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Sample records for reduced intergranular exchange

  1. Intergranular exchange coupling

    NASA Astrophysics Data System (ADS)

    Muller, M. W.; Indeck, R. S.

    1994-02-01

    We evaluate the exchange interaction between neighboring grains of a polycrystalline magnetic material with uniaxial magnetocrystalline anisotropy, based on the energy of the domain wall formed at the portion of the interface in atomic contact. The analysis suggests that previous work [J.-G. Zhu and H. N. Bertram, in Solid State Physics Vol. 46, edited by H. Ehrenreich and T. Turnbull (Academic, San Diego, 1992)] may underestimate the interaction, and it predicts a different dependence on grain size.

  2. FePt : Al2O3 nanocomposite thin films synthesized by magnetic trapping assisted pulsed laser deposition with reduced intergranular exchange coupling

    NASA Astrophysics Data System (ADS)

    Lin, J. J.; Pan, Z. Y.; Karamat, S.; Mahmood, S.; Lee, P.; Tan, T. L.; Springham, S. V.; Rawat, R. S.

    2008-05-01

    FePt : Al2O3 nanocomposite thin films synthesized by magnetic trapping (MT) assisted pulsed laser deposition (PLD) were found to have lower transition temperature for L10 face-centred-tetragonal (fct) phase due to higher concentration of defects. The low phase transition temperature together with non-magnetic matrix materials helps to reduce grain growth and agglomeration during annealing. Small remanence ratio and coercive squareness for nanocomposite thin films annealed at 300 °C to fct phase confirm that the main intergranular interaction is magnetostatic interaction rather than exchange coupling. The MT assisted PLD can synthesize fct-FePt : Al2O3 nanocomposite thin films with reduced intergranular exchange coupling.

  3. Intergranular Exchange in Magnetic Nanostructures

    NASA Astrophysics Data System (ADS)

    Skomski, Ralph

    2005-03-01

    Exchange interactions determine not only atomic-scale properties such as the Curie temperature but are also paramount to the realization of mesoscopic magnetism. Nanoscale exchange reflect the relativistic origin of magnetism. On an atomic scale, interatomic exchange tends to be much stronger than magnetic interactions, but the quadratic wave-vector dependence of the exchange energy makes magnetic interactions competitive on a nanoscale. The corresponding characteristic length scale is ao/α = 7.252 nm, where ao is the Bohr radius and α = 1/137 is Sommerfeld's fine structure constant. In homogeneous solids, the competing relativistic and nonrelativistic interactions determine, for example, the thickness of domain walls. In nanostructures, the situation is more complex, because mesoscopic and atomic exchange effects interfere with structural length scales. This is important in many areas of magnetism, such as permanent magnetism, soft magnetism, spin electronics, and magnetic recording. (For a recent review, see Skomski, J. Phys. CM, vol. 15, 2003, p. R841.) From an atomic point of view, local magnetic moments embedded in an itinerant electron gas are coupled by RKKY-type interactions, whose oscillatory period is determined by the Fermi wave vector kF. First, RKKY interaction between embedded clusters or particles do not average to zero but actually increase with particle size. Second, the low carrier densities of semimetals and semiconductors yield small Fermi wave vectors and nanoscale oscillation periodicities. From a mesoscopic point of view, traditional random-anisotropy scaling amounts to a dimensionless coupling constant A/K1R^2, but this expression fails to account for important real-structure features. For example, grain boundaries with reduced interatomic exchange give rise to a quasi-discontinuity of the magnetization, create a magnetization perturbation that extends far into the bulk, and modify scaling relations for the coercivity and other quantities

  4. Manifestation of higher-order inter-granular exchange in magnetic recording media

    NASA Astrophysics Data System (ADS)

    Ellis, Matthew O. A.; Ababei, Razvan-V.; Wood, Roger; Evans, Richard F. L.; Chantrell, Roy W.

    2017-08-01

    Exchange coupling between magnetic grains is essential for maintaining the stability of stored information in magnetic recording media. Using an atomistic spin model, we have investigated the coupling between neighbouring magnetic grains where magnetic impurity atoms have migrated into the non-magnetic grain boundary. We find that when the impurity density is low, a biquadratic term in addition to the bilinear term is found to better describe the inter-granular exchange coupling. The temperature dependence of both terms is found to follow a power law behaviour with the biquadratic exchange constant decaying faster than the bilinear. For the increasing grain boundary thickness, the inter-granular exchange reduces and also decays more quickly with temperature. Further simulations of a grain at a bit boundary show an unexpected energy minimum for in-plane magnetisation. This feature is reproduced if the biquadratic exchange term is included.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Effects of neutron irradiation on hydrogen-induced intergranular fracture in a low activation 9%Cr-2%W steel

    NASA Astrophysics Data System (ADS)

    Kimura, A.; Kayano, H.; Narui, M.

    1991-03-01

    Hydrogen charging changed the fracture mode in tensile tests at room temperature from ductile shear rupture to intergranular cracking, resulting in a considerable reduction of the ductility of a low activation 9%Cr-2%W martensitic steel. The critical hydrogen charging current density required to cause hydrogen-induced intergranular cracking was reduced by neutron irradiation, suggesting that neutron irradiation enhanced hydrogen-induced intergranular cracking. This hydrogen-induced intergranular cracking was not caused by irreversible damage due to hydrogen charging, since it disappeared after aging at room temperature. The recovery rate of the fracture mode from intergranular cracking to ductile rupture during aging at room temperature was reduced by irradiation. A mechanism of irradiation-induced enhancement of hydrogen embrittlement in a low activation 9%Cr-2%W martensitic steel is proposed.

  11. 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.

  12. On the Origin of Intergranular Jets

    NASA Astrophysics Data System (ADS)

    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 Hα 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 Hα images collected through a Zeiss Lyot filter with a passband of 0.025 nm.

  13. Some stochastic aspects of intergranular creep cavitation

    SciTech Connect

    Fariborz, S.J.; Farris, J.P.; Harlow, D.G.; Delph, T.J.

    1987-10-01

    We present some results obtained from a simplified stochastic model of intergranular creep cavitation. The probabilistic features of the model arise from the inclusion of random cavity placement on the grain boundary and time-discrete stochastic cavity nucleation. Among the predictions of the model are Weibull-distributed creep rupture failure times and a Weibull distribution of cavity radii. Both of these predictions have qualitative experimental support. 18 refs., 7 figs.

  14. 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.

  15. Laser Peening of Alloy 600 to Improve Intergranular Stress Corrosion Cracking Resistance in Power Plants

    SciTech Connect

    Chen, H; Rankin, J; Hackel, L; Frederick, G; Hickling, J; Findlan, S

    2004-04-20

    Laser peening is an emerging modern process that impresses a compressive stress into the surface of metals or alloys. This treatment can reduce the rate of intergranular stress corrosion cracking and fatigue cracking in structural metals or Alloy 600 needed for nuclear power plants.

  16. Effects of carbon on intergranular fracture of iron

    SciTech Connect

    Shin, K.S.; Meshii, M.

    1984-01-01

    The effect of carbon on the grain boundary strength of iron which had been already reduced by sulfur segregation was investigated by a slow strain-rate tensile test at 77/sup 0/K. The amounts of sulfur and carbon segregation at grain boundaries were controlled by carbon contents and heat treatments of specimens and were determined by Auger electron spectroscopy after in-situ fracture under ultra-high vacuum. It was found that the primary effect of carbon is to displace sulfur from grain boundaries and thus to improve the grain boundary strength by reducing the embrittling effect of sulfur. The second effect of carbon is to increase the resistance to dislocation motion and thus to increase the apparent stress for intergranular fracture.

  17. Role of Intergranular Films in Toughened Ceramics

    SciTech Connect

    Becher, P.F.; Hsueh, C.H.; More, K.L.; Painter, G.S.; Sun, E.Y.

    1999-05-10

    Self-reinforced silicon nitride ceramics rely the generation of elongated grains that act as reinforcing elements to gain increases in fracture toughness. However, the size and number of the reinforcing grains must be controlled, along with the matrix grain size, to optimize the fracture toughness and strength. Furthermore, the toughening processes of crack bridging are dependent upon retention of these reinforcing grains during crack extension by an interfacial debonding process. Both the debonding process and the resultant toughening effects are found to be influenced by the composition of the sintering aids which typical are incorporated into the amorphous intergranular films found in these ceramics. Specifically, it is shown that the interface between the intergranular glass and the reinforcing grains is strengthened in the presence of an epitaxial SiAlON layer. In addition, the interface strength increases with the Al and 0 content of the SiAlON layer. Micromechanics modeling indicates that stresses associated with thermal expansion mismatch are a secondary factor in interfacial debonding in these specific systems. On the other hand, first principles atomic cluster calculations reveal that the debonding behavior is consistent with the formation of strong Si-0 and Al-O bonds across the glass-crystalline interface.

  18. Magnetic Field Twisting by Intergranular Downdrafts

    NASA Astrophysics Data System (ADS)

    Taroyan, Youra; Williams, Thomas

    2016-10-01

    The interaction of an intergranular downdraft with an embedded vertical magnetic field is examined. It is demonstrated that the downdraft may couple to small magnetic twists leading to an instability. The descending plasma exponentially amplifies the magnetic twists when it decelerates with depth due to increasing density. Most efficient amplification is found in the vicinity of the level, where the kinetic energy density of the downdraft reaches equipartition with the magnetic energy density. Continual extraction of energy from the decelerating plasma and growth in the total azimuthal energy occurs as a consequence of the wave-flow coupling along the downdraft. The presented mechanism may drive vortices and torsional motions that have been detected between granules and in simulations of magnetoconvection.

  19. 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.

  20. Influence of local stress and strain on intergranular cracking of 316L stainless steel in supercritical water

    NASA Astrophysics Data System (ADS)

    West, Elaine Ann

    The objective of this study was to determine how the deformation propensities of individual grains of 316L stainless steel influence intergranular cracking behavior in supercritical water (SCW). The grain-to-grain variations in deformation propensities were estimated from the Schmid and Taylor factors of grains. Resulting stress inhomogeneities and strain incompatibilities which were evaluated to determine the conditions that promoted intergranular cracking in SCW. Proton irradiation of 316L caused hardening and radiation induced depletion of chromium at grain boundaries and was found to increase intergranular cracking severity. The SCW environment increased the crack density on the gage surfaces of the specimen by a factor of 18 compared to a 400°C argon environment. Intergranular cracks preferentially occurred along grain boundaries oriented perpendicular to the tensile axis and adjacent to grains with low Schmid factors. The Schmid-Modified Grain Boundary Stress (SMGBS) model was developed to analyze local grain boundary stresses. The model was validated by showing that the Schmid factor dependence of cracking in SCW could be predicted from the trace inclination distribution, and confirmed that cracking was driven by the normal stresses acting on grain boundaries. The similar dependencies of slip discontinuity and intergranular cracking on trace inclination, Schmid factor, Taylor factor, and grain boundary character suggest that slip discontinuity contributes to intergranular cracking. Grains with low Taylor factors decreased slip discontinuity propensity at grain boundaries with trace inclinations >50° because they provided multiple favorably oriented slip systems on which deformation could occur. Grain boundary engineering reduced the intergranular cracking propensity of 316L stainless steel in SCW by virtue of the fact that special grain boundaries were more resistant to intergranular cracking in SCW than random high angle grain boundaries. The findings of

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. The effect of sintering temperature on the intergranular properties of Bi2223 superconductors

    NASA Astrophysics Data System (ADS)

    Kameli, P.; Salamati, H.; Eslami, M.

    2006-01-01

    A systematic study of the intergranular properties of (Bi,Pb) 2Sr 2Ca 2Cu 3O y (Bi2223) polycrystalline samples has been done using the electrical resistivity and Ac susceptibility techniques. In this project, we have prepared a series of Bi2223 samples with different sintering temperature. The XRD results show that by increasing sintering temperature up to 865 °C the Bi2212 phase fraction decrease. It was found that the Bi2212 phase on the grain boundaries is likely to play the role of weak links and consequently reduces the intergranular critical current densities. Analysis of the temperature dependence of the Ac susceptibility near the transition temperature ( Tc) has been done employing Bean's Critical State Model. The observed variation of intergranular critical current densities ( Jc) with temperature indicates that the weak links are changed from superconductor-normal metal-superconductor (SNS) for well-coupled sample to superconductor-insulator-superconductor (SIS) type of junctions for the sample with high Bi2212 phase fraction.

  7. 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.

  8. Mechanism of Intergranular Penetration of Ga in an Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Ding, Boxiong; Hoagland, Richard

    1998-03-01

    The intergranular penetration rates of gallium in 7050-T74 aluminum alloy were examined at temperatures from 25C to 180C under stress free condition. The results provide an estimate of activation energy of the penetration process. The penetration of Ga is observed to occur along the grain boundary and also spread over the surface, but much more slowly. Experiments were also performed at 23C involving solid Ga. These results together with mechanism controlling the intergranular penetration of Ga in Al will be discussed. This work was supported by DARPA.

  9. Intergranular Properties of Zr-SUBSTITUTED Y123 Compounds

    NASA Astrophysics Data System (ADS)

    Sbârciog, C.; Redac, R. T.; Gr. Deac, I.; Pop, I.

    AC susceptibility measurements have been done to determine the intergranular properties for some 123-superconducting ceramics. From the imaginary part of the complex susceptibility, χ″(T), the temperature dependence of the critical current density was determined by using Bean's model. The intergranular current density was experimentally determined from AC susceptibility data by varying the field amplitude. All intragrain critical parameters are gradually degraded with increasing the concentration of the dopant substituting on the rare-earth side and with decreasing the sintering temperature during the sample preparation.

  10. Dual capillary tube / heat exchanger in combination with cycle priming for reducing charge migration

    DOEpatents

    Gomes, Alberto Regio; Kuehl, Steven J.; Litch, Andrew D.; Wu, Guolian

    2017-07-04

    A refrigerator appliance including a multi-capacity compressor and a refrigerant circuit with two conduits and pressure reducing devices arranged in parallel between an evaporator and a condenser. Refrigerant can flow through one, both or none of the conduits and pressure reducing devices. The appliance also has a heat exchanger in contact with either one pressure reducing device, or one conduit between the pressure reducing device and the valve system. The appliance also includes a controller for priming the compressor above a nominal capacity for a predetermined or calculated duration at the beginning of an ON-cycle.

  11. Computer Simulation of Intergranular Stress Corrosion Cracking via Hydrogen Embrittlement

    SciTech Connect

    Smith, R.W.

    2000-04-01

    Computer simulation has been applied to the investigation of intergranular stress corrosion cracking in Ni-based alloys based on a hydrogen embrittlement mechanism. The simulation employs computational modules that address (a) transport and reactions of aqueous species giving rise to hydrogen generation at the liquid-metal interface, (b) solid state transport of hydrogen via intergranular and transgranular diffusion pathways, and (c) fracture due to the embrittlement of metallic bonds by hydrogen. A key focus of the computational model development has been the role of materials microstructure (precipitate particles and grain boundaries) on hydrogen transport and embrittlement. Simulation results reveal that intergranular fracture is enhanced as grain boundaries are weakened and that microstructures with grains elongated perpendicular to the stress axis are more susceptible to cracking. The presence of intergranular precipitates may be expected to either enhance or impede cracking depending on the relative distribution of hydrogen between the grain boundaries and the precipitate-matrix interfaces. Calculations of hydrogen outgassing and in gassing demonstrate a strong effect of charging method on the fracture behavior.

  12. 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.

  13. Reducing distortion and internal forces in truss structures by member exchanges

    NASA Technical Reports Server (NTRS)

    Greene, William H.; Haftka, Raphael T.

    1989-01-01

    Manufacturing errors in the length of members or joint diameters of large truss reflector backup structures may result in unacceptable large distortion errors or member forces. However, it may be possible to accurately measure these length or diameter errors. The present work suggests that a member and joint placement strategy may be used to reduce distortion errors and internal member forces. A member and joint exchange algorithm is used to demonstrate the potential of this approach on several 102-member and 660-member truss reflector structures. It is shown that it is possible to simultaneously reduce the rms of the surface error and the rms of member forces by two orders of magnitude by member and joint exchanges.

  14. Multistep Galvanic Exchange Synthesis Yielding Fully Reduced Pt Dendrimer-Encapsulated Nanoparticles

    PubMed Central

    2015-01-01

    Here we outline a new method for synthesizing fully reduced Pt dendrimer-encapsulated nanoparticles (DENs). This is achieved by first synthesizing Cu DENs of the appropriate size through sequential dendrimer loading and reduction steps, and then galvanically exchanging the zerovalent Cu DENs for Pt. The properties of Pt DENs having an average of 55, 140, and 225 atoms prepared by direct chemical reduction and by galvanic exchange are compared. Data obtained by UV–vis spectroscopy, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and high-resolution electron microscopy confirm only the presence of fully reduced Pt DENs when synthesized by galvanic exchange, while chemical reduction leads to a mixture of reduced DENs and unreduced precursor. These results are significant because Pt DENs are good models for developing a better understanding of the effects of finite size on catalytic reactions. Until now, however, the results of such studies have been complicated by a heterogeneous mixture of Pt catalysts. PMID:25456853

  15. Fast Reversed-Phase Liquid Chromatography to Reduce Back Exchange and Increase Throughput in H/D Exchange Monitored by FT-ICR Mass Spectrometry

    PubMed Central

    Zhang, Hui-Min; Bou-Assaf, George M.; Emmett, Mark R.; Marshall, Alan G.

    2009-01-01

    In solution-phase hydrogen/deuterium exchange (HDX), it is essential to minimize the back exchange level of H for D after the exchange has been quenched, to accurately assign protein conformation and protein-protein or protein-ligand interactions. Reversed-phase HPLC is conducted at low pH and low temperature to desalt and separate proteolytic fragments. However, back exchange averages ∼30% due to long exposure to H2O in the mobile phase. In this paper, we first show that there is no significant backbone amide hydrogen back exchange during quenching and digestion; backbone exchange occurs primarily during subsequent LC separation. We then show that a rapid reversed-phase separation reduces back exchange for HDX by at least 25%, due to dramatically reduced retention time of the peptide fragments on the column. The influence of retention time on back exchange was also evaluated. The rapid separation coupled with high resolution FT-ICR MS at 14.5T provides high amino acid sequence coverage, high sample throughput, and high reproducibility and reliability. PMID:19095461

  16. Kinetic evaluation of intergranular fracture in austenitic stainless steels

    SciTech Connect

    Simonen, E.P.; Bruemmer, S.M.

    1995-12-31

    A second, higher-dose threshold exists for irradiation-assisted stress corrosion cracking (IASCC) of austenitic stainless steels in non-oxidizing environments. The data supporting this concept have stimulated interest in the mechanical aspects of intergranular (IG) fracture. Cracking in a non-oxidizing environment suggests that mechanically-induced IG fracture may play an important role in the IASCC mechanism under these conditions. Radiation alters deformation processes in austenitic alloys and may influence the fracture mode during either in-situ or post-irradiation straining. Radiation effects that must be considered include radiation strengthening, radiation creep and radiation-induced flow localization. The present evaluation relates these radiation-induced phenomena to IG fracture relevant to IASCC. The evaluation indicates that radiation strengthening retards matrix deformation and allows intergranular fracture to occur at higher stresses and lower temperatures than expected for unirradiated stainless steel.

  17. Grain boundary engineering for intergranular fracture and creep resistance

    SciTech Connect

    Palumbo, G.; Lehockey, E.M.; Lin, P.

    1996-12-31

    The effect of special grain boundary frequency on the bulk creep performance of 99.99% Ni at 84 MPa and 450{degrees}C (grain boundary sliding regime). Increasing the frequency of `special` grain boundaries (by thermomechanical processing) from 13% to 66% results in a 16-fold reduction in steady state creep rate and a 6-fold reduction in primary creep strain. Consistent with the previous intergranular fracture analysis, a moderate increase in special boundary frequency from 13% to 45% yields the greatest reduction in the creep strain parameters. Microstructural evaluation of the specimens following testing to 1.8% total strain showed that (1) cavitation had occurred exclusively at general grain boundaries (i.e., {Sigma}>29) and (2) no cavities were formed in the material containing 66% special grain boundaries. The results of this study provide considerable promise for a `grain boundary engineering` approach towards the mitigation of intergranular-creep and -fracture in practical engineering materials.

  18. Tailoring the intergranular phases in silicon nitride for improved toughness

    SciTech Connect

    Sun, E.Y.; Becher, P.F.; Plucknett, K.P.; Waters, S.B.; Hirao, K.; Brito, M.E.

    1996-12-31

    Intergranular glass phases can have a significant influence on fracture resistance (R-curve behavior) of Si nitride ceramics and appears to be related to debonding of the {beta}-Si{sub 3}N{sub 4}/oxynitride-glass interfaces. Applying the results from {beta}- Si{sub 3}N{sub 4}-whisker/oxynitride-glass model systems, self- reinforced Si nitrides with different sintering additive ratios were investigated. Si nitrides sintered with a lower Al{sub 2}O{sub 3}: Y{sub 2}O{sub 3} additive ratio exhibited higher stead-state fracture toughness together with a steeply rising R-curve. Analytical electron microscopy suggested that the different fracture behavior is related to the Al content in the SiAlON growth band on the elongated grains, which could result in differences in interfacial bonding structures between the grains and the intergranular glass.

  19. 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.

  20. 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

  1. 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.

  2. Intergranular strain evolution near fatigue crack tips in polycrystalline metals

    NASA Astrophysics Data System (ADS)

    Zheng, L. L.; Gao, Y. F.; Lee, S. Y.; Barabash, R. I.; Lee, J. H.; Liaw, P. K.

    2011-11-01

    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.

  3. Study of the large reduced density gradient limit for the exchange energy

    NASA Astrophysics Data System (ADS)

    Gazquez, Jose; Carmona-Espindola, Javier; Vela, Alberto; Trickey, Sam

    The generalized gradient approximation (GGA) for the Kohn-Sham exchange-correlation functional has become widely used in electronic structure calculations of small, medium and large systems, because it provides rather reasonable results with moderate computational effort. Usually the GGA for exchange (X) is expressed in terms of an analytical expression of the X enhancement function, Fx(s), where s is the reduced density gradient. When a non-empirical approach based on constraint satisfaction is followed, the analytical expression of Fx(s) is the result of interpolating between the small- and large-s limits. However, neither of those limits is uniquely defined. In both cases there are several possibilities. The present work is a study of the influence of the several large-s limit possibilities upon the calculation of properties that depend on energy differences, versus those that depend on response functions, and excitation energies.

  4. 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

  5. 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

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

    SciTech Connect

    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 was 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

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

    SciTech Connect

    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 was 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

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

    DOE PAGES

    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

  9. 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.

  10. Pt nanoparticle-reduced graphene oxide nanohybrid for proton exchange membrane fuel cells.

    PubMed

    Park, Dae-Hwan; Jeon, Yukwon; Ok, Jinhee; Park, Jooil; Yoon, Seong-Ho; Choy, Jin-Ho; Shul, Yong-Gun

    2012-07-01

    A platinum nanoparticle-reduced graphene oxide (Pt-RGO) nanohybrid for proton exchange membrane fuel cell (PEMFC) application was successfully prepared. The Pt nanoparticles (Pt NPs) were deposited onto chemically converted graphene nanosheets via ethylene glycol (EG) reduction. According to the powder X-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) analysis, the face-centered cubic Pt NPs (3-5 nm in diameter) were homogeneously dispersed on the RGO nanosheets. The electrochemically active surface area and PEMFC power density of the Pt-RGO nanohybrid were determined to be 33.26 m2/g and 480 mW/cm2 (maximum values), respectively, at 75 degrees C and at a relative humidity (RH) of 100% in a single-cell test experiment.

  11. Ethanolamine requirement of mammary epithelial cells is due to reduced activity of base exchange enzyme

    SciTech Connect

    Kano-Sueoka, T.; King, D.M.

