stress field, which is concordant with the characteristics of the Seooe Fault. In addition, focal mechanism solutions and geotechnical in-situ stress data in and around the Korean peninsula also support the current ENE-WSW or E-W regional compression. On the basis of the regional stress trajectories in and around East Asia, the current stress field in Korean peninsula is interpreted to have resulted from the cooperation of westward shallow subduction of the Pacific Plate and collision of Indian and Eurasian continents, whereas the Philippine Sea plate doesn't contribute to the crustal contraction due to its high-angle subduction that results in the crustal extension of back-arc region.

Quaternary extensional and compressional tectonics revealed from Quaternary landforms along Kosi River valley, outer Kumaun Lesser Himalaya, Uttarakhand

NASA Astrophysics Data System (ADS)

Luirei, Khayingshing; Bhakuni, S. S.; Kothyari, Girish Ch.; Tripathi, Kavita; Pant, P. D.

2016-04-01

A portion of the Kosi River in the outer Kumaun Lesser Himalaya is characterized by wide river course situated south of the Ramgarh Thrust, where huge thickness (~200 m) of the landslide deposits and two to three levels of unpaired fan terraces are present. Brittle normal faults, suggesting extensional tectonics, are recognized in the Quaternary deposits and bedrocks as further supported by surface morphology. Trending E-W, these faults measure from 3 to 5 km in length and are traced as discontinuous linear mini-horst and fault scarps (sackungen) exposed due to cutting across by streams. Active normal faults have displaced the coarsely laminated debris fan deposits at two sites located 550 m apart. At one of the sites, the faults look like bookshelf faulting with the maximum displacement of ~2 m and rotation of the Quaternary boulders along the fault plane is observed. At another site, the maximum displacement measures about 0.60 cm. Thick mud units deposited due to blocking of the streams by landslides are observed within and above the fan deposit. Landslide debris fans and terrace landforms are widely developed; the highest level of fan is observed ~1240 m above mean sea level. At some places, the reworking of the debris fans by streams is characterized by thick laminated sand body. Along the South Almora Thrust and Ramgarh Thrust zones, the valleys are narrow and V-shaped where Quaternary deposits are sparse due to relatively rapid uplift across these thrusts. Along the South Almora Thrust zone, three to four levels of fluvial terraces are observed and have been incised by river exposing the bedrocks due to recent movement along the RT and SAT. Abandoned channel, tilted mud deposits, incised meandering, deep-cut V-shaped valleys and strath terraces indicate rapid uplift of the area. Thick mud sequences in the Quaternary columns indicate damming of streams. A ~10-km-long north-south trending transverse Garampani Fault has offset the Ramgarh Thrust producing tectonic landforms.

Late Quaternary changes in intermediate water oxygenation and oxygen minimum zone, northern Japan: A benthic foraminiferal perspective

NASA Astrophysics Data System (ADS)

Shibahara, Akihiko; Ohkushi, Ken'ichi; Kennett, James P.; Ikehara, Ken

2007-09-01

A strong oxygen minimum zone (OMZ) currently exists at upper intermediate water depths on the northern Japanese margin, NW Pacific. The OMZ results largely from a combination of high surface water productivity and poor ventilation of upper intermediate waters. We investigated late Quaternary history (last 34 kyr) of ocean floor oxygenation and the OMZ using quantitative changes in benthic foraminiferal assemblages in three sediment cores taken from the continental slope off Shimokita Peninsula and Tokachi, northern Japan, at water depths between 975 and 1363 m. These cores are well located within the present-day OMZ, a region of high surface water productivity, and in close proximity to the source region of North Pacific Intermediate Water. Late Quaternary benthic foraminiferal assemblages experienced major changes in response to changes in dissolved oxygen concentration in ocean floor sediments. Foraminiferal assemblages are interpreted to represent three main groups representing oxic, suboxic, and dysoxic conditions. Assemblage changes in all three cores and hence in bottom water oxygenation coincided with late Quaternary climatic episodes, similar to that known for the southern California margin. These episodes, in turn, are correlated with orbital and millennial climate episodes in the Greenland ice core including the last glacial episode, Bølling-Ållerød (B/A), Younger Dryas, Preboreal (earliest Holocene), early Holocene, and late Holocene. The lowest oxygen conditions, marked by dysoxic taxa and laminated sediments in one core, occurred during the B/A and the Preboreal intervals. Suboxic taxa dominated mainly during the last glacial, the Younger Dryas, and most of the Holocene. Dysoxic conditions during the B/A and Preboreal intervals in this region were possibly caused by high surface water productivity at times of reduced intermediate ventilation in the northwestern Pacific. Remarkable similarities are evident in the late Quaternary sequence of benthic foraminiferal assemblage change between the two very distant continental margins of northern Japan and southern California. The oscillations in OMZ strength, reflected by these faunal changes, were widespread and apparently synchronous over wide areas of the North Pacific, reflecting broad changes in intermediate water ventilation and surface ocean productivity closely linked with late Quaternary climate change on millennial and orbital timescales.

