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Sample records for reduced intergranular exchange

  1. Magnetic patterning: local manipulation of the intergranular exchange coupling via grain boundary engineering

    PubMed Central

    Huang, Kuo-Feng; Liao, Jung-Wei; Hsieh, Cheng-Yu; Wang, Liang-Wei; Huang, Yen-Chun; Wen, Wei-Chih; Chang, Mu-Tung; Lo, Shen-Chuan; Yuan, Jun; Lin, Hsiu-Hau; Lai, Chih-Huang

    2015-01-01

    Magnetic patterning, with designed spatial profile of the desired magnetic properties, has been a rising challenge for developing magnetic devices at nanoscale. Most existing methods rely on locally modifying magnetic anisotropy energy or saturation magnetization, and thus post stringent constraints on the adaptability in diverse applications. We propose an alternative route for magnetic patterning: by manipulating the local intergranular exchange coupling to tune lateral magnetic properties. As demonstration, the grain boundary structure of Co/Pt multilayers is engineered by thermal treatment, where the stress state of the multilayers and thus the intergranular exchange coupling can be modified. With Ag passivation layers on top of the Co/Pt multilayers, we can hinder the stress relaxation and grain boundary modification. Combining the pre-patterned Ag passivation layer with thermal treatment, we can design spatial variations of the magnetic properties by tuning the intergranular exchange coupling, which diversifies the magnetic patterning process and extends its feasibility for varieties of new devices. PMID:26156786

  2. Effects of temperature on intergranular exchange coupling in L10 FePt thin films

    NASA Astrophysics Data System (ADS)

    Huang, Efrem Y.; Kryder, Mark H.

    2014-06-01

    The effects of temperature on intergranular exchange coupling for FePt:X:FePt (X = TaOx, SiOx, Cr) sputtered thin film stacks were investigated. In-plane FePt layers separated by a thin layer of segregant were used as an experimental model for the intergranular region in perpendicular recording media. Magnetic hysteresis was measured for varying segregant thicknesses (0.5 nm-1.5 nm) at varying temperatures (300 K-700 K). Exchange coupling energies were calculated using the reversal field, saturation magnetization, and coercivity. The intergranular exchange coupling energy was observed to be well-behaved, decreasing linearly with increasing temperature to 600 K. TaOx resulted in the lowest exchange coupling energy at any given temperature, while SiOx and Cr showed similar decoupling capabilities. At 600 K and beyond, antiferromagnetic behavior was observed. Exchange coupling was found to be negligible at operating temperatures above 600 K even with as little as 0.5 nm of TaOx segregant or 1 nm of SiOx segregant.

  3. Influence of intergranular exchange coupling on the magnetization dynamics of CoCrPt:SiO{sub 2} granular media

    SciTech Connect

    Brandt, R.; Schmidt, H.; Tibus, S.; Springer, F.; Fassbender, J.; Rohrmann, H.; Albrecht, M.

    2012-08-01

    We investigate the effect of Co{sup +} irradiation on the magnetization dynamics of CoCrPt:SiO{sub 2} granular media. Increasing irradiation levels reduce the saturation magnetization and effective anisotropy, which decrease the intrinsic magnetization precession frequency. Furthermore, increasing intergranular exchange coupling results in a qualitative change in the behavior of the magnetic material from a collection of individual grains to a homogeneous thin film, as evidenced in both the switching behavior and dynamics. The frequency change cannot be explained by single crystal macrospin modeling, and can only be reproduced by the inclusion of the dipolar effects and anisotropy distribution inherent in a granular medium.

  4. Influence of intergranular exchange coupling on the magnetization dynamics of CoCrPt:SiO2 granular media

    NASA Astrophysics Data System (ADS)

    Brandt, R.; Tibus, S.; Springer, F.; Fassbender, J.; Rohrmann, H.; Albrecht, M.; Schmidt, H.

    2012-08-01

    We investigate the effect of Co+ irradiation on the magnetization dynamics of CoCrPt:SiO2 granular media. Increasing irradiation levels reduce the saturation magnetization and effective anisotropy, which decrease the intrinsic magnetization precession frequency. Furthermore, increasing intergranular exchange coupling results in a qualitative change in the behavior of the magnetic material from a collection of individual grains to a homogeneous thin film, as evidenced in both the switching behavior and dynamics. The frequency change cannot be explained by single crystal macrospin modeling, and can only be reproduced by the inclusion of the dipolar effects and anisotropy distribution inherent in a granular medium.

  5. Grain-boundary engineering markedly reduces susceptibility to intergranular hydrogen embrittlement in metallic materials

    SciTech Connect

    Bechtle, Sabine; Kumar, Mukul; Somerday, Brian P.; Launey, Maximilien E.; Ritchie, Robert O.

    2009-05-10

    The feasibility of using 'grain-boundary engineering' techniques to reduce the susceptibility of a metallic material to intergranular embrittlement in the presence of hydrogen is examined. Using thermomechanical processing, the fraction of 'special' grain boundaries was increased from 46% to 75% (by length) in commercially pure nickel samples. In the presence of hydrogen concentrations between 1200 and 3400 appm, the high special fraction microstructure showed almost double the tensile ductility; also, the proportion of intergranular fracture was significantly lower and the J{sub c} fracture toughness values were some 20-30% higher in comparison with the low special fraction microstructure. We attribute the reduction in the severity of hydrogen-induced intergranular embrittlement to the higher fraction of special grain boundaries, where the degree of hydrogen segregation at these boundaries is reduced.

  6. Investigation on intergranular exchange coupling effect in Pr9Fe85.5B5.5 ribbons

    NASA Astrophysics Data System (ADS)

    Li, Z. B.; Zhang, M.; Wang, L. C.; Shen, B. G.; Zhang, X. F.; Li, Y. F.; Hu, F. X.; Sun, J. R.

    2014-02-01

    The intergranular exchange coupling effects are investigated via thermal activation of magnetization reversal in the magnetic relaxation process, combined with Henkel plots and the measurement of susceptibilities in three types of Pr9Fe85.5B5.5 ribbons. Exchange interaction between hard-hard grains is proposed in optimal melt-spun ribbons, as well as in over melt-spun ribbons even bearing a weak exchange coupling between soft-hard grains. In under melt-spun ribbons, the decoupled effect is proposed between hard-hard grains. These investigations may contribute to a clear understanding about the complicated nature of the intergranular exchange coupling in nanocomposite magnets.

  7. Experimental modeling of intergranular exchange coupling for perpendicular thin film media

    NASA Astrophysics Data System (ADS)

    Sokalski, Vincent; Laughlin, David E.; Zhu, Jian-Gang

    2009-09-01

    We present an experimental model system that enables quantitative assessment of intergranular exchange coupling in CoCrPt-oxide perpendicular magnetic recording media. A thin film structure consisting of a high coercivity CoPt unicrystal layer and a lower coercivity CoPt layer separated by a thin oxide interlayer is used to model perpendicularly magnetized grains separated by oxide grain boundaries. Exchange coupling energy between the CoPt layers was obtained for SiOx, TiOx, and CrOx interlayers by measuring field shifts from the lower coercivity layer. Cr segregation in CoCrPt grains to grain boundaries is also modeled experimentally and found to significantly suppress exchange coupling.

  8. Micromagnetic simulation of ferromagnetic resonance of perpendicular granular media: Influence of the intergranular exchange on the Landau-Lifshitz-Gilbert damping constant

    NASA Astrophysics Data System (ADS)

    Krone, P.; Albrecht, M.; Schrefl, T.

    2011-03-01

    A micromagnetic approach was used to simulate ferromagnetic resonance frequency (FMR) profiles of perpendicular granular CoCrPt-oxide thin films. From the obtained FMR line-width we computed the effective damping constant. The influence of the intergranular exchange on the effective damping was investigated, showing an increase in the damping constant with increase in intergranular exchange coupling. Moreover, the effective damping constant increases with decrease in mesh size of the model, and eventually saturates for mesh sizes of about 1 nm. These dependencies are explained in terms of different modes that can be excited in the granular medium due to interactions between the individual spins.

  9. Synthesis of L1{sub 0}-FePt perpendicular films with controllable coercivity and intergranular exchange coupling by interfacial microstructure control

    SciTech Connect

    Feng Chun; Zhang En; Yang Meiyin; Li Ning; Jiang Yong; Yu Guanghua; Li Baohe

    2010-06-15

    A series of FePtBi/Au multilayers were fabricated by magnetron sputtering. The interfacial microstructure control of Bi and Au atoms and its effect on comprehensive properties of L1{sub 0}-FePt perpendicular films were carefully studied. Results show that: perpendicular magnetic anisotropy of the L1{sub 0}-FePt film can be remarkably enhanced with the epitaxial inducement of Au atoms. On the other hand, intergranular exchange coupling (IEC) of the film is greatly decreased due to the isolation of FePt particles by nonmagnetic Au particles. Moreover, the controllable coercivity of the film can be realized by adjusting ordering degree of the film through diffusion of Bi atoms. Thus, an L1{sub 0}-FePt perpendicular film with controllable coercivity and no IEC is realized with the interfacial microstructure control of surfactant Bi and Au atoms.

  10. Evaluation of intergranular exchange coupling and magnetic domain size in CoCrPt-SiOX thin films with perpendicular anisotropy

    NASA Astrophysics Data System (ADS)

    Papusoi, C.; Desai, M.; Acharya, R.

    2015-06-01

    A method to evaluate the intergranular exchange coupling constant JEX in thin films with perpendicular anisotropy, based on first order reversal curve (FORC) diagrams, is proposed. For a 7.5 nm thick CoCrPt-SiOx magnetic (MAG) layer, JEX can be decreased from 1.1 to 0.26 erg cm-2 by using an adjacent CoCr-TiOx layer (isolation enhancement layer or IEL), enabling its application for high-density magnetic recording. The minimum value of JEX is attained for an IEL thickness of ~1.5 nm, which is low enough to preserve the HCP crystallographic structure of the MAG layer, with the c-axis perpendicular to film plane. The extracted values of JEX are used to evaluate the magnetic domain size of MAG layer using the checkerboard and the stripe domain models. Magnetic force microscopy observations indicate that domain size approaches the value predicted by the checkerboard model when JEX ≈ 0.8 erg cm-2, while for JEX > 0.8 erg cm-2 the actual domain size lies between the values indicated by the two models.

  11. Study of intergranular exchange coupling in longitudinal CoCrPt and perpendicular CoNi/Pt thin films for magnetic recording

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Lee, Hwan-Soo; Peng, Jie-Gang; Zhong, Zhi-Yong; Zu, Xiao-Tao

    2008-10-01

    We investigated magnetic intergranular coupling in both longitudinal and perpendicular media, suitable for high-density recording. The longitudinal media were two kinds of CoCrPt thin films with one strongly and the other weakly coupled. The perpendicular media were two kinds of CoNi/Pt multilayered thin films with one strongly and the other weakly coupled. The dc saturated and demagnetized magnetic states of thin films were studied by magnetic force microscopy. The demagnetized state of strongly coupled media shows greater contrast than that of granular ones for both CoNi/Pt and CoCrPt. In the dc saturated states, CoNi/Pt shows uniform distribution of the magnetization, while CoCrPt shows distinct remanent magnetization, which is smaller than saturation magnetization. A recording demonstration shows that the perpendicular medium is advantageous over the longitudinal one, and the weakly coupled medium outweighs the strongly coupled one for high-density recording.

  12. The role of intergranular chromium carbides on intergranular oxidation of nickel based alloys in pressurized water reactors primary water

    NASA Astrophysics Data System (ADS)

    Gaslain, F. O. M.; Le, H. T.; Duhamel, C.; Guerre, C.; Laghoutaris, P.

    2016-02-01

    Alloy 600 is used in pressurized water reactors (PWRs) but is susceptible to primary water stress corrosion cracking (PWSCC). Intergranular chromium carbides have been found beneficial to reduce PWSCC. Focussed ion beam coupled with scanning electron microscopy (FIB/SEM) 3D tomography has been used to reconstruct the morphology of grain boundary oxide penetrations and their interaction with intergranular Cr carbides in Alloy 600 subjected to a PWR environment. In presence of intergranular Cr carbides, the intergranular oxide penetrations are less deep but larger than without carbide. However, the intergranular oxide volumes normalized by the grain boundary length for both samples are similar, which suggest that intergranular oxidation growth rate is not affected by carbides. Analytical transmission electron microscopy (TEM) shows that the intergranular oxide consists mainly in a spinel-type oxide containing nickel and chromium, except in the vicinity of Cr carbides where Cr2O3 was evidenced. The formation of chromium oxide may explain the lower intergranular oxide depth observed in grain boundaries containing Cr carbides.

  13. Air Circulation and Heat Exchange Under Reduced Pressures

    NASA Technical Reports Server (NTRS)

    Rygalov, V.; Wheeler, R.; Dixon, M.; Fowler, P.; Hillhouse, L.

    2010-01-01

    Heat exchange rates decrease non-linearly with reductions in atmospheric pressure. This decrease creates risk of thermal stress (elevated leaf temperatures) for plants under reduced pressures. Forced convection (fans) significantly increases heat exchange rate under almost all pressures except below 10 kPa. Plant cultivation techniques under reduced pressures will require forced convection. The cooling curve technique is a reliable means of assessing the influence of environmental variables like pressure and gravity on gas exchange of plant. These results represent the extremes of gas exchange conditions for simple systems under variable pressures. In reality, dense plant canopies will exhibit responses in between these extremes. More research is needed to understand the dependence of forced convection on atmospheric pressure. The overall thermal balance model should include latent and radiative exchange components.

  14. Air Circulation and Heat Exchange under Reduced Pressures

    NASA Astrophysics Data System (ADS)

    Rygalov, Vadim; Wheeler, Raymond; Dixon, Mike; Hillhouse, Len; Fowler, Philip

    Low pressure atmospheres were suggested for Space Greenhouses (SG) design to minimize sys-tem construction and re-supply materials, as well as system manufacturing and deployment costs. But rarified atmospheres modify heat exchange mechanisms what finally leads to alter-ations in thermal control for low pressure closed environments. Under low atmospheric pressures (e.g., lower than 25 kPa compare to 101.3 kPa for normal Earth atmosphere), convection is becoming replaced by diffusion and rate of heat exchange reduces significantly. During a period from 2001 to 2009, a series of hypobaric experiments were conducted at Space Life Sciences Lab (SLSLab) NASA's Kennedy Space Center and the Department of Space Studies, University of North Dakota. Findings from these experiments showed: -air circulation rate decreases non-linearly with lowering of total atmospheric pressure; -heat exchange slows down with pressure decrease creating risk of thermal stress (elevated leaf tem-peratures) for plants in closed environments; -low pressure-induced thermal stress could be reduced by either lowering system temperature set point or increasing forced convection rates (circulation fan power) within certain limits; Air circulation is an important constituent of controlled environments and plays crucial role in material and heat exchange. Theoretical schematics and mathematical models are developed from a series of observations. These models can be used to establish optimal control algorithms for low pressure environments, such as a space greenhouse, as well as assist in fundamental design concept developments for these or similar habitable structures.

  15. Sludge, fuel degradation and reducing fouling on heat exchangers

    SciTech Connect

    Butcher, T.; Litzke, Wai Lin; Krajewski, R.; Celebi, Y.

    1992-02-01

    Brookhaven National Laboratory, under contract to the US Department of Energy, operates an oil heat research primarily to lower energy consumption in the 12 million oil heated homes in the US. The program objectives include: Improve steady state efficiency of oil heating equipment, Improve seasonal efficiencies, Eliminate or minimize factors which tend to degrade system performance. This paper provides an overview of the status of three specific projects which fall under the above objectives. This includes our fuel quality project, oil appliance venting and a project addressing efficiency degradation due to soot fouling of heat exchangers.

  16. Measuring the exchange of volatile reduced nitrogen compounds over grassland

    NASA Astrophysics Data System (ADS)

    Sintermann, J.; Kuhn, U.; Ammann, C.; Neftel, A.; Spirig, C.

    2009-04-01

    An important part of nitrogen transfer between the atmosphere and the biosphere occurs through the exchange of reactive nitrogen compounds. Among them are alkaline gases like ammonia and amines. Atmospheric ammonia deposition represents an important fraction of nitrogen input for terrestrial ecosystems and ammonia plays an important role in aerosol formation. Despite this environmental relevance, many uncertainties on the sources and the behaviour of atmospheric ammonia persist, partly because of the challenging nature of ammonia measurements. In principle, eddy covariance (EC) methods are best suited to determine biosphere-atmosphere fluxes because of their direct nature and negligible influence on the ecosystem by instrumental installations. However, the applicability of EC is restricted to compounds for which fast and sensitive sensors are available. For measurements of ammonia, not only the principal capabilities of the sensors are critical, but also the properties of the air sampling system, because ammonia sticks to almost any kind of surfaces. We explored the possibilities of ammonia and amine measurements using a PTR-MS instrument. Although this instrument has a nominal response time well sufficient for EC measurements, its effective response time for ammonia and selected amines was only in the order of minutes apparently due to absorption effects. A PTR-MS instrument was installed at the NitroEurope grassland site Oensingen for measuring ammonia and amines following the application of liquid cattle slurry. Air was sampled alternately from 0.5 and 1.5 m above ground through two identical tubes continuously flushed at high flow rates. In parallel, a gradient measurement system based on ammonia absorption into acidic solution and subsequent analysis in the liquid phase was operated. The liquid sampling system proved to be suited for the determination of fluxes with the aerodynamic gradient method both for high ammonia emissions after slurry application and

  17. ON THE ORIGIN OF INTERGRANULAR JETS

    SciTech Connect

    Yurchyshyn, V. B.; Goode, P. R.; Abramenko, V. I.; Steiner, O.

    2011-08-01

    We observe that intergranular jets, originating in the intergranular space surrounding individual granules, tend to be associated with granular fragmentation, in particular, with the formation and evolution of a bright granular lane (BGL) within individual granules. The BGLs have recently been identified as vortex tubes by Steiner et al. We further discover the development of a well-defined bright grain located between the BGL and the dark intergranular lane to which it is connected. Signatures of a BGL may reach the lower chromosphere and can be detected in off-band H{alpha} images. Simulations also indicate that vortex tubes are frequently associated with small-scale magnetic fields. We speculate that the intergranular jets detected in the New Solar Telescope (NST) data may result from the interaction between the turbulent small-scale fields associated with the vortex tube and the larger-scale fields existing in the intergranular lanes. The intergranular jets are much smaller and weaker than all previously known jet-like events. At the same time, they appear much more numerous than the larger events, leading us to the speculation that the total energy release and mass transport by these tiny events may not be negligible in the energy and mass-flux balance near the temperature minimum atop the photosphere. The study is based on the photospheric TiO broadband (1.0 nm) filter data acquired with the 1.6 m NST operating at the Big Bear Solar Observatory. The data set also includes NST off-band H{alpha} images collected through a Zeiss Lyot filter with a passband of 0.025 nm.

  18. On the mechanism of intergranular embrittlement by phosphorus in transformer steel

    NASA Astrophysics Data System (ADS)

    Thompson, R. G.; White, C. L.; Wert, J. J.; Easton, D. S.

    1981-07-01

    Transformer steel (Fe-6 at. pct Si) was doped with varying amounts of phosphorus and given an embrittling step-cool heat treatment. Auger electron spectroscopy was used to determine that large increases in intergranular phosphorus concentration occurred in approximate proportion to the bulk phosphorus level through an equilibrium segregation mechanism. Bicrystals of this material were fractured at 300, 77 and 4.2 K. Grain boundary fracture energy, γgb was determined as a function of intergranular phosphorus concentration at 4.2 K. An analysis of γgband fracture mode, as a function of temperature, was used to evaluate the relative merits of intergranular fracture models based on reduced interatomic separation energy (Gibbs-Griffith model) and reduced interatomic cohesive strength (Seah model). It was found that the reduced interatomic separation energy model best fits the experimental findings.

  19. Coercivity mechanism of α-Fe/Nd2Fe14B nanocomposite magnets with an intergranular amorphous phase

    NASA Astrophysics Data System (ADS)

    Zhang, Yongmei; Li, Wei; Li, Hailing; Zhang, Xiangyi

    2014-01-01

    Understanding the coercivity mechanism of nanocomposite magnets is essential for developing high-performance permanent magnets. In this study, the mechanism of coercivity enhancement in α-Fe/Nd2Fe14B nanocomposites with an intergranular amorphous phase has been studied. The homogeneity and strength of domain-wall pinning in the magnets are enhanced by the existence of an intergranular amorphous phase. The suitable exchange constant and thickness of the amorphous interface are favourable for simultaneously obtaining high coercivity and strong exchange coupling between hard and soft grains. The present work provides a way to achieve high coercivity in nanocomposite magnets by the modification of the interfacial structure.

  20. NGNP/HTE full-power operation at reduced high-temperature heat exchanger temperatures.

    SciTech Connect

    VIlim, R.; Nuclear Engineering Division

    2009-03-12

    Operation of the Next Generation Nuclear Plant (NGNP) with reduced reactor outlet temperature at full power was investigated for the High Temperature Electrolysis (HTE) hydrogen-production application. The foremost challenge for operation at design temperature is achieving an acceptably long service life for heat exchangers. In both the Intermediate Heat Exchanger (IHX) and the Process Heat Exchanger (PHX) (referred to collectively as high temperature heat exchangers) a pressure differential of several MPa exists with temperatures at or above 850 C. Thermal creep of the heat exchanger channel wall may severely limit heat exchanger life depending on the alloy selected. This report investigates plant performance with IHX temperatures reduced by lowering reactor outlet temperature. The objective is to lower the temperature in heat transfer channels to the point where existing materials can meet the 40 year lifetime needed for this component. A conservative estimate for this temperature is believed to be about 700 C. The reactor outlet temperature was reduced from 850 C to 700 C while maintaining reactor power at 600 MWt and high pressure compressor outlet at 7 MPa. We included a previously reported design option for reducing temperature at the PHX. Heat exchanger lengths were adjusted to reflect the change in performance resulting from coolant property changes and from resizing related to operating-point change. Turbomachine parameters were also optimized for the new operating condition. An integrated optimization of the complete system including heat transfer equipment was not performed. It is estimated, however, that by performing a pinch analysis the combined plant efficiency can be increased from 35.5 percent obtained in this report to a value between 38.5 and 40.1 percent. Then after normalizing for a more than three percent decrease in commodities inventory compared to the reference plant, the commodities-normalized efficiency lies between 40.0 and 41.3. This

  1. Modeling Selective Intergranular Oxidation of Binary Alloys

    SciTech Connect

    Xu, Zhijie; Li, Dongsheng; Schreiber, Daniel K.; Rosso, Kevin M.; Bruemmer, Stephen M.

    2015-01-07

    Intergranular attack of alloys under hydrothermal conditions is a complex problem that depends on metal and oxygen transport kinetics via solid-state and channel-like pathways to an advancing oxidation front. Experiments reveal very different rates of intergranular attack and minor element depletion distances ahead of the oxidation front for nickel-based binary alloys depending on the minor element. For example, a significant Cr depletion up to 9 µm ahead of grain boundary crack tips were documented for Ni-5Cr binary alloy, in contrast to relatively moderate Al depletion for Ni-5Al (~100s of nm). We present a mathematical kinetics model that adapts Wagner’s model for thick film growth to intergranular attack of binary alloys. The transport coefficients of elements O, Ni, Cr, and Al in bulk alloys and along grain boundaries were estimated from the literature. For planar surface oxidation, a critical concentration of the minor element can be determined from the model where the oxide of minor element becomes dominant over the major element. This generic model for simple grain boundary oxidation can predict oxidation penetration velocities and minor element depletion distances ahead of the advancing front that are comparable to experimental data. The significant distance of depletion of Cr in Ni-5Cr in contrast to the localized Al depletion in Ni-5Al can be explained by the model due to the combination of the relatively faster diffusion of Cr along the grain boundary and slower diffusion in bulk grains, relative to Al.

  2. Kohn–Sham exchange-correlation potentials from second-order reduced density matrices

    SciTech Connect

    Cuevas-Saavedra, Rogelio; Staroverov, Viktor N.; Ayers, Paul W.

    2015-12-28

    We describe a practical algorithm for constructing the Kohn–Sham exchange-correlation potential corresponding to a given second-order reduced density matrix. Unlike conventional Kohn–Sham inversion methods in which such potentials are extracted from ground-state electron densities, the proposed technique delivers unambiguous results in finite basis sets. The approach can also be used to separate approximately the exchange and correlation potentials for a many-electron system for which the reduced density matrix is known. The algorithm is implemented for configuration-interaction wave functions and its performance is illustrated with numerical examples.

  3. Modeling selective intergranular oxidation of binary alloys.

    PubMed

    Xu, Zhijie; Li, Dongsheng; Schreiber, Daniel K; Rosso, Kevin M; Bruemmer, Stephen M

    2015-01-01

    Intergranular attack of alloys under hydrothermal conditions is a complex problem that depends on metal and oxygen transport kinetics via solid-state and channel-like pathways to an advancing oxidation front. Experiments reveal very different rates of intergranular attack and minor element depletion distances ahead of the oxidation front for nickel-based binary alloys depending on the minor element. For example, a significant Cr depletion up to 9 μm ahead of grain boundary crack tips was documented for Ni-5Cr binary alloy, in contrast to relatively moderate Al depletion for Ni-5Al (∼100 s of nm). We present a mathematical kinetics model that adapts Wagner's model for thick film growth to intergranular attack of binary alloys. The transport coefficients of elements O, Ni, Cr, and Al in bulk alloys and along grain boundaries were estimated from the literature. For planar surface oxidation, a critical concentration of the minor element can be determined from the model where the oxide of minor element becomes dominant over the major element. This generic model for simple grain boundary oxidation can predict oxidation penetration velocities and minor element depletion distances ahead of the advancing front that are comparable to experimental data. The significant distance of depletion of Cr in Ni-5Cr in contrast to the localized Al depletion in Ni-5Al can be explained by the model due to the combination of the relatively faster diffusion of Cr along the grain boundary and slower diffusion in bulk grains, relative to Al. PMID:25573575

  4. Ignition calculations using a reduced coupled-mode electron- ion energy exchange model*

    NASA Astrophysics Data System (ADS)

    Garbett, W. J.; Chapman, D. A.

    2016-03-01

    Coupled-mode models for electron-ion energy exchange can predict large deviations from standard binary collision models in some regimes. A recently developed reduced coupled-mode model for electron-ion energy exchange, which accurately reproduces full numerical results over a wide range of density and temperature space, has been implemented in the Nym hydrocode and used to assess the impact on ICF capsule fuel assembly and performance. Simulations show a lack of sensitivity to the model, consistent with results from a range of simpler alternative models. Since the coupled-mode model is conceptually distinct to models based on binary collision theory, this result provides increased confidence that uncertainty in electron-ion energy exchange will not impact ignition attempts.

  5. The stabilizing role of itinerant ferromagnetism in inter-granular cohesion in iron

    NASA Astrophysics Data System (ADS)

    Yesilleten, D.; Arias, T. A.

    1998-03-01

    We recently have introduced a tight-binding energy-functional for ferromagnetic iron based upon a local spin density extension to the Stoner theory of itinerant ferromagnetism(D. Yesilleten, M. Nastar, T.A. Arias, A.T. Paxton, S. Yip (MIT preprint, September 1997)). In this talk, we report the predictions of the model for the magnetic structure of grain boundaries in iron. Our results indicate that inter-granular cohesion along twin boundaries is due in large part to an enhanced exchange interaction at the boundary, which dramatically reduces the grain boundary energy. We hypothesize that this is why simple atomistic models which do not include magnetic interactions explicitly, such as the embedded atom method (EAM), tend to overestimate grain boundary energies in iron. We present results which agree well both with experimental measurements of boundary energies and with recent ab initio calculations of the distribution of atomic spin moments near the Σ=5 symmetric tilt boundary.

  6. Grain boundary segregation and intergranular failure

    SciTech Connect

    White, C.L.

    1980-01-01

    Trace elements and impurities often segregate strongly to grain boundaries in metals and alloys. Concentrations of these elements at grain boundaries are often 10/sup 3/ to 10/sup 5/ times as great as their overall concentration in the alloy. Because of such segregation, certain trace elements can exert a disproportionate influence on material properties. One frequently observed consequence of trace element segregation to grain boundaries is the occurrence of grain boundary failure and low ductility. Less well known are incidences of improved ductility and inhibition of grain boundary fracture resulting from trace element segregation to grain boundaries in certain systems. An overview of trace element segregation and intergranular failure in a variety of alloy systems as well as preliminary results from studies on Al 3% Li will be presented.

  7. Amide proton exchange rates of oxidized and reduced Saccharomyces cerevisiae iso-1-cytochrome c.

    PubMed Central

    Marmorino, J. L.; Auld, D. S.; Betz, S. F.; Doyle, D. F.; Young, G. B.; Pielak, G. J.

    1993-01-01

    Proton NMR spectroscopy was used to determine the rate constant, kobs, for exchange of labile protons in both oxidized (Fe(III)) and reduced (Fe(II)) iso-1-cytochrome c. We find that slowly exchanging backbone amide protons tend to lack solvent-accessible surface area, possess backbone hydrogen bonds, and are present in regions of regular secondary structure as well as in omega-loops. Furthermore, there is no correlation between kobs and the distance from a backbone amide nitrogen to the nearest solvent-accessible atom. These observations are consistent with the local unfolding model. Comparisons of the free energy change for denaturation, delta Gd, at 298 K to the free energy change for local unfolding, delta Gop, at 298 K for the oxidized protein suggest that certain conformations possessing higher free energy than the denatured state are detected at equilibrium. Reduction of the protein results in a general increase in delta Gop. Comparisons of delta Gd to delta Gop for the reduced protein show that the most open states of the reduced protein possess more structure than its chemically denatured form. This persistent structure in high-energy conformations of the reduced form appears to involve the axially coordinated heme. PMID:8268806

  8. EXCHANGE

    SciTech Connect

    Boltz, J.C.

    1992-09-01

    EXCHANGE is published monthly by the Idaho National Engineering Laboratory (INEL), a multidisciplinary facility operated for the US Department of Energy (DOE). The purpose of EXCHANGE is to inform computer users about about recent changes and innovations in both the mainframe and personal computer environments and how these changes can affect work being performed at DOE facilities.

  9. Reduced impact logging minimally alters tropical rainforest carbon and energy exchange

    PubMed Central

    Miller, Scott D.; Goulden, Michael L.; Hutyra, Lucy R.; Keller, Michael; Saleska, Scott R.; Wofsy, Steven C.; Figueira, Adelaine Michela Silva; da Rocha, Humberto R.; de Camargo, Plinio B.

    2011-01-01

    We used eddy covariance and ecological measurements to investigate the effects of reduced impact logging (RIL) on an old-growth Amazonian forest. Logging caused small decreases in gross primary production, leaf production, and latent heat flux, which were roughly proportional to canopy loss, and increases in heterotrophic respiration, tree mortality, and wood production. The net effect of RIL was transient, and treatment effects were barely discernable after only 1 y. RIL appears to provide a strategy for managing tropical forest that minimizes the potential risks to climate associated with large changes in carbon and water exchange. PMID:22087005

  10. Hydrogen-deuterium exchange mass spectrometry for investigation of backbone dynamics of oxidized and reduced cytochrome P450cam.

    PubMed

    Hamuro, Yoshitomo; Molnar, Kathleen S; Coales, Stephen J; OuYang, Bo; Simorellis, Alana K; Pochapsky, Thomas C

    2008-02-01

    Backbone dynamics of the camphor monoxygenase cytochrome P450(cam) (CYP101) as a function of oxidation/ligation state of the heme iron were investigated via hydrogen/deuterium exchange (H/D exchange) as monitored by mass spectrometry. Main chain amide NH hydrogens can exchange readily with solvent and the rate of this exchange depends upon, among other things, dynamic fluctuations in local structural elements. A fluxional region of the polypeptide will exchange more quickly with solvent than one that is more constrained. In most regions of the enzyme, exchange rates were similar between oxidized high-spin camphor-bound and reduced camphor- and CO-bound CYP101 (CYP-S and CYP-S-CO, respectively). However, in regions of the protein that have previously been implicated in substrate access by structural and molecular dynamics investigations, the reduced enzyme shows significantly slower exchange rates than the oxidized CYP-S. This observation corresponds to increased flexibility of the oxidized enzyme relative to the reduced form. Structural features previously found to be perturbed in CYP-S-CO upon binding of the biologically relevant effector and reductant putidaredoxin (Pdx) as determined by nuclear magnetic resonance are also more protected from exchange in the reduced state. To our knowledge, this study represents the first experimental investigation of backbone dynamics within the P450 family using this methodology. PMID:18023482

  11. Adsorption of iodine on hydrogen-reduced silver-exchanged mordenite: Experiments and modeling

    DOE PAGESBeta

    Nan, Yue; Tavlarides, Lawrence L.; DePaoli, David W.

    2016-08-03

    The adsorption process of iodine, a major volatile radionuclide in the off-gas streams of spent nuclear fuel reprocessing, on hydrogen-reduced silver-exchanged mordenite (Ag0Z) was studied at the micro-scale. The gas-solid mass transfer and reaction involved in the adsorption process were investigated and evaluated with appropriate models. Optimal conditions for reducing the silver-exchanged mordenite (AgZ) in a hydrogen stream were determined. Kinetic and equilibrium data of iodine adsorption on Ag0Z were obtained by performing single-layer adsorption experiments with experimental systems of high precision at 373–473 K over various iodine concentrations. Results indicate approximately 91% to 97% of the iodine adsorption wasmore » through the silver-iodine reaction. The effect of temperature on the iodine loading capacity of Ag0Z was discussed. In conclusion, the Shrinking Core model describes the data well, and the primary rate controlling mechanisms were macro-pore diffusion and silver-iodine reaction. © 2016 American Institute of Chemical Engineers AIChE J, 2016« less

  12. Microchemistry of corroded intergranular surfaces. Final report

    SciTech Connect

    Gibbon, D.L.; Varsanik, R.G.

    1985-02-01

    Sections of Alloy 600 boiler tubes which had undergone multi-year exposure to typical conditions in a Babcock-and-Wilcox model boiler were received for examination of grain surfaces which had undergone intergranular attack during service. The primary problem was to prepare samples of the desired surface in a way that would not degrade it. This was accomplished by pneumatically inflating the tube sections until they burst; the ductile layer of Alloy 600 expanded plastically, while the exterior IGA layer did not. Subsequent twisting of the metal section caused the outer surface to drop off, exposing the IGA surfaces. Examination of these fresh surfaces was carried out by scanning electron microscopy (SEM), transmission electron microscopy (TEM), wavelength-dispersive x-ray spectroscopy (WDX), energy-dispersive x-ray spectroscopy (EDX), Auger electron spectroscopy (AES), and selected area diffraction (SAD). There appears to be a distinct film of material between the IGA grains on the order of 150 to 200A thick. This film has not been fully characterized, but has been found to be sodium and/or sulfur-rich. Electron diffraction suggests that this layer may consist of a mixed sodium/transition-metal oxide and a nickel sulfide. Confirmation of this hypothesis could best be accomplished by examination of ion-thinned sections of this material in an analytical electron microscope.

  13. Study of intergranular embrittlement in Fe-12Mn alloys

    SciTech Connect

    Lee, H.J.

    1982-06-01

    A high resolution scanning Auger microscopic study has been performed on the intergranular fracture surfaces of Fe-12Mn steels in the as-austenitized condition. Fracture mode below the ductile-brittle transition temperature was intergranular whenever the alloy was quenched from the austenite field. The intergranular fracture surface failed to reveal any consistent segregation of P, S, As, O, or N. The occasional appearance of S or O on the fracture surface was found to be due to a low density precipitation of MnS and MnO/sub 2/ along the prior austenite boundaries. An AES study with Ar/sup +/ ion-sputtering showed no evidence of manganese enrichment along the prior austenite boundaries, but a slight segregation of carbon which does not appear to be implicated in the tendency toward intergranular fracture. Addition of 0.002% B with a 1000/sup 0/C/1h/WQ treatment yielded a high Charpy impact energy at liquid nitrogen temperature, preventing the intergranular fracture. High resolution AES studies showed that 3 at. % B on the prior austenite grain boundaries is most effective in increasing the grain boundary cohesive strength in an Fe-12Mn alloy. Trace additions of Mg, Zr, or V had negligible effects on the intergranular embrittlement. A 450/sup 0/C temper of the boron-modified alloys was found to cause tempered martensite embrittlement, leading to intergranular fracture. The embrittling treatment of the Fe-12Mn alloys with and without boron additions raised the ductile-brittle transition by 150/sup 0/C. This tempered martensite embrittlement was found to be due to the Mn enrichment of the fracture surface to 32 at. % Mn in the boron-modified alloy and 38 at. % Mn in the unmodified alloy. The Mn-enriched region along the prior austenite grain boundaries upon further tempering is believed to cause nucleation of austenite and to change the chemistry of the intergranular fracture surfaces. 61 figures.

  14. Subzero temperature chromatography for reduced back-exchange and improved dynamic range in amide hydrogen/deuterium exchange mass spectrometry.

    PubMed

    Venable, John D; Okach, Linda; Agarwalla, Sanjay; Brock, Ansgar

    2012-11-01

    Amide hydrogen/deuterium exchange is a commonly used technique for studying the dynamics of proteins and their interactions with other proteins or ligands. When coupled with liquid chromatography and mass spectrometry, hydrogen/deuterium exchange provides several unique advantages over other structural characterization techniques including very high sensitivity, the ability to analyze proteins in complex environments, and a large mass range. A fundamental limitation of the technique arises from the loss of the deuterium label (back-exchange) during the course of the analysis. A method to limit loss of the label during the separation stage of the analysis using subzero temperature reversed-phase chromatography is presented. The approach is facilitated by the use of buffer modifiers that prevent freezing. We evaluated ethylene glycol, dimethyl formamide, formamide, and methanol for their freezing point suppression capabilities, effects on peptide retention, and their compatibilities with electrospray ionization. Ethylene glycol was used extensively because of its good electrospray ionization compatibility; however, formamide has potential to be a superior modifier if detrimental effects on ionization can be overcome. It is demonstrated using suitable buffer modifiers that separations can be performed at temperatures as low as -30 °C with negligible loss of the deuterium label, even during long chromatographic separations. The reduction in back-exchange is shown to increase the dynamic range of hydrogen/deuterium exchange mass spectrometry in terms of mixture complexity and the magnitude with which changes in deuteration level can be quantified. PMID:23025328

  15. Measurement of intergranular stress and porosity during dynamic compaction of porous beds of cyclotetramethylene tetranitramine

    NASA Astrophysics Data System (ADS)

    Greenaway, M. W.

    2005-05-01

    The dynamic compaction of granular beds of the propellant cyclotetramethylene tetranitramine (HMX) has been investigated using a modified split Hopkinson pressure bar system. Intergranular stress and bed porosity were simultaneously measured during controlled loading. The importance of grain size was investigated by comparing conventional HMX (mean particle size ˜260μm) to microfine HMX (<5μm). Samples were radially confined and compression was predetermined using special end caps. Initial porosity was varied by hydraulically pressing the beds prior to testing. With large grains, resistance to compaction increased with the solid volume fraction. Microfine HMX behaved like low porosity conventional HMX beds in all cases. Porosity was typically reduced by 5%-10% during compaction and intergranular stresses below the yield stress were ensured. Energy dissipation to plastic flow and fracture were largely eliminated. Optical particle size analysis and electron microscopy support the experimental observations.

  16. Minocycline, a microglial inhibitor, reduces ‘honey trap’ risk in human economic exchange

    PubMed Central

    Watabe, Motoki; Kato, Takahiro A.; Tsuboi, Sho; Ishikawa, Katsuhiko; Hashiya, Kazuhide; Monji, Akira; Utsumi, Hideo; Kanba, Shigenobu

    2013-01-01

    Recently, minocycline, a tetracycline antibiotic, has been reported to improve symptoms of psychiatric disorders and to facilitate sober decision-making in healthy human subjects. Here we show that minocycline also reduces the risk of the ‘honey trap’ during an economic exchange. Males tend to cooperate with physically attractive females without careful evaluation of their trustworthiness, resulting in betrayal by the female. In this experiment, healthy male participants made risky choices (whether or not to trust female partners, identified only by photograph, who had decided in advance to exploit the male participants). The results show that trusting behaviour in male participants significantly increased in relation to the perceived attractiveness of the female partner, but that attractiveness did not impact trusting behaviour in the minocycline group. Animal studies have shown that minocycline inhibits microglial activities. Therefore, this minocycline effect may shed new light on the unknown roles microglia play in human mental activities. PMID:23595250

  17. Detection of Intergranular Corrosion in Cold Plate Face Sheets

    NASA Technical Reports Server (NTRS)

    Winfree, William P.; Smith, Stephen W.; Piascik, Robert S.; Howell, Patricia A.

    2002-01-01

    Cold plates are critical for cooling electronic systems in the shuttle. As a result of the environmental conditions in which they operate, water can condense between them and a support shelf. In some cases, this water results in intergranular corrosion in the face sheet. If the intergranular corrosion sufficiently penetrates the face sheet, a coolant leak could occur and jeopardize cold plate operation. This paper examines techniques for detecting and characterizing the intergranular corrosion, to enable recertification of cold plates that have been in operation for 15 plus years. Intergranular corrosion was artificially induced in the face sheets of a series of cold plate specimens using an electrochemical process. Some of the cold plate specimens were separated for destructive characterization of the extent of corrosion produced by the electrochemical process and to insure the induced corrosion was intergranular. The rest of the specimens were characterized nondestructively using several techniques. X-ray tomography and ultrasonic techniques provided the best indication of corrosion in these specimens and will be the focus of this paper. An x-ray tomography technique was shown to be the most effective technique for characterizing depth of the intergranular corrosion. From these measurements, corrosion profile maps were developed that were consistent with subsequent destructive evaluations of the specimens. This enabled the assessment of NDE (ondestructive evaluation) standards to evaluate the viability of other NDE techniques. Due to system constraints, a different technique must be used to inspect an entire cold plate. An ultrasonic technique was shown to be very reliable for detection of corrosion in the unbacked regions of the face sheet. The ultrasonic technique was performed in an alcohol bath to avoid additional corrosion during the NDE evaluation. A pulse echo technique that focuses on the RMS value of the signal is shown to be very sensitive to the

  18. Discontinuous Inter-Granular Separations (DIGS) in the Gas Nitride Layer of ISS Race Rings

    NASA Technical Reports Server (NTRS)

    Figert, John; Dasgupta, Rajib; Martinez, James

    2010-01-01

    The starboard solar alpha rotary joint (SARJ) race ring on the International space station (ISS) failed due to severe spalling of the outer diameter, 45 degree (outer canted) nitrided surface. Subsequent analysis at NASA-KSC revealed that almost all of the debris generated due to the failure was nitrided 15-5 stainless steel. Subsequent analysis of the nitride control coupons (NCC) at NASA-JSC revealed the presence of discontinuous inter-granular separations (DIGS) in the gas nitride layer. These DIGS were present in the inter-granular networking located in the top 2 mils of the nitride layer. The manufacturer's specification requires the maximum white structure to be 0.0003 inches and intergranular networking below the allowable white structure depth to be cause for rejection; a requirement that the NCCs did not meet. Subsequent testing and analysis revealed that lower DIGS content significantly lowered the probability of nitride spalling in simulated, dry condition runs. One batch of nitride samples with DIGS content similar to the port SARJ (did not fail on orbit) which exhibited almost no nitride spalling after being run on one test rig. Another batch of nitride samples with DIGS content levels similar to the starboard SARJ exhibited significant nitride spalling on the same test rig with the same load under dry conditions. Although DIGS were not the root cause of starboard race ring failure, testing indicates that increased DIGS reduced the robustness of the gas nitride layer under dry operating conditions.

  19. Intergranular stress distributions in polycrystalline aggregates of irradiated stainless steel

    NASA Astrophysics Data System (ADS)

    Hure, J.; El Shawish, S.; Cizelj, L.; Tanguy, B.

    2016-08-01

    In order to predict InterGranular Stress Corrosion Cracking (IGSCC) of post-irradiated austenitic stainless steel in Light Water Reactor (LWR) environment, reliable predictions of intergranular stresses are required. Finite elements simulations have been performed on realistic polycrystalline aggregate with recently proposed physically-based crystal plasticity constitutive equations validated for neutron-irradiated austenitic stainless steel. Intergranular normal stress probability density functions are found with respect to plastic strain and irradiation level, for uniaxial loading conditions. In addition, plastic slip activity jumps at grain boundaries are also presented. Intergranular normal stress distributions describe, from a statistical point of view, the potential increase of intergranular stress with respect to the macroscopic stress due to grain-grain interactions. The distributions are shown to be well described by a master curve once rescaled by the macroscopic stress, in the range of irradiation level and strain considered in this study. The upper tail of this master curve is shown to be insensitive to free surface effect, which is relevant for IGSCC predictions, and also relatively insensitive to small perturbations in crystallographic texture, but sensitive to grain shapes.

  20. Photochemical and ligand-exchange properties of the cyanide complex of fully reduced cytochrome c oxidase.

    PubMed Central

    Hill, B C; Marmor, S

    1991-01-01

    Cytochrome oxidase, in its fully reduced state, forms a complex with CN having a Kd of 230 microM with a stoicheiometry of 1 CN molecule per cytochrome oxidase. We do not detect a second CN-binding site as seen by i.r. spectroscopy [Yoshikawa & Caughey (1990) J. Biol. Chem. 265, 7945-7958]. The ferrocytochrome a3-CN complex, like the analogous ferrocytochrome a3-CO complex, is photosensitive but with a 15-fold lower quantum yield for photolysis. Analysis of the recombination kinetics after CN photolysis establishes a simple bimolecular binding constant of 235 M-1.s-1, in agreement with the value obtained from stopped-flow studies [Antonini, Brunori, Greenwood, Malmström & Rotillo (1971) Eur. J. Biochem. 23, 396-400]. A rate of 0.07 s-1 for the first-order dissociation of CN from cytochrome a3 is found by the rate of exchange of CO with ferrocytochrome a3-CN, and is consistent with the value calculated from the equilibrium binding constant and the CN on rate. However, O2 is able to oxidize the fully reduced CN compound at a rate well in excess of the CN off rate. The product of this oxidation reaction is a partially reduced CN complex. This implies that O2 either promotes CN dissociation or is able to oxidize the CN-bound enzyme directly. These results are discussed in the context of the structure and dynamics of the ligand-binding site of cytochrome oxidase. PMID:1659377

  1. Quantifying and Reducing Uncertainty in Eddy Covariance CO2 Exchange Estimates With Large Data Gaps.

    NASA Astrophysics Data System (ADS)

    Brodeur, J. J.; Arain, M. A.; Peichl, M.

    2009-05-01

    Roving eddy covariance (rEC) applications involve cycling a single, portable rEC system through numerous ecosystems of interest at frequencies of weeks to months. This approach provides capability to measure energy, water and carbon exchanges in many more ecosystems with minimum resources. This approach has been adopted at many flux stations with multiple towers or sites. However, data gaps introduce large uncertainty when sums of annual exchanges are estimated from these measurements. Quantifying reliable carbon uptake/loss estimates, and reducing uncertainty is challenging. Analyses were performed with 5 years of net ecosystem CO2 exchange (NEE) measurements made over an age-sequence of managed eastern white pine (Pinus strobus L.) forests in southern Ontario, Canada. Measurements and synthetic data produced from a permanent closed-path EC system at the 70-year-old site were used to assess uncertainty on annual NEE sums caused by open-path rEC operation at three younger sites (35, 20 and 7 years old). Data was removed both randomly (to simulate short gaps due to typical EC operation), and systematically (to simulate 2-week to 2-month long gaps associated with rEC operation). Numerous gap scenarios were created, with annual data coverage ranging from 35 to 70%. Both Ameriflux Howland (HOW) and Fluxnet Canada Research Network (FCRN) gap-filling models were applied to the gapped-data to produce annual NEE estimates. Both gap-filling methods estimated a baseline uncertainty of ± 25 g C m-2 yr-1, that was associated with short gaps from regular EC operation only. However, when applied to datasets with long rEC gaps, a large discrepancy in gap-filling model performance was evident. The HOW method produced much less overall uncertainty (± 30 to 45 g C m-2 yr-1) in annual sums than the FCRN method (± 45 to > 200 g C m-2 yr-1). Uncertainty in annual sums increased with increases to overall gap frequency and length, as a result of inadequate parameterization of gap

  2. Further Study of near Solidus Intergranular Cracking in Inconel 718

    NASA Technical Reports Server (NTRS)

    Thompson, R. G.

    1981-01-01

    A series of tests, performed to determine the strain necessary to initiate intergranular cracking in Inconel 718 as a function of temperature, contained enough scatter near the melting temperature that questions remained as to the best curve of curves to fit to the data. Fracture surface analysis showed that the scatter was due to incipient melting in the grain boundary region. The melting contributed to low fracture strain but had only a small on the incipient cracking strain. Gleeble tests, which could be interrupted by water quenching, were used to study the incipient intergranular melting of Inconel 718. This modified weld simulation test provided a sufficiently rapid quench to preserve the intergranular microstructure created during incipient melting. This structure was studied both microscopically and with energy dispensive X-ray analysis. The implications of incipient melting and low-strain incipient cracking on the development of microfissuring envelopes are discussed.

  3. Hydrogen Isotope Separation by Combined Electrolysis Catalytic Exchange Under Reduced Pressure

    SciTech Connect

    Sugiyama, T.; Asakura, Y.; Uda, T.; Abe, Y.; Shiozaki, T.; Enokida, Y.; Yamamoto, I.

    2005-07-15

    At the National Institute for Fusion Science experimental studies on hydrogen isotope separation by a Combined Electrolysis Catalytic Exchange (CECE) process have been carried out in order to apply it to the system of water detritiation for D-D burning experiments of the Large Helical Device. As an improvement of the CECE process, we have developed a reduced-pressure method as a means of enhancing the separation factor. The feasibility of this method is examined through application to a CECE process using a prototype separation column. Hydrogen-deuterium isotope separation experiments are performed in the two cases where column pressures are 12 and 101 kPa, and the separation factors for hydrogen and deuterium are obtained as 6.8 and 5.6, respectively. It is confirmed that the present method is applicable and useful to the CECE process. The values of Height Equivalent to a Theoretical Plate (HETP) are estimated by analyses with the equilibrium stage model. The HETP values are 15 cm at 12 kPa and 13 cm at 101 kPa. The increase of superficial velocity with decreasing pressure may spoil the efficiency of the mass transfer.

  4. Mechanism of hydrodenitrogenation H sub 2 -D sub 2 exchange in reduced molybdenum catalysts

    SciTech Connect

    Miranda, R.

    1991-01-01

    Diffuse reflectance infrared spectroscopy was used to study the deuterium exchangeability of reduced molybdena catalysts supported on silica, alumina and 75% silica-alumina. It was found that silica hydroxyls react partially with deposited molybdena. The new species formed does not lead to regeneration of hydroxyl on the catalyst. On the other hand, the interaction of molybdena with alumina or silica-alumina leads to the generation of interfacial OH groups, that compensate for the hydroxyls lost to reaction. In this project is a proposed that the selectivity of the Hydrodenitrogenation (HDN) reaction can be affected by an alteration of the catalyst acidity since it is possible that an acidic Hofmann-like deamination pathway is operative (1) in parallel with the hydrogenolysis of saturated C--N--C bonds. Such was the conclusion from the study done of the denitrogenation of piperidine (3), where it was demonstrated that Bronsted acid sites are active for the denitrogenation of N-heterocycles where as Lewis sites are not.

  5. The Art of Living Together: Reducing Stereotyping and Prejudicial Attitudes through the Arab-Jewish Class Exchange Program (CEP)

    ERIC Educational Resources Information Center

    Berger, Rony; Abu-Raiya, Hisham; Gelkopf, Marc

    2015-01-01

    This study evaluated the efficacy of a newly developed Arab-Jewish Class Exchange Program (CEP) in reducing stereotyping and prejudicial attitudes between Israeli-Jewish and Israeli-Palestinian children. The CEP builds on the core principles of contact theory and is designed to help participants cultivate empathy and tolerance toward the other.…

  6. Reduced sodium/proton exchanger NHE3 activity causes congenital sodium diarrhea.

    PubMed

    Janecke, Andreas R; Heinz-Erian, Peter; Yin, Jianyi; Petersen, Britt-Sabina; Franke, Andre; Lechner, Silvia; Fuchs, Irene; Melancon, Serge; Uhlig, Holm H; Travis, Simon; Marinier, Evelyne; Perisic, Vojislav; Ristic, Nina; Gerner, Patrick; Booth, Ian W; Wedenoja, Satu; Baumgartner, Nadja; Vodopiutz, Julia; Frechette-Duval, Marie-Christine; De Lafollie, Jan; Persad, Rabindranath; Warner, Neil; Tse, C Ming; Sud, Karan; Zachos, Nicholas C; Sarker, Rafiquel; Zhu, Xinjun; Muise, Aleixo M; Zimmer, Klaus-Peter; Witt, Heiko; Zoller, Heinz; Donowitz, Mark; Müller, Thomas

    2015-12-01

    Congenital sodium diarrhea (CSD) refers to an intractable diarrhea of intrauterine onset with high fecal sodium loss. CSD is clinically and genetically heterogeneous. Syndromic CSD is caused by SPINT2 mutations. While we recently described four cases of the non-syndromic form of CSD that were caused by dominant activating mutations in intestinal receptor guanylate cyclase C (GC-C), the genetic cause for the majority of CSD is still unknown. Therefore, we aimed to determine the genetic cause for non-GC-C non-syndromic CSD in 18 patients from 16 unrelated families applying whole-exome sequencing and/or chromosomal microarray analyses and/or direct Sanger sequencing. SLC9A3 missense, splicing and truncation mutations, including an instance of uniparental disomy, and whole-gene deletion were identified in nine patients from eight families with CSD. Two of these nine patients developed inflammatory bowel disease (IBD) at 4 and 16 years of age. SLC9A3 encodes Na(+)/H(+) antiporter 3 (NHE3), which is the major intestinal brush-border Na(+)/H(+) exchanger. All mutations were in the NHE3 N-terminal transport domain, and all missense mutations were in the putative membrane-spanning domains. Identified SLC9A3 missense mutations were functionally characterized in plasma membrane NHE null fibroblasts. SLC9A3 missense mutations compromised NHE3 activity by reducing basal surface expression and/or loss of basal transport function of NHE3 molecules, whereas acute regulation was normal. This study identifies recessive mutations in NHE3, a downstream target of GC-C, as a cause of CSD and implies primary basal NHE3 malfunction as a predisposition for IBD in a subset of patients. PMID:26358773

  7. Intergranular fracture in an Al-Li-Cu-Mg-Zr alloy

    SciTech Connect

    Wert, J.A.; Lumsden, J.B.

    1985-02-01

    The intergranular fracture characteristics of the Al-Li-Cu-Mg-Zr alloy is studied for underaged (170 C/4 hr) and overaged (230 C/4 hr) conditions. In addition, extensive intergranular fracture parallel to the tensile axis (delamination) in longitudinal tensile specimens is found together with equal concentration of K on all intergranular fracture surfaces independent of aging treatment. K is believed to promote intergranular fracture in Al-Li alloys similarly to a Na presence. 7 references.

  8. The concept and fabrication of exchange switchable trilayer of FePt/FeRh/FeCo with reduced switching field

    NASA Astrophysics Data System (ADS)

    Zhou, T. J.; Cher, K.; Hu, J. F.; Yuan, Z. M.; Liu, B.

    2012-04-01

    We report the concept and fabrication of exchange switchable trilayer of FePt/FeRh/FeCo with reduced switching field for heat assisted magnetic recording (HAMR). A thin layer of FeRh is sandwiched between L10 FePt and magnetically soft FeCo. At room temperature, FePt and FeCo are magnetically isolated by the antiferromagnetic FeRh layer. After the metamagnetic transition of FeRh layer by heating, FePt and FeCo are exchange-coupled together through ferromagnetic FeRh layer. Therefore, the switching field of FePt can be greatly reduced via exchange-spring effect. Simulation work was carried out to understand the exchange coupling strength and the FeCo thickness effects on the switching field reduction. It is found that switching field decreases with the increase of exchange coupling strength and FeCo thickness. The trilayer films were also successfully fabricated. A clear change of reversal mechanism from two-step to one-step switching upon heating was observed and a 3-time switching field reduction was demonstrated. The results show the promise of the trilayer for HAMR applications.

  9. by ligand exchange: utilizing energy level alignment for efficiently reducing carrier rec ombination

    NASA Astrophysics Data System (ADS)

    Wang, Xia; Kou, Dong-Xing; Zhou, Wen-Hui; Zhou, Zheng-Ji; Wu, Si-Xin; Cao, Xuan

    2014-05-01

    In this work, we employed a convenient one-step synthesis method for synthesizing Cu2ZnSnSe4 (CZTSe) nanocrystals (NCs) in an excess selenium environment. This excess selenium situation enhanced the reaction of metal acetylacetonates with selenium, resulting in the burst nucleation of NCs at relatively low temperatures. The phase morphology and surface and optoelectronic properties of NCs before and after ligand exchange were discussed in depth. It was found that pure tetragonal-phase structure CZTSe NCs with approximately 1.7-eV bandgap could be synthesized. The removal of large organic molecules on CZTSe NCs after ligand exchange by S2- decreased the resistivity. The bandgap of the films after ligand exchange by 550°C selenization was also decreased due to better crystallinity. For potential application in CZTSe solar cells, we constructed an energy level diagram to explain the mutual effect between the absorption layer and CdS layer. Using cyclic voltammetry (CV) measurement, we found that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of CZTSe films shifted down after ligand exchange. After energy level alignment at the CdS/CZTSe interface, a type I band alignment structure was more conveniently formed after ligand exchange. This structure acted as the barrier against injection electrons from ZnO to the CZTSe layer, and recombination would subsequently be depressed.

  10. Reducing Pica by Teaching Children to Exchange Inedible Items for Edibles

    ERIC Educational Resources Information Center

    Kern, Lee; Starosta, Kristin; Adelman, Barry Eshkol

    2006-01-01

    Assessment results indicated that pica exhibited by two boys with developmental disabilities was not associated with environmental contingencies. Consistent with previous research, an oral stimulation function was hypothesized. A related intervention that taught participants to exchange inedible items for edibles was developed. Findings showed…

  11. Study of Ram-air Heat Exchangers for Reducing Turbine Cooling-air Temperature of a Supersonic Aircraft Turbojet Engine

    NASA Technical Reports Server (NTRS)

    Diaguila, Anthony J; Livingood, John N B; Eckert, Ernst R G

    1956-01-01

    The sizes and weights of the cores of heat exchangers were determined analytically for possible application for reducing turbine cooling-air temperatures of an engine designed for a Mach number of 2.5 and an altitude The sizes and weights of the cores of heat exchangers were determined analytically for possible application for reducing turbine cooling-air temperatures of an engine designed for a Mach number of 2.5 and an altitude of 70,000 feet. A compressor-bleed-air weight flow of 2.7 pounds per second was assumed for the coolant; ram air was considered as the other fluid. Pressure drops and inlet states of both fluids were prescribed, and ranges of compressor-bleed-air temperature reductions and of the ratio of compressor-bleed to ram-air weight flows were considered.

  12. Measurement of intergranular attack in stainless steel using ultrasonic energy

    DOEpatents

    Mott, Gerry; Attaar, Mustan; Rishel, Rick D.

    1989-08-08

    Ultrasonic test methods are used to measure the depth of intergranular attack (IGA) in a stainless steel specimen. The ultrasonic test methods include a pitch-catch surface wave technique and a through-wall pulse-echo technique. When used in combination, these techniques can establish the extent of IGA on both the front and back surfaces of a stainless steel specimen from measurements made on only one surface.

  13. Intergranular degradation assessment via random grain boundary network analysis

    DOEpatents

    Kumar, Mukul; Schwartz, Adam J.; King, Wayne E.

    2002-01-01

    A method is disclosed for determining the resistance of polycrystalline materials to intergranular degradation or failure (IGDF), by analyzing the random grain boundary network connectivity (RGBNC) microstructure. Analysis of the disruption of the RGBNC microstructure may be assess the effectiveness of materials processing in increasing IGDF resistance. Comparison of the RGBNC microstructures of materials exposed to extreme operating conditions to unexposed materials may be used to diagnose and predict possible onset of material failure due to

  14. Intergranular Strain Evolution near Fatigue Crack Tips in Polycrystalline Metals

    SciTech Connect

    Zheng, Lili; Gao, Yanfei; Lee, Sooyeol; Barabash, Rozaliya; Lee, Jinhaeng; Liaw, Peter K

    2011-01-01

    The deformation field near a steady fatigue crack includes a plastic zone in front of the crack tip and a plastic wake behind it, and the magnitude, distribution, and history of the residual strain along the crack path depend on the stress multiaxiality, material properties, and history of stress intensity factor and crack growth rate. An in situ, full-field, non-destructive measurement of lattice strain (which relies on the intergranular interactions of the inhomogeneous deformation fields in neighboring grains) by neutron diffraction techniques has been performed for the fatigue test of a Ni-based superalloy compact tension specimen. These microscopic grain level measurements provided unprecedented information on the fatigue growth mechanisms. A two-scale model is developed to predict the lattice strain evolution near fatigue crack tips in polycrystalline materials. An irreversible, hysteretic cohesive interface model is adopted to simulate a steady fatigue crack, which allows us to generate the stress/strain distribution and history near the fatigue crack tip. The continuum deformation history is used as inputs for the micromechanical analysis of lattice strain evolution using the slip-based crystal plasticity model, thus making a mechanistic connection between macro- and micro-strains. Predictions from perfect grain-boundary simulations exhibit the same lattice strain distributions as in neutron diffraction measurements, except for discrepancies near the crack tip within about one-tenth of the plastic zone size. By considering the intergranular damage, which leads to vanishing intergranular strains as damage proceeds, we find a significantly improved agreement between predicted and measured lattice strains inside the fatigue process zone. Consequently, the intergranular damage near fatigue crack tip is concluded to be responsible for fatigue crack growth.