    1987-05-01

    Epithelial cells and some of their transformed derivatives require ethanolamine (Etn) to proliferate normally in defined culture medium. The amount of cellular phosphatidylethanolamine (PtdEtn) is considerably reduced when these cells are cultured without Etn. Using Etn-responsive and -nonresponsive rat mammary carcinoma cell lines, the biochemical mechanism of Etn-responsiveness of investigated. The incorporation of (/sup 3/H)serine into phosphatidylserine (PtdSer) and PtdEtn in Etn-responsive cells was 60 and 37%, respectively, of those in Etn-nonresponsive cells. There was no significant difference between the two cell types in the activities of enzymes involved in PtdEtn synthesis via CDP-Etn. The activity of PtdSer decarboxylase was also very similar in these two cell types. When these cells were cultured in the presence of (/sup 32/P)PtdEtn, the rate of accumulation of (/sup 32/P)-labeled PtdSer from the radioactive PtdEtn was considerably reduced in Etn-responsive cells as compared to Etn-nonresponsive cells. Whereas there was no significant difference in the accumulation of the labeled PtdSer from (/sup 32/P)phosphatidylcholine. These results demonstrate that the Etn-responsiveness is due to a limited ability to synthesize PtdSer resulting from a limited base exchange activity utilizing PtdEtn.

  12. 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

  13. Mesoscale modeling of intergranular bubble percolation in nuclear fuels

    SciTech Connect

    Millett, Paul C.; Tonks, Michael; Biner, S. B.

    2012-04-15

    Phase-field simulations are used to examine the variability of intergranular fission gas bubble growth and percolation on uranium dioxide grain boundaries on a mesoscopic length scale. Three key parameters are systematically varied in this study: the contact angle (or dihedral angle) defining the bubble shape, the initial bubble density on the grain boundary plane, and the ratio of the gas diffusivity on the grain boundary versus the grain interiors. The simulation results agree well with previous experimental data obtained for bubble densities and average bubble areas during coalescence events. Interestingly, the rate of percolation is found to be highly variable, with a large dependency on the contact angle and the initial bubble density and little-to-no dependency on the grain boundary gas diffusivity.

  14. MESOSCALE MODELING OF INTERGRANULAR BUBBLE PERCOLATION IN NUCLEAR FUELS

    SciTech Connect

    Paul C. Millett; Michael Tonks; S. B. Biner

    2012-04-01

    Phase-field simulations are used to examine the variability of intergranular fission gas bubble growth and percolation on uranium dioxide grain boundaries on a mesoscopic length scale. Three key parameters are systematically varied in this study: the contact angle (or dihedral angle) defining the bubble shape, the initial bubble density on the grain boundary plane, and the ratio of the gas diffusivity on the grain boundary versus the grain interiors. The simulation results agree well with previous experimental data obtained for bubble densities and average bubble areas during coalescence events. Interestingly, the rate of percolation is found to be highly variable, with a large dependency on the contact angle and the initial bubble density, and little-to-no dependency on the grain boundary gas diffusivity.

  15. 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.

  16. 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.

  17. Boric acid application guidelines for intergranular corrosion inhibition: Topical report

    SciTech Connect

    Hermer, R.E.

    1987-12-01

    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 via crevice flushing, low power soaks, on-line, or using 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 how it should be correctly applied. The data on these subjects may be found in a diversity of sources, which are often not readily available or convenient to use. This document has been prepared to be a comprehensive treatise on boric acid relevant to its application in nuclear steam generators. 49 refs., 31 figs., 16 tabs.

  18. Wood Xylowall: New process to reduce water exchange by an intra-graft of polymer

    NASA Astrophysics Data System (ADS)

    Uyttenhove, Anne; Tilquin, Bernard

    2005-07-01

    Our research shows that poplar treated with selected monomer mixture and then irradiated at 50 kGy reduces the water exchange without adversely altering the desirable qualities of wood. Moreover, the environment is not polluted. To retard changes in moisture content and dimensions, different commercial Radcures (UCB) were tested. A comparative study on the water retention showed significant reduction between non-treated and Xylowall wood for the species: poplar. The physical and mechanical measurements (density, volumetric shrinkage, elasticity, rupture, impact bending, hardness, compression strength) on poplar and pine show that the properties of the wood are not affected negatively by Xylowall treatment with irradiation. Moreover, the process does not discharge any toxic volatile residues into the atmosphere as proven by GC-MS trace analysis of heated wood samples. The stereomicroscope by imagery reveals an impregnation of 0.5 mm on cross-section of darker-stained areas, and sometimes more due to the texture (the relative size and arrangement of the wood cells) of the wood.

  19. Extracellular Na+ inhibits Na+/H+ exchange: cell shrinkage reduces the inhibition.

    PubMed

    Dunham, Philip B; Kelley, Scott J; Logue, Paul J

    2004-08-01

    Na+/H+ exchangers (NHE) are ubiquitous transporters participating in regulation of cell volume and pH. Cell shrinkage, acidification, and growth factors activate NHE by increasing its sensitivity to intracellular H+ concentration. In this study, the kinetics were studied in dog red blood cells of Na+ influx through NHE as a function of external Na+ concentration ([Na+](o)). In cells in isotonic media, [Na+](o) inhibited Na+ influx >40 mM. Osmotic shrinkage activated NHE by reducing this inhibition. In cells in isotonic media + 120 mM sucrose, there was no inhibition, and influx was a hyperbolic function of [Na+](o). The kinetics of Na+-inhibited Na+ influx were analyzed at various extents of osmotic shrinkage. The curves for inhibited Na+ fluxes were sigmoid, indicating more than one Na+ inhibitory site associated with each transporter. Shrinkage significantly increased the Na+ concentration at half-maximal velocity of Na+-inhibited Na+ influx, the mechanism by which shrinkage activates NHE.

  20. Investigation on the intergranular interaction of the soft magnetic granular films by {delta}M(H) curves

    SciTech Connect

    Yao Dongsheng; Ge Shihui; Zhou Xueyun; Zuo Huaping

    2008-07-01

    (Fe{sub 65}Co{sub 35}){sub x}(SiO{sub 2}){sub 1-x} granular films with various volume fraction (x) of Fe{sub 65}Co{sub 35} alloy were fabricated by magnetron sputtering, and the interaction between granules was explored by {delta}M(H) plots. Research results show that {delta}M(H) is positive for the samples in a wide range of 0.42exchange coupling exists among granules. Further research revels that {delta}M(H){sub max} increases gradually with decreasing x, reaching the maximum value at x=0.57, then decreases after x<0.57. Since {delta}M(H){sub max} can effectively reflect the intensity of exchange coupling, the intergranular exchange coupling also increases first, then decreases as x decreases. The microstructure is analyzed with help of the high-resolution transmission electron microscopy, and results show that the variation of exchange coupling with metal volume fraction x is dominated by the change of microstructure of samples. The microstructure of the sample with x=0.57 satisfy the optimization for realizing exchange coupling, leading to excellent soft magnetic properties.

  1. 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.…

  2. 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.…

  3. 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.

  4. 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.

  5. 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.

  6. Intergranular fracture of gamma titanium aluminides under hot working conditions

    SciTech Connect

    Seetharaman, V.; Semiatin, S.L.

    1998-07-01

    A comparative study of the hot workability of a near gamma titanium aluminide alloy Ti-49.5Al-2.5Nb-1.1Mn in the cast and wrought conditions was performed. Tension tests conducted on coarse grain, cast material, and fine grain wrought material revealed a pronounced variation in both fracture/peak stress and ductility with temperature and strain rate. Brittle, intergranular fracture occurring at high strain rates was found to be controlled by wedge crack nucleation, whereas the ductile fracture observed at low strain rates was controlled by the growth of wedge cracks and cavities. Dynamic recrystallization was shown to be the main restorative mechanism to accommodate grain boundary sliding and thereby control the crack growth rates. The ductile-to-brittle (DB) transition was found to be determined by the critical values of a grain size-based stress intensity factor given by the product of the peak/fracture stress and the square root of grain size. A processing map for the near gamma titanium aluminides was constructed based on the comparative analysis of the hot tension and compression test results.

  7. Intergranular corrosion of an aluminum-magnesium-silicon-copper alloy

    SciTech Connect

    Burleigh, T.D.; Ludwiczak, E.; Petri, R.A.

    1995-01-01

    The intergranular (intercrystalline) corrosion (IGC) of a heat-treated aluminum-magnesium-silicon-copper alloy was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM revealed that tall chimneys of corrosion product formed on the surface above the pits during oxygenated salt water immersion. It was postulated that pitting corrosion occurred first and that the corrosion chimneys maintained the acidic, chloride pit environment that subsequently caused IGC (preferential dissolution of the region adjacent to the grain boundaries). TEM foils of the same alloy were immersed in a model pit solution (dilute hydrochloric acid) and showed IGC identical to the corrosion attack seen in the bulk samples. Potentiodynamic polarization in the dilute HCl solution verified that pure Al corroded many times faster than the bulk alloy. These results indicated IGC of this alloy occurred because the depleted region adjacent to the grain boundaries corroded rapidly in acidic solutions. The presence of pits with corrosion chimneys, or some type of occluded cells, must have maintained the acidic environment, which caused IGC.

  8. Micromechanics of intergranular creep failure under cyclic loading

    SciTech Connect

    Giessen, E. van der; Tvergaard, V.

    1996-07-01

    This paper is concerned with a micromechanical investigation of intergranular creep failure caused by grain boundary cavitation under strain-controlled cyclic loading conditions. Numerical unit cell analyses are carried out for a planar polycrystal model in which the grain material and the grain boundaries are modeled individually. The model incorporates power-law creep of the grains, viscous grain boundary sliding between grains as well as the nucleation and growth of grain boundary cavities until they coalesce and form microcracks. Study of a limiting case with a facet-size microcrack reveals a relatively simple phenomenology under either balanced loading, slow-fast loading or balanced loading with a hold period at constant tensile stress. Next, a (non-dimensionalized) parametric study is carried out which focuses on the effect of the diffusive cavity growth rate relative to the overall creep rate, and the effects of cavity nucleation and grain boundary sliding. The model takes account of the build up of residual stresses during cycling, and it turns out that this, in general, gives rise to a rather complex phenomenology, but some cases are identified which approach the simple microcrack behavior. The analyses provide some new understanding that helps to explain the sometimes peculiar behavior under balanced cyclic creep.

  9. Evaluation of stainless steels for their resistance to intergranular corrosion

    NASA Astrophysics Data System (ADS)

    Korostelev, A. B.; Abramov, V. Ya.; Belous, V. N.

    1996-10-01

    Austenitic stainless steels are being considered as structural materials for first wall/blanket systems in the International Thermonuclear Reactor (ITER). The uniform corrosion of stainless steels in water is well known and is not a critical issue limiting its application for the ITER design. The sensitivity of austenitic steels to intergranular corrosion (IGC) can be estimated rather accurately by means of calculation methods, considering structure and chemical composition of steel. There is a maximum permissible carbon content level, at which sensitization of stainless steel is eliminated: K = Cr eff - αC eff, where α-thermodynamic coefficient, Cr eff-effective chromium content (regarding molybdenum influence) and C eff-effective carbon content (taking into account nickel and stabilizing elements). Corrosion tests for 16Cr11Ni3MoTi, 316L and 316LN steel specimens, irradiated up to 2 × 10 22 n/cm 2 fluence have proved the effectiveness of this calculation technique for determination of austenitic steels tendency to IGC. This method is directly applicable in austenitic stainless steel production and enables one to exclude complicated experiments on determination of stainless steel susceptibility to IGC.

  10. First-principles study of the effects of halogen dopants on the properties of intergranular films in silicon nitride ceramics

    NASA Astrophysics Data System (ADS)

    Painter, Gayle S.; Becher, Paul F.; Kleebe, H.-J.; Pezzotti, G.

    2002-02-01

    The nanoscale intergranular films that form in the sintering of ceramics often occur as adherent glassy phases separating the crystalline grains in the ceramic. Consequently, the properties of these films are often equal in importance to those of the constituent grains in determining the ceramic's properties. The measured characteristics of the silica-rich phase separating the crystalline grains in Si3N4 and many other ceramics are so reproducible that SiO2 has become a model system for studies of intergranular films (IGF's). Recently, the influence of fluorine and chlorine dopants in SiO2-rich IGF's in silicon nitride was precisely documented by experiment. Along with the expected similarities between the halogens, some dramatically contrasting effects were found. But the atomic-scale mechanisms distinguishing the effects F and Cl on IGF behavior have not been well understood. First-principles density functional calculations reported here provide a quantum-level description of how these dopant-host interactions affect the properties of IGF's, with specific modeling of F and Cl in the silica-rich IGF in silicon nitride. Calculations were carried out for the energetics, structural changes, and forces on the atoms making up a model cluster fragment of an SiO2 intergranular film segment in silicon nitride with and without dopants. Results show that both anions participate in the breaking of bonds within the IGF, directly reducing the viscosity of the SiO2-rich film and promoting decohesion. Observed differences in the way fluorine and chlorine affect IGF behavior become understandable in terms of the relative stabilities of the halogens as they interact with Si atoms that have lost one if their oxygen bridges.

  11. 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.

  12. Proceedings: 1991 EPRI workshop on secondary-side intergranular corrosion mechanisms

    SciTech Connect

    Partridge, M.J.; Zemitis, W.S. )

    1992-08-01

    A workshop on Secondary-Side Intergranular Corrosion Mechanisms'' was organized by EPRI as an effort to give those working in this area an opportunity to share their results, ideas, and plans. Topics covered included: (1) caustic induced intergranular attack/stress corrosion cracking (IGA/IGSCC), (2) plant experience, (3) boric acid as an IGA/IGSCC remedial measure, (4) lead induced IGA/IGSCC, and (5) acid induced IGA/IGSCC.

  13. Reduction of Intergranular Cracking Susceptibility by Precipitation Control in 2.25Cr Heat-Resistant Steels

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

    This research is performed to decrease reheat cracking susceptibility in the T/P23 heat-resistant steels (2.25Cr1.5WVNbTi), in other words, to reduce phosphorus and sulfur segregation concentration at the prior austenite grain boundary/carbide interfaces (GCIs) and the carbide-free prior austenite grain boundaries (carbide-free PAGBs) causing intergranular cracking. The increase of bulk vanadium content reduces the amount of M23C6 carbides consuming carbon atoms which can repulse phosphorus and sulfur from interfaces, but promotes the precipitation reaction of V-rich MX carbo-nitrides. Such a precipitation reaction results in the lower segregation concentration of phosphorus or no sulfur at the GCIs and the carbide-free PAGBs. This is because the carbon atoms remaining after precipitation reaction segregates to the interfaces and repels phosphorus and sulfur. Also, tungsten segregation can increase the cohesive grain boundary strength as one of the grain boundary strengtheners. Consequently, the lower segregation concentration of the impurities and the segregation of tungsten atoms lower the intergranular cracking susceptibility.

  14. Reduction of Intergranular Cracking Susceptibility by Precipitation Control in 2.25Cr Heat-Resistant Steels

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

    This research is performed to decrease reheat cracking susceptibility in the T/P23 heat-resistant steels (2.25Cr1.5WVNbTi), in other words, to reduce phosphorus and sulfur segregation concentration at the prior austenite grain boundary/carbide interfaces (GCIs) and the carbide-free prior austenite grain boundaries (carbide-free PAGBs) causing intergranular cracking. The increase of bulk vanadium content reduces the amount of M23C6 carbides consuming carbon atoms which can repulse phosphorus and sulfur from interfaces, but promotes the precipitation reaction of V-rich MX carbo-nitrides. Such a precipitation reaction results in the lower segregation concentration of phosphorus or no sulfur at the GCIs and the carbide-free PAGBs. This is because the carbon atoms remaining after precipitation reaction segregates to the interfaces and repels phosphorus and sulfur. Also, tungsten segregation can increase the cohesive grain boundary strength as one of the grain boundary strengtheners. Consequently, the lower segregation concentration of the impurities and the segregation of tungsten atoms lower the intergranular cracking susceptibility.

  15. 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…

  16. 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.

  17. Micromechanisms of intergranular brittle ftacture in intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Vitek, V.

    1991-06-01

    Grain boundaries in intermetallic compounds such as Ni3A1 are inherently brittle. The reason is usually sought in grain boundary cohesion but in metals even brittle fracture is accompanied by some local plasticity and thus not only cohesion but also dislocation mobility in the boundary region need to be studied. We first discuss here the role of an irreversible shear deformation at the crack tip during microcrack propagation assuming that these two processes are concomitant. It is shown that a pre-existing crack cannot propagate in a brittle manner once the dislocation emission occurs. However, if a microcrack nucleates during loading it can propagate concurrently with the development of the irreversible shear deformation at the crack tip. The latter is then the major energy dissipating process. In the second part of this paper we present results of atomistic studies of grain boundaries in Ni3A1 and CU3Au which suggest that substantial structural differences exist between strongly and weakly ordered L12 alloys. We discuss then the consequence of these differences for intergranular brittleness in the framework of the above model for microcrack propagation. On this basis we propose an explanation for the intrinsic intergranular brittleness in some L12 alloys and relate it directly to the strength of ordering. Les joints de grains dans les composés intermétalliques de type Ni3AI sont de nature fragile. L'origine de cette fragilité est habituellement dans la cohésion des joints de grains. Dans les métaux, cependant, même la rupture fragile est accompagnée d'une certaine déformation plastique locale, de telle sorte que non seulement la cohésion mais aussi la mobilité des dislocations près des joints doit être étudiée. Nous discutons d'abord le rôle d'une déformation en cisaillement irréversible en tête de fissure pendant la propagation de cette fissure, en supposant que les deux processus sont concomitants. Nous montrons qu'une fissure préexistante ne

  18. Ceramic fracture mode-intergranular vs transgranular fracture

    SciTech Connect

    Rice, R.W.

    1996-12-31

    Available data on intergranular fracture (IGF) vs transgranular fracture (TGF) of ceramics is summarized and significantly extended. At 22 C, where there is most data, TGF is normally dominant. IGF generally increases with decreasing grain size (G, mainly at G {le} 1-10 {mu}m), increasing grain boundary phase content and the occurrence of (1) slow crack growth, (2) mist, hackle, and crack branching, and (3) (mainly finer, substantial, grain boundary) porosity, and possibly with increasing elastic anisotropy. Possible effects of grain orientation, stress rate and character, as well as microstructural stresses from thermal expansion anisotropy (TEA) are discussed. At higher temperatures, there is a general shift to more IGF, especially with more grain boundary impurities, finer G, and probably higher elastic anisotropy. This shift often starts with IGF only at the fracture origin, and may not commence until temperatures of the order of 1500 C or more in some materials. While IGF is often attributed to weaker grain boundaries (implying lower strengths), it is also often associated with fine grain size, and thus the highest strengths at lower temperatures. IGF vs TGF reflects not just grain boundary strength (as often emphasized), but a balance of this versus the fracture toughness for grain fracture (usually via cleavage, which may also entail the multiplicity of cleavage planes). Several factors may interact to shift differing balances in different materials, e.g. some increase in IGF at larger G in TiB{sub 2} with high TEA, but more IGF increase in Al{sub 2}O{sub 3}, at larger G with less TEA, and no IGF increase in BeO and all TGF in B{sub 4}C having similar TEA to Al{sub 2}O{sub 3}.

  19. [The place of syringe exchange programs in reducing harm in Canadian prisoners].

    PubMed

    Orsi, Mylène M; Brochu, Serge

    2009-01-01

    The prevalence rates of illicit drug consumption within the prison system are much higher than those in the Canadian population in general. Of the substances used in detention, those of most concern to prison and public health authorities are injection drugs, as the sharing of injection drug equipment may be responsible for the high prevalence of blood-borne diseases in prison facilities. Faced with this situation, the Correctional Service of Canada put in practice a number of harm reduction strategies targeting injection drug users, such as methadone maintenance programs and access to bleach. However, despite their use in the community, needle-exchange programs are not yet allowed in penitentiaries. This article analyzes the limits of harm reduction strategies approved by the prison authorities and discusses the sources of resistance that continue to impede the realization of a pilot project to assess the feasibility of needle-exchange programs in detention in Canada.

  20. 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

  1. 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.

  2. 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

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

    PubMed

    McLEAN, Katherine

    2013-09-01

    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.

  4. 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.

  5. Drag reducing effects of polymer additives in a plate heat exchanger for the OTEC system

    SciTech Connect

    Kim, N.; Yoon, S.; Kim, C.; Seo, T.

    1999-07-01

    Experiments were undertaken for a 15kW Alfa-Laval plate heat exchanger utilizing polyethylene oxide as a polymer additive. Concentrations of polymer additives were 5, 10, 20, 30, 40, 50, 100, 200 and 400 wppm at 25 C and mass flow rates were 0.6kg/s, 0.7kg/s, 0.8kg/s and 0.9kg/s in normal operating ranges of the plate heat exchanger. The maximum effects of drag reductions were found at 20 wppm polymer concentration and at approximately 0.7kg/s of mass flow rate. The results show that there exist optimum polymer concentration and at approximately 0.7kg/s of mass flow rate. The results show that there exist optimum polymer concentration and mass flow rate for the plate heat exchanger for maximum drag reduction effects. In most cases, drag reduction of approximately 20% has been obtained. It means considerable savings in pumping power for a large size OTEC plant.

  6. Inter-Granular Relationships and Characterization of Bed Structures for Fluvial Sediment in Gravel-Bed Rivers Using Computed Tomography

    NASA Astrophysics Data System (ADS)

    Voepel, H.; Ahmed, S. I.; Hodge, R. A.; Leyland, J.; Sear, D. A.

    2015-12-01

    Uncertainty in bedload estimates for gravel bed rivers is largely driven by our inability to characterize arrangement, orientation and resultant forces of fluvial sediment in river beds. Water working of grains leads to structural differences between areas of the bed through particle sorting, packing, imbrication, mortaring and degree of bed armoring. In this study, non-destructive, micro-focus X-ray computed tomography (CT) imaging in 3D is used to visualize, quantify and assess the internal geometry of sections of a flume bed that have been extracted keeping their fabric intact. Flume experiments were conducted at 1:1 scaling of our prototype river. From the volume, center of mass, points of contact, and protrusion of individual grains derived from 3D scan data we estimate 3D static force properties at the grain-scale such as pivoting angles, buoyancy and gravity forces, and local grain exposure. By aggregating representative samples of grain-scale properties of localized interacting sediment into overall metrics, we derive inter-granular relationships to compare and contrast bed structure and stability at a macro-scale. This is the first time bed stability has been studied in 3D using CT scanned images of sediment from the bed surface to depths well into the subsurface. The derived metrics and inter-granular relationships and characterization of bed structures will lead to improved bedload estimates with reduced uncertainty.

  7. 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.

  8. Effects of nitrogen on intergranular cohesion in iron: electronic structure modeling

    NASA Astrophysics Data System (ADS)

    Kim, Miyoung; Freeman, A. J.; Geller, Clint B.

    2003-03-01

    Mechanical property data suggest that N tends to embrittle iron based alloys when present at grain boundaries (GBs). For the development of embrittlement mitigation strategies it is of interest whether N alone can embrittle an Fe GB, or whether it must combine with other impurities or alloying additions to form intergranular precipitates. Strengthening energy calculations are reported for an N interstitial impurity in an FeΣ3 [110] (111) coincident-site tilt GB, using the 2D-film FLAPW electronic structure method(Wimmer, Krakauer, Weinert, Freeman, PRB, 24), 864, (1981) at the GGA level of density functional theory. Results indicate that N reduces the GB cohesive energy by 7.8 eV per N atom. Previously reported computational results for C, B, and other interstitial impurities establish a strong, qualitative correlation between FLAPW strengthening energy predictions and observed behavior in Fe and Ni based alloys (Wu, Freeman, Olson, PRB, 50), 75 (1994); 50, 7504 (1996) ( Geng, Freeman, Wu, Geller, and Raynolds, PRB, 60), 7149 (1999) (Smith, Geng, Geller, Wu, Freeman, Scripta Mater., 43), 957 (2000). The results reported here indicate that atomic interstitial N tends to embrittle iron based alloys of steel with elevated N levels, and that precipitate formation is not essential to the embrittlement phenomenon.

  9. Partial manual exchange reduces iron accumulation during chronic red cell transfusions for sickle cell disease

    PubMed Central

    Savage, William J.; Reddoch, Shirley; Wolfe, Jaime; Casella, James F.