Quaternary tectonic faulting in the Eastern United States

USGS Publications Warehouse

Wheeler, R.L.

2006-01-01

Paleoseismological study of geologic features thought to result from Quaternary tectonic faulting can characterize the frequencies and sizes of large prehistoric and historical earthquakes, thereby improving the accuracy and precision of seismic-hazard assessments. Greater accuracy and precision can reduce the likelihood of both underprotection and unnecessary design and construction costs. Published studies proposed Quaternary tectonic faulting at 31 faults, folds, seismic zones, and fields of earthquake-induced liquefaction phenomena in the Appalachian Mountains and Coastal Plain. Of the 31 features, seven are of known origin. Four of the seven have nontectonic origins and the other three features are liquefaction fields caused by moderate to large historical and Holocene earthquakes in coastal South Carolina, including Charleston; the Central Virginia Seismic Zone; and the Newbury, Massachusetts, area. However, the causal faults of the three liquefaction fields remain unclear. Charleston has the highest hazard because of large Holocene earthquakes in that area, but the hazard is highly uncertain because the earthquakes are uncertainly located. Of the 31 features, the remaining 24 are of uncertain origin. They require additional work before they can be clearly attributed either to Quaternary tectonic faulting or to nontectonic causes. Of these 24, 14 features, most of them faults, have little or no published geologic evidence of Quaternary tectonic faulting that could indicate the likely occurrence of earthquakes larger than those observed historically. Three more features of the 24 were suggested to have had Quaternary tectonic faulting, but paleoseismological and other studies of them found no evidence of large prehistoric earthquakes. The final seven features of uncertain origin require further examination because all seven are in or near urban areas. They are the Moodus Seismic Zone (Hartford, Connecticut), Dobbs Ferry fault zone and Mosholu fault (New York City), Lancaster Seismic Zone and the epicenter of the shallow Cacoosing Valley earthquake (Lancaster and Reading, Pennsylvania), Kingston fault (central New Jersey between New York and Philadelphia), and Everona fault-Mountain Run fault zone (Washington, D.C., and Arlington and Alexandria, Virginia). ?? 2005 Elsevier B.V. All rights reserved.

Black phosphorus-assisted laser desorption ionization mass spectrometry for the determination of low-molecular-weight compounds in biofluids.

PubMed

He, Xiao-Mei; Ding, Jun; Yu, Lei; Hussain, Dilshad; Feng, Yu-Qi

2016-09-01

Quantitative analysis of small molecules by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been a challenging task due to matrix-derived interferences in low m/z region and poor reproducibility of MS signal response. In this study, we developed an approach by applying black phosphorus (BP) as a matrix-assisted laser desorption ionization (MALDI) matrix for the quantitative analysis of small molecules for the first time. Black phosphorus-assisted laser desorption/ionization mass spectrometry (BP/ALDI-MS) showed clear background and exhibited superior detection sensitivity toward quaternary ammonium compounds compared to carbon-based materials. By combining stable isotope labeling (SIL) strategy with BP/ALDI-MS (SIL-BP/ALDI-MS), a variety of analytes labeled with quaternary ammonium group were sensitively detected. Moreover, the isotope-labeled forms of analytes also served as internal standards, which broadened the analyte coverage of BP/ALDI-MS and improved the reproducibility of MS signals. Based on these advantages, a reliable method for quantitative analysis of aldehydes from complex biological samples (saliva, urine, and serum) was successfully established. Good linearities were obtained for five aldehydes in the range of 0.1-20.0 μM with correlation coefficients (R (2)) larger than 0.9928. The LODs were found to be 20 to 100 nM. Reproducibility of the method was obtained with intra-day and inter-day relative standard deviations (RSDs) less than 10.4 %, and the recoveries in saliva samples ranged from 91.4 to 117.1 %. Taken together, the proposed SIL-BP/ALDI-MS strategy has proved to be a reliable tool for quantitative analysis of aldehydes from complex samples. Graphical Abstract An approach for the determination of small molecules was developed by using black phosphorus (BP) as a matrix-assisted laser desorption ionization (MALDI) matrix.