  15. Reducing calls missed by the hospital telephone exchange from 26% to less than 10%

    PubMed Central

    Bhartia, Saru; Bahlvi, Zorba; Sharma, Irina

    2016-01-01

    A hospital's telephone exchange is the first point of contact for patients and their attendants to take appointments, to collect healthcare related information and to connect to the hospital in case of emergencies. At Sitaram Bhartia Institute of Science and Research the doctors, patients, and attendants often complained about the inefficiency of the hospital exchange. In February 2012, a doctor raised her concern of calls not being picked up at the exchange with the senior management and a QI project was initiated to tackle the problem. Baseline data showed that about 26% of incoming calls to the hospital during 8am to 8pm were not being picked up. On the basis of the baseline data, call audits, staff interviews, and observations the project team identified the defects. These defects were categorized under four headings - manpower, equipment, processes, and environment. The team proposed several change ideas. Some of these change ideas were implemented immediately. Three proposed change ideas were tested through individual PDSA cycles. The percentage of missed calls dropped from 26% to 18.1% after the first cycle and then to 9.6% and 6.5% after the subsequent cycles which involved testing of two other additional change ideas. These changes were implemented and a benchmark of no more than 10% calls to be missed was set. For nearly three years we have held the gains and have met the benchmark of missing not more than 10% calls coming to the hospital exchange between 8am to 8pm. The contributing factors to the success have been the involvement of frontline workers, an expert and engaged head of department, and senior leadership support. PMID:26893896

  16. Reducing calls missed by the hospital telephone exchange from 26% to less than 10.

    PubMed

    Bhartia, Saru; Bahlvi, Zorba; Sharma, Irina

    2016-01-01

    A hospital's telephone exchange is the first point of contact for patients and their attendants to take appointments, to collect healthcare related information and to connect to the hospital in case of emergencies. At Sitaram Bhartia Institute of Science and Research the doctors, patients, and attendants often complained about the inefficiency of the hospital exchange. In February 2012, a doctor raised her concern of calls not being picked up at the exchange with the senior management and a QI project was initiated to tackle the problem. Baseline data showed that about 26% of incoming calls to the hospital during 8am to 8pm were not being picked up. On the basis of the baseline data, call audits, staff interviews, and observations the project team identified the defects. These defects were categorized under four headings - manpower, equipment, processes, and environment. The team proposed several change ideas. Some of these change ideas were implemented immediately. Three proposed change ideas were tested through individual PDSA cycles. The percentage of missed calls dropped from 26% to 18.1% after the first cycle and then to 9.6% and 6.5% after the subsequent cycles which involved testing of two other additional change ideas. These changes were implemented and a benchmark of no more than 10% calls to be missed was set. For nearly three years we have held the gains and have met the benchmark of missing not more than 10% calls coming to the hospital exchange between 8am to 8pm. The contributing factors to the success have been the involvement of frontline workers, an expert and engaged head of department, and senior leadership support. PMID:26893896

  17. Reducing risk, producing order: The surprisingly disciplinary world of needle exchange

    PubMed Central

    McLEAN, KATHERINE

    2015-01-01

    Emphasizing the reduction of risk over the cessation of drug use, needle exchange in the United States is often condemned for coddling its participants. Declining the punitive measures or unwavering teleology of criminal justice and drug treatment approaches, harm-reduction measures in general are faulted by naysayers for their refusal to establish clear normative boundaries for behavior modification. This article will seek to subvert such critiques by describing the ways in which disciplinary technologies suffused one needle exchange program in New York City. Drawing upon 1 year of participant observation at “Bronx Harm Reduction,” this article will consider how the “minor procedures” of disciplinary power first characterized by Foucault (1977) worked to shape and organize different user bodies in needle exchange; it will further employ the work of Mitchell Dean to reflect upon the connections between program-level “technologies of agency” and government-led “technologies of performance.” While conceding the overarching disciplinary transformation of late harm reduction, this article is specifically interested in the ramifications of this trajectory within one specific time and place. Namely, it postulates that attempts to “raise the bar” within a low-threshold program may serve to alienate or explicitly exclude certain service users. PMID:26221058

  18. Reducing the Cation Exchange Capacity of Lithium Clay to Form Better Dispersed Polymer-Clay Nanocomposites

    NASA Technical Reports Server (NTRS)

    Liang, Maggie

    2004-01-01

    Polymer-clay nanocomposites have exhibited superior strength and thermo- oxidative properties as compared to pure polymers for use in air and space craft; however, there has often been difficulty completely dispersing the clay within the matrices of the polymer. In order to improve this process, the cation exchange capacity of lithium clay is first lowered using twenty-four hour heat treatments of no heat, 130 C, 150 C, or 170 C to fixate the lithium ions within the clay layers so that they are unexchangeable. Generally, higher temperatures have generated lower cation exchange capacities. An ion exchange involving dodecylamine, octadecylamine, or dimethyl benzidine (DMBZ) is then employed to actually expand the clay galleries. X-ray diffraction and transmission electron microscopy can be used to determine whether the clay has been successfully exfoliated. Finally, resins of DMBZ with clay are then pressed into disks for characterization using dynamic mechanical analyzer and oven- aging techniques in order to evaluate their glass transition, modulus strength, and thermal-oxidative stability in comparison to neat DMBZ. In the future, they may also be tested as composites for flexural and laminar shear strength.

  19. Mice with a Targeted Disruption of the Cl−/HCO3− Exchanger AE3 Display a Reduced Seizure Threshold

    PubMed Central

    Hentschke, Moritz; Wiemann, Martin; Hentschke, Suna; Kurth, Ingo; Hermans-Borgmeyer, Irm; Seidenbecher, Thomas; Jentsch, Thomas J.; Gal, Andreas; Hübner, Christian A.

    2006-01-01

    Neuronal activity results in significant pH shifts in neurons, glia, and interstitial space. Several transport mechanisms are involved in the fine-tuning and regulation of extra- and intracellular pH. The sodium-independent electroneutral anion exchangers (AEs) exchange intracellular bicarbonate for extracellular chloride and thereby lower the intracellular pH. Recently, a significant association was found with the variant Ala867Asp of the anion exchanger AE3, which is predominantly expressed in brain and heart, in a large cohort of patients with idiopathic generalized epilepsy. To analyze a possible involvement of AE3 dysfunction in the pathogenesis of seizures, we generated an AE3-knockout mouse model by targeted disruption of Slc4a3. AE3-knockout mice were apparently healthy, and neither displayed gross histological and behavioral abnormalities nor spontaneous seizures or spike wave complexes in electrocorticograms. However, the seizure threshold of AE3-knockout mice exposed to bicuculline, pentylenetetrazole, or pilocarpine was reduced, and seizure-induced mortality was significantly increased compared to wild-type littermates. In the pyramidal cell layer of the hippocampal CA3 region, where AE3 is strongly expressed, disruption of AE3 abolished sodium-independent chloride-bicarbonate exchange. These findings strongly support the hypothesis that AE3 modulates seizure susceptibility and, therefore, are of significance for understanding the role of intracellular pH in epilepsy. PMID:16354689

  20. Expanded syringe exchange programs and reduced HIV infection among new injection drug users in Tallinn, Estonia

    PubMed Central

    2011-01-01

    Background Estonia has experienced an HIV epidemic among intravenous drug users (IDUs) with the highest per capita HIV prevalence in Eastern Europe. We assessed the effects of expanded syringe exchange programs (SEP) in the capital city, Tallinn, which has an estimated 10,000 IDUs. Methods SEP implementation was monitored with data from the Estonian National Institute for Health Development. Respondent driven sampling (RDS) interview surveys with HIV testing were conducted in Tallinn in 2005, 2007 and 2009 (involving 350, 350 and 327 IDUs respectively). HIV incidence among new injectors (those injecting for < = 3 years) was estimated by assuming (1) new injectors were HIV seronegative when they began injecting, and (2) HIV infection occurred at the midpoint between first injection and time of interview. Results SEP increased from 230,000 syringes exchanged in 2005 to 440,000 in 2007 and 770,000 in 2009. In all three surveys, IDUs were predominantly male (80%), ethnic Russians (>80%), and young adults (mean ages 24 to 27 years). The proportion of new injectors decreased significantly over the years (from 21% in 2005 to 12% in 2009, p = 0.005). HIV prevalence among all respondents stabilized at slightly over 50% (54% in 2005, 55% in 2007, 51% in 2009), and decreased among new injectors (34% in 2005, 16% in 2009, p = 0.046). Estimated HIV incidence among new injectors decreased significantly from 18/100 person-years in 2005 and 21/100 person-years in 2007 to 9/100 person-years in 2009 (p = 0.026). Conclusions In Estonia, a transitional country, a decrease in the HIV prevalence among new injectors and in the numbers of people initiating injection drug use coincided with implementation of large-scale SEPs. Further reductions in HIV transmission among IDUs are still required. Provision of 70 or more syringes per IDU per year may be needed before significant reductions in HIV incidence occur. PMID:21718469

  1. 76 FR 10038 - Determination That a Demonstration Needle Exchange Program Would be Effective in Reducing Drug...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-23

    ... Drug Abuse and the Risk of Acquired Immune Deficiency Syndrome Infection Among Intravenous Drug Users... program or SSP) would be effective in reducing drug abuse and the risk of infection with the...

  2. Reducing Intimate and Paying Partner Violence Against Women Who Exchange Sex in Mongolia: Results From a Randomized Clinical Trial

    PubMed Central

    Carlson, Catherine E.; Chen, Jiehua; Chang, Mingway; Batsukh, Altantsetseg; Toivgoo, Aira; Riedel, Marion; Witte, Susan S.

    2014-01-01

    Women who exchange sex for money or other goods, that is, female sex workers, are at increased risk of experiencing physical and sexual violence from both paying and intimate partners. Exposure to violence can be exacerbated by alcohol use and HIV/STI risk. The purpose of this study is to examine the efficacy of a HIV/STI risk reduction and enhanced HIV/ STI risk reduction intervention at decreasing paying and intimate partner violence against Mongolian women who exchange sex and engage in harmful alcohol use. Women are recruited and randomized to either (a) four sessions of a relationship-based HIV/STI risk reduction intervention (n = 49), (b) the same HIV/STI risk reduction intervention plus two additional motivational interviewing sessions (n = 58), or (c) a four session control condition focused on wellness promotion (n = 59). All the respondents complete assessments at baseline (preintervention) as well as at immediate posttest, 3 and 6 months postintervention. A multilevel logistic model finds that women who participated in the HIV/STI risk reduction group (OR = 0.14, p < .00), HIV/STI risk reduction and motivational interview group (OR = 0.46, p = .02), and wellness (OR = 0.20, p < .00) group reduced their exposure to physical and sexual violence in the past 90 days. No significant differences in effects are observed between conditions. This study demonstrates the efficacy of a relationship-based HIV/STI risk reduction intervention, a relationship-based HIV/STI risk reduction intervention combined with motivational interviewing, and a wellness promotion intervention in reducing intimate and paying partner violence against women who exchange sex in Mongolia. The findings have significant implications for the impact of minimal intervention and the potential role of peer networks and social support in reducing women’s experiences of violence in resource poor settings. PMID:22366477

  3. Reducing intimate and paying partner violence against women who exchange sex in Mongolia: results from a randomized clinical trial.

    PubMed

    Carlson, Catherine E; Chen, Jiehua; Chang, Mingway; Batsukh, Altantsetseg; Toivgoo, Aira; Riedel, Marion; Witte, Susan S

    2012-07-01

    Women who exchange sex for money or other goods, that is, female sex workers, are at increased risk of experiencing physical and sexual violence from both paying and intimate partners. Exposure to violence can be exacerbated by alcohol use and HIV/STI risk. The purpose of this study is to examine the efficacy of a HIV/STI risk reduction and enhanced HIV/STI risk reduction intervention at decreasing paying and intimate partner violence against Mongolian women who exchange sex and engage in harmful alcohol use. Women are recruited and randomized to either (a) four sessions of a relationship-based HIV/STI risk reduction intervention (n = 49), (b) the same HIV/STI risk reduction intervention plus two additional motivational interviewing sessions (n = 58), or (c) a four session control condition focused on wellness promotion (n = 59). All the respondents complete assessments at baseline (preintervention) as well as at immediate posttest, 3 and 6 months postintervention. A multilevel logistic model finds that women who participated in the HIV/STI risk reduction group (OR = 0.14, p < .00), HIV/STI risk reduction and motivational interview group (OR = 0.46, p = .02), and wellness (OR = 0.20, p < .00) group reduced their exposure to physical and sexual violence in the past 90 days. No significant differences in effects are observed between conditions. This study demonstrates the efficacy of a relationship-based HIV/STI risk reduction intervention, a relationship-based HIV/STI risk reduction intervention combined with motivational interviewing, and a wellness promotion intervention in reducing intimate and paying partner violence against women who exchange sex in Mongolia. The findings have significant implications for the impact of minimal intervention and the potential role of peer networks and social support in reducing women's experiences of violence in resource poor settings. PMID:22366477

  4. Effects of Intergranular Gas Bubbles on Thermal Conductivity

    SciTech Connect

    K. Chockalingam; Paul C. Millett; M. R. Tonks

    2012-11-01

    Model microstructures obtained from phase-field simulations are used to study the effective heat transfer across bicrys- tals with stationary grain boundary bubble populations. We find that the grain boundary coverage, irrespective of the intergranular bubble radii, is the most relevant parameter to the thermal resistance, which we use to derive effec- tive Kapitza resistances that are dependent on the grain boundary coverage and Kaptiza resistance of the intact grain boundary. We propose a model to predict thermal conductivity as a function of porosity, grain-size, Kaptiza resistance of the intact grain boundary, and grain boundary bubble coverage.

  5. Indirect measurement of the viscosity of the intergranular glass phase in yttria-sintered silicon nitride

    NASA Technical Reports Server (NTRS)

    Dittmar, Mark B.; Drummond, Charles H., III

    1991-01-01

    Dense, sintered Si3N4 possesses a residual intergranular glass phase which softens at high temperatures, resulting in degradation of the ceramic's mechanical properties at high temperatures. An important parameter in the determination of the high temperature mechanical properties of sintered Si3N4 is the temperature-viscosity relationship of the intergranular glass. A method for indirectly measuring the intergranular glass viscosity at a given temperature using physical modelling of a two phase glass crystal microstructure and beam bending viscometry measurements of Si3N4 is described. Intergranular glass viscosities obtained by this method are presented for a yttria sintered Si3N4.

  6. Intergranular failures of Alloy 600 in high temperature caustic environments

    SciTech Connect

    Bandy, R.; Roberge, R.; van Rooyen, D.

    1984-01-01

    This paper describes the results of our investigation of two commonly observed modes of failure of Alloy 600 in high temperature caustic environment namely, intergranular stress corrosion cracking (IGSCC) and intergranular attack (IGA). Specimens are studied as C-rings under constant deflection, wires with and without any externally applied load, and as straining electrodes. The potential dependence of average crack propagation rate is established in a single test by using several C-rings held at different potentials, by using a modification of the static potential gradient method of Seys and Van Haute. SCC appears to be governed by a film rupture mechanism and its propagation rate is significantly influenced by the electrochemical potential and associated surface film formation. The maximum crack propagation rate for C-rings and constant load specimens is very similar but much smaller than that calculated for a straining electrode at the same potential. IGA occurs over a wide range of potential - starting from a few tens of millivolts cathodic to the corrosion potential up to the lower end of anodic potentials normally required for SCC. IGA seems to be rather independent of stress and is generally more pronounced in the crevice area under the nuts used in C-rings. Examination of several creviced coupons shows that outside the crevice, enrichment of iron and chromium occurs on the surface as the potential is raised anodically, whereas the Ni:Fe and Ni:Cr ratios remain relatively independent of potential within the crevice.

  7. 1987 EPRI Workshop on Secondary-Side Intergranular Corrosion Mechanisms: Proceedings, Volumes 1 and 2

    SciTech Connect

    1988-09-01

    Participants at a 1987 steam generator corrosion workshop in Alexandria, Virginia, presented 33 papers discussing questions of environment-induced intergranular attack (IGA) and intergranular stress corrosion cracking (IGSCC). Data collected from operating plants and research laboratories demonstrate that IGA/IGSCC occurs in caustic, neutral, and acidic environments.

  8. Reducing the global burden of Preterm Birth through knowledge transfer and exchange: a research agenda for engaging effectively with policymakers.

    PubMed

    Yamey, Gavin; Horváth, Hacsi; Schmidt, Laura; Myers, Janet; Brindis, Claire D

    2016-01-01

    Preterm birth (PTB) is the world's leading cause of death in children under 5 years. In 2013, over one million out of six million child deaths were due to complications of PTB. The rate of decline in child death overall has far outpaced the rate of decline attributable to PTB. Three key reasons for this slow progress in reducing PTB mortality are: (a) the underlying etiology and biological mechanisms remain unknown, presenting a challenge to discovering ways to prevent and treat the condition; (ii) while there are several evidence-based interventions that can reduce the risk of PTB and associated infant mortality, the coverage rates of these interventions in low- and middle-income countries remain very low; and (c) the gap between knowledge and action on PTB--the "know-do gap"--has been a major obstacle to progress in scaling up the use of existing evidence-based child health interventions, including those to prevent and treat PTB.In this review, we focus on the know-do gap in PTB as it applies to policymakers. The evidence-based approaches to narrowing this gap have become known as knowledge transfer and exchange (KTE). In our paper, we propose a research agenda for promoting KTE with policymakers, with an ambitious but realistic goal of reducing the global burden of PTB. We hope that our proposed research agenda stimulates further debate and discussion on research priorities to soon bend the curve of PTB mortality. PMID:26987438

  9. Boric acid application guidelines for intergranular corrosion inhibition

    SciTech Connect

    Piskor, S.R. . Nuclear Services Div.)

    1990-12-01

    A significant fraction of the operating Pressurized Water Reactor steam generators have used or are using boric acid as an inhibitor to control stress corrosion cracking, intergranular attack, or denting. Boric acid is applied on line, or by means of crevice flushing, low power soaks, or a combination of these methods. When boric acid is used, it is important to have knowledge about its chemical and physical properties, its effect on corrosion, and its correct application. The data on these subjects may be found in a diversity of sources, which are often not readily available or convenient to use. In addition, new information has recently become available. This report has been prepared and revised to be comprehensive treatise on boric acid relevant to its application in nuclear steam generators. Relevant boric acid information from 1987--89 has been added to provide the latest available data from laboratory testing and power plant application. 5 figs.

  10. Rotating plasma jets in the photospheric intergranular lanes

    NASA Astrophysics Data System (ADS)

    Lemmerer, Birgit; Hanslmeier, Arnold; Muthsam, Herbert; Piantschitsch, Isabell; Zaqarashvili, Teimuraz

    2016-07-01

    High resolution simulations and observations of the solar photosphere reveal the population of small granular cells with diameters less than 600 km. However, the underlying mechanisms of their generation are still unclear. Simulations show that the majority of small granules may not result from fragmentation of larger granular cells but instead evolve and dissolve in the intergranular lanes. We study the dynamics of these granular cells in high resolution simulations. We found that the small granules show a jet-like behavior with strong horizontal and vertical vortex motions. A newly developed algorithm that tracks the evolution of the 3D plasma cells in the convection zone and lower photosphere shows strong vertical vorticity within the small granular cells. The rotating plasma jets, which are visible as small granules, may generate magnetized vortex flows and torsional Alfvén waves observed at upper layers and hence can play a distinct role in the energy supply to the chromosphere and corona.

  11. Amorphous intergranular phases control the properties of rodent tooth enamel

    NASA Astrophysics Data System (ADS)

    Gordon, Lyle M.; Cohen, Michael J.; MacRenaris, Keith W.; Pasteris, Jill D.; Seda, Takele; Joester, Derk

    2015-02-01

    Dental enamel, a hierarchical material composed primarily of hydroxylapatite nanowires, is susceptible to degradation by plaque biofilm-derived acids. The solubility of enamel strongly depends on the presence of Mg2+, F-, and CO32-. However, determining the distribution of these minor ions is challenging. We show—using atom probe tomography, x-ray absorption spectroscopy, and correlative techniques—that in unpigmented rodent enamel, Mg2+ is predominantly present at grain boundaries as an intergranular phase of Mg-substituted amorphous calcium phosphate (Mg-ACP). In the pigmented enamel, a mixture of ferrihydrite and amorphous iron-calcium phosphate replaces the more soluble Mg-ACP, rendering it both harder and more resistant to acid attack. These results demonstrate the presence of enduring amorphous phases with a dramatic influence on the physical and chemical properties of the mature mineralized tissue.

  12. Intergranular failures of alloy 600 in high temperature caustic environments

    SciTech Connect

    Bandy, R.; van Rooyen, D.; Roberge, R.

    1985-03-01

    This paper describes the results of an investigation of two commonly observed modes of failure of Alloy 600 in high temperature caustic environment, namely, intergranular stress corrosion cracking (IGSCC) and intergranular attack (IGA). Specimens are studied as C-rings under constant deflection, wires with and without any externally applied load, and as straining electrodes. The potential dependence of average crack propagation rate is established in a single test in which several C-rings are held at different potentials by using a modification of the static potential gradient method of Seys and Van Haute. SCC appears to be governed by a film rupture mechanism, and its propagation rate is significantly influenced by the electrochemical potential and associated surface film formation. The maximum crack propagation rate for C-rings and constant load specimens is very similar but much smaller than that calculated for a straining electrode at the same potential. IGA occurs over a wide range of potential, starting from a few multiples of ten millivolts cathodic to the corrosion potential up to the lower end of anodic potentials normally required for SCC. IGA seems to be rather independent of stress and is generally more pronounced in the crevice area under the nuts used in C-rings. Examination of several creviced coupons shows that outside the crevice, enrichment of iron and chromium occurs on the surface as the potential is raised anodically, whereas the Ni:Fe and Ni:Cr ratios remain relatively independent of potential within the crevice. It is believed that a better knowledge of the crevice chemistry and its mass transport characteristics will provide a clue to the origin and extent of IGA.

  13. Reduced-Dimensionality Semiclassical Transition State Theory: Application to Hydrogen Atom Abstraction and Exchange Reactions of Hydrocarbons.

    PubMed

    Greene, Samuel M; Shan, Xiao; Clary, David C

    2015-12-17

    Quantum mechanical methods for calculating rate constants are often intractable for reactions involving many atoms. Semiclassical transition state theory (SCTST) offers computational advantages over these methods but nonetheless scales exponentially with the number of degrees of freedom (DOFs) of the system. Here we present a method with more favorable scaling, reduced-dimensionality SCTST (RD SCTST), that treats only a subset of DOFs of the system explicitly. We apply it to three H abstraction and exchange reactions for which two-dimensional potential energy surfaces (PESs) have previously been constructed and evaluated using RD quantum scattering calculations. We differentiated these PESs to calculate harmonic frequencies and anharmonic constants, which were then used to calculate cumulative reaction probabilities and rate constants by RD SCTST. This method yielded rate constants in good agreement with quantum scattering results. Notably, it performed well for a heavy-light-heavy reaction, even though it does not explicitly account for corner-cutting effects. Recent extensions to SCTST that improve its treatment of deep tunneling were also evaluated within the reduced-dimensionality framework. The success of RD SCTST in this study suggests its potential applicability to larger systems. PMID:26090556

  14. Reduced junctional Na+/Ca2+-exchanger activity contributes to sarcoplasmic reticulum Ca2+ leak in junctophilin-2-deficient mice

    PubMed Central

    Wang, Wei; Landstrom, Andrew P.; Wang, Qiongling; Munro, Michelle L.; Beavers, David; Ackerman, Michael J.; Soeller, Christian

    2014-01-01

    Expression silencing of junctophilin-2 (JPH2) in mouse heart leads to ryanodine receptor type 2 (RyR2)-mediated sarcoplasmic reticulum (SR) Ca2+ leak and rapid development of heart failure. The mechanism and physiological significance of JPH2 in regulating RyR2-mediated SR Ca2+ leak remains elusive. We sought to elucidate the role of JPH2 in regulating RyR2-mediated SR Ca2+ release in the setting of cardiac failure. Cardiac myocytes isolated from tamoxifen-inducible conditional knockdown mice of JPH2 (MCM-shJPH2) were subjected to confocal Ca2+ imaging. MCM-shJPH2 cardiomyocytes exhibited an increased spark frequency width with altered spark morphology, which caused increased SR Ca2+ leakage. Single channel studies identified an increased RyR2 open probability in MCM-shJPH2 mice. The increase in spark frequency and width was observed only in MCM-shJPH2 and not found in mice with increased RyR2 open probability with native JPH2 expression. Na+/Ca2+-exchanger (NCX) activity was reduced by 50% in MCM-shJPH2 with no detectable change in NCX expression. Additionally, 50% inhibition of NCX through Cd2+ administration alone was sufficient to increase spark width in myocytes obtained from wild-type mice. Additionally, superresolution analysis of RyR2 and NCX colocalization showed a reduced overlap between RyR2 and NCX in MCM-shJPH2 mice. In conclusion, decreased JPH2 expression causes increased SR Ca2+ leakage by directly increasing open probability of RyR2 and by indirectly reducing junctional NCX activity through increased dyadic cleft Ca2+. This demonstrates two novel and independent cellular mechanisms by which JPH2 regulates RyR2-mediated SR Ca2+ leak and heart failure development. PMID:25193470

  15. Applicability of the fracture toughness master curve to irradiated highly embrittled steel and intergranular fracture

    SciTech Connect

    Nanstad, Randy K; Sokolov, Mikhail A; McCabe, Donald E

    2008-01-01

    The Heavy-Section Steel Irradiation (HSSI) Program at Oak Ridge National Laboratory has evaluated a submerged-arc (SA) weld irradiated to a high level of embrittlement and a temper embrittled base metal that exhibits significant intergranular fracture (IGF) relative to representation by the Master Curve. The temper embrittled steel revealed that the intergranular mechanism significantly extended the transition temperature range up to 150 C above To. For the irradiated highly embrittled SA weld study, a total of 21 1T compact specimens were tested at five different temperatures and showed the Master Curve to be nonconservative relative to the results, although that observation is uncertain due to evidence of intergranular fracture.

  16. Does amifostine reduce metabolic rate? Effect of the drug on gas exchange and acute ventilatory hypoxic response in humans.

    PubMed

    Pandit, Jaideep J; Allen, Caroline; Little, Evelyn; Formenti, Federico; Harris, Adrian L; Robbins, Peter A

    2015-01-01

    Amifostine is added to chemoradiation regimens in the treatment of many cancers on the basis that, by reducing the metabolic rate, it protects normal cells from toxic effects of therapy. We tested this hypothesis by measuring the metabolic rate (by gas exchange) over 255 min in 6 healthy subjects, at two doses (500 mg and 1000 mg) of amifostine infused over 15 min at the start of the protocol. We also assessed the ventilatory response to six 1 min exposures to isocapnic hypoxia mid-protocol. There was no change in metabolic rate with amifostine as measured by oxygen uptake (p = 0.113). However in carbon dioxide output and respiratory quotient, we detected a small decline over time in control and drug protocols, consistent with a gradual change from carbohydrate to fat metabolism over the course of the relatively long study protocol. A novel result was that amifostine (1000 mg) increased the mean ± SD acute hypoxic ventilatory response from 12.4 ± 5.1 L/min to 20.3 ± 11.9 L/min (p = 0.045). In conclusion, any cellular protective effects of amifostine are unlikely due to metabolic effects. The stimulatory effect on hypoxic ventilatory responses may be due to increased levels of hypoxia inducible factor, either peripherally in the carotid body, or centrally in the brain. PMID:25894815

  17. Intergranular stresses in Zircaloy-2 with rod texture

    SciTech Connect

    Pang, J.W.L.; Mason, T.E.; Holden, T.M.; Turner, P.A.

    1999-01-15

    The intergranular strains in thermally and mechanically anisotropic Zircaloy-2 with rod texture have been measured in situ under uniaxial tension along the rod axis by neutron diffraction. An in-plane biaxial stress state was developed in the grains as deformation proceeded. The tensors describing the stress state of the grains throughout the deformation process have been determined experimentally in the natural crystallographic axes system. After 5% deformation, the stress tensor components of the grains, {sigma}{sub 11} and {sigma}{sub 33}--stresses acting along the {l_angle}a{r_angle}-axes and {l_angle}c{r_angle}-axes lying in the transverse plane--are 230 {+-} 20 MPa and {minus}241 {+-} 21 MPa, respectively. The angular dependence of the initial thermal residual stress state and the final deformed state have also been obtained. The elasto-plastic self-confident model has been used to simulate the experiments and exhibits agreement with experiment. It appears that the introduction of basal slip {l_brace}0001{r_brace}{l_angle}1{bar 2}10{r_angle} considerably improves the agreement with experiment.

  18. Ultrasonic inspection reliability for intergranular stress corrosion cracks

    SciTech Connect

    Heasler, P G; Taylor, T T; Spanner, J C; Doctor, S R; Deffenbaugh, J D

    1990-07-01

    A pipe inspection round robin entitled Mini-Round Robin'' was conducted at Pacific Northwest Laboratory from May 1985 through October 1985. The research was sponsored by the US Nuclear Regulatory Commission, Office of Nuclear Regulatory Research under a program entitled Evaluation and Improvement of NDE Reliability for Inservice Inspection of Light Water Reactors.'' The Mini-Round Robin (MRR) measured the intergranular stress corrosion (GSC) crack detection and sizing capabilities of inservice inspection (ISI) inspectors that had passed the requirements of IEB 83-02 and the Electric Power Research Institute (EPRI) sizing training course. The MRR data base was compared with an earlier Pipe Inspection Round Robin (PIRR) that had measured the performance of inservice inspection prior to 1982. Comparison of the MRR and PIRR data bases indicates no significant change in the inspection capability for detecting IGSCC. Also, when comparing detection of long and short cracks, no difference in detection capability was measured. An improvement in the ability to differentiate between shallow and deeper IGSCC was found when the MRR sizing capability was compared with an earlier sizing round robin conducted by the EPRI. In addition to the pipe inspection round robin, a human factors study was conducted in conjunction with the Mini-Round Robin. The most important result of the human factors study is that the Relative Operating Characteristics (ROC) curves provide a better methodology for describing inspector performance than only probability of detection (POD) or single-point crack/no crack data. 6 refs., 55 figs., 18 tabs.

  19. A probabilistic model of intergranular stress corrosion cracking

    SciTech Connect

    Bourcier, R.J.; Jones, W.B. ); Scully, J.R. )

    1991-01-01

    We have developed a model which utilizes a probabilistic failure criterion to describe intergranular stress corrosion cracking (IGSCC). A two-dimensional array of elements representing a section of a pipe wall is analyzed, with each element in the array representing a segment of grain boundary. The failure criterion is applied repetitively to each element of the array that is exposed to the interior of the pipe (i.e. the corrosive fluid) until that element dissolves, thereby exposing the next element. A number of environmental, mechanical, and materials factors have been incorporated into the model, including: (1) the macroscopic applied stress profile, (2) the stress history, (3) the extent and grain-to- grain distribution of carbide sensitization levels, which can be applied to a subset of elements comprising a grain boundary, and (4) a data set containing IGSCC crack growth rates as function of applied stress intensity and sensitization level averaged over a large population of grains. The latter information was obtained from the literature for AISI 304 stainless steel under light water nuclear reactor primary coolant environmental conditions. The resulting crack growth simulations are presented and discussed. 14 refs., 10 figs.

  20. Intergranular fracture in some precipitation-hardened aluminum alloys at low temperatures

    SciTech Connect

    Kuramoto, S.; Itoh, G.; Kanno, M.

    1996-10-01

    Intergranular fracture at low temperatures from room temperature down to 4.2 K has been studied in some precipitation-hardened aluminum alloys. Microscopic appearance of intergranular facets is revealed to be greatly affected by the microstructure adjacent to the grain boundaries (GBs). When large precipitates on GBs and wide precipitation-free zones (PFZs) are present, coalescence of microvoids initiated at the GB precipitates causes the intergranular fracture with dimples. This fracture process is found to be unaffected by deformation temperature. On the other hand, in the presence of fine precipitates on GBs and narrow PFZs, matrix slip localization exerts significant influence on the fracture behavior. At low temperatures, large stress concentration at GBs leads to intergranular fracture, forming sharp ledges on the fracture surfaces, while at room temperature, the dynamic recovery process is thought to relax such stress concentration, resulting in a transgranular ductile rupture.

  1. Study on Laser-Assisted Rejuvenation of Inter-Granular Corrosion Damaged Type 304 Stainless Steel

    NASA Astrophysics Data System (ADS)

    Gupta, R. K.; Bhardwaj, V. K.; Agrawal, D. K.; Kumar, Manoj; Upadhyay, B. N.; Sankar, P. Ram; Ganesh, P.; Kaul, R.; Oak, S. M.; Kukreja, L. M.

    2015-09-01

    The paper evaluates laser surface melting treatment for rejuvenation of inter-granular corrosion damaged type 304 stainless steel. Surface melting of inter-granular corrosion damaged specimens with CW CO2 and pulsed Nd:YAG lasers was quite effective in sealing surface damage. However, inter-granular corrosion susceptibility of laser-rejuvenated surface was strongly influenced by associated thermal exposure. With respect to CW CO2 laser, pulsed Nd:YAG laser-rejuvenated surface demonstrated significantly suppressed micro-structural damage and IGC-susceptibility. Compact pulsed Nd:YAG laser, with flexible beam transportation, presents an effective tool for in-situ rejuvenation of inter-granular corrosion damaged in-service stainless steel components operating in susceptible environments.

  2. MESO-SCALE MODELING OF THE INFLUENCE OF INTERGRANULAR GAS BUBBLES ON EFFECTIVE THERMAL CONDUCTIVITY

    SciTech Connect

    Paul C. Millett; Michael Tonks

    2011-06-01

    Using a mesoscale modeling approach, we have investigated how intergranular fission gas bubbles, as observed in high-burnup nuclear fuel, modify the effective thermal conductivity in a polycrystalline material. The calculations reveal that intergranular porosity has a significantly higher resistance to heat transfer compared to randomly-distributed porosity. A model is developed to describe this conductivity reduction that considers an effective grain boundary Kapitza resistance as a function of the fractional coverage of grain boundaries by bubbles.

  3. The Galim LL/EH Polymict Breccia: Evidence for Impact-Induced Exchange Between Reduced and Oxidized Meteoritic Material

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    1997-01-01

    Galim is a polymict breccia consisting of a heavily shocked (shock stage S6) LL6 chondrite, Galim (a), and an impact-melted EH chondrite, Galim (b). Relict chondrules in Galim (b) served as nucleation sites for euhedral enstatite grains crystallizing from the impact melt. Many of the reduced phases typical of EH chondrites (e.g., Si-bearing metallic Fe-Ni; Ti-bearing troilite) are absent. Galim (b) was probably shock-melted while in contact with a more oxidized source, namely, Galim (a); during this event, Si was oxidized from the metal and Ti was oxidized from troilite. Galim (a) contains shock veins and recrystallized, unzoned olivine. The absence of evidence for reduction in Galim (a) may indicate that the amount of LL material greatly exceeded that of EH material; shock metamorphism may have taken place on the LL parent body. Shock-induced redox reactions such as those inferred for the Galim breccia appear to be restricted mainly to asteroids because the low-end tail of their relative-velocity distribution permits mixing of intact disparate materials (including accretion of projectiles of different oxidation states), whereas the peak of the distribution leads to high equilibration shock pressures (allowing impact-induced exchange between previously accreted, disequilibrated materials). Galim probably formed by a two-stage process: (I) accretion to the LL parent body of an intact EH projectile at low relative velocities, and (2) shock metamorphism of the assemblage by the subsequent impact of another projectile at significantly higher relative velocities.

  4. Reducing uncertainty in model estimates of North American polar net ecosystem exchange by including remote sensing observations of snow cover

    NASA Astrophysics Data System (ADS)

    Luus, K. A.; Lin, J. C.; Kelly, R. E.

    2012-12-01

    Uncertainty exists in high-latitude estimates of net ecosystem exchange (NEE) due to a variety of factors such as a limited number of high-latitude eddy covariance stations, and challenges in remote sensing of polar CO2 concentrations and land surface properties. Furthermore, although in situ studies have indicated that a substantial portion of annual NEE in polar regions occurs during the snow season, and that the timing and magnitude of photosynthesis and subnivean respiration are influenced by snow cover, previous estimates of NEE have not explicitly represented snow properties. The objective of this study was to examine the uncertainty in simulated estimates of NEE from the Vegetation Photosynthesis and Respiration Model (VPRM) by contrasting values generated with, versus without, an explicit representation of snow cover. VPRM is a biospheric carbon flux model that generates high resolution estimates of NEE from remote sensing observations of temperature, shortwave radiation and a vegetation index (NDVI) using a simple mathematical structure with only four parameters per vegetation class. In the standard VPRM formulation, photosynthesis is limited during the cold season by low air temperatures, diminished shortwave radiation and low NDVI values. Respiration is assumed to be constant below a threshold air temperature and is otherwise calculated as a linear function of air temperature. In this study, MODIS observations of fractional snow cover were incorporated into VPRM in order to represent the influence of snow cover on suppressing photosynthetic uptake by vegetation and allowing subnivean respiration to persist at cold air temperatures by insulating the soil from heat loss. Photosynthesis was first calculated using the standard VPRM formulation, and the rate of photosynthesis was then reduced according to the fractional snow cover such that the rate of photosynthesis on an 80% snow covered pixel would be reduced by 80%. When a pixel's snow cover area was

  5. Correlation of texture and intergranular corrosion in Al-Mg 5xxx series alloys

    NASA Astrophysics Data System (ADS)

    Engler, O.; Hentschel, T.; Brinkman, H.-J.

    2015-04-01

    Aluminium-alloys of the AA 5xxx series with Mg contents in excess of 3% may suffer from intergranular corrosion (IGC) when exposed to temperatures in the range 60 to 200°C. At these temperatures Al-Mg alloys are rendered susceptible to IGC by precipitation of β-Al8Mg5 phases along the grain boundaries. Accordingly, susceptibility to IGC will depend on grain size as well as type and orientation of the grain boundaries present in the material, that is, on the crystallographic texture of the material at final gauge. Therefore, it is of great interest to study the correlation of texture and precipitation of β-AlMg phases and, therewith, susceptibility to IGC. For this purpose, different AA 5182 samples were processed so as to produce different crystallographic textures and characterized with respect to microstructure and resistance against IGC. EBSD local texture analysis was applied to provide information about the grain boundary character distribution. Eventually, this may enable Al industry to reduce the susceptibility of Al-Mg alloys to IGC by proper control of the final gauge texture, such that higher Mg-contents may be used in IGC-critical applications.

  6. Intergranular fracture in irradiated Inconel X-750 containing very high concentrations of helium and hydrogen

    NASA Astrophysics Data System (ADS)

    Judge, Colin D.; Gauquelin, Nicolas; Walters, Lori; Wright, Mike; Cole, James I.; Madden, James; Botton, Gianluigi A.; Griffiths, Malcolm

    2015-02-01

    In recent years, it has been observed that Inconel X-750 spacers in CANDU reactors exhibits lower ductility with reduced load carrying capacity following irradiation in a reactor environment. The fracture behaviour of ex-service material was also found to be entirely intergranular at high doses. The thermalized flux spectrum in a CANDU reactor leads to transmutation of 58Ni to 59Ni. The 59Ni itself has unusually high thermal neutron reaction cross-sections of the type: (n, γ), (n, p), and (n, α). The latter two reactions, in particular, contribute to a significant enhancement of the atomic displacements in addition to creating high concentrations of hydrogen and helium within the material. Microstructural examinations by transmission electron microscopy (TEM) have confirmed the presence of helium bubbles in the matrix and aligned along grain boundaries and matrix-precipitate interfaces. Helium bubble size and density are found to be highly dependent on the irradiation temperature and material microstructure; the bubbles are larger within grain boundary precipitates. TEM specimens extracted from fracture surfaces and crack tips provide information that is consistent with crack propagation along grain boundaries due to the presence of He bubbles.

  7. NDI method to locate intergranular corrosion around fastener holes in aluminum wing skins

    NASA Astrophysics Data System (ADS)

    Rutherford, Paul S.

    1998-03-01

    Contact between galvanically dissimilar metals, such as cadmium plated steel fasteners and aluminum wing skins are known to be a source of corrosion. There is a design requirement to fill the void between the contacting surfaces of steel fasteners with a wet sealant. However, if the contacting surface is damaged or a void exists between the fastener head and the aluminum skin, moisture can collect and intergranular corrosion may occur along aluminum grain boundaries, which run parallel to the surface of the wing skin. If intergranular corrosion is allowed to propagate, delamination of the thin layers of aluminum, known as exfoliation corrosion will occur. When this intergranular corrosion reaches an exfoliated state, extensive rework is involved in removing the corrosion. This paper discusses the results of a USAF E-3A Engineering Service Task 89-E3B3-16 to develop a nondestructive inspection procedure to detect intergranular corrosion in an incipient state before it reaches exfoliation. Eddy current and ultrasonic inspection techniques were evaluated. A novel ultrasonic pulse echo technique was developed which utilizes a focus transducer with a hand held fixture. Inspections were performed on test parts which were removed from the upper wing skin of a retired 707 which had varying degrees of intergranular and exfoliation corrosion. Inspection results are compared to the results from the mechanical rework of the wing skin and dissection of a wing skin fastener hole.

  8. Aluminum-containing intergranular phases in hot-pressed silicon carbide

    SciTech Connect

    Zhang, Xiao Feng; De Jonghe, Lutgard C.

    2003-01-12

    Aluminum-containing intergranular phases, forming intergranular films and secondary phase particles at triple-junctions in SiC hot-pressed with aluminum, boron, and carbon additions, were studied by transmission electron microscopy. Statistical high-resolution electron microscopy study of intergranular films indicated that a large fraction of the vitreous intergranular films in the s-hot-pressed SiC crystallized during postannealing in argon above 1000 C. However, brief heating to 1900 C indeed re-melted 25 percent of the crystallized intergranular films. The structural transitions were reflected in the statistical width distributions of the amorphous grain boundary layers. At triple-junctions, Al2O3, Al2OC-SiC solid solution, and mullite phases were newly identified. These phases,together with others reported before are represented in a quaternary phase diagram for 1900 C. It is proposed that a SiC-Al2OC liquid domain is to be included in this phase diagram.

  9. Control of cryogenic intergranular fracture in high-manganese austenitic steels

    SciTech Connect

    Strum, M.J.

    1986-12-01

    The sources of cryogenic intergranular embrittlement in high-Mn austenitic steels and the conditions necessary for its control are examined. It is shown that the high-Mn alloys are inherently susceptible to intergranular embrittlement due to both their low grain boundary cohesion and heterogeneous deformation characteristics. Extrinsic sources of embrittlement which could account for the transition behavior are not observed. An Auger electron spectroscopy (AES) study shows no indication of impurity-segregation-induced embrittlement. No grain boundary precipitation is observed, and austenite stabilization does not ensure ductile fracture. The influence of chemistry modifications on the ductile-to-brittle transition behavior were also examined through additions of N, Cr, and C to binary Fe-31 Mn. Nitrogen additions increase the 77K yield strength at a rate of 2200 MPa per weight percent N, and increase the austenite stability, but also increase the susceptibility of ternary alloys to intergranular fracture. Quaternary Cr additions are effective in increasing the N solubility, and lower the transition temperature. Carbon additions result in complete suppression of intergranular fracture at 77K. Qualitatively significant changes in the deformation heterogeneity with chemistry modifications are not observed. The temper-toughening of Fe-Mn-Cr-N alloys is associated with the grain boundary segregation of boron and the redistribution of N. Both boron and carbon are expected to inhibit intergranular fracture through increases in grain boundary cohesion.

  10. Reducing Intimate and Paying Partner Violence against Women Who Exchange Sex in Mongolia: Results from a Randomized Clinical Trial

    ERIC Educational Resources Information Center

    Carlson, Catherine E.; Chen, Jiehua; Chang, Mingway; Batsukh, Altantsetseg; Toivgoo, Aira; Riedel, Marion; Witte, Susan S.

    2012-01-01

    Women who exchange sex for money or other goods, that is, female sex workers, are at increased risk of experiencing physical and sexual violence from both paying and intimate partners. Exposure to violence can be exacerbated by alcohol use and HIV/STI risk. The purpose of this study is to examine the efficacy of a HIV/STI risk reduction and…

  11. Core-shell self-assembly triggered via a thiol-disulfide exchange reaction for reduced glutathione detection and single cells monitoring.

    PubMed

    Zhang, Zhen; Jiao, Yuting; Wang, Yuanyuan; Zhang, Shusheng

    2016-01-01

    A novel core-shell DNA self-assembly catalyzed by thiol-disulfide exchange reactions was proposed, which could realize GSH-initiated hybridization chain reaction (HCR) for signal amplification and molecules gathering. Significantly, these self-assembled products via electrostatic interaction could accumulate into prominent and clustered fluorescence-bright spots in single cancer cells for reduced glutathione monitoring, which will effectively drive cell monitoring into a new era. PMID:27412605

  12. Core-shell self-assembly triggered via a thiol-disulfide exchange reaction for reduced glutathione detection and single cells monitoring

    PubMed Central

    Zhang, Zhen; Jiao, Yuting; Wang, Yuanyuan; Zhang, Shusheng

    2016-01-01

    A novel core-shell DNA self-assembly catalyzed by thiol-disulfide exchange reactions was proposed, which could realize GSH-initiated hybridization chain reaction (HCR) for signal amplification and molecules gathering. Significantly, these self-assembled products via electrostatic interaction could accumulate into prominent and clustered fluorescence-bright spots in single cancer cells for reduced glutathione monitoring, which will effectively drive cell monitoring into a new era. PMID:27412605

  13. Creep and intergranular cracking of Ni-Cr-Fe-C in 360[degree]C argon

    SciTech Connect

    Angeliu, T.M. ); Was, G.S. )

    1994-06-01

    The influence of carbon and chromium on the creep and intergranular (IG) cracking behavior of controlled-purity Ni-xCr-9Fe-yC alloys in 360 C argon was investigated using constant extension rate tension (CERT) and constant load tension (CLT) testing. The CERT test results at 360 C show that the degree of IG cracking increases with decreasing bulk chromium or carbon content. The CLT test results at 360 C and 430 C reveal that, as the amounts of chromium and carbon in solution decrease, the steady-state creep rate increases. The occurrence of severe IG cracking correlates with a high steady-state creep rate, suggesting that creep plays a role in the IG cracking behavior in argon at 360 C. The failure mode of IG cracking and the deformation mode of creep are coupled through the formation of grain boundary voids that interlink to form grain boundary cavities, resulting in eventual failure by IG cavitation and ductile overload of the remaining ligaments. Grain boundary sliding may be enhancing grain boundary cavitation by redistributing the stress from inclined to more perpendicular boundaries and concentrating stress at discontinuities for the boundaries oriented 45 deg with respect to the tensile axis. Additions of carbon or chromium, which reduce the creep rate over all stress levels, also reduce the amount of IG fracture in CERT experiments. A damage accumulation model was formulated and applied to CERT tests to determine whether creep damage during a CERT test controls failure. Results show that, while creep plays a significant role in CERT experiments, failure is likely controlled by ductile overload caused by reduction in area resulting from grain boundary void formation and interlinkage.

  14. Intergranular corrosion of Type 409 stainless steel used in automotive exhaust applications

    SciTech Connect

    Brossia, C.S.; Martin, K.L.

    1998-12-31

    Automotive exhaust systems must meet increasingly stringent lifetime requirements, and thus the incorporation of stainless steels (primarily ferritic) has increased. One of the failure mechanisms that is rarely encountered, but does occur, is intergranular corrosion. Intergranular corrosion of ferritic stainless steels is believed to occur via a similar mechanism as is observed in austenitic stainless, namely precipitation of chromium-carbon nitride (Cr-C/N) particles at the grain boundaries leading to Cr-depleted regions. In the present study, the effect of thermal history (including heat treatment, welding and post-weld heat treatment) and alloy chemistry on the level of sensitization of Type 409SS were examined.

  15. STUDY OF GRAIN BOUNDARY CHARACTER ALONG INTERGRANULAR STRESS CORROSION CRACK PATHS IN AUSTENITIC ALLOYS

    SciTech Connect

    Guertsman, Valery Y.; Bruemmer, Stephen M.

    2001-05-25

    Samples of austenitic stainless alloys were examined by means of scanning and transmission electron microscopy. Misorientations were measured by electron backscattered diffraction. Grain boundary distributions were analyzed with special emphasis on the grain boundary character along intergranular stress-corrosion cracks and at crack arrest points. It was established that only coherent twin S3 boundaries could be considered as "special" ones with regard to crack resistance. However, it is possible that twin interactions with random grain boundaries may inhibit crack propagation. The results suggest that other factors besides geometrical ones play an important role in the intergranular stress-corrosion cracking of commercial alloys.

  16. An evaluation of multiple-schedule variations to reduce high-rate requests in the picture exchange communication system.

    PubMed

    Landa, Robin; Hanley, Gregory P

    2016-06-01

    Using procedures similar to those of Tiger, Hanley, and Heal (2006), we compared two multiple-schedule variations (S+/S- and S+ only) to treat high-rate requests for edible items in the Picture Exchange Communication System (PECS). Two individuals with autism participated, after they showed persistent requests for edible items after PECS training. Stimulus control was achieved only with the multiple schedule that involved presentation of a discriminative stimulus during reinforcement components and its removal during extinction components (S+ only). Discriminated requests were maintained for the 1 participant who experienced schedule thinning. PMID:26814152

  17. Double coating protection of Nd-Fe-B magnets: Intergranular phosphating treatment and copper plating

    NASA Astrophysics Data System (ADS)

    Zheng, Jingwu; Chen, Haibo; Qiao, Liang; Lin, Min; Jiang, Liqiang; Che, Shenglei; Hu, Yangwu

    2014-12-01

    In this work, a double coating protection technique of phosphating treatment and copper plating was made to improve the corrosion resistance of sintered Nd-Fe-B magnets. In other words, the intergranular region of sintered Nd-Fe-B is allowed to generate passive phosphate conversion coating through phosphating treatment, followed by the copper coating on the surface of sintered Nd-Fe-B. The morphology and corrosion resistance of the phosphated sintered Nd-Fe-B were observed using SEM and electrochemical method respectively. The phosphate conversion coating was formed more preferably on the intergranular region of sintered Nd-Fe-B than on the main crystal region; just after a short time of phosphating treatment, the intergranular region of sintered Nd-Fe-B has been covered by the phosphate conversion coating and the corrosion resistance is significantly improved. With the synergistic protection of the intergranular phosphorization and the followed copper electrodeposition, the corrosion resistance of the sintered Nd-Fe-B is significantly better than that with a single phosphate film or single plating protection.

  18. Proceedings: 1985 EPRI Workshop on Remedial Actions for Secondary-Side Intergranular Corrosion

    SciTech Connect

    1986-12-01

    During 1984 and 1985, several EPRI projects provided data showing that remedial actions can retard or stop intergranular corrosion and stress corrosion cracking in PWR steam generators. These remedies change either crevice-fluid pH, crevice-fluid concentration, or oxide-film composition on structural alloys.

  19. Effect of Se partial pressure on intergranular embrittlement of a Pt-Rh-W alloy

    SciTech Connect

    White, C.L.; Keiser, J.R.; Heatherly, L.; Newsome, J.F.

    1981-07-01

    This note presents additional experimental results concerning the effect of P/sub Se/ on the degree of intergranular embrittlement and the extent of Se contamination at Pt +30 wt % Rh +8 wt % W Alloy (Pt-3008) grain boundaries. 8 refs.

  20. Effect of boric acid on intergranular corrosion and on hideout return efficiency of sodium in the tube support plate crevices

    SciTech Connect

    Paine, J.P.N.; Shoemaker, C.E.; Campan, J.L.; Brunet, J.P.; Schindler, P.; Stutzmann, A.

    1995-12-31

    Sodium hydroxide is one of the main causes of intergranular attack/stress corrosion cracking (IGA/SCC) of alloy 600 steam generator (S.G.) tubes. Boric acid appears to be one of the possible remedies for intergranular corrosion process inhibition. In order to obtain data on boric acid injection efficiency, an experimental program was performed on previously corroded tubes. To prevent premature tube wall cracking, samples were sleeved on alloy 690 tubes. The objective of the tests was to evaluate, on a statistically valid number of samples, the effectiveness of boric acid and tube sleeving as possible remedies for IGA/SCC extension. Another independent experimental program was initiated to determine the hideout return efficiency in the tube support plate (TSP) and tubesheet (TS) crevices after a significant duration ({<=} 180 hours) of sodium hideout. The main objective of the first tests being a statistical evaluation of the efficiency of boric acid treatment, was not achieved. The tests did demonstrate that sleeving effectively reduces IGA/SCC growth. In an additional program, cracks were obtained on highly susceptible tubes when specimens were not sleeved. The companion tests performed in the same conditions but with an addition of boric acid did not show any IGA or cracks. These results seem to demonstrate the possible effect of boric acid in preventing the corrosion process. Results of the second tests did not demonstrate any difference in the amount of sodium piled up in the crevices before and after boric acid injection. They however showed an increase of the hideout return efficiency at the tube support plate level from 78 % without boric acid to 95 % when boric acid is present in the feed water.

  1. Three dimensional calculations of the effective Kapitza resistance of UO2 grain boundaries containing intergranular bubbles

    NASA Astrophysics Data System (ADS)

    Millett, Paul C.; Tonks, Michael R.; Chockalingam, K.; Zhang, Yongfeng; Biner, S. B.

    2013-08-01

    A parametric study has been performed that quantifies the effective change in grain boundary Kapitza resistance due to the presence of intergranular bubbles. The steady-state heat conduction equation was solved in three-dimensional space using INL's MOOSE finite element software, with which spacial mesh adaptivity was used to resolve interfacial widths down to several nanometers while investigating bubble sizes up to a micrometer. Three critical parameters were systematically varied: the intergranular bubble radius, the fractional grain boundary bubble coverage, and the Kapitza resistance of the intact grain boundary. Using the simulation results, a mathematical model dependent on each of these parameters was developed to describe the effective Kapitza resistance. Furthermore, we illustrate how this model can be implemented in a fuel performance code to predict the temperature profile of a cylindrical fuel pellet.

  2. Intergranular Strain Evolution in Titanium During Tensile Loading: Neutron Diffraction and Polycrystalline Model

    NASA Astrophysics Data System (ADS)

    Gloaguen, David; Oum, Guy; Legrand, Vincent; Fajoui, Jamal; Moya, Marie-José; Pirling, Thilo; Kockelmann, Winfried

    2015-11-01

    Intergranular strains due to tensile plastic deformation were investigated in a commercially pure Ti. Neutron diffraction has been used to characterize the evolution of residual elastic strain in grains with different crystallographic orientations. Experimental data have been obtained for the macroscopic stress-strain curve and the intergranular strain evolution in the longitudinal and transverse direction relative to the uniaxial loading axis. The elasto-plastic self-consistent (EPSC) approach was used to model the deformation behavior of the studied material. Comparison between the neutron measurements and the model predictions shows that in most cases the EPSC approach can predict the lattice strain evolution and capture the plastic anisotropy observed in the experiments.

  3. Influence of grain boundaries misorientation angle on intergranular corrosion in 2024-T3 aluminium

    NASA Astrophysics Data System (ADS)

    Bałkowiec, A.; Michalski, J.; Matysiak, H.; Kurzydlowski, K. J.

    2011-12-01

    The special attention has been paid to the influence of misorientation angle of a random grain boundary (GB) on susceptibility to intergranular attack. The detailed observations of the microstructure of the intergranular corrosion (IGC) in 2024-T3 aluminium alloy (AA2024-T3) subjected to galvanic corrosion tests in two different solutions containing chloride ions (0.1 M and 0.5 M NaCl) were carried out using Scanning Electron Microscopy (SEM). The Electron Backscattered Diffraction (EBSD) technique was used to determine the grain boundary character distribution (GBCD) in the initial sample and a GBCD of corroded grain boundaries on a sample subjected to the corrosion test. The results are discussed in terms of the influence of the misorientation angle on the susceptibility of the grain boundaries to corrosion.

  4. Investigation of intergranular stress corrosion cracking in the fuel pool at Three Mile Island Unit 1

    SciTech Connect

    Czajkowski, C.J.

    1985-01-01

    An intergranular stress corrosion cracking failure of 304 stainless steel pipe in 2000 ppM B as H/sub 3/BO/sub 3/ + H/sub 2/O at 100/sup 0/C has been investigated. Constant extension rate testing has produced an intergranular type failure in material in air. Chemical analysis was performed on both the base metal and weld material, in addition to fractography, EPR testing and optical microscopy in discerning the mode of failure. Various effects of Cl/sup -/, O/sub 2/, and MnS are discussed. The results have indicated that the cause of failure was the severe sensitization coupled with probable contamination by S and possibly by Cl ions.

  5. Multi-scale modeling of inter-granular fracture in UO2

    SciTech Connect

    Chakraborty, Pritam; Zhang, Yongfeng; Tonks, Michael R.; Biner, S. Bulent

    2015-03-01

    A hierarchical multi-scale approach is pursued in this work to investigate the influence of porosity, pore and grain size on the intergranular brittle fracture in UO2. In this approach, molecular dynamics simulations are performed to obtain the fracture properties for different grain boundary types. A phase-field model is then utilized to perform intergranular fracture simulations of representative microstructures with different porosities, pore and grain sizes. In these simulations the grain boundary fracture properties obtained from molecular dynamics simulations are used. The responses from the phase-field fracture simulations are then fitted with a stress-based brittle fracture model usable at the engineering scale. This approach encapsulates three different length and time scales, and allows the development of microstructurally informed engineering scale model from properties evaluated at the atomistic scale.

  6. Aqueous sodium chloride induced intergranular corrosion of Al-Li-Cu alloys

    NASA Technical Reports Server (NTRS)

    Pizzo, P. P.; Daeschner, D. L.

    1986-01-01

    Two methods have been explored to assess the susceptibility of Al-Li-Cu alloys to intergranular corrosion in aqueous sodium chloride solution. They are: (1) constant extension rate testing with and without alternate-immersion preexposure and (2) metallographic examination after exposure to a NaCl-H2O2 corrosive solution per Mil-H-6088F. Intergranular corrosion was found to occur in both powder and ingot metallurgy alloys of similar composition, using both methods. Underaging rendered the alloys most susceptible. The results correlate to stress-corrosion data generated in conventional time-to-failure and crack growth-rate tests. Alternate-immersion preexposure may be a reliable means to assess stress corrosion susceptibility of Al-Li-Cu alloys.

  7. Complex nonlinear deformation of nanometer intergranular glassy films in beta-Si3N4.

    PubMed

    Chen, Jun; Ouyang, Lizhi; Rulis, Paul; Misra, Anil; Ching, W Y

    2005-12-16

    The mechanical properties of a model of Y-doped intergranular glassy film in silicon nitride ceramics are studied by large-scale ab initio modeling. By linking directly to its electronic structure, it is shown that this microstructure has a complex nonlinear deformation under stress and Y doping significantly enhances the mechanical properties. The calculation of the electrostatic potential across the film supports the space charge model in ceramic microstructures. PMID:16384476

  8. Intergranular corrosion in AA5XXX aluminum alloys with discontinuous precipitation at the grain boundaries

    NASA Astrophysics Data System (ADS)

    Bumiller, Elissa

    The US Navy currently uses AA5xxx aluminum alloys for structures exposed to a marine environment. These alloys demonstrate excellent corrosion resistance over other aluminum alloys (e.g., AA2xxx or AA7xxx) in this environment, filling a niche in the marine structures market when requiring a light-weight alternative to steel. However, these alloys are susceptible to localized corrosion; more specifically, intergranular corrosion (IGC) is of concern. IGC of AA5xxx alloys due to the precipitation of beta phase on the grain boundaries is a well-established phenomenon referred to as sensitization. At high degrees of sensitization, the IGC path is a continuous anodic path of beta phase particles. At lower degrees of sensitization, the beta phase coverage at the grain boundaries is not continuous. The traditional ranges of susceptibility to IGC as defined by ASTM B928 are in question due to recent studies. These studies showed that even at mid range degrees of sensitization where the beta phase is no longer continuous, IGC may still occur. Previous thoughts on IGC of these alloy systems were founded on the idea that once the grain boundary precipitate became discontinuous the susceptibility to IGC was greatly reduced. Additionally, IGC susceptibility has been defined metallurgically by compositional gradients at the grain boundaries. However, AA5xxx alloys show no compositional gradients at the grain boundaries, yet are still susceptible to IGC. The goal of this work is to establish criteria necessary for IGC to occur given no continuous beta phase path and no compositional gradient at the grain boundaries. IGC performance of the bulk alloy system AA5083 has been studied along with the primary phases present in the IGC system: alpha and beta phases using electrochemistry and modeling as the primary tools. Numerical modeling supports that at steady-state the fissure tip is likely saturated with Mg in excess of the 4% dissolved in the matrix. By combining these results

  9. Proceedings: 1983 Workshop on Secondary-Side Stress Corrosion Cracking and Intergranular Corrosion of PWR Steam Generator Tubing

    SciTech Connect

    1986-03-01

    Participants in this international workshop discussed research investigating mechanisms and propagation rates of intergranular corrosion in PWR steam generators. Laboratory test results, which have been consistent with power plant experience, permitted preliminary definition of corrosion rates in alloy 600 tubing.