    2013-01-01

    Iron overload is an inevitable consequence of chronic red cell transfusions without erythrocytapheresis or chelation therapy. The effectiveness of partial manual exchange, a technique used to slow iron loading, has not been evaluated. We evaluated all children with sickle cell disease (SCD) receiving chronic transfusion to identify chelation naïve subjects who had quantitative liver iron concentration (LIC) studies. Seventeen chelation naïve children with SCD received a median of 29 transfusions prior to first LIC determination. Serum ferritin concentrations were assessed prior to each transfusion. The mean volume of blood phlebotomized prior to each transfusion was 5.1±1.8 cc/kg, which cumulatively resulted in a calculated median 35.0 mg/kg removal of iron. Using linear regression, pretransfusion phlebotomy resulted in a statistically significant reduction in ferritin (-8.8 ng/mL of ferritin for each mg/kg of iron phlebotomized, P = 0.02). A reduction in LIC from pretransfusion phlebotomy could not be established (P =0.4). Partial manual exchanges appear to be an effective strategy for slowing the pace of iron loading in the setting of chronic transfusion for SCD. PMID:23887022

  10. 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.

  11. 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.

  12. Effect of mechanical treatment on intergranular corrosion of 6064 alloy bars

    NASA Astrophysics Data System (ADS)

    Sláma, P.; Nacházel, J.

    2017-02-01

    Aluminium Al-Mg-Si-type alloys (6xxx-series) exhibit good mechanical properties, formability, weldability and good corrosion resistance in various environments. They often find use in automotive industry and other applications. Some alloys, however, particularly those with higher copper levels, show increased susceptibility to intergranular corrosion. Intergranular corrosion (IGC) is typically related to the formation of microgalvanic cells between cathodic, more noble phases and depleted (precipitate-free) zones along grain boundaries. It is encountered mainly in AlMgSi alloys containing Cu, where it is thought to be related to the formation Q-phase precipitates (Al4Mg8Si7Cu2) along grain boundaries. The present paper describes the effects of mechanical working (extrusion, drawing and straightening) and artificial aging on intergranular corrosion in rods of the 6064 alloy. The resistance to intergranular corrosion was mapped using corrosion tests according to EN ISO 11846, method B. Corrosion tests showed dependence of corrosion type on mechanical processing of the material. Intergranular, pitting and transgranular corrosion was observed. Artificial ageing influenced mainly the depth of the corrosion.

  13. 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

  14. Gastrointestinal Inhibition of Sodium-Hydrogen Exchanger 3 Reduces Phosphorus Absorption and Protects against Vascular Calcification in CKD.

    PubMed

    Labonté, Eric D; Carreras, Christopher W; Leadbetter, Michael R; Kozuka, Kenji; Kohler, Jill; Koo-McCoy, Samantha; He, Limin; Dy, Edward; Black, Deborah; Zhong, Ziyang; Langsetmo, Ingrid; Spencer, Andrew G; Bell, Noah; Deshpande, Desiree; Navre, Marc; Lewis, Jason G; Jacobs, Jeffrey W; Charmot, Dominique

    2015-05-01

    In CKD, phosphate retention arising from diminished GFR is a key early step in a pathologic cascade leading to hyperthyroidism, metabolic bone disease, vascular calcification, and cardiovascular mortality. Tenapanor, a minimally systemically available inhibitor of the intestinal sodium-hydrogen exchanger 3, is being evaluated in clinical trials for its potential to (1) lower gastrointestinal sodium absorption, (2) improve fluid overload-related symptoms, such as hypertension and proteinuria, in patients with CKD, and (3) reduce interdialytic weight gain and intradialytic hypotension in ESRD. Here, we report the effects of tenapanor on dietary phosphorous absorption. Oral administration of tenapanor or other intestinal sodium-hydrogen exchanger 3 inhibitors increased fecal phosphorus, decreased urine phosphorus excretion, and reduced [(33)P]orthophosphate uptake in rats. In a rat model of CKD and vascular calcification, tenapanor reduced sodium and phosphorus absorption and significantly decreased ectopic calcification, serum creatinine and serum phosphorus levels, circulating phosphaturic hormone fibroblast growth factor-23 levels, and heart mass. These results indicate that tenapanor is an effective inhibitor of dietary phosphorus absorption and suggest a new approach to phosphate management in renal disease and associated mineral disorders. Copyright © 2015 by the American Society of Nephrology.

  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. Reduced exchange narrowing caused by gate-induced charge carriers in high-mobility donor-acceptor copolymers

    NASA Astrophysics Data System (ADS)

    Tsutsumi, Jun'ya; Matsuoka, Satoshi; Osaka, Itaru; Kumai, Reiji; Hasegawa, Tatsuo

    2017-03-01

    Variations in exciton absorption resulting from charge accumulation in various semiconducting donor-acceptor (DA) copolymer thin films were systematically investigated by gate modulation (GM) spectroscopy by using the field-effect transistor device structure. The GM spectra obtained for high-mobility DA copolymer thin films exhibited second-derivative like line shapes due to an effect of spectral broadening of ordinary exciton absorption spectra by accumulated charges. In contrast, the GM spectra obtained for relatively low-mobility DA copolymer thin films exhibited simple bleaching of exciton absorption spectra, as well as observed for non-DA-type polymers like poly(3-hexylthiophene-2,5-diyl) (P3HT). From a systematic comparison of the GM spectra with temperature-dependent absorption spectra for the polymers in solution, we found that the spectral broadening observed in the GM spectra can be attributed to a reduced effect on the exchange narrowing where excitonic transitions of individual polymer chains are coherently coupled within highly ordered crystalline domains in the polymer thin films. We discuss that the gate-induced charge accumulation in the polymer films effects to suppress the exciton coherence length, which contributes to the reduced exchange narrowing. We also discuss that the whole feature of the GM spectra can be understood in terms of a decomposition into ordered and disordered polymers and that the GM spectra can be used as fine probes for a degree of structural ordering in semiconductor channels of polymer field-effect transistors.

  17. Refolding of denatured/reduced lysozyme at high concentrations by artificial molecular chaperone-ion exchange chromatography.

    PubMed

    Wang, Chaozhan; Zhang, Qinming; Cheng, Yan; Wang, Lili

    2010-01-01

    Development of high efficiency and low cost protein refolding methods is a highlighted research focus in biotechnology. Artificial molecular chaperone (AMC) and protein folding liquid chromatography (PFLC) are two attractive refolding methods developed in recent years. In the present work, AMC and one branch of PFLC, ion exchange chromatography (IEC), are integrated to form a new refolding method, artificial molecular chaperone-ion exchange chromatography (AMC-IEC). This new method is applied to the refolding of a widely used model protein, urea-denatured/dithiothreitol-reduced lysozyme. Many factors influencing the refolding of lysozyme, such as urea concentration, beta-cyclodextrin concentration, molar ratio of detergent to protein, mobile phase flow rate, and type of detergent, were investigated, respectively, to optimize the conditions for lysozyme refolding by AMC-IEC. Compared with normal IEC refolding method, the activity recoveries of lysozyme obtained by AMC-IEC were much higher in the investigated range of initial protein concentrations. Moreover, the activity recoveries obtained by using this newly developed refolding method were still quite high for denatured/reduced lysozyme at high initial concentrations. When the initial protein concentration was 200 mg mL(-1), the activity recovery was over 60%. In addition, the lifetime of the chromatographic column during AMC-IEC was much longer than that during protein refolding by normal IEC. Therefore, AMC-IEC is a high efficient and low cost protein refolding method.

  18. 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.

  19. Moderate shade can increase net gas exchange and reduce photoinhibition in citrus leaves.

    PubMed

    Jifon, John L; Syvertsen, James P

    2003-02-01

    Daily variations in net gas exchange, chlorophyll a fluorescence and water relations of mature, sun-acclimated grapefruit (Citrus paradisi Macfady.) and orange (Citrus sinensis L. Osbeck) leaves were determined in tree canopies either shaded with 50% shade screens or left unshaded (sunlit). Mean daily maximum photosynthetic photon flux density (PPFD) under shade varied from 500 to 700 micromol m-2 s-1 and was sufficient to achieve maximum net CO2 assimilation rates (A CO2). Responses of grapefruit and orange leaves to shading were remarkably similar. At midday, on bright clear days, the temperatures of sunlit leaves were 2-6 degrees C above air temperature and 1-4 degrees C above the temperatures of shaded leaves. Although midday depressions of stomatal conductance (gs) and A CO2 were observed in both sunlit and shaded leaves, shaded leaves had lower leaf-to-air vapor pressure differences (D) along with higher gs, A CO2 and leaf water-use efficiency than sunlit leaves. Estimated stomatal limitation to A CO2 was generally less than 25% and did not differ between shaded and sunlit leaves. Leaf intercellular CO2 partial pressure was not altered by shade treatment and did not change substantially with increasing D. Radiation and high temperature stress-induced non-stomatal limitation to A CO2 in sunlit leaves was greater than 40%. Reversible photoinhibition of photosystem II efficiency was more pronounced in sunlit than in shaded leaves. Thus, non-stomatal factors play a major role in regulating A CO2 of citrus leaves during radiation and high temperature stress.

  20. Exchanges across land-water-scape boundaries in urban systems: strategies for reducing nitrate pollution.

    PubMed

    Cadenasso, M L; Pickett, S T A; Groffman, P M; Band, L E; Brush, G S; Galvin, M F; Grove, J M; Hagar, G; Marshall, V; McGrath, B P; O'Neil-Dunne, J P M; Stack, W P; Troy, A R

    2008-01-01

    Conservation in urban areas typically focuses on biodiversity and large green spaces. However, opportunities exist throughout urban areas to enhance ecological functions. An important function of urban landscapes is retaining nitrogen thereby reducing nitrate pollution to streams and coastal waters. Control of nonpoint nitrate pollution in urban areas was originally based on the documented importance of riparian zones in agricultural and forested ecosystems. The watershed and boundary frameworks have been used to guide stream research and a riparian conservation strategy to reduce nitrate pollution in urban streams. But is stream restoration and riparian-zone conservation enough? Data from the Baltimore Ecosystem Study and other urban stream research indicate that urban riparian zones do not necessarily prevent nitrate from entering, nor remove nitrate from, streams. Based on this insight, policy makers in Baltimore extended the conservation strategy throughout larger watersheds, attempting to restore functions that no longer took place in riparian boundaries. Two urban revitalization projects are presented as examples aimed at reducing nitrate pollution to stormwater, streams, and the Chesapeake Bay. An adaptive cycle of ecological urban design synthesizes the insights from the watershed and boundary frameworks, from new data, and from the conservation concerns of agencies and local communities. This urban example of conservation based on ameliorating nitrate water pollution extends the initial watershed-boundary approach along three dimensions: 1) from riparian to urban land-water-scapes; 2) from discrete engineering solutions to ecological design approaches; and 3) from structural solutions to inclusion of individual, household, and institutional behavior.

  1. Responses of foliar delta13C, gas exchange and leaf morphology to reduced hydraulic conductivity in Pinus monticola branches.

    PubMed

    Cernusak, L A; Marshall, J D

    2001-10-01

    We tested the hypothesis that branch hydraulic conductivity partly controls foliar stable carbon isotope ratio (delta13C) by its influence on stomatal conductance in Pinus monticola Dougl. Notching and phloem-girdling treatments were applied to reduce branch conductivity over the course of a growing season. Notching and phloem girdling reduced leaf-specific conductivity (LSC) by about 30 and 90%, respectively. The 90% reduction in LSC increased foliar delta13C by about 1 per thousand (P < 0.0001, n = 65), whereas the 30% reduction in LSC had no effect on foliar delta13C (P = 0.90, n = 65). Variation in the delta13C of dark respiration was similar to that of whole-tissues when compared among treatments. These isotopic measurements, in addition to instantaneous gas exchange measurements, suggested only minor adjustments in the ratio of intercellular to atmospheric CO2 partial pressures (ci/ca) in response to experimentally reduced hydraulic conductivity. A strong correlation was observed between stomatal conductance (gs) and photosynthetic demand over a tenfold range in gs. Although ci/ca and delta13C appeared to be relatively homeostatic, current-year leaf area varied linearly as a function of branch hydraulic conductivity (r2 = 0.69, P < 0.0001, n = 18). These results suggest that, for Pinus monticola, adjustment of leaf area is a more important response to reduced branch conductivity than adjustment of ci/ca.

  2. Relationship between segregation-induced intergranular fracture and melting in the nickel-sulfur system

    NASA Astrophysics Data System (ADS)

    Heuer, J. K.; Okamoto, P. R.; Lam, N. Q.; Stubbins, J. F.

    2000-06-01

    The effect of S segregation to grain boundaries on the intergranular embrittlement of Ni has been studied at room temperature using Auger electron spectroscopy and slow strain rate tensile tests. The grain-boundary S concentration was varied by time-controlled annealing of dilute Ni-S alloy specimens at 625 °C. The ductile-to-brittle transition in Ni, as determined from percent integranular fracture and reduction-in-area measurements, occurred over a narrow range of S concentrations centered on 15.5±3.4 at. % S. This critical S concentration for 50% intergranular fracture of polycrystalline Ni is similar to the 14.2±3.3 at. % S required to induce 50% amorphization of single-crystal Ni by S+-ion implantation. This suggests that segregation-induced intergranular fracture, like implantation-induced amorphization, may be a disorder-induced polymorphous melting process. In agreement with experimental observations, the polymorphous melting curve for the Ni-S solid solution on the phase diagram drops rapidly to zero as the alloy composition approaches ˜18 at. % S. The critical grain-boundary concentration for intergranular fracture, while slightly less, is within experimental error of the concentration predicted for polymorphous melting as well as that measured for ion-implantation-induced amorphization.

  3. 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.

  4. 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

    2016-03-18

    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.

  5. 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

  6. Intergranular Strain Evolution During Biaxial Loading: A Multiscale FE-FFT Approach

    NASA Astrophysics Data System (ADS)

    Upadhyay, M. V.; Capek, J.; Van Petegem, S.; Lebensohn, R. A.; Van Swygenhoven, H.

    2017-05-01

    Predicting the macroscopic and microscopic mechanical response of metals and alloys subjected to complex loading conditions necessarily requires a synergistic combination of multiscale material models and characterization techniques. This article focuses on the use of a multiscale approach to study the difference between intergranular lattice strain evolution for various grain families measured during in situ neutron diffraction on dog bone and cruciform 316L samples. At the macroscale, finite element simulations capture the complex coupling between applied forces and gauge stresses in cruciform geometries. The predicted gauge stresses are used as macroscopic boundary conditions to drive a mesoscale full-field elasto-viscoplastic fast Fourier transform crystal plasticity model. The results highlight the role of grain neighborhood on the intergranular strain evolution under uniaxial and equibiaxial loading.

  7. Random-Walk Monte Carlo Simulation of Intergranular Gas Bubble Nucleation in UO2 Fuel

    SciTech Connect

    Yongfeng Zhang; Michael R. Tonks; S. B. Biner; D.A. Andersson

    2012-11-01

    Using a random-walk particle algorithm, we investigate the clustering of fission gas atoms on grain bound- aries in oxide fuels. The computational algorithm implemented in this work considers a planar surface representing a grain boundary on which particles appear at a rate dictated by the Booth flux, migrate two dimensionally according to their grain boundary diffusivity, and coalesce by random encounters. Specifically, the intergranular bubble nucleation density is the key variable we investigate using a parametric study in which the temperature, grain boundary gas diffusivity, and grain boundary segregation energy are varied. The results reveal that the grain boundary bubble nucleation density can vary widely due to these three parameters, which may be an important factor in the observed variability in intergranular bubble percolation among grain boundaries in oxide fuel during fission gas release.

  8. Improving intergranular corrosion resistance of sensitized type 316 austenitic stainless steel by laser surface melting

    NASA Astrophysics Data System (ADS)

    Mudali, U. K.; Dayal, R. K.

    1992-06-01

    An attempt was made to modify the surface microstructure of a sensitized austenitic stainless steel, without affecting the bulk properties, using laser surface melting techniques. AISI type 316 stainless steel specimens sensitized at 923 K for 20 hr were laser surface melted using a pulsed ruby laser at 6 J energy. Two successive pulses were given to ensure uniform melting and homogenization. The melted layers were characterized by small angle X- ray diffraction and scanning electron microscopy. Intergranular corrosion tests were carried out on the melted region as per ASTM A262 practice A (etch test) and electrochemical potentiokinetic reactivation test. The results indicated an improvement in the intergranular corrosion resistance after laser surface melting. The results are explained on the basis of homogeneous and nonsensitized microstructure obtained at the surface after laser surface melting. It is concluded that laser surface melting can be used as an in situ method to increase the life of a sensitized component by modifying the surface microstructure.

  9. Intergranular Strain Evolution During Biaxial Loading: A Multiscale FE-FFT Approach

    NASA Astrophysics Data System (ADS)

    Upadhyay, M. V.; Capek, J.; Van Petegem, S.; Lebensohn, R. A.; Van Swygenhoven, H.

    2017-03-01

    Predicting the macroscopic and microscopic mechanical response of metals and alloys subjected to complex loading conditions necessarily requires a synergistic combination of multiscale material models and characterization techniques. This article focuses on the use of a multiscale approach to study the difference between intergranular lattice strain evolution for various grain families measured during in situ neutron diffraction on dog bone and cruciform 316L samples. At the macroscale, finite element simulations capture the complex coupling between applied forces and gauge stresses in cruciform geometries. The predicted gauge stresses are used as macroscopic boundary conditions to drive a mesoscale full-field elasto-viscoplastic fast Fourier transform crystal plasticity model. The results highlight the role of grain neighborhood on the intergranular strain evolution under uniaxial and equibiaxial loading.

  10. 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.

  11. 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.

  12. 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.

  13. Improvement of creep resistance of sintered silicon nitride by hot isostatic exudation of intergranular glass

    SciTech Connect

    Rouxel, T.; Besson, J. ); Goursat, P. )

    1993-11-01

    Postsintering treatment of pressureless-sintered silicon nitride at 1,250 C (i.e., above the glass transition temperature of the amorphous phase) by hot isostatic pressing was performed to diminish the quantity of residual intergranular amorphous phase that results from densification aids. The samples were first embedded in a powder (SiC or Al[sub 2]O[sub 3]), which worked as a diffusion barrier and a pressure transmitter; then, both sample and surrounding powder were encapsulated in evacuated tubes of borosilicate glass or stainless steel. Energy dispersive X-ray spectrometry proved that, during the treatment, a noticeable amount of intergranular vitreous phase exuded out of the sample into powder pores. As a consequence, the creep resistance was enhanced by a factor of 3. When the HIP treatment was associated with a subsequent crystallization treatment, a further improvement in creep resistance was obtained.

  14. 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.

  15. A Visual Basic program for analyzing oedometer test results and evaluating intergranular void ratio

    NASA Astrophysics Data System (ADS)

    Monkul, M. Murat; Önal, Okan

    2006-06-01

    A visual basic program (POCI) is proposed and explained in order to analyze oedometer test results. Oedometer test results have vital importance from geotechnical point of view, since settlement requirements usually control the design of foundations. The software POCI is developed in order perform the necessary calculations for convential oedometer test. The change of global void ratio and stress-strain characteristics can be observed both numerically and graphically. It enables the users to calculate some parameters such as coefficient of consolidation, compression index, recompression index, and preconsolidation pressure depending on the type and stress history of the soil. Moreover, it adopts the concept of intergranular void ratio which may be important especially in the compression behavior of sandy soils. POCI shows the variation of intergranular void ratio and also enables the users to calculate granular compression index.

  16. 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.

  17. Weak shock loadings induce potential hot spots formation around an intergranular pore

    NASA Astrophysics Data System (ADS)

    Ma, Xiao; Li, Xinguo; Zheng, Xianxu; Guo, Wencan; Li, Jianling

    2017-03-01

    The weak shock loading plays the leading role in the unexpected explosion accidents of condensed-phase explosives. Under the weak shock loading conditions, the shear localization is the main factor affecting the formation of hot spots. When a planar stress wave crosses over a pore in the polymeric binder of the polymer bonded explosive (called intergranular pore), the shear localization comes out around the pore, which may induce potential hot spots formation in the polymeric binder and cause the chemical reaction of the nearby energetic crystal granules. In the present work, a novel experiment system consisting of time-resolved shadowgraph and laser-driven compressions was used to record the interactions between the planar stress wave and the intergranular pore. Then, a two-dimensional numerical simulation was performed to calculate the shear localization and the temperature rise around the intergranular pore. The simulation results were in good agreement with the experiments. Finally, the locations of the potential hot spots were determined, and the variations of the locations with the impulse width of incident stress wave were discussed.

  18. 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.

  19. 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.

  20. HREM and STEM of intergranular films at zinc oxide varistor grain boundaries.

    PubMed

    Chiang; Wang; Lee

    1998-09-01

    Grain boundaries in model ZnO-Bi2O3 and ZnO-Bi2O3-CoO varistors and a commercial multicomponent varistor have been characterized by high-resolution electron microscopy (HREM) and scanning transmission electron microscopy (STEM), in order to determine the relationship between Bi grain boundary segregation and formation of thin intergranular films. By controlling Bi2O3 content, applied pressure and temperature, the grain boundary Bi excess has been systematically varied from nearly zero to GammaBi = 1 x 1015 cm-2 ( approximately 1 monolayer), as measured by HB 603 STEM using an area-scan method. HREM shows that intergranular amorphous films are clearly distinguishable in samples with GammaBi > 8 x 1014 cm-2. These films range in thickness, depending on the Bi excess, from 0.6 to 1.5 nm. Similar films of approximately 1 nm thickness are widely observed in the commercial varistor. The composition of the films is a ZnO-Bi2O3 solid solution, which is in all cases more enriched in ZnO than the bulk eutectic liquid. The Bi-doped grain boundaries in ZnO varistors therefore contain an intergranular amorphous film which has not only an equilibrium thickness, but also a distinct equilibrium composition.

  1. 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.

  2. 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

  3. Ethylene reduces plant gas exchange and growth of lettuce grown from seed to harvest under hypobaric and ambient total pressure.

    PubMed

    He, Chuanjiu; Davies, Fred T

    2012-03-01

    Naturally occurring high levels of ethylene can be a problem in spaceflight and controlled environment agriculture (CEA) leading to sterility and irregular plant growth. There are engineering and safety advantages of growing plants under hypobaria (low pressure) for space habitation. The goals of this research were to successfully grow lettuce (Lactuca sativa cv. Buttercrunch) in a long-term study from seed to harvest under hypobaric conditions, and to investigate how endogenously produced ethylene affects gas exchange and plant growth from seed germination to harvest under hypobaric and ambient total pressure conditions. Lettuce was grown under two levels of total gas pressure [hypobaric or ambient (25 or 101 kPa)] in a long-term, 32-day study. Significant levels of endogenous ethylene occurred by day-15 causing reductions in photosynthesis, dark-period respiration, and a subsequent decrease in plant growth. Hypobaria did not mitigate the adverse ethylene effects on plant growth. Seed germination was not adversely affected by hypobaria, but was reduced by hypoxia (6 kPa pO(2)). Under hypoxia, seed germination was higher under hypobaria than ambient total pressure. This research shows that lettuce can be grown from seed to harvest under hypobaria (≅25% of normal earth ambient total pressure). Copyright © 2011 Elsevier GmbH. All rights reserved.

  4. Steps to reduce favorable risk selection in medicare advantage largely succeeded, boding well for health insurance exchanges.

    PubMed

    Newhouse, Joseph P; Price, Mary; Huang, Jie; McWilliams, J Michael; Hsu, John

    2012-12-01

    Within Medicare, the Medicare Advantage program has historically attracted better risks-healthier, lower-cost patients-than has traditional Medicare. The disproportionate enrollment of lower-cost patients and avoidance of higher-cost ones during the 1990s-known as favorable selection-resulted in Medicare's spending more per beneficiary who enrolled in Medicare Advantage than if the enrollee had remained in traditional Medicare. We looked at two measures that can indicate whether favorable selection is taking place-predicted spending on beneficiaries and mortality-and studied whether policies that Medicare implemented in the past decade succeeded in reducing favorable selection in Medicare Advantage. We found that these policies-an improved risk adjustment formula and a prohibition on monthly disenrollment by beneficiaries-largely succeeded. Differences in predicted spending between those switching from traditional Medicare to Medicare Advantage relative to those who remained in traditional Medicare markedly narrowed, as did adjusted mortality rates. Because insurance exchanges set up under the Affordable Care Act will employ similar policies to combat risk selection, our results give reason for optimism about managing competition among health plans.