An expanded ostracod-based conductivity transfer function for climate reconstruction in the Levant

NASA Astrophysics Data System (ADS)

Mischke, Steffen; Almogi-Labin, Ahuva; Al-Saqarat, Bety; Rosenfeld, Arik; Elyashiv, Hadar; Boomer, Ian; Stein, Mordechai; Lev, Lilach; Ito, Emi

2014-06-01

We present the first modern calibration dataset linking ostracod assemblage composition to water chemistry, and other site-specific variables, in the hydrologically and geopolitically sensitive southern Levant region. A total of 42 ostracod taxa were recorded from the 178 sampled sites in Israel and Jordan. Ilyocypris spp., Heterocypris salina and Cypridopsis vidua are the most abundant taxa. Species strictly confined to freshwater conditions are Prionocypris zenkeri, Gomphocythere ortali and Prionocypris olivaceus. In contrast, H. salina, Bradleytriebella lineata and Cyprideis torosa show high frequencies in brackish waters (waters with higher conductivity). Humphcypris subterranea, G. ortali, P. olivaceus and Cypridopsis elongata apparently prefer flowing waters. Specific conductivity optima and tolerance ranges were calculated for the recorded ostracod species and may be used for the palaeoenvironmental assessment of fossil ostracod assemblages. In addition, a transfer-function for quantitative specific conductivity estimation based on 141 samples was established with weighted averaging partial least squares regression (WA-PLS). The resulting coefficient of determination r2 between observed and predicted conductivity values (0.72) and the root-mean-square error of prediction (RMSEP) in % gradient length (13.1) indicate that conductivity may be reliably estimated from ostracod assemblage data. The transfer function was first applied to last glacial ostracod assemblage data from an archaeological trench in the Sea of Galilee (northern Israel). Relatively large conductivity fluctuations between ca 1 and 7 mS cm-1 were inferred for the period 24-20 cal ka BP. In addition, four episodes of freshwater influx near the site of the trench were identified from the presence of shells of freshwater and stream-dwelling species intermingled with very abundant shells of Cyprideis torosa. The results of our study allow a better use of Quaternary ostracods from the Levant as palaeoenvironmental indicators of water-body types and past conductivity levels and will contribute to a better understanding of Quaternary environmental and climate change in the Levant.

The pH-dependent rate of action of local anesthetics on the node of Ranvier

PubMed Central

1977-01-01

Local anesthetic solutions were applied suddenly to the outside of single myelinated nerve fibers to measure the time course of development of block of sodium channels. Sodium currents were measured under voltage clamp with test pulses applied several times per second during the solution change. The rate of block was studied by using drugs of different lipid solubility and of different charge type, and the external pH was varied from pH 8.3 to pH 6 to change the degree of ionization of the amine compounds. At pH 8.3 the half-time of action of amine anesthetics such as lidocaine, procaine, tetracaine, and others was always less than 2 s and usually less than 1 s. Lowering the pH to 6.0 decreased the apparent potency and slowed the rate of action of these drugs. The rate of action of neutral benzocaine was fast (1 s) and pH independent. The rate of action of cationic quaternary QX-572 was slow (greater than 200 s) and also pH independent. Other quaternary anesthetic derivatives showed no action when applied outside. The result is that neutral drug forms act much more rapidly than charged ones, suggesting that externally applied local anesthetics must cross a hydrophobic barrier to reach their receptor. A model representing diffusion of drug into the nerve fiber gives reasonable time courses of action and reasonable membrane permeability coefficients on the assumption that the hydrophobic barrier is the nodal membrane. Arguments are given that there may be a need for reinterpretation of many published experiments on the location of the anesthetic receptor and on which charge form of the drug is active to take into account the effects of unstirred layers, high membrane permeability, and high lipid solubility. PMID:16078