  10. The effect of residuals on the presence of intergranular surface cracks on continuously cast billets

    SciTech Connect

    Wijngaarden, M.J.U.T. van; Visagie, G.P.

    1996-12-31

    During 1991, Iscor Vereeniging experienced a dramatic increase in the rejection rate of specialty steel bars rolled from continuously cast billets due to the presence of seams on the bars. The seams originated from tearing of the billets during the first 2 passes in the roughing mill during hot rolling. The defective billets were found to contain fine intergranular cracks on the surface. Such cracks have been described in the literature and have been attributed to the presence of high levels of residuals resulting in the well-known phenomenon of surface hot shortness which results from the enrichment of residuals at the grain boundaries after preferential oxidation of iron during scaling of the steel. The present investigation revealed that the effect of residuals on intergranular surface cracking is a complex interaction between steel composition and casting conditions such as casting speed, intensity of secondary cooling, section size, and mold type. This paper quantifies the effect of residuals on the intergranular surface cracking of continuously cast billets and quantitatively relates the incidence of these cracks to parameters which can be controlled during steelmaking and continuous casting.

  11. Molecular dynamics simulations of intergranular fracture in UO2 with nine empirical interatomic potentials

    SciTech Connect

    Yongfeng Zhang; Paul C Millett; Michael R Tonks; Xian-Ming Bai; S Bulent Biner

    2014-09-01

    The intergranular fracture behavior of UO2 was studied using molecular dynamics simulations with a bicrystal model. The anisotropic fracture behavior due to the different grain boundary characters was investigated with the View the MathML source symmetrical tilt S5 and the View the MathML source symmetrical tilt S3 ({1 1 1} twin) grain boundaries. Nine interatomic potentials, seven rigid-ion plus two core–shell ones, were utilized to elucidate possible potential dependence. Initiating from a notch, crack propagation along grain boundaries was observed for most potentials. The S3 boundary was found to be more prone to fracture than the S5 one, indicated by a lower energy release rate associated with the former. However, some potential dependence was identified on the existence of transient plastic deformation at crack tips, and the results were discussed regarding the relevant material properties including the excess energies of metastable phases and the critical energy release rate for intergranular fracture. In general, local plasticity at crack tips was observed in fracture simulations with potentials that predict low excess energies for metastable phases and high critical energy release rates for intergranular fracture.

  12. Molecular dynamics simulations of intergranular fracture in UO2 with nine empirical interatomic potentials

    NASA Astrophysics Data System (ADS)

    Zhang, Yongfeng; Millett, Paul C.; Tonks, Michael R.; Bai, Xian-Ming; Biner, S. Bulent

    2014-09-01

    The intergranular fracture behavior of UO2 was studied using molecular dynamics simulations with a bicrystal model. The anisotropic fracture behavior due to the different grain boundary characters was investigated with the <1 0 0> symmetrical tilt Σ5 and the <1 1 0> symmetrical tilt Σ3 ({1 1 1} twin) grain boundaries. Nine interatomic potentials, seven rigid-ion plus two core-shell ones, were utilized to elucidate possible potential dependence. Initiating from a notch, crack propagation along grain boundaries was observed for most potentials. The Σ3 boundary was found to be more prone to fracture than the Σ5 one, indicated by a lower energy release rate associated with the former. However, some potential dependence was identified on the existence of transient plastic deformation at crack tips, and the results were discussed regarding the relevant material properties including the excess energies of metastable phases and the critical energy release rate for intergranular fracture. In general, local plasticity at crack tips was observed in fracture simulations with potentials that predict low excess energies for metastable phases and high critical energy release rates for intergranular fracture.

  13. Structural analysis and intergranular corrosion tests of AISI 316L steel.

    PubMed

    Stonawská, Z; Svoboda, M; Sozańska, M; Krístková, M; Sojka, J; Dagbert, C; Hyspecká, L

    2006-10-01

    Pure AISI 316L steel is investigated after solution heat treatment (1050 degrees C/H(2)O) and structural sensitization (650 degrees C). Two quite different intergranular corrosion tests are used to determine the degree of structural sensitization due to the precipitation of secondary phases along the grain boundaries (mainly the M(23)C(6) and sigma-phase): the oxalic acid etch test and the electrochemical potentio-kinetic reactivation test. Generally, the dissolution of chromium-rich carbides (M(23)C(6)) is provoked by oxalic acid etch tests, whereas the chromium-depleted zones, in the vicinity of chromium-rich carbides (M(23)C(6)), are attacked by electrochemical potentio-kinetic reactivation tests. Both intergranular corrosion tests are used to determine the maximum degree of structural sensitization. Thus structural analysis by carbon replicas reveals the Laves phase, and both the M(23)C(6) and (Cr,Mo)(x)(Fe,Ni)(y) phases. The results of intergranular corrosion tests are related to the findings of the structural analysis. PMID:17100908

  14. Intergranular diffusion and embrittlement of a Ni-16Mo-7Cr alloy in Te vapor environment

    NASA Astrophysics Data System (ADS)

    Cheng, Hongwei; Li, Zhijun; Leng, Bin; Zhang, Wenzhu; Han, Fenfen; Jia, Yanyan; Zhou, Xingtai

    2015-12-01

    Nickel and some nickel-base alloys are extremely sensitive to intergranular embrittlement and tellurium (Te) enhanced cracking, which should be concerned during their serving in molten salt reactors. Here, a systematic study about the effects of its temperature on the reaction products at its surface, the intergranular diffusion of Te in its body and its embrittlement for a Ni-16Mo-7Cr alloy contacting Te is reported. For exposed to Te vapor at high temperature (823-1073 K), the reaction products formed on the surface of the alloy were Ni3Te2, CrTe, and MoTe2, and the most serious embrittlement was observed at 1073 K. The kinetic measurement in terms of Te penetration depth in the alloy samples gives an activation energy of 204 kJ/mol. Electron probe microanalysis confirmed the local enrichment of Te at grain boundaries. And clearly, the embrittlement was results from the intergranular diffusion and segregation of element Te.

  15. Reduced translocation of current photosynthate precedes changes in gas exchange for Quercus rubra seedlings under flooding stress.

    PubMed

    Sloan, Joshua L; Islam, M Anisul; Jacobs, Douglass F

    2016-01-01

    Northern red oak (Quercus rubra L.) seedlings are frequently planted on suboptimal sites in their native range in North America, subjecting them to environmental stresses, such as flooding, for which they may not be well adapted. Members of the genus Quercus exhibit a wide range of responses to flooding, and responses of northern red oak to flooding remain inadequately described. To better understand the physiological effects of root system inundation in post-transplant northern red oak seedlings and the effects of flooding on endogenous patterns of resource allocation within the plant, we observed the effects of short-term flooding initiated at the linear shoot growth stage on net photosynthetic rates, dark respiration, chlorophyll fluorescence (Fv/Fm) and translocation of (13)C-labeled current photosynthate. Downward translocation of current photosynthate declined after 4 days of flooding and was the first measured physiological response to flooding; net photosynthetic rates decreased and dark respiration rates increased after 7 days of flooding. Short-term flooding did not affect maximal potential efficiency of photosystem II (Fv/Fm). The finding that decreased downward translocation of (13)C-labeled current photosynthate preceded reduced net photosynthesis and increased dark respiration during flooding suggests the occurrence of sink-limited photosynthesis under these conditions. PMID:26655380

  16. Intergranular stress corrosion cracking and selective internal oxidation of nickel-chromium-iron alloys in hydrogenated steam

    NASA Astrophysics Data System (ADS)

    Capell, Brent M.

    2005-07-01

    Selective internal oxidation (SIO) is a mechanism of grain boundary embrittlement through the formation of intergranular oxides of Cr2O3. SIO is proposed as a mechanism to explain intergranular stress corrosion cracking (IGSCC) of Ni-base alloys in pressurized water reactor environments. The purpose of this work is to investigate SIO through a series of experiments using controlled-purity alloys in a controlled, low-pressure steam environment in which the oxygen potential is varied. Five alloys; Ni-9Fe, Ni-5Cr, LCr (Ni-5Cr-9Fe), CD85 (Ni-16Cr-9Fe) and HCr (Ni-30Cr-9Fe), were used in corrosion coupon exposure tests and constant extension rate tensile (CERT) tests at 550°C and 400°C in an environment consisting of a controlled mixture of hydrogen, water vapor and argon. The hydrogen-to-water vapor partial pressure ratio (PPR) was varied between 0.001 and 0.9 to control the oxygen partial pressure. The Ni-9Fe, Ni-5Cr and LCr alloys formed a uniform Ni(OH)2 film at PPR values less than 0.09 while CD85 and HCr formed Cr2O 3 oxide films over the entire PPR range. Corrosion coupon results also show the formation of highly localized oxide particles at grain boundaries. Focused ion beam analysis revealed that intergranular oxides were observed at significant depths (>150 nm) down grain boundaries and the oxide morphology depended on the alloy composition and PPR value. Diffusion of oxygen along the grain boundary accounted for the growth of intergranular oxides. CERT test results showed that intergranular cracking was caused by creep-induced microvoid coalescence only at 550°C and did not depend on PPR. At 400°C, the cracking behavior depended on the PPR and resulted in a mixture of creep-induced microvoid coalescence and brittle intergranular failure. The cracked boundary fraction was higher at a PPR value where a Ni(OH)2 surface film formed. Alloy composition influenced cracking and the cracked boundary fraction decreased as the alloy chromium content increased. The

  17. Reducing uncertainties associated with remotely sensed estimates of forest growth and carbon exchange in the Great Lakes Region

    NASA Astrophysics Data System (ADS)

    Cook, Bruce Douglas

    results can be improved using spatial inputs derived from a combination of LiDAR data and multispectral imagery, and uncertainties can be reduced by accounting for variations in leaf area and cloudiness. Land cover generalizations and failure to account for wetlands and wetland processes were less important for predicting plant production in this predominantly forested region.

  18. Warmer temperatures stimulate respiration and reduce net ecosystem productivity in a northern Great Plains grassland: Analysis of CO2 exchange in automatic chambers

    NASA Astrophysics Data System (ADS)

    Flanagan, L. B.

    2013-12-01

    The interacting effects of altered temperature and precipitation are expected to have significant consequences for ecosystem net carbon storage. Here I report the results of an experiment that evaluated the effects of elevated temperature and altered precipitation on ecosystem CO2 exchange in a northern Great Plains grassland, near Lethbridge, Alberta Canada. Open-top chambers were used to establish an experiment in 2012 with three treatments (control, warmed, warmed plus 50% of normal precipitation input). A smaller experiment with only the two temperature treatments (control and warmed) was conducted in 2013. Continuous half-hourly net CO2 exchange measurements were made using nine automatic chambers during May-October in both years. My objectives were to determine the sensitivity of the ecosystem carbon budget to temperature and moisture manipulations, and to test for direct and indirect effects of the environmental changes on ecosystem CO2 exchange. The experimental manipulations resulted primarily in a significant increase in air temperature in the warmed treatment plots. A cumulative net loss of carbon or negative net ecosystem productivity (NEP) occurred during May through September in the warmed treatment (NEP = -659 g C m-2), while in the control treatment there was a cumulative net gain of carbon (NEP = +50 g C m-2). An eddy covariance system that operated at the site, over a footprint region that was not influenced by the experimental treatments, also showed a net gain of carbon by the ecosystem. The reduced NEP was due to higher plant and soil respiration rates in the warmed treatment that appeared to be caused by a combination of: (i) higher carbon substrate availability indirectly stimulating soil respiration in the warmed relative to the control treatment, and (ii) a strong increase in leaf respiration likely caused by a shift in electron partitioning to the alternative pathway respiration in the warmed treatment, particularly when exposed to high

  19. Inhibition effect of the borate ion on intergranular stress corrosion cracking of sensitized type 304 stainless steel

    SciTech Connect

    Zhang, S.; Shibata, T.; Haruna, T.

    1998-06-01

    The intergranular stress corrosion cracking (IGSCC) behavior of sensitized type 304 stainless steel (SS) in dilute sodium borate solutions at 95 C was examined by slow strain rate testing using a dynamic observation system. The borate ion (B{sub 4}O{sub 7}{sup 2{minus}}) suppressed IGSCC susceptibility of sensitized type 304 SS by delaying the crack initiation time and reducing the crack initiation frequency. The inhibition effect of the borate ion on crack initiation may have resulted from its buffer effect on local acidification at crack nuclei and its inhibitive nature in reacting with metal ions to form a protective film. However, B{sub 4}O{sub 7}{sup 2{minus}} concentration provided no remarkable inhibition effect on crack velocity (CV), which depended mainly upon solution conductivity, within the scattered values. Hydroxyl ions also suppressed initiation of IGSCC, but not as effectively as B{sub 4}O{sub 7}{sup 2{minus}}. The crack initiation time obeyed the exponential probability distribution, and the CV obeyed the Weibull probability distribution.

  20. Assessment of susceptibility of Type 304 stainless steel to intergranular stress corrosion cracking in simulated Savannah River Reactor environments

    SciTech Connect

    Ondrejcin, R.S.; Caskey, C.R. Jr.

    1989-12-01

    Intergranular stress corrosion cracking (IGSCC) of Type 304 stainless steel rate tests (CERT) of specimens machined was evaluated by constant extension from Savannah River Plant (SRP) decontaminated process water piping. Results from 12 preliminary CERT tests verified that IGSCC occurred over a wide range of simulated SRP envirorments. 73 specimens were tested in two statistical experimental designs of the central composite class. In one design, testing was done in environments containing hydrogen peroxide; in the other design, hydrogen peroxide was omitted but oxygen was added to the environment. Prediction equations relating IGSCC to temperature and environmental variables were formulated. Temperature was the most important independent variable. IGSCC was severe at 100 to 120C and a threshold temperature between 40C and 55C was identified below which IGSCC did not occur. In environments containing hydrogen peroxide, as in SRP operation, a reduction in chloride concentration from 30 to 2 ppB also significantly reduced IGSCC. Reduction in sulfate concentration from 50 to 7 ppB was effective in reducing IGSCC provided the chloride concentration was 30 ppB or less and temperature was 95C or higher. Presence of hydrogen peroxide in the environment increased IGSCC except when chloride concentration was 11 ppB or less. Actual concentrations of hydrogen peroxide, oxygen and carbon dioxide did not affect IGSCC. Large positive ECP values (+450 to +750 mV Standard Hydrogen Electrode (SHE)) in simulated SRP environments containing hydrogen peroxide and were good agreement with ECP measurements made in SRP reactors, indicating that the simulated environments are representative of SRP reactor environments. Overall CERT results suggest that the most effective method to reduce IGSCC is to reduce chloride and sulfate concentrations.

  1. Molecular-dynamics Simulation-based Cohesive Zone Representation of Intergranular Fracture Processes in Aluminum

    NASA Technical Reports Server (NTRS)

    Yamakov, Vesselin I.; Saether, Erik; Phillips, Dawn R.; Glaessgen, Edward H.

    2006-01-01

    A traction-displacement relationship that may be embedded into a cohesive zone model for microscale problems of intergranular fracture is extracted from atomistic molecular-dynamics simulations. A molecular-dynamics model for crack propagation under steady-state conditions is developed to analyze intergranular fracture along a flat 99 [1 1 0] symmetric tilt grain boundary in aluminum. Under hydrostatic tensile load, the simulation reveals asymmetric crack propagation in the two opposite directions along the grain boundary. In one direction, the crack propagates in a brittle manner by cleavage with very little or no dislocation emission, and in the other direction, the propagation is ductile through the mechanism of deformation twinning. This behavior is consistent with the Rice criterion for cleavage vs. dislocation blunting transition at the crack tip. The preference for twinning to dislocation slip is in agreement with the predictions of the Tadmor and Hai criterion. A comparison with finite element calculations shows that while the stress field around the brittle crack tip follows the expected elastic solution for the given boundary conditions of the model, the stress field around the twinning crack tip has a strong plastic contribution. Through the definition of a Cohesive-Zone-Volume-Element an atomistic analog to a continuum cohesive zone model element - the results from the molecular-dynamics simulation are recast to obtain an average continuum traction-displacement relationship to represent cohesive zone interaction along a characteristic length of the grain boundary interface for the cases of ductile and brittle decohesion. Keywords: Crack-tip plasticity; Cohesive zone model; Grain boundary decohesion; Intergranular fracture; Molecular-dynamics simulation

  2. Understanding the Origins of Intergranular Corrosion in Copper-Containing Al-Mg-Si Alloys

    NASA Astrophysics Data System (ADS)

    Kairy, Shravan K.; Alam, Talukder; Rometsch, Paul A.; Davies, Chris H. J.; Banerjee, Raj; Birbilis, Nick

    2016-03-01

    A definitive understanding of the mechanism of intergranular corrosion (IGC) in under-aged (UA) Cu-containing Al-Mg-Si alloys has not been clear to date. The grain boundary microstructure and chemistry in an UA Cu-containing Al-Mg-Si alloy were characterized by coupling atom probe tomography and scanning transmission electron microscopy. The rapid formation of an ultra-thin wetting Cu layer and discrete Q-phase (Al4Cu2Mg8Si7) precipitates along the grain boundaries, and a precipitate-free zone adjacent to the grain boundaries in the UA condition contribute to IGC.

  3. Measuring electrostatic potential profiles across amorphous intergranular films by electron diffraction.

    PubMed

    Koch, Christoph T; Bhattacharyya, Somnath; Rühle, Manfred; Satet, Raphaëlle L; Hoffmann, Michael J

    2006-04-01

    Amorphous 1-2-nm-wide intergranular films in ceramics dictate many of their properties. The detailed investigation of structure and chemistry of these films pushes the limits of today's transmission electron microscopy. We report on the reconstruction of the one-dimensional potential profile across the film from an experimentally acquired tilt series of energy-filtered electron diffraction patterns. Along with the potential profile, the specimen thickness, film orientation with respect to the grain lattice and specimen surface, and the absolute specimen orientation with respect to the laboratory frame of reference are retrieved. PMID:17481353

  4. Intergranular Jc determination in toroidal high temperature superconductors using a soft-core closed magnetic circuit

    SciTech Connect

    Lessure, H.S.; Simizu, S.; Kung, P.J.; Baumert, B.A.; Snakar, S.G.; McHenry, M.E. )

    1991-03-01

    An examination of weak link coupling between grains has been made using a noncontact magnetic technique. This paper reports intergranular Jc(T) measurements for unaligned and grain aligned sintered YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} (YBC) toroids. Supercurrent is deduced from measurement of the net current encircling the core and Jc is found from supercurrent saturation in contrast to onset pickup voltage criteria. Agreement with recently reported direct transport measurements on the aligned sample suggests that the conduction mechanism is the same as for direct transport.

  5. Root causes of intergranular attack in an operating nuclear steam generator tube

    NASA Astrophysics Data System (ADS)

    Hur, Do Haeng; Lee, Deok Hyun; Choi, Myung Sik; Song, Myung Ho; Han, Jung Ho

    2008-04-01

    This paper reports the secondary side intergranular attack of an Alloy 600 tube, which was located within sludge piles in the hot-leg side of an operating nuclear steam generator. Carbide distribution along the grain boundaries and chromium depletion were analyzed using optical microscopy and transmission electron microscopy. Local crevice chemistry in contact with the defect was also assessed from the hideout return test data and oxide film analysis results using energy dispersive spectroscopy. The main causes of this defect are discussed based on the microstructure, local chemistry and operation temperature.

  6. Charge exchange system

    DOEpatents

    Anderson, Oscar A.

    1978-01-01

    An improved charge exchange system for substantially reducing pumping requirements of excess gas in a controlled thermonuclear reactor high energy neutral beam injector. The charge exchange system utilizes a jet-type blanket which acts simultaneously as the charge exchange medium and as a shield for reflecting excess gas.

  7. Critical level of intergranular fracture to affect the toughness of embrittled 2.25Cr-1Mo steels

    NASA Astrophysics Data System (ADS)

    Islam, M. A.; Knott, J. F.; Bowen, P.

    2004-10-01

    In general, the low-temperature brittle fracture mode of unembrittled ferritic steel is transgranular cleavage. During temper embrittlement, impurity elements, such as sulfur (S), phosphorus (P), antimony (Sb), arsenic (As), and tin (Sn), segregate to prior austenite grain boundaries, which results in a decrease in the grain boundary cohesive strength. As a result, the brittle transgranular cleavage fracture mode changes to intergranular decohesion in association with the decrease in the critical fracture (stress (σ F) as well as the fracture toughness (K). However, the appearance of intergranular facets on the fracture surface does not cause a decrease in the K and σ F values. In this work, quenched and fully tempered 2.25Cr-1Mo steel (in an unembrittled condition that exhibits almost 100% brittle transgranular cleavage fracture) has been embrittled for 24, 96, and 210 h at 520 °C to produce different proportions of intergranular fracture. These unembrittled and embrittled steel specimens were tested to measure K (at -120 and -196 °C) and σ F (at -196 °C). The experimental results and detailed fractographic observations show that the K and σ F values decrease with an increase in the area fraction of intergranular fracture, provided that the area fraction of the intergranular facet on the brittle fracture surface exceeded a certain critical level, approximately 20 22%.

  8. Mechanism of hydrodenitrogenation H{sub 2}-D{sub 2} exchange in reduced molybdenum catalysts. Ninth quarterly report, October 1--December 31, 1991

    SciTech Connect

    Miranda, R.

    1991-12-31

    Diffuse reflectance infrared spectroscopy was used to study the deuterium exchangeability of reduced molybdena catalysts supported on silica, alumina and 75% silica-alumina. It was found that silica hydroxyls react partially with deposited molybdena. The new species formed does not lead to regeneration of hydroxyl on the catalyst. On the other hand, the interaction of molybdena with alumina or silica-alumina leads to the generation of interfacial OH groups, that compensate for the hydroxyls lost to reaction. In this project is a proposed that the selectivity of the Hydrodenitrogenation (HDN) reaction can be affected by an alteration of the catalyst acidity since it is possible that an acidic Hofmann-like deamination pathway is operative (1) in parallel with the hydrogenolysis of saturated C--N--C bonds. Such was the conclusion from the study done of the denitrogenation of piperidine (3), where it was demonstrated that Bronsted acid sites are active for the denitrogenation of N-heterocycles where as Lewis sites are not.

  9. Intergranular fracture in UO{sub 2}: derivation of traction-separation law from atomistic simulations

    SciTech Connect

    Zhang, Yongfeng; Millett, P.C.; Tonks, M.R.; Bai, Xian-Ming; Biner, S.B.

    2013-07-01

    In this study, the intergranular fracture behavior of UO{sub 2} was studied by molecular dynamics simulations using the Basak potential. In addition, the constitutive traction-separation law was derived from atomistic data using the cohesive-zone model. In the simulations a bicrystal model with the (100) symmetric tilt Σ5 grain boundaries was utilized. Uniaxial tension along the grain boundary normal was applied to simulate Mode-I fracture. The fracture was observed to propagate along the grain boundary by micro-pore nucleation and coalescence, giving an overall intergranular fracture behavior. Phase transformations from the Fluorite to the Rutile and Scrutinyite phases were identified at the propagating crack tips. These new phases are metastable and they transformed back to the Fluorite phase at the wake of crack tips as the local stress concentration was relieved by complete cracking. Such transient behavior observed at atomistic scale was found to substantially increase the energy release rate for fracture. Insertion of Xe gas into the initial notch showed minor effect on the overall fracture behavior. (authors)

  10. Multiscale Modeling of Intergranular Fracture in Aluminum: Constitutive Relation For Interface Debonding

    NASA Technical Reports Server (NTRS)

    Yamakov, V.; Saether, E.; Glaessgen, E. H.

    2008-01-01

    Intergranular fracture is a dominant mode of failure in ultrafine grained materials. In the present study, the atomistic mechanisms of grain-boundary debonding during intergranular fracture in aluminum are modeled using a coupled molecular dynamics finite element simulation. Using a statistical mechanics approach, a cohesive-zone law in the form of a traction-displacement constitutive relationship, characterizing the load transfer across the plane of a growing edge crack, is extracted from atomistic simulations and then recast in a form suitable for inclusion within a continuum finite element model. The cohesive-zone law derived by the presented technique is free of finite size effects and is statistically representative for describing the interfacial debonding of a grain boundary (GB) interface examined at atomic length scales. By incorporating the cohesive-zone law in cohesive-zone finite elements, the debonding of a GB interface can be simulated in a coupled continuum-atomistic model, in which a crack starts in the continuum environment, smoothly penetrates the continuum-atomistic interface, and continues its propagation in the atomistic environment. This study is a step towards relating atomistically derived decohesion laws to macroscopic predictions of fracture and constructing multiscale models for nanocrystalline and ultrafine grained materials.

  11. Orbiter Cold Plate Intergranular Corrosion: Development of NDE Standards and Assessment of NDE Methods

    NASA Technical Reports Server (NTRS)

    Smith, Stephen W.; Winfree, William P.; Piascik, Robert S.

    2002-01-01

    During pre-servicing of a space shuttle (orbiter vehicle, OV-102), helium leak detection of an avionics cold plate identified a leak located in the face sheet oriented towards the support shelf. Subsequent destructive examination of the leaking cold plate revealed that intergranular corrosion had penetrated the 0.017-inch thick aluminum (AA6061) face sheet. The intergranular attack (IGA) was likely caused by an aggressive crevice environment created by condensation of water vapor between the cold plate and support shelf. Face sheet susceptibility to IGA is a result of the brazing process used in the fabrication of the cold plates. Cold plate components were brazed at 1000 F followed by a slow cooling process to avoid distortion of the bonded cold plate. The slow cool process caused excessive grain boundary precipitation resulting in a material that is susceptible to IGA. The objectives of this work are as follows: (1) Develop first-of-a-kind nondestructive evaluation (NDE) standards that contain IGA identical to that found in the orbiter cold plates; and (2) Assess advanced NDE techniques for corrosion detection and recommend methods for cold plate examination. This report documents the results of work performed at Langley Research Center to fulfill these objectives.

  12. Intergranular fracture in UO2: derivation of traction-separation law from atomistic simulations

    SciTech Connect

    Yongfeng Zhang; Paul C Millett; Michael R Tonks; Xian-Ming Bai; S Bulent Biner

    2013-10-01

    In this study, the intergranular fracture behavior of UO2 was studied by molecular dynamics simulations using the Basak potential. In addition, the constitutive traction-separation law was derived from atomistic data using the cohesive-zone model. In the simulations a bicrystal model with the (100) symmetric tilt E5 grain boundaries was utilized. Uniaxial tension along the grain boundary normal was applied to simulate Mode-I fracture. The fracture was observed to propagate along the grain boundary by micro-pore nucleation and coalescence, giving an overall intergranular fracture behavior. Phase transformations from the Fluorite to the Rutile and Scrutinyite phases were identified at the propagating crack tips. These new phases are metastable and they transformed back to the Fluorite phase at the wake of crack tips as the local stress concentration was relieved by complete cracking. Such transient behavior observed at atomistic scale was found to substantially increase the energy release rate for fracture. Insertion of Xe gas into the initial notch showed minor effect on the overall fracture behavior.

  13. Quasi-static intergranular cracking in a Cu-Sn alloy: An analog of stress relief cracking of steels

    SciTech Connect

    Barrera, E.V.; Menyhard, M.; Bika, D.; Rothman, B.; McMahon, C.J. Jr.

    1991-01-01

    Intergranular cracking in a laboratory-made Cu-8wt%Sn alloy at 265 to 300{degree}C in vacuum was studied in order to explore the hypothesis that this could serve as an analog to the brittle mode of stress-relief cracking in steels and to test the mechanism proposed earlier to explain that phenomenon. This mechanism involves the stress-induced intergranular penetration along grain boundaries of a surface-adsorbed embrittling element. Sulfur is the active element in this regard in steels, and tin was envisioned as playing the same role in Cu-Sn alloys. Auger spectroscopy was used to confirm earlier reports of the surface activity of tin and to determine the segregation kinetics in the present polycrystals; no other elements were found to segregate to surfaces to any significant degree in the present alloy. Crack growth measurements showed that intergranular cracking occurs in an intermittent manner at an average rate on the order of 0.1 {mu}m/sec over a range of crack length. Crack initiation was found to be remarkably sensitive to the stress intensity, implying the existence of a threshold. The fracture appearance in the regions of slow crack growth was similar to that observed in steels undergoing stress-relief cracking at 500--600{degree}C. It was concluded that the quasi-static intergranular cracking in the steels and in the Cu-Sn alloy represent two aspects of the same generic phenomenon and that the proposed mechanism of stress-induced intergranular impurity penetration is valid. It is believed that liquid-and solid-metal embrittlement are closely related to the type of intergranular cracking described here.

  14. Quasi-static intergranular cracking in a Cu-Sn alloy: An analog of stress relief cracking of steels

    SciTech Connect

    Barrera, E.V.; Menyhard, M.; Bika, D.; Rothman, B.; McMahon, C.J. Jr.

    1991-12-31

    Intergranular cracking in a laboratory-made Cu-8wt%Sn alloy at 265 to 300{degree}C in vacuum was studied in order to explore the hypothesis that this could serve as an analog to the brittle mode of stress-relief cracking in steels and to test the mechanism proposed earlier to explain that phenomenon. This mechanism involves the stress-induced intergranular penetration along grain boundaries of a surface-adsorbed embrittling element. Sulfur is the active element in this regard in steels, and tin was envisioned as playing the same role in Cu-Sn alloys. Auger spectroscopy was used to confirm earlier reports of the surface activity of tin and to determine the segregation kinetics in the present polycrystals; no other elements were found to segregate to surfaces to any significant degree in the present alloy. Crack growth measurements showed that intergranular cracking occurs in an intermittent manner at an average rate on the order of 0.1 {mu}m/sec over a range of crack length. Crack initiation was found to be remarkably sensitive to the stress intensity, implying the existence of a threshold. The fracture appearance in the regions of slow crack growth was similar to that observed in steels undergoing stress-relief cracking at 500--600{degree}C. It was concluded that the quasi-static intergranular cracking in the steels and in the Cu-Sn alloy represent two aspects of the same generic phenomenon and that the proposed mechanism of stress-induced intergranular impurity penetration is valid. It is believed that liquid-and solid-metal embrittlement are closely related to the type of intergranular cracking described here.

  15. The Respiratory Exchange Ratio is Associated with Fitness Indicators Both in Trained and Untrained Men: A Possible Application for People with Reduced Exercise Tolerance

    PubMed Central

    Ramos-Jiménez, Arnulfo; Hernández-Torres, Rosa P.; Torres-Durán, Patricia V.; Romero-Gonzalez, Jaime; Mascher, Dieter; Posadas-Romero, Carlos; Juárez-Oropeza, Marco A.

    2008-01-01

    Background: The respiratory exchange ratio (RER) indirectly shows the muscle’s oxidative capacity to get energy. Sedentarism, exercise and physically active lifestyles modify it. For that reason, this study evaluates the associations between RER during sub-maximum exercise and other well established fitness indicators (body fat, maximum heart rate, maximum O2 uptake, workload, and lactate threshold), in physically active trained and untrained men. Methods: The RER, O2 uptake and blood lactate were measured in eight endurance trained and eight untrained men (age, 22.9 ± 4.5 vs. 21.9 ± 2.8 years; body mass, 67.1 ± 5.4 vs. 72.2 ± 7.7 kg; body fat, 10.6 ± 2.4% vs. 16.6 ± 3.8% and maximum O2 uptake, 68.9 ± 6.3 vs. 51.6 ± 5.8 ml•kg−1•min−1), during maximum exercise test and during three different sub-maximum exercises at fixed workload: below, within or above the lactate threshold. Results: Endurance trained men presented higher O2 uptake, lower blood lactate concentrations and lower RER values than those in untrained men at the three similar relative workloads. Even though with these differences in RER, a strong association (p < 0.05) of RER during sub-maximum exercise with the other well established fitness indicators was observed, and both maximum O2 uptake and lactate threshold determined more than 57% of its variance (p < 0.05). Conclusions: These data demonstrate that RER measurement under sub-maximum exercise conditions was well correlated with other established physical fitness indicators, despite training condition. Furthermore, the results suggest that RER could help obtain an easy approach of fitness status under low exercise intensity and could be utilized in subjects with reduced exercise tolerance. PMID:21157516

  16. Intergranular stress corrosion cracking susceptibility of neutron-irradiated, thermally sensitized type 304 stainless steel

    SciTech Connect

    Onchi, T.; Hide, K.; Mayuzumi, M.; Hoshiya, T.

    2000-05-01

    Austenitic stainless steels (SS) have been used as core component materials for light water reactors. As reactors age, however, the material tends to suffer from degradation primarily resulting from irradiation-assisted stress corrosion cracking (IASCC) as well as intergranular stress corrosion cracking (IGSCC). Neutron-irradiated, thermally sensitized Type 304 (UNS S30400) stainless steels (SS) were examined by slow strain rate (SSR) stress corrosion cracking (SCC) tests in 290 C water of 0.2 ppm dissolved oxygen concentration (DO) and by SSR tensile tests in 290 C inert gas environment. Neutron fluences ranged from 4 x 10{sup 22} n/m{sup 2} to 3 x 10{sup 25} n/m{sup 2} (energy [E] > 1 MeV). percent intergranular (%IG) cracking, which has been used as an intergranular (IG) cracking susceptibility indicator in the SSR SCC tests, changes anomalously with neutron fluence in spite of the strain-to-failure rate decreasing with an increase of neutron fluence. Apparently, %IG is a misleading indicator for the irradiated, thermally sensitized Type 304 SS and for the irradiated, nonsensitized SS when IG cracking susceptibility is compared at different neutron fluences, test temperatures, DO, and strain rates. These test parameters may affect deformation and fracture behaviors of the irradiated SS during the SSR SCC tests, resulting in changing %IG, which is given by the ratio of the total IG cracking area to the entire fracture surface area. It is suggested that strain-to-IG crack initiation for the irradiated, thermally sensitized SS and for the irradiated, nonsensitized SS is the alternative indicator in the SSR SCC tests. An engineering expedient to determine the IG crack initiation strain is given by a deviating point on superposed stress-strain curves in inert gas and in oxygenated water. The strain-to-IG crack initiation becomes smaller with an increase of neutron fluence and DO. The SSR tensile tests in inert gas are needed to obtain strain-to-IG crack initiation in

  17. Stress corrosion cracking and intergranular corrosion of neutron irradiated austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Fukuya, K.; Shima, S.; Kayano, H.; Narui, M.

    1992-09-01

    The effects of irradiation on stress corrosion cracking (SCC) and intergranular corrosion (IGC) susceptibility were investigated in solution-treated Fe19Cr9NiMn alloys and JPCA irradiated to 5.3×1024 n/m2 (E > 1 MeV) at 573 K. In Fe19Cr9NiMn alloys, the irradiation enhanced IGC i n boiling HNO3 + Cr6+ solution when the alloys contained phosphorus and silicon and induced SCC in all the alloys with strain rate tensile tests in 571 K water containing 32 ppm oxygen. With increasing phosphorus and silicon contents. IGC was promoted but IGSCC was suppressed after irradiation. The results indicated that these elements are not the main contributors to irradiation-assisted SCC, although they affect SCC behavior. The Japanese Prime Candidate Alloy (JPCA) had better SCC resistance than Fe19Cr9NiMn alloys under the present irradiation condition.

  18. Dental materials. Amorphous intergranular phases control the properties of rodent tooth enamel.

    PubMed

    Gordon, Lyle M; Cohen, Michael J; MacRenaris, Keith W; Pasteris, Jill D; Seda, Takele; Joester, Derk

    2015-02-13

    Dental enamel, a hierarchical material composed primarily of hydroxylapatite nanowires, is susceptible to degradation by plaque biofilm-derived acids. The solubility of enamel strongly depends on the presence of Mg(2+), F(-), and CO3(2-). However, determining the distribution of these minor ions is challenging. We show—using atom probe tomography, x-ray absorption spectroscopy, and correlative techniques—that in unpigmented rodent enamel, Mg(2+) is predominantly present at grain boundaries as an intergranular phase of Mg-substituted amorphous calcium phosphate (Mg-ACP). In the pigmented enamel, a mixture of ferrihydrite and amorphous iron-calcium phosphate replaces the more soluble Mg-ACP, rendering it both harder and more resistant to acid attack. These results demonstrate the presence of enduring amorphous phases with a dramatic influence on the physical and chemical properties of the mature mineralized tissue. PMID:25678658

  19. Proceedings: 1984 Workshop on Secondary-Side Stress Corrosion Cracking and Intergranular Corrosion of PWR Steam Generator Tubing

    SciTech Connect

    1986-03-01

    During 1984, research investigating intergranular corrosion and stress corrosion cracking in PWR steam generators provided data to formulate a corrosion-product transport theory. In addition, the research showed that changing the pH of liquids in generator crevices will retard and sometimes arrest the corrosion process.

  20. Intergranular attack and stress corrosion cracking of Alloy 600 in high-temperature caustic solutions containing contaminants

    SciTech Connect

    Bandy, R.; Roberge, R.; van Rooyen, D.

    1985-06-01

    Concentrated caustic is a primary cause of stress corrosion cracking and intergranular attack of Alloy 600 tubing in PWRs. However, temperature, electrochemical potential, stress, and metallurgical state all play a role. This study provides the quantitative evidence needed to develop models of crack growth and to devise effective countermeasures.

  1. Self-sintering-assisted high intergranular connectivity in ball-milled ex situ MgB2 bulks

    NASA Astrophysics Data System (ADS)

    Mizutani, Shunsuke; Yamamoto, Akiyasu; Shimoyama, Jun-ichi; Ogino, Hiraku; Kishio, Kohji

    2014-11-01

    To understand the mechanisms leading to higher intergranular connectivity in polycrystalline ex situ MgB2 prepared using a pressure-less self-sintering technique, the influence of the initial particle size of the MgB2 powder was investigated. MgB2 bulks sintered at 900 °C for 24 h using ball-milled powders exhibited a network structure with both qualitatively and quantitatively improved intergranular couplings. The connectivity calculated using normal-state transport measurements reached a high value of ˜40%, which is comparable to that of MgB2 bulks fabricated via Mg diffusion or high-pressure-assisted processes. Moreover, the sintering time required to achieve a reasonably high connectivity of 25-30% was less than 1 h. Notably, microstructural analyses confirmed the formation of intergranular necks and grain boundaries during the early stage of sintering. These results suggested self-sintering of the ball-milled MgB2 bulks proceeded much more rapidly than those sintered using an MgB2 powder without ball-milling. Increased intergranular contact points and decreased gap length between grains in green compact are assumed to be the origins for the stimulated self-sintering and corresponding increase in the electrical connectivity.

  2. Comparison of Acetate Turnover in Methanogenic and Sulfate-Reducing Sediments by Radiolabeling and Stable Isotope Labeling and by Use of Specific Inhibitors: Evidence for Isotopic Exchange

    PubMed Central

    de Graaf, W.; Wellsbury, P.; Parkes, R. J.; Cappenberg, T. E.

    1996-01-01

    Acetate turnover in the methanogenic freshwater anoxic sediments of Lake Vechten, The Netherlands, and in anoxic sediments from the Tamar Estuary, United Kingdom, and the Grosser Jasmunder Bodden, Germany, the latter two dominated by sulfate reduction, was determined. Stable isotopes and radioisotopes, inhibitors (chloroform and fluoroacetate), and methane flux were used to provide independent estimates of acetate turnover. Pore water acetate pool sizes were determined by gas chromatography with a flame ionization detector, and stable isotope-labeled acetate was determined by gas chromatography-mass spectrometry. The appearance of acetates with a different isotope labeling pattern from that initially added demonstrated that isotopic exchange occurred during methanogenic acetate metabolism. The predominant exchange processes were (i) D-H exchange in the methyl group and (ii) (sup13)C-(sup12)C exchange at the carboxyl carbon. These exchanges are most probably caused by the activity of the enzyme complex carbon monoxide dehydrogenase and subsequent methyl group dehydrogenation by tetrahydromethanopterine or a related enzyme. The methyl carbon was not subject to exchange during transformation to methane, and hence acetate with the methyl carbon labeled will provide the most reliable estimate of acetate turnover to methane. Acetate turnover rate estimates with these labels were consistent with independent estimates of acetate turnover (acetate accumulation after inhibition and methane flux). Turnover rates from either radioisotope- or stable isotope-labeled methyl carbon isotopes are, however, dependent on accurate determination of the acetate pool size. The additions of large amounts of stable isotope-labeled acetate elevate the acetate pool size, stimulating acetate consumption and causing deviation from steady-state kinetics. This can, however, be overcome by the application of a non-steady-state model. Isotopic exchange in sediments dominated by sulfate reduction

  3. Reducing uncertainty in model estimates of high-latitude net ecosystem exchange by incorporating remote sensing observations of snow cover area

    NASA Astrophysics Data System (ADS)

    Luus, Kristina; Lin, John; Kelly, Richard

    2013-04-01

    Recent high-latitude studies have indicated that the seasonal timing of initial snow accumulation and final snow melt each year substantially influence net ecosystem exchange (NEE). Previous terrestrial biogeochemical models have either not simulated the influence of snow season processes on NEE, or have used process-based estimates of snow depth or subnivean temperature to estimate snow season NEE. As predictions indicate that the northern carbon balance is likely to be altered by cumulative and interconnected changes in Arctic air temperature, precipitation, and snowpack dynamics, uncertainty in estimates of NEE may be reduced by incorporating independent remote sensing observations of fractional snow cover into terrestrial biogeochemical models. The objective of this study was to examine whether uncertainty in Vegetation Photosynthesis and Respiration Model (VPRM) estimates of North American NEE north of 55°N could be reduced by using remote sensing observations to explicitly represent the influence of fractional snow cover on NEE. VPRM is a biospheric carbon flux model that generates high resolution estimates of NEE from remote sensing observations of air temperature, shortwave radiation and the normalized difference vegetation index (NDVI). In the standard VPRM (VPRM0) formulation, photosynthesis is limited during the cold season by low air temperatures, diminished shortwave radiation and low NDVI values, and respiration is assumed to be constant below a threshold air temperature. Conversely, in the new VRPMsnow formulation, moderate resolution imaging spectroradiometer (MODIS) observations of fractional snow cover are used to simulate the effects snow has on suppressing photosynthetic uptake by vegetation and decoupling soil and air temperatures. Therefore, when MODIS observations indicate that snow is present at a location, the rate of photosynthetic uptake by vegetation is diminished as a function of the fractional snow cover area, and when a region is

  4. Cu2ZnSnSe4 nanocrystals capped with S(2-) by ligand exchange: utilizing energy level alignment for efficiently reducing carrier rec ombination.

    PubMed

    Wang, Xia; Kou, Dong-Xing; Zhou, Wen-Hui; Zhou, Zheng-Ji; Wu, Si-Xin; Cao, Xuan

    2014-01-01

    In this work, we employed a convenient one-step synthesis method for synthesizing Cu2ZnSnSe4 (CZTSe) nanocrystals (NCs) in an excess selenium environment. This excess selenium situation enhanced the reaction of metal acetylacetonates with selenium, resulting in the burst nucleation of NCs at relatively low temperatures. The phase morphology and surface and optoelectronic properties of NCs before and after ligand exchange were discussed in depth. It was found that pure tetragonal-phase structure CZTSe NCs with approximately 1.7-eV bandgap could be synthesized. The removal of large organic molecules on CZTSe NCs after ligand exchange by S(2-) decreased the resistivity. The bandgap of the films after ligand exchange by 550°C selenization was also decreased due to better crystallinity. For potential application in CZTSe solar cells, we constructed an energy level diagram to explain the mutual effect between the absorption layer and CdS layer. Using cyclic voltammetry (CV) measurement, we found that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of CZTSe films shifted down after ligand exchange. After energy level alignment at the CdS/CZTSe interface, a type I band alignment structure was more conveniently formed after ligand exchange. This structure acted as the barrier against injection electrons from ZnO to the CZTSe layer, and recombination would subsequently be depressed. PMID:24994951

  5. Cu2ZnSnSe4 nanocrystals capped with S2− by ligand exchange: utilizing energy level alignment for efficiently reducing carrier rec ombination

    PubMed Central

    2014-01-01

    In this work, we employed a convenient one-step synthesis method for synthesizing Cu2ZnSnSe4 (CZTSe) nanocrystals (NCs) in an excess selenium environment. This excess selenium situation enhanced the reaction of metal acetylacetonates with selenium, resulting in the burst nucleation of NCs at relatively low temperatures. The phase morphology and surface and optoelectronic properties of NCs before and after ligand exchange were discussed in depth. It was found that pure tetragonal-phase structure CZTSe NCs with approximately 1.7-eV bandgap could be synthesized. The removal of large organic molecules on CZTSe NCs after ligand exchange by S2− decreased the resistivity. The bandgap of the films after ligand exchange by 550°C selenization was also decreased due to better crystallinity. For potential application in CZTSe solar cells, we constructed an energy level diagram to explain the mutual effect between the absorption layer and CdS layer. Using cyclic voltammetry (CV) measurement, we found that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of CZTSe films shifted down after ligand exchange. After energy level alignment at the CdS/CZTSe interface, a type I band alignment structure was more conveniently formed after ligand exchange. This structure acted as the barrier against injection electrons from ZnO to the CZTSe layer, and recombination would subsequently be depressed. PMID:24994951

  6. On the toughening of brittle materials by grain bridging:promoting intergranular fracture through grain angle, strength, andtoughness

    SciTech Connect

    Foulk III, J.W.; Johnson, G.C.; Klein, P.A.; Ritchie, R.O.

    2007-11-15

    The structural reliability of many brittle materials such asstructural ceramics relies on the occurrence of intergranular, as opposedto transgranular, fracture in order to induce toughening by grainbridging. For a constant grain boundary strength and grain boundarytoughness, the current work examines the role of grain strength, graintoughness, and grain angle in promoting intergranular fracture in orderto maintain such toughening. Previous studies have illustrated that anintergranular path and the consequent grain bridging process can bepartitioned into five distinct regimes, namely: propagate, kink, arrest,stall and bridge. To determine the validity of the assumed intergranularpath, the classical penentration/deflection problem of a crack impingingon an interface is reexamined within a cohesive zone framework forintergranular and transgranular fracture. Results considering both modesof propagation, i.e., a transgranular and intergranular path, reveal thatcrack-tip shielding is a natural outcome of the cohesive zone approach tofracture. Cohesive zone growth in one mode shields the opposing mode fromthe stresses required for cohesive zone initiation. Although stablepropagation occurs when the required driving force is equivalent to thetoughness for either transgranular or intergranular fracture, the mode ofpropagation depends on the normalized grain strength, normalized graintoughness, and grain angle. For each grain angle, the intersection ofsingle path and multiple path solutions demarcates "strong" grains thatincrease the macroscopic toughness and "weak" grains that decrease it.The unstable transition to intergranular fracture reveals that anincreasinggrain toughness requires a growing region of the transgranularcohesive zone be at and near the peak cohesive strength. The inability ofthe body to provide the requisite stress field yields an overdriven andunstable configuration. The current results provide restrictions for theachievement of substantial toughening

  7. Intravenous HOE-642 reduces brain edema and Na uptake in the rat permanent middle cerebral artery occlusion model of stroke: evidence for participation of the blood-brain barrier Na/H exchanger.

    PubMed

    O'Donnell, Martha E; Chen, Yi-Je; Lam, Tina I; Taylor, Kelleen C; Walton, Jeffrey H; Anderson, Steven E

    2013-02-01

    Cerebral edema forms in the early hours of ischemic stroke by processes involving increased transport of Na and Cl from blood into brain across an intact blood-brain barrier (BBB). Our previous studies provided evidence that the BBB Na-K-Cl cotransporter is stimulated by the ischemic factors hypoxia, aglycemia, and arginine vasopressin (AVP), and that inhibition of the cotransporter by intravenous bumetanide greatly reduces edema and infarct in rats subjected to permanent middle cerebral artery occlusion (pMCAO). More recently, we showed that BBB Na/H exchanger activity is also stimulated by hypoxia, aglycemia, and AVP. The present study was conducted to further investigate the possibility that a BBB Na/H exchanger also participates in edema formation during ischemic stroke. Sprague-Dawley rats were subjected to pMCAO and then brain edema and Na content assessed by magnetic resonance imaging diffusion-weighed imaging and magnetic resonance spectroscopy Na spectroscopy, respectively, for up to 210 minutes. We found that intravenous administration of the specific Na/H exchange inhibitor HOE-642 significantly decreased brain Na uptake and reduced cerebral edema, brain swelling, and infarct volume. These findings support the hypothesis that edema formation and brain Na uptake during the early hours of cerebral ischemia involve BBB Na/H exchanger activity as well as Na-K-Cl cotransporter activity. PMID:23149557

  8. Reduced Epithelial Na+/H+ Exchange Drives Gut Microbial Dysbiosis and Promotes Inflammatory Response in T Cell-Mediated Murine Colitis.

    PubMed

    Laubitz, Daniel; Harrison, Christy A; Midura-Kiela, Monica T; Ramalingam, Rajalakshmy; Larmonier, Claire B; Chase, John H; Caporaso, J Gregory; Besselsen, David G; Ghishan, Fayez K; Kiela, Pawel R

    2016-01-01

    Inflammatory bowel diseases (IBD) are associated with functional inhibition of epithelial Na+/H+ exchange. In mice, a selective disruption of NHE3 (Slc9a3), a major apical Na+/H+ exchanger, also promotes IBD-like symptoms and gut microbial dysbiosis. We hypothesized that disruption of Na+/H+ exchange is necessary for the development of dysbiosis, which promotes an exacerbated mucosal inflammatory response. Therefore, we performed a temporal analysis of gut microbiota composition, and mucosal immune response to adoptive T cell transfer was evaluated in Rag2-/- and NHE3-/-/Rag2-/- (DKO) mice with and without broad-spectrum antibiotics. Microbiome (16S profiling), colonic histology, T cell and neutrophil infiltration, mucosal inflammatory tone, and epithelial permeability were analyzed. In adoptive T cell transfer colitis model, Slc9a3 status was the most significant determinant of gut microbial community. In DKO mice, NHE3-deficiency and dysbiosis were associated with dramatically accelerated and exacerbated disease, with rapid body weight loss, increased mucosal T cell and neutrophil influx, increased mucosal cytokine expression, increased permeability, and expansion of CD25-FoxP3+ Tregs; this enhanced susceptibility was alleviated by oral broad-spectrum antibiotics. Based on these results and our previous work, we postulate that epithelial electrolyte homeostasis is an important modulator in the progression of colitis, acting through remodeling of the gut microbial community. PMID:27050757

  9. Reduced Epithelial Na+/H+ Exchange Drives Gut Microbial Dysbiosis and Promotes Inflammatory Response in T Cell-Mediated Murine Colitis

    PubMed Central

    Midura-Kiela, Monica T.; Ramalingam, Rajalakshmy; Larmonier, Claire B.; Chase, John H.; Caporaso, J. Gregory; Besselsen, David G.; Ghishan, Fayez K.; Kiela, Pawel R.

    2016-01-01

    Inflammatory bowel diseases (IBD) are associated with functional inhibition of epithelial Na+/H+ exchange. In mice, a selective disruption of NHE3 (Slc9a3), a major apical Na+/H+ exchanger, also promotes IBD-like symptoms and gut microbial dysbiosis. We hypothesized that disruption of Na+/H+ exchange is necessary for the development of dysbiosis, which promotes an exacerbated mucosal inflammatory response. Therefore, we performed a temporal analysis of gut microbiota composition, and mucosal immune response to adoptive T cell transfer was evaluated in Rag2-/- and NHE3-/-/Rag2-/- (DKO) mice with and without broad-spectrum antibiotics. Microbiome (16S profiling), colonic histology, T cell and neutrophil infiltration, mucosal inflammatory tone, and epithelial permeability were analyzed. In adoptive T cell transfer colitis model, Slc9a3 status was the most significant determinant of gut microbial community. In DKO mice, NHE3-deficiency and dysbiosis were associated with dramatically accelerated and exacerbated disease, with rapid body weight loss, increased mucosal T cell and neutrophil influx, increased mucosal cytokine expression, increased permeability, and expansion of CD25-FoxP3+ Tregs; this enhanced susceptibility was alleviated by oral broad-spectrum antibiotics. Based on these results and our previous work, we postulate that epithelial electrolyte homeostasis is an important modulator in the progression of colitis, acting through remodeling of the gut microbial community. PMID:27050757

  10. Intergranular Cracking Susceptibility of 2.25Cr Heat-Resistant Steels Depending on Alloying Elements and Impurities

    NASA Astrophysics Data System (ADS)

    Sung, Hyun Je; Heo, Nam Hoe; Kim, Sung-Joon

    2016-05-01

    The intergranular cracking susceptibility of 2.25Cr heat-resistant steels increases with increasing bulk phosphorus content. This is due to the increase in phosphorus segregation concentration of prior austenite grain boundaries (PAGBs) and the prior austenite grain boundary/carbide interfaces (GCIs) with increasing bulk phosphorus content. Moreover, the susceptibility is higher in tungsten-added steels than the molybdenum-added steel. This is attributed to the higher driving force for carbide formation of tungsten which causes more active carbide formation in the tungsten-added steel, the consequent absence of the repulsive segregation between carbon and phosphorus, and the final higher phosphorus segregation concentration at the PAGBs and the GCIs. Additionally, the absence of sulfur segregation at the PAGBs and the GCIs of the molybdenum-added steel, which arises from the repulsive segregation between carbon and sulfur, acts as an additional factor which lowers the intergranular cracking susceptibility.

  11. Atomistic Structure, Strength, and Kinetic Properties of Intergranular Films in Ceramics

    SciTech Connect

    Garofalini, Stephen H

    2015-01-08

    Intergranular films (IGFs) present in polycrystalline oxide and nitride ceramics provide an excellent example of nanoconfined glasses that occupy only a small volume percentage of the bulk ceramic, but can significantly influence various mechanical, thermal, chemical, and optical properties. By employing molecular dynamics computer simulations, we have been able to predict structures and the locations of atoms at the crystal/IGF interface that were subsequently verified with the newest electron microscopies. Modification of the chemistry of the crystal surface in the simulations provided the necessary mechanism for adsorption of specific rare earth ions from the IGF in the liquid state to the crystal surface. Such results had eluded other computational approaches such as ab-initio calculations because of the need to include not only the modified chemistry of the crystal surfaces but also an accurate description of the adjoining glassy IGF. This segregation of certain ions from the IGF to the crystal caused changes in the local chemistry of the IGF that affected fracture behavior in the simulations. Additional work with the rare earth ions La and Lu in the silicon oxynitride IGFs showed the mechanisms for their different affects on crystal growth, even though both types of ions are seen adhering to a bounding crystal surface that would normally imply equivalent affects on grain growth.

  12. Effect of intergranular surface attack on the fatigue and corrosion properties of AM-355 CRT material

    SciTech Connect

    Bhansali, K.J.; Liu, G.; Grendahl, S.M.; Champagne, V.K.; Pepi, M.S.

    1998-12-31

    A dynamic part, consisting of a stack of laminates, failed in the field after an unexpectedly short life. Failure analysis showed that a multitude of fatigue cracks originated from a combination of corrosion and fretting. Recent changes in the production process of the laminates resulted in the presence of an intergranular (IG) morphology on the surface. Due to the criticality of this part`s application, a better understanding of the influence of varying degrees of IG attack on fatigue properties was pursued. Coupon specimens were machined from actual components with different surface IG conditions and were subjected to fatigue testing. Results showed a direct relationship between the number of cycles to failure and the severity of surface IG attack. Potentiodynamic polarization measurements indicated that a sample with IG attack had a lower breakdown potential and an unstable passivation behavior as compared to that without an IG attack. The detrimental effects of surface IG attack on the crack initiation process, endurance limit and corrosion resistance is discussed in terms of the stress concentration and breakdown of the passivation layer.

  13. Issues of intergranular embrittlement of VVER-type nuclear reactors pressure vessel materials

    NASA Astrophysics Data System (ADS)

    Zabusov, O.

    2016-04-01

    In light of worldwide tendency to extension of service life of operating nuclear power plants - VVER-type in the first place - recently a special attention is concentrated on phenomena taking place in reactor pressure vessel materials that are able to lead to increased level of mechanical characteristics degradation (resistibility to brittle fracture) during long term of operation. Formerly the hardening mechanism of degradation (increase in the yield strength under influence of irradiation) mainly had been taken into consideration to assess pressure vessel service life limitations, but when extending the service life up to 60 years and more the non-hardening mechanism (intergranular embrittlement of the steels) must be taken into account as well. In this connection NRC “Kurchatov Institute” has initiated a number of works on investigations of this mechanism contribution to the total embrittlement of reactor pressure vessel steels. The main results of these investigations are described in this article. Results of grain boundary phosphorus concentration measurements in specimens made of first generation of VVER-type pressure vessels materials as well as VVER-1000 surveillance specimens are presented. An assessment of non-hardening mechanism contribution to the total ductile-to- brittle transition temperature shift is given.

  14. Direct visualization of β phase causing intergranular forms of corrosion in Al–Mg alloys

    SciTech Connect

    Yang, Young-Ki Allen, Todd

    2013-06-15

    For a more effective examination of microstructure in Al–Mg alloys, a new etching solution has been developed; dissolved ammonium persulfate in water. It is demonstrated how β phase (Al{sub 3}Mg{sub 2}) in Al–Mg alloys respond to this solution using samples of a binary Al–Mg alloy and a commercial 5083 aluminum alloy. Nanometer sized β phase is clearly visualized for the first time using scanning electron microscopy (SEM) instead of transmission electron microscopy (TEM). It is anticipated that direct and unambiguous visualization of β phase will greatly augment intergranular corrosion research in 5xxx series aluminum alloys. - Highlights: • Nanometer sized β phase in Al-10% Mg is first clearly visualized with SEM. • Nanometer sized β phase in wrought alloy 5083 is first clearly visualized with SEM. • Grain boundary decorating β phase and isolated sponge-like β phase are shown. • This phase is confirmed to be β phase using composition analysis.

  15. A microstructural study of phosphorus segregation and intergranular fracture in neutron irradiated submerged-arc welds

    SciTech Connect

    Bischler, P.J.E.; Wild, R.K.

    1996-12-31

    Accelerated irradiation experiments have been carried out on submerged-arc welds to obtain validation of trend curves built up from surveillance results. This was done by withdrawing surveillance specimens and re-irradiating them in higher flux positions. One batch, from weld HS, showed a significantly higher increase in the Charpy {Delta}T{sub 40J} value than that for weld LS at a similar dose. Work done to explain this difference is described in this paper. Selected Charpy specimens were examined using a shielded scanning electron microscope to determine the fracture modes present. Regions of mixed cleavage, micro-void coalescence (MVC) and intergranular failure (IGF) were found on HS weld specimens fractured in the transition region. The IFG was confined to certain regions within each weld bead. Significantly less IGF was found on LS weld specimens. Sub-fracture surface matchstick specimens were removed from embrittled regions and fractured within a scanning Auger microscope. IGF occurred in these specimens, and phosphorus was found to be the main grain boundary segregant. The levels of phosphorus increased with increasing neutron dose. No other embrittling element was consistently found at any significant level, but carbon was also found on grain boundary surfaces in some cases. The grain boundary coverage of phosphorus was determined for each weld at several neutron dose levels.

  16. Intergranular Corrosion Behavior of Low-Nickel and 304 Austenitic Stainless Steels

    NASA Astrophysics Data System (ADS)

    Bansod, Ankur V.; Patil, Awanikumar P.; Moon, Abhijeet P.; Khobragade, Nilay N.

    2016-07-01

    Intergranular corrosion (IGC) susceptibility for Cr-Mn austenitic stainless steel and 304 austenitic stainless steel (ASS) was estimated using electrochemical techniques. Optical and SEM microscopy studies were carried out to investigate the nature of IGC at 700 °C with increasing time (15, 30, 60, 180, 360, 720, 1440 min) according to ASTM standard 262 A. Quantitative analysis was performed to estimate the degree of sensitization (DOS) using double loop electrochemical potentiokinetic reactivation (DLEPR) and EIS technique. DLEPR results indicated that with the increase in thermal aging duration, DOS becomes more severe for both types of stainless steel. The DOS for Cr-Mn ASS was found to be higher (65.12% for 1440 min) than that of the AISI 304 ASS (23% for 1440 min). The higher degree of sensitization resulted in lowering of electrical charge capacitance resistance. Chronoamperometry studies were carried out at a passive potential of 0.4 V versus SCE and was observed to have a higher anodic dissolution of the passive film of Cr-Mn ASS. EDS studies show the formation of chromium carbide precipitates in the vicinity of the grain boundary. The higher Mn content was also observed for Cr-Mn ASS at the grain boundary.

  17. Intergranular fracture in irradiated Inconel X-750 containing very high concentrations of helium and hydrogen

    SciTech Connect

    Judge, Colin D.; Gauquelin, Nicolas; Walters, Lori; Wright, Mike; Cole, James I.; Madden, James; Botton, Gianluigi A.; Griffiths, Malcolm

    2015-02-01

    In recent years, it has been determined that Inconel X-750 CANDU spacers have lost strength and material ductility following irradiation in reactor. The irradiated fracture behaviour of ex-service material was also found to be entirely intergranular. The heavily thermalized flux spectrum in a CANDU reactor results in transmutation of 58Ni to 59Ni. The 59Ni itself has unusually high thermal neutron reaction cross-sections of the type: (n, γ), (n, p), and (n,α). The latter two reactions, in particular, contribute to a significant enhancement of the atomic displacements in addition to creating high concentrations of hydrogen and helium within the material. Metallographic examinations by transmission electron microscopy (TEM) have confirmed the presence of helium bubbles in the matrix and aligned along grain boundaries and matrix-precipitate interfaces. He bubble size and density are found to be highly dependent on the irradiation temperature and material microstructure; the bubbles are larger within grain boundary precipitates. TEM specimens extracted from fracture surfaces and crack tips give direct evidence linking crack propagation with grain boundary He bubbles.