  5. Water availability drives gas exchange and growth of trees in northeastern US, not elevated CO2 and reduced acid deposition

    PubMed Central

    Levesque, Mathieu; Andreu-Hayles, Laia; Pederson, Neil

    2017-01-01

    Dynamic global vegetation models (DGVM) exhibit high uncertainty about how climate change, elevated atmospheric CO2 (atm. CO2) concentration, and atmospheric pollutants will impact carbon sequestration in forested ecosystems. Although the individual roles of these environmental factors on tree growth are understood, analyses examining their simultaneous effects are lacking. We used tree-ring isotopic data and structural equation modeling to examine the concurrent and interacting effects of water availability, atm. CO2 concentration, and SO4 and nitrogen deposition on two broadleaf tree species in a temperate mesic forest in the northeastern US. Water availability was the strongest driver of gas exchange and tree growth. Wetter conditions since the 1980s have enhanced stomatal conductance, photosynthetic assimilation rates and, to a lesser extent, tree radial growth. Increased water availability seemingly overrides responses to reduced acid deposition, CO2 fertilization, and nitrogen deposition. Our results indicate that water availability as a driver of ecosystem productivity in mesic temperate forests is not adequately represented in DGVMs, while CO2 fertilization is likely overrepresented. This study emphasizes the importance to simultaneously consider interacting climatic and biogeochemical drivers when assessing forest responses to global environmental changes. PMID:28393872

  6. 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

    2015-04-16

    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.

  7. Efficacy of zoniporide, an Na/H exchange ion inhibitor, for reducing perioperative cardiovascular events in vascular surgery patients.

    PubMed

    Fleisher, Lee A; Newman, Mark F; St Aubin, Lisa B; Cropp, Anne B; Billing, C Bill; Bonney, Sharon; Mackey, William C; Poldermans, Don; Corbalan, Roman; Pereira, Adamastor H; Coriat, Pierre

    2005-10-01

    To determine whether a novel Na+/H+ exchange ion inhibitor, zoniporide, is associated with reduced perioperative myocardial ischemic injury in high-risk surgery patients. Randomized double-blind placebo-controlled multidose trial. Multicenter worldwide (105 centers) trial. Patients with known or multiple risk factors for coronary artery disease undergoing noncardiac vascular surgery. Four parallel groups received 1 of 3 doses of zoniporide or placebo, delivered as a 60-minute loading dose immediately before surgery, and followed by a continuous intravenous infusion for up to 7 days. A total of 824 subjects were randomized into the study from 105 centers worldwide. Of these, 784 subjects received study drug infusion in the 3-mg/kg/d, 6-mg/kg/d, and 12-mg/kg/d groups and the placebo group, and 769 satisfied the criteria for the primary efficacy analysis population. This is 68% of the planned sample size of 1125 subjects. Anesthetic management and perioperative cardiac medications were at the discretion of the attending anesthesiologists, surgeons, and cardiologists. The proportion of subjects who experienced the composite endpoint event (death, myocardial infarction, congestive heart failure, arrhythmia) by postsurgical day 30 was 18.5% in the 12-mg/kg/d group, compared with 15.7% in the placebo group, resulting in a relative risk (RR) of 1.17% (95% confidence interval [CI], 0.80-1.72; p = NS) favoring placebo. The proportions in the lower 2 zoniporide dose groups were slightly lower than in the placebo group, although the sample size is inadequate to reach any firm conclusions. The results fail to demonstrate the efficacy of zoniporide in reducing the proportion of patients at high risk undergoing noncardiac vascular surgery who experience a composite cardiovascular endpoint, which led the corporate sponsor to stop enrollment early on the basis of a futility analysis of the chance of demonstrating efficacy with a larger sample size.

  8. 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.

  9. 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.

  10. Effect of interphase mixing on the structure of calcium silicate intergranular film/silicon nitride crystal interfaces

    NASA Astrophysics Data System (ADS)

    Su, Xiaotao; Garofalini, Stephen H.

    2005-06-01

    Molecular-dynamics simulations of intergranular films (IGF) containing Si, O, N, and Ca in contact with Si3N4 surfaces containing different levels of interface mixing of the species from the IGF with the crystal surfaces were performed using a multibody interatomic potential. This mixing is equivalent to the formation of a roughened silicon oxynitride crystal surface. With significant interphase mixing at the crystal surfaces, less ordering into the IGF caused by the compositionally modified oxynitride interfaces is observed. Such results are in contrast to our earlier data that showed significant ordering into the IGF induced by the ideally terminated crystal surfaces with no interphase mixing. In all cases, the central position of the first peak in the Si-O pair distribution function (PDF) at the interface ranges from 1.62 to 1.64 Å, consistent with recent experimental findings. The central position of the first peak in the Si-N PDF ranges from 1.72 to 1.73 Å, consistent with experimental results. With increased interphase mixing, the intensity as well as the area of the first peak of the Si-O and Si-N PDFs for Si attached to the crystal decreases, indicating the decrease of coordination number of O or N with these silicon. Such combined decrease in coordination indicates a significant remnant of vacancies in the crystal surfaces due to the exchange process used here. The results imply a significant effect of interface roughness on the extent of ordering in the amorphous IGF induced by the crystal surface.

  11. 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

  12. Intergranular fracture stress and phosphorus grain boundary segregation of a Mn-Ni-Mo steel

    SciTech Connect

    Naudin, C.; Frund, J.M.; Pineau, A.

    1999-04-09

    Nuclear Reactor Pressure Vessel (RPV) steel A508 class 3 which is a low alloyed steel is not usually sensitive to reversible temper embrittlement when properly heat treated. However heterogeneous zones may be present in particular near the inner side of the vessel. These zones result from the segregation of the alloying elements (C, Mn, Ni, Mo) and impurities (S, P) taking place during solidification of the material. They are called segregated zones (or ghost lines). They can reach 2 mm thick along the radius and 30 mm long through the circumferential direction. Their susceptibility to reversible temper embrittlement is mainly due to grain boundary phosphorus segregation triggering brittle intergranular fracture when the material is tested at low temperature. In this material like in other steels the influence of some other alloying elements (Mo, Mn...) is clearly significant and should also be taken into account. But phosphorus effect has proved to be predominant. The aim of the present study is therefore to find out a quantitative relationship between grain boundary phosphorus segregation and critical intergranular fracture stress. A synthetic steel with a chemical composition representative of an average segregated zone was prepared for the present study. A number of heat treatments were applied to reach different embrittlement conditions. Then brittle fracture properties were obtained by performing cryogenic fracture tests on notched tensile specimens while the corresponding grain boundary phosphorus levels were measured by Auger electron spectroscopy. Systematic fractographic observations were carried out. Moreover an attempt to determine the influence of temperature on the critical intergranular fracture stress was made.

  13. Reduced Flavin: NMR investigation of N(5)-H exchange mechanism, estimation of ionisation constants and assessment of properties as biological catalyst

    PubMed Central

    Macheroux, Peter; Ghisla, Sandro; Sanner, Christoph; Rüterjans, Heinz; Müller, Franz

    2005-01-01

    Background The flavin in its FMN and FAD forms is a versatile cofactor that is involved in catalysis of most disparate types of biological reactions. These include redox reactions such as dehydrogenations, activation of dioxygen, electron transfer, bioluminescence, blue light reception, photobiochemistry (as in photolyases), redox signaling etc. Recently, hitherto unrecognized types of biological reactions have been uncovered that do not involve redox shuffles, and might involve the reduced form of the flavin as a catalyst. The present work addresses properties of reduced flavin relevant in this context. Results N(5)-H exchange reactions of the flavin reduced form and its pH dependence were studied using the 15N-NMR-signals of 15N-enriched, reduced flavin in the pH range from 5 to 12. The chemical shifts of the N(3) and N(5) resonances are not affected to a relevant extent in this pH range. This contrasts with the multiplicity of the N(5)-resonance, which strongly depends on pH. It is a doublet between pH 8.45 and 10.25 that coalesces into a singlet at lower and higher pH values. From the line width of the 15N(5) signal the pH-dependent rate of hydrogen exchange was deduced. The multiplicity of the 15N(5) signal and the proton exchange rates are little dependent on the buffer system used. Conclusion The exchange rates allow an estimation of the pKa value of N(5)-H deprotonation in reduced flavin to be ≥ 20. This value imposes specific constraints for mechanisms of flavoprotein catalysis based on this process. On the other hand the pK ≈ 4 for N(5)-H protonation (to form N(5)+-H2) would be consistent with a role of N(5)-H as a base. PMID:16309555

  14. 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.

  15. 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…

  16. 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…

  17. 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

  18. Automatic Detection and Extraction Algorithm of Inter-Granular Bright Points

    NASA Astrophysics Data System (ADS)

    Feng, Song; Ji, Kai-fan; Deng, Hui; Wang, Feng; Fu, Xiao-dong

    2012-12-01

    Inter-granular Bright Points (igBPs) are small-scale objects in the Solar photosphere which can be seen within dark inter-granular lanes. We present a new algorithm to automatically detect and extract igBPs. Laplacian and Morphological Dilation (LMD) technique is employed by the algorithm. It involves three basic processing steps: (1) obtaining candidate ``seed" regions by Laplacian; (2) determining the boundary and size of igBPs by morphological dilation; (3) discarding brighter granules by a probability criterion. For validating our algorithm, we used the observed samples of the Dutch Open Telescope (DOT), collected on April 12, 2007. They contain 180 high-resolution images, and each has a 85 × 68 arcsec^{2} field of view (FOV). Two important results are obtained: first, the identified rate of igBPs reaches 95% and is higher than previous results; second, the diameter distribution is 220 ± 25 km, which is fully consistent with previously published data. We conclude that the presented algorithm can detect and extract igBPs automatically and effectively.

  19. 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.

  20. Intergranular solid-fluid phase transformations under stress: The effect of surface forces

    NASA Astrophysics Data System (ADS)

    Heidug, Wolfgang K.

    1995-04-01

    Existing work on mineral solubility in fluid-infiltrated and stressed rock has remained limited in that it has neglected surface forces. These forces are appreciable only when the fluid exists as a thin film, as in the grain-to-grain contact zone and in microcracks. Indeed, when the film thickness is of the order of 10(exp -9) m or so, the strength of the forces can be comparable to overburden stress at several kilometers depth. In this contribution we develop the thermodynamics of the phase reaction between nonhydrostatically stressed grains and an intervening water layer by using the concept of the disjoining pressure to account for surface forces acting in the grain-to-grain contact zone. Using a thermodynamic extremum principle, we find an extended version of Gibb's classical condition for the equilibrium of a stressed solid in contact with its solution phase. We then employ nonequilibrium thermodynamics to formulate kinetic equations describing phase boundary migration and intergranular mass transfer. It is demonstrated that surface forces weaken the efficacy with which diffusion removes dissolved material from the grain-to-grain contact zone and enhance the tendency of intergranular pressure solution to flatten initially rough surfaces.

  1. 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.

  2. 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)

  3. 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.

  4. A phenomenological model for intergranular failure by r-type and wedge-type cavitation

    SciTech Connect

    Lee, S.B.; Miller, A.K.

    1995-07-01

    Equations to predict local intergranular failure (by r-type and wedge-type cavitation and the coupling between them) have been developed. The derivation has utilized physically based concepts such as thermal activation of the controlling processes, wedge cracking driven by grain boundary sliding, and cavity growth driven by diffusion. It has also been based upon phenomenological observations such as the variation in the steady-state creep rate with stress and temperature, incomplete healing of cavities under compression, and differences in life under slow-fast and fast-slow cycling. The model has been tested against data on the low-cycle fatigue life of 304 stainless steel under unequal ramp rates. The new equations simulate, for example, the differences in life produced by slow-fast, fast-slow, and equal ramp rate cycling in terms of their effects on internal cavitation. Together with the new equations` ability to treat monotonic creep rupture, these comparisons demonstrate that the intergranular failure equations are capable of simulating a number of phenomena of importance in life prediction for high-temperature structures.

  5. A study on electromigration-inducing intergranular fracture of fine silver alloy wires

    NASA Astrophysics Data System (ADS)

    Hsueh, Hao-Wen; Hung, Fei-Yi; Lui, Truan-Sheng

    2017-01-01

    In this study, Pd-coated Cu, Ag (purity = 4 N), and Ag alloy (Ag-8Au-3Pd) wires were employed to measure the tensile properties during current stressing using the so-called dynamic current tensile (DCT) test. Both the tensile strength and elongation of the wires decreased dramatically in the DCT test, particularly of the Ag-based wires, and the fracture morphology of the Cu-based and Ag-based wires was ductile fracture and intergranular fracture, respectively. Compared to the Cu-based wires, electromigration occurred more easily in the Ag-based wires, and it always generated voids and cracks at the grain boundaries; therefore, the fracture morphology of the Ag-based wires was intergranular fracture owing to the weakened grain boundary. Further, the results indicated that the Ag-based wires could not carry a higher current density than the Cu-based wires, primarily because their extremely low strength and elongation in current stressing might cause serious reliability problems.

  6. Intergranular stress-corrosion cracking of austenitic stainless steels in PWR boric-acid storage systems

    SciTech Connect

    Macdonald, D.D.; Cragnolino, G.A.; Olemacher, J.; Chen, T.Y.; Dhawale, S.

    1982-08-01

    A review is presented of the available literature on the intergranular stress corrosion cracking (IGSCC) of austenitic stainless steels at temperatures below 100/sup 0/C, as well as the results of an experimental investigation of the IGSCC of Types 304, 304L, and 316L stainless steels conducted in boric acid environments of the type employed in pressurized nuclear reactors (PWRs) for nuclear shim control. The susceptibility of furnace sensitized Type 304SS to IGSCC was studied using slow strain rate tests as a function of pH, temperature, potential, and concentration of suspected contaminants: chloride, thiosulfate, and tetrathionate. Possible alternate alloys, such as Types 304L and 316L stainless steels, were also tested under those specific conditions that render Type 304SS susceptible to cracking. Corrosion potentials that can be attained in air-saturated boric acid solutions in the presence of the above mentioned species were measured in order to evaluate the propensity towards intergranular cracking under conditions simulating those that prevail in service.

  7. Mitigation of Intergranular Stress Corrosion Cracking in Al-Mg by Electrochemical Potential Control

    NASA Astrophysics Data System (ADS)

    McMahon, M. E.; Scully, J. R.; Burns, J. T.

    2017-08-01

    Intergranular stress corrosion cracking in the Al-Mg alloy AA5456-H116 is suppressed via cathodic polarization in 0.6 M NaCl, saturated (5.45 M) NaCl, 2 M MgCl2, and saturated (5 M) MgCl2. Three zones of intergranular stress corrosion cracking (IG-SCC) susceptibility correlate with pitting potentials of unsensitized AA5456-H116 and pure β phase (Al3Mg2) in each solution. These critical potentials reasonably describe the influence of α Al matrix and β phase dissolution rates on IG-SCC severity. Complete inhibition occurred at applied potentials of -1.0 V and -1.1 V versus saturated calomel electrode ( V SCE) in 0.6 M NaCl. Whereas only partial mitigation of IG-SCC was achieved at -0.9 V SCE in 0.6 M NaCl and at -0.9, -1.0, and -1.1 V SCE in the more aggressive environments. Correlation of pitting potentials in bulk environments with IG-SCC behavior suggests an effect of bulk environment [Cl-] and pH on the stabilized crack tip chemistry.

  8. Effect of prior cold work on intergranular and transgranular corrosion in type 304 stainless steels: Quantitative discrimination by image analysis

    SciTech Connect

    Garcia, C.; Martin, F.; De Tiedra, P.; Heredero, J.A.; Aparicio, M.L.

    2000-03-01

    Stainless steel (AISI 304 [UNS S30400]) was evaluated as a function of prior cold work and several thermal sensitization treatments. Traditional experimental techniques such as ASTM A262, practice A; modified Strauss test; electrochemical potentiokinetic reactivation (EPR); and electrochemical potentiokinetic reactivation double-loop (EPRDL) were used. Microstructural studies also were conducted. Analysis of the results showed the presence of transgranular attack (TGA) and intergranular attack (IGA) and a transition phenomenon between them. The IGA and TBA contributions to this transition phenomenon were analyzed and quantified by a new procedure based on quantitative metallography performed by image analysis. Using this new methodology, it was possible to determine the most dangerous degrees of deformation for the development of intergranular corrosion (IGC), transgranular corrosion (TGC), intergranular stress corrosion cracking (IGSCC), and transgranular stress corrosion cracking (TGSCC) for different sensitization conditions.

  9. Mechanisms of stress corrosion cracking and intergranular attack in Alloy 600 in high temperature caustic and pure water

    SciTech Connect

    Bandy, R.; van Rooyen, D.

    1984-01-01

    In recent years, several studies have been conducted on the intergranular stress corrosion cracking (SCC) and intergranular attack (IGA) of Alloy 600. A combination of SCC and IGA has been observed in Alloy 600 tubing on the hot leg of some operating steam generators in pressurized water reactor (PWR) nuclear power plants, and sodium hydroxide along with several other chemical species have been implicated in the tube degradations. SCC has been observed above and within the tube sheet, whereas IGA is generally localized within the tube sheet. Alloy 600 is also susceptible to SCC in pure and primary water. Various factors that influence SCC and IGA include metallurgical conditions of the alloy, concentrations of alkaline species, impurity content of the environment, temperature and stress. The mechanisms of these intergranular failures, however, are not well understood. Some of the possible mechanisms of the SCC and IGA in high temperature water and caustic are described in this paper.

  10. 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. © 2016 Society for the Experimental Analysis of Behavior.

  11. Intergranular Cracking as a Major Cause of Long-Term Capacity Fading of Layered Cathodes

    DOE PAGES

    Liu, Hao; Wolf, Mark; Karki, Khim; ...

    2017-05-26

    Capacity fading has limited commercial layered Li-ion battery electrodes to <70% of their theoretical capacity. Higher capacities can be achieved initially by charging to higher voltages, however, these gains are quickly eroded by a faster fade in capacity. In-creasing lifetimes and reversible capacity is contingent on identifying the origin of this capacity fade to inform electrode design and synthesis. We must understand how the battery reactions change following capacity loss after long-term cycling. Using operando X-ray diffraction, we followed the reaction of a LiNi0.8Co0.15Al0.05O2 (NCA) electrode after months of charge-discharge cycles. Furthermore, the heterogeneous reaction kinetics observed during extended cyclesmore » quantitatively explain the capacity loss, which is ultimately attributed to inter-granular fracturing that degrades the connectivity of sub-surface grains within the polycrystalline NCA aggregate.« less

  12. 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.

  13. Depth sizing of intergranular attack with multi-frequency analysis of eddy current data

    NASA Astrophysics Data System (ADS)

    Lei, Jia; Horn, Dag

    2014-02-01

    Depth sizing of intergranular attack (IGA) with conventional eddy-current analysis is difficult, and typically gives results of poor accuracy. This paper presents a sizing technique using multi-frequency analysis for bobbin probe and X-Probe eddy-current data, along with a case study of outer-surface IGA in 0.510" (12.95 mm) diameter, 0.044" (1.12 mm) wall Alloy 600 tubing. A mathematical framework for the expected eddy-current phase and amplitude response is provided. Using this formulation, eddy-current amplitude and phase responses at four inspection frequencies are calculated, and compared to the corresponding measured responses. IGA flaw geometry is approximated through the optimization of flaw parameters via a least-squares minimization of the residual from the comparison.

  14. Aberration-corrected transmission electron microscopy of the intergranular phase in magnetic recording media.

    PubMed

    Hossein-Babaei, Faraz; Koh, Ai Leen; Srinivasan, Kumar; Bertero, Gerardo A; Sinclair, Robert

    2012-05-09

    In perpendicular hard disk memory media, nanometric magnetic Co-rich grains are separated by a ∼1 nm thick nonmagnetic and preferably amorphous intergranular phase (IP). Attempts at observing the IP structure at high resolution using TEM have been obstructed by the superposition of lattice fringes from the crystalline grains extending into the IP region in images. Here we present the first images of a magnetic recording medium produced using a spherical aberration-corrected TEM showing the true amorphous IP structure in contrast to the crystalline grains, allowing the accurate determination of the grain-IP interface and the grain and IP dimensions. It is shown that these aberration-corrected TEM images are functionally superior for analyzing certain features of the ultrahigh capacity data recording media.

  15. Thermal treatment, grain boundary composition and intergranular attack resistance of Alloy 690

    SciTech Connect

    Smith, A.J.; Stratton, R.P.

    1992-12-31

    Commercial Alloy 690 PWR steam generator tubes and experimentally produced alloys with varying amounts of carbon, aluminium and titanium have been examined. After simulated mill annealing and thermal treatment, the microstructure and corrosion behaviour in corrosion tests have been investigated. Stress corrosion resistance of selected alloy 690 tubes and experimental alloys has been examined with environments based on pure water, sodium hydroxide and sodium hydroxide + sodium sulphate solutions. Effects of aluminium content and the thermal treatments on the susceptibility to intergranular attack have been examined, although they appear not to be very significant to the amounts of IGA. Samples used in thermal treatments have been further examined with a dedicated scanning transmission electron microscope to show compositional changes at grain boundaries.

  16. Height-dependent Velocity Structure of Photospheric Convection in Granules and Intergranular Lanes with Hinode/SOT

    NASA Astrophysics Data System (ADS)

    Oba, T.; Iida, Y.; Shimizu, T.

    2017-02-01

    The solar photosphere is the visible surface of the Sun, where many bright granules, surrounded by narrow dark intergranular lanes, are observed everywhere. The granular pattern is a manifestation of convective motion at the photospheric level, but its velocity structure in the height direction is poorly understood observationally. Applying bisector analysis to a photospheric spectral line recorded by the Hinode Solar Optical Telescope, we derived the velocity structure of the convective motion in granular regions and intergranular lanes separately. The amplitude of motion of the convective material decreases from 0.65 to 0.40 km s‑1 as the material rises in granules, whereas the amplitude of motion increases from 0.30 to 0.50 km s‑1 as it descends in intergranular lanes. These values are significantly larger than those obtained in previous studies using bisector analysis. The acceleration of descending materials with depth is not predicted from the convectively stable condition in a stratified atmosphere. Such convective instability can be developed more efficiently by radiative cooling and/or a gas pressure gradient, which can control the dynamical behavior of convective material in intergranular lanes. Our analysis demonstrated that bisector analysis is a useful method for investigating the long-term dynamic behavior of convective material when a large number of pixels is available. In addition, one example is the temporal evolution of granular fragmentation, in which downflowing material develops gradually from a higher layer downward.

  17. Intergranular attack of alloy 600: Simulation and remedial action tests: Final report

    SciTech Connect

    Daret, J.; Feron, D.

    1989-02-01

    The intergranular attack (IGA) that affects alloy 600 tubes in the tube sheet crevices of PWR steam generators is hard to simulate in laboratory studies. For this study, a special apparatus was designed with a range of representative materials, mechanical conditions and geometry. The design also took account of sludge piles, thermal fluxes and water chemistry. During a first series of seven model boiler tests, chemical parameters and test procedures were adjusted to finally obtain a field prototypical degradation of tubing over a significant length within the tube sheet crevice for the case of caustic pollution. IGA was not produced for the river water in-leakage case. A second series of model boiler tests also showed the possibility of producing a representative IGA by initially filling the tube sheet crevices with concentrated caustic solutions. A third series of five model boiler tests aimed at studying in the effectiveness of remedial actions on either virgin of IGA affected tubing. Tube sheet crevice flushing operations using the natural circulation procedure showed a poor efficiency for moving concentrated contaminants, but they succeeded in forcing chemicals additives (acetic acid or boric acid) within the non-occluded portions of crevices. This off-line treatment resulted in a reduction in the progression rate of the pre-existing IGA by a factor of 2 to 3. Simulation of this treatment on virgin material showed that this result was obtained because acetate or borate shifted the cation-to-anion equivalent ratio to well under one. However this off-line treatment could not prevent the occurrence of intergranular stress corrosion cracking (IGSCC) near the top of crevices, since caustic continued to hideout under full power operation. The best remedial action consisted of a combination of off-line and on-line boric acid treatment. IGSCC was prevented both on virgin and IGA affected tubes. 3 figs., 3 tabs.

  18. Small punch test evaluation of intergranular embrittlement of an alloy steel

    SciTech Connect

    Baik, J.M.; Buck, O.; Kameda, J.