Study of Third-Order Optical Nonlinearities of Se-Sn (Bi,Te) Quaternary Chalcogenide Thin Films Using Ti: Sapphire Laser in Femtosecond Regime

NASA Astrophysics Data System (ADS)

Yadav, Preeti; Sharma, Ambika

2017-01-01

The objective of the present research work is to study the nonlinear optical properties of quaternary Se-Sn (Bi,Te) chalcogenide thin films. A Z-scan technique utilizing 800 nm femtosecond laser source has been used for the determination of the nonlinear refractive index ( n 2), two-photon absorption coefficient ( β 2) and third-order susceptibility ( χ (3)). In the measurement of n 2, an aperture is placed in the far field before the detector (closed aperture), while for the measurement of β 2, entire transmitted light is collected by the detector without an aperture (open aperture). Self-focusing has been observed in closed aperture transmission spectra. The appearance of the peak after the valley in this spectrum reflects the positive nonlinear refractive index. The calculated value of n 2 of the studied thin films varies from 1.06 × 10-12 cm2/W to 0.88 × 10-12 cm2/W. The compound-dependent behavior of n 2 is explained in this paper. We have also compared the experimental values of n 2 with the theoretically determined values, other compounds of chalcogenide glass and pure silica. The n 2 of the investigated thin films is found to be 3200 times higher than pure silica. The results of the open aperture Z-scan revealed that the value of β 2 of the studied compound is in the order of 10-8 cm/W. The behavior of two-photon absorption is described by means of the optical band gap ( E g) of the studied compound. The variation in the figure-of-merit from 0.32 to 1.4 with varying Sn content is also reported in this paper. The higher value of nonlinearity makes this material advantageous for optical fibers, waveguides and optical limiting devices.

Ion-pair partition of quarternary ammonium drugs: the influence of counter ions of different lipophilicity, size, and flexibility.

PubMed

Takács-Novák, K; Szász, G

1999-10-01

The ion-pair partition of quaternary ammonium (QA) pharmacons with organic counter ions of different lipophilicity, size, shape and flexibility was studied to elucidate relationships between ion-pair formation and chemical structure. The apparent partition coefficient (P') of 4 QAs was measured in octanol/pH 7.4 phosphate buffer system by the shake-flask method as a function of molar excess of ten counter ions (Y), namely: mesylate (MES), acetate (AC), pyruvate (PYRU), nicotinate (NIC), hydrogenfumarate (HFUM), hydrogenmaleate (HMAL), p-toluenesulfonate (PTS), caproate (CPR), deoxycholate (DOC) and prostaglandin E1 anion (PGE1). Based on 118 of highly precise logP' values (SD< 0.05), the intrinsic lipophilicity (without external counter ions) and the ion-pair partition of QAs (with different counter ions) were characterized. Linear correlation was found between the logP' of ion-pairs and the size of the counter ions described by the solvent accessible surface area (SASA). The lipophilicity increasing effect of the counter ions were quantified and the following order was established: DOC approximate to PGE1 > CPR approximate to PTS > NIC approximate to HMAL > PYRU approximate to AC approximate to MES approximate to HFUM. Analyzing the lipophilicity/molar ratio (QA:Y) profile, the differences in the ion-pair formation were shown and attributed to the differences in the flexibility/rigidity and size both of QA and Y. Since the largest (in average, 300 X) lipophilicity enhancement was found by the influence of DOC and PGE1 and considerable (on average 40 X) increase was observed by CPR and PTS, it was concluded that bile acids and prostaglandin anions may play a significant role in the ion-pair transport of quaternary ammonium drugs and caproic acid and p-toluenesulfonic acid may be useful salt forming agents to improve the pharmacokinetics of hydrophilic drugs.

Assessment of spatial distrilbution of porosity and aquifer geohydraulic parameters in parts of the Tertiary - Quaternary hydrogeoresource of south-eastern Nigeria

NASA Astrophysics Data System (ADS)

George, N. J.; Akpan, A. E.; Akpan, F. S.