  18. Theoretical studies on the mechanical behavior of granular materials under very low intergranular stresses

    NASA Technical Reports Server (NTRS)

    French, Kenneth W., Jr.

    1986-01-01

    The salient aspects of the theoretical modeling of a conventional triaxial test (CTC) of a cohesionless granular medium with stress and strain rate loading are described. Included are a controllable gravitational body force and provision for low confining pressure and/or very low intergranular stress. The modeling includes rational, analytic, and numerical phases, all in various stages of development. The numerical evolutions of theoretical models will be used in final design stages and in the analysis of the experimental data. In this the experimental design stage, it is of special interest to include in the candidate considerations every anomaly found in preliminary terrestrial experimentation. Most of the anomalies will be eliminated by design or enhanced for measurement as the project progresses. The main aspect of design being not the physical apparatus but the type and trajectories of loading elected. The major considerations that have been treated are: appearance and growth of local surface aberrations, stress-power coefficients, strain types, optical strain, radial bead migration, and measures of rotation for the proper stress flux.

  19. Intergranular corrosion following friction stir welding of aluminum alloy 7075-T651

    SciTech Connect

    Lumsden, J.B.; Mahoney, M.W.; Pollock, G.; Rhodes, C.G.

    1999-12-01

    Friction stir welding (FSW), a relatively new solid-state joining process, is used to join Al alloys of all compositions, including alloys essentially considered unweldable. This study focused on microstructures in FSW Al alloy 7075-T651 (AA 7075-T651 [UNS 97075-T651]), an alloy not commonly fusion welded, and the resultant corrosion susceptibility. Although the heat input associated with FSW was relatively low and the time at temperature was short compared to fusion welding, localized microstructures, chemical segregation, and precipitate distributions were created that generally are not present in parent metal AA 7075-T651. Typically, in the weld and heat affected zone (HAZ), the times at peak temperature were short, cooling was relatively rapid, and peak temperatures were {lt} {approx}500 C. Accordingly, a corresponding microstructural gradient developed from the weld nugget into the unaffected parent metal with the precipitate distribution in and around grain boundaries reflecting this temperature excursion. Some of these microstructures, when exposed to a corrosive environment, showed selective grain boundary attack and a decrease in the pitting potential relative to the parent metal. A characterization of the microstructure and localized chemistry differences within the weld zones suggested that the decrease in corrosion resistance correlated with a depletion of Cu within the grain boundaries and precipitate-free zones. These results provided evidence that the lowered resistance to intergranular corrosion following FSW of AA 7075-T651 was caused by a difference in pitting potentials.

  20. Natural and ion-exchanged illite clays reduce bacterial burden and inflammation in cutaneous meticillin-resistant Staphylococcus aureus infections in mice.

    PubMed

    Otto, Caitlin C; Kilbourne, Jacquelyn; Haydel, Shelley E

    2016-01-01

    Discoveries associated with antibacterial activity of hydrated clays necessitate assessments of in vivo efficacy, practical use and safety. Surface properties of clays can lead to variations in the composition and abundance of bound compounds or ions, thus affecting antibacterial activity. Since exchangeable metal ions released from the clay surface are responsible for in vitro antibacterial activity, we evaluated the in vivo antibacterial efficacy of four natural clays (one illite clay, two montmorillonite clays and one kaolinite clay) and three ion-exchanged, antibacterial clays against superficial, cutaneous meticillin-resistant Staphylococcus aureus (MRSA) infections in mice. Superficial, cutaneous wounds on the back of SKH1-Elite mice were generated and subsequently infected with MRSA. Following twice daily applications of a hydrated clay poultice to infected wounds for 7  days, we observed significant differences in the in vivo antibacterial efficacy between different types of clays. The natural and ion-exchanged illite clays performed best, as measured by bacterial load, inflammatory response and gross wound morphology with significant decreases in bacterial viability and dermatitis. Topical application of kaolinite clay was the least effective, resulting in the lowest decrease in bacterial load and exhibiting severe dermatitis. These data suggest that specific types of clays may offer a complementary and integrative strategy for topically treating MRSA and other cutaneous infections. However, since natural clays exhibit in vitro antibacterial variability and vary vastly in surface chemistries, adsorptive/absorptive characteristics and structural composition, the properties and characteristics of illite clays could aid in the development of standardized and customized aluminosilicates for topical infections. PMID:26508716

  1. Influences of intergranular structure on the magnetic properties of directly cast nanocrystalline NdFeCoTiNbBC alloys

    NASA Astrophysics Data System (ADS)

    Zhao, L. Z.; Hong, Y.; Jiao, D. L.; Qiu, Z. G.; Zhou, Q.; Hussain, M.; Liu, Z. W.; Greneche, J. M.; Zhang, G. Q.

    2016-05-01

    The millimeter-sized Nd9.5Fe61.5Co10Ti2.5Nb0.5B16‑x C x (x  =  0–1.25) alloy rods with various compositions were fabricated by direct casting. Nano-sized hard phase Nd2(FeCo)14B, soft phase ɑ-FeCo, and amorphous phase were observed in all alloys. An optimized amount of carbon additions improved the magnetic properties by enhancing the glass forming ability and forming near single domain-sized Nd2(FeCo)14B grains around the rod surface. Various intergranular structures were observed in the alloys with x  =  0.25–1. Micromagnetic simulation using the images obtained from the magnetic force microscope and transition electron microscope indicates that the distribution and magnetism of the intergranular phase have an important influence on the magnetic properties and demagnetization process of the alloys. A uniformly distributed nonmagnetic intergranular amorphous phase may enhance the magnetic properties, but the coercivity decreases when the amorphous phase is magnetic. It is important to modify the structure and distribution of the inter-grain amorphous phase in order to achieve high hard magnetic properties in these alloys.

  2. Slow Strain Rate Tensile Testing to Assess the Ability of Superalloys to Resist Environment-Assisted Intergranular Cracking

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; Telesman, Jack; Banik, Anthony; McDevitt, Erin

    2014-01-01

    Intergranular fatigue crack initiation and growth due to environmental degradation, especially at notched features, can often limit the fatigue life of disk superalloys at high temperatures. For clear comparisons, the effects of alloy composition on cracking in air needs to be understood and compared separately from variables associated with notches and cracks such as effective stress concentration, plastic flow, stress relaxation, and stress redistribution. The objective of this study was to attempt using simple tensile tests of specimens with uniform gage sections to compare the effects of varied alloy composition on environment-assisted cracking of several powder metal and cast and wrought superalloys including ME3, LSHR, Udimet 720, ATI 718Plus alloy, Haynes 282, and Inconel 740. Slow and fast strain-rate tensile tests were found to be a useful tool to compare propensities for intergranular surface crack initiation and growth. The effects of composition and heat treatment on tensile fracture strain and associated failure modes were compared. Environment interactions were determined to often limit ductility, by promoting intergranular surface cracking. The response of various superalloys and heat treatments to slow strain rate tensile testing varied substantially, showing that composition and microstructure can significantly influence environmental resistance to cracking.

  3. Selective Internal Oxidation as a Mechanism for Intergranular Stress Corrosion Cracking of Ni-Cr-Fe Alloys

    NASA Astrophysics Data System (ADS)

    Capell, Brent M.; Was, Gary S.

    2007-06-01

    The mechanism of selective internal oxidation (SIO) for intergranular stress corrosion cracking (IGSCC) of nickel-base alloys has been investigated through a series of experiments using high-purity alloys and a steam environment to control the formation of NiO on the surface. Five alloys (Ni-9Fe, Ni-5Cr, Ni-5Cr-9Fe, Ni-16Cr-9Fe, and Ni-30Cr-9Fe) were used to investigate oxidation and intergranular cracking behavior for hydrogen-to-water vapor partial pressure ratios (PPRs) between 0.001 and 0.9. The Ni-9Fe, Ni-5Cr, and Ni-5Cr-9Fe alloys formed a uniform Ni(OH)2 film at PPRs less than 0.09, and the higher chromium alloys formed chromium-rich oxide films over the entire PPR range studied. Corrosion coupon results show that grain boundary oxides extended for significant depths (>150 nm) below the sample surface for all but the highest Cr containing alloy. Constant extension rate tensile (CERT) test results showed that intergranular cracking varied with PPR and cracking was more pronounced at a PPR value where nonprotective Ni(OH)2 was able to form and a link between the nonprotective Ni(OH)2 film and the formation of grain boundary oxides is suggested. The observation of grain boundary oxides in stressed and unstressed samples as well as the influence of alloy content on IG cracking and oxidation support SIO as a mechanism for IGSCC.

  4. Coercivity enhancement of Dy-free Nd-Fe-B sintered magnets by intergranular adding Ho63.4Fe36.6 alloy

    NASA Astrophysics Data System (ADS)

    Liang, Liping; Ma, Tianyu; Wu, Chen; Zhang, Pei; Liu, Xiaolian; Yan, Mi

    2016-01-01

    High coercivity Nd-Fe-B sintered magnets serving in high-temperature environments always consume expensive and scarce heavy rare-earth Dy, which has simulated considerable interest to reduce Dy usage. In this work, coercivity of Dy-free magnets was investigated through intergranular adding eutectic Ho63.4Fe36.6 powders. The coercivity increases gradually up to 4 wt% Ho63.4Fe36.6 addition, however the remanence starts to deteriorate drastically as the addition is over 2.5 wt%. Coercivity above 18.0 kOe is obtained at the expense of a slight reduction in remanence through optimizing the addition amount and sintering conditions. The coercivity enhancement is explained through microstructural observations and elemental distribution analysis. (i) (Nd, Ho)2Fe14B shell forms in the outer region of 2:14:1 phase grains, strengthening the local magnetic anisotropy filed, (ii) RE-rich grain boundary phase with low Fe content is thickened, weakening the magnetic coupling between adjacent 2:14:1 phase grains, and (iii) 2:14:1 phase grains are refined upon lowering sintering temperature, reducing the microstructural defects and the stray fields aroused from neighboring grains.

  5. Study of the Intergranular Corrosion of Sensitized UNS S31803 Stainless Steel in Transpassive Region

    NASA Astrophysics Data System (ADS)

    Morshed Behbahani, Khashayar; Najafisayar, Pooria; Pakshir, Mahmoud

    2016-06-01

    In this study, intergranular corrosion behavior of UNS S31803 duplex stainless steel was investigated using conventional potentiodynamic polarization, double loop electrochemical potentiokinetic reactivation (DLEPR), and electrochemical impedance spectroscopy (EIS) technique carried out at different potentials in the transpassive region. Different types of heat treatments were used to obtain samples with different degrees of sensitization. The results of the DLEPR tests showed that the solution-annealed sample and that was sensitized for half an hour would be considered as nonsensitized ones. Moreover, the sample that was sensitized for 24 h exhibits the highest value of the degree of sensitization. Polarization test results showed a typical active-passive behavior from which the transpassive potential range was determined and used as the range of the applied DC bias in the EIS experiments. Three different AC responses (including capacitive and inductive responses) were observed depending on the value of applied DC bias in the EIS experiments. In addition, it was observed that the presence of the second inductive loop at high applied DC bias is due to the adsorption of nonsoluble corrosion products on the surface of the samples. Moreover, the fitted values to the charge transfer and polarization resistances (R ct and R P) decreased as the sensitization time increased from 30 min to 24 h. Such observations were in good accordance with the metallographic examination of the corroded surfaces, carried out by optical and scanning electron microscopy techniques, revealing discontinuous grain boundary attack in nonsensitized samples and a continuous network of grain boundary attack in the case of sensitized ones. Moreover, as the applied DC bias increases the ferrite phase attack also occurs in the sensitized samples. In addition, approximately no pitting corrosion was observed on the surface of the corroded samples which is in accordance with their respective cyclic

  6. Creep and intergranular cracking behavior of nickel-chromium-iron-carbon alloys in 360 C water

    SciTech Connect

    Angeliu, T.M.; Paraventi, D.J.; Was, G.S.

    1995-11-01

    Mechanical testing of controlled-purity Ni-x% Cr-9% Fe-y% C alloys at 360 C revealed an environmental enhancement in intergranular (IG) cracking and time-dependent deformation in high-purity (HP) and primary water (PW) over that exhibited in argon. Dimples on the IG facets indicated a creep void nucleation and growth failure mode. IG cracking was located primarily in the interior of the specimen and was not necessarily linked to the environment. Controlled-potential constant extension rate tensile (CERT) experiments showed increases in IG cracking as the applied potential decreased, suggesting that hydrogen was detrimental to the mechanical properties. It was proposed that the environment, through the presence of hydrogen, enhanced IG cracking by enhancing the matrix dislocation mobility. This conclusion was based on observations that dislocation creep controlled IG cracking of controlled-purity Ni-x% Cr-9% Fe-y% C in argon at 360 C. Grain-boundary cavitation (GBC) and sliding (GBS) results showed environmental enhancement of the creep rate primarily resulted from an increase in matrix plastic deformation. However, controlled-potential constant load tensile (CLT) experiments did not indicate a change in the creep rate as the applied potential decreased. While this result did not support hydrogen-assisted creep, the material already may have been saturated with hydrogen at these applied potentials, and thus, no effect was realized. Chromium and carbon decreased IG cracking in HP and PW by increasing the creep resistance. The surface film did not play a significant role in the creep or IG cracking behavior under the conditions investigated.

  7. Investigation of intergranular bright points from the New Vacuum Solar Telescope

    NASA Astrophysics Data System (ADS)

    Ji, Kai-Fan; Xiong, Jian-Ping; Xiang, Yong-Yuan; Feng, Song; Deng, Hui; Wang, Feng; Yang, Yun-Fei

    2016-05-01

    Six high-resolution TiO-band image sequences from the New Vacuum Solar Telescope (NVST) are used to investigate the properties of intergranular bright points (igBPs). We detect the igBPs using a Laplacian and morphological dilation algorithm (LMD) and automatically track them using a three-dimensional segmentation algorithm, and then investigate the morphologic, photometric and dynamic properties of igBPs in terms of equivalent diameter, intensity contrast, lifetime, horizontal velocity, diffusion index, motion range and motion type. The statistical results confirm previous studies based on G-band or TiO-band igBPs from other telescopes. These results illustrate that TiO data from the NVST are stable and reliable, and are suitable for studying igBPs. In addition, our method is feasible for detecting and tracking igBPs with TiO data from the NVST. With the aid of vector magnetograms obtained from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager, the properties of igBPs are found to be strongly influenced by their embedded magnetic environments. The areal coverage, size and intensity contrast values of igBPs are generally larger in regions with higher magnetic flux. However, the dynamics of igBPs, including the horizontal velocity, diffusion index, ratio of motion range and index of motion type are generally larger in the regions with lower magnetic flux. This suggests that the absence of strong magnetic fields in the medium makes it possible for the igBPs to look smaller and weaker, diffuse faster, and move faster and further along a straighter path.

  8. Do inclusive leaders help to reduce turnover in diverse groups? The moderating role of leader-member exchange in the diversity to turnover relationship.

    PubMed

    Nishii, Lisa H; Mayer, David M

    2009-11-01

    This research examines leader-member exchange (LMX) at the group level as a moderator of the relationships between demographic (i.e., race, age, gender) and tenure diversity and group turnover. Drawing primarily from LMX, social categorization, and expectation states theories, we hypothesized that through the pattern of LMX relationships that they develop with followers, group managers influence inclusion and status differentials within groups such that the positive relationship between diversity and group turnover will be weaker when the group mean on LMX is high or when group differentiation on LMX is low. Results from a sample of supermarket departments (N = 348) yielded general support for the study hypotheses. We also found evidence for a 3-way interaction involving demographic diversity, LMX mean, and LMX differentiation such that the interaction between demographic diversity and LMX differentiation was only significant when LMX mean was high. These findings highlight the important role that leaders play in influencing the relationship between diversity and turnover through the patterns of inclusion that they create in their units. PMID:19916652

  9. Anion exchange membrane

    DOEpatents

    Verkade, John G; Wadhwa, Kuldeep; Kong, Xueqian; Schmidt-Rohr, Klaus

    2013-05-07

    An anion exchange membrane and fuel cell incorporating the anion exchange membrane are detailed in which proazaphosphatrane and azaphosphatrane cations are covalently bonded to a sulfonated fluoropolymer support along with anionic counterions. A positive charge is dispersed in the aforementioned cations which are buried in the support to reduce the cation-anion interactions and increase the mobility of hydroxide ions, for example, across the membrane. The anion exchange membrane has the ability to operate at high temperatures and in highly alkaline environments with high conductivity and low resistance.

  10. TEM Study of Intergranular Fluid Distributions in Rocks at a Nanometer Scale

    NASA Astrophysics Data System (ADS)

    Hiraga, T.; Anderson, I. M.; Kohlstedt, D. L.

    2002-12-01

    The distribution of intergranular fluids in rocks plays an essential role in fluid migration and rock rheology. Structural and chemical analyses with sub-nanometer resolution is possible with transmission and scanning-transmission electron microscopy; therefore, it is possible to perform the fine-scale structural analyses required to determine the presence or absence of very thin fluid films along grain boundaries. For aqueous fluids in crustal rocks, Hiraga et al. (2001) observed a fluid morphology controlled by the relative values of the solid-solid and solid-fluid interfacial energies, which resulted in well-defined dihedral angles. Their high-resolution transmission electron microscopy (TEM) observations demonstrate that grain boundaries are tight even at a nanometer scale, consistent with the absence of aqueous fluid films. For partially molten ultra-mafic rocks, two conflicting conclusions have been reached: nanometer-thick melt films wet grain boundaries (Drury and Fitz Gerald 1996; De Kloe et al. 2000) versus essentially all grain boundaries are melt-free (Vaughan et al. 1982; Kohlstedt 1990). To resolve this conflict, Hiraga et al. (2002) examined grain boundaries in quenched partially molten peridotites. Their observations demonstrate the following: (i) Although a small fraction of the grains are separated by relatively thick (~1 μm) layers of melt, lattice fringe images obtained with a high-resolution TEM reveal that most of the remaining boundaries do not contain a thin amorphous phase. (ii) In addition, the composition of olivine-olivine grain boundaries was analyzed with a nano-beam analytical scanning TEM with a probe size of <2 nm. Although the grain boundaries contained no melt film, the concentration of Ca, Al and Ti were enhanced near the boundaries. The segregation of these elements to the grain boundaries formed enriched regions <7 nm wide. A similar pattern of chemical segregation was detected in subsolidus systems. Creep experiments on the

  11. Molecular dynamic simulations of the intergranular films between alumina and silicon nitride crystal grains

    NASA Astrophysics Data System (ADS)

    Zhang, Shenghong

    The intergranular films (IGFs) between the ceramics grains have very important effects on the structure and mechanical properties on the whole ceramics and have been studied for many decades. In the thesis, molecular dynamic (MD) computer simulations were applied to study the IGFs between the alumina and silicon nitride ceramic grains. Preferential adsorption of specific ions from the IGFs to the contacting surfaces of the alumina crystals was observed in the study of calcium-alumino-silicate glassy (CAS) IGFs formed between the combined basal and prism orientations of alpha-Al2O3 crystals. This segregation of specific ions to the interface enables formation of localized, ordered structures between the IGF and the crystals. However, the segregation behavior of the ions is anisotropic, depending on the orientation of the alpha-Al2O 3 crystals. Self-diffusion of calcium ions between these CAS IGFs was also carried out by MD simulations. The results show that the diffusion coefficients adjacent to the interfaces are smaller and the activation energies are much higher than those in the interior of the IGF and in bulk glasses. It was also suggested that Ca transport is mainly though the interior of the IGF and implies that diffusion would be significantly inhibited by sufficiently thin IGFs. The growth of the alumina ceramic grains was simulated in the contacting with IGFs containing high concentrations of aluminum ions. Five different compositions in the IGFs were studied. Results show preferential growth along the [1120] of the (1120) surface in comparison to growth along the [0001] direction on the (0001) surface for compositions near a Ca/Al ratio of 0.5. The simulations also show the mechanism by which Ca ions in the IGF inhibit growth on the basal surface. The simulations provide an atomistic view of attachment onto crystal surfaces, affecting grain growth in alumina. The dissolution of the alumina crystal grains in the silicate melts is another important issue in

  12. AN ULTRASONIC PHASED ARRAY EVALUATION OF INTERGRANULAR STRESS CORROSION CRACK (IGSCC) DETECTION IN AUSTENITIC STAINLESS STEEL PIPING WELDS

    SciTech Connect

    Diaz, Aaron A.; Anderson, Michael T.; Cinson, Anthony D.; Crawford, Susan L.; Cumblidge, Stephen E.

    2010-07-22

    Research is being conducted for the U.S. Nuclear Regulatory Commission at the Pacific Northwest National Laboratory to assess the effectiveness and reliability of advanced nondestructive examination (NDE) methods for the inspection of light water reactor (LWR) components and challenging material/component configurations. This study assessed the effectiveness of far-side inspections on wrought stainless steel piping with austenitic welds, as found in thin-walled, boiling water reactor (BWR) component configurations, for the detection and characterization of intergranular stress corrosion cracks (IGSCC).

  13. Magnetic Barkhausen Noise and Neutron Diffraction Techniques for the Study of Intergranular Residual Strains in Mild Steel

    SciTech Connect

    Hutanu, Roxana; Clapham, Lynann; Rogge, Ronald

    2004-02-26

    Intergranular residual stresses (IS) are microscopic residual stresses which have been found to accumulate along the <100> direction in steels. The <100> direction is also the magnetic easy axis direction in steel. This work involved Magnetic Barkhausen Noise (MBN) studies on steel samples, deformed uniaxially to increasing levels of strain. The MBN results indicated that a bulk magnetic easy axis was produced by the deformation process, and neutron diffraction experiments showed that this easy axis was correlated with the tensile strain in grains oriented in the <100> direction.

  14. Multi-scale modeling of microstructure dependent intergranular brittle fracture using a quantitative phase-field based method

    SciTech Connect

    Chakraborty, Pritam; Zhang, Yongfeng; Tonks, Michael R.

    2015-12-07

    In this study, the fracture behavior of brittle materials is strongly influenced by their underlying microstructure that needs explicit consideration for accurate prediction of fracture properties and the associated scatter. In this work, a hierarchical multi-scale approach is pursued to model microstructure sensitive brittle fracture. A quantitative phase-field based fracture model is utilized to capture the complex crack growth behavior in the microstructure and the related parameters are calibrated from lower length scale atomistic simulations instead of engineering scale experimental data. The workability of this approach is demonstrated by performing porosity dependent intergranular fracture simulations in UO2 and comparing the predictions with experiments.

  15. The role of Hydrogen and Creep in Intergranular Stress Corrosion Cracking of Alloy 600 and Alloy 690 in PWR Primary Water Environments ? a Review

    SciTech Connect

    Rebak, R B; Hua, F H

    2004-07-12

    Intergranular attack (IGA) and intergranular stress corrosion cracking (IGSCC) of Alloy 600 in PWR steam generator environment has been extensively studied for over 30 years without rendering a clear understanding of the essential mechanisms. The lack of understanding of the IGSCC mechanism is due to a complex interaction of numerous variables such as microstructure, thermomechanical processing, strain rate, water chemistry and electrochemical potential. Hydrogen plays an important role in all these variables. The complexity, however, significantly hinders a clearer and more fundamental understanding of the mechanism of hydrogen in enhancing intergranular cracking via whatever mechanism. In this work, an attempt is made to review the role of hydrogen based on the current understanding of grain boundary structure and chemistry and intergranular fracture of nickel alloys, effect of hydrogen on electrochemical behavior of Alloy 600 and Alloy 690 (e.g. the passive film stability, polarization behavior and open-circuit potential) and effect of hydrogen on PWSCC behavior of Alloy 600 and Alloy 690. Mechanistic studies on the PWSCC are briefly reviewed. It is concluded that further studies on the role of hydrogen on intergranular cracking in both inert and primary side environments are needed. These studies should focus on the correlation of the results obtained at different laboratories by different methods on materials with different metallurgical and chemical parameters.

  16. Experimental investigation of heat transfer augmentation inside double pipe heat exchanger equipped with reduced width twisted tapes inserts using polymeric nanofluid

    NASA Astrophysics Data System (ADS)

    Hazbehian, Mohammad; Maddah, Heydar; Mohammadiun, Hamid; Alizadeh, Mostafa

    2016-01-01

    In this study, we report a further enhancement in heat transfer coefficients of base fluid in combination with structural modifications of tape inserts. Polyvinyl Alcohol and TiO2 with mean diameter of 15 nm were chosen as base fluid and nano-particles, respectively. The experiments are carried out in plain tube with four longitudinal internal fins and reduced width twisted tape (RWTT) inserts of twist ratio varying form 2-5 and width of 12-16. Experiments are undertaken to determine heat transfer coefficients and friction factor of TiO2/PVA nanofluid up to 2.0 % volume concentration at an average temperature of 30 °C. The investigations are undertaken in the Reynolds number range of 800-30,000 for flow in tubes and with tapes of different width length ratios. The experiments was verified with well-known correlations. The average Nusselt number and friction factor in the tube fitted with the full-length twisted tapes at y/w = 3.0, and 5.0, are respectively 50-130, and 30-95 % higher than those in the plain tube; 90-220 and 100-270 % when the working fluid is nanofluid, respectively. For the reduced width twisted tapes, the heat transfer rate is decreased with decreasing tapes width. The average Nusselt numbers in the tube fitted with the RWTT of 16, 14 and 12 are respectively, 210-390, 190-320 and 170-290 % of that in the plain tube. With the similar trend mentioned above, RWTT with higher width length yield higher thermal enhancement factor in comparison with smaller width. The use of RWTT led to the highest thermal performance factor up to 1.75. Maximum thermal performance factor which was obtained belonged to twists with twist ratio of 2 and width of 16 with φ = 0.5 % and Reynolds number range of 800-30,000.

  17. Corrosion resistance of Nd-Fe-B sintered magnets with intergranular addition of Cu 60Zn 40 powders

    NASA Astrophysics Data System (ADS)

    Wu, Yeren; Ni, Junjie; Ma, Tianyu; Yan, Mi

    2010-08-01

    Cu 60Zn 40 powders, as grain boundary modifiers, were added into Nd 28.2Dy 2.0Fe balAl 0.1Nb 0.2Ga 0.11B 0.96 sintered magnets to improve the corrosion resistance of magnets. The corrosion resistance of magnets was investigated by polarization curve measurements in 3.5 wt% NaCl and 3.0 wt% NaOH solutions. It was found that the Cu 60Zn 40-added magnets had more positive corrosion potential Ecorr and much lower corrosion current density icorr than the Cu 60Zn 40-free one in both solutions, indicating the improvement of the corrosion resistance by Cu 60Zn 40 intergranular addition. Promotion of the electrochemical potential of the intergranular phase, formation of the Nd (Fe, Cu) 2 phase, the uniform distribution of the Nd-rich phase and increase of the magnet density were found to be responsible for the improvement of the corrosion resistance.

  18. Role of oxygen diffusion at Ni/Cr2O3 interface in intergranular oxidation of Ni-Cr alloy

    NASA Astrophysics Data System (ADS)

    Medasani, Bharat; Sushko, Maria; Schreiber, Daniel; Rosso, Kevin; Bruemmer, Stephen

    Certain Ni-Cr alloys used in nuclear systems experience intergranular oxidation and stress corrosion cracking when exposed to high-temperature water leading to their degradation and unexpected failure. To develop a mechanistic understanding of grain boundary oxidation processes, we proposed a mesoscale metal alloy oxidation model that combines quantum Density Functional Theory (DFT) with mesoscopic Poisson-Nernst-Planck/classical DFT. This framework encompasses the chemical specificity of elementary diffusion processes and mesoscale reactive dynamics, and allows modeling oxidation processes on experimentally relevant length scales from first principles. As a proof of concept, a preliminary model was previously employed that limited oxygen diffusion pathways to those through the oxide phase and did not allow oxygen diffusion in the alloy or across oxide/alloy interfaces. In this work, we expand the model to include oxygen diffusion pathways along Ni/Cr2O3 interfaces and demonstrate the increasing importance of such pathways for intergranular oxidation of Ni-Cr alloys with high Cr content. This work is supported by the U.S. Dept. of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. Simulations are performed using PNNL Institutional Computing facility.

  19. Elimination of intergranular corrosion susceptibility of cold-worked and sensitized AlSl 316 SS by laser surface melting

    NASA Astrophysics Data System (ADS)

    Parvathavarthini, N.; Subbarao, R. V.; Dayal, R. K.; Khatak, H. S.; Kumar, Sanjay

    2001-02-01

    Susceptibility to intergranular corrosion (IGC) and intergranular stress corrosion cracking (IGSCC) due to sensitization is one of the major problems associated with austenitic stainless steels. Thermal exposures encountered during fabrication (welding, hot working, etc.) and elevated temperature service may lead to sensitization of components of austenitic stainless steels. Laser surface melting (LSM) is an in-situ method to increase the life of a sensitized component by modifying the surface microstructure without affecting the bulk properties. In this paper, the results obtained in the attempt to improve IGC resistance of coldworked and sensitized 316 SS by LSM are presented. Type 316 SS specimens cold worked to various degrees ranging from 5 to 25% reduction in thickness and sensitized to different degrees by exposing at 898 K for different durations were laser surface melted using continuous wave (cw) CO2 laser. ASTM standard A262 practice A, optical metallography, and ASTM standard G108 were used to characterize the specimens before and after LSM. Influence of prior deformation on the desensitization behavior was evaluated for the laser melting conditions adopted during the investigation. Complete dissolution of M23C6 due to laser melting and suppression of re-precipitation due to rapid quenching result in a desensitized homogenous microstructure, which is immune to IGC. Under identical laser melting conditions, the extent of desensitization decreases with an increase in the degree of cold work, and hence, higher power levels and an extended interaction time must be adopted to homogenize the sensitized microstructure with prior cold work.

  20. Determination of the field dependence of the intergranular critical current in a YBCO tube by horizontal traversals

    NASA Astrophysics Data System (ADS)

    Çelebi, S.; LeBlanc, M. A. R.

    2006-12-01

    The magnetic flux density in the cavity of a sintered tube of Yttrium Barium Copper Oxide (YBCO) is measured as a function of H∥, the axial magnetic field impressed and removed after zero field cooling (ZFC). We note that, in a short thick-walled hollow cylinder of a weak-linked polycrystalline high- Tc superconductor, the magnetic field in the cavity of the tube, Hz hole , rises above the applied field H∥ when it is initially increasing. Consequently the standard approach to determine the critical current density from an ascending sweep of H∥ alone, or a descending sweep alone cannot be exploited. However the field dependence of the intergranular critical current density Jcm can be reliably obtained from the horizontal traversals of Hz hole vs H∥. Comparison of the experimental data with model calculations for the horizontal traversals of the hysteresis curves show that the intergranular critical current density in the YBCO tube has a Kim-like field dependence. The magnetization of the grains has a significant influence on the flux density in the cavity of the tube.

  1. Coercivity enhancement of Nd-Fe-B sintered magnets with intergranular adding (Pr, Dy, Cu)-Hx powders

    NASA Astrophysics Data System (ADS)

    Zhang, Yujing; Ma, Tianyu; Liu, Xiaolian; Liu, Pan; Jin, Jiaying; Zou, Junding; Yan, Mi

    2016-02-01

    Forming Nd2Fe14B/(Nd, Dy)2Fe14B core-shell structure by intergranular adding Dy-containing sources into Nd-Fe-B sintered magnets is effective to improve coercivity and to minimize remanence loss simultaneously. However, the excessive Dy located in the intergranular regions has nearly no hard magnetic contribution, causing its low utilization efficiency. In this work, diluted Dy powders (Pr37Dy30Cu33)-Hx were prepared and incorporated into Nd-Fe-B sintered magnets via a dual-alloy approach. The coercivity increases rapidly from 15.0 to 18.2 kOe by 21.3% with 2.0 wt% (Pr, Dy, Cu)-Hx addition (the equivalent Dy is only 0.32 at%). The deduced coercivity incremental ratio is 10.0 kOe per unit Dy at%. Dehydrogenation reaction of (Pr, Dy, Cu)-Hx occurs during sintering, which favors Dy diffusion towards the 2:14:1 phase grains as well as smoothing the grain boundaries (GBs). The enhanced local anisotropic field and the well decoupled 2:14:1 phase grains contribute to such rapid coercivity enhancement. This work suggests that adding diluted Dy hydrides is promising for fabricating high coercivity Nd-Fe-B sintered magnets with less heavy rare-earth consumption.

  2. Inter/intra granular exchange and thermal activation in nanoscale granular magnetic materials

    NASA Astrophysics Data System (ADS)

    Morrison, C.; Saharan, L.; Hrkac, G.; Schrefl, T.; Ikeda, Y.; Takano, K.; Miles, J. J.; Thomson, T.

    2011-09-01

    We explain the effect of inter/intra granular exchange coupling and thermal activation on the switching behavior of nano-scale granular magnetic materials. For an ideal, non-interacting granular system, the minimum switching field occurs at 45° from the easy axis of the grains. We show through simulation and measurements, using a CoCrPt oxide-segregated granular film as a model system, that there is a clear shift in the angle of applied field at which the minimum switching field occurs. This arises solely due to incoherent reversal induced by inter-granular exchange coupling or incoherency within larger grains, rather than thermal activation.

  3. UNDERSTANDING THE MECHANISMS CONTROLLING ENVIRONMENTALLY-ASSISTED INTERGRANULAR CRACKING OF NICKEL-BASE ALLOYS

    SciTech Connect

    Gary S. Was

    2004-02-13

    Creep and IG cracking of nickel-base alloys depend principally on two factors--the deformation behavior and the effect of the environment. We have shown that both contribute to the observed degradation in primary water. The understanding of cracking does not lie wholly within the environmental effects arena, nor can it be explained only by intrinsic mechanical behavior. Rather, both processes contribute to the observed behavior in primary water. In this project, we had three objectives: (1) to verify that grain boundaries control deformation in Ni-16Cr-9Fe at 360 C, (2) to identify the environmental effect on IGSCC, and (3) to combine CSLBs and GBCs to maximize IGSCC resistance in Ni-Cr-Fe in 360 C primary water. Experiments performed in hydrogen gas at 360 C confirm an increase in the primary creep rate in Ni-16Cr-9Fe at 360 C due to hydrogen. The creep strain transients caused by hydrogen are proposed to be due to the collapse of dislocation pile-ups, as confirmed by observations in HVEM. The observations only partially support the hydrogen-enhanced plasticity model, but also suggest a potential role of vacancies in the accelerate creep behavior in primary water. In high temperature oxidation experiments designed to examine the potential for selective internal oxidation in the IGSCC process, cracking is greatest in the more oxidizing environments compared to the low oxygen potential environments where nickel metal is stable. In Ni-Cr-Fe alloys, chromium oxides form preferentially along the grain boundaries, even at low oxygen potential, supporting a potential role in grain boundary embrittlement due to preferential oxidation. Experiments designed to determine the role of grain boundary deformation on intergranular cracking have established, for the first time, a cause-and-effect relationship between grain boundary deformation and IGSCC. That is, grain boundary deformation in Ni-16Cr-9Fe in 360 C primary water leads to IGSCC of the deformed boundaries. As well

  4. An Electrochemical Framework to Explain Intergranular Stress Corrosion Cracking in an Al-5.4%Cu-0.5%Mg-0.5%Ag Alloy

    NASA Technical Reports Server (NTRS)

    Little, D. A.; Connolly, B. J.; Scully, J. R.

    2001-01-01

    A modified version of the Cu-depletion electrochemical framework was used to explain the metallurgical factor creating intergranular stress corrosion cracking susceptibility in an aged Al-Cu-Mg-Ag alloy, C416. This framework was also used to explain the increased resistance to intergranular stress corrosion cracking in the overaged temper. Susceptibility in the under aged and T8 condition is consistent with the grain boundary Cu-depletion mechanism. Improvements in resistance of the T8+ thermal exposure of 5000 h at 225 F (T8+) compared to the T8 condition can be explained by depletion of Cu from solid solution.

  5. HEAT EXCHANGER

    DOEpatents

    Fox, T.H. III; Richey, T. Jr.; Winders, G.R.

    1962-10-23

    A heat exchanger is designed for use in the transfer of heat between a radioactive fiuid and a non-radioactive fiuid. The exchanger employs a removable section containing the non-hazardous fluid extending into the section designed to contain the radioactive fluid. The removable section is provided with a construction to cancel out thermal stresses. The stationary section is pressurized to prevent leakage of the radioactive fiuid and to maintain a safe, desirable level for this fiuid. (AEC)

  6. The role of grain boundary chemistry and structure in the environmentally-assisted intergranular cracking of nickel-base alloys. Progress report, [December 1, 1990--November 31, 1993

    SciTech Connect

    Was, G.S.

    1993-11-01

    Progress focused on (1) determination of the role of C and Cr on deformation and IG cracking behavior of Ni-(5--30)Cr-9Fe, (2) determination of the effect of grain boundary misorientation on IG cracking behavior, (3) construction of an electron backscattering pattern (EBSP) imaging system, (4) determination of effect of the environment on creep and cracking, and (5) characterization of the surface film. Results showed that both C and Cr are potent solid solution strengtheners which can reduce the steady state creep rate at 360{degree}C by several orders of magnitude. Intergranular cracking of 100 {mu}m grain samples of high purity Ni-16Cr-9Fe at 360{degree}C occurs by formation of grain boundary voids and interlinkage, driven by dislocation creep in the matrix. Creep experiments in primary water at 360{degree}C and an applied cathodic potential show that the creep rate is increased by an order of magnitude over that in Ar and the percent IG fracture increases as well. Oxide film composition and thickness is a sensitive function of the C content, increasing in thickness and Ni(OH){sub 2} content with increase in C or decrease in Cr to 5 wt%. Thermomechanical treatments along with electron channeling pattern (ECP) analysis wee used to create and index, samples with enhanced fractions of coincident site lattice boundaries (CSLBs). Constant extension rate tensile (CERT) experiments on samples with a high percentage of CSLBs showed IG cracking compared with general high angle boundaries. However, these experiments were conducted on grain sizes of 300 {mu}m, while commercial material is an order of magnitude smaller. An electron backscattering pattern imaging system has been constructed for an environmental scanning electron microscope which can image grains below {mu}m. The system has been successfully benchmarked against results from ECP analysis.

  7. Cryptographic Combinatorial Securities Exchanges

    NASA Astrophysics Data System (ADS)

    Thorpe, Christopher; Parkes, David C.

    We present a useful new mechanism that facilitates the atomic exchange of many large baskets of securities in a combinatorial exchange. Cryptography prevents information about the securities in the baskets from being exploited, enhancing trust. Our exchange offers institutions who wish to trade large positions a new alternative to existing methods of block trading: they can reduce transaction costs by taking advantage of other institutions’ available liquidity, while third party liquidity providers guarantee execution—preserving their desired portfolio composition at all times. In our exchange, institutions submit encrypted orders which are crossed, leaving a “remainder”. The exchange proves facts about the portfolio risk of this remainder to third party liquidity providers without revealing the securities in the remainder, the knowledge of which could also be exploited. The third parties learn either (depending on the setting) the portfolio risk parameters of the remainder itself, or how their own portfolio risk would change if they were to incorporate the remainder into a portfolio they submit. In one setting, these third parties submit bids on the commission, and the winner supplies necessary liquidity for the entire exchange to clear. This guaranteed clearing, coupled with external price discovery from the primary markets for the securities, sidesteps difficult combinatorial optimization problems. This latter method of proving how taking on the remainder would change risk parameters of one’s own portfolio, without revealing the remainder’s contents or its own risk parameters, is a useful protocol of independent interest.

  8. EPRI Nondestructive Evaluation Center: Assessment of the intergranular stress corrosion cracking training and qualification program: Interim report

    SciTech Connect

    Not Available

    1988-02-01

    Formal training programs for ultrasonic inspection of boiling water reactor (BWR) piping for intergranular stress-corrosion cracking (IGSCC) have been provided by the EPRI NDE Center since 1983. Separate courses are available for detection and sizing of IGSCC in unrepaired piping. A third course addresses inspection for IGSCC in piping which has been repaired by the weld overlay method. It is the policy of EPRI and EPRI NDE Center management to review these programs periodically, using both expertise internal to the NDE Center staff and from outside sources. This report provides the results of a review of the NDE Center IGSCC ultrasonic inspection training by a group of individuals who have no permanent relationshiip with the NDE Center, but who possess recognized expertise in the subject area.

  9. Multi-scale modeling of microstructure dependent intergranular brittle fracture using a quantitative phase-field based method

    DOE PAGESBeta

    Chakraborty, Pritam; Zhang, Yongfeng; Tonks, Michael R.

    2015-12-07

    In this study, the fracture behavior of brittle materials is strongly influenced by their underlying microstructure that needs explicit consideration for accurate prediction of fracture properties and the associated scatter. In this work, a hierarchical multi-scale approach is pursued to model microstructure sensitive brittle fracture. A quantitative phase-field based fracture model is utilized to capture the complex crack growth behavior in the microstructure and the related parameters are calibrated from lower length scale atomistic simulations instead of engineering scale experimental data. The workability of this approach is demonstrated by performing porosity dependent intergranular fracture simulations in UO2 and comparing themore » predictions with experiments.« less

  10. Experimental and theoretical studies of the superposition of intergranular and macroscopic strains in Ni-based industrial alloys

    SciTech Connect

    Holden, T.M.; Tome, C.N.; Holt, R.A.

    1998-12-01

    Measurements of the strain response to applied stress in polycrystalline MONEL-400 by neutron diffraction are modeled with the elastoplastic self-consistent (EPSC) theory. The strains in the different crystallographic orientations of grains, which are generated i the tensile test experiments, are shown to be caused by the anisotropy of elastic and plastic deformation with respect to crystallographic orientation. On the basis of the description of the results in the theory, the origin of a number of anomalies of a general nature in measurements by high neutron and X-ray diffraction can be understood. The theory is used to calculate which crystallographic reflections are least sensitive to intergranular effects under uniaxial tension.

  11. Study on grain boundary character and strain distribution of intergranular cracking in the CGHAZ of T23 steel

    SciTech Connect

    Jin, Y.J.; Lu, H. Yu, C.; Xu, J.J.

    2013-10-15

    Intergranular reheat cracking in the coarse-grained heat-affected zone of T23 steel was produced by strain to fracture tests on a Gleeble 3500 thermal–mechanical simulator. Then the grain boundary character, as well as the strain distribution after reheat crack propagation, was studied by electron backscatter diffraction technique. The results showed that incoherent Σ3 boundaries were seldom found on the prior austenite grain boundaries. Therefore, only the type of random high-angle boundaries played a crucial role in the intergranular cracking. Microstructurally cavities and small cracks were preferentially initiated from high-angle grain boundaries. Low-angle grain boundaries and high-angle ones with misorientation angles less than 15° were more resistant to the cracking. More importantly, the fraction of high-angle grain boundaries increased with the plastic strain induced by both temperature gradient and stress in the coarse-grained heat-affected zone, which contributed to the crack initiation and propagation. Furthermore, the strain distributions in the vicinity of cavities and cracks revealed the accommodation processes of plastic deformation during stress relaxation. It also reflected the strength differences between grain interior and grain boundary at different heat-treated temperatures, which had a large influence on the cracking mechanism. - Highlights: • The coincidence site lattice boundaries play little role in the reheat cracking. • Cavity and crack occur at high-angle grain boundaries rather than low-angle ones. • The strain leads low-angle grain boundaries to transform to high-angle ones. • Strain distribution differs for cavity and crack zones at different temperatures.

  12. 75 FR 34186 - Self-Regulatory Organizations; BATS Exchange, Inc.; EDGA Exchange, Inc.; EDGX Exchange, Inc...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-16

    ...; New York Stock Exchange LLC; NYSE Amex LLC; NYSE Arca, Inc.; The NASDAQ Stock Market LLC; Chicago.... (``NYSEArca''), The NASDAQ Stock Market LLC (``NASDAQ''), National Stock Exchange, Inc. (``NSX'') and Chicago... proposed rules may exacerbate market volatility rather than reduce it due to the interplay of stock...

  13. Microscale Regenerative Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Moran, Matthew E.; Stelter, Stephan; Stelter, Manfred

    2006-01-01

    The device described herein is designed primarily for use as a regenerative heat exchanger in a miniature Stirling engine or Stirling-cycle heat pump. A regenerative heat exchanger (sometimes called, simply, a "regenerator" in the Stirling-engine art) is basically a thermal capacitor: Its role in the Stirling cycle is to alternately accept heat from, then deliver heat to, an oscillating flow of a working fluid between compression and expansion volumes, without introducing an excessive pressure drop. These volumes are at different temperatures, and conduction of heat between these volumes is undesirable because it reduces the energy-conversion efficiency of the Stirling cycle.

  14. Optimal design of crossflow heat exchangers

    SciTech Connect

    Van den Bulck, E. )

    1991-05-01

    The design of plate-fin and tube-fin crossflow heat exchangers is discussed. The transfer surface area of crossflow heat exchangers is used ineffectively because of the nonuniform distribution of the heat transfer across the volume of the exchanger. The optimal distribution of the transfer surface area for maximum heat exchanger effectiveness and constant total surface area is determined. It is found that a Dirac delta distribution of the transfer surface aligned along the diagonal of the crossflow exchanger gives the best performance; equal to that of a counterflow device. Design guidelines for optimal area allocation within crossflow heat exchangers are established. Compared to conventional designs, designs following these guidelines may lead to either a higher exchanger effectiveness for equal pressure drops and surface area, reduced pressure drops for equal exchanger effectiveness, or reduced weight and a near cubic form of the exchanger core for equal pressure drops and effectiveness.

  15. Science exchanges

    NASA Astrophysics Data System (ADS)

    Richman, Barbara T.

    Dwindling scientific and technical exchange between the United States and the Soviet Union and prospects for enhancing such exchanges were discussed at an August 2 hearing by the Foreign Affairs Committee of the U.S. House of Representatives. The committee also heard overviews on the United States' approach to international exchange of science and technology. The hearing was the first in a series on current and future international science and technology programs.Four of eight science and technology agreements with the USSR that have expired in the last 15 months, including one on space, have not been renewed. The remaining four agreements have been extended into 1987 and 1988. Two others, including one on oceanography, are scheduled to run out in 1984.

  16. Heat exchanger

    SciTech Connect

    Drury, C.R.

    1988-02-02

    A heat exchanger having primary and secondary conduits in heat-exchanging relationship is described comprising: at least one serpentine tube having parallel sections connected by reverse bends, the serpentine tube constituting one of the conduits; a group of open-ended tubes disposed adjacent to the parallel sections, the open-ended tubes constituting the other of the conduits, and forming a continuous mass of contacting tubes extending between and surrounding the serpentine tube sections; and means securing the mass of tubes together to form a predetermined cross-section of the entirety of the mass of open-ended tubes and tube sections.

  17. Heat exchanger

    DOEpatents

    Daman, Ernest L.; McCallister, Robert A.

    1979-01-01

    A heat exchanger is provided having first and second fluid chambers for passing primary and secondary fluids. The chambers are spaced apart and have heat pipes extending from inside one chamber to inside the other chamber. A third chamber is provided for passing a purge fluid, and the heat pipe portion between the first and second chambers lies within the third chamber.

  18. Ion-exchange chromatography combined with direct current amperometric detection at CuNPs/reduced graphene oxide-chitosan composite film modified electrode for determination of monosaccharide composition of polysaccharides from Phellinus igniarius.

    PubMed

    Xi, Lingling; Wang, Fengli; Zhu, Zuoyi; Huang, Zhongping; Zhu, Yan

    2014-02-01

    A novel Cu nanoparticles/reduced graphene oxide-chitosan (CuNPs/r-GO-chitosan) composite film modified glassy carbon electrode (GCE) was fabricated by dispersing CuNPs uniformly on a stable r-GO-chitosan thin film through electrodeposition process. The modified electrode was characterized by cyclic voltammetry, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS), and exhibited efficiently electrocatalytic oxidation toward monosaccharides with high stability. The good electrocatalytic activity of this modified electrode might be attributed to the synergistic effect of r-GO and CuNPs, and the stability might be attributed to the r-GO and chitosan thin matrix film. When the CuNPs/r-GO-chitosan/GCE was used as an electrochemical sensor in high performance anion exchange chromatography-direct current amperometric detection (HPAEC-DC) flowing system for the determination of monosaccharides under constant working potential of +0.55 V, the detection limits (S/N=3) ranged from 0.006 to 0.02 mg L(-1) for the analyzed sugars, and the dynamic linear ranges spanned from 0.02 to 500 mg L(-1). The proposed method has been applied for the determination of monosaccharide composition of crude polysaccharides from phellinus igniarius real samples, and the results were satisfactory. PMID:24401438

  19. Counterflow Regolith Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Zubrin, Robert; Jonscher, Peter

    2013-01-01

    A problem exists in reducing the total heating power required to extract oxygen from lunar regolith. All such processes require heating a great deal of soil, and the heat energy is wasted if it cannot be recycled from processed material back into new material. The counterflow regolith heat exchanger (CoRHE) is a device that transfers heat from hot regolith to cold regolith. The CoRHE is essentially a tube-in-tube heat exchanger with internal and external augers attached to the inner rotating tube to move the regolith. Hot regolith in the outer tube is moved in one direction by a right-hand - ed auger, and the cool regolith in the inner tube is moved in the opposite direction by a left-handed auger attached to the inside of the rotating tube. In this counterflow arrangement, a large fraction of the heat from the expended regolith is transferred to the new regolith. The spent regolith leaves the heat exchanger close to the temperature of the cold new regolith, and the new regolith is pre-heated close to the initial temperature of the spent regolith. Using the CoRHE can reduce the heating requirement of a lunar ISRU system by 80%, reducing the total power consumption by a factor of two. The unique feature of this system is that it allows for counterflow heat exchange to occur between solids, instead of liquids or gases, as is commonly done. In addition, in variants of this concept, the hydrogen reduction can be made to occur within the counterflow heat exchanger itself, enabling a simplified lunar ISRU (in situ resource utilization) system with excellent energy economy and continuous nonbatch mode operation.

  20. Evaluation by the Double Loop Electrochemical Potentiokinetic Reactivation Test of Aged Ferritic Stainless Steel Intergranular Corrosion Susceptibility

    NASA Astrophysics Data System (ADS)

    Sidhom, H.; Amadou, T.; Braham, C.

    2010-12-01

    An experimental design method was used to determine the effect of factors that significantly affect the response of the double loop-electrochemical potentiokinetic reactivation (DL-EPR) test in controlling the susceptibility to intergranular corrosion (IGC) of UNS S43000 (AISI 430) ferritic stainless steel. The test response is expressed in terms of the reactivation/activation current ratio ( I r / I a pct). Test results analysed by the analysis of variance (ANOVA) method show that the molarity of the H2SO4 electrolyte and the potential scanning rate have a more significant effect on the DL-EPR test response than the temperature and the depassivator agent concentration. On the basis of these results, a study was conducted in order to determine the optimal operating conditions of the test as a nondestructive technique for evaluating IGC resistance of ferritic stainless steel components. Three different heat treatments are considered in this study: solution annealing (nonsensitized), aging during 3 hours at 773 K (500 °C) (slightly sensitized), and aging during 2 hours at 873 K (600 °C) (highly sensitized). The aim is to find the operating conditions that simultaneously ensure the selectivity of the attack (intergranular and chromium depleted zone) and are able to detect the effect of low dechromization. It is found that a potential scanning rate of 2.5 mV/s in an electrolyte composed of H2SO4 3 M solution without depassivator, at a temperature around 293 K (20 °C), is the optimal operating condition for the DL-EPR test. Using this condition, it is possible to assess the degree of sensitization (DOS) to the IGC of products manufactured in ferritic stainless steels rapidly, reliably, and quantitatively. A time-temperature-start of sensitization (TTS) diagram for the UNS S43000 (France Inox, Villepinte, France) stainless steel was obtained with acceptable accuracy by this method when the IGC sensitization criterion was set to I r / I a > 1 pct. This diagram is in

  1. Simulating Intergranular Stress Corrosion Cracking in AZ31 Using Three-Dimensional Cohesive Elements for Grain Structure

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Chen, Z. H.; Dong, C. F.

    2015-12-01

    In this study, a grain boundary model with three-dimensional (3D) cohesive elements for analyzing the intergranular stress corrosion cracking (IGSCC) on the crystal level in polycrystalline materials is presented. The objectives are to characterize the grain boundary microstructure and the fracture mechanism of IGSCC in AZ31 Mg alloy. In order to investigate the development of the microcrack and its effects on macrocrack evolution, a novel model of IGSCC propagation has been developed, in which the 3D Voronoi tessellations geometry is employed to model polycrystalline grain structures. And the 3D cohesive elements with zero constitutive thickness are directly inserted on the faces of two adjacent grains. The effect of the embrittlement due to the presence of hydrogen has also been included in the cohesive model. To validate the model, an IGSCC process of AZ31 Mg alloy in NaCl solution has been simulated, with the influence of hydrogen concentration being taken into account. It is found that damage develops at the triple lines between the grains and the combinations of grains can lead to high stresses at the grains boundary, especially those that are normal to the direction of the applied strain. In this paper, the effects of damage due to hydrogen and the grain sizes in microstructure are considered. The simulation results have a good consistency with the experimental phenomenon.

  2. A Collector Plate Mechanism-Based Classical Intergranular Precipitation Model for Al Alloys Sensitized at Different Temperatures

    NASA Astrophysics Data System (ADS)

    Yi, Gaosong; Derrick, Alexander T.; Zhu, Yakun; Free, Michael L.

    2015-11-01

    The sensitization behavior of Al 5xxx alloys is mainly caused by the formation of Mg-rich precipitates at grain boundaries. In this study, a classical nucleation-growth-coarsening theory for the description of intergranular precipitation is formulated, which adopts a collector plate mechanism, an equivalent average Mg concentration at the grain boundary, and new coarsening mechanisms. Three coarsening mechanisms, the modified Lifshitz-Slyozov-Wagner, the Kirchner mechanism, and a combination of these two mechanisms, are compared. Modeling results reveal that the Kirchner mechanism will breakdown when continuity ( √ {Nπ R2 } ) is close to 1. According to the new model, the coarsening still accounts for a small fraction (only 10 pct) in the final growth rate after aging at 343 K (70 °C) for 40 months, which is confirmed by the precipitate size distribution data. Thickness and continuity results predicted by the new model agree well with the experimental results obtained from scanning transmission electron microscopy images of Al 5083 H131 alloys aged at 343 K (70 °C) for different times. In addition, the new model is also applied to a high-temperature [453 K (180 °C)] situation, where coarsening of precipitates is observed.

  3. Intergranular Corrosion Behavior of 304LN Stainless Steel Heat Treated at 623 K (350 °C)

    NASA Astrophysics Data System (ADS)

    Singh, Raghuvir; Kumar, Mukesh; Ghosh, Mainak; Das, Gautam; Singh, P. K.; Chattoraj, I.

    2013-01-01

    Low temperature sensitization of 304LN stainless steel from the two pipes, differing slightly in chemical composition, has been investigated; specimens were aged at 623 K (350 °C) for 20,000 hours and evaluated for intergranular corrosion and degree of sensitization. The base and heat-affected zone (HAZ) of the 304LN-1 appear resistant to sensitization, while 304LN-2 revealed a "dual" type microstructure at the transverse section and HAZ. The microstructure at 5.0-mm distance from the fusion line indicates qualitatively less sensitization as compared to that at 2.0 mm. The 304LN-2 base alloy shows overall lower degree of sensitization values as compared to the 304LN-1. A similar trend of degree of sensitization was observed in the HAZ where it was higher in the 304LN-1 as compared to the 304LN-2. The weld zone of both the stainless steels suffered from cracking during ASTM A262 practice E, while the parent metals and HAZs did not show such fissures. A mottled image within the ferrite lamella showed spinodal decomposition. The practice E test and transmission electron microscopy results indicate that the interdendritic regions may suffer from failure due to carbide precipitation and due to the evolution of brittle phase from spinodal decomposition.

  4. OBSERVATIONS AND IMPLICATIONS OF INTERGRANULAR STRESS CORROSION CRACK GROWTH OF ALLOY 152 WELD METALS IN SIMULATED PWR PRIMARY WATER

    SciTech Connect

    Toloczko, Mychailo B.; Olszta, Matthew J.; Overman, Nicole R.; Bruemmer, Stephen M.

    2013-08-15

    Significant intergranular (IG) crack growth during stress corrosion cracking (SCC) tests has been documented during tests in simulated PWR primary water on two alloy 152 specimens cut from a weldment produced by ANL. The cracking morphology was observed to change from transgranular (TG) to mixed mode (up to ~60% IG) during gentle cycling and cycle + hold loading conditions. Measured crack growth rates under these conditions often suggested a moderate degree of environmental enhancement consistent with faster growth on grain boundaries. However, overall SCC propagation rates at constant stress intensity (K) or constant load were very low in all cases. Initial SCC rates up to 6x10-9 mm/s were occasionally measured, but constant K/load growth rates dropped below ~1x10-9 mm/s with time even when significant IG engagement existed. Direct comparisons were made among loading conditions, measured crack growth response and cracking morphology during each test to assess IGSCC susceptibility of the alloy 152 specimens. These results were analyzed with respect to our previous SCC crack growth rate measurements on alloy 152/52 welds.

  5. Grain boundary composition and intergranular fracture of steels. Volume 1: Detection of grain boundary segregation in steels

    NASA Astrophysics Data System (ADS)

    Bruemmer, S. M.; Charlot, L. A.; Thomas, M. T.; Jones, R. H.

    1985-01-01

    Several alternative techniques for the measurement of grain boundary composition in iron-base alloys were evaluated, including Secondary Ion Mass Spectroscopy (SIMS), Analytical Electron Microscopy (AEM), and chemical/electrochemical etching. Potential problems in grain boundary composition measurements of CrMoV and NiCrMoV steels by AES were identified as a result of AES, high-resolution AES, and AEM characterization. Significant differences were identified in comparing peak height ratios on identical specimens using PHI 545, 560, and 595 systems. These differences were due to instrument parameters that are generally not known for any particular AES system. Localized ductile tearing regions and the presence of second phase particles on intergranular faces exposed by fracture led to significant point to point composition varitions. Phosphorus levels varied by more than 50% across individual grain boundary facets. Copper-tin intermetallics were observed by AEM in the CrMoV steel and nickel-tin intermetallics in the NiCrMoV steel. Much of the tin documented by AES at grain boundaries could be explained by the presence of these small intermetallic precipitates.

  6. High-resolution comparison of primary- and secondary-side intergranular degradation in alloy 600 steam generator tubing

    SciTech Connect

    Bruemmer, Stephen M.; Guertsman, Valery Y.; Thomas, Larry E.

    2000-01-01

    Abstract Intergranular (IG) attack and stress-corrosion cracks in alloy 600 tubing removed from the PWR steam generator #1 at Ringhals 2 have been characterized by analytical transmission electron microscopy (ATEM). Comparisons are made between environmentally induced cracks initiated on the primary-water ID surface versus those initiated on the secondary-water OD surface. General SCC crack morphologies were quite similar with branched IG cracking extending to approximately 50% through wall. Corrosion products in the open cracks were quite different with hydrated nickel phosphate seen filling the secondary-side crack, while the crack wall oxide in the primary-side crack was a Cr and Fe-rich spinel. Both samples revealed narrow (~10-nm wide), deeply penetrated, oxidized zones along most grain boundaries that intersect the open cracks. The local structures and chemistries in these corrosion-affected zones were examined by high-resolution TEM imaging, electron diffraction and fine-probe compositional analysis. These porous IG penetrations were nearly identical in appearance for both the primary- and secondary-side examples and contained Cr-rich oxides (Cr2O3 on the primary side and spinel plus Cr2O3 on the secondary side). Similarities between corrosion-induced structures for primary- and secondary-side cracking may indicate that the same degradation mechanism is operating in both cases. However, controlled experiments are needed where specific mechanisms can be properly distinguished.

  7. Heat exchanger performance monitoring guidelines

    SciTech Connect

    Stambaugh, N. ); Closser, W. Jr. ); Mollerus, F.J. )

    1991-12-01

    Fouling can occur in many heat exchanger applications in a way that impedes heat transfer and fluid flow and reduces the heat transfer or performance capability of the heat exchanger. Fouling may be significant for heat exchanger surfaces and flow paths in contact with plant service water. This report presents guidelines for performance monitoring of heat exchangers subject to fouling. Guidelines include selection of heat exchangers to monitor based on system function, safety function and system configuration. Five monitoring methods are discussed: the heat transfer, temperature monitoring, temperature effectiveness, delta P and periodic maintenance methods. Guidelines are included for selecting the appropriate monitoring methods and for implementing the selected methods. The report also includes a bibliography, example calculations, and technical notes applicable to the heat transfer method.

  8. B2O3: Grain boundary material for high-K u CoPt–oxide granular media with low degree of intergranular exchange coupling

    NASA Astrophysics Data System (ADS)

    Kong Tham, Kim; Hinata, Shintaro; Kushibiki, Ryosuke; Saito, Shin

    2016-07-01

    The magnetic properties and structures of Co80Pt20–30 vol % oxide (ZrO2, Cr2O3, Y2O3, Al2O3, MnO, TiO2, WO2, SiO2, Mn3O4, WO3, Co3O4, MoO3, and B2O3) granular media deposited at room temperature were investigated. As a result, the following were found. 1) By employing oxides with low melting point temperatures as the granular media, magnetic grains with high saturation magnetization (M\\text{s}\\text{grain}) and perpendicular magnetic anisotropy (K\\text{u}\\text{grain}) are obtained; the increases in M\\text{s}\\text{grain} and K\\text{u}\\text{grain} are due to the promotion of the columnar growth of magnetic grains and phase separation or two-phase precipitation between magnetic grains and oxides. 2) The increase in the K\\text{u}\\text{grain} of the granular media followed by the decrease in the melting point of oxides is due to the reduction in the amount of stacking faults. 3) Among these granular media, the CoPt–B2O3 granular medium has the highest coercivity (H c) and ratio of H c to the magnetic anisotropy field (H\\text{c}/H\\text{k}\\text{grain}) of 8.0 kOe and 0.4, with M\\text{s}\\text{grain} and K\\text{u}\\text{grain} of 1115 emu/cm3 and 1.1 × 107 erg/cm3, respectively. 4) The CoPt–B2O3 granular medium has well-isolated and columnar growth magnetic grains with an average grain size of 6.5 nm.