    1983-12-01

    The ductile-brittle transition temperature in steel is commonly determined using Charpy V-notch impact specimens as specified by ASTM E23-81. In some specific cases, however, the use of this standardized test specimen may be impractical, if not impossible. For instance, it is well known that ferritic steels show a substantial degradation of the mechanical properties after long time exposure to an irradiation environment. Because of the increase in strength and the reduction in ductility due to neutron irradiation, the Charpy V-notch transition temperature is raised causing concern from a safety point of view. To study these radiation effects, a test specimen much smaller than the standard Charpy V-notch specimen would be extremely desirable for two reasons. First, to study neutron damage small specimens take less space within a reactor. Secondly, the damage achieved in simulation experiments, such as proton or electron accelerators, is limited to small penetration depths. Several efforts on the development of such a small test specimen, similar to that used to determine the ductility of sheet metal, as recommended by ASTM E643-78, have been described in the literature. The paper reports on correlations between small punch (SP) and Charpy V-notch (CVN) test results obtained on temper-embrittled NiCr steel. The ductile-brittle transition temperature (DBTT) with intergranular embrittlement being induced by grain boundary segregation of specific impurities was determined. The relation between test results discussed in terms of the micromechanisms of intergranular cracking. It is suggested that in radiation embrittlement investigations similar correlations may be obtained.

  19. Remedial methods for intergranular attack of alloy 600 tubing. Volume 3. Boric acid and acetic acid remedial methods. Final report

    SciTech Connect

    Rubright, M.M.

    1986-06-01

    An important cause of recent tube degradation in recirculating pressurized water reactor (PWR) steam generators with open tube/tubesheet crevices is intergranular attack (IGA) of alloy 600 tubing in the crevice region. The attack appears to occur on the hot leg tubing because of high concentrations of caustic species formed from remnants of past phosphate water treatment, combined with materials from inleakage from freshwater-cooled condensers. The concept of using neutralizers to modify the aggressiveness of the crevice environment was examined. It appears that this can be accomplished by neutralizing the caustic species with an acid. Two ways to apply the acid are by off-line flushing during plant shutdown and by on-line treatment during operation. The substance that appears to be most suitable for off-line flushing is acetic acid, with boric acid as a second choice. Concentrations should be in the range of from 1000 to 5000 ppM. The addition of 1000 to 5000 ppM of a non-ionic detergent in the flush solution should improve penetration of the crevice. Use of preflush lancing to remove sludge on the tubesheet will also help by reducing acid consumption. The requirements for materials to be used in on-line treatment are more stringent because of possible interaction with other components in the secondry system. Boric acid is the only substance that has operational experience. A series of tests are proposed to investigate the behavior of acetic acid and boric acid on tubesheet sludge, on tubesheet/support plate material, and on alloy 600/tubesheet couples. Similarly, areas of uncertainty of on-line treatment with boric acid are its effect on tubesheet/support plate materials and on the rest of the secondary system. 23 refs.

  20. 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

  1. The Mark Coventry, MD, Award: Oral Antibiotics Reduce Reinfection After Two-Stage Exchange: A Multicenter, Randomized Controlled Trial.

    PubMed

    Frank, Jonathan M; Kayupov, Erdan; Moric, Mario; Segreti, John; Hansen, Erik; Hartman, Curtis; Okroj, Kamil; Belden, Katherine; Roslund, Brian; Silibovsky, Randi; Parvizi, Javad; Della Valle, Craig J

    2017-01-01

    Many patients develop recurrent periprosthetic joint infection after two-stage exchange arthroplasty of the hip or knee. One potential but insufficiently tested strategy to decrease the risk of persistent or recurrent infection is to administer additional antibiotics after the second-stage reimplantation. (1) Does a 3-month course of oral antibiotics decrease the risk of failure secondary to infection after a two-stage exchange? (2) Are there any complications related to the administration of oral antibiotics after a two-stage exchange? (3) In those patients who develop a reinfection, is the infecting organism different from the initial infection? Patients at seven centers randomized to receive 3 months of oral antibiotics or no further antibiotic treatment after operative cultures after the second-stage reimplantation were negative. Adult patients undergoing two-stage hip or knee revision arthroplasty for a periprosthetic infection who met Musculoskeletal Infection Society (MSIS) criteria for infection at the first stage were included. Oral antibiotic therapy was tailored to the original infecting organism(s) in consultation with an infectious disease specialist. MSIS criteria as used by the treating surgeon defined failure. Surveillance of patients for complications, including reinfection, occurred at 3 weeks, 6 weeks, 3 months, 12 months, and 24 months. If an organism demonstrated the same antibiotic sensitivities as the original organism, it was considered the same organism; no DNA subtyping was performed. Analysis was performed as intent to treat with all randomized patients included in the groups to which they were randomized. A log-rank survival curve was used to analyze the primary outcome of reinfection. At planned interim analysis (enrollment is ongoing), 59 patients were successfully randomized to the antibiotic group and 48 patients to the control group. Fifty-seven patients had an infection after TKA and 50 after a THA. There was no minimum followup

  2. Exchanging a few commercial, regularly consumed food items with improved fat quality reduces total cholesterol and LDL-cholesterol: a double-blind, randomised controlled trial.

    PubMed

    Ulven, Stine M; Leder, Lena; Elind, Elisabeth; Ottestad, Inger; Christensen, Jacob J; Telle-Hansen, Vibeke H; Skjetne, Anne J; Raael, Ellen; Sheikh, Navida A; Holck, Marianne; Torvik, Kristin; Lamglait, Amandine; Thyholt, Kari; Byfuglien, Marte G; Granlund, Linda; Andersen, Lene F; Holven, Kirsten B

    2016-10-01

    The healthy Nordic diet has been previously shown to have health beneficial effects among subjects at risk of CVD. However, the extent of food changes needed to achieve these effects is less explored. The aim of the present study was to investigate the effects of exchanging a few commercially available, regularly consumed key food items (e.g. spread on bread, fat for cooking, cheese, bread and cereals) with improved fat quality on total cholesterol, LDL-cholesterol and inflammatory markers in a double-blind randomised, controlled trial. In total, 115 moderately hypercholesterolaemic, non-statin-treated adults (25-70 years) were randomly assigned to an experimental diet group (Ex-diet group) or control diet group (C-diet group) for 8 weeks with commercially available food items with different fatty acid composition (replacing SFA with mostly n-6 PUFA). In the Ex-diet group, serum total cholesterol (P<0·001) and LDL-cholesterol (P<0·001) were reduced after 8 weeks, compared with the C-diet group. The difference in change between the two groups at the end of the study was -9 and -11 % in total cholesterol and LDL-cholesterol, respectively. No difference in change in plasma levels of inflammatory markers (high-sensitive C-reactive protein, IL-6, soluble TNF receptor 1 and interferon-γ) was observed between the groups. In conclusion, exchanging a few regularly consumed food items with improved fat quality reduces total cholesterol, with no negative effect on levels of inflammatory markers. This shows that an exchange of a few commercially available food items was easy and manageable and led to clinically relevant cholesterol reduction, potentially affecting future CVD risk.

  3. Study of the thermal transformations of Co- and Fe-exchanged zeolites A and X by 'in situ' XRD under reducing atmosphere

    SciTech Connect

    Ronchetti, Silvia; Turcato, Elisa Aurelia; Delmastro, Alessandro; Esposito, Serena; Ferone, Claudio; Pansini, Michele; Onida, Barbara; Mazza, Daniele

    2010-06-15

    'In situ' high temperature X-ray diffraction under reducing atmosphere is used for the first time to study the thermal stability and transformations of Co- and Fe-exchanged A and X zeolites. TG-DTA and 'ex situ' XRD characterization were also carried out. The temperature of incipient crystallization of metallic phase was found to be 700 {sup o}C in Fe-zeolites and 800 {sup o}C in Co-zeolites. Moreover, ex situ X-ray experiments, after thermal treatment both under inert and reducing atmosphere, revealed the formation of ceramic phases upon the thermal collapse of the zeolitic framework. Metal nanoparticles were obtained by reduction and the size of metal clusters was found to range between 24 and 40 nm.

  4. Mutagenesis in the switch IV of the helical domain of the human Gsalpha reduces its GDP/GTP exchange rate.

    PubMed

    Echeverría, V; Hinrichs, M V; Torrejón, M; Ropero, S; Martinez, J; Toro, M J; Olate, J

    2000-01-01

    The Galpha subunits of heterotrimeric G proteins are constituted by a conserved GTPase "Ras-like" domain (RasD) and by a unique alpha-helical domain (HD). Upon GTP binding, four regions, called switch I, II, III, and IV, have been identified as undergoing structural changes. Switch I, II, and III are located in RasD and switch IV in HD. All Galpha known functions, such as GTPase activity and receptor, effector, and Gbetagamma interaction sites have been found to be localized in RasD, but little is known about the role of HD and its switch IV region. Through the construction of chimeras between human and Xenopus Gsalpha we have previously identified a HD region, encompassing helices alphaA, alphaB, and alphaC, that was responsible for the observed functional differences in their capacity to activate adenylyl cyclase (Antonelli et al. [1994]: FEBS Lett 340:249-254). Since switch IV is located within this region and contains most of the nonconservative amino acid differences between both Gsalpha proteins, in the present work we constructed two human Gsalpha mutant proteins in which we have changed four and five switch IV residues for the ones present in the Xenopus protein. Mutants M15 (hGsalphaalphaS133N, M135P, P138K, P143S) and M17 (hGsalphaalphaS133N, M135P, V137Y, P138K, P143S) were expressed in Escherichia coli, purified, and characterized by their ability to bind GTPgammaS, dissociate GDP, hydrolyze GTP, and activate adenylyl cyclase. A decreased rate of GDP release, GTPgammaS binding, and GTP hydrolysis was observed for both mutants, M17 having considerably slower kinetics than M15 for all functions tested. Reconstituted adenylyl cyclase activity with both mutants showed normal activation in the presence of AlF(4)(-), but a decreased activation with GTPgammaS, which is consistent with the lower GDP dissociating rate they displayed. These data provide new evidence on the role that HD is playing in modulating the GDP/GTP exchange of the Gsalpha subunit.

  5. The effect of grain boundary misorientation on the intergranular M 23C 6 carbide precipitation in thermally treated Alloy 690

    NASA Astrophysics Data System (ADS)

    Lim, Yun Soo; Kim, Joung Soo; Kim, Hong Pyo; Cho, Hai Dong

    2004-10-01

    The precipitation characteristics of chromium carbides on various types of grain boundaries in Alloy 690 thermally treated at 720 °C for 10 h were studied through transmission electron microscopy. Precipitation of the intergranular chromium carbides, identified as Cr-rich M 23C 6, was retarded on the low angle grain boundaries, compared to that on the random high angle grain boundaries on which coarse and discrete ones were found. They were rarely found on the coherent twin boundaries, however, needle-like ones were evolved on the incoherent twin and twin related Σ9 boundaries. Precipitation of the chromium carbides was also suppressed on the nearly exact coincidence site lattice boundaries such as Σ11 and Σ15, for which the Brandon criterion was fulfilled. The results of the intergranular M 23C 6 carbide precipitation were explained in terms of the influence of the grain boundary energy.

  6. 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.

  7. Effects of water chemistry on intergranular cracking of irradiated austenitic stainless steels

    SciTech Connect

    Chung, H.M.; Ruther, W.E.; Sanecki, J.E.; Hins, A.; Kassner, T.F.

    1995-12-31

    To determine the effects of water chemistry on the susceptibility to irradiation-assisted stress corrosion cracking (IASCC) in austenitic stainless steels, constant-extension-rate tests were conducted in simulated BWR environments on several heats of high- and commercial-purity (HP and CP) Type 304 SS specimens from BWR components irradiated to fluences up to 2.4 {times} 10{sup 21} n cm{sup {minus}2} (E > 1 MeV). Effects of dissolved oxygen (DO) and electrochemical potential (ECP) in 289 C water were investigated. Dependence of susceptibility to intergranular stress corrosion cracking (IGSCC) on DO was somewhat different for the two materials. Susceptibility of the HP heats, less influenced by DO and ECP, was higher than that of CP material for all DO and fluence levels. Percent IGSCC in the CP material was negligible for DO < 0.01 ppm or ECP <{minus}140 mV SHE. Results of analysis by Auger electron spectroscopy indicated that the HP neutron absorber tubes were characterized by relatively lower concentrations of Cr, Ni, and Li and relatively higher concentrations of F and N on grain boundaries than those of the CP materials. It is suggested that a synergism between irradiation-induced grain-boundary Cr depletion and fabrication-related fluorine contamination plays an important role in the stress corrosion cracking behavior of the HP neutron absorber tubes.

  8. 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.

  9. 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.

  10. 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.

  11. Dynamic Embrittlement in Cu-Cr-Zr-Ti Alloy: Evidence of Intergranular Segregation of Sulphur

    NASA Astrophysics Data System (ADS)

    Chenna Krishna, S.; Radhika, K. V.; Tharian, K. Thomas; Swathi Kiranmayee, M.; Sudarshan Rao, G.; Jha, Abhay K.; Pant, Bhanu

    2013-08-01

    In the present investigation, Cu-0.6Cr-0.005Zr-0.0045Ti alloy was subjected to different heat treatment and thermomechanical treatment (TMT) to simulate the conditions experienced during brazing and forming, respectively. Grain coarsening was observed in the samples subjected to heat treatment, and grain refinement was observed in the samples subjected to TMT. Tensile tests conducted with these samples at room temperature and 600 °C have shown that Cu-Cr-Zr-Ti alloy was susceptible to dynamic embrittlement (DE). However, the observation was limited to coarse-grained samples (280-350 μm) at 600 °C. On the other hand, the fine-grained samples (20-40 μm) showed good ductility. Electron microscopy studies conducted on the tensile-tested specimens prone to DE indicated the presence of sulfur on the fractured surface and intergranular segregation of sulfur. Therefore, it can be inferred from the results that DE due to sulfur can occur in Cu-Cr-Zr-Ti alloy at elevated temperature for coarse-grained samples.

  12. The intergranular segregation of boron in substoichiometric Ni/sub 3/Al

    SciTech Connect

    Choudhury, A.

    1987-12-01

    The intermetallic compound Ni/sub 3/Al offers promise as a material for high temperature applications. In addition to its unusual property of increasing strength with temperature (until approx.700/sup 0/C), it has excellent corrosion and oxidation resistance. Microalloying the alloy with boron has been shown to be dramatically effective in improving its inherent intergranular brittleness. This improvement results from the strong tendency of boron to segregate to the grain boundaries of Ni/sub 3/Al. This research deals with the study of the segregation behavior of boron. Auger electron spectroscopy was chosen as the technique adopted to study this segregation. The strong effect of segregant level on the grain boundary strength level can be controlled by thermal history variations and by variations in the level of solute in the bulk. Cathodic hydrogen charging was shown to be a potent tool in opening up other wise cohesive boundaries for analysis. The effective binding energy of boron at the grain boundaries of Ni/sub 3/Al was calculated from experimental data; it was found to vary between 0.2 and 0.45 eV. Kinetics of segregation have been investigated; the present set of kinetic studies were shown to be inadequate to find a diffusion coefficient and that temperatures lower than those studied here need to be used. As an associated investigation, a set of elemental standards were developed for the particular scanning Auger microprobe used in this study. 141 refs., 94 figs., 26 tabs.

  13. 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.

  14. Effect of boric acid on intergranular corrosion in tube support plate crevices. Final report

    SciTech Connect

    Brunet, J.P.; Campan, J.L.

    1993-10-01

    Intergranular attack on steam generator tubing is one important phenomenon involved in availability of Pressurized Water Reactors. Boric acid appears to be a possible candidate for inhibiting the corrosion process. The program performed in Cadarache was supposed to give statistical informations on the boric acid effect. It was based on a large number of samples initially attacked during a program performed by BABCOCK & WILCOX. These samples were sleeved onto Alloy 690 tubes, in order to prevent premature cracking. Unfortunately it was not possible to find chemical conditions able to produce significant additional corrosion; we postulated mainly due to a drastic reduction of the thermal flux resulting from the increase of the tube wall thickness under the tube support plates (TSP). The tests demonstrate that such sleeve could be a possible remedy of the corrosion when introduced under the TSP. The tests show indications of a possible beneficial effect of the boric acid, a large variability of the heats sensitivity to the IGA and a predominant effect of Na{sub 2}CO{sub 3} on IGA production.

  15. 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.

  16. Status report: Intergranular stress corrosion cracking of BWR core shrouds and other internal components

    SciTech Connect

    1996-03-01

    On July 25, 1994, the US Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 94-03 to obtain information needed to assess compliance with regulatory requirements regarding the structural integrity of core shrouds in domestic boiling water reactors (BWRs). This report begins with a brief description of the safety significance of intergranular stress corrosion cracking (IGSCC) as it relates to the design and function of BWR core shrouds and other internal components. It then presents a brief history of shroud cracking events both in the US and abroad, followed by an indepth summary of the industry actions to address the issue of IGSCC in BWR core shrouds and other internal components. This report summarizes the staff`s basis for issuing GL 94-03, as well as the staff`s assessment of plant-specific responses to GL 94-03. The staff is continually evaluating the licensee inspection programs and the results from examinations of BWR core shrouds and other internal components. This report is representative of submittals to and evaluations by the staff as of September 30, 1995. An update of this report will be issued at a later date.

  17. 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.

  18. Crossover from nanoscopic intergranular hopping to conventional charge transport in pyrite thin films.

    PubMed

    Zhang, Xin; Manno, Michael; Baruth, Andrew; Johnson, Melissa; Aydil, Eray S; Leighton, Chris

    2013-03-26

    Pyrite FeS2 is receiving a resurgence of interest as a uniquely attractive thin film solar absorber based on abundant, low-cost, nontoxic elements. Here we address, via ex situ sulfidation synthesis, the long-standing problem of understanding conduction and doping in FeS2 films, an elusive prerequisite to successful solar cells. We find that an abrupt improvement in crystallinity at intermediate sulfidation temperatures is accompanied by unanticipated crossovers from intergranular hopping to conventional transport, and, remarkably, from hole-like to electron-like Hall coefficients. The hopping is found to occur between a small volume fraction of conductive nanoscopic sulfur-deficient grain cores (beneath our X-ray diffraction detection limits), embedded in nominally stoichiometric FeS2. In addition to placing constraints on the conditions under which useful properties can be obtained from FeS2 synthesized in diffusion-limited situations, these results also emphasize that FeS2 films are not universally p-type. Indeed, with no knowledge of the active transport mechanism we demonstrate that the Hall coefficient alone is insufficient to determine the sign of the carriers. These results elucidate the possible transport mechanisms in thin film FeS2 in addition to their influence on the deduced carrier type, an enabling advancement with respect to understanding and controlling doping in pyrite films.

  19. Microstructural Modeling of Intergranular Fracture in Tricrystals With Random Low- and High-Angle Grain Boundaries

    NASA Astrophysics Data System (ADS)

    Bond, David M.; Zikry, Mohammed A.

    2017-03-01

    Intergranular (IG) fracture behavior near triple junctions (TJs) in f.c.c. tricrystals with a variety of grain boundary (GB) misorientations has been investigated. Based on a dislocation-density GB interaction scheme, critical fracture conditions were coupled to evolving dislocation-density pileups and local stresses by using a dislocation-density-based crystalline plasticity formulation within a nonlinear finite-element framework to elucidate the effects of local GB structure, dislocation-GB interactions, and misorientations on IG crack propagation in f.c.c. crystalline materials. Tricrystals with low-angle GBs had higher fracture toughness than tricrystals with high-angle GBs. In TJs with a combination of random low- and high-angle GBs, the formation of dislocation-density pileups in the high-angle GB led to IG crack propagation along the high-angle GB rather than along the low-angle GB. These predictions, which are consistent with experimental observations, indicate that fracture behavior near TJs is controlled by highly local, evolving, and interrelated events, such as dislocation-density pileups and GB misorientations.

  20. 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.

    2016-09-01

    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.

  1. 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.

  2. 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.

  3. 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.

  4. Intergranular corrosion-fatigue failure of cobalt-alloy femoral stems. A failure analysis of two implants.

    PubMed

    Gilbert, J L; Buckley, C A; Jacobs, J J; Bertin, K C; Zernich, M R

    1994-01-01

    Two modular hip implants with a cobalt-alloy head and a cobalt-alloy stem were retrieved after a fracture had occurred in the neck region of the femoral component, eighty-five and seventy months after implantation. Both implants failed less than one millimeter distal to the taper junction between the head and the stem (outside of the taper). The fracture surfaces of the implant were investigated with the use of scanning electron microscopy, to determine the nature of the failure process. The fractures occurred at the grain boundaries of the microstructure and appeared to be the result of three factors: porosity at the grain boundaries; intergranular corrosive attack, initiated both at the head-neck taper and at the free surface; and cyclic fatigue-loading of the stem. The corrosive attack of the free surface was initiated, in part, by the egression of surface grains and by the ingression of fluid into the intergranular regions. Sectioned surfaces showed extensive intergranular corrosive attack in the prosthetic neck localized in the region of the head-neck taper junction and penetrating deeply into the microstructure.

  5. Determination of the equivalent intergranular void ratio - Application to the instability and the critical state of silty sand

    NASA Astrophysics Data System (ADS)

    Nguyen, Trung-Kien; Benahmed, Nadia; Hicher, Pierre-Yves

    2017-06-01

    This paper presents an experimental study of mechanical response of natural Camargue silty sand. The analysis of test results used the equivalent intergranular void ratio instead of the global void ratio. The calculation of equivalent intergranular void ratio requires the determination of parameter b which represents, physically, the fraction of active fines participating on the chain forces network, hence the strength of the soil. A new formula for determining the parameter b by using an approach based on the coordination number distribution and probability calculation is proposed. The validation of the developed relationship was done through back-analysis of published datasets in literature on the effect of fines content on silty sand behavior. It is shown that the equivalent intergranular void ratio calculated with the b value obtained by the new formula is able to provide strong correlation to not only the critical state of but also the onset of instability of various silty sands, in different terms as peak deviator stress, peak stress ratio or cyclic resistance. Therefore, it is suggested that the use of the equivalent void ratio concept and the new b calculating formula is highly desirable in predicting of the silty sand behavior.

  6. Application of Minkowski layer for intergranular fractal surfaces of multiphase active microalloyed and alloyed aluminium-silicate ceramics

    NASA Astrophysics Data System (ADS)

    Purenović, J. M.; Randjelović, M. S.; Matović, B. Z.; Purenović, M. M.

    2015-03-01

    Microalloyed and alloyed aluminium-silicate ceramics represents multiphase and multifunctional solid-solid system. The microstructure of aluminium-silicate ceramics matrix is arranged with favorable relationship between crystallinity and amorphousness. Numbered physical processes and interactions take place in very complex intergranular and interphase areas, making new boundaries and regions with fractal nature. Fractal nature of grains contours, macro, mezzo and micro pores and nanostructure phases at grain boundaries make this ceramics an active dielectric material. The synergistic effect of additives, dislocations and impurities leads to dislocations movement at grain boundaries and fragmentation of existing grains in a large number of micrograins with distinct fractal nature. Hence, permanent change of micromorphology occurs in intergranular area. Fractal analysis of intergranular microstructure has included application of Minkowski layer, correlated with fractal dimension. It represents convex layer of grains contour roughness and irregularity, determined in accordance with grain contours fractality. The introduction of fractal microstructure analysis allows better interpretation of many physical and physico-chemical processes, bearing in mind that Minkowski layer defines grains contact probability.

  7. 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.

  8. 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

  9. Evaluation of a simple intervention to reduce exchange transfusion rates among inborn and outborn neonates in Myanmar, comparing pre- and post-intervention rates.

    PubMed

    Arnolda, G; Thein, A A; Trevisanuto, D; Aung, N; Nwe, H M; Thin, A A; Aye, N S S; Defechereux, T; Kumara, D; Moccia, L

    2015-12-17

    In Myanmar, approximately half of all neonatal hospital admissions are for hyperbilirubinaemia, and tertiary facilities report high rates of Exchange Transfusion (ET). The aim of this study was to evaluate the effectiveness of the pilot program in reducing ET, separately of inborn and outborn neonates. The study was conducted in the Neonatal Care Units of four national tertiary hospitals: two exclusively treating inborn neonates, and two solely for outborn neonates. Prior to intervention, no high intensity phototherapy was available in these units. Intervention in late November 2011 comprised, for each hospital, provision of two high intensity LED phototherapy machines, a photo radiometer, and training of personnel. Hospital-specific data were assessed as Relative Risk (RR) ratios comparing ET rates pre- and post-intervention, and individual hospital results were pooled when appropriate. In 2011, there were 118 ETs among inborn neonates and 140 ETs among outborn neonates. The ET rate was unchanged at Inborn Hospital A (RR = 1.07; 95 % CI: 0.80-1.43; p = 0.67), and reduced by 69 % at Inborn Hospital B (RR = 0.31; 95 % CI: 0.17-0.57; p < 0.0001). For outborn neonates, the pooled estimate indicated that ET rates reduced by 33 % post-intervention (RRMH = 0.67; 95 % CI: 0.52-0.87; p = 0.002); heterogeneity was not a problem. Together with a photoradiometer and education, intensive phototherapy can significantly reduce the ET rate. Inborn Hospital A had four times as many admissions for jaundice as Inborn Hospital B, and did not reduce ET until it received additional high intensity machines. The results highlight the importance of providing enough intensive phototherapy units to treat all neonates requiring high intensity treatment for a full course. Australian New Zealand Clinical Trials Registry ACTRN12615001171505 , 2 November 2015.