2017-12-01

An integrated attempt exploring information deduced from extensive surface resistivity study in three Local Government Areas of Akwa Ibom State, Nigeria and data from hydrogeological sources obtained from water boreholes have been explored to economically estimate porosity and coefficient of permeability/hydraulic conductivity in parts of the clastic Tertiary - Quaternary sediments of the Niger Delta region. Generally, these parameters are predominantly estimated from empirical analysis of core samples and pumping test data generated from boreholes in the laboratory. However, this analysis is not only costly and time consuming, but also limited in areal coverage. The chosen technique employs surface resistivity data, core samples and pumping test data in order to estimate porosity and aquifer hydraulic parameters (transverse resistance, hydraulic conductivity and transmissivity). In correlating the two sets of results, Porosity and hydraulic conductivity were observed to be more elevated near the riverbanks. Empirical models utilising Archie's, Waxman-Smits and Kozeny-Carman Bear relations were employed characterising the formation parameters with wonderfully deduced good fits. The effect of surface conduction occasioned by clay usually disregarded or ignored in Archie's model was estimated to be 2.58 × 10-5 Siemens. This conductance can be used as a corrective factor to the conduction values obtained from Archie's equation. Interpretation aided measures such as graphs, mathematical models and maps which geared towards realistic conclusions and interrelationship between the porosity and other aquifer parameters were generated. The values of the hydraulic conductivity estimated from Waxman-Smits model was approximately 9.6 × 10-5m/s everywhere. This revelation indicates that there is no pronounced change in the quality of the saturating fluid and the geological formations that serve as aquifers even though the porosities were varying. The deciphered parameter relations can be used to estimate geohydraulic parameters in other locations with little or no borehole data.

First principles study on Fe based ferromagnetic quaternary Heusler alloys

NASA Astrophysics Data System (ADS)

Amudhavalli, A.; Rajeswarapalanichamy, R.; Iyakutti, K.

2017-11-01

The study of stable half-metallic ferromagnetic materials is important from various fundamental and application points of view in condensed matter Physics. Structural phase stability, electronic structure, mechanical and magnetic properties of Fe-based quaternary Heusler alloys XX‧YZ (X = Co, Ni; X‧ = Fe; Y = Ti; Z = Si, Ge, As) for three different phases namely α, β and γ phases of LiMgPdSn crystal structure have been studied by density functional theory with generalized gradient approximation formulated by Perdew, Burke and Ernzerhof (GGA-PBE) and the Hubbard formalism (GGA-PBE + U). This work aims to identify the ferromagnetic and half-metallic properties of XX‧YZ (X = Co, Ni, X‧ = Fe; Y = Ti; Z = Si, Ge, As) quaternary Heusler alloys. The predicted phase stability shows that α-phase is found to be the lowest energy phase at ambient pressure. A pressure-induced structural phase transition is observed in CoFeTiSi, CoFeTiGe, CoFeTiAs, NiFeTiSi, NiFeTiGe and NiFeTiAs at the pressures of 151.6 GPa, 33.7 GPa, 76.4 GPa, 85.3 GPa, 87.7 GPa and 96.5 GPa respectively. The electronic structure reveals that these materials are half metals at normal pressure whereas metals at high pressure. The investigation of electronic structure and magnetic properties are performed to reveal the underlying mechanism of half metallicity. The spin polarized calculations concede that these quaternary Heusler compounds may exhibit the potential candidate in spintronics application. The magnetic moments for these quaternary Heusler alloys in all the three different phases (α, β and γ) are estimated.

Late Quaternary glaciation of the Upper Soca River Region (Southern Julian Alps, NW Slovenia)

USGS Publications Warehouse

Bavec, Milos; Tulaczyk, Slawek M.; Mahan, Shannon; Stock, Gregory M.