  9. Heat exchanger

    DOEpatents

    Brackenbury, Phillip J.

    1986-04-01

    A heat exchanger comparising a shell attached at its open end to one side of a tube sheet and a detachable head connected to the other side of said tube sheet. The head is divided into a first and second chamber in fluid communication with a nozzle inlet and nozzle outlet, respectively, formed in said tube sheet. A tube bundle is mounted within said shell and is provided with inlets and outlets formed in said tube sheet in communication with said first and second chambers, respectively.

  10. Use of Slow Strain Rate Tensile Testing to Assess the Ability of Several Superalloys to Resist Environmentally-Assisted Intergranular Cracking

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; Telesman, Jack; Banik, Anthony; McDevitt, Erin

    2014-01-01

    Intergranular fatigue crack initiation and growth due to environmental degradation, especially at notched features, can often limit the fatigue life of disk superalloys at high temperatures. For clear comparisons, the effects of alloy composition on cracking in air needs to be understood and compared separately from variables associated with notches and cracks such as effective stress concentration, plastic flow, stress relaxation, and stress redistribution. The objective of this study was to attempt using simple tensile tests of specimens with uniform gage sections to compare the effects of varied alloy composition on environment-assisted cracking of several powder metal and cast and wrought superalloys including ME3, LSHR, Udimet 720(TradeMark) ATI 718Plus(Registered TradeMark) alloy, Haynes 282(Trademark), and Inconel 740(TradeMark) Slow and fast strain-rate tensile tests were found to be a useful tool to compare propensities for intergranular surface crack initiation and growth. The effects of composition and heat treatment on tensile fracture strain and associated failure modes were compared. Environment interactions were determined to often limit ductility, by promoting intergranular surface cracking. The response of various superalloys and heat treatments to slow strain rate tensile testing varied substantially, showing that composition and microstructure can significantly influence environmental resistance to cracking.

  11. Effect of the heating of the intergranular water on the softening of a shear band

    NASA Astrophysics Data System (ADS)

    Galindo, S. A.; Munoz, J. D.; Lizcano, A.

    2009-06-01

    When a landslide takes place, it is believed that a shear band of loose granular media acts as a lubricant between the descending block of soil and the basis on repose. The mechanism involved is known as softening: the granular skeleton looses its stiffness and the shear stress on the block is lost. In the hypothesis of Habib, the friction between grains heats the pore water, increasing its pressure and reducing the effective stress by the Terzagi criterion. Vardoulakis had constructed models on this hypothesis including thermal diffusion and Darcy's law, plus a double dependence of the friction angle on the displacement and the velocity of the rolling block. Hereby we present a discrete element simulation of the process on a tilted shear band between two soil blocks: one bottom at rest and one upper at move. Soil blocks are assumed with uniform permeability and thermal conductivity. The shear band is modeled as a set of Voronoi polygons with elastic, frictional and damping forces between them. Pore water acts with hydrostatic pressure on the grains and on the upper and lower blocks, with a thermodynamic response that is reproduced by the Steam Tables provided by the International Association for the Properties of Water and Steam (IAPWS 97 report). At each time step, the forces on all grains are computed and all translational and rotational movements are integrated. Then, the heat is computed as the work done by all dissipative forces, distributing between water and grains according to their thermal capacities and increasing water temperature and pressure. Finally, this water pressure pushes the grains apart, reducing the shear stress on the upper block and speeding up the landslide. By this simulation procedure we obtain temperature increments on 10 C° that are strong enough to produce softening. Although the model is in two dimensions, it provides new insights on the study of catastrophic landslides evolutions.

  12. Vitrification of ion exchange resins

    DOEpatents

    Cicero-Herman, Connie A.; Workman, Rhonda Jackson

    2001-01-01

    The present invention relates to vitrification of ion exchange resins that have become loaded with hazardous or radioactive wastes, in a way that produces a homogenous and durable waste form and reduces the disposal volume of the resin. The methods of the present invention involve directly adding borosilicate glass formers and an oxidizer to the ion exchange resin and heating the mixture at sufficient temperature to produce homogeneous glass.

  13. Atomistically derived cohesive zone model of intergranular fracture in polycrystalline graphene

    NASA Astrophysics Data System (ADS)

    Guin, Laurent; Raphanel, Jean L.; Kysar, Jeffrey W.

    2016-06-01

    Pristine single crystal graphene is the strongest known two-dimensional material, and its nonlinear anisotropic mechanical properties are well understood from the atomic length scale up to a continuum description. However, experiments indicate that grain boundaries in the polycrystalline form reduce the mechanical behavior of polycrystalline graphene. Herein, we perform atomistic-scale molecular dynamics simulations of the deformation and fracture of graphene grain boundaries and express the results as continuum cohesive zone models (CZMs) that embed notions of the grain boundary ultimate strength and fracture toughness. To facilitate energy balance, we employ a new methodology that simulates a quasi-static controlled crack propagation which renders the kinetic energy contribution to the total energy negligible. We verify good agreement between Griffith's critical energy release rate and the work of separation of the CZM, and we note that the energy of crack edges and fracture toughness differs by about 35%, which is attributed to the phenomenon of bond trapping. This justifies the implementation of the CZM within the context of the finite element method (FEM). To enhance computational efficiency in the FEM implementation, we discuss the use of scaled traction-separation laws (TSLs) for larger element sizes. As a final result, we have established that the failure characteristics of pristine graphene and high tilt angle bicrystals differ by less than 10%. This result suggests that one could use a unique or a few typical TSLs as a good approximation for the CZMs associated with the mechanical simulations of the polycrystalline graphene.

  14. Hartree potential dependent exchange functional.

    PubMed

    Constantin, Lucian A; Fabiano, Eduardo; Della Sala, Fabio

    2016-08-28

    We introduce a novel non-local ingredient for the construction of exchange density functionals: the reduced Hartree parameter, which is invariant under the uniform scaling of the density and represents the exact exchange enhancement factor for one- and two-electron systems. The reduced Hartree parameter is used together with the conventional meta-generalized gradient approximation (meta-GGA) semilocal ingredients (i.e., the electron density, its gradient, and the kinetic energy density) to construct a new generation exchange functional, termed u-meta-GGA. This u-meta-GGA functional is exact for the exchange of any one- and two-electron systems, is size-consistent and non-empirical, satisfies the uniform density scaling relation, and recovers the modified gradient expansion derived from the semiclassical atom theory. For atoms, ions, jellium spheres, and molecules, it shows a good accuracy, being often better than meta-GGA exchange functionals. Our construction validates the use of the reduced Hartree ingredient in exchange-correlation functional development, opening the way to an additional rung in the Jacob's ladder classification of non-empirical density functionals. PMID:27586907

  15. Inhibitory effect of boric acid on intergranular attack and stress corrosion cracking of Alloy 600 in high temperature water

    SciTech Connect

    Kawamura, H.; Hirano, H.; Koike, M.; Suda, M.

    1995-09-01

    The inhibitory effect of boric acid on the Intergranular Attack and Stress Corrosion Cracking (IGA/SCC) propagation behavior of steam generator (SG) tubing was studied under accelerated test conditions. Based on the analysis results of stress intensity factors at IGA/SCC crack tips, the notched C-ring tests were carried out to evaluate the effect of stress intensity and boric acid on the IGA/SCC crack propagation. The A.C. impedance measurement and Auger electron spectroscopy (AES) were also conducted to clarify the inhibitory effect of boric acid. Notched C-ring test results indicated that IGA/SCC crack velocity of alloy 600 increased gradually with increasing stress intensity factor in the range 4 to about 26 MPa{center_dot}m{sup 1/2}, which might be loaded on the IGA/SCC crack tips of actual SG tubes under PWR secondary conditions. Adding boric acid slightly retarded the crack velocity in both all volatile treatment (AVT) water and caustic solutions. IGA/SCC crack velocities were lower in nearly neutral solutions than in alkali or acidic solutions. Furthermore, A.C. impedance studies showed that the polarization resistances of oxide films formed in boric acid solutions were higher than those of films formed in acidic and alkali solutions. AES analysis revealed that boron content in the oxide films formed in acidic solution containing boric acid was lowest. Good agreement was obtained between the IGA/SCC inhibitory effect of boric acid and the formation of the stable oxide films containing boron.

  16. High-Resolution Characterization of Intergranular Attack and Stress Corrosion Cracking of Alloy 600 in High-Temperature Primary Water

    SciTech Connect

    Thomas, Larry E.; Bruemmer, Stephen M.

    2000-06-01

    Intergranular (IG) attack regions and stress-corrosion cracks in alloy 600 U-bend samples tested in 330C, pressurized-water-reactor water have been characterized by analytical transmission electron microscopy (ATEM). Observations of cross-sectional samples revealed short oxidized zones preceding crack tips and narrow (10-nm wide), deeply penetrated, oxidized zones along grain boundaries exposed along open cracks. High-resolution TEM imaging and fine-probe analysis were used to determine the local chemistries and structures in these corrosion-affected zones. Matrix areas surrounding the crack tips appeared highly strained, whereas the IG penetrations generally did not. The predominant oxide structure found along crack walls and just ahead of crack tips was NiO with metal-atom ratios similar to the alloy. The attacked grain boundaries off open cracks contained similar fine-grained NiO-structure oxide together with local areas of Cr-rich oxide and Ni-rich metal. In contrast, Cr-rich oxide identified as Cr2O3 predominated at the leading edges of the IG attack. Stereoscopic imaging of these tip structures revealed nm-scale porosity and tunnels within the oxide and pores along the grain-boundary plane ahead of the oxide. The general interpretation of these results is that IG attack and cracking follows local dissolution or oxidation and the formation of pores at grain boundaries. This degradation occurs at the nanometer scale and therefore requires high-resolution ATEM methods to reveal detailed characteristics. Experimental support for several possible IG degradation mechanisms is considered.

  17. Effect of Shot Peening on the Intergranular Corrosion Susceptibility of a Novel Super304H Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Wang, Rui Kun; Zheng, Zhi Jun; Gao, Yan

    2016-01-01

    The surface phase constituent of Super304H austenitic stainless steel, after shot peening and sensitization treatment at 600, 650, and 700 °C for 2 h, was characterized using x-ray diffraction method. The degree of sensitization (DOS) was investigated by means of double-loop electrochemical potentiokinetic reactivation (DL-EPR) test, and the morphology after DL-EPR test was observed by scanning electron microscopy (SEM). The results showed that nano-sized grains and strain-induced martensite together with compressive residual stress formed on the surface of Super304H steel after shot peening. Surface compressive residual stresses relaxed greatly after being sensitized at 600-700 °C for 2 h, and no systematic correlation was observed between the compressive residual stresses developed and the intergranular corrosion susceptibility (IGCS). Because of the occurrence of strain-induced martensite in the shot-peened specimens, their IGCS is much higher than that of the as-received specimen when being sensitized at 600-650 °C for 2 h. Besides, the DOS increased with the increasing of shot peening time and the content of strain-induced martensite. On the contrary, the IGCS of Super304H stainless steels subjected to shot peening was eliminated when being sensitized at 700 °C for 2 h because of the reverse transformation of strain-induced martensite and faster diffusion rate of Cr at higher temperature in ultrafine-grained austenite which had helped healing the chromium depletion zone in a very short time. In a word, shot peening promoted desensitization of Super304H steel in a time shorter than 2 h at higher temperature up to 700 °C.

  18. Resistive and magnetoresistive properties of compacted CrO2 powders with different types of intergranular dielectric layers

    NASA Astrophysics Data System (ADS)

    Dalakova, N. V.; Belevtsev, B. I.; Beliayev, E. Yu.; Bludov, A. N.; Pashchenko, V. N.; Osmolovsky, M. G.; Osmolovskaya, O. M.

    2012-12-01

    Resistive, magnetoresistive and magnetic properties of four types of pressed CrO2 powders synthesized from chromic anhydride by the hydrothermal method were investigated. The new synthesis method allowed controlling the thickness of dielectric shells. The powders consisted of rounded particles (≈120 nm in dia.) or acicular crystals (≈22.9 nm in dia. and 302 nm in length). The particles were covered with a surface dielectric shell of different thickness and type (e.g. β-CrOOH oxyhydroxide or chromium oxide Cr2O3). The influence of the properties and the thickness of intergranular dielectric layers as well as the shape of CrO2 particles on the tunneling resistance and magnetoresistance (MR) of the pressed powders was studied. It was found that at low temperatures all the investigated samples displayed a nonmetallic temperature dependence of resistance and a giant negative MR. The maximal values of MR at T ≈ 5 K were found to be approx. 37% in relatively low magnetic fields (0.5 T). The MR decreased rapidly with increasing temperature (down to approx. 1% in 1 T at T ≈ 200 K). At low temperatures the powders with acicular particles exhibited a new type of MR hysteresis and nonmonotonous dependence of MR with increasing magnetic field. A nonmonotonous temperature dependence Hp(T), where Hp is the field in which the resistance is maximal, mismatch between the values of Hp and coercive force Hc, and the anisotropy of MR as a function of mutual orientation of transport current and magnetic field were observed.

  19. Segmented heat exchanger

    DOEpatents

    Baldwin, Darryl Dean; Willi, Martin Leo; Fiveland, Scott Byron; Timmons, Kristine Ann

    2010-12-14

    A segmented heat exchanger system for transferring heat energy from an exhaust fluid to a working fluid. The heat exchanger system may include a first heat exchanger for receiving incoming working fluid and the exhaust fluid. The working fluid and exhaust fluid may travel through at least a portion of the first heat exchanger in a parallel flow configuration. In addition, the heat exchanger system may include a second heat exchanger for receiving working fluid from the first heat exchanger and exhaust fluid from a third heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the second heat exchanger in a counter flow configuration. Furthermore, the heat exchanger system may include a third heat exchanger for receiving working fluid from the second heat exchanger and exhaust fluid from the first heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the third heat exchanger in a parallel flow configuration.

  20. Intergranular tellurium cracking of nickel-based alloys in molten Li, Be, Th, U/F salt mixture

    NASA Astrophysics Data System (ADS)

    Ignatiev, Victor; Surenkov, Alexander; Gnidoy, Ivan; Kulakov, Alexander; Uglov, Vadim; Vasiliev, Alexander; Presniakov, Mikhail

    2013-09-01

    , and intergranular corrosion does not take place. In the fuel salt with [U(IV)]/[U(III)] = 4-20 the potentials of uranium alloy formation with the main components of the tested alloys are not reached, that's why alloys and intermetallic compounds are not formed on the surface of the investigated chromium-nickel alloys. Under such conditions any intergranular tellurium corrosion of the selected alloys does not occur. In the fuel salt with [U(IV)/]/[U(III)] = 100 the potentials of uranium alloy formation with the main components of the tested alloys are not also reached. Under such redox conditions any traces intergranular tellurium IGC on the HN80MTY and H80M-VI alloys specimens are not found. Certain signs of incipient IGC in the form of tellurium presence on the grain boundaries in the HN80MTB and EM-721 alloys surface layer and formation of not too deep cracks on HN80MTB alloy surface were revealed at [U(IV)/]/[U(III)] = 100. With this uranium ratio in the presence of corrosion products on the surface of all of the alloys films, containing tellurium, metals of the construction alloys and carbon, are formed. In the melt with [U(IV)]/[U(III)] = 500 in all of the alloys tested the tellurium IGC took place. The HN80MTY alloy shows the maximum resistance to tellurium IGC. The intensity of tellurium IGC of the alloy (the K parameter) is by 3-5 times lower as compared to other alloys. The EM-721 alloy has the minimal resistance to tellurium IGC (K = 9200 pc m/cm, the depth of cracks is up to 434 μm). The studies have shown, that the intensity of the nickel alloys IGC is controlled by the [U(IV)]/[U(III)] ratio, and its dependence on this parameter is of threshold character. Providing the uranium ratio value's monitoring and regulation, it is possible to control the tellurium corrosion and in such a way to eliminate IGC completely or to minimize its value. The alloys strength characteristics and their structure were changed insignificantly after testing within the [U

  1. Educator Exchange Resource Guide.

    ERIC Educational Resources Information Center

    Garza, Cris; Rodriguez, Victor

    This resource guide was developed for teachers and administrators interested in participating in intercultural and international exchange programs or starting an exchange program. An analysis of an exchange program's critical elements discusses exchange activities; orientation sessions; duration of exchange; criteria for participation; travel,…

  2. Relating Ab Initio Mechanical Behavior of Intergranular Glassy Films in Γ-Si3N4 to Continuum Scales

    NASA Astrophysics Data System (ADS)

    Ouyang, L.; Chen, J.; Ching, W.; Misra, A.

    2006-05-01

    Nanometer thin intergranular glassy films (IGFs) form in polycrystalline ceramics during sintering at high temperatures. The structure and properties of these IGFs are significantly changed by doping with rare earth elements. We have performed highly accurate large-scale ab initio calculations of the mechanical properties of both undoped and Yittria doped (Y-IGF) model by theoretical uniaxial tensile experiments. Uniaxial strain was applied by incrementally stretching the super cell in one direction, while the other two dimensions were kept constant. At each strain, all atoms in the model were fully relaxed using Vienna Ab initio Simulation Package VASP. The relaxed model at a given strain serves as the starting position for the next increment of strain. This process is carried on until the total energy (TE) and stress data show that the "sample" is fully fractured. Interesting differences are seen between the stress-strain response of undoped and Y-doped models. For the undoped model, the stress-strain behavior indicates that the initial atomic structure of the IGF is such that there is negligible coupling between the x- and the y-z directions. However, once the behavior becomes non- linear the lateral stresses increase, indicating that the atomic structure evolves with loading [1]. To relate the ab initio calculations to the continuum scales we analyze the atomic-scale deformation field under this uniaxial loading [1]. The applied strain in the x-direction is mostly accommodated by the IGF part of the model and the crystalline part experiences almost negligible strain. As the overall strain on the sample is incrementally increased, the local strain field evolves such that locations proximal to the softer spots attract higher strains. As the load progresses, the strain concentration spots coalesce and eventually form persistent strain localization zone across the IGF. The deformation pattern obtained through ab initio calculations indicates that it is possible to

  3. Corrosive resistant heat exchanger

    DOEpatents

    Richlen, Scott L.

    1989-01-01

    A corrosive and errosive resistant heat exchanger which recovers heat from a contaminated heat stream. The heat exchanger utilizes a boundary layer of innocuous gas, which is continuously replenished, to protect the heat exchanger surface from the hot contaminated gas. The innocuous gas is conveyed through ducts or perforations in the heat exchanger wall. Heat from the heat stream is transferred by radiation to the heat exchanger wall. Heat is removed from the outer heat exchanger wall by a heat recovery medium.

  4. Advanced heat exchanger development for molten salts

    SciTech Connect

    Sabharwall, Piyush; Clark, Denis; Glazoff, Michael; Zheng, Guiqiu; Sridharan, Kumar; Anderson, Mark

    2014-12-01

    This study addresses present work concerned with advanced heat exchanger development for molten salt in nuclear and non nuclear thermal systems. The molten salt systems discussed herein use alloys, such as Hastelloy N and 242, which show corrosion resistance to molten salt at nominal operating temperatures up to 700°C. These alloys were diffusion welded, and the corresponding information is presented. Test specimens were prepared for exposing diffusion welds to molten salt environments. Hastelloy N and 242 were found to be weldable by diffusion welding, with ultimate tensile strengths about 90% of base metal values. Both diffusion welds and sheet material in Hastelloy N were corrosion tested in?58 mol% KF and 42 mol% ZrF4 at 650, 700, and 850°C for 200, 500, and 1,000 hours. Corrosion rates found were similar between welded and nonwelded materials, typically <10 mils per year. For materials of construction, nickel and alloys with dense nickel coatings are effectively inert to corrosion in fluorides, but not so in chlorides. Hence, additional testing of selected alloys for resistance to intergranular corrosion is needed, as is a determination of corrosion rate as a function of contaminant type and alloy composition with respect to chromium and carbon to better define the optimal chromium and carbon composition, independent of galvanic or differential solubility effects. Also presented is the division of the nuclear reactor and high temperature components per ASME standards, along with design requirements for a subcritical Rankine power cycle heat exchanger that has to overcome pressure difference of about 17 MPa.

  5. Advanced heat exchanger development for molten salts

    DOE PAGESBeta

    Sabharwall, Piyush; Clark, Denis; Glazoff, Michael; Zheng, Guiqiu; Sridharan, Kumar; Anderson, Mark

    2014-12-01

    This study addresses present work concerned with advanced heat exchanger development for molten salt in nuclear and non nuclear thermal systems. The molten salt systems discussed herein use alloys, such as Hastelloy N and 242, which show corrosion resistance to molten salt at nominal operating temperatures up to 700°C. These alloys were diffusion welded, and the corresponding information is presented. Test specimens were prepared for exposing diffusion welds to molten salt environments. Hastelloy N and 242 were found to be weldable by diffusion welding, with ultimate tensile strengths about 90% of base metal values. Both diffusion welds and sheet materialmore » in Hastelloy N were corrosion tested in?58 mol% KF and 42 mol% ZrF4 at 650, 700, and 850°C for 200, 500, and 1,000 hours. Corrosion rates found were similar between welded and nonwelded materials, typically <10 mils per year. For materials of construction, nickel and alloys with dense nickel coatings are effectively inert to corrosion in fluorides, but not so in chlorides. Hence, additional testing of selected alloys for resistance to intergranular corrosion is needed, as is a determination of corrosion rate as a function of contaminant type and alloy composition with respect to chromium and carbon to better define the optimal chromium and carbon composition, independent of galvanic or differential solubility effects. Also presented is the division of the nuclear reactor and high temperature components per ASME standards, along with design requirements for a subcritical Rankine power cycle heat exchanger that has to overcome pressure difference of about 17 MPa.« less

  6. Skew chicane based betatron eigenmode exchange module

    DOEpatents

    Douglas, David

    2010-12-28

    A skewed chicane eigenmode exchange module (SCEEM) that combines in a single beamline segment the separate functionalities of a skew quad eigenmode exchange module and a magnetic chicane. This module allows the exchange of independent betatron eigenmodes, alters electron beam orbit geometry, and provides longitudinal parameter control with dispersion management in a single beamline segment with stable betatron behavior. It thus reduces the spatial requirements for multiple beam dynamic functions, reduces required component counts and thus reduces costs, and allows the use of more compact accelerator configurations than prior art design methods.

  7. Discontinuous gas exchange in insects.

    PubMed

    Quinlan, Michael C; Gibbs, Allen G

    2006-11-01

    Insect respiratory physiology has been studied for many years, and interest in this area of insect biology has become revitalized recently for a number of reasons. Technical advances have greatly improved the precision, accuracy and ease with which gas exchange can be measured in insects. This has made it possible to go beyond classic models such as lepidopteran pupae and examine a far greater diversity of species. One striking result of recent work is the realization that insect gas exchange patterns are much more diverse than formerly recognized. Current work has also benefited from the inclusion of comparative methods that rigorously incorporate phylogenetic, ecological and life history information. We discuss these advances in the context of the classic respiratory pattern of insects, discontinuous gas exchange. This mode of gas exchange was exhaustively described in moth pupae in the 1950s and 1960s. Early workers concluded that discontinuous gas exchange was an adaptation to reduce respiratory water loss. This idea is no longer universally accepted, and several competing hypotheses have been proposed. We discuss the genesis of these alternative hypotheses, and we identify some of the predictions that might be used to test them. We are pleased to report that what was once a mature discipline, in which the broad parameters and adaptive significance of discontinuous gas exchange were thought to be well understood, is now a thriving and vigorous field of research. PMID:16870512

  8. Localized deformation as a key precursor to initiation of intergranular stress corrosion cracking of austenitic stainless steels employed in nuclear power plants

    NASA Astrophysics Data System (ADS)

    Karlsen, Wade; Diego, Gonzalo; Devrient, Bastian

    2010-11-01

    Cold-work has been associated with the occurrence of intergranular cracking of stainless steels employed in light water reactors. This study examined the deformation behavior of AISI 304, AISI 347 and a higher stacking fault energy model alloy subjected to bulk cold-work and (for 347) surface deformation. Deformation microstructures of the materials were examined and correlated with their particular mechanical response under different conditions of temperature, strain rate and degree of prior cold-work. Select slow-strain rate tensile tests in autoclaves enabled the role of local strain heterogeneity in crack initiation in pressurized water reactor environments to be considered. The high stacking fault energy material exhibited uniform strain hardening, even at sub-zero temperatures, while the commercial stainless steels showed significant heterogeneity in their strain response. Surface treatments introduced local cold-work, which had a clear effect on the surface roughness and hardness, and on near-surface residual stress profiles. Autoclave tests led to transgranular surface cracking for a circumferentially ground surface, and intergranular crack initiation for a polished surface.

  9. Woven heat exchanger

    DOEpatents

    Piscitella, Roger R.

    1987-05-05

    In a woven ceramic heat exchanger using the basic tube-in-shell design, each heat exchanger consisting of tube sheets and tube, is woven separately. Individual heat exchangers are assembled in cross-flow configuration. Each heat exchanger is woven from high temperature ceramic fiber, the warp is continuous from tube to tube sheet providing a smooth transition and unitized construction.

  10. Woven heat exchanger

    DOEpatents

    Piscitella, R.R.

    1984-07-16

    This invention relates to a heat exchanger for waste heat recovery from high temperature industrial exhaust streams. In a woven ceramic heat exchanger using the basic tube-in-shell design, each heat exchanger consisting of tube sheets and tube, is woven separately. Individual heat exchangers are assembled in cross-flow configuration. Each heat exchanger is woven from high temperature ceramic fiber, the warp is continuous from tube to tube sheet providing a smooth transition and unitized construction.

  11. Gas Exchange of Algae

    PubMed Central

    Ammann, Elizabeth C. B.; Lynch, Victoria H.

    1966-01-01

    Changes in the oxygen partial pressure of air over the range of 8 to 258 mm of Hg did not adversely affect the photosynthetic capacity of Chlorella pyrenoidosa. Gas exchange and growth measurements remained constant for 3-week periods and were similar to air controls (oxygen pressure of 160 mm of Hg). Oxygen partial pressures of 532 and 745 mm of Hg had an adverse effect on algal metabolism. Carbon dioxide consumption was 24% lower in the gas mixture containing oxygen at a pressure 532 mm of Hg than in the air control, and the growth rate was slightly reduced. Oxygen at a partial pressure of 745 mm of Hg decreased the photosynthetic rate 39% and the growth rate 37% over the corresponding rates in air. The lowered metabolic rates remained constant during 14 days of measurements, and the effect was reversible after this time. Substitution of helium or argon for the nitrogen in air had no effect on oxygen production, carbon dioxide consumption, or growth rate for 3-week periods. All measurements were made at a total pressure of 760 mm of Hg, and all gas mixtures were enriched with 2% carbon dioxide. Thus, the physiological functioning and reliability of a photosynthetic gas exchanger should not be adversely affected by: (i) oxygen partial pressures ranging from 8 to 258 mm of Hg; (ii) the use of pure oxygen at reduced total pressure (155 to 258 mm of Hg) unless pressure per se affects photosynthesis, or (iii) the inclusion of helium or argon in the gas environment (up to a partial pressure of 595 mm of Hg). PMID:5927028

  12. Indiana Health Information Exchange

    Cancer.gov

    The Indiana Health Information Exchange is comprised of various Indiana health care institutions, established to help improve patient safety and is recognized as a best practice for health information exchange.

  13. Micrometer-size Nd-Fe-B dots as model systems for the study of intergranular phase engineering in Nd-Fe-B permanent magnets

    NASA Astrophysics Data System (ADS)

    Le Roy, Damien; Akdogan, Ozan; Ciuta, Georgeta; Dempsey, Nora; Givord, Dominique

    2014-05-01

    Nd-Fe-B micrometer-size dots were prepared by optical lithography and sputtering. It is proposed to use such structures as model systems to study intergranular phase engineering in Nd-Fe-B permanent magnets. The influence of Ta, Nd, Dy, and Gd coatings on the magnetization reversal of such Nd-Fe-B dot arrays are compared, after different heat treatments. A very thin layer of Dy (tNdFeB/tDy = 120) was found to lead to a significant increase of the coercive field, up to 80% for a total equivalent Dy content of less than 5 at. % of all the Nd. A coercivity increase of up to 20% was found with Gd coating which is attributed to the so-called superferrimagnetic coupling phenomenon. Nd and Ta coating are neutral or detrimental to the magnetic hardness.

  14. Low field AC susceptibility study of intergranular critical current density in Mg-substituted CuBa2Ca3Cu4O12-y high temperature superconductors

    NASA Astrophysics Data System (ADS)

    Agarwal, S. K.; Kumaraswamy, B. V.

    2005-05-01

    Measurements of the a.c.susceptibility (χ=χ‧+iχ″) have been made on the Mg substituted high TC superconducting system, CuBa2(MgxCa1-x)3Cu4O12-y (Cu-1234) with x=0, 0.10 & 0.20, at different values of the a.c.field amplitude. Estimates of the intergranular critical current density(JC) made from the field dependent χ″-T curves show an improvement in the Mg-substituted Cu-1234 system. Results have been analysed in the light of the crystal structure and the superconducting anisotropy factor (γ=ξab/ξc) of the Cu-1234 system. Lower superconducting anisotropy emanating from Mg substitution has been found to be significant, resulting in better superconducting properties.

  15. Origins of Negative Strain Rate Dependence of Stress Corrosion Cracking Initiation in Alloy 690, and Intergranular Crack Formation in Thermally Treated Alloy 690

    NASA Astrophysics Data System (ADS)

    Kim, Young Suk; Kim, Sung Soo

    2016-07-01

    We show that enhanced stress corrosion cracking (SCC) initiation in cold-rolled Alloy 690 with decreasing strain rate is related to the rate of short-range ordering (SRO) but not to the time-dependent corrosion process. Evidence for SRO is provided by aging tests on cold-rolled Alloy 690 at 623 K and 693 K (350 °C and 420 °C), respectively, which demonstrate its enhanced lattice contraction and hardness increase with aging temperature and time, respectively. Secondary intergranular cracks formed only in thermally treated and cold-rolled Alloy 690 during SCC tests, which are not SCC cracks, are caused by its lattice contraction by SRO before SCC tests but not by the orientation effect.

  16. Possible surface antiferromagnetism and no evidence for intergranular tunneling magnetoresistance in La0.5Sr0.5CoO3-δ cobaltites

    NASA Astrophysics Data System (ADS)

    Troyanchuk, I. O.; Bushinsky, M. V.; Lobanovsky, L. S.

    2013-12-01

    The magnetization and magnetoresistance (MR) of La0.5Sr0.5CoO3-δ have been studied as function of surface/volume ratio and oxygen deficit. All the samples have positive and negative components of MR at low temperature. The small positive component is predominated in low field regime below and well above the coercive field. The positive MR under magnetic moment reorientation is in contradiction with scenario of negative intergranular tunneling magnetoresistance being the hallmark of half-metallic polycrystalline oxides. The oxygen deficit leads to a gradual stabilization of antiferromagnetic phase in bulk and concomitant enhancement of the MR. The decrease in value of magnetization and enhancement of the negative MR component in compacted at high pressure/room temperature powder with a large surface/volume ratio can be ascribed to antiferromagnetism at the surface.

  17. Effect of Palladium Nuclei Insertion by Electroless Deposition on Magnetic Intergranular Isolation and Read/Write Characteristics in SmCo5 Perpendicular Magnetic Recording Media

    NASA Astrophysics Data System (ADS)

    Sugiyama, Atsushi; Egawa, Yuko; Koizumi, Isao; Yoshino, Masahiro; Hokkyo, Jiro; Asahi, Toru; Kiya, Takanori; Ariake, Jun; Ouchi, Kazuhiro; Osaka, Tetsuya

    In order to improve the magnetic intergranular isolation between the magnetic grains in the SmCo5 perpendicular magnetic recording media, the palladium nuclei deposited by an electrochemical process were introduced into a sputter deposition process of the SmCo5 film. A few nanometer size Pd nuclei were electrochemically deposited on the sputtered Cu underlayer by a displacement deposition (chemical plating). The sizes of Pd nuclei were controlled by adjusting the Pd ion concentration in electrolyte solutions. The magnetic domain size in Sm-Co layer deposited on Pd nuclei / Cu / Ti underlayer became smaller and the magnetization reversal process was changed from the wall motion to the coherent rotation. Moreover, the read/write characteristics were improved at higher linear recording densities.

  18. Origins of Negative Strain Rate Dependence of Stress Corrosion Cracking Initiation in Alloy 690, and Intergranular Crack Formation in Thermally Treated Alloy 690

    NASA Astrophysics Data System (ADS)

    Kim, Young Suk; Kim, Sung Soo

    2016-09-01

    We show that enhanced stress corrosion cracking (SCC) initiation in cold-rolled Alloy 690 with decreasing strain rate is related to the rate of short-range ordering (SRO) but not to the time-dependent corrosion process. Evidence for SRO is provided by aging tests on cold-rolled Alloy 690 at 623 K and 693 K (350 °C and 420 °C), respectively, which demonstrate its enhanced lattice contraction and hardness increase with aging temperature and time, respectively. Secondary intergranular cracks formed only in thermally treated and cold-rolled Alloy 690 during SCC tests, which are not SCC cracks, are caused by its lattice contraction by SRO before SCC tests but not by the orientation effect.

  19. Coercivity and thermal stability improvement in sintered Nd-Fe-B permanent magnets by intergranular addition of Dy-Mn alloy

    NASA Astrophysics Data System (ADS)

    Li, Xiangbin; Liu, Shuo; Cao, Xuejing; Zhou, Beibei; Chen, Ling; Yan, Aru; Yan, Gaolin

    2016-06-01

    To increase coercivity and thermal stability of sintered Nd-Fe-B magnets for high temperature applications, Dy88Mn12 (wt%) alloy powders were intergranular added into (Pr0.25Nd0.75)30.6Cu0.15FebalB1 (wt%) starting magnet. The magnetic properties, microstructure and thermal stability of the sintered magnets with different amounts of Dy88Mn12 were investigated. By adding a small amount of Dy88Mn12, the coercivity was significantly increased from 12.56 kOe to 17.49 kOe. Microstructure analysis showed that a optimized microstructure, i.e. continuous, uniform grain boundary phase was achieved with Dy88Mn12 alloy addition, and Dy was enriched in the outer region of the Nd2Fe14B matrix grains during the sintering process, which favored to substitute for Nd in matrix grains to form the (Nd,Dy)2Fe14B core-shell phase. The greatly increased magnetocrystalline anisotropy of the core-shell phase and the improved decoupling by the continuous grain boundary phase accounted for the coercivity enhancement. Furthermore, by adding 0-4 wt% Dy88Mn12, the reversible temperature coefficients of remanence (α) and coercivity (β) of the magnet were improved from -0.115%/ºC to -0.107%/ºC and -0.744%/ºC to -0.696%/ºC in the range of 20-100 °C, respectively. In addition, the irreversible flux loss of magnetic flow (hirr) decreased sharply as Dy88Mn12 addition. The temperature-dependent magnetic properties results indicated that with intergranular addition of Dy88Mn12 alloy, the thermal stability of the magnets was effectively improved.

  20. Electrically switched ion exchange

    SciTech Connect

    Lilga, M.A.; Schwartz, D.T.; Genders, D.

    1997-10-01

    A variety of waste types containing radioactive {sup 137}Cs are found throughout the DOE complex. These waste types include water in reactor cooling basins, radioactive high-level waste (HLW) in underground storage tanks, and groundwater. Safety and regulatory requirements and economics require the removal of radiocesium before these wastes can be permanently disposed of. Electrically Switched Ion Exchange (ESIX) is an approach for radioactive cesium separation that combines IX and electrochemistry to provide a selective, reversible, and economic separation method that also produces little or no secondary waste. In the ESIX process, an electroactive IX film is deposited electrochemically onto a high-surface area electrode, and ion uptake and elution are controlled directly by modulating the potential of the film. For cesium, the electroactive films under investigation are ferrocyanides, which are well known to have high selectivities for cesium in concentrated sodium solutions. When a cathode potential is applied to the film, Fe{sup +3} is reduced to the Fe{sup +2} state, and a cation must be intercalated into the film to maintain charge neutrality (i.e., Cs{sup +} is loaded). Conversely, if an anodic potential is applied, a cation must be released from the film (i.e., Cs{sup +} is unloaded). Therefore, to load the film with cesium, the film is simply reduced; to unload cesium, the film is oxidized.

  1. Lipid exchange between membranes.

    PubMed Central

    Jähnig, F

    1984-01-01

    The exchange of lipid molecules between vesicle bilayers in water and a monolayer forming at the water surface was investigated theoretically within the framework of thermodynamics. The total number of exchanged molecules was found to depend on the bilayer curvature as expressed by the vesicle radius and on the boundary condition for exchange, i.e., whether during exchange the radius or the packing density of the vesicles remains constant. The boundary condition is determined by the rate of flip-flop within the bilayer relative to the rate of exchange between bi- and monolayer. If flip-flop is fast, exchange is independent of the vesicle radius; if flip-flop is slow, exchange increases with the vesicle radius. Available experimental results agree with the detailed form of this dependence. When the theory was extended to exchange between two bilayers of different curvature, the direction of exchange was also determined by the curvatures and the boundary conditions for exchange. Due to the dependence of the boundary conditions on flip-flop and, consequently, on membrane fluidity, exchange between membranes may partially be regulated by membrane fluidity. PMID:6518251

  2. Heat exchanger performance monitoring guidelines. Final report

    SciTech Connect

    Stambaugh, N.; Closser, W. Jr.; Mollerus, F.J.

    1991-12-01

    Fouling can occur in many heat exchanger applications in a way that impedes heat transfer and fluid flow and reduces the heat transfer or performance capability of the heat exchanger. Fouling may be significant for heat exchanger surfaces and flow paths in contact with plant service water. This report presents guidelines for performance monitoring of heat exchangers subject to fouling. Guidelines include selection of heat exchangers to monitor based on system function, safety function and system configuration. Five monitoring methods are discussed: the heat transfer, temperature monitoring, temperature effectiveness, delta P and periodic maintenance methods. Guidelines are included for selecting the appropriate monitoring methods and for implementing the selected methods. The report also includes a bibliography, example calculations, and technical notes applicable to the heat transfer method.

  3. The Electrically Controlled Exchange Bias

    NASA Astrophysics Data System (ADS)

    Harper, Jacob

    Controlling magnetism via voltage in the virtual absence of electric current is the key to reduce power consumption while enhancing processing speed, integration density and functionality in comparison with present-day information technology. Almost all spintronic devices rely on tailored interface magnetism. Controlling magnetism at thin-film interfaces, preferably by purely electrical means, is therefore a key challenge to better spintronics. However, there is no direct interaction between magnetization and electric fields, thus making voltage control of magnetism in general a scientific challenge. The significance of controlled interface magnetism started with the exchange-bias effect. Exchange bias is a coupling phenomenon at magnetic interfaces that manifests itself prominently in the shift of the ferromagnetic hysteresis loop along the magnetic-field axis. Various attempts on controlling exchange bias via voltage utilizing different scientific principles have been intensively studied recently. The majority of present research is emphasizing on various complex oxides. Our approach can be considered as a paradigm shift away from complex oxides. We focus on a magnetoelectric antiferromagnetic simple oxide Cr2O3. From a combination of experimental and theoretical efforts, we show that the (0001) surface of magnetoelectric Cr2O3 has a roughness-insensitive, electrically switchable magnetization. Using a ferromagnetic Pd/Co multilayer deposited on the (0001) surface of a Cr2O3 single crystal, we achieve reversible, room-temperature isothermal switching of the exchange-bias between positive and negative values by reversing the electric field while maintaining a permanent magnetic field. This is a significant scientific breakthrough providing a new route towards potentially revolutionizing information technology. In addition, a second path of electrically controlled exchange bias is introduced by exploiting the piezoelectric property of BaTiO3. An exchange-bias Co

  4. Nonsurvivable momentum exchange system

    NASA Technical Reports Server (NTRS)

    Roder, Russell (Inventor); Ahronovich, Eliezer (Inventor); Davis, III, Milton C. (Inventor)

    2007-01-01

    A demiseable momentum exchange system includes a base and a flywheel rotatably supported on the base. The flywheel includes a web portion defining a plurality of web openings and a rim portion. The momentum exchange system further includes a motor for driving the flywheel and a cover for engaging the base to substantially enclose the flywheel. The system may also include components having a melting temperature below 1500 degrees Celsius. The momentum exchange system is configured to demise on reentry.

  5. Text Exchange System

    NASA Technical Reports Server (NTRS)

    Snyder, W. V.; Hanson, R. J.

    1986-01-01

    Text Exchange System (TES) exchanges and maintains organized textual information including source code, documentation, data, and listings. System consists of two computer programs and definition of format for information storage. Comprehensive program used to create, read, and maintain TES files. TES developed to meet three goals: First, easy and efficient exchange of programs and other textual data between similar and dissimilar computer systems via magnetic tape. Second, provide transportable management system for textual information. Third, provide common user interface, over wide variety of computing systems, for all activities associated with text exchange.

  6. Preparation of Pt-Co nanoparticles by galvanostatic pulse electrochemical codeposition on in situ electrochemical reduced graphene nanoplates based carbon paper electrode for oxygen reduction reaction in proton exchange membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Yaldagard, Maryam; Seghatoleslami, Naser; Jahanshahi, Mohsen

    2014-10-01

    Nanocomposite films of Pt-Co nanoparticles deposited on graphene nanoplate based gas diffusion layer electrode are fabricated via an electrochemical route involving a series of electrochemical process. Pt-Co nanoparticles of 11.37 nm in average size are prepared by galvanostatic codeposition in 0.5 M NaCl at PH of 2.5 at 300 mA cm-2 on the surface of in situ reduced graphene nanoplates on carbon paper. The topographical features, structure, morphology and composition of the prepared film samples are characterized by Atomic Force microscopy, Raman Spectroscopy, FTIR analysis, X-ray Diffraction, FESEM and EDS. At the same time, the catalytic activities of prepared electrodes for the oxygen reduction reaction are evaluated through cyclic voltammetry, linear sweep voltammetry and chronoamperometry and electrochemical impedance spectroscopy measurements. Raman spectroscopy measurements confirmed the graphitic structure of the produced graphene nanoplates. The nanoparticles in the film were observed to be uniform spherical objects and well distributed. Catalytic properties of Pt-Co/GNP/GDL electrode were compared with Pt/C/GDL using half cell polarization measurements based on both mass activity and specific activity. The as prepared Pt-Co/GNP/GDL electrode exhibits high catalytic activity for the ORR, which may be attributed to structural changes caused by alloying and the high specific surface area of graphene nanoplates catalyst support. The mass activity peak current is found to be as high as 728.25 mA mgPt-1.

  7. Asymmetric Magnetization Reversal in Exchange Bias Systems*

    NASA Astrophysics Data System (ADS)

    Fitzsimmons, Michael

    2001-03-01

    Polarized neutron reflectometry measured the in-plane projection of the net-magnetization vector of polycrystalline Fe films exchange-coupled to (110) FeF2 antiferromagnetic (AF) films of controlled crystalline quality. For the sample with the single crystal AF film, we observed perpendicular exchange coupling across the ferromagnetic (F)-AF interface on either side of the hysteresis loop at coercivity. Perpendicular exchange coupling was observed regardless of cooling field orientation parallel or perpendicular to the AF anisotropy axis. Yet, for one orientation the exchange bias was zero; thus, perpendicular exchange coupling is not a sufficient condition for exchange bias. For samples with twinned AF films, an asymmetry in the spin flip scattering on either side of the hysteresis loop, and consequently in the magnetization reversal process, was observed. The origin of the asymmetry is explained by frustration of perpendicular exchange coupling, which enhances exchange bias and leads to 45° exchange coupling across the F-AF interface. The easy axis in the ferromagnet, which gives rise to asymmetric magnetization reversal in the twinned samples, is not present in samples with (110) textured polycrystalline AF films; and consequently exchange bias is reduced. *Work supported by the U.S. Department of Energy, BES-DMS under Contract No. W-7405-Eng-36, Grant No. DE-FG03-87ER-45332 and funds from the University of California Collaborative University and Laboratory Assisted Research. ÝWork in collaboration with A. Hoffmann, P. Yashar, J. Groves, R. Springer, P. Arendt (LANL), C. Leighton, K. Liu, Ivan K. Schuller (UCSD), J. Nogués (UAB), C.F. Majkrzak, J.A. Dura (NIST), H. Fritzsche (HMI), V. Leiner, H. Lauter (ILL).

  8. Higher Education Exchange, 2008

    ERIC Educational Resources Information Center

    Brown, David W., Ed.; Witte, Deborah, Ed.

    2008-01-01

    "Higher Education Exchange" publishes case studies, analyses, news, and ideas about efforts within higher education to develop more democratic societies. Contributors to this issue of the "Higher Education Exchange" examine whether institutions of higher learning are doing anything to increase the capacity of citizens to shape their future.…

  9. Higher Education Exchange, 2010

    ERIC Educational Resources Information Center

    Brown, David W., Ed.; Witte, Deborah, Ed.

    2010-01-01

    "Higher Education Exchange" publishes case studies, analyses, news, and ideas about efforts within higher education to develop more democratic societies. Contributors to this issue of the "Higher Education Exchange" examine whether institutions of higher learning are doing anything to increase the capacity of citizens to shape their future.…

  10. Direct fired heat exchanger

    DOEpatents

    Reimann, Robert C.; Root, Richard A.

    1986-01-01

    A gas-to-liquid heat exchanger system which transfers heat from a gas, generally the combustion gas of a direct-fired generator of an absorption machine, to a liquid, generally an absorbent solution. The heat exchanger system is in a counterflow fluid arrangement which creates a more efficient heat transfer.

  11. Handicapping Social Exchange Theory.

    ERIC Educational Resources Information Center

    Mishler, Barbara

    The economic theory of social exchange has some serious shortcomings when applied to minorities--especially the disabled. First, it assumes dyads comprise the basic unit where exchange occurs and that rewards and costs must occur at that level. Second, the model standardizes the experience of white, Western European and American males. The model…

  12. Building Relationships through Exchange

    ERIC Educational Resources Information Center

    Primavera, Angi; Hall, Ellen

    2011-01-01

    From the moment of birth, children form and develop relationships with others in their world based on exchange. Children recognize that engaging in such encounters offers them the opportunity to enter into a relationship with another individual and to nurture that relationship through the exchange of messages and gifts, items and ideas. At Boulder…

  13. Higher Education Exchange, 2011

    ERIC Educational Resources Information Center

    Brown, David W., Ed.; Witte, Deborah, Ed.

    2011-01-01

    "Higher Education Exchange" publishes case studies, analyses, news, and ideas about efforts within higher education to develop more democratic societies. Contributors to this issue of the "Higher Education Exchange" examine whether institutions of higher learning are doing anything to increase the capacity of citizens to shape their future.…

  14. Optimization of Heat Exchangers

    SciTech Connect

    Ivan Catton

    2010-10-01

    The objective of this research is to develop tools to design and optimize heat exchangers (HE) and compact heat exchangers (CHE) for intermediate loop heat transport systems found in the very high temperature reator (VHTR) and other Generation IV designs by addressing heat transfer surface augmentation and conjugate modeling. To optimize heat exchanger, a fast running model must be created that will allow for multiple designs to be compared quickly. To model a heat exchanger, volume averaging theory, VAT, is used. VAT allows for the conservation of mass, momentum and energy to be solved for point by point in a 3 dimensional computer model of a heat exchanger. The end product of this project is a computer code that can predict an optimal configuration for a heat exchanger given only a few constraints (input fluids, size, cost, etc.). As VAT computer code can be used to model characteristics )pumping power, temperatures, and cost) of heat exchangers more quickly than traditional CFD or experiment, optimization of every geometric parameter simultaneously can be made. Using design of experiment, DOE and genetric algorithms, GE, to optimize the results of the computer code will improve heat exchanger disign.

  15. Higher Education Exchange, 2012

    ERIC Educational Resources Information Center

    Brown, David W., Ed.; Witte, Deborah, Ed.

    2012-01-01

    "Higher Education Exchange" publishes case studies, analyses, news, and ideas about efforts within higher education to develop more democratic societies. Contributors to this issue of the "Higher Education Exchange" examine whether institutions of higher learning are doing anything to increase the capacity of citizens to shape their future.…

  16. Higher Education Exchange, 2007

    ERIC Educational Resources Information Center

    Brown, David W., Ed.; Witte, Deborah, Ed.

    2007-01-01

    "Higher Education Exchange" publishes case studies, analyses, news, and ideas about efforts within higher education to develop more democratic societies. Contributors to this issue of the "Higher Education Exchange" discuss the concept of growing public scholars; each contribution incorporates a student component. Articles include: (1) "Foreword"…

  17. Money and Exchange.

    ERIC Educational Resources Information Center

    Walstad, William B.; And Others

    1982-01-01

    This teaching guide begins with an explanation of the role of money in the economy, focusing on its circulation or exchange. The use of money as a unit of account, a store of value, and a medium of exchange are explained. Three brief teaching units are included. The grade K-2 unit, "Money Counts," provides games and activities which develop the…

  18. Mechanical Property and Intergranular Corrosion Sensitivity of Zn-Free and Zn-Microalloyed Al-2.7Cu-1.7Li-0.3Mg Alloys

    NASA Astrophysics Data System (ADS)

    Li, Jin-feng; Xu, Long; Cai, Chao; Chen, Yong-lai; Zhang, Xu-hu; Zheng, Zi-qiao

    2014-11-01

    The influence of 0.72 pct Zn addition on the tensile properties of Al-2.7Cu-1.7Li-0.3Mg alloys was investigated. Their intergranular corrosion (IGC) dependence on aging [T6 type at 423 K (150 °C) and 448 K (175 °C) and T8 type at 423 K (150 °C)] time was studied. An IGC diagram associated with aging process was established. The addition of 0.72 pct Zn enhanced the strength of the Al-Li alloy with T6 type aging at 448 K (175 °C). With aging process, the corrosion mode of the T6-aged Al-Li alloys was changed in the following order: pitting and local IGC (initial aging stage), general IGC (underaging stage), local IGC (near peak-aging stage), and pitting (overaging stage) again. The IGC depth was increased first and then decreased with aging time extension. The corrosion potential change of grains and the microstructure variation were used to explain the IGC sensitivity of the Al-Li alloy with different tempers. Meanwhile, 0.72 pct Zn addition decreased the IGC sensitivity of the Al-Li alloy, especially the T6-aged Al-Li alloy.

  19. Mechanical Property and Intergranular Corrosion Sensitivity of Zn-Free and Zn-Microalloyed Al-2.7Cu-1.7Li-0.3Mg Alloys

    NASA Astrophysics Data System (ADS)

    Li, Jin-feng; Xu, Long; Cai, Chao; Chen, Yong-lai; Zhang, Xu-hu; Zheng, Zi-qiao

    2014-09-01

    The influence of 0.72 pct Zn addition on the tensile properties of Al-2.7Cu-1.7Li-0.3Mg alloys was investigated. Their intergranular corrosion (IGC) dependence on aging [T6 type at 423 K (150 °C) and 448 K (175 °C) and T8 type at 423 K (150 °C)] time was studied. An IGC diagram associated with aging process was established. The addition of 0.72 pct Zn enhanced the strength of the Al-Li alloy with T6 type aging at 448 K (175 °C). With aging process, the corrosion mode of the T6-aged Al-Li alloys was changed in the following order: pitting and local IGC (initial aging stage), general IGC (underaging stage), local IGC (near peak-aging stage), and pitting (overaging stage) again. The IGC depth was increased first and then decreased with aging time extension. The corrosion potential change of grains and the microstructure variation were used to explain the IGC sensitivity of the Al-Li alloy with different tempers. Meanwhile, 0.72 pct Zn addition decreased the IGC sensitivity of the Al-Li alloy, especially the T6-aged Al-Li alloy.

  20. A Re-examination of the Portevin-Le Chatelier Effect in Alloy 718 in Connection with Oxidation-Assisted Intergranular Cracking

    NASA Astrophysics Data System (ADS)

    Max, Bertrand; Viguier, Bernard; Andrieu, Eric; Cloue, Jean Marc

    2014-11-01

    In Alloy 718, a sharp transition exists in the fracture path changing from an intergranular brittle mode to a transgranular ductile mode which is associated with a transition of flow behavior from smooth in the dynamic strain aging regime to a serrated one in the Portevin-Le Chatelier (PLC) regime. In order to better understand both deformation and rupture behavior, PLC phenomenon in a precipitation-hardened nickel-base superalloy was carefully investigated in a wide range of temperatures [573 K to 973 K (300 °C to 700 °C)] and strain rates (10-5 to 3.2 × 10-2 s-1). Distinction was made between two PLC domains characterized by different evolutions of the critical strain to the onset of the first serration namely normal and inverse behavior. The apparent activation energies associated with both domains were determined using different methods. Results showed that normal and inverse behavior domains are related to dynamic interaction of dislocations with, respectively, interstitial and substitutional solutes atoms. This analysis confirms that normal PLC regime may be associated to the diffusion of carbon atoms, whereas the substitutional species involves in the inverse regime is discussed with an emphasis on the role of Nb and Mo.

  1. Interdependence of character of grain boundaries, intergranular segregation of boron and grain boundary liquation in simulated weld heat-affected zone in Inconel 718

    SciTech Connect

    Guo, H.; Chaturvedi, M.C.; Richards, N.L.; McMahon, G.S.

    1999-01-08

    Intergranular microfissuring is frequently observed in the weld heat-affected zones (HAZ) in Inconel 718. Extensive studies of this phenomenon have established that the HAZ microfissuring in Inconel 718 is associated with the constitutional liquation of grain boundary (GB) precipitates of carbides, Laves and {delta} phases. In addition, HAZ microfissuring has been also attributed to the GB segregation of B and S. To differentiate between the influence of B from other factors, studies were initiated on Inconel 718 that was almost free of C, P, and S, and contained different concentrations of B. These studies have shown that B in Inconel 718 can segregate to the grain boundaries by a non-equilibrium mechanism during cooling from the pre-weld solution heat treatment temperature, which would lower the melting temperature of the GB material. If the segregation of B is sufficiently high, the GBs are likely to liquate in the HAZ during the heating component of the welding thermal cycle. The inability of the liquated GBs to support tensile stresses that develop during cooling of the welds would result in microfissuring in the HAZs. It was also observed that the GB liquation in the HAZs was heterogeneously distributed. That is, while a GB liquated others connected to it did not. Therefore, an investigation was initiated to determine the interdependence of segregation of B on GBs, their crystallographic character and liquation. The results are presented in this communication.

  2. Exchange spring like magnetic behavior in cobalt ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Chithra, M.; Anumol, C. N.; Sahu, Baidyanath; Sahoo, Subasa C.

    2016-03-01

    Cobalt ferrite nanoparticles were prepared by sol-gel technique and were annealed at 900 °C in air for 2 h. Structural properties were studied by X-ray diffraction, Raman spectroscopy and Fourier transformed infrared spectroscopy. Scanning electron microscopy and transmission electron microscopy studies show presence of mostly two different sizes of grains in these samples. Magnetization value of 58.36 emu/g was observed at 300 K for the as prepared sample and an enhanced magnetization close to the bulk value of 80.59 emu/g was observed for the annealed sample. At 10 K a two stepped hysteresis loop showing exchange spring magnetic behavior was observed accompanied by very high values of coercivity and remanence. Two clear peaks were observed in the derivative of demagnetization curve in the as prepared sample where as two partially overlapped peaks were observed in the annealed sample. The observed magnetic properties can be understood on the basis of the grain size and their distribution leading to the different types of intergranular interactions in these nanoparticles.

  3. Markets, distribution, and exchange after societal cataclysm

    SciTech Connect

    Cantor, R.A.; Henry, S.; Rayner, S.; Eastern Michigan Univ., Ypsilanti, MI . Dept. of Sociology; Oak Ridge National Lab., TN )

    1989-11-01

    The report identifies constraints and opportunities for the restoration of economic exchange following nuclear war. Four survival scenarios are postulated based on high or low levels of damage to (1) institutions that signal trading opportunities, reduce transaction costs, and regulate and enforce contracts, and (2) resources that are used to create and define wealth. The four scenarios are best case, worst case, resource abundance, and an institution intensive case. Three kinds of literature were reviewed, (1) the economics literature on formal markets, (2) the sociological literature on informal markets, and (3) the economic anthropology literature on pre-capitalist and pre-industrial exchange. From this corpus a set of non-market and market exchange structures are derived and rendered as rules vectors describing their operation. Each of the four survival scenarios is expounded as a subset of the possible exchange structures that is logically compatible with the constraints defining that scenario. 242 refs.

  4. Wound tube heat exchanger

    DOEpatents

    Ecker, Amir L.

    1983-01-01

    What is disclosed is a wound tube heat exchanger in which a plurality of tubes having flattened areas are held contiguous adjacent flattened areas of tubes by a plurality of windings to give a double walled heat exchanger. The plurality of windings serve as a plurality of effective force vectors holding the conduits contiguous heat conducting walls of another conduit and result in highly efficient heat transfer. The resulting heat exchange bundle is economical and can be coiled into the desired shape. Also disclosed are specific embodiments such as the one in which the tubes are expanded against their windings after being coiled to insure highly efficient heat transfer.

  5. Heat and mass exchanger

    SciTech Connect

    Lowenstein, Andrew; Sibilia, Marc J.; Miller, Jeffrey A.; Tonon, Thomas

    2011-06-28

    A mass and heat exchanger includes at least one first substrate with a surface for supporting a continuous flow of a liquid thereon that either absorbs, desorbs, evaporates or condenses one or more gaseous species from or to a surrounding gas; and at least one second substrate operatively associated with the first substrate. The second substrate includes a surface for supporting the continuous flow of the liquid thereon and is adapted to carry a heat exchange fluid therethrough, wherein heat transfer occurs between the liquid and the heat exchange fluid.

  6. Heat and mass exchanger

    SciTech Connect

    Lowenstein, Andrew; Sibilia, Marc J.; Miller, Jeffrey A.; Tonon, Thomas

    2007-09-18

    A mass and heat exchanger includes at least one first substrate with a surface for supporting a continuous flow of a liquid thereon that either absorbs, desorbs, evaporates or condenses one or more gaseous species from or to a surrounding gas; and at least one second substrate operatively associated with the first substrate. The second substrate includes a surface for supporting the continuous flow of the liquid thereon and is adapted to carry a heat exchange fluid therethrough, wherein heat transfer occurs between the liquid and the heat exchange fluid.

  7. Microtube strip heat exchanger

    SciTech Connect

    Doty, F.D.

    1991-10-16

    This progress report is for the September--October 1991 quarter. We have demonstrated feasibility of higher specific conductance by a factor of five than any other work in high-temperature gas-to-gas exchangers. These laminar-flow, microtube exchangers exhibit extremely low pressure drop compared to alternative compact designs under similar conditions because of their much shorter flow length and larger total flow area for lower flow velocities. The design appears to be amenable to mass production techniques, but considerable process development remains. The reduction in materials usage and the improved heat exchanger performance promise to be of enormous significance in advanced engine designs and in cryogenics.

  8. Heat exchanger for electrothermal devices

    SciTech Connect

    Zavesky, R.J.; Sovey, J.S.; Mirtich, M.J.; Marinos, C.; Penko, P.F.

    1986-09-02

    A heat exchanger is described for heating a gaseous propellant to a temperature between about 200/sup 0/C and about 2200/sup 0/C in an electrothermal thruster having a nozzle comprising a hollow housing forming a cylindrical chamber adjacent to the nozzle, the hollow housing having a textured inner surface to provide high absorptivity and an oppositely disposed textured outer surface to provide high emissivity, an outer housing surrounding the cylindrical chamber in spaced relationship thereto thereby forming an annular chamber for conducting the gaseous propellant to the nozzle, a porous heat exchanger material selected from the group consisting of refractories, ceramics, and cermets contained within the annular chamber, housing a wire coiled about the outer surface of the hollow housing in engagement with the outer housing for providing a lengthened spiral flow path for the propellant to the annular chamber, an electrical heating comprising a coiled tube having a wall thickness of about 0.25 mm and a textured surface for providing high emissivity mounted within the cylindrical chamber in spaced relationship with the textured inner surface for radiatively heating the hollow housing and heat exchanger material without contacting the gaseous propellant, means for supplying a gaseous propellant to the lengthened spiral flow path and seal annular chamber whereby the propellant is uniformly heated by the hollow housing and the porous heat exchanger material as it flows therethrough in a minimum gas path length, and a thermal choke formed in the electrical heating element adjacent to the coiled wire for reducing conducted thermal energy.

  9. Outdoor heat exchanger section

    SciTech Connect

    Kessler, A.F.; Smiley, W.A. III; Wendt, M.E.

    1988-02-09

    An outdoor section for an air conditioning system is described comprising: a compressor; a heat exchanger; a cabinet having an upper cabinet section, a lower cabinet section and a louvered lower section top cover, the heat exchanger and the compressor being housed in the lower cabinet section and the upper cabinet section having a solid top which overlies the louvers in the lower section top cover; and a fan disposed in the lower cabinet section to draw air through the sides of the lower cabinet section and through the heat exchanger housed therein, the fan discharging air, after having been drawn through the heat exchanger, upward through the louvers in the lower cabinet section top cover and into the interior of the upper cabinet section.