  10. 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.

  11. A three-dimensional multiscale model of intergranular hydrogen-assisted cracking

    NASA Astrophysics Data System (ADS)

    Rimoli, J. J.; Ortiz, M.

    2010-07-01

    We present a three-dimensional model of intergranular hydrogen-embrittlement (HE) that accounts for: (i) the degradation of grain-boundary strength that arises from hydrogen coverage; (ii) grain-boundary diffusion of hydrogen; and (iii) a continuum model of plastic deformation that explicitly resolves the three-dimensional polycrystalline structure of the material. The polycrystalline structure of the specimen along the crack propagation path is resolved explicitly by the computational mesh. The texture of the polycrystal is assumed to be random and the grains are elastically anisotropic and deform plastically by crystallographic slip. We use the impurity-dependent cohesive model in order to account for the embrittling of grain boundaries due to hydrogen coverage. We have carried out three-dimensional finite-element calculations of crack-growth initiation and propagation in AISI 4340 steel double-cantilever specimens in contact with an aggressive environment and compared the predicted initiation times and crack-growth curves with the experimental data. The calculated crack-growth curves exhibit a number of qualitative features that are in keeping with observation, including: an incubation time followed by a well-defined crack-growth initiation transition for sufficiently large loading; the existence of a threshold intensity factor K Iscc below which there is no crack propagation; a subsequent steeply rising part of the curve known as stage I; a plateau, or stage II, characterized by a load-insensitive crack-growth rate; and a limiting stress-intensity factor K Ic , or toughness, at which pure mechanical failure occurs. The calculated dependence of the crack-growth initiation time on applied stress-intensity factor exhibits power-law behavior and the corresponding characteristic exponents are in the ball-park of experimental observation. The stage-II calculated crack-growth rates are in good overall agreement with experimental measurements.

  12. 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

    2016-08-01

    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

  13. Evaluation of intergranular attack on Alloy 600: Volume 2, Effectiveness of boric acid: Final report

    SciTech Connect

    Hermer, R.E.; Wolfe, C.R.

    1987-12-01

    The effect of boric acid applied on-line and via crevice flushing was evaluated in this program as a remedial action for intergranular attack on mill annealed Alloy 600 steam generator tubing in tubesheet and support plate crevices. Single tube model boilers were used to simulate the full length of a steam generator tubesheet crevice and the support plate crevices at hot leg conditions. The tubesheet crevices had preloaded inventories of 10% sodium hydroxide/2.5% sodium sulfate solution. All of the crevices were exposed to on-line additions of 0.1 ppM hydroxide and 0.04 ppM sulfate as the sodium salts. These baseline conditions caused pre-existing IGA beneath eccentrically mounted support plates to increase in depth at a rate of 2.40 ..mu..m/day. In the tubesheet crevices the pre-existing IGA increased in depth at a rate of 1.6 ..mu..m/day. The virgin mill annealed tubing in the tubesheet crevice developed IGA at a rate of 0.73 ..mu..m/day during the final 60 days of the 90 day test. The first 30 days were an incubation period during which no IGA occurred. The results of this work suggest that boric acid can inhibit IGA on unattacked tubing when applied continuously at the field specifiation of 5 to 10 ppM in the blowdown. It can also slow down propagation of pre-existing IGA if present in the proper ratio (which requires adequate treatment levels) and if it can access the corrosion sites. Corrosion may progress in areas where boric acid is not able to penetrate in sufficient excess to the corrodent present. 10 refs., 85 figs., 39 tabs.

  14. Selective knockout of astrocytic Na(+) /H(+) exchanger isoform 1 reduces astrogliosis, BBB damage, infarction, and improves neurological function after ischemic stroke.

    PubMed

    Begum, Gulnaz; Song, Shanshan; Wang, Shaoxia; Zhao, Hanshu; Bhuiyan, Mohammad Iqbal H; Li, Eric; Nepomuceno, Rachel; Ye, Qing; Sun, Ming; Calderon, Michael Joseph; Stolz, Donna B; St Croix, Claudette; Watkins, Simon C; Chen, Yinhuai; He, Pingnian; Shull, Gary E; Sun, Dandan

    2017-09-19

    Stimulation of Na(+) /H(+) exchanger isoform 1 (NHE1) in astrocytes causes ionic dysregulation under ischemic conditions. In this study, we created a Nhe1(flox/flox) (Nhe1(f/f) ) mouse line with exon 5 of Nhe1 flanked with two loxP sites and selective ablation of Nhe1 in astrocytes was achieved by crossing Nhe1(f/f) mice with Gfap-Cre(ERT2) Cre-recombinase mice. Gfap-Cre(ERT2+/-) ;Nhe1(f/f) mice at postnatal day 60-90 were treated with either corn oil or tamoxifen (Tam, 75 mg/kg/day, i.p.) for 5 days. After 30 days post-injection, mice underwent transient middle cerebral artery occlusion (tMCAO) to induce ischemic stroke. Compared with the oil-vehicle group (control), Tam-treated Gfap-Cre(ERT2+/-) ;Nhe1(f/f) (Nhe1 KO) mice developed significantly smaller ischemic infarction, less edema, and less neurological function deficits at 1-5 days after tMCAO. Immunocytochemical analysis revealed less astrocytic proliferation, less cellular hypertrophy, and less peri-lesion gliosis in Nhe1 KO mouse brains. Selective deletion of Nhe1 in astrocytes also reduced cerebral microvessel damage and blood-brain barrier (BBB) injury in ischemic brains. The BBB microvessels of the control brains show swollen endothelial cells, opened tight junctions, increased expression of proinflammatory protease MMP-9, and significant loss of tight junction protein occludin. In contrast, the Nhe1 KO mice exhibited reduced BBB breakdown and normal tight junction structure, with increased expression of occludin and reduced MMP-9. Most importantly, deletion of astrocytic Nhe1 gene significantly increased regional cerebral blood flow in the ischemic hemisphere at 24 hr post-MCAO. Taken together, our study provides the first line of evidence for a causative role of astrocytic NHE1 protein in reactive astrogliosis and ischemic neurovascular damage. © 2017 Wiley Periodicals, Inc.

  15. The intergranular segregation of boron in Ni sub 3 Al; Equilibrium segregation and segregation kinetics

    SciTech Connect

    Choudhury, A. . Metals and Ceramics Div.); White, C.L. . Dept. of Metallurgical Engineering); Brooks, C.R. . Dept. of Materials Science and Engineering)

    1992-01-01

    This paper discusses the grain boundary B content of high-purity Ni-24 at% Al alloys containing 0.048, 0.144, 0.240 and 0.480 at %B (100, 300, 500, 1000 ppm mass) determined for samples aged from 1323 to 873 K for sufficient times to attain equilibrium. The B content was derived from Auger electron spectra of the intergranular fracture facets. Many facets were exposed during fracture at {approximately}300 K, and additional facets were formed upon fracturing following hydrogen charging after heat treatment. For each alloy sample, about 25 facets were analyzed. The grain boundary B contents were in the range of 0.5-2.5 at %. The grain boundary B content increased with decreasing temperature and with increasing bulk B content in the alloys. The values were in the range of 0.15-0.45 eV/atom, and increased with increasing temperature and with decreasing bulk B content. These results have been rationalized in terms of a spectrum of binding energies for a given alloy. However, when the entropy of adsorption was taken into account, an enthalpy of adsorption of B to the grain boundary of 0.13 eV/atom was obtained, independent of temperature and bulk B content. This is interpreted to mean that the spectrum of binding energies is quite restricted. The grain boundary B content of these alloys has also been measured as a function of annealing time at 773, 873, 973 and 1173 K. The diffusion coefficient of B in Ni{sub 3}Al at 773 K is about 5 {times} 10{sup {minus}21} m{sup 2}/s, and the equilibrium grain boundary B content is attained at about 3000 s. The diffusion coefficient at 973 K is between 10{sup {minus}16} and 10{sup {minus}17} m{sup 2}/s. The activation energy for diffusion of B in Ni{sup 3}Al is between 200,000 and 300,000 J/mol.

  16. 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

  17. A comparison of sulfur-free and ambient air enclosure techniques for measuring the exchange of reduced sulfur gases between soils and the atmosphere

    NASA Astrophysics Data System (ADS)

    Castro, Mark S.; Galloway, James N.

    1991-08-01

    The exchange of reduced sulfur gases between the atmosphere and forest soils in the Shaver Hollow watershed (Shenandoah National Park, Virginia) were measured with sulfur-free and ambient air enclosures at least twice a month from March through November 1989. Soils within sulfur-free enslosures were sources of carbonyl sulfide (COS) and carbon disulfide (CS2). Atmospheric fluxes of COS and CS2 ranged from 0.77 to 13.03 ng COS-S/sq m-min and from 2.04 to 15.74 ng CS2-S/sq m-min. In contrast, soils within ambient air enclosures were sinks for COS and CS2. Uptake rates of COS and CS2 ranged from 2.78 to 16.20 ng COS-S/sq m-min and from 3.42 to 26.62 ng CS2-S/sq m-min. The discrepancy in the direction of these fluxes was caused by the flux-measurement techniques.

  18. 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.

  19. 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.

  20. 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).

  1. 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.

  2. Ketoconazole ion-exchange fiber complex: a novel method to reduce the individual difference of bioavailability in oral administration caused by gastric anacidity.

    PubMed

    Xin, Che; Li-hong, Wang; Jing, Yuan; Yang, Yang; Yue, Yuan; Qi-fang, Wang; San-ming, Li

    2013-01-01

    Water insoluble faintly alkaline drugs often have potential absorption problem in gastrointestinal tract in oral administration for patients with gastric anacidity. The purpose of the present study is to develop a novel method to improve the absorption of the water insoluble faintly alkaline drug in peroral administration. This method is based on ion exchange of ion-exchange fibers. Water-insoluble faintly alkaline drug ketoconazole was used as a model drug. Ketoconazole and the active groups of the ion-exchange fibers combined into ion pairs based on the acid-base reaction. This drug carrier did not release drugs in deionized water, but in water solution containing other ions it would release the drugs into the solution by ion exchange. Confirmed by the X-ray diffraction and the differential scanning calorimetry (DSC), the ketoconazole combined onto the ion-exchange fibers was in a highly molecular level dispersed state. The improved dissolution of ketoconazole ion-exchange fiber complexes is likely to originate from this ketoconazole's highly dispersed state. Furthermore, due to this ketoconazole's highly dispersed state, ketoconazole ion-exchange fiber complexes significantly decreased the individual difference of absorption in oral administration of ketoconazole caused by the fluctuation of the acid degree in the gastric fluid.

  3. 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.

  4. Laser Processed Heat Exchangers

    NASA Technical Reports Server (NTRS)

    Hansen, Scott

    2017-01-01

    The Laser Processed Heat Exchanger project will investigate the use of laser processed surfaces to reduce mass and volume in liquid/liquid heat exchangers as well as the replacement of the harmful and problematic coatings of the Condensing Heat Exchangers (CHX). For this project, two scale unit test articles will be designed, manufactured, and tested. These two units are a high efficiency liquid/liquid HX and a high reliability CHX.

  5. Reduced expression of microRNA-27a modulates cisplatin resistance in bladder cancer by targeting the cystine/glutamate exchanger SLC7A11

    PubMed Central

    Drayton, Ross M; Dudziec, Ewa; Peter, Stefan; Bertz, Simone; Hartmann, Arndt; Bryant, Helen E; Catto, James WF

    2014-01-01

    Purpose Resistance to cisplatin-based chemotherapy is a major obstacle to bladder cancer treatment. We aimed to identify microRNAs that are dysregulated in cisplatin-resistant disease, ascertain how these contribute to a drug resistant phenotype and how this resistance might be overcome. Experimental Design MicroRNA expression in paired cisplatin resistant and sensitive cell lines was measured. Dysregulated microRNAs were further studied for their ability to mediate resistance. The nature of the cisplatin resistant phenotype was established by measurement of cisplatin/DNA adducts and intracellular glutathione. Candidate microRNAs were examined for their ability to (i) mediate resistance and (ii) alter the expression of a candidate target protein (SLC7A11); direct regulation of SLC7A11 was confirmed using a luciferase assay. SLC7A11 protein and mRNA, and microRNA-27a were quantified in patient tumour material. Results A panel of microRNAs were found to be dysregulated in cisplatin resistant cells. MicroRNA-27a was found to target the cystine/glutamate exchanger SLC7A11 and to contribute to cisplatin resistance through modulation of glutathione biosynthesis. In patients, SLC7A11 expression was inversely related to microRNA-27a expression, and those tumors with high mRNA expression or high membrane staining for SLC7A11 experienced poorer clinical outcomes. Resistant cell lines were resensitized by restoring microRNA-27a expression, or reducing SLC7A11 activity with an siRNA or with sulfasalazine. Conclusion Our findings indicate that microRNA-27a negatively regulates SLC7A11 in cisplatin-resistant bladder cancer, and shows promise as a marker for patients likely to benefit from cisplatin-based chemotherapy. SLC7A11 inhibition with sulfasalazine may be a promising therapeutic approach to the treatment of cisplatin-resistant disease. PMID:24516043

  6. 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

  7. 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

  8. 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.

  9. Spline Implementation of Generalized Gradient Approximations to the Exchange-Correlation Functional and Study of the Sensitivity of Density Functional Accuracy to Localized Domains of the Reduced Density Gradient.

    PubMed

    Peverati, Roberto; Truhlar, Donald G

    2011-12-13

    We present a natural cubic spline implementation of the exchange enhancement factor as a function of the reduced density gradient, and we demonstrate its performance by replicating the results of common GGA functionals. We also investigate the effect on the accuracy of various calculated properties of changing the shape of the exchange enhancement factor and an analogous factor for correlation. The properties considered are main group atomization energies, ionization potentials, electron affinities, proton affinities, alkyl bond dissociation energies, difficult hydrocarbon cases, barrier heights for chemical reactions, noncovalent interactions, atomic energies, metal bond energies, and main group bond lengths.

  10. 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

  11. Sedimentation and response to sea-level rise of a restored marsh with reduced tidal exchange: Comparison with a natural tidal marsh

    USGS Publications Warehouse

    Vandenbruwaene, W.; Maris, T.; Cahoon, D.R.; Meire, P.; Temmerman, S.

    2011-01-01

    Along coasts and estuaries, formerly embanked land is increasingly restored into tidal marshes in order to re-establish valuable ecosystem services, such as buffering against flooding. Along the Scheldt estuary (Belgium), tidal marshes are restored on embanked land by allowing a controlled reduced tide (CRT) into a constructed basin, through a culvert in the embankment. In this way tidal water levels are significantly lowered (ca. 3 m) so that a CRT marsh can develop on formerly embanked land with a ca. 3 m lower elevation than the natural tidal marshes. In this study we compared the long-term change in elevation (ΔE) within a CRT marsh and adjacent natural tidal marsh. Over a period of 4 years, the observed spatio-temporal variations in ΔE rate were related to variations in inundation depth, and this relationship was not significantly different for the CRT marsh and natural tidal marsh. A model was developed to simulate the ΔE over the next century. (1) Under a scenario without mean high water level (MHWL) rise in the estuary, the model shows that the marsh elevation-ΔE feedback that is typical for a natural tidal marsh (i.e. rising marsh elevation results in decreasing inundation depth and therefore a decreasing increase in elevation) is absent in the basin of the CRT marsh. This is because tidal exchange of water volumes between the estuary and CRT marsh are independent from the CRT marsh elevation but dependent on the culvert dimensions. Thus the volume of water entering the CRT remains constant regardless of the marsh elevation. Consequently the CRT MHWL follows the increase in CRT surface elevation, resulting after 75 years in a 2–2.5 times larger elevation gain in the CRT marsh, and a faster reduction of spatial elevation differences. (2) Under a scenario of constant MHWL rise (historical rate of 1.5 cm a-1), the equilibrium elevation (relative to MHWL) is 0.13 m lower in the CRT marsh and is reached almost 2 times faster. (3) Under a scenario of

  12. 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.

  13. Intergranular stress corrosion cracking of alloy 600 and x-750 in high-temperature deaerated water/steam

    NASA Astrophysics Data System (ADS)

    Shen, Yulin; Shewmon, Paul G.

    1991-08-01

    Intergranular stress corrosion cracking (IGSCC) has been studied in two similar nickel-base alloys, alloys 600 and X-750, in deaerated steam at elevated temperatures (380 °C). In both cases, IGSCC occurs through the nucleation, growth, and linkup of grain boundary voids rather than by grain boundary dissolution. The rate of IGSCC is much faster in both alloys when they are heat-treated so that carbon is kept in solution instead of precipitating as grain boundary carbides. This higher carbon content allows the formation of a higher methane pressure in grain boundary voids. Slip impingement on the grain boundary plays a central role in nucleating a set of voids with a spacing of about 0.2 μm. A second set of more closely spaced bubbles develops between these through the action of stress-assisted diffusion of material from the first set of bubbles.

  14. 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.

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

    DOE PAGES

    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

  16. Influence of thermal aging on the intergranular corrosion resistance of types 304LN and 316LN stainless steels

    NASA Astrophysics Data System (ADS)

    Mudali, U. Kamachi; Dayal, R. K.; Gnanamoorthy, J. B.; Rodriguez, P.

    1996-10-01

    Intergranular corrosion (IGC) resistance of types 304LN and 316LN stainless steels (SS) thermally aged at 823, 873, and 923 K for various durations was assessed by ASTM A262 practice A test (electrolytic etch test) and electrochemical potentiodynamic reactivation (EPR) test. The results indicated that the type 316LN SS has significantly improved IGC resistance compared to 304LN SS. Based on the results of these tests, time-temperature-sensitization (TTS) diagrams were developed for both alloys. The secondary precipitates formed during thermal aging treatments were electrochemically extracted and analyzed by X-ray diffraction (XRD) to determine the types of precipitates formed during the aging treatments. The results indicated that the precipitates were mostly of M23C6 carbides.

  17. Influence of thermal aging on the intergranular corrosion resistance of types 304LN and 316LN stainless steels

    SciTech Connect

    Mudali, U.K.; Dayal, R.K.; Gnanamoorthy, J.B.; Rodriguez, P.

    1996-10-01

    Intergranular corrosion (IGC) resistance of types 304LN and 316LN stainless steels (SS) thermally aged at 823, 873, and 923 K for various durations was assessed by ASTM A262 practice A test (electrolytic etch test) and electrochemical potentiodynamic reactivation (EPR) test. The results indicated that the type 316LN SS has significantly improved IGC resistance compared to 304LN SS. Based on the results of these tests, time-temperature-sensitization (TTS) diagrams were developed for both alloys. The secondary precipitates formed during thermal aging treatments were electrochemically extracted and analyzed by X-ray diffraction (XRD) to determine the types of precipitates formed during the aging treatments. The results indicated that the precipitates were mostly of M{sub 23}C{sub 6} carbides.

  18. An analysis of intergranular segregation of sulphur in a low alloy steel by stress-induced diffusion process

    SciTech Connect

    Misra, R.D.K.; Kashyap, B.P.

    1996-09-15

    Grain boundary segregation isotherms, determined through fracture experiments in a scanning Auger microprobe, have recently been employed to study interactions amongst trace and alloying elements in a low alloy steel, to elucidate alloying and microstructural effects and to describe the effects of tensile stress on grain boundary segregation of elements. It was determined from the ready applicability of grain boundary segregation isotherms, recorded for isothermally aged low alloy steels under unstressed and stressed conditions, that the application of tensile stress during aging enhances the grain boundary segregation of trace elements, in particular, sulphur. The present paper is a sequel to the earlier work concerning the influence of applied tensile stress on intergranular segregation of sulphur in 2.6NiCrMoV low alloy steel. The study attempts to corroborate the earlier viewpoint that stress-driven diffusion of impurity element, sulphur, is a transient redistribution process and is a particular manifestation of Coble creep effect.

  19. Electronic structure and bonding of intergranular glassy films in polycrystalline Si3 N4 : Ab initio studies and classical molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Rulis, P.; Chen, J.; Ouyang, L.; Ching, W.-Y.; Su, X.; Garofalini, S. H.

    2005-06-01

    The electronic structure and bonding of a realistic model of an intergranular glassy film (IGF) was studied with multiple computational methods. The model has a Si-O-N glassy region sandwiched between crystalline basal planes of β-Si3N4 and contains a total of 798 atoms. It was constructed with periodic boundary conditions via classical molecular dynamics (MD) techniques using an accurate multibody atomic potential. The model was then further relaxed by the VASP (Vienna ab initio simulation package) program. It is shown that the VASP-relaxed structure reduces the total energy from the MD-relaxed structure by only 47.38eV , validating the accuracy of the multiatom potential used. The calculated electronic structure shows the IGF model to be an insulator with a sizable gap of almost 3eV . Quasidefectlike states can be identified near the band edges arising from the more strained Si-N and Si-O bonds at the interface. Calculation of the Mulliken effective charge and bond order values indicates that the bonds in the glassy region and at the interface can be enhanced and weakened by distortions in the bond length and bond angle. The states at the top of the valence band are derived mostly from the crystalline part of the Si-N bonding while the states at the bottom of the conduction band are dominated by the Si-O bonding in the glassy region. Calculation of the electrostatic potential across the interface shows an average band offset of about 1.5eV between the crystalline β-Si3N4 and the glassy Si-O-N region which could be related to the space charge model for IGF.

  20. Phosphor doping enhanced c-axis alignment and exchange decoupling of sputtered Co-Pt perpendicular thin films

    SciTech Connect

    Yang, Bo; Qin, Gaowu Xiao, Na; Li, Zongbin; Zhao, Xiang; Zuo, Liang; Zhang, Yudong; Esling, Claude

    2016-04-14

    In the present work, Co-23.0 at. % Pt and Co-23.0 at. % Pt-3.67 at. % P thin films with their c-axis perpendicular to the substrate surface were fabricated on a glass substrate by DC magnetron sputtering. X-ray diffraction and transmission electron microscopic analyses demonstrate that the doping of P improves the c-axis alignment and forms P-rich non-magnetic phase at grain boundary areas, the latter resulting in inter-granular exchange decoupling between Co-Pt grains. The improved c-axis alignment and the inter-granular exchange decoupling give rise to the increase of the out of plane coercivity and the squareness of the Co-Pt-P films.

  1. The utility of two daytime icodextrin exchanges to reduce dextrose exposure in automated peritoneal dialysis patients: a pilot study of nine patients.

    PubMed

    Gobin, Jaya; Fernando, Sanjay; Santacroce, Sally; Finkelstein, Fredric O

    2008-01-01

    The use of dextrose-containing solutions in peritoneal dialysis (PD) is thought to be associated with glucose-related toxicity both to the peritoneal membrane and systemically. There has, therefore, been considerable interest in minimizing the use of dextrose exposure during PD. The present study was designed to explore the use of icodextrin in patients with high/high-average transporter characteristics for two exchanges per day to minimize glucose exposure. We performed a 6-month prospective cohort study using two icodextrin exchanges per day in a group of high/high-average transporters maintained on automated PD. Icodextrin levels, serum sodium levels, and glucose exposure were measured at baseline, 3 and 6 months. Nine patients completed the study protocol. While the total volume of PD solution remained the same, there was a reduction in mean glucose exposure from a baseline mean value of 410 +/- 75 to 275 +/- 57 g/day at 3 months and 300 +/- 75 g/day at 6 months. Serum icodextrin levels rose from a baseline mean of 345 +/- 145 to 615 +/- 120 mg/dl at 3 months and 620 +/- 108 mg/dl at 6 months. Serum sodium levels remained stable. The use of two (double) icodextrin exchanges in high/high-average transporters on PD can contribute to reduction in glucose exposure for patients maintained on automated PD and appears to be safe. Copyright 2008 S. Karger AG, Basel.