2004-01-01

Extent of Late Quaternary glaciers in the Upper Soc??a River Region (Southern Julian Alps, SE Europe) has been analyzed using a combination of geological mapping, glaciological modeling, and sediment dating (radiocarbon, U/Th series and Infrared Stimulated Luminescence-IRSL). Field investigations focused mainly on relatively well preserved Quaternary sequences in the Bovec Basin, an intramontane basin located SW of the Mediterranean/Black Sea divide and surrounded by mountain peaks reaching from approximately 2100 up to 2587 m a.s.l. Within the Basin we recognized two Late Quaternary sedimentary assemblages, which consist of the same facies association of diamictons, laminated lacustrine deposits and sorted fluvial sediments. Radiocarbon dating of the upper part of the lake sediments sequence (between 12790??85 and 5885??60 14C years b.p.) indicates that the younger sedimentary assemblage was deposited during the last glacial maximum and through early Holocene (Marine Isotope Stage 21, MIS 2-1). Sediment ages obtained for the older assemblage with U/Th and IRSL techniques (between 154.74??22.88 and 129.93??7.90 ka b.p. for selected samples) have large errors but both methods yield results consistent with deposition during the penultimate glacial-interglacial transition (MIS 6-5). Based on analyses of field data combined with glaciological modeling, we argue that both sediment complexes formed due to high sediment productivity spurred by paraglacial conditions with glaciers present in the uplands around the Bovec Basin but not extending down to the basin floor. Our study shows that the extent and intensity of direct glacial sedimentation by Late Quaternary glaciers in the region was previously significantly overestimated. ?? 2004 Elsevier B.V. All rights reserved.

Effect of Quaternary Ammonium Carboxymethylchitosan on Release Rate In-vitro of Aspirin Sustained-release Matrix Tablets

PubMed Central

Meng, Lingbin; Teng, Zhongqiu; Zheng, Nannan; Meng, Weiwei; Dai, Rongji; Deng, Yulin

2013-01-01

The aim of this study was to develop a derivative of chitosan as pharmaceutical excipient used in sustained-release matrix tablets of poorly soluble drugs. A water-soluble quaternary ammonium carboxymethylchitosan was synthesized by a two-step reaction with carboxymethylchitosan (CMCTS), decylalkyl dimethyl ammonium and epichlorohydrin. The elemental analysis showed that the target product with 10.27% of the maximum grafting degree was obtained. To assess the preliminary safety of this biopolymer, cell toxicity assay was employed. In order to further investigate quaternary ammonium carboxymethylchitosan application as pharmaceutical excipient, aspirin was chosen as model drug. The effect of quaternary ammonium CMCTS on aspirin release rate from sustained-release matrix tablets was examined by in-vitro dissolution experiments. The results showed that this biopolymer had a great potential in increasing the dissolution of poorly soluble drug. With the addition of CMCTS-CEDA, the final cumulative release rate of drug rose up to 90%. After 12 h, at the grade of 10, 20 and 50 cps, the drug release rate increased from 58.1 to 90.7%, from 64.1 to 93.9%, from 69.3 to 96.1%, respectively. At the same time, aspirin release rate from sustainedrelease model was found to be related to the amount of quaternary ammonium CMCTS employed. With the increase of CMCTS-CEDA content, the accumulated release rate increased from 69.1% to 86.7%. The mechanism of aspirin release from sustained-release matrix tablets was also preliminary studied to be Fick diffusion. These data demonstrated that the chitosan derivative has positive effect on drug release from sustained-release matrix tablets. PMID:24250627

A closer look at the Neogene erosion and accumulation rate increase

NASA Astrophysics Data System (ADS)

Willenbring, J.; von Blanckenburg, F.

2008-12-01

Glacial erosion and Quaternary cold-stage warm-stage climate cycling have been cited as mechanisms to explain observations of increased Neogene marine sedimentation rates. Quantification of long-term glacial erosion rates from cosmogenic radionuclides from large areas mostly covered by cold-based ice during the Quaternary show very low erosion rates over several glacial cycles. In addition, isotope ratio proxies of dissolved metals in seawater, measured in chemical ocean sediments, lack clear evidence for an increase in terrigenous denudation. In particular, the stable isotope 9Be, derived from continental erosion, shows no change in its ratio to meteoric cosmogenic nuclide 10Be, derived from rain over the past 10 My. Radiogenic Pb and Nd isotopes, mainly show a change in the style of denudation from more chemical to more physical processes in the Quaternary. These data are at odds with a suggested increase in marine sedimentation rates during the late Cenozoic. In order to resolve this contradiction we have scrutinized these sedimentation rate calculations from ocean cores to identify whether they might show only apparent increases in the Neogene sections. Potential explanations are that in some cases, measured sediment thicknesses for different time intervals lack corrections for sediment compaction. Compaction of the lower portions of the cores drastically increases the apparent thickness of the more recent (Quaternary) sediment. In addition, sedimentation rates often only appear higher for recent sections in cores due to an artifact of an averaging timescale that decreases up-core. Such an averaging time scale decrease arises from better chronological resolution in recent times (Sadler et al., 1999). Cannibalization of older sediment might add to this effect. Together, these data question a clear, global-scale Quaternary climate-erosion connection that would be unique in Earth's history.