  10. Exchange transfusion - series (image)

    MedlinePlus

    ... her back, usually under a radiant warmer. The umbilical vein is catheterized with a fluid-filled catheter. ... plasma is injected. After the exchange transfusion, an umbilical catheter may be left in place in case ...

  11. Active microchannel heat exchanger

    DOEpatents

    Tonkovich, Anna Lee Y [Pasco, WA; Roberts, Gary L [West Richland, WA; Call, Charles J [Pasco, WA; Wegeng, Robert S [Richland, WA; Wang, Yong [Richland, WA

    2001-01-01

    The present invention is an active microchannel heat exchanger with an active heat source and with microchannel architecture. The microchannel heat exchanger has (a) an exothermic reaction chamber; (b) an exhaust chamber; and (c) a heat exchanger chamber in thermal contact with the exhaust chamber, wherein (d) heat from the exothermic reaction chamber is convected by an exothermic reaction exhaust through the exhaust chamber and by conduction through a containment wall to the working fluid in the heat exchanger chamber thereby raising a temperature of the working fluid. The invention is particularly useful as a liquid fuel vaporizer and/or a steam generator for fuel cell power systems, and as a heat source for sustaining endothermic chemical reactions and initiating exothermic reactions.

  12. Anion exchange polymer electrolytes

    SciTech Connect

    Kim, Yu Seung; Kim, Dae Sik

    2015-06-02

    Anion exchange polymer electrolytes that include guanidinium functionalized polymers may be used as membranes and binders for electrocatalysts in preparation of anodes for electrochemical cells such as solid alkaline fuel cells.

  13. Data exchange in metrology.

    PubMed

    Badger, P

    1996-01-01

    The adoption of the directives 71/316/EEC on measuring instruments and 90/384/EEC on non-automatic weighing instruments has resulted in a considerable quantity of certificates to be exchanged between the Central Metrological Authorities and the Local Metrological Authorities, in the member states. This requirement to exchange data, prompted the setting up of the WELMEC working group, to explore how computerisation could help the member states perform their tasks. PMID:10172832

  14. Microtube Strip Heat Exchanger

    SciTech Connect

    Doty, F.D.

    1990-12-27

    Doty Scientific (DSI) believes their Microtube-Strip Heat Exchanger will contribute significantly to (a) the closed Brayton cycles being pursued at MIT, NASA, and elsewhere; (b) reverse Brayton cycle cryocoolers, currently being investigated by NASA for space missions, being applied to MRI superconducting magnets; and (c) high-efficiency cryogenic gas separation schemes for CO{sub 2} removal from exhaust stacks. The goal of this current study is to show the potential for substantial progress in high-effectiveness, low-cost, gas-to-gas heat exchangers for diverse applications at temperatures from below 100 K to above 1000 K. To date, the highest effectiveness measured is about 98%, and relative pressure drops below 0.1% with a specific conductance of about 45 W/kgK are reported. During the pre-award period DSI built and tested a 3-module heat exchanger bank using 103-tube microtube strip (MTS) modules. To add to their analytical capabilities, DSI has acquired computational fluid dynamics (CFD) software. This report describes the pre-award work and the status of the ten tasks of the current project, which are: analyze flow distribution and thermal stresses within individual modules; design a heat exchanger bank of ten modules with 400 microtube per module; obtain production quality tubestrip die and AISI 304 tubestrips; obtain production quality microtubing; construct revised MTS heat exchanger; construct dies and fixtures for prototype heat exchanger; construct 100 MTS modules; assemble 8-10 prototype MTS heat exchangers; test prototype MTS heat exchanger; and verify test through independent means. 7 refs., 9 figs. 1 tab. (CK)

  15. The effect of SiO2 content on activation volumes in exchange coupled composite media

    NASA Astrophysics Data System (ADS)

    Chureemart, J.; Lari, L.; Nolan, T. P.; O'Grady, K.

    2013-08-01

    The activation volume, Vact, and the physical grain volume, VTEM, have been investigated on identical structures of exchange coupled composite media with three different contents of silicon dioxide (SiO2) utilised for intergranular exchange decoupling. Time dependence measurements known as the waiting time method have been used to determine Vact. Transmission Electron Microscopy analysis has been carried out to investigate the grain size distribution and the composition distribution at the grain boundaries using bright field high resolution-scanning transmission electron microscopy (BF HR-STEM) and high angle annular dark-field (HAADF) modes. We found that Vact and VTEM decrease as the oxide content is increased. The activation volume and the single grain volume are in excellent agreement for the samples with the highest oxide content indicating complete exchange decoupling. The BF HR-STEM and HAADF STEM images indicate excellent SiO2 segregation at the grain boundaries. This result implies that the activation volume in advanced recording media can be estimated via the correlation to the grain size.

  16. General anesthesia reduces the information exchange between heart and circulation.

    PubMed

    Porta, Alberto; Bari, Vlasta; Marchi, Andrea; De Maria, Beatrice; Pistuddi, Valeria; Ranucci, Marco

    2015-08-01

    The study demonstrates the ability of an information-theoretic measure, such as the transfer entropy (TE), in detecting the depression of the cardiac baroreflex control and circulatory-cardio mechanical feedforward link during propofol-induced general anesthesia. TE was computed from spontaneous variability of heart period (HP) and systolic arterial pressure (SAP) in patients undergoing coronary artery bypass graft (CABG). TE from SAP to HP and from HP to SAP were evaluated by accounting for the confounding effect of respiration (R) affecting both HP and SAP (i.e. TESAP→HP|R and TEHP→SAP|R respectively). Both TESAP→HP|R and TEHP→SAP|R decreased during general anesthesia, thus suggesting that the strength of the causal relation diminished over both arms of the closed loop HP-SAP control. The squared coherence function between HP and SAP confirmed the decreased HP-SAP coupling during general anesthesia, even though it could not distinguish directionality. PMID:26737178

  17. Radial flow heat exchanger

    DOEpatents

    Valenzuela, Javier

    2001-01-01

    A radial flow heat exchanger (20) having a plurality of first passages (24) for transporting a first fluid (25) and a plurality of second passages (26) for transporting a second fluid (27). The first and second passages are arranged in stacked, alternating relationship, are separated from one another by relatively thin plates (30) and (32), and surround a central axis (22). The thickness of the first and second passages are selected so that the first and second fluids, respectively, are transported with laminar flow through the passages. To enhance thermal energy transfer between first and second passages, the latter are arranged so each first passage is in thermal communication with an associated second passage along substantially its entire length, and vice versa with respect to the second passages. The heat exchangers may be stacked to achieve a modular heat exchange assembly (300). Certain heat exchangers in the assembly may be designed slightly differently than other heat exchangers to address changes in fluid properties during transport through the heat exchanger, so as to enhance overall thermal effectiveness of the assembly.

  18. Vacuum powered heat exchanger

    SciTech Connect

    Ruffolo, R.F.

    1986-06-24

    In an internal combustion engine including an oil lubrication system, a liquid cooling system, and an improved air intake system is described. The improved air intake system comprises: a housing including a first opening in one end, which opening is open to the atmosphere and a second opening comprising an air outlet opening in the other end open to the air intake manifold of the engine, a heat exchanger positioned in the first opening. The heat exchanger consists of a series of coils positioned in the flow path of the atmospheric air as it enters the housing, the heat exchanger being fluidly connected to either the engine lubrication system or the cooling system to provide a warm heat source for the incoming air to the housing, acceleration means positioned in the housing downstream of the heat exchanger, the acceleration means comprising a honeycomb structure positioned across the air intake flow path. The honey-comb structure includes a multitude of honey combed mini-venturi cells through which the heated air flows in an accelerated mode, a removable air filter positioned between the heat exchanger and the acceleration means and a single opening provided in the housing through which the air filter can be passed and removed, and additional openings in the housing positioned downstream of the heat exchanger and upstream of the air filter, the additional openings including removable flaps for opening and closing the openings to control the temperature of the air flowing through the housing.

  19. Analysis of a Flooded Heat Exchanger

    ERIC Educational Resources Information Center

    Fink, Aaron H.; Luyben, William L.

    2015-01-01

    Flooded heat exchangers are often used in industry to reduce the required heat-transfer area and the size of utility control valves. These units involve a condensing vapor on the hot side that accumulates as a liquid phase in the lower part of the vessel. The heat transfer occurs mostly in the vapor space, but the condensate becomes somewhat…

  20. Hydrostratigraphic characterization of intergranular and secondary porosity in part of the Cambrian sandstone aquifer system of the cratonic interior of North America: Improving predictability of hydrogeologic properties

    USGS Publications Warehouse

    Runkel, Anthony C.; Tipping, R.G.; Alexander, E.C., Jr.; Alexander, S.C.

    2006-01-01

    The Upper Cambrian interval of strata in the cratonic interior of North America has a long history of inconsistent hydrogeologic classification and a reputation for marked and unpredictable variability in hydraulic properties. We employed a hydrostratigraphic approach that requires hydraulic data to be interpreted within the context of a detailed characterization of the distribution of porosity and permeability to arrive at a better understanding of these rocks. As a first step, we constructed a framework of hydrostratigraphic attributes that is a depiction of the spatial distribution of both rock matrix and secondary porosity, independent of hydraulic data such as pumping-test results. The locations of hundreds of borehole geophysical logs and laboratory measurements of rock sample matrix porosity and permeability were mapped on detailed (mostly 1:100,000 or greater), conventional, lithostratigraphic maps. Stratigraphic cross-sections, based on hundreds of natural gamma logs and thousands of water-well records, have provided a markedly improved depiction of the regional distribution of rock matrix hydrostratigraphic components. Borehole, core and outcrop observations of secondary porosity were also tied to detailed stratigraphic sections and interpolated regionally. As a second step, we compiled and conducted a large number of hydraulic tests (e.g., packer tests and borehole flowmeter logs) and analyzed thousands of specific capacity tests (converted to hydraulic conductivity). Interpretation of these data within the context of the hydrostratigraphic attributes allowed us to produce a new hydrogeologic characterization for this stratigraphic interval and gain important insights into geologic controls on hydraulic variability. There are a number of assumptions in herent in most previous hydrogeologic investigations of these strata, such as equivalency of lithostratigraphic and hydrogeologic units and the dominance of intergranular flow in sandstone, that are not

  1. Reducing Dropouts.

    ERIC Educational Resources Information Center

    Timpane, Michael; And Others

    A group of three conference papers, all addressing the subject of effective programs to decrease the number of school dropouts, is presented in this document. The first paper, "Systemic Approaches to Reducing Dropouts" (Michael Timpane), asserts that dropping out is a symptom of failures in the social, economic, and educational systems. Dropping…

  2. Federal funding for needle exchange programs.

    PubMed

    Clark, Peter A; Fadus, Matthew

    2010-01-01

    The HIV/AIDS pandemic has affected millions across the globe. The sharing of needles, for reasons of economy or social relations, has become the most common mode of HIV transmission among injection drug users. Needle exchange programs, which provide many services in addition to the exchange of clean needles for contaminated needles, have proven effective in reducing HIV rates among injection drug users in their communities. Although these programs have proven to be one of the most effective strategies in the efforts to reduce HIV rates, there has been a federal ban on the use of federal money for needle exchange programs since 1989. This ban was introduced by Congress in accordance with the drug war ideology, a narrow and elusive plan to completely eradicate drug use in the United States. Although there are a significant number of government reports supporting needle exchange programs, including support from the CDC, American Medical Association, the National Institutes of Health, it appears as If public health and the lives of others have become a secondary concern to strong federal policy on eradicating drug use. Lifting the federal ban would save the country millions of lives and billions of dollars in healthcare costs. Needle exchange programs should be an integral part of HIV prevention strategy, and are ethically imperative as well, restoring human dignity to the clients that so often need it.
    PMID:20037499

  3. Heat exchanger restart evaluation

    SciTech Connect

    Morrison, J.M.; Hirst, C.W.; Lentz, T.F.

    1992-02-28

    On December 24, 1991, the K-Reactor was in the shutdown mode with full AC process water flow and full cooling water flow. Safety rod testing was being performed as part of the power ascension testing program. The results of cooling water samples indicated tritium concentrations higher than allowable. Further sampling and testing confirmed a Process Water System to Cooling Water System leak in heat exchanger 4A (HX 4A). The heat exchanger was isolated and the plant shutdown. Heat exchanger 4kA was removed from the plant and moved to C-Area prior to performing examinations and diagnostic testing. This included locating and identifying the leaking tube or tubes, eddy current examination of the leaking tube and a number of adjacent tubes, visually inspecting the leaking tube from both the inside as well as the area surrounding the failure mechanism. In addition ten other tubes that either exhibited eddy current indications or would represent a baseline condition were removed from heat exchanger 4A for metallurgical examination. Additional analysis and review of heat exchanger leakage history was performed to determine if there are any patterns which can be used for predictive purposes. Compensatory actions have been taken to improve the sensitivity and response time to any future events of this type. The results of these actions are summarized herein.

  4. Heat exchanger restart evaluation

    SciTech Connect

    Morrison, J.M.; Hirst, C.W.; Lentz, T.F.

    1992-03-18

    On December 24, 1991, the K-Reactor was in the shutdown mode with full AC process water flow and full cooling water flow. Safety rod testing was being performed as part of the power ascension testing program. The results of cooling water samples indicated tritium concentrations higher than allowable. Further sampling and testing confirmed a Process Water System to Cooling Water System leak in heat exchanger 4A (HX 4A). The heat exchanger was isolated and the plant shutdown. Heat exchanger 4A was removed from the plant and moved to C-Area prior to performing examinations and diagnostic testing. This included locating and identifying the leaking tube or tubes, eddy current examination of the leaking tube and a number of adjacent tubes, visually inspecting the leaking tube from both the inside as well as the area surrounding the identified tube. The leaking tube was removed and examined metallurgically to determine the failure mechanism. In addition ten other tubes that either exhibited eddy current indications or would represent a baseline condition were removed from heat exchanger 4A for metallurgical examination. Additional analysis and review of heat exchanger leakage history was performed to determine if there are any patterns which can be used for predictive purposes. Compensatory actions have been taken to improve the sensitivity and response time to any future events of this type. The results of these actions are summary herein.

  5. Heat exchanger restart evaluation

    SciTech Connect

    Morrison, J.M.; Hirst, C.W.; Lentz, T.F.

    1992-03-18

    On December 24, 1991, the K-Reactor was in the shutdown mode with full AC process water flow and full cooling water flow. Safety rod testing was being performed as part of the power ascension testing program. The results of cooling water samples indicated tritium concentrations higher than allowable. Further sampling and testing confirmed a Process Water System to Cooling Water System leak in heat exchanger 4A (HX 4A). The heat exchanger was isolated and the plant shutdown. Heat exchanger 4A was removed from the plant and moved to C-Area prior to performing examinations and diagnostic testing. This included locating and identifying the leaking tube or tubes, eddy current examination of the leaking tube and a number of adjacent tubes, visually inspecting the leaking tube from both the inside as well as the area surrounding the identified tube. The leaking tube was removed and examined metallurgically to determine the failure mechanism. In addition ten other tubes that either exhibited eddy current indications or would represent a baseline condition were removed from heat exchanger 4A for metallurgical examination. Additional analysis and review of heat exchanger leakage history was performed to determine if there are any patterns which can be used for predictive purposes. Compensatory actions have been taken to improve the sensitivity and response time to any future events of this type. The results of these actions are summarized.

  6. Downhole heat exchangers

    SciTech Connect

    Culver, G.; Lund, J.W.

    1999-09-01

    The downhole heat exchanger (DHE) eliminates the problem of disposal of geothermal fluid, since only heat is taken from the well. The exchanger consists of a system of pipes or tubes suspended in the well through which clean secondary water is pumped or allowed to circulate by natural convection. These systems offer substantial economic savings over surface heat exchangers where a single-well system is adequate (typically less than 0.8 MWt, with well depths up to about 500 ft) and may be economical under certain conditions at well depths to 1500 ft. Several designs have proven successful; but, the most popular are a simple hairpin loop or multiple loops of iron pipe (similar to the tubes in a U-tube and shell exchanger) extending to near the well bottom. An experimental design consisting of multiple small tubes with headers at each end suspended just below the water surface appears to offer economic and heating capacity advantages. The paper describes design and construction details and New Zealand`s experience with downhole heat exchangers.

  7. Shuffle-exchanges on augmented meshes

    NASA Technical Reports Server (NTRS)

    Bokhari, S. H.

    1984-01-01

    A mesh connected array of size N = two to the Kth power, K an integer, can be augmented by adding at most one edge per node such that it can perform a shuffle-exchange of size N/2 in constant time. A shuffle-exchange of size N is performed on this augmented array in constant time. This is done by combining the available perfect shuffle of size N/2 with the existing nearest neighbor connections of the mesh. By carefully scheduling the different permutations that are composed in order to achieve the shuffle, the time required is reduced to 5 steps, which is optimal for this network.

  8. Low exchange element for nuclear reactor

    DOEpatents

    Brogli, Rudolf H.; Shamasunder, Bangalore I.; Seth, Shivaji S.

    1985-01-01

    A flow exchange element is presented which lowers temperature gradients in fuel elements and reduces maximum local temperature within high temperature gas-cooled reactors. The flow exchange element is inserted within a column of fuel elements where it serves to redirect coolant flow. Coolant which has been flowing in a hotter region of the column is redirected to a cooler region, and coolant which has been flowing in the cooler region of the column is redirected to the hotter region. The safety, efficiency, and longevity of the high temperature gas-cooled reactor is thereby enhanced.

  9. Renormalized anisotropic exchange for representing heat assisted magnetic recording media

    SciTech Connect

    Jiao, Yipeng; Liu, Zengyuan; Victora, R. H.

    2015-05-07

    Anisotropic exchange has been incorporated in a description of magnetic recording media near the Curie temperature, as would be found during heat assisted magnetic recording. The new parameters were found using a cost function that minimized the difference between atomistic properties and those of renormalized spin blocks. Interestingly, the anisotropic exchange description at 1.5 nm discretization yields very similar switching and magnetization behavior to that found at 1.2 nm (and below) discretization for the previous isotropic exchange. This suggests that the increased accuracy of anisotropic exchange may also reduce the computational cost during simulation.

  10. Modular heat exchanger

    DOEpatents

    Culver, Donald W.

    1978-01-01

    A heat exchanger for use in nuclear reactors includes a heat exchange tube bundle formed from similar modules each having a hexagonal shroud containing a large number of thermally conductive tubes which are connected with inlet and outlet headers at opposite ends of each module, the respective headers being adapted for interconnection with suitable inlet and outlet manifold means. In order to adapt the heat exchanger for operation in a high temperature and high pressure environment and to provide access to all tube ports at opposite ends of the tube bundle, a spherical tube sheet is arranged in sealed relation across the chamber with an elongated duct extending outwardly therefrom to provide manifold means for interconnection with the opposite end of the tube bundle.

  11. Ion exchange phenomena

    SciTech Connect

    Bourg, I.C.; Sposito, G.

    2011-05-01

    Ion exchange phenomena involve the population of readily exchangeable ions, the subset of adsorbed solutes that balance the intrinsic surface charge and can be readily replaced by major background electrolyte ions (Sposito, 2008). These phenomena have occupied a central place in soil chemistry research since Way (1850) first showed that potassium uptake by soils resulted in the release of an equal quantity of moles of charge of calcium and magnesium. Ion exchange phenomena are now routinely modeled in studies of soil formation (White et al., 2005), soil reclamation (Kopittke et al., 2006), soil fertilitization (Agbenin and Yakubu, 2006), colloidal dispersion/flocculation (Charlet and Tournassat, 2005), the mechanics of argillaceous media (Gajo and Loret, 2007), aquitard pore water chemistry (Tournassat et al., 2008), and groundwater (Timms and Hendry, 2007; McNab et al., 2009) and contaminant hydrology (Chatterjee et al., 2008; van Oploo et al., 2008; Serrano et al., 2009).

  12. On exchangeable multinomial distributions

    PubMed Central

    George, E. Olusegun; Cheon, Kyeongmi; Yuan, Yilian; Szabo, Aniko

    2016-01-01

    We derive an expression for the joint distribution of exchangeable multinomial random variables, which generalizes the multinomial distribution based on independent trials while retaining some of its important properties. Unlike de Finneti's representation theorem for a binary sequence, the exchangeable multinomial distribution derived here does not require that the finite set of random variables under consideration be a subset of an infinite sequence. Using expressions for higher moments and correlations, we show that the covariance matrix for exchangeable multinomial data has a different form from that usually assumed in the literature, and we analyse data from developmental toxicology studies. The proposed analyses have been implemented in R and are available on CRAN in the CorrBin package.

  13. Microgravity condensing heat exchanger

    NASA Technical Reports Server (NTRS)

    Thomas, Christopher M. (Inventor); Ma, Yonghui (Inventor); North, Andrew (Inventor); Weislogel, Mark M. (Inventor)

    2011-01-01

    A heat exchanger having a plurality of heat exchanging aluminum fins with hydrophilic condensing surfaces which are stacked and clamped between two cold plates. The cold plates are aligned radially along a plane extending through the axis of a cylindrical duct and hold the stacked and clamped portions of the heat exchanging fins along the axis of the cylindrical duct. The fins extend outwardly from the clamped portions along approximately radial planes. The spacing between fins is symmetric about the cold plates, and are somewhat more closely spaced as the angle they make with the cold plates approaches 90.degree.. Passageways extend through the fins between vertex spaces which provide capillary storage and communicate with passageways formed in the stacked and clamped portions of the fins, which communicate with water drains connected to a pump externally to the duct. Water with no entrained air is drawn from the capillary spaces.

  14. Enhanced exchange algorithm without detailed balance condition for replica exchange method

    NASA Astrophysics Data System (ADS)

    Kondo, Hiroko X.; Taiji, Makoto

    2013-06-01

    The replica exchange method (REM) is a powerful tool for the conformational sampling of biomolecules. In this study, we propose an enhanced exchange algorithm for REM not meeting the detailed balance condition (DBC), but satisfying the balance condition in all considered exchanges between two replicas. Breaking the DBC can minimize the rejection rate and make an exchange process rejection-free as the number of replicas increases. To enhance the efficiency of REM, all possible pairs—not only the nearest neighbor—were considered in the exchange process. The test simulations of the alanine dipeptide confirmed the correctness of our method. The average traveling distance of each replica in the temperature distribution was also increased in proportion to an increase in the exchange rate. Furthermore, we applied our algorithm to the conformational sampling of the 10-residue miniprotein, chignolin, with an implicit solvent model. The results showed a faster convergence in the calculation of its free energy landscape, compared to that achieved using the normal exchange method of adjacent pairs. This algorithm can also be applied to the conventional near neighbor method and is expected to reduce the required number of replicas.

  15. Heat exchanger panel

    NASA Technical Reports Server (NTRS)

    Warburton, Robert E. (Inventor); Cuva, William J. (Inventor)

    2005-01-01

    The present invention relates to a heat exchanger panel which has broad utility in high temperature environments. The heat exchanger panel has a first panel, a second panel, and at least one fluid containment device positioned intermediate the first and second panels. At least one of the first panel and the second panel have at least one feature on an interior surface to accommodate the at least one fluid containment device. In a preferred embodiment, each of the first and second panels is formed from a high conductivity, high temperature composite material. Also, in a preferred embodiment, the first and second panels are joined together by one or more composite fasteners.

  16. Alert Exchange Process Protocol

    NASA Technical Reports Server (NTRS)

    Groen, Frank

    2015-01-01

    The National Aeronautics and Space Administration of the United States of America (NASA), and the European Space Agency (ESA), and the Japanese Aerospace Exploration Agency (JAXA), acknowledging that NASA, ESA and JAXA have a mutual interest in exchanging Alerts and Alert Status Lists to enhance the information base for each system participant while fortifying the general level of cooperation between the policy agreement subscribers, and each Party will exchange Alert listings on regular basis and detailed Alert information on a need to know basis to the extent permitted by law.

  17. Securities and Exchange Commission Semiannual Regulatory Agenda

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-26

    ... [Securities and Exchange Commission Semiannual Regulatory Agenda ] Part XXIII Securities and Exchange Commission Semiannual Regulatory Agenda ] SECURITIES AND EXCHANGE COMMISSION (SEC) SECURITIES AND EXCHANGE COMMISSION 17 CFR Ch. II Regulatory Flexibility Agenda AGENCY: Securities and Exchange Commission. ACTION: Semiannual regulatory...

  18. DHE (downhole heat exchangers). [Downhole Heat Exchangers (DHE)

    SciTech Connect

    Culver, G.

    1990-11-01

    The use of downhole heat exchangers (DHE) for residential or commercial space and domestic water heating and other applications has several desirable features. Systems are nearly or completely passive -- that is, no or very little geothermal water or steam is produced from the well either reducing or completely eliminating surface environmental concerns and the need for disposal systems or injection wells. Initial cost of pumps and installation are eliminated or reduced along with pumping power costs and maintenance costs associated with pumping often corrosive geothermal fluids. Many residential and small commercial systems do not require circulating pumps because the density difference in the incoming and outgoing sides of the loop are sufficient to overcome circulating friction losses in the entire system. The major disadvantage of DHEs is their dependence on natural heat flow. In areas where geological conditions provide high permeability and a natural hydraulic gradient, DHEs can provide a substantial quantity of heat. A single 500-ft (152 m) well in Klamath Falls, Oregon, supplies over one megawatt thermal and output is apparently limited by the surface area of pipe that can be installed in the well bore. In contrast, DHEs used in conjunction with heat pumps may supply less than 8 KW from a well of similar depth. Here output is limited by conductive heat flow with perhaps a small contribution from convection near the well bore. The highest capacity DHE reported to date, in Turkey, supplies 6 MW thermal from an 820-ft (250 m) well. There were two main goals for this project. The first was to gather, disseminate and exchange internationally information on DHES. The second was to perform experiments that would provide insight into well bore/aquifer interaction and thereby provide more information on which to base DHE designs. 27 refs., 31 figs., 3 tabs.

  19. Exchange of astronomy teaching experiences

    NASA Astrophysics Data System (ADS)

    Ros, Rosa M.

    The Working Group of the European Association for Astronomy Education responsible for Teacher Training organises an annual Summer School for teachers under expert guidance. For a week the teachers participating can exchange experiences, increase their knowledge and discuss different ideas and perspectives. In general, the instructors are professional astronomers, professors and teachers from different countries. The papers presented offer very practical activities, paying special attention to didactic aspects, and take the form of general lectures to all 40 participants and workshops to reduced groups of 20 participants. There are also day and night observations, without expensive equipment or complicated procedures, that are easy to set up and based on topics that it is possible to use in the classroom. The Summer Schools promote a scientific astronomical education at all levels of astronomy teaching, reinforce the link between professional astronomers and teachers with experience of teaching astronomy, allow debates among the participants on their pedagogical activities already carried out in their own classroom and help them to organise activities outside it. Astronomy teachers need special training, access to specific research, to new educational materials and methods and the opportunity to exchange experiences. All these things are provided by the Summer School.

  20. The roles of carbon and grain boundary carbides on the intergranular corrosion cracking behavior of Ni-16Cr-9Fe-xC alloys at 360 degrees C

    NASA Astrophysics Data System (ADS)

    Hertzberg, Jason Lyle

    The roles of carbon and grain boundary carbides on the creep and cracking behaviors of controlled purity Ni-16Cr-9Fe-xC alloys at 360sp°C were both isolated and determined in order to better understand the effect of carbon distribution on intergranular stress corrosion cracking (IGSCC) behavior. Constant load tensile (CLT) tests were conducted in 360sp°C argon and primary water in order to determine relative creep susceptibilities, while constant extension rate tensile (CERT) tests were performed in 360sp°C argon and primary water environments to study relative cracking propensities. Solid solution carbon increases the creep resistance of Ni-16Cr-9Fe-xC alloys at 360sp°C by delaying the recovery process of climb in the grain boundary. Grain boundary recovery rates were estimated by performing in situ TEM grain boundary dislocation spreading experiments to determine grain boundary diffusivities. The addition of 65 wppm carbon in solution serves to lower the grain boundary diffusivity and grain boundary recovery rate by over 4 orders of magnitude. As a result of lowering the grain boundary diffusivity, solid solution carbon suppresses both grain boundary sliding and cavitation. Grain boundary carbides decrease the creep resistance of Ni-16Cr-9Fe-xC alloys at 360sp°C compared to a microstucture containing all carbon in solution, but increase IGSCC resistance in primary water environments containing 0, 1, and 18 bar hydrogen overpressures. The magnitude of the beneficial effect of the grain boundary carbides is strongly dependent upon hydrogen overpressure. The superior IGSCC resistance of a microstrucutre containing grain boundary carbides can be attributed to its highest overall resistance to both creep and environmentally induced cracking. The detrimental effect of hydrogen on the IGSCC resistance shows consistencies with both the film rupture/slip dissolution and hydrogen embrittlement cracking mechanisms. It is proposed that carbon distribution influences the

  1. Currency Exchange Rates.

    ERIC Educational Resources Information Center

    Siler, Carl R.

    This curriculum unit of the Muncie (Indiana) Southside High School is to simulate the dynamics of foreign currency exchange rates from the perspectives of: (1) a major U.S. corporation, ABB Power T & D Company, Inc., of Muncie, Indiana, a manufacturer of large power transformers for the domestic and foreign markets; and (2) individual consumers…

  2. Estimate exchanger vibration

    SciTech Connect

    Nieh, C.D.; Zengyan, H.

    1986-04-01

    Based on the classical beam theory, a simple method for calculating the natural frequency of unequally spanned tubes is presented. The method is suitable for various boundary conditions. Accuracy of the calculations is sufficient for practical applications. This method will help designers and operators estimate the vibration of tubular exchangers. In general, there are three reasons why a tube vibrates in cross flow: vortex shedding, fluid elasticity and turbulent buffeting. No matter which is the cause, the basic reason is that the frequency of exciting force is approximately the same as or equal to the natural frequency of the tube. To prevent the heat exchanger from vibrating, it is necessary to select correctly the shell-side fluid velocity so that the frequency of exciting force is different from the natural frequency of the tube, or to vary the natural frequency of the heat exchanger tube. So precisely determining the natural frequency of the heat exchanger, especially its foundational frequency under various supporting conditions, is of significance.

  3. Research Exchange, 2002.

    ERIC Educational Resources Information Center

    Research Exchange, 2002

    2002-01-01

    These three issues of the "Research Exchange" focus on how better to conduct disability research and disseminate research results. The first issue examines the topic of human subject/human research participant protection, with a focus on research funded through the National Institute on Disability and Rehabilitation Research (NIDRR). It provides…

  4. Higher Education Exchange 2006

    ERIC Educational Resources Information Center

    Brown, David W., Ed.; Witte, Deborah, Ed.

    2006-01-01

    Contributors to this issue of the Higher Education Exchange debate the issues around knowledge production, discuss the acquisition of deliberative skills for democracy, and examine how higher education prepares, or does not prepare, students for citizenship roles. Articles include: (1) "Foreword" (Deborah Witte); (2) "Knowledge, Judgment and…

  5. Technology Performance Exchange

    SciTech Connect

    2015-09-01

    To address the need for accessible, high-quality data, the Department of Energy has developed the Technology Performance Exchange (TPEx). TPEx enables technology suppliers, third-party testing laboratories, and other entities to share product performance data. These data are automatically transformed into a format that technology evaluators can easily use in their energy modeling assessments to inform procurement decisions.

  6. Heat exchange enhancement structure

    SciTech Connect

    Cornelison, R.C.; Kreith, F.

    1980-12-02

    A passive heat exchange enhancement structure which operates by free convection includes a flat mounting portion having a plurality of integral fins bent outwardly from one side edge thereof. The mounting portion is securable around a stovepipe, to a flat surface or the like for transferring heat from the pipe through the fins to the surrounding air by rotation-enhanced free convection.

  7. Higher Education Exchange, 2014

    ERIC Educational Resources Information Center

    Brown, David W., Ed.; Witte, Deborah, Ed.

    2014-01-01

    Research shows that not only does higher education not see the public; when the public, in turn, looks at higher education, it sees mostly malaise, inefficiencies, expense, and unfulfilled promises. Yet, the contributors to this issue of the "Higher Education Exchange" tell of bright spots in higher education where experiments in working…

  8. Nature's Heat Exchangers.

    ERIC Educational Resources Information Center

    Barnes, George

    1991-01-01

    Discusses the heat-transfer systems of different animals. Systems include heat conduction into the ground, heat transferred by convection, heat exchange in lizards, fish and polar animals, the carotid rete system, electromagnetic radiation from animals and people, and plant and animal fiber optics. (MDH)

  9. Chimney heat exchanger

    SciTech Connect

    Whiteley, I.C.

    1981-09-01

    A heat exchanger for installation on the top of a chimney of a building includes a housing having a lower end receiving the top of the chimney and an upper end with openings permitting the escape of effluent from the chimney and a heat exchanger assembly disposed in the housing including a central chamber and a spirally arranged duct network defining an effluent spiral path between the top of the chimney and the central chamber and a fresh air spiral path between an inlet disposed at the lower end of the housing and the central chamber, the effluent and fresh air spiral paths being in heat exchange relationship such that air passing through the fresh air spiral path is heated by hot effluent gases passing upward through the chimney and the effluent spiral path for use in heating the building. A pollution trap can be disposed in the central chamber of the heat exchanger assembly for removing pollutants from the effluent, the pollution trap including a rotating cage carrying pumice stones for absorbing pollutants from the effluent with the surface of the pumice gradually ground off to reveal fresh stone as the cage rotates.

  10. Visiting Scholar Exchange Reports.

    ERIC Educational Resources Information Center

    Rubin, Kyna, Ed.

    1986-01-01

    Provides reports of four United States scholars who visited China as part of the Visiting Scholar Exchange Program. The titles of the reports are (1) "China Journey: A Political Scientist's Look at Yan'an," (2) "The Social Consequences of Land Reclamation in Chinese Coastal Ecosystems," (3) "Anthropology Lectures in South China," and (4) "The Use…

  11. Higher Education Exchange

    ERIC Educational Resources Information Center

    Brown, David W., Ed.; Witte, Deborah, Ed.

    2009-01-01

    This volume begins with an essay by Noelle McAfee, a contributor who is familiar to readers of Higher Education Exchange (HEX). She reiterates Mathews' argument regarding the disconnect between higher education's sense of engagement and the public's sense of engagement, and suggests a way around the epistemological conundrum of "knowledge produced…

  12. Higher Education Exchange, 2009

    ERIC Educational Resources Information Center

    Brown, David W., Ed.; Witte, Deborah, Ed.

    2009-01-01

    This volume begins with an essay by Noelle McAfee, a contributor who is familiar to readers of Higher Education Exchange (HEX). She reiterates Kettering's president David Mathews' argument regarding the disconnect between higher education's sense of engagement and the public's sense of engagement, and suggests a way around the epistemological…

  13. Hydrogen exchange in thermally denatured ribonuclease A

    SciTech Connect

    Robertson, A.D.; Baldwin, R.L. )

    1991-10-15

    Hydrogen exchange has been used to test for the presence of nonrandom structure in thermally denatured ribonuclease A (RNase A). Quenched-flow methods and 2d {sup 1}H NMR spectroscopy were used to measure exchange rates for 36 backbone amide protons (NHs) at 65C and at pH* (uncorrected pH measured in D{sub 2}O) values ranging from 1.5 to 3.8. The results show that exchange is approximately that predicted for a disordered polypeptide, the authors thus are unable to detect any stable hydrogen-bonded structure in thermally denatured RNase A. Two observations suggest, however, that the predicted rates should be viewed with some caution. First, they discovered that one of the approximations made by Molday et al, that exchange for valine NHs is similar to that for alanine NHs, had to modified; the exchange rates for valine NHs are about 4-fold slower. Second, the pH minima for exchange tend to fall at lower pH values than predicted, by as much as 0.45 pH units. The origin of the disagreement between predicted and observed pH minima is unknown but may be the high net positive charge on these proteins at low pH. This spectrum is reduced to a low level by adding guanidine hydrochloride. The nature of the residual structure responsible for this spectrum is not known. The results show that it is not stable helix formation by the three {alpha}-helices of native ribonuclease A, which would give measurable protection against amide proton exchange.

  14. Composite ion exchange materials

    SciTech Connect

    Amarasinghe, S.; Zook, L.; Leddy, J.

    1994-12-31

    Composite ion exchange materials can be formed by sorbing ion exchange polymers on inert, high surface area substrates. In general, the flux of ions and molecules through these composites, as measured electrochemically, increases as the ratio of the surface area of the substrate increases relative to the volume of the ion exchanger. This suggests that fields and gradients established at the interface between the ion exchanger and substrate are important in determining the transport characteristics of the composites. Here, the authors will focus on composites formed with a cation exchange polymer, Nafion, and two different types of microbeads: polystyrene microspheres and polystyrene coated magnetic microbeads. For the polystyrene microbeads, scanning electron micrographs suggest the beads cluster in a self-similar manner, independent of the bead diameter. Flux of Ru(NH3)63+ through the composites was studied as a function of bead fraction, bead radii, and fixed surface area with mixed bead sizes. Flux was well modeled by surface diffusion along a fractal interface. Magnetic composites were formed with columns of magnetic microbeads normal to the electrode surface. Flux of Ru(NH3)63+ through these composites increased exponentially with bead fraction. For electrolyses, the difference in the molar magnetic susceptibility of the products and reactants, Dcm, tends to be non-zero. For seven redox reactions, the ratio of the flux through the magnetic composites to the flux through a Nafion film increases monotonically with {vert_bar}Dcm{vert_bar}, with enhancements as large as thirty-fold. For reversible species, the electrolysis potential through the magnetic composites is 35 mV positive of that for the Nafion films.

  15. Slotting Fins of Heat Exchangers to Provide Thermal Breaks

    NASA Technical Reports Server (NTRS)

    Scull, Timothy D.

    2003-01-01

    Heat exchangers that include slotted fins (in contradistinction to continuous fins) have been invented. The slotting of the fins provides thermal breaks that reduce thermal conduction along flow paths (longitudinal thermal conduction), which reduces heat-transfer efficiency. By increasing the ratio between transverse thermal conduction (the desired heat-transfer conduction) and longitudinal thermal conduction, slotting of the fins can be exploited to (1) increase heat-transfer efficiency (thereby reducing operating cost) for a given heat-exchanger length or to (2) reduce the length (thereby reducing the weight and/or cost) of the heat exchanger needed to obtain a given heat transfer efficiency. By reducing the length of a heat exchanger, one can reduce the pressure drop associated with the flow through it. In a case in which slotting enables the use of fins with thermal conductivity greater than could otherwise be tolerated on the basis of longitudinal thermal conduction, one can exploit the conductivity to make the fins longer (in the transverse direction) than they otherwise could be, thereby making it possible to make a heat exchanger that contains fewer channels and therefore, that weighs less, contains fewer potential leak paths, and can be constructed from fewer parts and, hence, reduced cost.

  16. Development, Fabrication, and Testing of a Liquid/Liquid Microchannel Heat Exchanger for Constellation Spacecrafts

    NASA Technical Reports Server (NTRS)

    Hawkins-Reynolds, Ebony; Le,Hung; Stephans, Ryan A.

    2009-01-01

    Minimizing mass and volume is critically important for space hardware. Microchannel technology can be used to decrease both of these parameters for heat exchangers. Working in concert with NASA, Pacific Northwest National Laboratories (PNNL) has developed a microchannel liquid/liquid heat exchanger that has resulted in significant mass and volume savings. The microchannel heat exchanger delivers these improvements without sacrificing thermal and pressure drop performance. A conventional heat exchanger has been tested and the performance of it recorded to compare it to the microchannel heat exchanger that PNNL has fabricated. The microchannel heat exchanger was designed to meet all of the requirements of the baseline heat exchanger, while reducing the heat exchanger mass and volume. The baseline heat exchanger was designed to have an transfer approximately 3.1 kW for a specific set of inlet conditions. The baseline heat exchanger mass was 2.7 kg while the microchannel mass was only 2.0 kg. More impressive, however, was the volumetric savings associated with the microchannel heat exchanger. The microchannel heat exchanger was an order of magnitude smaller than the baseline heat exchanger (2180cm3 vs. 311 cm3). This paper will describe the test apparatus designed to complete performance tests for both heat exchangers. Also described in this paper will be the performance specifications for the microchannel heat exchanger and how they compare to the baseline heat exchanger.

  17. A corrosive resistant heat exchanger

    DOEpatents

    Richlen, S.L.

    1987-08-10

    A corrosive and erosive resistant heat exchanger which recovers heat from a contaminated heat stream. The heat exchanger utilizes a boundary layer of innocuous gas, which is continuously replenished, to protect the heat exchanger surface from the hot contaminated gas. The innocuous gas is pumped through ducts or perforations in the heat exchanger wall. Heat from the heat stream is transferred by radiation to the heat exchanger wall. Heat is removed from the outer heat exchanger wall by a heat recovery medium. 3 figs., 3 tabs.

  18. Treatment of Pica Using a Pica Exchange Procedure with Increasing Response Effort

    ERIC Educational Resources Information Center

    Carter, Stacy L.

    2009-01-01

    The effects of a pica exchange procedure were evaluated on the pica of a female with severe mental retardation. A BAB design revealed that the pica exchange procedure was effective at reducing the occurrence of pica. In addition, the pica exchange procedure was effective throughout six increasingly more difficult response effort conditions.…

  19. Phosphonic acid based exchange resins

    DOEpatents

    Horwitz, E. Philip; Alexandratos, Spiro D.; Gatrone, Ralph C.; Chiarizia, Ronato

    1995-01-01

    An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene.

  20. Phosphonic acid based exchange resins

    DOEpatents

    Horwitz, E.P.; Alexandratos, S.D.; Gatrone, R.C.; Chiarizia, R.

    1995-09-12

    An ion exchange resin is described for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene. 10 figs.

  1. Lipid Exchange by Ultracentrifugation.

    PubMed

    Drachmann, Nikolaj Düring; Olesen, Claus

    2016-01-01

    Lipids play an important role in maintaining P-type ATPase structure and function, and often they are crucial for ATPase activity. When the P-type ATPases are in the membrane, they are surrounded by a mix of different lipid species with varying aliphatic chain lengths and saturation, and the complex interplay between the lipids and the P-type ATPases are still not well understood. We here describe a robust method to exchange the majority of the lipids surrounding the ATPase after solubilisation and/or purification with a target lipid of interest. The method is based on an ultracentrifugation step, where the protein sample is spun through a dense buffer containing large excess of the target lipid, which results in an approximately 80-85 % lipid exchange. The method is a very gently technique that maintains protein folding during the process, hence allowing further characterization of the protein in the presence of a target lipid of interest. PMID:26695050

  2. Heat exchanger tube mounts

    DOEpatents

    Wolowodiuk, W.; Anelli, J.; Dawson, B.E.

    1974-01-01

    A heat exchanger in which tubes are secured to a tube sheet by internal bore welding is described. The tubes may be moved into place in preparation for welding with comparatively little trouble. A number of segmented tube support plates are provided which allow a considerable portion of each of the tubes to be moved laterally after the end thereof has been positioned in preparation for internal bore welding to the tube sheet. (auth)

  3. Thermoelectric heat exchange element

    DOEpatents

    Callas, James J.; Taher, Mahmoud A.

    2007-08-14

    A thermoelectric heat exchange module includes a first substrate including a heat receptive side and a heat donative side and a series of undulatory pleats. The module may also include a thermoelectric material layer having a ZT value of 1.0 or more disposed on at least one of the heat receptive side and the heat donative side, and an electrical contact may be in electrical communication with the thermoelectric material layer.

  4. Heat exchange apparatus

    DOEpatents

    Degtiarenko, Pavel V.

    2003-08-12

    A heat exchange apparatus comprising a coolant conduit or heat sink having attached to its surface a first radial array of spaced-apart parallel plate fins or needles and a second radial array of spaced-apart parallel plate fins or needles thermally coupled to a body to be cooled and meshed with, but not contacting the first radial array of spaced-apart parallel plate fins or needles.

  5. Soviets seek scientific exchange

    NASA Astrophysics Data System (ADS)

    GEOS-A, associated with the Soviet Union's Institute of Earth Physics, is seeking to promote exchange between Soviet and Western geophysicists. GEOS-A is a nonprofit, private organization formed by specialists from the U.S.S.R. Academy of Scientists.GEOS-A aims to promote the transfer of academic research results to industry and education. It also seeks to stimulate international scientific exchange and to support independent nongovernmental programs and expertise in geophysics and ecology. The organization would like to cooperate with Western universities in exchanging students and young scientists and in building scientific relationships between the two countries. This would include inviting students and young specialists for collaborative scientific research, consultations, language practice, and graduate study in any institute of the U.S.S.R. Academy of Sciences. Participants would live in rented private apartments in downtown Moscow for approximately one week to several months. All living expenses would be covered at a rate higher than the academy's standard one (unfortunately travel to and from the Soviet Union cannot be covered).

  6. The exchangeability of shape

    PubMed Central

    2010-01-01

    Background Landmark based geometric morphometrics (GM) allows the quantitative comparison of organismal shapes. When applied to systematics, it is able to score shape changes which often are undetectable by traditional morphological studies and even by classical morphometric approaches. It has thus become a fast and low cost candidate to identify cryptic species. Due to inherent mathematical properties, shape variables derived from one set of coordinates cannot be compared with shape variables derived from another set. Raw coordinates which produce these shape variables could be used for data exchange, however they contain measurement error. The latter may represent a significant obstacle when the objective is to distinguish very similar species. Results We show here that a single user derived dataset produces much less classification error than a multiple one. The question then becomes how to circumvent the lack of exchangeability of shape variables while preserving a single user dataset. A solution to this question could lead to the creation of a relatively fast and inexpensive systematic tool adapted for the recognition of cryptic species. Conclusions To preserve both exchangeability of shape and a single user derived dataset, our suggestion is to create a free access bank of reference images from which one can produce raw coordinates and use them for comparison with external specimens. Thus, we propose an alternative geometric descriptive system that separates 2-D data gathering and analyzes. PMID:20964872

  7. Building partnerships -- The Ohio Materials Exchange

    SciTech Connect

    Covey, S.K.

    1999-07-01

    As this century comes to a close, landfills are being opened, closed and mined for resources; commercial businesses and manufacturers are under pressure to be responsible both environmentally and economically. The timing is right for individuals and organizations to start listening to each other and working cooperatively for a greater good. In 1996, an ad hoc group of state government agencies, private business, not-for-profits and educational institutions met to discuss the potential for a materials exchange in Ohio. The Ohio Materials Exchange (OMEX) exists today from the cooperation and funding form the Ohio Environmental Education Fund (OEEF), The Association of Ohio Recyclers (AOR) in cooperation with Waste Alternatives, Inc., The Ohio Environmental Protection Agency (OhEPA) (Division of Solid and Infectious Waste Management and the Office of Pollution Prevention), The Ohio Department of Natural Resources (Division of Recycling and Litter Prevention) and the Ohio Department of Development (ODOD) (Office of Energy Efficiency OEE). In addition, private business, solid waste management districts and individual organizations who use the exchange actively help guide and market the program. The author was employed with the ODOD-OEE and a member of the planning team. A materials exchange allows companies to trade, sell or give away unwanted materials to one another and use it as raw material for manufacturing or reuse in its existing form (Table 1.). Materials exchanges were both out of necessity in World War II but are continuing due to foresight. (EPA 1994) The exchange of raw product, rejects or waste can reduce waste and save energy. Not only do recycled materials often use less energy to produce the product, the trading may save hauling or disposal costs, that could then be diverted to purchase new, more efficient equipment. The materials available or wanted are collected into lists. These lists may take the form of catalogs, fax-back systems, Internet or

  8. AGRICULTURAL EXCHANGE RATE DATA SHEET

    EPA Science Inventory

    The ERS data set contains annual and monthly data for exchange rates important to U.S. agriculture. It includes both nominal and real exchange rates for 80 countries (plus the European Union) as well as real trade-weighted exchange rate indexes for many commodities and aggregatio...

  9. Thrombotic thrombocytopenic purpura treated with plasma exchange or exchange transfusions.

    PubMed Central

    Shepard, K. V.; Fishleder, A.; Lucas, F. V.; Goormastic, M.; Bukowski, R. M.

    1991-01-01

    Of 40 patients with thrombotic thrombocytopenic purpura, 17 were treated with plasma exchange, 15 with exchange transfusions, and 6 with both types of therapy. One patient died before being treated and another patient was seen but not treated. Plasma exchange was performed daily for a mean of seven exchanges per patient. The replacement fluid during plasma exchange was fresh frozen plasma in all cases. The complete response rates for each type of treatment were as follows: 88% for plasma exchange (15 patients), 47% for exchange transfusions (7 patients), and 67% for exchange transfusions and plasma exchange (4 patients). Clinical and laboratory factors were examined for any statistically significant association with therapy response. Treatment with plasma exchange was statistically the initial factor most strongly associated with prognosis. Paresis, paresthesias, seizures, mental status change, and coma showed no association with response to treatment. Some of the laboratory factors that did not show significant association with treatment response were the initial creatinine, hemoglobin, platelet count, lactate dehydrogenase, and total bilirubin. This study supports the hypothesis that plasma exchange has significantly improved the prognosis of patients with thrombotic thrombocytopenic purpura. These patients should be treated aggressively regardless of the severity of their symptoms. PMID:1877181

  10. Minimizing back exchange in the hydrogen exchange-mass spectrometry experiment.

    PubMed

    Walters, Benjamin T; Ricciuti, Alec; Mayne, Leland; Englander, S Walter

    2012-12-01

    The addition of mass spectrometry (MS) analysis to the hydrogen exchange (HX) proteolytic fragmentation experiment extends powerful HX methodology to the study of large biologically important proteins. A persistent problem is the degradation of HX information due to back exchange of deuterium label during the fragmentation-separation process needed to prepare samples for MS measurement. This paper reports a systematic analysis of the factors that influence back exchange (solution pH, ionic strength, desolvation temperature, LC column interaction, flow rates, system volume). The many peptides exhibit a range of back exchange due to intrinsic amino acid HX rate differences. Accordingly, large back exchange leads to large variability in D-recovery from one residue to another as well as one peptide to another that cannot be corrected for by reference to any single peptide-level measurement. The usual effort to limit back exchange by limiting LC time provides little gain. Shortening the LC elution gradient by 3-fold only reduced back exchange by ~2%, while sacrificing S/N and peptide count. An unexpected dependence of back exchange on ionic strength as well as pH suggests a strategy in which solution conditions are changed during sample preparation. Higher salt should be used in the first stage of sample preparation (proteolysis and trapping) and lower salt (<20 mM) and pH in the second stage before electrospray injection. Adjustment of these and other factors together with recent advances in peptide fragment detection yields hundreds of peptide fragments with D-label recovery of 90% ± 5%. PMID:22965280

  11. A cryogenic heat exchanger with bypass and throttling and its thermodynamic analysis

    NASA Astrophysics Data System (ADS)

    Tao, X.; Liu, D. L.; Wang, L. Y.; Shen, J.; Gan, Z. H.

    2015-12-01

    A precooled Joule-Thomson (J-T) cooler refrigerates at liquid helium temperature. Its third stage heat exchanger works below 20 K. Hot fluid cannot be sufficiently cooled due to nonidealism of the heat exchanger and helium-4 properties. In a J-T cycle of low pressure ratio, the heat exchanger with bypass and throttling improves the refrigeration capacity. Bypass and throttling reduces the temperature difference and entropy generation within the heat exchanger.

  12. Lightweight Long Life Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Moore, E. K.

    1976-01-01

    A shuttle orbiter flight configuration aluminum heat exchanger was designed, fabricated, and tested. The heat exchanger utilized aluminum clad titanium composite parting sheets for protection against parting sheet pin hole corrosion. The heat exchanger, which is fully interchangeable with the shuttle condensing heat exchanger, includes slurpers (a means for removing condensed water from the downstream face of the heat exchanger), and both the core air passes and slurpers were hydrophilic coated to enhance wettability. The test program included performance tests which demonstrated the adequacy of the design and confirmed the predicted weight savings.

  13. Emittance and Phase Space Exchange

    SciTech Connect

    Xiang, Dao; Chao, Alex; /SLAC

    2011-08-19

    Alternative chicane-type beam lines are proposed for exact emittance exchange between horizontal phase space (x; x{prime}) and longitudinal phase space (z; {delta}). Methods to achieve exact phase space exchanges, i.e. mapping x to z, x{prime} to {delta}, z to x and {delta} to x{prime} are suggested. Methods to mitigate the thick-lens effect of the transverse cavity on emittance exchange are discussed. Some applications of the phase space exchanger and the feasibility of an emittance exchange experiment with the proposed chicane-type beam line at SLAC are discussed.

  14. Reduced Sensitivity to Charge Noise in Semiconductor Spin Qubits via Symmetric Operation

    NASA Astrophysics Data System (ADS)

    Reed, M. D.; Maune, B. M.; Andrews, R. W.; Borselli, M. G.; Eng, K.; Jura, M. P.; Kiselev, A. A.; Ladd, T. D.; Merkel, S. T.; Milosavljevic, I.; Pritchett, E. J.; Rakher, M. T.; Ross, R. S.; Schmitz, A. E.; Smith, A.; Wright, J. A.; Gyure, M. F.; Hunter, A. T.

    2016-03-01

    We demonstrate improved operation of exchange-coupled semiconductor quantum dots by substantially reducing the sensitivity of exchange operations to charge noise. The method involves biasing a double dot symmetrically between the charge-state anticrossings, where the derivative of the exchange energy with respect to gate voltages is minimized. Exchange remains highly tunable by adjusting the tunnel coupling. We find that this method reduces the dephasing effect of charge noise by more than a factor of 5 in comparison to operation near a charge-state anticrossing, increasing the number of observable exchange oscillations in our qubit by a similar factor. Performance also improves with exchange rate, favoring fast quantum operations.

  15. The Dynamics of Multilateral Exchange

    NASA Astrophysics Data System (ADS)

    Hausken, Kjell; Moxnes, John F.

    The article formulates a dynamic mathematical model where arbitrarily many players produce, consume, exchange, loan, and deposit arbitrarily many goods over time to maximize utility. Consuming goods constitutes a benefit, and producing, exporting, and loaning away goods constitute a cost. Utilities are benefits minus costs, which depend on the exchange ratios and bargaining functions. Three-way exchange occurs when one player acquires, through exchange, one good from another player with the sole purpose of using this good to exchange against the desired good from a third player. Such a triple handshake is not merely a set of double handshakes since the player assigns no interest to the first good in his benefit function. Cognitive and organization costs increase dramatically for higher order exchanges. An exchange theory accounting for media of exchange follows from simple generalization of two-way exchange. The examples of r-way exchange are the triangle trade between Africa, the USA, and England in the 17th and 18th centuries, the hypothetical hypercycle involving RNAs as players and enzymes as goods, and reaction-diffusion processes. The emergence of exchange, and the role of trading agents are discussed. We simulate an example where two-way exchange gives zero production and zero utility, while three-way exchange causes considerable production and positive utility. Maximum utility for each player is reached when exchanges of the same order as the number of players in society are allowed. The article merges micro theory and macro theory within the social, natural, and physical sciences.

  16. Cesium Separation Using Electrically Switched Ion Exchange

    SciTech Connect

    Lilga, Michael A.); Orth, Rick J.); Sukamto, Johanes H.); Rassat, Scot D.); Genders, J D.; Gopal, R

    2001-09-01

    Electrically Switched Ion Exchange (ESIX) is a separation technology being developed at Pacific Northwest National Laboratory as an alternative to conventional ion exchange for removing metal ions from wastewater. In ESIX, which combines ion exchange and electro-chemistry, ion uptake and elution can be controlled directly by modulating the potential of an ion exchange film that has been electrochemically deposited onto an electrode. This paper presents the results of experiments on high surface area electrodes and the development of a flow system for cesium ion separation. Bench-scale flow system studies showed no change in capacity or performance of the ESIX films at a flow rate up to 113 BV/h, the maxi-mum flow rate tested, and breakthrough curves supported once-through waste processing. A comparison of results for a stacked 5-electrode cell versus a single-electrode cell showed enhanced breakthrough performance. In the stacked configuration, break-through began at about 120 BV for a feed containing 0.2 ppm cesium at a flow rate of 13 BV/h. A case study for the KE Basin (a spent nuclear fuel storage basin) on the Hanford Site demonstrated that KE Basin wastewater could be processed continuously with minimal waste generation, reduced disposal costs, and lower capital expenditures.

  17. Quantifying exchange coupling in segregated granular materials

    NASA Astrophysics Data System (ADS)

    Morrison, C.; Saharan, L.; Ikeda, Y.; Takano, K.; Hrkac, G.; Thomson, T.

    2013-11-01

    The volume of a magnetic grain, together with its anisotropy, determines the probability of thermally activated reversal. Thus for grain volume distributions where the median volume is close to the superparamagnetic limit there will be a sub-set of grains which are either superparamagnetic on the time scale of a typical magnetic measurement (10 s), or the reverse due to magnetostatic fields from surrounding grains. We use this effect to probe exchange coupling in segregated granular materials, using CoCrPt-SiOx granular recording media as model systems. As the film thickness is reduced below 10 nm, the remanent magnetization of these films decreases, due to thermal activation and magnetostatic reversal. Varying film thickness and temperature allows us to thermally select a population of grains that contribute to the measurement. Exchange coupling is characterized by the angle dependence of remanent coercivity where we associate a breaking of symmetry from the Stoner-Wohlfarth model towards the Kondorsky model as a measure of the incoherency of reversal. Combining these models allows an estimate to be made of the volume fraction of grains that are exchange coupled and we find that, for well segregated CoCrPt-SiOx media, approximately 8% of the magnetic volume undergoes some degree of exchange coupling.

  18. Exchange lists: revised 1986.

    PubMed

    Franz, M J; Barr, P; Holler, H; Powers, M A; Wheeler, M L; Wylie-Rosett, J

    1987-01-01

    A committee composed of members of The American Dietetic Association and the American Diabetes Association has revised Exchange List for Meal Planning. Changes were made, as deemed necessary, on the basis of nutritional recommendations for persons with diabetes as understood in 1986. Major changes include rewriting the text to make it more useful in the education of persons with diabetes; changing the order of the exchange lists to emphasize a high-carbohydrate, high-fiber diet, as well as to better reflect the order of foods in menu planning; adding symbols to foods high in fiber and sodium; changing nutritive values for the starch/bread and fruit lists; adding lists of combination foods, free foods, and foods recommended only for occasional use; developing a data base; and initiating a plan for field testing and evaluation. The committee also developed a simplified meal planning tool, Healthy Food Choices, to be used for initial or "survival" level education. In poster format, foods are grouped by calories into six food groups. Approximate portion sizes of commonly used foods are listed. Blank lines are provided for the nutrition counselor to write in a suggested menu or meal plan for the client. Because the booklet does not use the word "diabetes" specifically, it is appropriate as a general teaching tool. PMID:3794130

  19. Heat exchanger-accumulator

    DOEpatents

    Ecker, Amir L.

    1980-01-01

    What is disclosed is a heat exchanger-accumulator for vaporizing a refrigerant or the like, characterized by an upright pressure vessel having a top, bottom and side walls; an inlet conduit eccentrically and sealingly penetrating through the top; a tubular overflow chamber disposed within the vessel and sealingly connected with the bottom so as to define an annular outer volumetric chamber for receiving refrigerant; a heat transfer coil disposed in the outer volumetric chamber for vaporizing the liquid refrigerant that accumulates there; the heat transfer coil defining a passageway for circulating an externally supplied heat exchange fluid; transferring heat efficiently from the fluid; and freely allowing vaporized refrigerant to escape upwardly from the liquid refrigerant; and a refrigerant discharge conduit penetrating sealingly through the top and traversing substantially the length of the pressurized vessel downwardly and upwardly such that its inlet is near the top of the pressurized vessel so as to provide a means for transporting refrigerant vapor from the vessel. The refrigerant discharge conduit has metering orifices, or passageways, penetrating laterally through its walls near the bottom, communicating respectively interiorly and exteriorly of the overflow chamber for controllably carrying small amounts of liquid refrigerant and oil to the effluent stream of refrigerant gas.

  20. System for exchanging tools and end effectors on a robot

    DOEpatents

    Burry, D.B.; Williams, P.M.

    1991-02-19

    A system and method for exchanging tools and end effectors on a robot permits exchange during a programmed task. The exchange mechanism is located off the robot, thus reducing the mass of the robot arm and permitting smaller robots to perform designated tasks. A simple spring/collet mechanism mounted on the robot is used which permits the engagement and disengagement of the tool or end effector without the need for a rotational orientation of the tool to the end effector/collet interface. As the tool changing system is not located on the robot arm no umbilical cords are located on robot. 12 figures.

  1. System for exchanging tools and end effectors on a robot

    DOEpatents

    Burry, David B.; Williams, Paul M.

    1991-02-19

    A system and method for exchanging tools and end effectors on a robot permits exchange during a programmed task. The exchange mechanism is located off the robot, thus reducing the mass of the robot arm and permitting smaller robots to perform designated tasks. A simple spring/collet mechanism mounted on the robot is used which permits the engagement and disengagement of the tool or end effector without the need for a rotational orientation of the tool to the end effector/collet interface. As the tool changing system is not located on the robot arm no umbilical cords are located on robot.

  2. Exchange and relaxation effects in low-energy radiationless transitions

    NASA Technical Reports Server (NTRS)

    Chen, M. H.; Crasemann, B.; Aoyagi, M.; Mark, H.