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

    PubMed Central

    Otto, Caitlin C.; Kilbourne, Jacquelyn

    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

  3. Comparison of the Calculations Results of Heat Exchange Between a Single-Family Building and the Ground Obtained with the Quasi-Stationary and 3-D Transient Models. Part 2: Intermittent and Reduced Heating Mode

    NASA Astrophysics Data System (ADS)

    Staszczuk, Anna

    2017-03-01

    The paper provides comparative results of calculations of heat exchange between ground and typical residential buildings using simplified (quasi-stationary) and more accurate (transient, three-dimensional) methods. Such characteristics as building's geometry, basement hollow and construction of ground touching assemblies were considered including intermittent and reduced heating mode. The calculations with simplified methods were conducted in accordance with currently valid norm: PN-EN ISO 13370:2008. Thermal performance of buildings. Heat transfer via the ground. Calculation methods. Comparative estimates concerning transient, 3-D, heat flow were performed with computer software WUFI®plus. The differences of heat exchange obtained using more exact and simplified methods have been specified as a result of the analysis.

  4. 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.

  5. Predicting susceptibility of alloy 600 to intergranular stress corrosion cracking using a modified electrochemical potentiokinetic reactivation test

    SciTech Connect

    Ahn, M.K.; Kwon, H.S.; Lee, J.H.

    1995-06-01

    Modified double-loop electrochemical potentiokinetic reactivation (DL-EPR) tests were applied to evaluate the degree of sensitization (DOS) for alloy 600 aged at 700 C. Results of the modified DL-EPR test were compared to intergranular stress corrosion cracking (IGSCC) susceptibilities determined in deaerated 0.01 M sodium tetrathionate under deformation at a constant strain rate of 0.93 {times} 10{sup {minus}6}/s. By analyzing the effects of solution concentration, temperature, and scan rate on the electrochemical response in the EPR tests and the morphologies, the optimal modified DL-EPR test condition for alloy 600 was obtained in 0.01 M sulfuric acid + 10 ppm potassium thiocyanate at 25 C and at a scan rate of 0.5 mV/s. The standard DL-EPR test, performed under conditions of 0.5 M H{sub 2}SO{sub 4} + 0.01 M KCNS at 30 C and a scan rate of 1.67 mV/s, provided very poor discriminating power for various DOS of alloy 600 because general and pitting corrosion occurred, in addition to intergranular corrosion. The modified test, however, was highly discriminating because of its highly selective corrosion attack at grain boundaries. IGSCC occurred in samples of alloy 600 aged for < 20 h, and susceptibility to IGSCC{sub s} increased with decreasing aging times up to 1 h, showing maximum IGSCC{sub s} in the sample aged for 1 h. IGSCC{sub s} for the alloy was found to be associated closely with the chromium-depleted profile across grain boundaries. The deeper and narrower chromium-depleted zone produced greater IGSCC{sub s}. It was demonstrated that DOS measured by the modified DL-EPR test was correlated more closely with IGSCC{sub s} than was DOS measured by the standard EPR test. This correlation resulted from the fact that the modified EPR test selectively attacked the more deeply chromium-depleted regions in comparison to the standard EPR test.

  6. 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

  7. Reduced thrombocyte adhesion to endothelialized poly 4-methyl-1-pentene gas exchange membranes—a first step toward bioartificial lung development.

    PubMed

    Hess, Christian; Wiegmann, Bettina; Maurer, Andreas N; Fischer, Philipp; Möller, Lena; Martin, Ulrich; Hilfiker, Andres; Haverich, Axel; Fischer, Stefan

    2010-10-01

    Polymeric materials used in biomedical devices, bioartificial organs, or for the fabrication of tissue engineering scaffolds should completely prevent the activation of the coagulation system and subsequent clot formation. Surface endothelialization is considered an important tool to optimize the blood compatibility of synthetic materials, as a functional endothelial cell layer on an artificial material may help control hemostasis and, therefore, provide a solution to improve the biocompatibility of these materials. Here we report on the endothelialization of poly 4-methyl-1-pentene (PMP) gas exchange membranes using human cord blood-derived late outgrowth endothelial colony forming cells. We achieved complete endothelialization of PMP membranes; and when seeded and cultivated on the membrane, cord blood-derived late outgrowth endothelial colony forming cells maintained both endothelial characteristics and functionality. Endothelialization resulted in significantly lower platelet adhesion and activation compared with unseeded membranes. Of importance, the endothelial layer had no major impact on gas permeability of PMP membranes. This study is a first promising step toward the development of a biofunctionalized surface for the use in gas exchange devices with blood contacting surfaces and a straightforward approach toward a long-term bio-hybrid lung replacement system.

  8. Exchange rate rebounds after foreign exchange market interventions

    NASA Astrophysics Data System (ADS)

    Hoshikawa, Takeshi

    2017-03-01

    This study examined the rebounds in the exchange rate after foreign exchange intervention. When intervention is strongly effective, the exchange rate rebounds at next day. The effect of intervention is reduced slightly by the rebound after the intervention. The exchange rate might have been 67.12-77.47 yen to a US dollar without yen-selling/dollar-purchasing intervention of 74,691,100 million yen implemented by the Japanese government since 1991, in comparison to the actual exchange rate was 103.19 yen to the US dollar at the end of March 2014.

  9. Roles of bulk carbon content on grain size, carbide reactions and intergranular rupture life in 2.25cr martensitic heat resistant steels

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    The steel of a higher bulk carbon content shows the denser precipitation distribution of carbides after the solution treatment followed by tempering. Such a carbide distribution produces the smaller prior austenite grain size after the welding simulation at a high temperature. Because the equilibrium segregation concentration of phosphorus decreases with decreasing prior austenite grain size, the specimen of the higher bulk carbon content shows therefore the longer intergranular rupture life. The rupture life is also increased by the partitioning of phosphorus pre-segregated at prior austenite grain boundary/carbide interfaces onto the fresh surface of precipitates formed on the surface of pre-formed carbides. The intergranular rupture life is additionally increased by the repulsive segregation between carbon and phosphorus which decreases the overall phosphorus segregation concentration at the prior austenite grain boundaries.

  10. 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.

  11. Kinetics of water vapor reactions with intergranular fracture surfaces of Ni{sub 3}Al with and without boron

    SciTech Connect

    Lee, K.H.; Lukowski, J.T.; White, C.L.

    1996-11-15

    In recent years, there has appeared some convincing evidence that the brittleness normally observed in Ni{sub 3}Al polycrystals at ambient temperature and pressure is at least partially due to an environmental effect associated with trace levels of moisture present in many testing environments. In a previous study, the authors found that undoped Ni{sub 3}Al is susceptible to environmental embrittlement in either moist Ar or Ar + 5%H{sub 2} gas, indicating similar embrittling effect of both environments. In contrast to this, boron-doped Ni{sub 3}Al is not very susceptible to moisture-induced embrittlement whereas it is susceptible to gaseous hydrogen-induced intergranular embrittlement. In both H{sub 2}O and H{sub 2} environments, crack tip processes leading to embrittlement may involve gas phase transport to the crack tip, adsorption of the gaseous species (associative and dissociative), absorption and diffusion of atomic hydrogen. Once atomic hydrogen is produced at the surface, its absorption and diffusion should be the same regardless of whether it originates as environmental H{sub 2}O or as H{sub 2}.

  12. Ab initio tensile experiment on a model of an intergranular glassy film in β-Si3N4 with prismatic surfaces

    NASA Astrophysics Data System (ADS)

    Ching, W. Y.; Rulis, Paul; Ouyang, Lizhi; Misra, A.

    2009-02-01

    We report the results of a large-scale ab initio simulation of an intergranular glassy film (IGF) model in β-Si3N4. It is shown that the stress-strain behavior under uniaxial load in the model with prismatic surfaces and few defective bonds is very different from an earlier IGF model with basal planes. The results are explained by the fundamental electronic structure of the model.

  13. 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.

  14. Effect of intergranular versus intragranular cornstarch on tablet friability and in vitro dissolution.

    PubMed

    Chowhan, Z T; Yang, I C

    1983-09-01

    The effect of blending dry cornstarch versus wet granulation with the drug and other excipients on friability and in vitro dissolution of a ticlopidine hydrochloride tablet formulation was studied. The friability of the tablets was reduced by wet granulating cornstarch with the drug and other excipients compared with the dry blending. The dissolution rate and the tablet-to-tablet variability was improved by incorporating cornstarch in the wet-granulation stage. The lactose placebo tablets, which were wet granulated with either a binder solution or without a binder, also showed reduced tablet friability due to the incorporation of cornstarch in the wet-granulation step. Examination of the tablet cross sections under the scanning electron microscope indicated clumping of starch grains when starch was blended in the dry form. Starch grains were well embedded in the other materials of the tablet and not readily visible when starch was wet granulated with the other excipients. This results in better bonding, fewer weak points, and better homogeneity of the starch disintegrator within the tablet, which accounts for better friability and improved dissolution.

  15. Radiation exchange

    SciTech Connect

    Taylor, J.H. )

    1990-01-01

    This book deals with radiation laws, the phenomena of radiation exchange, the quantification of radiation, and the mechanisms whereby radiation is attenuated in passing through the earth's atmosphere. Applications of radiation exchange are discussed, such as the measurement of the effective radiating temperature of the ozonosphere. Also presented is the development of the concept of atmospheric windows and atmospheric transmittance. Radiation exchange experiments between Earth and space are presented and their interpretations given. The book fives detailed, step-by-step procedures for carrying out the radiometric calibration of an infrared prism spectrometer and a radiation thermopile.

  16. 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.

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

    SciTech Connect

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

    2016-06-28

    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.

  18. 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.

  19. Exchange Network

    EPA Pesticide Factsheets

    The Environmental Information Exchange Network (EIEN) is an Internet-based system used by state, tribal and territorial partners to securely share environmental and health information with one another and EPA.

  20. Enhancement of intergranular current density of Sm-based oxypnictide superconductors with Sn addition

    NASA Astrophysics Data System (ADS)

    Singh, Shiv Jee; Shimoyama, Jun-ichi; Ogino, Hiraku; Yamamoto, Akiyasu; Kishio, Kohji

    2014-08-01

    A series of Sn-added Sm1111 sintered bulks (SmFeAs(O, F) + xSn x = 0-0.8) was synthesized, and the influence of Sn addition on the superconducting properties of SmFeAs(O, F) was studied. The cell volume (V) slightly increases with Sn addition in the lightly F-doped Sm1111 (SmFeAsO0.88F0.12), suggesting a slight reduction of F concentration in the lattice, whereas there is almost no change in V for the optimally F-doped sample (SmFeAsO0.8F0.2). The transition temperature (Tc) of SmFeAsO0.88F0.12 decreased from 50 to 40 K for x = 0.35, with another maximum at x = 0.27 (Tc = 50 K). On the other hand, SmFeAsO0.8F0.2 remained an almost constant Tc ˜ 56 K up to x = 0.8. Microstructural analysis depicts that the impurity phases in SmFeAsO0.8F0.2 were reduced by Sn addition, resulting in an increase in clean and well connected grain boundaries. Remanent magnetization measurements revealed that Sn addition improved the intergrain Jc at 5 K from 1 × 102 to 1.1 × 104 A cm-2 for SmFeAsO0.8F0.2 and from 4 × 103 to 9.7 × 103 A cm-2 for SmFeAsO0.88F0.12. We believe this superior intergrain Jc to be attributable to the strong intergrain coupling due to grain connectivity improved by the Sn addition.

  1. 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)

  2. Cohesive zone model for intergranular slow crack growth in ceramics: influence of the process and the microstructure

    NASA Astrophysics Data System (ADS)

    Romero de la Osa, M.; Estevez, R.; Olagnon, C.; Chevalier, J.; Tallaron, C.

    2011-10-01

    Ceramic polycrystals are prone to slow crack growth (SCG) which is stress and environmentally assisted, similarly to observations reported for silica glasses. The kinetics of fracture are known to be dependent on the load level, the temperature and the relative humidity. In addition, evidence is available on the influence of the microstructure on the SCG rate with an increase in the crack velocity with decreasing the grain size. Crack propagation takes place beyond a load threshold, which is grain size dependent. We present a cohesive zone model for the intergranular failure process. The methodology accounts for an intrinsic opening that governs the length of the cohesive zone and allows the investigation of grain size effects. A rate and temperature-dependent cohesive model is proposed (Romero de la Osa M, Estevez R et al 2009 J. Mech. Adv. Mater. Struct. 16 623-31) to mimic the reaction-rupture mechanism. The formulation is inspired by Michalske and Freiman's picture (Michalske and Freiman 1983 J. Am. Ceram. Soc. 66 284-8) together with a recent study by Zhu et al (2005 J. Mech. Phys. Solids 53 1597-623) of the reaction-rupture mechanism. The present investigation extends a previous work (Romero de la Osa et al 2009 Int. J. Fracture 158 157-67) in which the problem is formulated. Here, we explore the influence of the microstructure in terms of grain size, their elastic properties and residual thermal stresses originating from the cooling from the sintering temperature down to ambient conditions. Their influence on SCG for static loadings is reported and the predictions compared with experimental trends. We show that the initial stress state is responsible for the grain size dependence reported experimentally for SCG. Furthermore, the account for the initial stresses enables the prediction of a load threshold below which no crack growth is observed: a crack arrest takes place when the crack path meets a region in compression.

  3. 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.

  4. Sensitization and Intergranular Corrosion Behavior of High Nitrogen Type 304LN Stainless Steels for Reprocessing and Waste Management Applications

    NASA Astrophysics Data System (ADS)

    Parvathavarthini, N.; Kamachi Mudali, U.; Nenova, Lilyana; Andreev, Chavdar; Raj, Baldev

    2012-06-01

    High nitrogen 304LN stainless steels (SS) intended for chloride and nitric acid environments in spent nuclear fuel reprocessing and waste management applications were evaluated for their sensitization and intergranular corrosion (IGC) resistance. For this purpose, high nitrogen (0.132 pct, 0.193 pct and 0.406 pct) containing, impurity-controlled, vanadium-added 304LN SS alloys were developed. For comparison, 304L SS, which is currently used in reprocessing plants, was also studied. These stainless steels were subjected to heat treatment at 948 K (675 °C) for various durations ranging from 1 to 1000 hours and tested for susceptibility to IGC as per ASTM A262 Practice A and E tests. The degree of sensitization was estimated with the double loop electrochemical potentiokinetic reactivation technique. The increase in nitrogen content resulted in higher hardness and finer grain size. Based on the detailed microstructural and corrosion studies, it was determined that an addition of 0.132 pct and 0.193 pct nitrogen showed better IGC resistance and an additional increase in nitrogen resulted in deterioration resulting from chromium nitride precipitation, which was confirmed by electrochemical phase separation and X-ray diffraction studies. The onset of desensitization was faster for the alloy with 0.132 pct nitrogen as well as 0.406 pct nitrogen because of the lower nitrogen content in the former case and the finer grain size in the latter case. The higher hardness and superior IGC resistance of 0.132 pct and 0.193 pct nitrogen containing Type 304LN SS suggests the suitability of this alloy for nitric acid- and chloride-containing environments of reprocessing and waste management plants.

  5. 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.

  6. 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

  7. 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.

  8. Effects of elevated root zone CO2 and air temperature on photosynthetic gas exchange, nitrate uptake, and total reduced nitrogen content in aeroponically grown lettuce plants

    PubMed Central

    He, Jie; Austin, Paul T.; Lee, Sing Kong

    2010-01-01

    Effects of elevated root zone (RZ) CO2 and air temperature on photosynthesis, productivity, nitrate (NO3–), and total reduced nitrogen (N) content in aeroponically grown lettuce plants were studied. Three weeks after transplanting, four different RZ [CO2] concentrations [ambient (360 ppm) and elevated concentrations of 2000, 10 000, and 50 000 ppm] were imposed on plants grown at two air temperature regimes of 28 °C/22 °C (day/night) and 36 °C/30 °C. Photosynthetic CO2 assimilation (A) and stomatal conductance (gs) increased with increasing photosynthetically active radiation (PAR). When grown at 28 °C/22 °C, all plants accumulated more biomass than at 36 °C/30 °C. When measured under a PAR ≥600 μmol m−2 s−1, elevated RZ [CO2] resulted in significantly higher A, lower gs, and higher midday leaf relative water content in all plants. Under elevated RZ [CO2], the increase of biomass was greater in roots than in shoots, causing a lower shoot/root ratio. The percentage increase in growth under elevated RZ [CO2] was greater at 36 °C/30 °C although the total biomass was higher at 28 °C/22 °C. NO3– and total reduced N concentrations of shoot and root were significantly higher in all plants under elevated RZ [CO2] than under ambient RZ [CO2] of 360 ppm at both temperature regimes. At each RZ [CO2], NO3– and total reduced N concentration of shoots were greater at 28 °C/22 °C than at 36 °C/30 °C. At all RZ [CO2], roots of plants at 36 °C/30 °C had significantly higher NO3– and total reduced N concentrations than at 28 °C/22 °C. Since increased RZ [CO2] caused partial stomatal closure, maximal A and maximal gs were negatively correlated, with a unique relationship for each air temperature. However, across all RZ [CO2] and temperature treatments, there was a close correlation between maximal A and total shoot reduced N concentration of plants under different RZ [CO2], indicating that

  9. 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.

  10. Private Health Insurance Exchanges

    PubMed Central

    Buttorff, Christine; Nowak, Sarah; Syme, James; Eibner, Christine

    2017-01-01

    Abstract Private health insurance exchanges offer employer health insurance, combining online shopping, increased plan choice, benefit administration, and cost-containment strategies. This article examines how private exchanges function, how they may affect employers and employees, and the possible implications for the Affordable Care Act's (ACA's) Small Business Health Options Program (SHOP) Marketplaces. The authors found that private exchanges could encourage employees to select less-generous plans. This could expose employees to higher out-of-pocket costs, but premium contributions would drop substantially, so net spending would decrease. On the other hand, employee spending may increase if, in moving to private exchanges, employers decrease their health insurance contributions. Most employers can avoid the ACA's “Cadillac tax” by reducing the generosity of the plans they offer, regardless of whether they move to a private exchange. There is not yet enough evidence to determine whether the private exchanges will become prominent in the insurance market and how they will affect employers and their employees. PMID:28845340

  11. Hibernation and gas exchange.

    PubMed

    Milsom, William K; Jackson, Donald C

    2011-01-01

    Hibernation in endotherms and ectotherms is characterized by an energy-conserving metabolic depression due to low body temperatures and poorly understood temperature-independent mechanisms. Rates of gas exchange are correspondly reduced. In hibernating mammals, ventilation falls even more than metabolic rate leading to a relative respiratory acidosis that may contribute to metabolic depression. Breathing in some mammals becomes episodic and in some small mammals significant apneic gas exchange may occur by passive diffusion via airways or skin. In ectothermic vertebrates, extrapulmonary gas exchange predominates and in reptiles and amphibians hibernating underwater accounts for all gas exchange. In aerated water diffusive exchange permits amphibians and many species of turtles to remain fully aerobic, but hypoxic conditions can challenge many of these animals. Oxygen uptake into blood in both endotherms and ectotherms is enhanced by increased affinity of hemoglobin for O₂ at low temperature. Regulation of gas exchange in hibernating mammals is predominately linked to CO₂/pH, and in episodic breathers, control is principally directed at the duration of the apneic period. Control in submerged hibernating ectotherms is poorly understood, although skin-diffusing capacity may increase under hypoxic conditions. In aerated water blood pH of frogs and turtles either adheres to alphastat regulation (pH ∼8.0) or may even exhibit respiratory alkalosis. Arousal in hibernating mammals leads to restoration of euthermic temperature, metabolic rate, and gas exchange and occurs periodically even as ambient temperatures remain low, whereas body temperature, metabolic rate, and gas exchange of hibernating ectotherms are tightly linked to ambient temperature.

  12. 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

    2016-11-01

    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.

  13. Magnetic anisotropy and exchange in (001) textured FePT-based nanostructures

    NASA Astrophysics Data System (ADS)

    George, Tom Ainsley

    Hard-magnetic L10 phase FePt has been demonstrated as a promising candidate for future nanomagnetic applications, especially magnetic recording at areal densities approaching 10 Tb/in2. Realization of FePt's potential in recording media requires control of grain size and intergranular exchange interactions in films with high degrees of L10 order and (001) crystalline texture, including high perpendicular magnetic anisotropy. Furthermore, a write-assist mechanism must be employed to overcome the high coercivity of L10 FePt nanograins. The research described in this dissertation examines potential solutions to the aforementioned problems. Specifically, a nonepitaxial method of fabricating highly (001) textured thin films is investigated by careful tuning of the as-deposited structure. Such highly textured films could be useful as a template for bit-patterned media. Secondly, control of grain size and intergranular magnetic interactions is demonstrated using non-magnetic additions of Al2O3, C, and Au. Finally, large reductions in the coercivity of high anisotropy, epitaxially grown L10 FePt islands are achieved in an exchange-coupled composite system by adding an exchange coupled layer of FePt:SiO2 with moderate anisotropy. The results show promise for the implementation of L10 FePt in future magnetic recording media and other nanomagnetic applications.

  14. 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.

  15. Mechanisms of intergranular fracture

    SciTech Connect

    Farkas, D.

    1999-08-01

    The authors present a study of the atomistic mechanisms of crack propagation along grain boundaries in metals and alloys. The failure behavior showing cleavage crack growth and/or crack-tip dislocation emission is demonstrated using atomistic simulations for an embedded-atom model. The simulations follow the quasi-equilibrium growth of a crack as the stress intensity applied increases. Dislocations emitted from crack tips normally blunt the crack and inhibit cleavage, inducing ductile behavior. When the emitted dislocations stay near the crack tip (sessile dislocations), they do blunt the crack but brittle cleavage can occur after the emission of a sufficient number of dislocations. The fracture process occurs as a combination of dislocation emission/micro-cleavage portions that are controlled by the local atomistic structure of the grain boundary. The grain boundary is shown to be a region where dislocation emission is easier, a mechanism that competes with the lower cohesive strength of the boundary region.

  16. Quantitative Evaluation of Aged AISI 316L Stainless Steel Sensitization to Intergranular Corrosion: Comparison Between Microstructural Electrochemical and Analytical Methods

    NASA Astrophysics Data System (ADS)

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

    2007-06-01

    The evaluation of the degree of sensitization (DOS) to intergranular corrosion (IGC) of a commercial AISI 316L austenitic stainless steel aged at temperatures ranging from 550 °C to 800 °C during 100 to 80,000 hours was carried out using three different assessment methods. (1) The microstructural method coupled with the Strauss standard test (ASTM A262). This method establishes the kinetics of the precipitation phenomenon under different aging conditions, by transmission electronic microscope (TEM) examination of thin foils and electron diffraction. The subsequent chromium-depleted zones are characterized by X-ray microanalysis using scanning transmission electronic microscope (STEM). The superimposition of microstructural time-temperature-precipitation (TTP) and ASTM A262 time-temperature-sensitization (TTS) diagrams provides the relationship between aged microstructure and IGC. Moreover, by considering the chromium-depleted zone characteristics, sensitization and desensitization criteria could be established. (2) The electrochemical method involving the double loop-electrochemical potentiokinetic reactivation (DL-EPR) test. The operating conditions of this test were initially optimized using the experimental design method on the bases of the reliability, the selectivity, and the reproducibility of test responses for both annealed and sensitized steels. The TTS diagram of the AISI 316L stainless steel was established using this method. This diagram offers a quantitative assessment of the DOS and a possibility to appreciate the time-temperature equivalence of the IGC sensitization and desensitization. (3) The analytical method based on the chromium diffusion models. Using the IGC sensitization and desensitization criteria established by the microstructural method, numerical solving of the chromium diffusion equations leads to a calculated AISI 316L TTS diagram. Comparison of these three methods gives a clear advantage to the nondestructive DL-EPR test when it is

  17. 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

  18. Heat exchanger

    DOEpatents

    Wolowodiuk, Walter

    1976-01-06

    A heat exchanger of the straight tube type in which different rates of thermal expansion between the straight tubes and the supply pipes furnishing fluid to those tubes do not result in tube failures. The supply pipes each contain a section which is of helical configuration.

  19. 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.

  20. 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.