Electric field dynamics in nitride structures containing quaternary alloy (Al, In, Ga)N

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borysiuk, J., E-mail: jolanta.borysiuk@ifpan.edu.pl; Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw; Sakowski, K.

2016-07-07

Molecular beam epitaxy growth and basic physical properties of quaternary AlInGaN layers, sufficiently thick for construction of electron blocking layers (EBL), embedded in ternary InGaN layers are presented. Transmission electron microscopy (TEM) measurement revealed good crystallographic structure and compositional uniformity of the quaternary layers contained in other nitride layers, which are typical for construction of nitride based devices. The AlInGaN layer was epitaxially compatible to InGaN matrix, strained, and no strain related dislocation creation was observed. The strain penetrated for limited depth, below 3 nm, even for relatively high content of indium (7%). For lower indium content (0.6%), the strain wasmore » below the detection limit by TEM strain analysis. The structures containing quaternary AlInGaN layers were studied by time dependent photoluminescence (PL) at different temperatures and excitation powers. It was shown that PL spectra contain three peaks: high energy donor bound exciton peak from the bulk GaN (DX GaN) and the two peaks (A and B) from InGaN layers. No emission from quaternary AlInGaN layers was observed. An accumulation of electrons on the EBL interface in high-In sample and formation of 2D electron gas (2DEG) was detected. The dynamics of 2DEG was studied by time resolved luminescence revealing strong dependence of emission energy on the 2DEG concentration. Theoretical calculations as well as power-dependence and temperature-dependence analysis showed the importance of electric field inside the structure. At the interface, the field was screened by carriers and could be changed by illumination. From these measurements, the dynamics of electric field was described as the discharge of carriers accumulated on the EBL.« less

Structural Stability of Diffusion Barriers in Cu/Ru/MgO/Ta/Si

PubMed Central

Hsieh, Shu-Huei; Chen, Wen Jauh; Chien, Chu-Mo

2015-01-01

Various structures of Cu (50 nm)/Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm)/Si were prepared by sputtering and electroplating techniques, in which the ultra-thin trilayer of Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm) is used as the diffusion barrier against the interdiffusion between Cu film and Si substrate. The various structures of Cu/Ru/MgO/Ta/Si were characterized by four-point probes for their sheet resistances, by X-ray diffractometers for their crystal structures, by scanning electron microscopes for their surface morphologies, and by transmission electron microscopes for their cross-section and high resolution views. The results showed that the ultra-thin tri-layer of Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm) is an effective diffusion barrier against the interdiffusion between Cu film and Si substrate. The MgO, and Ta layers as deposited are amorphous. The mechanism for the failure of the diffusion barrier is that the Ru layer first became discontinuous at a high temperature and the Ta layer sequentially become discontinuous at a higher temperature, the Cu atoms then diffuse through the MgO layer and to the substrate at the discontinuities, and the Cu3Si phases finally form. The maximum temperature at which the structures of Cu (50 nm)/Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm)/Si are annealed and still have low sheet resistance is from 550 to 750 °C for the annealing time of 5 min and from 500 to 700 °C for the annealing time of 30 min. PMID:28347099

How thin barrier metal can be used to prevent Co diffusion in the modern integrated circuits?

NASA Astrophysics Data System (ADS)