    1978-01-01

    The effect on low-energy atomic inner-shell Coster-Kronig and super Coster-Kronig transitions that is produced by relaxation and by exchange between the continuum electron and bound electrons was examined and illustrated by specific calculations for transitions that deexcite the 3p vacancy state of Zn. Taking exchange and relaxation into account is found to reduce, but not to eliminate, the discrepancies between theoretical rates and measurements.

  3. Ion exchange technology assessment report

    SciTech Connect

    Duhn, E.F.

    1992-01-01

    In the execution of its charter, the SRS Ion Exchange Technology Assessment Team has determined that ion exchange (IX) technology has evolved to the point where it should now be considered as a viable alternative to the SRS reference ITP/LW/PH process. The ion exchange media available today offer the ability to design ion exchange processing systems tailored to the unique physical and chemical properties of SRS soluble HLW's. The technical assessment of IX technology and its applicability to the processing of SRS soluble HLW has demonstrated that IX is unquestionably a viable technology. A task team was chartered to evaluate the technology of ion exchange and its potential for replacing the present In-Tank Precipitation and proposed Late Wash processes to remove Cs, Sr, and Pu from soluble salt solutions at the Savannah River Site. This report documents the ion exchange technology assessment and conclusions of the task team.

  4. Ion exchange technology assessment report

    SciTech Connect

    Duhn, E.F.

    1992-12-31

    In the execution of its charter, the SRS Ion Exchange Technology Assessment Team has determined that ion exchange (IX) technology has evolved to the point where it should now be considered as a viable alternative to the SRS reference ITP/LW/PH process. The ion exchange media available today offer the ability to design ion exchange processing systems tailored to the unique physical and chemical properties of SRS soluble HLW`s. The technical assessment of IX technology and its applicability to the processing of SRS soluble HLW has demonstrated that IX is unquestionably a viable technology. A task team was chartered to evaluate the technology of ion exchange and its potential for replacing the present In-Tank Precipitation and proposed Late Wash processes to remove Cs, Sr, and Pu from soluble salt solutions at the Savannah River Site. This report documents the ion exchange technology assessment and conclusions of the task team.

  5. MODELING RESULTS FROM CESIUM ION EXCHANGE PROCESSING WITH SPHERICAL RESINS

    SciTech Connect

    Nash, C.; Hang, T.; Aleman, S.

    2011-01-03

    Ion exchange modeling was conducted at the Savannah River National Laboratory to compare the performance of two organic resins in support of Small Column Ion Exchange (SCIX). In-tank ion exchange (IX) columns are being considered for cesium removal at Hanford and the Savannah River Site (SRS). The spherical forms of resorcinol formaldehyde ion exchange resin (sRF) as well as a hypothetical spherical SuperLig{reg_sign} 644 (SL644) are evaluated for decontamination of dissolved saltcake wastes (supernates). Both SuperLig{reg_sign} and resorcinol formaldehyde resin beds can exhibit hydraulic problems in their granular (nonspherical) forms. SRS waste is generally lower in potassium and organic components than Hanford waste. Using VERSE-LC Version 7.8 along with the cesium Freundlich/Langmuir isotherms to simulate the waste decontamination in ion exchange columns, spherical SL644 was found to reduce column cycling by 50% for high-potassium supernates, but sRF performed equally well for the lowest-potassium feeds. Reduced cycling results in reduction of nitric acid (resin elution) and sodium addition (resin regeneration), therefore, significantly reducing life-cycle operational costs. These findings motivate the development of a spherical form of SL644. This work demonstrates the versatility of the ion exchange modeling to study the effects of resin characteristics on processing cycles, rates, and cold chemical consumption. The value of a resin with increased selectivity for cesium over potassium can be assessed for further development.

  6. Biological Ion Exchanger Resins

    PubMed Central

    Damadian, Raymond; Goldsmith, Michael; Zaner, K. S.

    1971-01-01

    Biological selectivity is shown to vary with medium osmotic strength and temperature. Selectivity reversals occur at 4°C and at an external osmolality of 0.800 indicating that intracellular hydration and endosolvent (intracellular water) structure are important determinants in selectivity. Magnetic resonance measurements of line width by steady-state nuclear magnetic resonance (NMR) indicate a difference in the intracellular water signal of 16 Hz between the K form and Na form of Escherichia coli, providing additional evidence that changes in the ionic composition of cells are accompanied by changes in endosolvent structure. The changes were found to be consistent with the thermodynamic and magnetic resonance properties of aqueous electrolyte solutions. Calculation of the dependence of ion-pairing forces on medium dielectric reinforces the role of endosolvent structure in determining ion exchange selectivity. PMID:4943653

  7. Cross-Shelf Exchange.

    PubMed

    Brink, K H

    2016-01-01

    Cross-shelf exchange dominates the pathways and rates by which nutrients, biota, and materials on the continental shelf are delivered and removed. This follows because cross-shelf gradients of most properties are usually far greater than those in the alongshore direction. The resulting transports are limited by Earth's rotation, which inhibits flow from crossing isobaths. Thus, cross-shelf flows are generally weak compared with alongshore flows, and this leads to interesting observational issues. Cross-shelf flows are enabled by turbulent mixing processes, nonlinear processes (such as momentum advection), and time dependence. Thus, there is a wide range of possible effects that can allow these critical transports, and different natural settings are often governed by different combinations of processes. This review discusses examples of representative transport mechanisms and explores possible observational and theoretical paths to future progress. PMID:26747520

  8. Monogroove liquid heat exchanger

    NASA Technical Reports Server (NTRS)

    Brown, Richard F. (Inventor); Edelstein, Fred (Inventor)

    1990-01-01

    A liquid supply control is disclosed for a heat transfer system which transports heat by liquid-vapor phase change of a working fluid. An assembly (10) of monogroove heat pipe legs (15) can be operated automatically as either heat acquisition devices or heat discharge sources. The liquid channels (27) of the heat pipe legs (15) are connected to a reservoir (35) which is filled and drained by respective filling and draining valves (30, 32). Information from liquid level sensors (50, 51) on the reservoir (35) is combined (60) with temperature information (55) from the liquid heat exchanger (12) and temperature information (56) from the assembly vapor conduit (42) to regulate filling and draining of the reservoir (35), so that the reservoir (35) in turn serves the liquid supply/drain needs of the heat pipe legs (15), on demand, by passive capillary action (20, 28).

  9. Hybrid Heat Exchangers

    NASA Technical Reports Server (NTRS)

    Tu, Jianping Gene; Shih, Wei

    2010-01-01

    A hybrid light-weight heat exchanger concept has been developed that uses high-conductivity carbon-carbon (C-C) composites as the heat-transfer fins and uses conventional high-temperature metals, such as Inconel, nickel, and titanium as the parting sheets to meet leakage and structural requirements. In order to maximize thermal conductivity, the majority of carbon fiber is aligned in the fin direction resulting in 300 W/m.K or higher conductivity in the fin directions. As a result of this fiber orientation, the coefficient of thermal expansion (CTE) of the C-C composite in both non-fiber directions matches well with the CTE of various high-temperature metal alloys. This allows the joining of fins and parting sheets by using high-temperature braze alloys.

  10. South Atlantic interbasin exchange

    NASA Technical Reports Server (NTRS)

    Rintoul, Stephen Rich

    1991-01-01

    The exchange of mass and heat between the South Atlantic and the neighboring ocean basins was estimated using hydrographic data and inverse methods, in order to gain information on the links between the deep-water formation processes occurring within the Atlantic and the global thermohaline circulation. Results demonstrate that the global thermohaline cell associated with the formation and export of North Atlantic deep water (NADW) is closed primarily by a 'cold water path' in which deep water leaving the Atlantic ultimately returns as intermediate water entering the basin through Drake Passage. This conclusion conflicts with the suggestion by Gordon (1986) that the global thermohaline circulation associated with the formation of NADW is closed primarily by a 'warm water path', in which the export of NADW is compensated by an inflow of warm Indian Ocean thermocline water south of Africa.

  11. Heat exchanger bypass test report

    SciTech Connect

    De Vries, M.L.

    1995-01-26

    This test report documents the results that were obtained while conducting the test procedure which bypassed the heat exchangers in the HC-21C sludge stabilization process. The test was performed on November 15, 1994 using WHC-SD-CP-TC-031, ``Heat Exchanger Bypass Test Procedure.`` The primary objective of the test procedure was to determine if the heat exchangers were contributing to condensation of moisture in the off-gas line. This condensation was observed in the rotameters. Also, a secondary objective was to determine if temperatures at the rotameters would be too high and damage them or make them inaccurate without the heat exchangers in place.

  12. Ion-exchange hollow fibers

    NASA Technical Reports Server (NTRS)

    Rembaum, A.; Yen, S. P. S.; Klein, E. (Inventor)

    1976-01-01

    An ion-exchange hollow fiber is prepared by introducing into the wall of the fiber polymerizable liquid monomers, and polymerizing the monomers therein to form solid, insoluble, crosslinked, ion-exchange resin particles which embed in the wall of the fiber. Excess particles blocking the central passage or bore of the fiber are removed by forcing liquid through the fiber. The fibers have high ion-exchange capacity, a practical wall permeability and good mechanical strength even with very thin wall dimensions. Experimental investigation of bundles of ion-exchange hollow fibers attached to a header assembly have shown the fiber to be very efficient in removing counterions from solution.

  13. Ion-exchange hollow fibers

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Shiao-Ping S. (Inventor); Klein, Elias (Inventor)

    1980-01-01

    An ion-exchange hollow fiber is prepared by introducing into the wall of the fiber polymerizable liquid monomers, and polymerizing the monomers therein to form solid, insoluble, cross-linked, ion-exchange resin particles which embed in the wall of the fiber. Excess particles blocking the central passage or bore of the fiber are removed by forcing liquid through the fiber. The fibers have high ion-exchange capacity, a practical wall permeability and good mechanical strength even with very thin wall dimensions. Experimental investigation of bundles of ion-exchange hollow fibers attached to a header assembly have shown the fiber to be very efficient in removing counterions from solution.

  14. Ion-exchange hollow fibers

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Shiao-Ping S. (Inventor); Klein, Elias (Inventor)

    1977-01-01

    An ion-exchange hollow fiber is prepared by introducing into the wall of the fiber polymerizable liquid monomers, and polymerizing the monomers therein to form solid, insoluble, cross-linked, ion-exchange resin particles which embed in the wall of the fiber. Excess particles blocking the central passage or bore of the fiber are removed by forcing liquid through the fiber. The fibers have high ion-exchange capacity, a practical wall permeability and good mechanical strength even with very thin wall dimensions. Experimental investigation of bundles of ion-exchange hollow fibers attached to a header assembly have shown the fiber to be very efficient in removing counterions from solution.

  15. Asphaltene precipitation primary crude exchanger fouling mechanism

    SciTech Connect

    Dickakian, G.; Seay, S.

    1988-03-07

    Research at Exxon Chemical Co. has shown that asphaltene precipitation and subsequent carbonization is the major mechanism in crude oil heat exchanger fouling. Exchangers that foul frequently must be cleaned on a regular basis. In the worst case, furnace-limited refiners may have to cut crude-charging rates as preheat fouling reduces coil inlet temperatures. To improve operation and control these costs, many refiners invest significant amounts of money in antifoulant programs. A new way to characterize crude oil fouling tendencies, Exxon's AFC fouling index has been developed. Two examples of how refiners can improve the cost effectiveness and performance of their antifoulant programs by using the index are presented in this article, along with the general methods used to control fouling.

  16. [Pathophysiology of gas exchange in ARDS].

    PubMed

    Fernández Fernández, R

    2006-11-01

    ARDS is produced in a pulmonary edema picture due to increased vascular patency. In this way, the initial alteration consists in an alveolar occupation due to protein rich edema. This occupation reduces the alveolar surface available for gas exchange, increasing the pulmonary areas with poor or null V/Q ratio. As ARDS progresses, vascular phenomena occur that affect the gas exchange differently, giving rise to heterogeneity in the V/Q ratio. This situation worsens due to the appearance of areas with null ventilation in relationship with the appearance of atelectasis in lung dependent zones. All these factors form the hypoxemia picture refractory to the increase of the inspired oxygen fraction characteristic of this clinical entity. In this article, we make a review of these physiological mechanisms and the effect on the oxygenation of different ventilatory and drug maneuvers. PMID:17129535

  17. Intergranular properties of (Y{sub 1{minus}x{minus}y}Zr{sub x}Ca{sub y})Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} compounds

    SciTech Connect

    Deac, I.G.; Burzo, E.; Pop, A.V.; Pop, V.; Tetean, R.; Kovacs, D.; Borodi, G.

    1999-05-30

    the integranular properties of (Y{sub 1{minus}x{minus}y}Zr{sub x}Ca{sub y})Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} ceramics were studies by using temperature-dependent ac susceptibility measurements at zero dc magnetic field. The intergranular critical current density was determined from ac susceptibility data by varying the field amplitude H{sub ac}. From the imaginary part of the complex susceptibility, {chi}{double_prime}(T), the authors have determined the temperature dependence of the critical current density by using the Bean`s model. The ac field dependencies of the intergrain {chi}{double_prime}-peak temperatures T{sub p} are linear and agree with Mueller critical state model. The results were analyzed in terms of superconductor-insulator-superconductor (SIS)-and superconductor-normal-superconductor (SNS)-type models for granular superconductors.

  18. Part 2. Metallurgical factors governing the H-assisted intergranular cracking of peak-aged Ti-3Al-8V-6Cr-4Mo-4Zr (Beta-C)

    SciTech Connect

    Gaudett, M.A.; Scully, J.R.

    2000-01-01

    A previous study (Part 1) showed that the solution-treated and aged (STA) (i.e., peak-aged) condition of Beta-C Ti, ({sigma}{sub 0.2 pct y} = 865 MPa), as measured by reductions in the fracture initiation stress with predissolved H content and the introduction of an intergranular (IG) fracture mode. It was also shown that yield-strength elevation and the subsequent enhancement in the local hydrostatic stresses within the notch root are not the controlling factors in the H-assisted IG fracture initiation of the STA condition. Previous work (Part 1) implicates a microstructural feature or condition associated with the 500 C aging treating. In this study, it is shown that localized internal hydride precipitation at the grain boundaries or alpha beta interfaces was not detected by a variety of experimental methods over the range of internal H contents for which IG fracture initiation was observed. It was also shown that grain-boundary alpha colonies or films are not responsible for the IG fracture initiation in the STA condition. A measured increase in hydrogen embrittlement (HG) susceptibility as a function of aging time at 500 C is consistent with the segregation or depletion of a critical species at the grain boundary. However, grain-boundary segregation/depletion could not be detected with Auger electron spectroscopy (AES) of specimens fracturing in a vacuum. Compression tests used to characterize and compare the alloys' slip behavior showed that plastic deformation is concentrated at or near the grain boundaries in the STA condition. Therefore, a possible intergranular fracture initiation mechanism that includes the effects of hydrogen and localized deformation is discussed.

  19. Syringe exchange programs --- United States, 2008.

    PubMed

    2010-11-19

    Persons who inject drugs should use a new, sterile needle and syringe for each injection. Syringe exchange programs (SEPs) provide free sterile syringes and collect used syringes from injection-drug users (IDUs) to reduce transmission of bloodborne pathogens, including human immunodeficiency virus (HIV), hepatitis B virus, and hepatitis C virus (HCV). As of March 2009, a total of 184 SEPs were known to be operating in 36 states, the District of Columbia (DC), and Puerto Rico (North American Syringe Exchange Network [NASEN], unpublished data, 2009). Of these, 123 (67%) SEP directors participated in a mail/telephone survey conducted by NASEN and Beth Israel Medical Center (New York, New York) that covered program operations for the calendar year 2008. To characterize SEPs in the United States, this report summarizes the findings from that survey and compares them with previous SEP survey results from the period 1994-2007. In 2008, the 123 SEPs reported exchanging 29.1 million syringes and had budgets totaling $21.3 million, of which 79% came from state and local governments. Most of the SEPs reported offering preventive health and clinical services in addition to basic syringe exchange: 87% offered HIV counseling and testing, 65% offered hepatitis C counseling and testing, 55% offered sexually transmitted disease screening, and 31% offered tuberculosis screening; 89% provided referrals to substance abuse treatment. Providing comprehensive prevention services and referrals to IDUs, such as those offered by many SEPs, can help reduce the spread of bloodborne infections and should increase access to health care and substance abuse treatment, thus serving as an effective public health approach for this population. PMID:21085091

  20. Heat recovery reduces process energy losses

    SciTech Connect

    Anon

    1981-09-01

    After evaluation of process and plant operation losses, a pharmaceutical plant found heat recovery a viable means of reducing energy losses. One of the first applications of air-to-air heat recovery was in a recirculation/dehumidification process. Heat exchangers were used to recover heat from the air used to generate or dry the dehumidification material.

  1. StarBright Learning Exchange

    ERIC Educational Resources Information Center

    Kalinowski, Michael

    2007-01-01

    This article features StarBright Learning Exchange, a program that provides a cross-cultural exchange between Australian and South African early childhood educators. The program was originated when its president, Carol Allen, and her colleague, Karen Williams, decided that they could no longer sit by and watch the unfolding social catastrophe that…

  2. Educators Exchange: A Program Evaluation.

    ERIC Educational Resources Information Center

    Armstrong, William B.

    The Educators Exchange Program (EEP) was established under a training and educational exchange agreement reached by California's San Diego Community College District (SDCCD) and the republic of Mexico. In the program, the District provided a 4-week technological training program to faculty at Centros de Capacitacion Tecnologica Industrial…

  3. Technology Performance Exchange (Fact Sheet)

    SciTech Connect

    Not Available

    2012-10-01

    This fact sheet, 'The Technology Performance Exchange' will be presented at the ET Summit, held at the Pasadena Convention Center on October 15-17, 2012. The Technology Performance Exchange will be a centralized, Web-based portal for finding and sharing energy performance data for commercial building technologies.

  4. Exchange Rates and Old People.

    ERIC Educational Resources Information Center

    Dowd, James J.

    1980-01-01

    Extends earlier work on aging as a process of exchange by focusing on the issue of exchange rates and how they are negotiated. Access to power resources declines with age, placing the old person in the position of negotiating from weakness. (Author)

  5. Organ donation as gift exchange.

    PubMed

    Vernale, C; Packard, S A

    1990-01-01

    Organ donation, considered by sociologists as a type of gift exchange, involves moral, social, psychological, religious and legal issues. This gift exchange paradigm can be used as a framework to understand donor and recipient issues, cadaveric organ donation and the importance of the role of nurses during organ procurement. PMID:2292445

  6. Professional Exchange: Mapping the Future.

    ERIC Educational Resources Information Center

    Dingman, Robert L.

    1993-01-01

    New associate editor of Professional Exchange section of "Journal of Mental Health Counseling" discusses importance of section. Lists potential topics suggested in 1989, then adds several other topics to the list. Concludes with guidelines for submission to Professional Exchange section. (NB)

  7. EXCHANGE. Volume 9-92

    SciTech Connect

    Boltz, J.C.

    1992-09-01

    EXCHANGE is published monthly by the Idaho National Engineering Laboratory (INEL), a multidisciplinary facility operated for the US Department of Energy (DOE). The purpose of EXCHANGE is to inform computer users about about recent changes and innovations in both the mainframe and personal computer environments and how these changes can affect work being performed at DOE facilities.

  8. NGNP Process Heat Utilization: Liquid Metal Phase Change Heat Exchanger

    SciTech Connect

    Piyush Sabharwall; Mike Patterson; Vivek Utgikar; Fred Gunnerson

    2008-09-01

    One key long-standing issue that must be overcome to fully realize the successful growth of nuclear power is to determine other benefits of nuclear energy apart from meeting the electricity demands. The Next Generation Nuclear Plant (NGNP) will most likely be producing electricity and heat for the production of hydrogen and/or oil retrieval from oil sands and oil shale to help in our national pursuit of energy independence. For nuclear process heat to be utilized, intermediate heat exchange is required to transfer heat from the NGNP to the hydrogen plant or oil recovery field in the most efficient way possible. Development of nuclear reactor - process heat technology has intensified the interest in liquid metals as heat transfer media because of their ideal transport properties. Liquid metal heat exchangers are not new in practical applications. An important rational for considering liquid metals is the potential convective heat transfer is among the highest known. Thus explains the interest in liquid metals as coolant for intermediate heat exchange from NGNP. For process heat it is desired that, intermediate heat exchangers (IHX) transfer heat from the NGNP in the most efficient way possible. The production of electric power at higher efficiency via the Brayton Cycle, and hydrogen production, requires both heat at higher temperatures and high effectiveness compact heat exchangers to transfer heat to either the power or process cycle. Compact heat exchangers maximize the heat transfer surface area per volume of heat exchanger; this has the benefit of reducing heat exchanger size and heat losses. High temperature IHX design requirements are governed in part by the allowable temperature drop between the outlet and inlet of the NGNP. In order to improve the characteristics of heat transfer, liquid metal phase change heat exchangers may be more effective and efficient. This paper explores the overall heat transfer characteristics and pressure drop of the phase change

  9. High Temperature Heat Exchanger Project

    SciTech Connect

    Anthony E. Hechanova, Ph.D.

    2008-09-30

    The UNLV Research Foundation assembled a research consortium for high temperature heat exchanger design and materials compatibility and performance comprised of university and private industry partners under the auspices of the US DOE-NE Nuclear Hydrogen Initiative in October 2003. The objectives of the consortium were to conduct investigations of candidate materials for high temperature heat exchanger componets in hydrogen production processes and design and perform prototypical testing of heat exchangers. The initial research of the consortium focused on the intermediate heat exchanger (located between the nuclear reactor and hydrogen production plan) and the components for the hydrogen iodine decomposition process and sulfuric acid decomposition process. These heat exchanger components were deemed the most challenging from a materials performance and compatibility perspective

  10. Fault-Tolerant Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Izenson, Michael G.; Crowley, Christopher J.

    2005-01-01

    A compact, lightweight heat exchanger has been designed to be fault-tolerant in the sense that a single-point leak would not cause mixing of heat-transfer fluids. This particular heat exchanger is intended to be part of the temperature-regulation system for habitable modules of the International Space Station and to function with water and ammonia as the heat-transfer fluids. The basic fault-tolerant design is adaptable to other heat-transfer fluids and heat exchangers for applications in which mixing of heat-transfer fluids would pose toxic, explosive, or other hazards: Examples could include fuel/air heat exchangers for thermal management on aircraft, process heat exchangers in the cryogenic industry, and heat exchangers used in chemical processing. The reason this heat exchanger can tolerate a single-point leak is that the heat-transfer fluids are everywhere separated by a vented volume and at least two seals. The combination of fault tolerance, compactness, and light weight is implemented in a unique heat-exchanger core configuration: Each fluid passage is entirely surrounded by a vented region bridged by solid structures through which heat is conducted between the fluids. Precise, proprietary fabrication techniques make it possible to manufacture the vented regions and heat-conducting structures with very small dimensions to obtain a very large coefficient of heat transfer between the two fluids. A large heat-transfer coefficient favors compact design by making it possible to use a relatively small core for a given heat-transfer rate. Calculations and experiments have shown that in most respects, the fault-tolerant heat exchanger can be expected to equal or exceed the performance of the non-fault-tolerant heat exchanger that it is intended to supplant (see table). The only significant disadvantages are a slight weight penalty and a small decrease in the mass-specific heat transfer.

  11. Modular heat exchanger

    DOEpatents

    Giardina, A.R.

    1981-03-03

    A shell and tube heat exchanger is described having a plurality of individually removable tube bundle modules. A lattice of structural steel forming rectangular openings therein is placed at each end of a cylindrical shell. Longitudinal structural members are placed in the shell between corners of the rectangular openings situated on opposite ends of the shell. Intermediate support members interconnect the longitudinal supports so as to increase the longitudinal supports rigidity. Rectangular parallelepiped tube bundle modules occupy the space defined by the longitudinal supports and end supports and each include a rectangular tube sheet situated on each end of a plurality of tubes extending there through, a plurality of rectangular tube supports located between the tube sheets, and a tube bundle module stiffening structure disposed about the bundle's periphery and being attached to the tube sheets and tube supports. The corners of each tube bundle module have longitudinal framework members which are mateable with and supported by the longitudinal support members. Intermediate support members constitute several lattices, each of which is situated in a plane between the end support members. The intermediate support members constituting the several lattices extend horizontally and vertically between longitudinal supports of adjacent tube module voids. An alternative embodiment for intermediate support members constitute a series of structural plates situated at the corners of the module voids and having recesses therein for receiving the respective longitudinal support members adjacent thereto, protrusions separating the recesses, and a plurality of struts situated between protrusions of adjacent structural plates. 12 figs.

  12. Modular heat exchanger

    DOEpatents

    Giardina, Angelo R. [Marple Township, Delaware County, PA

    1981-03-03

    A shell and tube heat exchanger having a plurality of individually removable tube bundle modules. A lattice of structural steel forming rectangular openings therein is placed at each end of a cylindrical shell. Longitudinal structural members are placed in the shell between corners of the rectangular openings situated on opposite ends of the shell. Intermediate support members interconnect the longitudinal supports so as to increase the longitudinal supports rigidity. Rectangular parallelpiped tube bundle moldules occupy the space defined by the longitudinal supports and end supports and each include a rectangular tube sheet situated on each end of a plurality of tubes extending therethrough, a plurality of rectangular tube supports located between the tube sheets, and a tube bundle module stiffening structure disposed about the bundle's periphery and being attached to the tube sheets and tube supports. The corners of each tube bundle module have longitudinal framework members which are mateable with and supported by the longitudinal support members. Intermediate support members constitute several lattice, each of which is situate d in a plane between the end support members. The intermediate support members constituting the several lattice extend horizontally and vertically between longitudinal supports of adjacent tube module voids. An alternative embodiment for intermediate support members constitute a series of structural plates situated at the corners of the module voids and having recesses therein for receiving the respective longitudinal support members adjacent thereto, protrusions separating the recesses, and a plurality of struts situated between protrusions of adjacent structural plates.

  13. Energy-Exchange Project

    SciTech Connect

    Not Available

    1982-04-01

    The purpose of the study was to determine what energy savings can be achieved by coordinating the resources and requirements of two facilities, the 26th Ward Water Pollution Control Plant (WPCP) and a housing development named Starrett City with its own total energy system. It was determined that three energy exchange options were economically and technically feasible. These include: the transfer of digester gas produced at the 26th Ward to the boilers at the Starrett City's total energy plant (TEP); the transfer of hot water heated at the TEP to the 26th Ward for space and process heating; and the transfer of coal effluent waste water from the 26th Ward to the condenser cooling systems at the TEP. Technical information is presented to support the findings. The report addresses those tasks of the statement of work dedicated to data acquisition, analysis, and energy conservation strategies internal to the Starrett City TEP and the community it supplies as well as to the 26th Ward WPCP. (MCW)

  14. Insurance Exchange Marketplace: Implications for Emergency Medicine Practice

    PubMed Central

    Rankey, David S.

    2012-01-01

    The Patient Protection and Affordable Care Act of 2010 requires states to establish healthcare insurance exchanges by 2014 to facilitate the purchase of qualified health plans. States are required to establish exchanges for small businesses and individuals. A federally operated exchange will be established, and states failing to participate in any other exchanges will be mandated to join the federal exchange. Policymakers and health economists believe that exchanges will improve healthcare at lower cost by promoting competition among insurers and by reducing burdensome transaction costs. Consumers will no longer be isolated from monthly insurance premium costs. Exchanges will increase the number of patients insured with more cost-conscious managed care and high-deductible plans. These insurance plan models have historically undervalued emergency medical services, while also underinsuring patients and limiting their healthcare system access to the emergency department. This paradoxically increases demand for emergency services while decreasing supply. The continual devaluation of emergency medical services by insurance payers will result in inadequate distribution of resources to emergency care, resulting in further emergency department closures, increases in emergency department crowding, and the demise of acute care services provided to families and communities. PMID:22900107

  15. Novel exchange-coupled SmFe3/α-Fe nanocomposite magnets fabricated by magnetic annealing

    NASA Astrophysics Data System (ADS)

    Li, Liya; Yan, A.-ru; Peng, Hua-xin; Luo, Yang; Yi, Jianhong; Peng, Yuandong

    2015-02-01

    A new nanocomposite magnet containing exchange-coupled SmFe3 and α-Fe phases has been successfully fabricated via melt spinning followed by magnetic annealing at 450-470 °C for 10 min. These SmFe3/α-Fe magnets show remarkably high remanent ratio, Mr/Ms, up to 0.93 and display a smooth single-phase-like loop with excellent rectangularity. In comparison, the non-field treated ones exhibit much lower Mr/Ms values and show a distinctive kink in the demagnetization curve due to the decoupling of the nanograins. The Henkel plot and microstructural examination confirm that magnetic annealing leads to much stronger intergranular exchange coupling, which is attributed to the formation of a magnetic-field-induced microstructure consisting of the SmFe3 hard phase with diameters of 80-100 nm and the α-Fe soft phase with size of about 3-8 nm. An enhanced energy product of 13.0 MGOe has been obtained in the ribbon magnetically annealed at 470 °C, which is about 60% higher than that of the ribbon annealed without a magnetic field.

  16. 76 FR 28358 - Retail Foreign Exchange Transactions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-17

    ... Off-Exchange Retail Foreign Exchange Transactions and Intermediaries, 75 FR 55409 (Sept. 10, 2010... Act. Regulation of Off-Exchange Retail Foreign Exchange Transactions and Intermediaries, 75 FR 3281 (Jan. 20, 2010) (Proposed CFTC Retail Forex Rule). \\13\\ See Retail Foreign Exchange Transactions, 76...

  17. Various methods to improve heat transfer in exchangers

    NASA Astrophysics Data System (ADS)

    Pavel, Zitek; Vaclav, Valenta

    2015-05-01

    The University of West Bohemia in Pilsen (Department of Power System Engineering) is working on the selection of effective heat exchangers. Conventional shell and tube heat exchangers use simple segmental baffles. It can be replaced by helical baffles, which increase the heat transfer efficiency and reduce pressure losses. Their usage is demonstrated in the primary circuit of IV. generation MSR (Molten Salt Reactors). For high-temperature reactors we consider the use of compact desk heat exchangers, which are small, which allows the integral configuration of reactor. We design them from graphite composites, which allow up to 1000°C and are usable as exchangers: salt-salt or salt-acid (e.g. for the hydrogen production). In the paper there are shown thermo-physical properties of salts, material properties and principles of calculations.

  18. Enhancement of heat transfer in waste-heat heat exchangers

    NASA Astrophysics Data System (ADS)

    Stoeffler, R. C.

    1980-07-01

    The Fluidfire shallow fluidized bed heat transfer facility was modified to give increased air flow capacity and to allow testing with different distributor plates and with two stage heat exchangers. The effect of reduced distributor plate pressure loss and amount and type of bed material on the heat transfer performance of a single stage fluidized bed heat exchanger is explored. Elutriation from the bed was measured for different bed materials and distributor plates; alternate heat exchanger surfaces having different fin spacings were also tested. Two types of two stage fluidized bed heat exchangers were tested: one having a baffle (having almost no pressure loss) located between the stages and which allowed bed material to recirculate between upper and lower beds; the second having two distributor plates in series with no recirculation of the bed material.

  19. Ion Exchange Temperature Testing with SRF Resin

    SciTech Connect

    Russell, Renee L.; Rinehart, Donald E.; Brown, Garrett N.; Peterson, Reid A.

    2012-03-01

    Ion exchange using the Spherical Resorcinol-Formaldehyde (SRF) resin has been selected by the U.S. Department of Energy’s Office of River Protection for use in the Pretreatment Facility of the Hanford Tank Waste Treatment and Immobilization Plant (WTP) and for potential application in an at-tank deployment for removing 137Cs. Recent proposed changes to the WTP ion exchange process baseline indicate that higher temperatures (50°C) to alleviate post-filtration precipitation issues prior to reaching the ion exchange columns may be required. Therefore, it is important to understand the behavior of SRF resin performance under the conditions expected with the new equipment and process changes. This research examined the impact of elevated temperature on resin loading and resin degradation during extended solution flow using elevated temperature (45°, 50°, 55°, 60°, 65°, 75°C). Testing for extended times at elevated temperatures showed that the resin does degrade and loading capacity is reduced at and above 45°C. Above 60°C the resin appears to not load at all.

  20. Heat exchange assembly

    DOEpatents

    Lowenstein, Andrew; Sibilia, Marc; Miller, Jeffrey; Tonon, Thomas S.

    2004-06-08

    A heat exchange assembly comprises a plurality of plates disposed in a spaced-apart arrangement, each of the plurality of plates includes a plurality of passages extending internally from a first end to a second end for directing flow of a heat transfer fluid in a first plane, a plurality of first end-piece members equaling the number of plates and a plurality of second end-piece members also equaling the number of plates, each of the first and second end-piece members including a recessed region adapted to fluidly connect and couple with the first and second ends of the plate, respectively, and further adapted to be affixed to respective adjacent first and second end-piece members in a stacked formation, and each of the first and second end-piece members further including at least one cavity for enabling entry of the heat transfer fluid into the plate, exit of the heat transfer fluid from the plate, or 180.degree. turning of the fluid within the plate to create a serpentine-like fluid flow path between points of entry and exit of the fluid, and at least two fluid conduits extending through the stacked plurality of first and second end-piece members for providing first fluid connections between the parallel fluid entry points of adjacent plates and a fluid supply inlet, and second fluid connections between the parallel fluid exit points of adjacent plates and a fluid discharge outlet so that the heat transfer fluid travels in parallel paths through each respective plate.

  1. Hear Exchange Assembly

    DOEpatents

    Lowenstein, Andrew; Sibilia, Marc; Miller, Jeffrey; Tonon, Thomas S.

    2003-05-27

    A heat exchange assembly comprises a plurality of plates disposed in a spaced-apart arrangement, each of the plurality of plates includes a plurality of passages extending internally from a first end to a second end for directing flow of a heat transfer fluid in a first plane, a plurality of first end-piece members equaling the number of plates and a plurality of second end-piece members also equaling the number of plates, each of the first and second end-piece members including a recessed region adapted to fluidly connect and couple with the first and second ends of the plate, respectively, and further adapted to be affixed to respective adjacent first and second end-piece members in a stacked formation, and each of the first and second end-piece members further including at least one cavity for enabling entry of the heat transfer fluid into the plate, exit of the heat transfer fluid from the plate, or 180.degree. turning of the fluid within the plate to create a serpentine-like fluid flow path between points of entry and exit of the fluid, and at least two fluid conduits extending through the stacked plurality of first and second end-piece members for providing first fluid connections between the parallel fluid entry points of adjacent plates and a fluid supply inlet, and second fluid connections between the parallel fluid exit points of adjacent plates and a fluid discharge outlet so that the heat transfer fluid travels in parallel paths through each respective plate.

  2. Effect of polyamine reagents on exchange capacity in ion exchangers

    NASA Astrophysics Data System (ADS)

    Petrova, T. I.; Dyachenko, F. V.; Bogatyreva, Yu. V.; Borodastov, A. K.; Ershova, I. S.

    2016-05-01

    Effect of compounds involved in complex reagents is described using Helamin 906H reagent as an example. The working exchange capacity of KU-2-8chs cation exchanger in hydrogen form and Amberlite IRA 900Cl anion exchanger in OH form remained almost unchanged when they were used repeatedly to purify water that contained Helamin 906H reagent; in addition, this capacity was the same upon filtration of water that did not contain this reagent. Leakage of total organic carbon was observed earlier than that of calcium ions upon filtration of the solution through the cation exchanger layer. The test results obtained in industrial conditions indicated that using H-OH filters to purify turbine condensate enables the decrease of the concentration of organic and other impurities therein.

  3. Plasma exchange in endocrine ophthalmopathy.

    PubMed

    Berlin, G; Hjelm, H; Liedén, G; Tegler, L

    1990-01-01

    We studied the effects of intensive plasma exchange on endocrine ophthalmopathy in 12 patients with Graves' disease and one with Hashimoto's thyroiditis. All patients were euthyroid at the time of plasma exchange. All but five had concomitant treatment with azathioprine. Each patient had a treatment period consisting of six plasma exchanges performed in 2-3 weeks; two patients were treated in two periods. Each time a mean of 2.4 liters plasma was exchanged. There was a prompt reduction in the concentration of circulating immune complexes and/or thyrotropin receptor antibodies following plasma exchange. Six of the 13 patients improved their proptosis; their median duration of eye symptoms before treatment was less than 8 months. In patients suffering from eye symptoms for more than 1 year improvement was rare. Overall the Hertel values were 24.1 +/- 4.4 (SD) before and 22.8 +/- 3.4 after plasma exchange for the left eyes (P = 0.07) and 23.8 +/- 4.0 before and 23.0 +/- 3.8 after for the right eyes (P = 0.09). Nine patients altogether improved their ophthalmopathy index and periorbital oedema. In patients with disabling endocrine ophthalmopathy plasma exchange may sometimes be of value to induce a relief of the ophthalmopathy; when it is used it should be instituted before fibrotic changes occur. We suggest that concomitant immunosuppressive drugs should be given to prevent rebound phenomenon induced by plasma exchange. To establish the role of plasma exchange in the treatment of endocrine ophthalmopathy controlled studies should be performed. PMID:2228998

  4. Custom, contract, and kidney exchange.

    PubMed

    Healy, Kieran; Krawiec, Kimberly D

    2012-01-01

    In this Essay, we examine a case in which the organizational and logistical demands of a novel form of organ exchange (the nonsimultaneous, extended, altruistic donor (NEAD) chain) do not map cleanly onto standard cultural schemas for either market or gift exchange, resulting in sociological ambiguity and legal uncertainty. In some ways, a NEAD chain resembles a form of generalized exchange, an ancient and widespread instance of the norm of reciprocity that can be thought of simply as the obligation to “pay it forward” rather than the obligation to reciprocate directly with the original giver. At the same time, a NEAD chain resembles a string of promises and commitments to deliver something in exchange for some valuable consideration--that is, a series of contracts. Neither of these salient "social imaginaries" of exchange--gift giving or formal contract--perfectly meets the practical demands of the NEAD system. As a result, neither contract nor generalized exchange drives the practice of NEAD chains. Rather, the majority of actual exchanges still resemble a simpler form of exchange: direct, simultaneous exchange between parties with no time delay or opportunity to back out. If NEAD chains are to reach their full promise for large-scale, nonsimultaneous organ transfer, legal uncertainties and sociological ambiguities must be finessed, both in the practices of the coordinating agencies and in the minds of NEAD-chain participants. This might happen either through the further elaboration of gift-like language and practices, or through a creative use of the cultural form and motivational vocabulary, but not necessarily the legal and institutional machinery, of contract. PMID:23461002

  5. Ceramic heat exchanger

    DOEpatents

    LaHaye, P.G.; Rahman, F.H.; Lebeau, T.P.; Severin, B.K.

    1998-06-16

    A tube containment system is disclosed. The tube containment system does not significantly reduce heat transfer through the tube wall. The contained tube is internally pressurized, and is formed from a ceramic material having high strength, high thermal conductivity, and good thermal shock resistance. The tube containment system includes at least one ceramic fiber braid material disposed about the internally pressurized tube. The material is disposed about the tube in a predetermined axial spacing arrangement. The ceramic fiber braid is present in an amount sufficient to contain the tube if the tube becomes fractured. The tube containment system can also include a plurality of ceramic ring-shaped structures, in contact with the outer surface of the tube, and positioned between the tube and the ceramic fiber braid material, and/or at least one transducer positioned within tube for reducing the internal volume and, therefore, the energy of any shrapnel resulting from a tube fracture. 6 figs.

  6. Ceramic heat exchanger

    DOEpatents

    LaHaye, Paul G.; Rahman, Faress H.; Lebeau, Thomas P. E.; Severin, Barbara K.

    1998-01-01

    A tube containment system. The tube containment system does not significantly reduce heat transfer through the tube wall. The contained tube is internally pressurized, and is formed from a ceramic material having high strength, high thermal conductivity, and good thermal shock resistance. The tube containment system includes at least one ceramic fiber braid material disposed about the internally pressurized tube. The material is disposed about the tube in a predetermined axial spacing arrangement. The ceramic fiber braid is present in an amount sufficient to contain the tube if the tube becomes fractured. The tube containment system can also include a plurality of ceramic ring-shaped structures, in contact with the outer surface of the tube, and positioned between the tube and the ceramic fiber braid material, and/or at least one transducer positioned within tube for reducing the internal volume and, therefore, the energy of any shrapnel resulting from a tube fracture.

  7. Charge exchange molecular ion source

    DOEpatents

    Vella, Michael C.

    2003-06-03

    Ions, particularly molecular ions with multiple dopant nucleons per ion, are produced by charge exchange. An ion source contains a minimum of two regions separated by a physical barrier and utilizes charge exchange to enhance production of a desired ion species. The essential elements are a plasma chamber for production of ions of a first species, a physical separator, and a charge transfer chamber where ions of the first species from the plasma chamber undergo charge exchange or transfer with the reactant atom or molecules to produce ions of a second species. Molecular ions may be produced which are useful for ion implantation.

  8. Heat exchanger with ceramic elements

    DOEpatents

    Corey, John A.

    1986-01-01

    An annular heat exchanger assembly includes a plurality of low thermal growth ceramic heat exchange members with inlet and exit flow ports on distinct faces. A mounting member locates each ceramic member in a near-annular array and seals the flow ports on the distinct faces into the separate flow paths of the heat exchanger. The mounting member adjusts for the temperature gradient in the assembly and the different coefficients of thermal expansion of the members of the assembly during all operating temperatures.

  9. Heat exchanger for electrothermal devices

    NASA Technical Reports Server (NTRS)

    Zavesky, Ralph J. (Inventor); Sovey, James S. (Inventor); Mirtich, Michael J. (Inventor); Marinos, Charalampus (Inventor); Penko, Paul F. (Inventor)

    1986-01-01

    An improved electrothermal device is disclosed. An electrothermal thruster utilizes a generally cylindrical heat exchanger chamber to convert electricity to heat which raises the propellant temperature. A textured, high emissivity heat element radiatively transfers heat to the inner wall of this chamber that is ion beam morphologically controlled for high absorptivity. This, in turn, raises the temperature of a porous heat exchanger material in an annular chamber surrounding the cylindrical chamber. Propellant gas flows through the annular chamber and is heated by the heat exchanger material.

  10. Corrosion protected reversing heat exchanger

    SciTech Connect

    Zawierucha, R.

    1984-09-25

    A reversing heat exchanger of the plate and fin type having multiple aluminum parting sheets in a stacked arrangement with corrugated fins separating the sheets to form multiple flow paths, means for closing the ends of the sheets, an input manifold arrangement of headers for the warm end of of the exchanger and an output manifold arrangement for the cold end of the exchanger with the input air feed stream header and the waste gas exhaust header having an alloy of zinc and aluminum coated on the inside surface for providing corrosion protection to the stack.

  11. Heat exchanger using graphite foam

    SciTech Connect

    Campagna, Michael Joseph; Callas, James John

    2012-09-25

    A heat exchanger is disclosed. The heat exchanger may have an inlet configured to receive a first fluid and an outlet configured to discharge the first fluid. The heat exchanger may further have at least one passageway configured to conduct the first fluid from the inlet to the outlet. The at least one passageway may be composed of a graphite foam and a layer of graphite material on the exterior of the graphite foam. The layer of graphite material may form at least a partial barrier between the first fluid and a second fluid external to the at least one passageway.

  12. Nonlocal exchange correlation in screened-exchange densityfunctional methods

    SciTech Connect

    Lee, Byounghak; Wang, Lin-Wang; Spataru, Catalin D.; Louie,Steven G.

    2007-04-22

    We present a systematic study on the exchange-correlationeffects in screened-exchange local density functional method. Toinvestigate the effects of the screened-exchange potential in the bandgap correction, we have compared the exchange-correlation potential termin the sX-LDA formalism with the self-energy term in the GWapproximation. It is found that the band gap correction of the sX-LDAmethod primarily comes from the downshift of valence band states,resulting from the enhancement of bonding and the increase of ionizationenergy. The band gap correction in the GW method, on the contrary, comesin large part from the increase of theconduction band energies. We alsostudied the effects of the screened-exchange potential in the totalenergy by investigating the exchange-correlation hole in comparison withquantum Monte Carlo calculations. When the Thomas-Fermi screening isused, the sX-LDA method overestimates (underestimates) theexchange-correlation hole in short (long) range. From theexchange-correlation energy analysis we found that the LDA method yieldsbetter absolute total energy than sX-LDA method.

  13. Marriage exchanges, seed exchanges, and the dynamics of manioc diversity

    PubMed Central

    Delêtre, Marc; McKey, Doyle B.; Hodkinson, Trevor R.

    2011-01-01

    The conservation of crop genetic resources requires understanding the different variables—cultural, social, and economic—that impinge on crop diversity. In small-scale farming systems, seed exchanges represent a key mechanism in the dynamics of crop genetic diversity, and analyzing the rules that structure social networks of seed exchange between farmer communities can help decipher patterns of crop genetic diversity. Using a combination of ethnobotanical and molecular genetic approaches, we investigated the relationships between regional patterns of manioc genetic diversity in Gabon and local networks of seed exchange. Spatially explicit Bayesian clustering methods showed that geographical discontinuities of manioc genetic diversity mirror major ethnolinguistic boundaries, with a southern matrilineal domain characterized by high levels of varietal diversity and a northern patrilineal domain characterized by low varietal diversity. Borrowing concepts from anthropology—kinship, bridewealth, and filiation—we analyzed the relationships between marriage exchanges and seed exchange networks in patrilineal and matrilineal societies. We demonstrate that, by defining marriage prohibitions, kinship systems structure social networks of exchange between farmer communities and influence the movement of seeds in metapopulations, shaping crop diversity at local and regional levels. PMID:22042843

  14. Monte Carlo study on exchange bias and coercivity properties in coupled ferromagnetic/antiferromagnetic films

    NASA Astrophysics Data System (ADS)

    Jiang, Liqin; Shen, Shuangjuan; Zhang, Jian-Min; Feng, Qian; Huang, Zhigao

    2015-12-01

    Based on Monte Carlo simulation, a model consisting of an antiferromagnetic (AFM) film coupled to a ferromagnetic (FM) film is developed to study the exchange bias and coercivity phenomenon. It is suggested that exchange bias is a consequence of exchange coupling in the AFM/FM interface, and the AFM anisotropy needs to have a threshold value for the occurrence of exchange bias. Simultaneously, exchange bias and coercivity as functions of the value of anisotropy, exchange coupling and film thickness are studied. By inducing a thickness dependence of the anisotropy in FM film, the coercivity can be reduced or enhanced by choosing suitable magnetic parameters, which can better account for the discrepancies found in previous studies. The results also provide evidence for the absence of a direct correlation between coercivity and exchange bias, which is in agreement with other studies.

  15. 75 FR 51138 - Self-Regulatory Organizations; BATS Exchange, Inc.; Chicago Board Options Exchange, Incorporated...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-18

    ... Exchange Act Release Nos. 62251 (June 10, 2010), 75 FR 34183 (June 16, 2010); 62252 (June 10, 2010), 75 FR...; BATS Exchange, Inc.; Chicago Board Options Exchange, Incorporated; Chicago Stock Exchange, Inc.; EDGA... Securities Exchange LLC; NASDAQ OMX BX, Inc.; The NASDAQ Stock Market LLC; National Stock Exchange, Inc.;...

  16. 22 CFR Appendix B to Part 62 - Exchange Visitor Program Services, Exchange-Visitor Program Application

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Exchange Visitor Program Services, Exchange-Visitor Program Application B Appendix B to Part 62 Foreign Relations DEPARTMENT OF STATE PUBLIC DIPLOMACY AND EXCHANGES EXCHANGE VISITOR PROGRAM Pt. 62, App. B Appendix B to Part 62—Exchange Visitor Program Services, Exchange-Visitor...

  17. Polar Aprotic Modifiers for Chromatographic Separation and Back-Exchange Reduction for Protein Hydrogen/Deuterium Exchange Monitored by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Valeja, Santosh G.; Emmett, Mark R.; Marshall, Alan G.

    2012-04-01

    Hydrogen/deuterium exchange monitored by mass spectrometry is an important non-perturbing tool to study protein structure and protein-protein interactions. However, water in the reversed-phase liquid chromatography mobile phase leads to back-exchange of D for H during chromatographic separation of proteolytic peptides following H/D exchange, resulting in incorrect identification of fast-exchanging hydrogens as unexchanged hydrogens. Previously, fast high-performance liquid chromatography (HPLC) and supercritical fluid chromatography have been shown to decrease back-exchange. Here, we show that replacement of up to 40% of the water in the LC mobile phase by the modifiers, dimethylformamide (DMF) and N-methylpyrrolidone (NMP) (i.e., polar organic modifiers that lack rapid exchanging hydrogens), significantly reduces back-exchange. On-line LC micro-ESI FT-ICR MS resolves overlapped proteolytic peptide isotopic distributions, allowing for quantitative determination of the extent of back-exchange. The DMF modified solvent composition also improves chromatographic separation while reducing back-exchange relative to conventional solvent.

  18. Anion exchange polymer electrolytes

    DOEpatents

    Kim, Yu Seung; Kim, Dae Sik; Lee, Kwan-Soo

    2013-07-23

    Solid anion exchange polymer electrolytes and compositions comprising chemical compounds comprising a polymeric core, a spacer A, and a guanidine base, wherein said chemical compound is uniformly dispersed in a suitable solvent and has the structure: ##STR00001## wherein: i) A is a spacer having the structure O, S, SO.sub.2, --NH--, --N(CH.sub.2).sub.n, wherein n=1-10, --(CH.sub.2).sub.n--CH.sub.3--, wherein n=1-10, SO.sub.2-Ph, CO-Ph, ##STR00002## wherein R.sub.5, R.sub.6, R.sub.7 and R.sub.8 each are independently --H, --NH.sub.2, F, Cl, Br, CN, or a C.sub.1-C.sub.6 alkyl group, or any combination of thereof; ii) R.sub.9, R.sub.10, R.sub.11, R.sub.12, or R.sub.13 each independently are --H, --CH.sub.3, --NH.sub.2, --NO, --CH.sub.nCH.sub.3 where n=1-6, HC.dbd.O--, NH.sub.2C.dbd.O--, --CH.sub.nCOOH where n=1-6, --(CH.sub.2).sub.n--C(NH.sub.2)--COOH where n=1-6, --CH--(COOH)--CH.sub.2--COOH, --CH.sub.2--CH(O--CH.sub.2CH.sub.3).sub.2, --(C.dbd.S)--NH.sub.2, --(C.dbd.NH)--N--(CH.sub.2).sub.nCH.sub.3, where n=0-6, --NH--(C.dbd.S)--SH, --CH.sub.2--(C.dbd.O)--O--C(CH.sub.3).sub.3, --O--(CH.sub.2).sub.n--CH--(NH.sub.2)--COOH, where n=1-6, --(CH.sub.2).sub.n--CH.dbd.CH wherein n=1-6, --(CH.sub.2).sub.n--CH--CN wherein n=1-6, an aromatic group such as a phenyl, benzyl, phenoxy, methylbenzyl, nitrogen-substituted benzyl or phenyl groups, a halide, or halide-substituted methyl groups; and iii) wherein the composition is suitable for use in a membrane electrode assembly.

  19. Pu Anion Exchange Process Intensification

    SciTech Connect

    Taylor-Pashow, K.

    2015-10-08

    This project seeks to improve the efficiency of the plutonium anion-exchange process for purifying Pu through the development of alternate ion-exchange media. The objective of the project in FY15 was to develop and test a porous foam monolith material that could serve as a replacement for the current anion-exchange resin, Reillex® HPQ, used at the Savannah River Site (SRS) for purifying Pu. The new material provides advantages in efficiency over the current resin by the elimination of diffusive mass transport through large granular resin beads. By replacing the large resin beads with a porous foam there is much more efficient contact between the Pu solution and the anion-exchange sites present on the material. Several samples of a polystyrene based foam grafted with poly(4-vinylpyridine) were prepared and the Pu sorption was tested in batch contact tests.

  20. Phase Change Material Heat Exchangers

    NASA Video Gallery

    NASA’s Game Changing Development is taking on a technologydevelopment and demonstration effort to design, build, and test the next generation of Phase Change Material Heat Exchangers (PCM HXs) on ...

  1. Heat pipe array heat exchanger

    DOEpatents

    Reimann, Robert C.

    1987-08-25

    A heat pipe arrangement for exchanging heat between two different temperature fluids. The heat pipe arrangement is in a ounterflow relationship to increase the efficiency of the coupling of the heat from a heat source to a heat sink.

  2. A novel process for key exchange avoiding man-inmiddle attack

    NASA Astrophysics Data System (ADS)

    Biswas, Barun; Basuli, Krishnendu

    2012-09-01

    For the security porpoise in the internet cryptography is one of the most important subjects nowadays. Designing a cypher for data exchange between two nodes or receiver and sender deals with one of the troubleshoot jobs. In our proposed algorithm we try to introduce a new technique in the field of cryptography. We are hopeful that this new technique will sure reduces the overhead of data or key exchange between nodes. Here we will discuss the symmetric key exchange between nodes

  3. Expert System For Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Bagby, D. Gordon; Cormier, Reginald A.

    1991-01-01

    Diagnosis simplified for non-engineers. Developmental expert-system computer program assists operator in controlling, monitoring operation, diagnosing malfunctions, and ordering repairs of heat-exchanger system dissipating heat generated by 20-kW radio transmitter. System includes not only heat exchanger but also pumps, fans, sensors, valves, reservoir, and associated plumbing. Program conceived to assist operator while avoiding cost of keeping engineer in full-time attendance. Similar programs developed for heating, ventilating, and air-conditioning systems.

  4. Ion exchange - Simulation and experiment

    NASA Technical Reports Server (NTRS)

    Herrmann, Cal C.; Finn, John E.

    1991-01-01

    A FORTRAN program for simulating multicomponent adsorption by ion-exchange resins was adapted for use as both an ASPEN-callable module and as a free-standing simulator of the ion-exchange bed. Four polystyrene-divinylbenzene sulfonic acid resins have been characterized for three principal ions. It is concluded that a chelating resin appears appropriate as a heavy-metal trap. The same ASPEN-callable module is used to model this resin when Wilson parameters can be obtained.

  5. Isotope exchange in oxide-containing catalyst

    NASA Technical Reports Server (NTRS)

    Brown, Kenneth G. (Inventor); Upchurch, Billy T. (Inventor); Hess, Robert V. (Inventor); Miller, Irvin M. (Inventor); Schryer, David R. (Inventor); Sidney, Barry D. (Inventor); Wood, George M. (Inventor); Hoyt, Ronald F. (Inventor)

    1989-01-01

    A method of exchanging rare-isotope oxygen for common-isotope oxygen in the top several layers of an oxide-containing catalyst is disclosed. A sample of an oxide-containing catalyst is exposed to a flowing stream of reducing gas in an inert carrier gas at a temperature suitable for the removal of the reactive common-isotope oxygen atoms from the surface layer or layers of the catalyst without damaging the catalyst structure. The reduction temperature must be higher than any at which the catalyst will subsequently operate. Sufficient reducing gas is used to allow removal of all the reactive common-isotope oxygen atoms in the top several layers of the catalyst. The catalyst is then reoxidized with the desired rare-isotope oxygen in sufficient quantity to replace all of the common-isotope oxygen that was removed.

  6. Purification and neutron emission reduction of 238Plutonium oxide by nitrate anion exchange processing

    NASA Astrophysics Data System (ADS)

    Pansoy-Hjelvik, M. E.; Brock, J.; Nixon, J. Z.; Moniz, P.; Silver, G.; Ramsey, K. B.

    2001-02-01

    The use of ion exchange during the aqueous purification of 238Pu oxide results in low levels of uranium, thorium, and americium in the product oxide. Neutron emission rates are also reduced in the product oxide. Fluorine introduced during the dissolution of impure fuel increases the neutron emission rate of the product oxide due to the 238Pu-19F alpha/n reaction. Treating the 238Pu solution with aluminum nitrate prior to ion exchange reduces the neutron emission rate in the product oxide. Data are presented to show that neutron emission rates and concentrations of uranium, thorium, and americium are reduced by ion exchange processing. .

  7. [External respiration, pulmonary gas exchange and energy expenditure in weightlessness].

    PubMed

    Kas'ian, I I; Makarov, G F

    1984-01-01

    This paper summarizes the data on external respiration and energy expenditures of men exposed to zero-g for 185 days and to 1/6 g on the lunar surface reported by Soviet and foreign authors. The paper also discusses factors that may be responsible for a higher level of gas exchange processes at reduced g. PMID:6392736

  8. Renormalization of NN Interaction with Relativistic Chiral Two Pion Exchange

    SciTech Connect

    Higa, R; Valderrama, M Pavon; Arriola, E Ruiz

    2007-06-14

    The renormalization of the NN interaction with the Chiral Two Pion Exchange Potential computed using relativistic baryon chiral perturbation theory is considered. The short distance singularity reduces the number of counter-terms to about a half as those in the heavy-baryon expansion. Phase shifts and deuteron properties are evaluated and a general overall agreement is observed.

  9. Student Exchange Programs: Statistical Report. Academic Year, 2009-10

    ERIC Educational Resources Information Center

    Western Interstate Commission for Higher Education, 2010

    2010-01-01

    Over 55 years ago, the Western states formed the Western Regional Education Compact and agreed to share higher education resources in the West through the Western Interstate Commission for Higher Education (WICHE). Through WICHE's three student exchange programs, nearly 26,000 residents of 15 Western states are enrolled at reduced levels of…

  10. Student Exchange Programs Statistical Report, Academic Year 2007-08

    ERIC Educational Resources Information Center

    Western Interstate Commission for Higher Education, 2008

    2008-01-01

    Through the three student exchange programs administered by the Western Interstate Commission for Higher Education (WICHE), approximately 23,300 residents of 15 Western states are enrolled at reduced levels of tuition across a spectrum of undergraduate, graduate, and professional programs. This annual report covers Fall 2007 enrollments in the…

  11. Closed system respirometry may underestimate tissue gas exchange and bias the respiratory exchange ratio (RER).

    PubMed

    Malte, Christian Lind; Nørgaard, Simon; Wang, Tobias

    2016-02-01

    Closed respirometry is a commonly used method to measure gas exchange in animals due to its apparent simplicity. Typically, the rates of O2 uptake and CO2 excretion (VO2 and VCO2, respectively) are assumed to be in steady state, such that the measured rates of gas exchange equal those at tissue level. In other words, the respiratory gas exchange ratio (RER) is assumed to equal the respiratory quotient (RQ). However, because the gas concentrations change progressively during closure, the animal inspires air with a progressively increasing CO2 concentration and decreasing O2 concentration. These changes will eventually affect gas exchange causing the O2 and CO2 stores within the animal to change. Because of the higher solubility/capacitance of CO2 in the tissues of the body, VCO2 will be more affected than VO2, and we hypothesize therefore that RER will become progressively underestimated as closure time is prolonged. This hypothesis was addressed by a combination of experimental studies involving closed respirometry on ball pythons (Python regius) as well as mathematical models of gas exchange. We show that increased closed duration of the respirometer reduces RER by up to 13%, and these findings may explain previous reports of RER values being below 0.7. Our model reveals that the maximally possible reduction in RER is determined by the storage capacity of the body for CO2 (product of size and specific capacitance) relative to the respirometer storage capacity. Furthermore, modeling also shows that pronounced ventilatory and circulatory response to hypercapnia can alleviate the reduction in RER. PMID:26523499

  12. Exchange of information between system and environment: Facts and myths

    NASA Astrophysics Data System (ADS)

    Wudarski, Filip A.; Petruccione, F.

    2016-03-01

    The exchange of “information” between a system and its environment based on the reduced dynamics is investigated. The association of trace distance with information cannot be stated, because of lack of symmetry between leakage from the system and absorbability by the environment. A measure of loss for the reduced dynamics is established, which may be seen as a deviation from exact unitary dynamics.

  13. Nanoparticle conversion chemistry: Kirkendall effect, galvanic exchange, and anion exchange

    NASA Astrophysics Data System (ADS)

    Anderson, Bryan D.; Tracy, Joseph B.

    2014-10-01

    Conversion chemistry is a rapidly maturing field, where chemical conversion of template nanoparticles (NPs) into new compositions is often accompanied by morphological changes, such as void formation. The principles and examples of three major classes of conversion chemical reactions are reviewed: the Kirkendall effect for metal NPs, galvanic exchange, and anion exchange, each of which can result in void formation in NPs. These reactions can be used to obtain complex structures that may not be attainable by other methods. During each kind of conversion chemical reaction, NPs undergo distinct chemical and morphological changes, and insights into the mechanisms of these reactions will allow for improved fine control and prediction of the structures of intermediates and products. Conversion of metal NPs into oxides, phosphides, sulphides, and selenides often occurs through the Kirkendall effect, where outward diffusion of metal atoms from the core is faster than inward diffusion of reactive species, resulting in void formation. In galvanic exchange reactions, metal NPs react with noble metal salts, where a redox reaction favours reduction and deposition of the noble metal (alloying) and oxidation and dissolution of the template metal (dealloying). In anion exchange reactions, addition of certain kinds of anions to solutions containing metal compound NPs drives anion exchange, which often results in significant morphological changes due to the large size of anions compared to cations. Conversion chemistry thus allows for the formation of NPs with complex compositions and structures, for which numerous applications are anticipated arising from their novel catalytic, electronic, optical, magnetic, and electrochemical properties.

  14. Reversible brain inactivation induces discontinuous gas exchange in cockroaches.

    PubMed

    Matthews, Philip G D; White, Craig R

    2013-06-01

    Many insects at rest breathe discontinuously, alternating between brief bouts of gas exchange and extended periods of breath-holding. The association between discontinuous gas exchange cycles (DGCs) and inactivity has long been recognised, leading to speculation that DGCs lie at one end of a continuum of gas exchange patterns, from continuous to discontinuous, linked to metabolic rate (MR). However, the neural hypothesis posits that it is the downregulation of brain activity and a change in the neural control of gas exchange, rather than low MR per se, which is responsible for the emergence of DGCs during inactivity. To test this, Nauphoeta cinerea cockroaches had their brains inactivated by applying a Peltier-chilled cold probe to the head. Once brain temperature fell to 8°C, cockroaches switched from a continuous to a discontinuous breathing pattern. Re-warming the brain abolished the DGC and re-established a continuous breathing pattern. Chilling the brain did not significantly reduce the cockroaches' MR and there was no association between the gas exchange pattern displayed by the insect and its MR. This demonstrates that DGCs can arise due to a decrease in brain activity and a change in the underlying regulation of gas exchange, and are not necessarily a simple consequence of low respiratory demand. PMID:23430991

  15. Determination of soil organic phosphorus exchange sensitivity

    NASA Astrophysics Data System (ADS)

    Shand, Charles; Wendler, Renate; Lumsdon, David; Cooper, Pat; George, Timothy; Brown, Lawrie; Giles, Courtney; Stutter, Marc; Menezes-Blackburn, Daniel; Zhang, Hao; Wearing, Catherine; Haygarth, Philip; Blackwell, Martin; Darch, Tegan

    2015-04-01

    Soils contain both organic and inorganic phosphorus (P) species in varying proportions. Studies have shown that many soils contain substantial amounts of inositol hexaphosphate (IHP) and there is much interest worldwide in developing strategies to make some use of this recalcitrant resource for plant growth to reduce P fertilizer inputs. Little is known about the preference of ion exchange processes in the solubilisation of organic vs inorganic P forms in soils, an important first step in making P forms bioavailable. Although they do not possess biotic functions, resins provides a simple means to deplete P forms in soil allowing investigation of exchange selectivity between inorganic and organic P forms. The aim of our work was to determine new understanding of exchange selectivity in soils and provide insight into potential depletion and plant uptake of soil phosphorus, with emphasis on organic forms such as IHP. For our study we used a Cambisol sampled from an agricultural area (Tayport) near Dundee in Scotland. The soil had a high Olsen (0.5 M sodium bicarbonate at pH 8.5) extractable P status (84 mg P/kg) and P-31 nuclear magnetic resonance analysis of its NaOH/EDTA extract showed it contained a substantial proportion of IHP (21 % of total extractable P). For resin extraction we used anion exchange resin sheets (4.17 cm each side) in bicarbonate form to minimise pH related solubilisation effects. We used 3.5 g of soil in 75 ml of water and added 1, 2 or 3 resin squares. After equilibration the resin squares were removed and replaced with fresh resin squares a further 3 times. Phosphorus was recovered from the resin sheets by elution with 0.25 M sulphuric acid and analysed by inductively coupled plasma spectroscopy to determine total P, and colorimetrically with malachite green to determine inorganic P with the remainder assigned to organic P. The data showed that the resin preferentially removed inorganic P and even after four sequential extractions little or

  16. Building Communities for the Exchange of Learning Objects: Theoretical Foundations and Requirements

    ERIC Educational Resources Information Center

    Koper, Rob; Pannekeet, Kees; Hendriks, Maaike; Hummel, Hans

    2004-01-01

    In order to reduce overall costs of developing high-quality digital courses (including both the content, and the learning and teaching activities), the exchange of learning objects has been recognized as a promising solution. This article makes an inventory of the issues involved in the exchange of learning objects within a community. It explores…

  17. Design of heat exchange element for plastic film heat exchanger

    NASA Astrophysics Data System (ADS)

    Guyer, E. C.; Brownell, D. L.

    1984-12-01

    This report presents the results of an effort to design a plastic film heat exchanger element (PFHX) suitable for use in an industrial heat pump evaporator. This report addresses the selection of materials, the expected flow and heat transfer behavior, and the mechanical design features of a parallel plate type exchanger that uses thin plastic films as the boundary between the two process fluids. Criteria for material selection are presented, candidate materials are reviewed, and material recommendations are provided. Heat transfer performance is addressed in terms of the overall or total coefficient of heat transfer between condensing steam and a confined falling film of water. Appropriate mechanical designs of water flow manifolds are described along with methods of fabrication and assembly. This report addresses only the individual heat exchange element.

  18. Securities and Exchange Commission Semiannual Regulatory Agenda

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-20

    ... [The Regulatory Plan and Unified Agenda of Federal Regulatory and Deregulatory Actions] Part XXIV Securities and Exchange Commission Semiannual Regulatory Agenda ] SECURITIES AND EXCHANGE COMMISSION (SEC) SECURITIES AND EXCHANGE COMMISSION 17 CFR Ch. II Regulatory Flexibility Agenda AGENCY: Securities and Exchange Commission. ACTION:...

  19. Conflict and Fairness in Social Exchange

    ERIC Educational Resources Information Center

    Molm, Linda D.; Collett, Jessica L.; Schaefer, David R.

    2006-01-01

    Inherent to all social exchange relations are elements of both cooperation and competition. We develop and test a theoretical model which proposes that the relative salience of the competitive, conflictual elements of exchange mediate and explain the negative effects of negotiated exchange, as compared with reciprocal exchange, on actors'…

  20. Building Cohesion in Positively Connected Exchange Networks

    ERIC Educational Resources Information Center

    Schaefer, David R.; Kornienko, Olga

    2009-01-01

    This research investigates the process through which individuals build cohesive relationships in positively connected exchange relations. Positive connections exist any time exchange in one relation must precede exchange in another. Such situations arise through gatekeeping, in generalized exchange contexts, and when resources diffuse across a…

  1. Radiation Studies with Argentine Ion Exchange Material

    SciTech Connect

    Crawford, C.L.

    2002-06-28

    A recent technology exchange between Argentina Nuclear Energy Commission (CNEA) and the US Department of Energy involved vitrification studies of ion exchange resins. Details of the spent ion exchange resins currently stored at two Argentine nuclear power plants, Atucha I and Embalse, have been presented in earlier reports. The present study examines irradiation of simulant samples of ion exchange resins.

  2. 78 FR 42439 - Retail Foreign Exchange Transactions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-16

    ... Retail Foreign Exchange Transactions, Exchange Act Release No. 64874 (July 13, 2011), 76 FR 41676 (July... Foreign Exchange Transactions and Intermediaries, 75 FR 3282 (Jan. 20, 2010) (``CFTC Proposing Release... Recordkeeping; Final Rule, Exchange Act Release No. 67453 (July 18, 2012), 77 FR 48207 (Aug. 13,...

  3. A Colorful Ion Exchange Experiment

    NASA Astrophysics Data System (ADS)

    Mendes, Adélio

    1999-11-01

    A colorful ion-exchange experiment is described. The use of a resin with an adsorbed acid-base indicator allows students to follow the progress of the ion-exchange front along the column. In parallel, students can follow the ion-exchange breakthrough curve using a continuous conductometric cell at the column outlet. In the present example, K+ (KCl) exchanges with H+ (HCl) in a strong cationic resin (Amberlite IR 120). The adsorbed indicator is methyl violet. Sorption equilibrium is favorable to the K+ ions. Monovalent ions, used in this experiment, have the disadvantage of usually being colorless (except perhaps permanganate, but this is an extremely strong oxidant which attacks the resin). On the other hand, many divalent ions are colorful but the shape of the concentration front is hard to explain qualitatively as well as quantitatively. That is because the shape of the front depends on the total ionic concentration. However, color can be introduced in a monovalent ion-exchange system by adding an appropriate acid-base indicator to the resin. The text describes this experiment qualitatively. A simplified quantitative description, using the solute movement theory, can be found online.

  4. Electrically Switched Cesium Ion Exchange

    SciTech Connect

    JPH Sukamto; ML Lilga; RK Orth

    1998-10-23

    This report discusses the results of work to develop Electrically Switched Ion Exchange (ESIX) for separations of ions from waste streams relevant to DOE site clean-up. ESIX combines ion exchange and electrochemistry to provide a selective, reversible method for radionuclide separation that lowers costs and minimizes secondary waste generation typically associated with conventional ion exchange. In the ESIX process, an electroactive ion exchange film is deposited onto. a high surface area electrode, and ion uptake and elution are controlled directly by modulating the potential of the film. As a result, the production of secondary waste is minimized, since the large volumes of solution associated with elution, wash, and regeneration cycles typical of standard ion exchange are not needed for the ESIX process. The document is presented in two parts: Part I, the Summary Report, discusses the objectives of the project, describes the ESIX concept and the approach taken, and summarizes the major results; Part II, the Technology Description, provides a technical description of the experimental procedures and in-depth discussions on modeling, case studies, and cost comparisons between ESIX and currently used technologies.

  5. Influence of the Thermomechanical Treatment on the Intergranular Corrosion Susceptibility of Zn-Modified Al-5.1 Wt Pct Mg-0.7 Wt Pct Mn Alloy Sheet

    NASA Astrophysics Data System (ADS)

    Halap, Akram; Radetić, Tamara; Popović, Miljana; Romhanji, Endre

    2014-09-01

    In this study, the effect of thermomechanical treatment on intergranular corrosion (IGC) susceptibility of the Zn-modified Al-5.1 wt pct Mg-0.7 wt pct Mn alloy plates was investigated. The specimens underwent varied amounts of cold work, while final annealing was conducted in the 493 K to 533 K (220 °C to 260 °C) temperature range. It was shown that the extent of cold work, especially at lower temperatures of treatment, had a profound effect on the corrosion resistance of the alloy. Such observation was in direct correlation with the morphology of precipitated ternary grain boundary phase (Al-Mg-Zn). Microstructural characterization showed that, depending on the amount of cold work, different deformation substructures were created, which, in turn, influenced kinetics and the mechanism of precipitation. Wetting of the grain boundaries by the ternary grain boundary phase (Al-Mg-Zn) was a signature of the IGC susceptible state and occurred in the specimens that were subjected to a lower degree of cold work. The specimens that underwent a higher degree of cold work (over 30 pct) showed superior corrosion resistance as a result of ternary grain boundary phase (Al-Mg-Zn) precipitation in the form of discrete particles at the grain boundaries as well as in grain interiors.

  6. Concept of advanced spent fuel reprocessing based on ion exchange

    SciTech Connect

    Suzuki, Tatsuya; Takahashi, Kazuyuki; Nogami, Masanobu; Nomura, Masao; Fujii, Yasuhiko; Ozawa, Masaki |; Koyama, Shinichi; Mimura, Hitosi; Fujita, Reiko

    2007-07-01

    . Furthermore, the ion exchange is appropriate for multi-element mutual separation rather than single element extraction. In the future, ion exchange reprocessing would be expected to be the comprehensive separation process for spent fuels to recover precious and usable elements and to reduce the amount of wastes. (authors)

  7. Random matrix theory and portfolio optimization in Moroccan stock exchange

    NASA Astrophysics Data System (ADS)

    El Alaoui, Marwane

    2015-09-01

    In this work, we use random matrix theory to analyze eigenvalues and see if there is a presence of pertinent information by using Marčenko-Pastur distribution. Thus, we study cross-correlation among stocks of Casablanca Stock Exchange. Moreover, we clean correlation matrix from noisy elements to see if the gap between predicted risk and realized risk would be reduced. We also analyze eigenvectors components distributions and their degree of deviations by computing the inverse participation ratio. This analysis is a way to understand the correlation structure among stocks of Casablanca Stock Exchange portfolio.

  8. Turbulent energy exchange: Calculation and relevance for profile prediction

    SciTech Connect

    Candy, J.

    2013-08-15

    The anomalous heat production due to turbulence is neither routinely calculated in nonlinear gyrokinetic simulations nor routinely retained in profile prediction studies. In this work, we develop a symmetrized method to compute the exchange which dramatically reduces the intermittency in the time-dependent moment, thereby improving the accuracy of the time-average. We also examine the practical impact on transport-timescale simulations, and show that the exchange has only a minor impact on profile evolution for a well-studied DIII-D discharge.

  9. Multinucleon exchange in quasifission reactions

    NASA Astrophysics Data System (ADS)

    Ayik, S.; Yilmaz, B.; Yilmaz, O.

    2015-12-01

    The nucleon exchange mechanism is investigated in the central collisions of 40Ca+238U and 48Ca+238U systems near the quasifission regime in the framework of the stochastic mean-field (SMF) approach. Sufficiently below the fusion barrier, a dinuclear structure in the collisions is maintained to a large extent. Consequently, it is possible to describe nucleon exchange as a diffusion process familiar from deep-inelastic collisions. Diffusion coefficients for proton and neutron exchange are determined from the microscopic basis of the SMF approach in the semiclassical framework. Calculations show that after a fast charge equilibration the system drifts toward symmetry over a very long interaction time. Large dispersions of proton and neutron distributions of the produced fragments indicate that the diffusion mechanism may help to populate heavy transuranium elements near the quasifission regime in these collisions.

  10. Pion exchange at high energies

    SciTech Connect

    Jones, L.M.

    1980-07-01

    The state of Regge pion exchange calculations for high-energy reactions is reviewed. Experimental evidence is summarized to show that (i) the pion trajectory has a slope similar to that of other trajectories; (ii) the pion exchange contribution can dominate contributions of higher trajectories up to quite a large energy; (iii) many two-body cross sections with large pion contributions can be fit only by models which allow for kinematical conspiracy at t=0. The theory of kinematic conspiracy is reviewed for two-body amplitudes, and calculations of the conspiring pion--Pomeron cut discussed. The author then summarizes recent work on pion exchange in Reggeized Deck models for multiparticle final states, with emphasis on the predictions of various models (with and without resonances) for phases of the partial wave amplitudes.

  11. NASA data exchange standards for computational fluid dynamics

    NASA Technical Reports Server (NTRS)

    Blake, Matthew

    1993-01-01

    This paper covers the following topics in viewgraph format: purpose of data exchange standards; data exchange in engineering analysis/CFD; geometry data exchange through existing product data exchange standards, NASA Data Exchange Committee, and NASA-IGES (Initial Graphics Exchange Specification); CFD grid and solution data exchange; and data exchange for multi-disciplinary engineering.

  12. Grafted methylenediphosphonate ion exchange resins

    DOEpatents

    Trochimcznk, A.W.; Gatrone, R.C.; Alexandratos, S.; Horwitz, E.P.

    1997-04-08

    An ion exchange resin is disclosed that is comprised of an insoluble copolymer onto which are grafted pendent groups that provide 1.0 to about 10 mmol/g dry weight phosphorus. The pendent groups have the formula as shown in the patent wherein R is hydrogen, a cation or mixtures thereof; and R{sup 1} is hydrogen or an C{sub 1}-C{sub 2} alkyl group. The resin also contains zero to about 5 mmol/g dry weight of pendent aromatic sulfonate groups. Processes for making and using an ion exchange resin are also disclosed.

  13. Grafted methylenediphosphonate ion exchange resins

    DOEpatents

    Trochimcznk, Andrzej W.; Gatrone, Ralph C.; Alexandratos, Spiro; Horwitz, E. Philip

    1997-01-01

    An ion exchange resin is disclosed that is comprised of an insoluble copolymer onto which are grafted pendent groups that provide 1.0 to about 10 mmol/g dry weight phosphorous. The pendent groups have the formula ##STR1## wherein R is hydrogen, a cation or mixtures thereof; and R.sup.1 is hydrogen or an C.sub.1 -C.sub.2 alkyl group. The resin also contains zero to about 5 mmol/g dry weight of pendent aromatic sulfonate groups. Processes for making and using an ion exchange resin are also disclosed.

  14. Grafted methylenediphosphonate ion exchange resins

    DOEpatents

    Trochimcznk, Andrzej W.; Gatrone, Ralph C.; Alexandratos, Spiro; Horwitz, E. Philip

    1998-01-27

    An ion exchange resin is disclosed that is comprised of an insoluble copolymer onto which are grafted pendent groups that provide 1.0 to about 10 mmol/g dry weight phosphorous. The pendent groups have the formula ##STR1## wherein R is hydrogen, a cation or mixtures thereof; and R.sup.1 is hydrogen or an C.sub.1 -C.sub.2 alkyl group. The resin also contains zero to about 5 mmol/g dry weight of pendent aromatic sulfonate groups. Processes for making and using an ion exchange-resin are also disclosed.

  15. 78 FR 46622 - Application of Topaz Exchange, LLC for Registration as a National Securities Exchange; Findings...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-01

    .... See Securities Exchange Act Release No. 69011, 78 FR 14844 (March 7, 2013). Because Topaz Exchange's... Exchange. \\5\\ See Securities Exchange Act Release No. 69012 (March 1, 2013), 78 FR 14847 (``Notice''). \\6... Exchange Act Release No. 56955 (December 13, 2007), 72 FR 71979 (December 19, 2007) (File No....

  16. Interlayer exchange coupling effect of L1(0) CoPt based exchange coupled composite media.

    PubMed

    Yang, Yang; Pandey, K K M; Chen, J S; Chow, G M; Hu, J F

    2011-03-01

    In this work, effects of exchange coupling of soft magnetic layer on switching field and magnetization reversal behaviour of CoPt-SiO2(soft)/CoPt-SiO2(hard) exchange coupled media were investigated. With increasing the thickness of the soft layer, both the coercivity and magnetization squareness of composite media decreased. Soft layer thickness 4 nm and below was more effective to significantly reduce the switching field than that above 4 nm. More incoherent switching behavior was observed with increasing soft layer thickness. PMID:21449436

  17. Social preferences influence the short-term exchange of social grooming among male bonobos.

    PubMed

    Surbeck, Martin; Hohmann, Gottfried

    2015-03-01

    The emotional mediation hypothesis proposes a mediating role of social bonds in the exchange of services. This model predicts that the form of short-term exchange of services depends on the relationship between the individuals involved. Here, we test this prediction in the exchange of grooming among males in a wild bonobo community for which close relatedness could be excluded. As bonobo males hardly engage in food sharing or agonistic support, grooming is mainly exchanged for grooming. While overall grooming, both given and received, correlates across dyads and within sessions, the form of grooming exchange within a given session differs according to dyadic association preferences. Individuals with a higher tendency to associate, ergo more familiar individuals, exhibit larger time differences and reduced reciprocation in consecutive grooming bouts than less familiar individuals. These results support the idea that emotional components are involved in the exchange of services between unrelated individuals. PMID:25519436

  18. Limits on relief through constrained exchange on random graphs

    NASA Astrophysics Data System (ADS)

    LaViolette, Randall A.; Ellebracht, Lory A.; Gieseler, Charles J.

    2007-09-01

    Agents are represented by nodes on a random graph (e.g., “small world”). Each agent is endowed with a zero-mean random value that may be either positive or negative. All agents attempt to find relief, i.e., to reduce the magnitude of that initial value, to zero if possible, through exchanges. The exchange occurs only between the agents that are linked, a constraint that turns out to dominate the results. The exchange process continues until Pareto equilibrium is achieved. Only 40-90% of the agents achieved relief on small-world graphs with mean degree between 2 and 40. Even fewer agents achieved relief on scale-free-like graphs with a truncated power-law degree distribution. The rate at which relief grew with increasing degree was slow, only at most logarithmic for all of the graphs considered; viewed in reverse, the fraction of nodes that achieve relief is resilient to the removal of links.

  19. New anion-exchange polymers for improved separations

    SciTech Connect

    Jarvinen, G.D.; Barr, M.E.; Marsh, S.F.

    1997-08-01

    Objective is to improve the understanding of how the structure of a new class of anion-exchange polymers controls the binding of anionic actinide complexes from solution. This is needed to develop practical separation systems that will reduce the cost of actinide processing operations within the DOE complex. In addition anion exchange is widely used in industry. Several new series of bifunctional anion- exchange polymers have been designed, synthesized, and tested for removing Pu(IV), Am(III), and U(VI) from nitric acid. The polymers contain a pyridinium site derived from the host poly(4-vinylpyridine) and a second cationic site attached through a chain of 2 to 6 methylene groups. The new polymers removed Pu four to ten times more efficiently than the best commercial materials.

  20. Effect of interlayer exchange coupling on magnetic chiral structures

    SciTech Connect

    Kang, S. P.; Kwon, H. Y.; Kim, H. S.; Shim, J. H.; Won, C.

    2015-07-28

    We numerically investigated the effect of interlayer exchange coupling on magnetic chiral structures, such as a helical/cycloidal spin structure and magnetic skyrmion crystal (SkX), which are produced in a magnetic system involving the Dzyaloshinskii-Moriya interaction (DMI). We report the existence of a phase transition where the length scale of magnetic structure discontinuously changes, and that there can be a novel magnetic structure around the phase boundary that exhibits double-ordering lengths of magnetic structure. Therefore, the system has multiple ground phases determined by the ratio of interlayer exchange coupling strength and DMI strength. Furthermore, we investigated the critical condition of the external perpendicular field required for the SkX. The critical field is significantly reduced under the effect of interlayer exchange coupling, which can stabilize the SkX without the external field.

  1. A time-resolved study on the interaction of oppositely charged bicelles--implications on the charged lipid exchange kinetics.

    PubMed

    Yang, Po-Wei; Lin, Tsang-Lang; Hu, Yuan; Jeng, U-Ser

    2015-03-21

    Time-resolved small-angle X-ray scattering was applied to study charged lipid exchange between oppositely charged disc-shaped bicelles. The exchange of charged lipids gradually reduces the surface charge density and weakens the electrostatic attraction between the oppositely charged bicelles which form alternately stacked aggregates upon mixing. Initially, at a high surface charge density with almost no free water layer between the stacked bicelles, fast exchange kinetics dominate the exchange process. At a later stage with a lower surface charge density and a larger water gap between the stacked bicelles, slow exchange kinetics take over. The fast exchange kinetics are correlated with the close contact of the bicelles when there is almost no free water layer between the tightly bound bicelles with a charged lipid exchange time constant as short as 20-40 min. When the water gap becomes large enough to have a free water layer between the stacked bicelles, the fast lipid exchange kinetics are taken over by slow lipid exchange kinetics with time constants around 200-300 min, which are comparable to the typical time constant of lipid exchange between vesicles in aqueous solution. These two kinds of exchange mode fit well with the lipid exchange models of transient hemifusion for the fast mode and monomer exchange for the slow mode. PMID:25649711

  2. Primer on nuclear exchange models

    SciTech Connect

    Hafemeister, David

    2014-05-09

    Basic physics is applied to nuclear force exchange models between two nations. Ultimately, this scenario approach can be used to try and answer the age old question of 'how much is enough?' This work is based on Chapter 2 of Physics of Societal Issues: Calculations on National Security, Environment and Energy (Springer, 2007 and 2014)

  3. Homans on Exchange: Hedonism Revived

    ERIC Educational Resources Information Center

    Abrahamsson, Bengt

    1970-01-01

    George C. Homan's theory on social exchange is critically examined and found to have serious shortcomings with regard to its deductive and inductive aspects. An expecially prominent shortcoming concerns the tautological character of his concept of reward," which makes his theory deductively unclear and empirically untestable. Homan's critique…

  4. Export bill and scientific exchanges

    NASA Astrophysics Data System (ADS)

    President Ronald Reagan has signed into law the reauthorization of the Export Administration Act (EAA), first passed in 1979. The amended version of the law, signed July 12, includes a policy statement in support of “vigorous scientific enterprise. . .in accordance with applicable provisions of law. . .by means of publication, teaching, conferences, and other forms of scholarly exchange.”

  5. LENs: The Learning Exchange Networks.

    ERIC Educational Resources Information Center

    Hedley, Pat

    LENs (Learning Exchange Networks) modules and seminars are a series of self-directed learning resources that are written by and for faculty. The intent of the modules and seminars is to enhance faculty learning in the fundamentals of curriculum design and adult learning. The original LENs program was developed at Humber College, Toronto, Ontario,…

  6. International Educational Exchange. A Bibliography.

    ERIC Educational Resources Information Center

    Spencer, Richard E.; Awe, Ruth

    This bibliography was undertaken to facilitate and encourage further research in international education. Sources of the data include library reference works, University Microfilms containing PhD dissertations, US government agencies, foundations and universities. Entries include publications on the International Exchange of Students, Teachers and…

  7. Helping Behavior and Social Exchange

    ERIC Educational Resources Information Center

    Enzle, Michael E.; Lowe, Charles A.

    1976-01-01

    Social exchange theory was employed to predict instigative helping behavior as a function of two types of resources available to the recipient for reciprocation (social and non-social). The possibility of influencing reciprocation of both types of resources produced significant increases in subjects' helping. (Author)

  8. International Exchange of Official Publications.

    ERIC Educational Resources Information Center

    Metz, Johannes

    International exchange agreements potentially serve to facilitate the free access to official materials from abroad, similar to depository programs for national official publications collections and with corresponding issues of collecting and archiving electronic publications. In this connection, it is necessary to distinguish between exchange…

  9. Citizenship behavior and social exchange.

    PubMed

    Konovsky, M A; Pugh, S D

    1994-06-01

    This article develops and empirically examines a social exchange model of organizational citizenship behavior. An employee's trust in a supervisor is proposed to mediate the relationship between procedural fairness in the supervisor's decision making and employee citizenship. Data from 475 hospital employees and their supervisors were consistent with our model. We discuss future research directions. PMID:10134637

  10. Gambling, exchange systems, and moralities.

    PubMed

    Binde, Per

    2005-01-01

    History and ethnography show us that, across societies of the past and present, gambling varies considerably with respect to its organization, social meanings, and how it is regarded in moral terms. This paper presents a basic scheme for analyzing the relationship between gambling and society. A theoretical starting point is that reciprocity is fundamental to social and economic systems. An anthropological theory of exchange systems makes a broad distinction between a structural dimension (generalized versus balanced reciprocity) and a normative dimension (from voluntary to involuntary). A model of four basic forms of reciprocity, each having a characteristic exchange mode and morality, can thus be constructed. Gambling is here understood as an exchange system embedded in the reciprocal orders of society and having a necessary relationship to these; it can take on the characteristics of such an order or it can be regarded as conflicting with it. Much of the variation in the form and morality of gambling therefore emerges as systematic and explainable by a theory of forms of reciprocal exchange. PMID:16311877

  11. Knowledge Exchange with Sistema Scotland

    ERIC Educational Resources Information Center

    Allan, Julie; Moran, Nikki; Duffy, Celia; Loening, Gica

    2010-01-01

    This paper reports on a knowledge exchange project, funded by the Scottish Funding Council and undertaken by a group of researchers from three higher education institutions in Scotland and the project partner, Sistema Scotland. This newly established charity is attempting to implement a major programme of social change, developed in Venezuela,…

  12. Teachers' Centers Exchange Directory. 1982.

    ERIC Educational Resources Information Center

    Piper, Barbara

    The 198 teacher centers listed in this directory comprise a network of teacher center practitioners who communicate with the Teachers' Centers Exchange (Far West Laboratory for Educational Research and Development, San Francisco, California). Centers in the United States and Canada are listed alphabetically by state. Information on each center…

  13. Lightweight long life heat exchanger

    NASA Technical Reports Server (NTRS)

    Moore, E. K.

    1975-01-01

    The design, fabrication, and evaluation of a full scale shuttle-type condensing heat exchanger constructed of aluminum and utilizing aluminum clad titanium parting sheets is described. A long term salt spray test of candidate parting sheet specimens is described. The results of an investigation into an alternate method of making composite sheet material are discussed.

  14. A Model for Student Exchange

    NASA Astrophysics Data System (ADS)

    Teays, T.; Henry, R. C.; Nagchaudhuri, A.; Bowden, M.; Chen, G.

    2011-09-01

    We describe a successful summer program to exchange students among three universities, in which they conducted hands-on research related to NASA's strategic enterprises in earth and space sciences, with particular emphases on aerospace and related engineering fields. The program was a part of NASA's Minority Serving Institutions Partnership Development Competition.

  15. Nonadiabatic exchange dynamics during adiabatic frequency sweeps

    NASA Astrophysics Data System (ADS)

    Barbara, Thomas M.

    2016-04-01

    A Bloch equation analysis that includes relaxation and exchange effects during an adiabatic frequency swept pulse is presented. For a large class of sweeps, relaxation can be incorporated using simple first order perturbation theory. For anisochronous exchange, new expressions are derived for exchange augmented rotating frame relaxation. For isochronous exchange between sites with distinct relaxation rate constants outside the extreme narrowing limit, simple criteria for adiabatic exchange are derived and demonstrate that frequency sweeps commonly in use may not be adiabatic with regard to exchange unless the exchange rates are much larger than the relaxation rates. Otherwise, accurate assessment of the sensitivity to exchange dynamics will require numerical integration of the rate equations. Examples of this situation are given for experimentally relevant parameters believed to hold for in-vivo tissue. These results are of significance in the study of exchange induced contrast in magnetic resonance imaging.

  16. Evaluation of fluid bed heat exchanger optimization parameters. Final report

    SciTech Connect

    Not Available

    1980-03-01

    Uncertainty in the relationship of specific bed material properties to gas-side heat transfer in fluidized beds has inhibited the search for optimum bed materials and has led to over-conservative assumptions in the design of fluid bed heat exchangers. An experimental program was carried out to isolate the effects of particle density, thermal conductivity, and heat capacitance upon fluid bed heat transfer. A total of 31 tests were run with 18 different bed material loads on 12 material types; particle size variations were tested on several material types. The conceptual design of a fluidized bed evaporator unit was completed for a diesel exhaust heat recovery system. The evaporator heat transfer surface area was substantially reduced while the physical dimensions of the unit increased. Despite the overall increase in unit size, the overall cost was reduced. A study of relative economics associated with bed material selection was conducted. For the fluidized bed evaporator, it was found that zircon sand was the best choice among materials tested in this program, and that the selection of bed material substantially influences the overall system costs. The optimized fluid bed heat exchanger has an estimated cost 19% below a fin augmented tubular heat exchanger; 31% below a commercial design fluid bed heat exchanger; and 50% below a conventional plain tube heat exchanger. The comparisons being made for a 9.6 x 10/sup 6/ Btu/h waste heat boiler. The fluidized bed approach potentially has other advantages such as resistance to fouling. It is recommended that a study be conducted to develop a systematic selection of bed materials for fluidized bed heat exchanger applications, based upon findings of the study reported herein.

  17. A Literature Review on Health Information Exchange (HIE).

    PubMed

    Attallah, Nora; Gashgari, Horeya; Al Muallem, Yahya; Al Dogether, Majed; Al Moammary, Eman; Almeshari, Meshari; Househ, Mowafa

    2016-01-01

    Developing a national Health Information Exchange (HIE) for Saudi Arabia has developed into a priority for the Saudi Ministry of Health. In the process of conducting a literature review of existing opportunities and challenges of health information exchange in international hospitals and the possible implications of such studies on Saudi Arabia, an initial search was conducted in April 2015 yielding 31 articles from PubMed, Science Direct and other database using key terms such as: health information exchange, data exchange, health data exchange, data interoperability in health, lessons of data interoperability, opportunities of health information exchange, challenges of data integration, and challenges of data format and ontology. Research studies that were not related to the health care sector, that were not in English, or found not relevant to the purpose of the study were excluded. Only six studies were included in the review. Results show that there are many opportunities and challenges found in the literature which may impact how Saudi Arabia implements the national Health Information Exchange (HIE) strategy. Three primary challenges for HIE were identified including data formatting, semantic ontology, and building the HIE infrastructure. Opportunities for Saudi Arabia in implementing the HIE were also found in the literature such as improving the quality of healthcare services and reducing healthcare costs. Saudi Arabia is advancing in the electronic medical record (EMR) implementation especially with current changes on the level of authority and ministry structure. Building an EMR foundation will make the HIE simpler to implement for the Saudi Arabian Ministry of Health. PMID:27350496

  18. Gas Exchange with Mass Cultures of Algae

    PubMed Central

    Hannan, P. J.; Patouillet, Constance

    1963-01-01

    The performance of a small photosynthetic gas exchanger is described in which simultaneous measurements of suspension density, O2 production, and CO2 absorption are readily accomplished. The volume of suspension was 6200 ml. With the Sorokin strain of Chlorella pyrenoidosa 7-11-05, this unit produced 4500 cc of O2 per hr at a light intensity of 34,000 ft-c from each of six Quartzline lamps. At any given light intensity, the O2 production was proportional to the rate of CO2 input up to a maximum. The impetus for this study was the consideration of the algal system as a means of oxygen generation in a submarine. Based on the performance of this unit, the power requirement per man for a system having the geometry described would be 52 kw, but reasons are given for the hope that this may be reduced to less than 5 kw. PMID:14063789

  19. Reverse Emittance Exchange for Muon Colliders

    SciTech Connect

    V. Ivanov, A. Afanasev, C.M. Ankenbrandt, R.P. Johnson, G.M. Wang, S.A. Bogacz, Y.S. Derbenev

    2009-05-01

    Muon collider luminosity depends on the number of muons in the storage ring and on the transverse size of the beams in collision. Ionization cooling as it is currently envisioned will not cool the beam sizes sufficiently well to provide adequate luminosity without large muon intensities. Six-dimensional cooling schemes will reduce the longitudinal emittance of a muon beam so that smaller high frequency RF cavities can be used for later stages of cooling and for acceleration. However, the bunch length at collision energy is then shorter than needed to match the interaction region beta function. New ideas to shrink transverse beam dimensions by lengthening each bunch will help achieve high luminosity in muon colliders. Analytic expressions for the reverse emittance exchange mechanism were derived, including a new resonant method of beam focusing.

  20. A piloted simulation study of data link ATC message exchange

    NASA Technical Reports Server (NTRS)

    Waller, Marvin C.; Lohr, Gary W.

    1989-01-01

    Data link Air Traffic Control (ATC) and Air Traffic Service (ATS) message and data exchange offers the potential benefits of increased flight safety and efficiency by reducing communication errors and allowing more information to be transferred between aircraft and ground facilities. Digital communication also presents an opportunity to relieve the overloading of ATC radio frequencies which hampers message exchange during peak traffic hours in many busy terminal areas. A piloted simulation study to develop pilot factor guidelines and assess potential flight crew benefits and liabilities from using data link ATC message exchange was completed. The data link ATC message exchange concept, implemented on an existing navigation computer Control Display Unit (CDU) required maintaining a voice radio telephone link with an appropriate ATC facility. Flight crew comments, scanning behavior, and measurements of time spent in ATC communication activities for data link ATC message exchange were compared to similar measures for simulated conventional voice radio operations. The results show crew preference for the quieter flight deck environment and a perception of lower communication workload.

  1. Exchange Stiffness in Thin-Film Cobalt Alloys

    NASA Astrophysics Data System (ADS)

    Eyrich, Charles

    The exchange stiffness, Aex, is one of the key parameters controlling magnetization reversal in magnetic materials but is very difficult to measure, especially in thin films. We developed a new technique for measuring the exchange stiffness of a magnetic material based on the formation of a spin spiral within two antiferromagnetically coupled ferromagnetic films [1]. Using this method, I was able to measure the exchange stiffness of thin film Co alloyed with Cr, Fe, Ni, Pd, Pt and Ru. The results of this work showed that the rate at which a substituent element reduces the exchange stiffness is not directly related to its effect on the magnetization of the alloy. These measured trends have been understood by combining measurements of element specific magnetic moments obtained using X-ray magnetic circular dichroism (XMCD) and material specific modeling based on density functional theory (DFT) within the local density approximation (LDA). The experimental results also hint at significant reduction of the exchange stiffness at the interface that can account for the difference between our results and those obtained on bulk materials.

  2. Ultrafast reduction of exchange splitting in ferromagnetic nickel

    NASA Astrophysics Data System (ADS)

    Zhang, G. P.; Bai, Y. H.; George, Thomas F.

    2016-06-01

    A decade ago Rhie et al (2003 Phys. Rev. Lett. 90 247201) reported that when ferromagnetic nickel is subject to an intense ultrashort laser pulse, its exchange splitting is reduced quickly. But to simulate such reduction remains a big challenge. The popular rigid band approximation (RBA), where both the band structure and the exchange splitting are held fixed before and after laser excitation, is unsuitable for this purpose, while the time-dependent density functional theory could be time-consuming. To overcome these difficulties, we propose a time-dependent Liouville and density functional theory (TDLDFT) that integrates the time-dependent Liouville equation into the density functional theory. As a result, the excited charge density is reiterated back into the Kohn–Sham equation, and the band structure is allowed to change dynamically. Even with the ground-state density functional, a larger demagnetization than RBA is found; after we expand Ortenzi’s spin scaling method into an excited-state (laser) density functional, we find that the exchange splitting is indeed strongly reduced, as seen in the experiment. Both the majority and minority bands are shifted toward the Fermi level, but the majority shifts a lot more. The ultrafast reduction in exchange splitting occurs concomitantly with demagnetization. While our current theory is still unable to yield the same percentage loss in the spin moment as observed in the experiment, it predicts a correct trend that agrees with the experiments. With a better functional, we believe that our results can be further improved.

  3. Ultrafast reduction of exchange splitting in ferromagnetic nickel.

    PubMed

    Zhang, G P; Bai, Y H; George, Thomas F

    2016-06-15

    A decade ago Rhie et al (2003 Phys. Rev. Lett. 90 247201) reported that when ferromagnetic nickel is subject to an intense ultrashort laser pulse, its exchange splitting is reduced quickly. But to simulate such reduction remains a big challenge. The popular rigid band approximation (RBA), where both the band structure and the exchange splitting are held fixed before and after laser excitation, is unsuitable for this purpose, while the time-dependent density functional theory could be time-consuming. To overcome these difficulties, we propose a time-dependent Liouville and density functional theory (TDLDFT) that integrates the time-dependent Liouville equation into the density functional theory. As a result, the excited charge density is reiterated back into the Kohn-Sham equation, and the band structure is allowed to change dynamically. Even with the ground-state density functional, a larger demagnetization than RBA is found; after we expand Ortenzi's spin scaling method into an excited-state (laser) density functional, we find that the exchange splitting is indeed strongly reduced, as seen in the experiment. Both the majority and minority bands are shifted toward the Fermi level, but the majority shifts a lot more. The ultrafast reduction in exchange splitting occurs concomitantly with demagnetization. While our current theory is still unable to yield the same percentage loss in the spin moment as observed in the experiment, it predicts a correct trend that agrees with the experiments. With a better functional, we believe that our results can be further improved. PMID:27160931

  4. Reduce HIV Risk

    MedlinePlus

    ... incidence could be reduced if people changed their sexual behaviors. Our research has demonstrated remarkable success in reducing HIV risk-associated sexual behaviors among African American adolescents and adults." Spring 2008 ...

  5. Knowledge Exchange for Attention Deficit Hyperactivity Disorder Research: An Integrated Evidence and Knowledge Exchange Framework Leading to More Effective Research Dissemination Practices

    PubMed Central

    Levesque, Peter; Davidson, Simon; Kidder, Karen

    2007-01-01

    Introduction Knowledge Exchange refers to activities that help to create and support the conditions and culture that lead to the most effective access, implementation, utilization, and evaluation of the most credible evidence for improved mental health outcomes for children and youth in Ontario. Although knowledge exchange and associated concepts such as knowledge transfer and translation are increasingly well developed in other aspects of health and healthcare, it is underdeveloped in mental health generally. This paper introduces some of the basic concepts of knowledge exchange and calls for more development of knowledge exchange in the area of Attention Deficit Hyperactivity Disorder Research. Methods This is a discussion paper that presents a general overview of the Centre’s approach to knowledge exchange. It links the discussion to related concepts and to the need to overcome the research to practice gap. The Integrated Evidence and Knowledge Exchange Framework of the Provincial Centre of Excellence for Child and Youth Mental Health is introduced. Areas of active development in knowledge exchange are categorized into three objectives: context, content, and capacity. Results The use of an Integrated Evidence and Knowledge Exchange Framework for the Centre’s Grants and Awards program activities and evaluation has begun to explicitly and transparently link the evidence on effective knowledge exchange with the evidence on effective treatment for children and youth with mental health difficulties including ADHD. This framework is expected to produce greater transparency as well as improved attainment of outputs, outcomes, and impacts of these grants and awards in child and youth mental health. Conclusions Knowledge exchange activities may reduce the confusion for parents & care-givers, practitioners, researchers, and administrators, seeking the most credible data, information and knowledge about the most effective treatments for ADHD. An active process that

  6. Phosphonic acid based ion exchange resins

    DOEpatents

    Horwitz, E. Philip; Alexandratos, Spiro D.; Gatrone, Ralph C.; Chiarizia, Ronato

    1996-01-01

    An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene.

  7. Phosphonic acid based ion exchange resins

    DOEpatents

    Horwitz, E. Philip; Alexandratos, Spiro D.; Gatrone, Ralph C.; Chiarizia, Ronato

    1994-01-01

    An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene disphosphonic acid with styrene, acrylonitrile and divinylbenzene.

  8. The Kinetics of Isotopic Exchange Reactions.

    ERIC Educational Resources Information Center

    Logan, S. R.

    1990-01-01

    Discussed are the kinetic interactions of these chemical processes and the determination of the actual order of such reactions. Included are multiple exchange, catalytic exchange with deuterium, and depletion of the original substrate. (CW)

  9. Phosphonic acid based ion exchange resins

    DOEpatents

    Horwitz, E.P.; Alexandratos, S.D.; Gatrone, R.C.; Chiarizia, R.

    1994-01-25

    An ion exchange resin is described for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene. 9 figures.

  10. Phosphonic acid based ion exchange resins

    DOEpatents

    Horwitz, E.P.; Alexandratos, S.D.; Gatrone, R.C.; Chiarizia, R.

    1996-07-23

    An ion exchange resin is described for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene. 10 figs.

  11. Spin Exchange in Rydberg EIT

    NASA Astrophysics Data System (ADS)

    Nicholson, Travis; Thompson, Jeff; Liang, Qiyu; Cantu, Sergio; Venkatramani, Aditya; Pohl, Thomas; Choi, Soonwon; Lukin, Mikhail; Vuletic, Vladan

    2016-05-01

    The realization of strong optical nonlinearities between two photons has been a longstanding goal in quantum science. We achieve large single-photon-level nonlinearities with Rydberg EIT, which combines slow light techniques with strongly interacting Rydberg states. For two Rydberg atoms in the same state, a Van der Waals interaction is the dominant coupling mechanism. Inherently stronger dipole-dipole interactions are also possible between atoms in different Rydberg states. Using light storage and microwave resonances, we study the effect of dipole-dipole interactions in Rydberg EIT. We observe a coherent spin exchange effect for pairs of states dominated by dipole-dipole interactions. Spin exchange manifests as an increase in optical transmission through a cold Rubidium gas that is highly dissipative in the presence of Van der Waals interactions. We also observe a controlled π / 2 phase shift due to this effect, which paves the way for robust, universal all-optical quantum gates.

  12. The picture exchange communication system.

    PubMed

    Bondy, A S; Frost, L A

    1998-01-01

    The Picture Exchange Communication System (PECS) was developed as a means to teach children with autism and related developmental disabilities a rapidly acquired, self-initiating, functional communication system. Its theoretical roots combine principles from applied behavior analysis and guidelines established within the field of alternative and augmentative communication. This approach has several potential advantages relative to imitation-based strategies (both vocal and gestural) and symbol selection strategies. The system begins with the exchange of simple icons but rapidly builds "sentence" structure. The system also emphasizes developing the request function prior to developing responding to simple questions and commenting. The development of requesting with a sentence structure also permits the rapid development of attributes more traditionally taught within a receptive mode. The relationship between the introduction of PECS and various other behavioral issues (i.e., social approach and behavior management) as well as its relationship to the codevelopment of speech are reviewed. PMID:9857393

  13. Metabolic exchanges within tumor microenvironment.

    PubMed

    Chiarugi, Paola; Cirri, Paolo

    2016-09-28

    Tumor progression toward malignancy often requires a metabolic rewiring of cancer cells to meet changes in metabolic demand to forefront nutrient and oxygen withdrawal, together with strong anabolic requests to match high proliferation rate. Tumor microenvironment highly contributes to metabolic rewiring of cancer cells, fostering complete nutrient exploitation, favoring OXPHOS of lipids and glutamine at the expense of glycolysis and enhancing exchanges via extracellular microvesicles or exosomes of proteins, lipids and small RNAs among tumor and stromal cells. Noteworthy, the same molecular drivers of metabolic reprogramming within tumor and stroma are also able to elicit motility, survival and self-renewal on cancer cells, thereby sustaining successful escaping strategies to circumvent the hostile hypoxic, acidic and inflammatory environment. This review highlights the emerging role of nutrients and vesicle-mediated exchanges among tumor and stromal cells, defining their molecular pathways and offering new perspectives to develop treatments targeting this complex metabolic rewiring. PMID:26546872

  14. Heat exchanger and related methods

    SciTech Connect

    Turner, Terry D.; McKellar, Michael G.

    2015-12-22

    Heat exchangers include a housing having an inlet and an outlet and forming a portion of a transition chamber. A heating member may form another portion of the transition chamber. The heating member includes a first end having a first opening and a second end having a second opening larger than the first opening. Methods of conveying a fluid include supplying a first fluid into a transition chamber of a heat exchanger, supplying a second fluid into the transition chamber, and altering a state of a portion of the first fluid with the second fluid. Methods of sublimating solid particles include conveying a first fluid comprising a material in a solid state into a transition chamber, heating the material to a gaseous state by directing a second fluid through a heating member and mixing the first fluid and the second fluid.

  15. EXCHANGE

    SciTech Connect

    Boltz, J.C.

    1993-01-01

    This report contains the following news headlines: ADPE acquisition process made easy with SRP; scientific reference material available; ORPS WordPerfect macro setup procedure; system managed storage is here; LIBSPOOL for MVS mainframe end-users; training center course schedule for February 1993; enjoy NJOY; scientific user services staff decreased; new release of Forwarn, a static source code analysis tool for FORTRAN programs; out of the cold with HEAT; coping cells from one table to another in word perfect; used PC equipment pool; and video training.

  16. EXCHANGE

    SciTech Connect

    Boltz, J.C.

    1993-03-01

    This report discusses the following topics on computer environments: Releasing computer software outside EG G Idaho; Ilford digital photo imager; mandatory upgrade of PC ORPS software; ORPS host computer upgrade; EROB computer users see network change; password expiration notice; big iron still has place in HPC market; handy scripts to copy and move files; more on workstation password expiration; training center course schedule for April 1993; Microsoft Word Version 5.1a- button bar; file attributes can provide you greater flexibility; constructing a personal WordPerfect dictionary; and Windows shortcuts.

  17. Exchanging clinical knowledge via Internet.

    PubMed

    Buchan, I E; Hanka, R

    1997-11-01

    The need for effective and efficient exchange of clinical knowledge is increasing. Paper based methods for managing clinical knowledge are not meeting the demand for knowledge and this has undoubtedly contributed to the widely reported failures of clinical guidelines. Internet affords both opportunities and dangers for clinical knowledge. Systems such as Wax have demonstrated the importance of intuitive structure in the management of knowledge. We report on a new initiative for the global management of clinical knowledge. PMID:9506390

  18. Improved Ceramic for Heat Exchangers

    NASA Technical Reports Server (NTRS)

    Herbell, T. P.; Rauch, H. W.; Mccreeght, L. R.

    1982-01-01

    Most promising composition developed in investigation consisted of mixed oxides described generically as ZrMAS. Has been commercially designated as GE-7808. Material was obtained from low-cost clay/talc mixture. Overall assessment of ZrMAS indicates it is a viable candidate for heat-exchanger application in automotive gas-turbine engines and possibly other areas that require dielectric materials of moderate refractoriness, good corrosion resistance, and excellent thermal-shock resistance.

  19. Security message exchange interoperability scenarios

    SciTech Connect

    Tarman, Thomas

    1998-07-01

    This contribution describes three interoperability scenarios for the ATM Security Message Exchange (SME) protocol. These scenarios include network-wide signaling support for the Security Services Information Element, partial signaling support wherethe SSIE is only supported in private or workgroup ATM networks, and the case where the SSIE is nonsupported by any network elements (exceptthosethat implement security services). Explanatory text is proposed for inclusion infection 2.3 of the ATM Security Specification, Version 1.0.

  20. Heat exchanger demonstration expert system

    NASA Technical Reports Server (NTRS)

    Bagby, D. G.; Cormier, R. A.

    1988-01-01

    A real-time expert system intended for detecting and diagnosing faults in a 20 kW microwave transmitter heat exchanger is described. The expert system was developed on a LISP machine, Incorporated (LMI), Lambda Plus computer using Process Intelligent Control (PICON) software. The Heat Exhanger Expert System was tested and debugged. Future applications and extensions of the expert system to transmitters, masers, and antenna subassemblies are discussed.

  1. Heat exchanger demonstration expert system

    NASA Astrophysics Data System (ADS)

    Bagby, D. G.; Cormier, R. A.

    1988-05-01

    A real-time expert system intended for detecting and diagnosing faults in a 20 kW microwave transmitter heat exchanger is described. The expert system was developed on a LISP machine, Incorporated (LMI), Lambda Plus computer using Process Intelligent Control (PICON) software. The Heat Exhanger Expert System was tested and debugged. Future applications and extensions of the expert system to transmitters, masers, and antenna subassemblies are discussed.

  2. Electrically controlled cesium ion exchange

    SciTech Connect

    Lilga, M.

    1996-10-01

    Several sites within the DOE complex (Savannah River, Idaho, Oak Ridge and Hanford) have underground storage tanks containing high-level waste resulting from nuclear engineering activities. To facilitate final disposal of the tank waste, it is advantageous to separate and concentrate the radionuclides for final immobilization in a vitrified glass matrix. This task proposes a new approach for radionuclide separation by combining ion exchange (IX) and electrochemistry to provide a selective and economic separation method.

  3. SODIUM-WATER HEAT EXCHANGER

    DOEpatents

    Simmons, W.R.; Koch, L.J.

    1962-04-17

    A heat exchanger comprising a tank for hot liquid and a plurality of concentric, double tubes for cool liquid extending vertically through the tank is described. These tubes are bonded throughout most of their length but have an unbonded portion at both ends. The inner tubes extend between headers located above and below the tanmk and the outer tubes are welded into tube sheets forming the top and bottom of the tank at locations in the unbonded portions of the tubes. (AEC)

  4. Heat exchanger expert system logic

    NASA Technical Reports Server (NTRS)

    Cormier, R.

    1988-01-01

    The reduction is described of the operation and fault diagnostics of a Deep Space Network heat exchanger to a rule base by the application of propositional calculus to a set of logic statements. The value of this approach lies in the ease of converting the logic and subsequently implementing it on a computer as an expert system. The rule base was written in Process Intelligent Control software.

  5. Indeterminacy in foreign exchange markets

    NASA Astrophysics Data System (ADS)

    Pasquini, Michele; Serva, Maurizio

    2000-03-01

    We discuss price variations distributions in foreign exchange markets, characterizing them both in calendar and business time frameworks. The price dynamics is found to be the result of two distinct processes, a multi-variance diffusion and an error process. The presence of the latter, which dominates at short time scales, leads to indeterminacy principle in finance. Furthermore, dynamics does not allow for a scheme based on independent probability distributions, since volatility exhibits a strong correlation even at the shortest time scales.

  6. Test procedure for cation exchange chromatography

    SciTech Connect

    Cooper, T.D.

    1994-08-24

    The purpose of this test plan is to demonstrate the synthesis of inorganic antimonate ion exchangers and compare their performance against the standard organic cation exchangers. Of particular interest is the degradation rate of both inorganic and organic cation exchangers. This degradation rate will be tracked by determining the ion exchange capacity and thermal stability as a function of time, radiation dose, and chemical reaction.

  7. Reactive oxygen species production and discontinuous gas exchange in insects

    PubMed Central

    Boardman, Leigh; Terblanche, John S.; Hetz, Stefan K.; Marais, Elrike; Chown, Steven L.

    2012-01-01

    While biochemical mechanisms are typically used by animals to reduce oxidative damage, insects are suspected to employ a higher organizational level, discontinuous gas exchange mechanism to do so. Using a combination of real-time, flow-through respirometry and live-cell fluorescence microscopy, we show that spiracular control associated with the discontinuous gas exchange cycle (DGC) in Samia cynthia pupae is related to reactive oxygen species (ROS). Hyperoxia fails to increase mean ROS production, although minima are elevated above normoxic levels. Furthermore, a negative relationship between mean and mean ROS production indicates that higher ROS production is generally associated with lower . Our results, therefore, suggest a possible signalling role for ROS in DGC, rather than supporting the idea that DGC acts to reduce oxidative damage by regulating ROS production. PMID:21865257

  8. Understanding and mitigating heat exchanger fouling in bauxite refineries

    NASA Astrophysics Data System (ADS)

    Müller-Steinhagen, H.; Jamialahmadi, M.; Robson, B.

    1994-11-01

    Laboratory and plant measurements have been performed to evaluate possibilities of reducing the formation of desilication product (DSP) scale in the heat exchangers of the low-temperature Bayer process. It was found that the rate of scale formation is independent of the flow velocity, proportional to the square of the silica super saturation, and it increases exponentially with heat-transfer surface temperature. Because of the restricted operation conditions, variation of operating conditions may not reduce DSP formation sufficiently. Installation of turbulence promoters in the heat exchanger pipes had no beneficial aspects. Laboratory and plant measurements with a fluidized bed test heater indicated a strong potential of this technology to increase the operation times between chemical washes. Deposition of DSP could almost be eliminated if the process was modified such that developed subcooled boiling occurred at the heat-transfer surface.

  9. Reactive oxygen species production and discontinuous gas exchange in insects.

    PubMed

    Boardman, Leigh; Terblanche, John S; Hetz, Stefan K; Marais, Elrike; Chown, Steven L

    2012-03-01

    While biochemical mechanisms are typically used by animals to reduce oxidative damage, insects are suspected to employ a higher organizational level, discontinuous gas exchange mechanism to do so. Using a combination of real-time, flow-through respirometry and live-cell fluorescence microscopy, we show that spiracular control associated with the discontinuous gas exchange cycle (DGC) in Samia cynthia pupae is related to reactive oxygen species (ROS). Hyperoxia fails to increase mean ROS production, although minima are elevated above normoxic levels. Furthermore, a negative relationship between mean and mean ROS production indicates that higher ROS production is generally associated with lower . Our results, therefore, suggest a possible signalling role for ROS in DGC, rather than supporting the idea that DGC acts to reduce oxidative damage by regulating ROS production. PMID:21865257

  10. Oxidizer heat exchanger component test

    NASA Technical Reports Server (NTRS)

    Kanic, P. G.

    1988-01-01

    The RL10-IIB engine, is capable of multimode thrust operation. The engine operates at two low-thrust levels: tank head idle (THI), approximately 1 to 2 percent of full thrust; and pumped idle, 10 percent of full thrust. Operation at THI provides vehicle propellant settling thrust and efficient thermal conditioning; PI operation provides vehicle tank prepressurization and maneuver thrust for low-g deployment. Stable combustion of the RL10-IIB engine during the low-thrust operating modes can be accomplished by using a heat exchanger to supply gaseous oxygen to the propellant injector. The oxidized heat exchanger (OHE) vaporizes the liquid oxygen using hydrogen as the energy source. This report summarizes the test activity and post-test data analysis for two possible heat exchangers, each of which employs a completely different design philosophy. One design makes use of a low-heat transfer (PHT) approach in combination with a volume to attenuate pressure and flow oscillations. The test data showed that the LHT unit satisfied the oxygen exit quality of 0.95 or greater in both the THI and PI modes while maintaining stability. The HHT unit fulfilled all PI requirements; data for THI satisfactory operation is implied from experimental data that straddle the exact THI operating point.

  11. Characterization of the 70 kDa polypeptide of the Na/Ca exchanger.

    PubMed Central

    Saba, R I; Bollen, A; Herchuelz, A

    1999-01-01

    The Na/Ca exchanger is associated with 160, 120 and 70 kDa polypeptides whose nature is poorly understood. We have purified and characterized the Na/Ca exchanger from bovine cardiac sarcolemmal vesicles (SLVs) by using ion-exchange and affinity chromatographies. The Na/Ca exchanger-enriched fraction was reconstituted into asolectin liposomes [lipid to protein ratio 10:1 (w/w)] that showed Na/Ca exchange activity. Under non-reducing conditions, SDS/PAGE showed a single 70 kDa polypeptide, which was further characterized by immunoblots with different antibodies: SWant, raised against the purified exchanger protein; NH2-terminus, residues 1-21; NCX1, residues 393-406; and Exon F, residues 622-644. Immunoblots under reducing conditions with SWant, NH2-terminus and NCX1 showed three bands migrating at 160, 120 and 70 kDa for SLV preparations, whereas Exon F reacted only with the 160 and 120 kDa bands. Under non-reducing conditions, immunoblots with purified reconstituted Na/Ca exchanger showed a single band at 70 kDa reacting with SWant, NH2-terminus and NCX1 but not with Exon F. We conclude that the 70 kDa protein is associated with Na/Ca exchange activity, has the same N-terminal sequence as the cloned bovine cardiac exchanger, and has its length decreased by at least 35% from its C-terminal portion as compared with that of the wild-type exchanger. PMID:9931309

  12. High Temperature Thermosetting Polyimide Nanocomposites Prepared with Reduced Charge Organoclay

    NASA Technical Reports Server (NTRS)

    Campbell, Sandi; Liang, Margaret I.

    2005-01-01

    The naturally occurring sodium and calcium cations found in bentonite clay galleries were exchanged with lithium cations. Following the cation exchange, a series of reduced charge clays were prepared by heat treatment of the lithium bentonite at 130 C, 150 C, or 170 C. Inductively coupled plasma (ICP) analysis showed that heating the lithium clay at elevated temperatures reduced its cation exchange capacity. Ion exchange of heat-treated clays with either a protonated alkyl amine or a protonated aromatic diamine resulted in decreasing amounts of the organic modifier incorporated into the lithium clay. The level of silicate dispersion in a thermosetting polyimide matrix was dependent upon the temperature of Li-clay heat treatment as well as the organic modification. In general, clays treated at 150 C or 170 C, and exchanged with protonated octadcylamine or protonated 2,2'-dimethlybenzidine (DMBZ) showed a higher degree of dispersion than clays treated at 130 C, or exchanged with protonated dodecylamine. Dynamic mechanical analysis showed little change in the storage modulus or T(sub g) of the nanocomposites compared to the base resin. However, long term isothermal aging of the samples showed a significant decrease in the resin oxidative weight loss. Nanocomposite samples aged in air for 1000 hours at 288 C showed of to a decrease in weight loss compared to that of the base resin. This again was dependent on the temperature at which the Li-clay was heated and the choice of organic modification.

  13. 25 CFR 151.6 - Exchanges.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Exchanges. 151.6 Section 151.6 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER LAND ACQUISITIONS § 151.6 Exchanges. An individual Indian or tribe may acquire land in trust status by exchange if the acquisition comes within the terms...

  14. Pharmaceutical Applications of Ion-Exchange Resins

    ERIC Educational Resources Information Center

    Elder, David

    2005-01-01

    The historical uses of ion-exchanged resins and a summary of the basic chemical principles involved in the ion-exchanged process are discussed. Specific applications of ion-exchange are provided that include drug stabilization, pharmaceutical excipients, taste-masking agents, oral sustained-release products, topical products for local application…

  15. A theological perspective on social exchange theory.

    PubMed

    Hill, E W

    1992-06-01

    This article provides a brief review of the basic principles of social exchange theory with an emphasis on a social exchange model of conflict. The key concepts of justice, reciprocity, and equity comprised in social exchange theory are addressed from a social and theological perspective. PMID:24272881

  16. Neighbourhood Book Exchanges: Localising Information Practices

    ERIC Educational Resources Information Center

    Webster, Tenny; Gollner, Kathleen; Nathan, Lisa

    2015-01-01

    Introduction: Through this paper we report on an exploratory study into the design and use of neighbourhood book exchanges in North America. We identify dominant media framings of these book exchanges in North America, along with claims made concerning the influence of the exchanges. We compare the media claims with insights from interviews with…

  17. Trust and Transitions in Modes of Exchange

    ERIC Educational Resources Information Center

    Cheshire, Coye; Gerbasi, Alexandra; Cook, Karen S.

    2010-01-01

    In this study, we investigate the relationship between uncertainty and trust in exogenous shifts in modes of social exchange (i.e., those that are not initiated by the individuals in a given exchange system). We explore how transitions from a high uncertainty environment (reciprocal exchange) to lower-uncertainty environments (nonbinding or…

  18. Cryogenic Heat Exchanger with Turbulent Flows

    ERIC Educational Resources Information Center

    Amrit, Jay; Douay, Christelle; Dubois, Francis; Defresne, Gerard

    2012-01-01

    An evaporator-type cryogenic heat exchanger is designed and built for introducing fluid-solid heat exchange phenomena to undergraduates in a practical and efficient way. The heat exchanger functions at liquid nitrogen temperature and enables cooling of N[subscript 2] and He gases from room temperatures. We present first the experimental results of…

  19. Wright State University International Student Exchange Program.

    ERIC Educational Resources Information Center

    Nixon, Harold L.

    The Wright State University International Student Exchange Program is described. This school's approach to student exchange programs immerses students in the daily life of countries in Asia and South America at minimal cost to the participating institutions. Through exchange agreements with universities in Japan, Brazil, and China, students get 4…

  20. A fuel-oil matrix heat exchanger

    NASA Astrophysics Data System (ADS)

    Mikulin, E. I.; Shevich, Iu. A.; Potapov, V. N.; Veselov, V. A.; Saltais, E. A.; Glukhovskii, G. I.

    A novel design of a welded matrix heat exchanger capable of handling high-pressure liquid and gas coolants is described. Results of tests conducted on matrix heat exchangers and their models are presented, and formulas are recommended for calculating the heat transfer and hydraulic resistance characteristics. A comparison of the characteristics of matrix and tube heat exchangers demonstrates the advantages of the former.