Dixit, Hemant; Konar, Aniruddha; Pandey, Rajan; Ethirajan, Tamilmani

2017-11-01

In modern integrated circuits (ICs), billions of transistors are connected to each other via thin metal layers (e.g. copper, cobalt, etc) known as interconnects. At elevated process temperatures, inter-diffusion of atomic species can occur among these metal layers, causing sub-optimal performance of interconnects, which may lead to the failure of an IC. Thus, typically a thin barrier metal layer is used to prevent the inter-diffusion of atomic species within interconnects. For ICs with sub-10 nm transistors (10 nm technology node), the design rule (thickness scaling) demands the thinnest possible barrier layer. Therefore, here we investigate the critical thickness of a titanium-nitride (TiN) barrier that can prevent the cobalt diffusion using multi-scale modeling and simulations. First, we compute the Co diffusion barrier in crystalline and amorphous TiN with the nudged elastic band method within first-principles density functional theory simulations. Later, using the calculated activation energy barriers, we quantify the Co diffusion length in the TiN metal layer with the help of kinetic Monte Carlo simulations. Such a multi-scale modelling approach yields an exact critical thickness of the metal layer sufficient to prevent the Co diffusion in IC interconnects. We obtain a diffusion length of a maximum of 2 nm for a typical process of thermal annealing at 400 °C for 30 min. Our study thus provides useful physical insights for the Co diffusion in the TiN layer and further quantifies the critical thickness (~2 nm) to which the metal barrier layer can be thinned down for sub-10 nm ICs.

Materials properties of hafnium and zirconium silicates: Metal interdiffusion and dopant penetration studies

NASA Astrophysics Data System (ADS)

Quevedo Lopez, Manuel Angel

Hafnium and Zirconium based gate dielectrics are considered potential candidates to replace SiO2 or SiON as the gate dielectric in CMOS processing. Furthermore, the addition of nitrogen into this pseudo-binary alloy has been shown to improve their thermal stability, electrical properties, and reduce dopant penetration. Because CMOS processing requires high temperature anneals (up to 1050°C), it is important to understand the diffusion properties of any metal associated with the gate dielectric in silicon at these temperatures. In addition, dopant penetration from the doped polysilicon gate into the Si channel at these temperatures must also be studied. Impurity outdiffusion (Hf, Zr) from the dielectric, or dopant (B, As, P) penetration through the dielectric into the channel region would likely result in deleterious effects upon the carrier mobility. In this dissertation extensive thermal stability studies of alternate gate dielectric candidates ZrSixOy and HfSixO y are presented. Dopant penetration studies from doped-polysilicon through HfSixOy and HfSixOyNz are also presented. Rutherford Backscattering Spectroscopy (RBS), Heavy Ion RBS (HI-RBS), X-ray Photoelectron Spectroscopy (XPS), High Resolution Transmission Electron Microscopy (HR-TEM), and Time of Flight and Dynamic Secondary Ion Mass Spectroscopy (ToF-SIMS, D-SIMS) methods were used to characterize these materials. The dopant diffusivity is calculated by modeling of the dopant profiles in the Si substrate. In this disseration is reported that Hf silicate films are more stable than Zr silicate films, from the metal interdiffusion point of view. On the other hand, dopant (B, As, and P) penetration is observed for HfSixO y films. However, the addition of nitrogen to the Hf - Si - O systems improves the dopant penetration properties of the resulting HfSi xOyNz films.

Restricted-Access Al-Mediated Material Transport in Al Contacting of PureGaB Ge-on-Si p + n Diodes

NASA Astrophysics Data System (ADS)

Sammak, Amir; Qi, Lin; Nanver, Lis K.

2015-12-01

The effectiveness of using nanometer-thin boron (PureB) layers as interdiffusion barrier to aluminum (Al) is studied for a contacting scheme specifically developed for fabricating germanium-on-silicon (Ge-on-Si) p + n photodiodes with an oxide-covered light entrance window. Contacting is achieved at the perimeter of the Ge-island anode directly to an Al interconnect metallization. The Ge is grown in oxide windows to the Si wafer and covered by a B and gallium (Ga) layer stack (PureGaB) composed of about a nanometer of Ga for forming the p + Ge region and 10 nm of B as an interdiffusion barrier to the Al. To form contact windows, the side-wall oxide is etched away, exposing a small tip of the Ge perimeter to Al that from this point travels about 5 μm into the bulk Ge crystal. In this process, Ge and Si materials are displaced, forming Ge-filled V-grooves at the Si surface. The Al coalesces in grains. This process is studied here by high-resolution cross-sectional transmission electron microscopy and energy dispersive x-ray spectroscopy that confirm the purities of the Ge and Al grains. Diodes are fabricated with different geometries and statistical current-voltage characterization reveals a spread that can be related to across-the-wafer variations in the contact processing. The I- V behavior is characterized by low dark current, low contact resistance, and breakdown voltages that are suitable for operation in avalanching modes. The restricted access to the Ge of the Al inducing the Ge and Si material transport does not destroy the very good electrical characteristics typical of PureGaB Ge-on-Si diodes.