  1. Tax Implications of Forest Property Exchanges

    Treesearch

    William C. Siegel

    1999-01-01

    For various reasons, it may be advantageous for woodland owners to voluntarily exchange some or all of their timber and/or timberland for other property. For example, exchanges can be used to consolidate or diversify forest holdings and other investments; to obtain greater cash flow; and eliminate or reduce management problems. In many cases, voluntary exchanges--...

  2. 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.

  3. Effect of Ag2O addition on the intergranular properties of the superconducting Bi-(Pb)-Sr-Ca-Cu-O system

    NASA Astrophysics Data System (ADS)

    Karaca, I.; Çelebi, S.; Varilci, A.; Malik, A. I.

    2003-01-01

    The effect of Ag2O addition on the Bi-(Pb)-Sr-Ca-Cu-O system has been investigated in terms of ac susceptibility, phase evolution, critical current density and critical temperature. It was found that as the amount of Ag2O addition increases, the intergranular critical current density decreases in our samples (Bi1.84Pb0.34Sr1.91Ca2.03Cu3.06O10) fabricated by ammonium nitrate technique. The analysis for comparison is based on the suppression degree of the diamagnetic behaviour with respect to fields, rapid or slow shift of the summit in chi'(T) to lower temperature with increasing field amplitude and the sharpness of the transition of chi'(T) for intergranular component for the same field amplitude. We also qualitatively discuss experimental results in the framework of the critical state model. The room temperature XRD diagram indicates the presence of large amount of high-Tc (2223) phase. The percentage of Bi-2223 phase in the phase mixture was estimated from the intensities of high-Tc (2223) and low-Tc (2212) phase peaks as 78% for the pure BSCCO sample. Among the Ag2O-added BSCCO samples studied, the one in which 5 wt%Ag2O was added shows the highest rate of Bi-2223 formation as 92%. The SEM analysis reveals some morphological changes induced by silver addition.

  4. Influences of material processing on the microstructure and inter-granular current properties of polycrystalline bulk Ba(Fe,Co)2As2

    NASA Astrophysics Data System (ADS)

    Hayashi, Y.; Yamamoto, A.; Ogino, H.; Shimoyama, J.; Kishio, K.

    2014-09-01

    The phase formation, microstructure, magnetic, and transport properties of Ba(Fe,Co)2As2 polycrystalline bulks prepared by systematically varied synthesis conditions were studied to clarify the key issues for intergranular critical current properties. After optimization of heat treatment process, Ba(Fe0.92Co0.08)2As2 samples with high phase purity and Tc > 25 K were reproducibly obtained. Electron microscopy analyses showed that the use of refined starting powder by high-energy ball-milling yield microstructure with improved uniformity and Ba(Fe,Co)2As2 phase can be synthesized at lower temperature down to 500 °C owing to an increased reactivity. The samples synthesized at low temperature showed well-connected microstructure with fine grain size and intergranular critical current density progressively improved with lowering the heating temperature. Our results suggest that fine grain size and grain boundary structure formed at low temperature are favorable for increasing the area of effective transport current path, while they are electromagnetically weakly coupled and suppressed under external magnetic field.

  5. The microtube strip heat exchanger

    SciTech Connect

    Doty, F.D.; Hosford, G.; Spitzmesser, J.B. ); Jones, J.D. . School of Engineering Science)

    1991-01-01

    The advantages of designing heat exchangers in the laminar-flow regime are discussed from a theoretical standpoint. It is argued that laminar-flow designs have the advantages of reducing thermodynamic and hydrodynamic irreversibilities, and hence increasing system efficiency. More concretely, laminar-flow heat exchangers are free from the turbulence-induced vibration common in conventional heat exchangers, and can thus offer longer life and greater reliability. The problems of manufacturing heat exchangers suited to laminar flow are discussed. A method of manufacture is outlined that allows compact, modular design. Experience with this method of manufacture is described. Experimental results with a prototype heat exchanger bank are presented: these results show good agreement with theory at moderate levels of effectiveness (75--85%), but fall below predicted values at higher levels. It is argued that this discrepancy results from flow maldistribution. The problem of fouling and flow maldistribution are briefly discussed, and some possible applications are mentioned.

  6. 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.

  7. 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.

  8. Hartree potential dependent exchange functional

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Chemical exchange program analysis.

    SciTech Connect

    Waffelaert, Pascale

    2007-09-01

    As part of its EMS, Sandia performs an annual environmental aspects/impacts analysis. The purpose of this analysis is to identify the environmental aspects associated with Sandia's activities, products, and services and the potential environmental impacts associated with those aspects. Division and environmental programs established objectives and targets based on the environmental aspects associated with their operations. In 2007 the most significant aspect identified was Hazardous Materials (Use and Storage). The objective for Hazardous Materials (Use and Storage) was to improve chemical handling, storage, and on-site movement of hazardous materials. One of the targets supporting this objective was to develop an effective chemical exchange program, making a business case for it in FY07, and fully implementing a comprehensive chemical exchange program in FY08. A Chemical Exchange Program (CEP) team was formed to implement this target. The team consists of representatives from the Chemical Information System (CIS), Pollution Prevention (P2), the HWMF, Procurement and the Environmental Management System (EMS). The CEP Team performed benchmarking and conducted a life-cycle analysis of the current management of chemicals at SNL/NM and compared it to Chemical Exchange alternatives. Those alternatives are as follows: (1) Revive the 'Virtual' Chemical Exchange Program; (2) Re-implement a 'Physical' Chemical Exchange Program using a Chemical Information System; and (3) Transition to a Chemical Management Services System. The analysis and benchmarking study shows that the present management of chemicals at SNL/NM is significantly disjointed and a life-cycle or 'Cradle-to-Grave' approach to chemical management is needed. This approach must consider the purchasing and maintenance costs as well as the cost of ultimate disposal of the chemicals and materials. A chemical exchange is needed as a mechanism to re-apply chemicals on site. This will not only reduce the quantity of

  14. Crystal structure of an ethylene sorption complex of fully vacuum-dehydrated fully Ag+-exchanged zeolite X (FAU). Silver atoms have reduced ethylene to give CH2 2- carbanions at framework oxide vacancies.

    PubMed

    Lee, Young Mi; Choi, Seo Jung; Kim, Yang; Seff, Karl

    2005-11-03

    The crystal structure of an ethylene sorption complex of fully vacuum-dehydrated fully Ag(+)-exchanged zeolite X (FAU), a = 24.865(2) A, has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd at 21 degrees C. It is very different from the ethylene complex of Ag(92)-X that had been dehydrated at 400 degrees C in flowing oxygen, as were the two dehydrated structures. The crystal was prepared by ion exchange in a flowing stream of aqueous 0.05 M AgNO(3) for 3 days, followed by dehydration at 400 degrees C and 2 x 10(-6) Torr for 2 days, followed by exposure to 300 Torr of zeolitically dry ethylene gas for 2 h at 21 degrees C. The structure was determined in this atmosphere and was refined using all data to the final error indices (based upon the 534 reflections for which F(o) > 4sigma(F(o))) R(1) = 0.062 and wR(2) = 0.135. In this structure, per unit cell, 14 Ag(+) ions were found at the octahedral site I (Ag-O = 2.611(9) A), and 32 partially reduced Ag(+) ions fill two different site I' positions deep in the sodalite cavities (Ag-O = 2.601(13) and 2.618(12) A). The sodalite cavities host two different cationic silver clusters. In about 47% of sodalite units, eight silver atoms form interpenetrating tetrahedra, Ag(8)(n+) (n = 4 is suggested), with T(d)() symmetry. The other 53% of the sodalite units host cyclo-Ag(4)(m+) (m = 2 is suggested) cations with near S(4) symmetry. These clusters are very similar to those in vacuum-dehydrated Ag(92)-X. Thirty-two Ag(+) ions fill the single 6-rings, 15 at site II' (Ag-O = 2.492(10) A), and 17 at site II (Ag-O = 2.460(9) A). The latter 17 lie in supercages where each forms a lateral pi-complex with an ethylene molecule. In turn, each C(2)H(4) molecule forms two cis electrostatic hydrogen bonds to framework oxygens. The remaining 14 Ag+ ions occupy three different II' sites. Vacuum dehydration had caused substantial decomposition: per unit cell, 30 of the 92 Ag(+) ions were reduced and 15

  15. Advanced heat exchanger development for molten salts

    DOE PAGES

    Sabharwall, Piyush; Clark, Denis; Glazoff, Michael; ...

    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

  16. 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.

  17. 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,…

  18. Numerical simulation of heat exchanger

    SciTech Connect

    Sha, W.T.

    1985-01-01

    Accurate and detailed knowledge of the fluid flow field and thermal distribution inside a heat exchanger becomes invaluable as a large, efficient, and reliable unit is sought. This information is needed to provide proper evaluation of the thermal and structural performance characteristics of a heat exchanger. It is to be noted that an analytical prediction method, when properly validated, will greatly reduce the need for model testing, facilitate interpolating and extrapolating test data, aid in optimizing heat-exchanger design and performance, and provide scaling capability. Thus tremendous savings of cost and time are realized. With the advent of large digital computers and advances in the development of computational fluid mechanics, it has become possible to predict analytically, through numerical solution, the conservation equations of mass, momentum, and energy for both the shellside and tubeside fluids. The numerical modeling technique will be a valuable, cost-effective design tool for development of advanced heat exchangers.

  19. Handbook on heat exchangers

    NASA Astrophysics Data System (ADS)

    Bazhan, Pavel I.; Kanevets, Georgii E.; Seliverstov, Vladimir M.

    Essential data on heat exchange equipment used in ship, locomotive, automotive, and aircraft powerplants are presented in a systematic manner. The data cover the principal types and technical and performance characteristics of heat exchangers, fundamentals of the theory of heat exchange, calculation of heat transfer coefficients for different types of heat exchange apparatus, optimization of heat exchangers, computer-aided design of heat exchange equipment, testing techniques, and test result processing.

  20. 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.

  1. Exchange frequency in replica exchange molecular dynamics

    NASA Astrophysics Data System (ADS)

    Sindhikara, Daniel; Meng, Yilin; Roitberg, Adrian E.

    2008-01-01

    The effect of the exchange-attempt frequency on sampling efficiency is studied in replica exchange molecular dynamics (REMD). We show that sampling efficiency increases with increasing exchange-attempt frequency. This conclusion is contrary to a commonly expressed view in REMD. Five peptides (1-21 residues long) are studied with a spectrum of exchange-attempt rates. Convergence rates are gauged by comparing ensemble properties between fixed length test REMD simulations and longer reference simulations. To show the fundamental correlation between exchange frequency and convergence time, a simple model is designed and studied, displaying the same basic behavior of much more complex systems.

  2. Modelling of the effect of dislocation channel on intergranular microcrack nucleation in pre-irradiated austenitic stainless steels during low strain rate tensile loading

    NASA Astrophysics Data System (ADS)

    Evrard, Pierre; Sauzay, Maxime

    2010-10-01

    In the present article, the effect of dislocation channel on intergranular microcrack nucleation during the tensile deformation of pre-irradiated austenitic stainless steels is studied. Because several slip planes are activated within the dislocation channel, the simple dislocation pile-up model seems not well suited to predict grain boundary stress field. Finite element computations, using crystal plasticity laws and meshes including a channel of finite thickness, are also performed in order to study the effect of some microstructural characteristics on grain boundary stress field. Numerical results show that: the thickness and the length of the dislocation channel influence strongly the grain boundary normal stress field. The grain boundary orientation with respect the stress axis does not affect so much the grain boundary normal stresses close to the dislocation channel. On the contrary far away the dislocation channel, the grain boundary stress field depends on the grain boundary orientation. Based on these numerical results, an analytical model is proposed to predict grain boundary stress fields. It is valuable for large ranges of dislocation channel thickness, length as well as applied stress. Then, a macroscopic microcrack nucleation criterion is deduced based on the elastic-brittle Griffith model. The proposed criterion predicts correctly the influence of grain boundary characteristics (low-angle boundaries (LABs), non-coincident site lattice (non-CSL) high-angle boundaries (HABs), special grain boundaries (GBs)) on intergranular microcrack nucleation and the macroscopic tensile stress required for grain boundary microcrack nucleation for pre-irradiated austenitic stainless steels deformed in argon environment. The criterion based on a dislocation pile-up model (Smith and Barnby) underestimates strongly the nucleation stress. These results confirm that pile-up models are not well suited to predict microcrack nucleation stress in the case of dislocation

  3. The Gibbs-Thomson effect and intergranular melting in ice emulsions: Interpreting the anomalous heat capacity and volume of supercooled water

    NASA Astrophysics Data System (ADS)

    Johari, G. P.

    1997-12-01

    Calculations for the Gibbs-Thomson effect and the intergranular melting of the ice droplets in (water) emulsions at temperatures below 273.16 K show that water and ice coexist at thermodynamic equilibrium in an apparently frozen emulsion. The fraction of water at this equilibrium increases on heating, which alters further the thermodynamic properties of the emulsion. As some of the ice in the emulsion has already melted, the increase in the enthalpy, H, and heat capacity, Cp, and the decrease in the volume measured on the normal melting at 273.16 K, are less than the values anticipated. The ratio of this increase in H, or Cp, on melting of the emulsion to the corresponding value for pure ice, underestimates the emulsion's water content which, when used for scaling the difference between the Cp of the unfrozen and frozen emulsion at lower temperatures, as in earlier studies, leads to a larger Cp of supercooled water than the actual value. Similar scaling of the corresponding difference between the volume leads to higher volume, or lower density, than the actual value. A formalism for this premelting effect is given for both the adiabatic and differential scanning calorimetry (DSC), and its magnitude is calculated. New experiments show that the rise in the DSC signal, or equivalently in the apparent Cp observed on heating the frozen emulsion, occurs over a temperature range much wider than the Gibbs-Thomson effect and intergranular melting predict, for which reasons are given. It is shown that Cp of the dispersant phase is also affected by the melting of ice droplets. There are four consequences of the premelting effects for all finely dispersed materials, for frozen water emulsions below 273.16 K: (i) water and ice coexist in the emulsion, (ii) its apparent Cp will increase with increase in the heat input used to measure it, (iii) the apparent Cp will increase with decrease in the average size of the droplets, and (iv) the apparent Cp will decrease on annealing the

  4. Improvement in coercivity, thermal stability, and corrosion resistance of sintered Nd-Fe-B magnets with Dy80Ga20 intergranular addition

    NASA Astrophysics Data System (ADS)

    Zhou, Beibei; Li, Xiangbin; Cao, Xuejing; Yan, Gaolin; Yan, Aru

    2016-11-01

    To investigate the coercivity, corrosion resistance, and thermal stability of Nd-Fe-B magnets, their properties were investigated at room and high temperature before and after doping with Dy80Ga20 (at.%) powder. The coercivity of the magnets increased from the undoped value of 12.72 kOe to a doped value of 21.44 kOe. A micro-structural analysis indicates that a well-developed core-shell structure forms in the magnets doped with Dy80Ga20 powder. The improvement in magnetic properties is believed to be related to the refined and uniform matrix grains, continuous grain boundaries, and a hardened (Nd, Dy)2Fe14B shell surrounding the matrix grains. Additionally, the doped magnets exhibit an obvious improvement in thermal stability. For the magnets with added Dy80Ga20 powder, the temperature coefficients of remanence (α) and coercivity (β) increased to -0.106% °C-1 and -0.60% °C-1 over the range 20-100 °C, compared to temperature coefficients of -0.117% °C-1 (α) and -0.74% °C-1 (β) in the regular magnets without Dy80Ga20 powder. The irreversible loss of magnetic flux (Hirr) was investigated at different temperatures. After being exposed to 150 °C for 2 h, the Hirr of magnets with 4 wt.% Dy80Ga20 decreased by ˜95% compared to that of the undoped magnets. The enhanced temperature coefficients and Hirr indicate improved thermal stability in the doped Nd-Fe-B magnets. The intergranular addition of Dy80Ga20 also improved the corrosion resistance of the magnets because of the enhanced intergranular phase. In a corrosive atmosphere for 96 h, the mass loss of the sintered magnets with 4 wt.% Dy80Ga20 was 2.68 mg/cm2, less than 10% of that suffered by the undoped magnets (28.1 mg/cm2). Project supported by the Ministry of Science and Technology of China (Grant Nos. 2014DFB50130 and 2011CB612304) and the National Natural Science Foundation of China (Grant Nos. 51172168 and 51072139).

  5. 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.

  6. Woven heat exchanger

    DOEpatents

    Piscitella, Roger R.

    1987-01-01

    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.

  7. 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.

  8. SPECTRO-POLARIMETRIC SIMULATIONS OF THE SOLAR LIMB: ABSORPTION-EMISSION Fe I 6301.5 Å AND 6302.5 Å LINE PROFILES AND TORSIONAL FLOWS IN THE INTERGRANULAR MAGNETIC FLUX CONCENTRATIONS

    SciTech Connect

    Shelyag, S.

    2015-03-01

    Using radiative magnetohydrodynamic simulations of the magnetized solar photosphere and detailed spectro-polarimetric diagnostics with the Fe I 6301.5 Å and 6302.5 Å photospheric lines in the local thermodynamic equilibrium approximation, we model active solar granulation as if it was observed at the solar limb. We analyze general properties of the radiation across the solar limb, such as the continuum and the line core limb darkening and the granulation contrast. We demonstrate the presence of profiles with both emission and absorption features at the simulated solar limb, and pure emission profiles above the limb. These profiles are associated with the regions of strong linear polarization of the emergent radiation, indicating the influence of the intergranular magnetic fields on the line formation. We analyze physical origins of the emission wings in the Stokes profiles at the limb, and demonstrate that these features are produced by localized heating and torsional motions in the intergranular magnetic flux concentrations.

  9. 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.

  10. 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.

  11. Contribution of solution pH and buffer capacity to suppress intergranular stress corrosion cracking of sensitized type 304 stainless steel at 95 C

    SciTech Connect

    Zhang, S.; Shibata, T.; Haruna, T. . Dept. of Materials Science and Processing)

    1999-05-01

    Controlling pH of high-temperature water to [approximately]pH 7 at 300 C by adding lithium hydroxide (LiOH) into the coolant system of a pressurized water reactor (PWR) successfully has been mitigating the corrosion of PWR component materials. The effects of solution pH and buffer capacity on intergranular stress corrosion cracking (IGSCC) of sensitized type 304 stainless steel ([SS] UNS S30400) was examined at 95 C by slow strain rate technique (SSRT) with an in-situ cracking observation system. It was found that an increase in solution pH or buffer capacity increased crack initiation time and decreased mean crack initiation frequency, but exerted almost no effect on crack propagation. This inhibition effect on IGSCC initiation was explained as resulting from a retarding effect of solution pH and buffer capacity on the decrease in pH at crack nuclei caused by the hydrolysis of metal ions dissolved when the passive film was ruptured by strain in SSRT.

  12. Intergranular pinning potential and critical current in the magnetic superconductor Ru Sr2 Gd1.5 Ce0.5 Cu2 O10

    NASA Astrophysics Data System (ADS)

    Das Virgens, M. G.; García, S.; Continentino, M. A.; Ghivelder, L.

    2005-02-01

    The intergranular pinning potential U and the critical current density JC for polycrystalline RuSr2Gd1.5Ce0.5Cu2O10 ruthenate-cuprate were determined at zero magnetic field and temperature through the frequency shift in the peak of the imaginary part of the ac magnetic susceptibility, χ″ . A critical state model, including a flux creep term, was found to accurately describe the χ″ behavior. The obtained values, U(H=0,T=0)≅30meV and JC(H=0,T=0)≅110A/cm2 are about two orders of magnitude and four times lower, respectively, in comparison with the high- TC cuprate YBa2Cu3O7 . These results were ascribed to the effects of the Ru magnetization on the connectivity of the weak-linked network, giving an intrinsic local field at the junctions of ˜15Oe . The impact on JC is less intense because of the small average grain radius (˜1μm) . The intragranular London penetration length at T=0[λL(0)≅2μm] was derived using a Kim-type expression for the field dependence of JC . A possible source for the large value of λL in comparison to the high- Tc cuprates is suggested to come from a strong intragrain granularity, due to structural domains of coherent-rotated RuO6 octahedra separated by antiphase boundaries.

  13. Suppression of thiol exchange reaction in the determination of reduced-form thiols by high-performance liquid chromatography with fluorescence detection after derivatization with fluorogenic benzofurazan reagent, 7-fluoro-2,1,3-benzoxadiazole-4-sulfonate and 4-aminosulfonyl-7-fluoro-2,1,3-benzoxadiazole.

    PubMed

    Santa, Tomofumi; Aoyama, Chiaki; Fukushima, Takeshi; Imai, Kazuhiro; Funatsu, Takashi

    2006-01-01

    The derivatization of the reduced-form thiols with SBD-F (7-fluoro-2,1,3-benzoxadiazole-4-sulfonate) and ABD-F (4-aminosulfonyl-7-fluoro-2,1,3-benzoxadiazole) was studied. The yields of the derivatives of the reduced-form thiols (cysteine, homocysteine, reduced-form glutathione) with SBD-F at 60 degrees C for 45 min in the borate buffer (pH 9.3) were significantly decreased in the presence of the oxidized-form thiols (cystine, homocystine, oxidized-form glutathione) because of the thiol exchange reaction between the reduced-form and the oxidized-form thiols. The use of ABD-F at low temperature enabled the suppression of these thiol exchange reactions, and the recommended conditions were below 5 degrees C for 90 min in borate buffer (pH 9.3). These results suggest that ABD-F is a preferred derivatization reagent for the accurate determination of the reduced-form thiols in samples containing the oxidized-form thiols. In addition, it was also suggested that the derivatization of the reduced-form thiols should also be performed at low temperature when derivatization reagents such as o-phthalaldehyde (OPA) and monobromobimane (BrB) are used.

  14. 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.

  15. 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.; 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

  16. Industrial heat exchangers

    SciTech Connect

    Hayes, A.J.; Liang, W.W.; Richlen, S.L.; Tabb, E.S.

    1985-01-01

    This book presents the papers given at a symposium on the use of heat exchangers in the industrial plants. Topics considered include the US DOE and GRI research programs, advanced fixed boundary heat exchanger technology, commercial heat exchanger applications, thermo-hydraulic performance of heat-transfer equipment, field tests, the corrosion of heat exchanger materials, economics, cost benefit analysis, payback, and advanced assembly and materials.

  17. [Plasma exchange in nephrology: Indications and technique].

    PubMed

    Ridel, Christophe; Kissling, Sébastien; Mesnard, Laurent; Hertig, Alexandre; Rondeau, Éric

    2017-02-01

    Plasma exchange is a non-selective apheresis technique that can be performed by filtration or centrifugation allowing rapid purification of high molecular weight pathogens. An immunosuppressive treatment is generally associated to reduce the rebound effect of the purified substance. Substitution solutes such as human albumin and macromolecules are needed to compensate for plasma extraction. Compensation by viro-attenuated plasma is reserved solely for the treatment of thrombotic microangiopathies or when there is a risk of bleeding, because this product is very allergenic and expensive. The treatment goal for a plasma exchange session should be between one and one and one-half times the patient's plasma volume estimated at 40 mL/kg body weight. The anticoagulation is best ensured by the citrate. Complications of plasma exchange are quite rare according to the French hemapheresis registry. The level of evidence of efficacy of plasma exchange in nephrology varies from one pathology to another. Main indications of plasma exchange in nephrology are Goodpasture syndrome, antineutrophil cytoplasmic antibody vasculitis when plasma creatinine is greater than 500 μmol/L, and thrombotic microangiopathies. During renal transplantation, plasma exchange may be proposed in the context of human leukocyte antigen (HLA) desensitization protocols or ABO-incompatible graft. After renal transplantation, plasma exchange is indicated as part of the treatment of acute humoral rejection or recurrent focal segmental glomerulosclerosis on the graft. Plasma exchanges are also proposed in the management of cryoglobulinemia or polyarteritis nodosa. Hemodialysis with membranes of very high permeability tends to replace plasma exchange for myeloma nephropathy. The benefit from plasma exchange has not been formally demonstrated for the treatment of severe lupus or antiphospholipid antibody syndrome. There is no indication of plasma exchange in the treatment of scleroderma or nephrogenic

  18. Exchange-coupled perpendicular media

    NASA Astrophysics Data System (ADS)

    Suess, D.; Lee, J.; Fidler, J.; Schrefl, T.

    2009-03-01

    The potential of exchange spring bilayers and graded media is reviewed. An analytical model for the optimization of graded media gives an optimal value of the magnetic polarization of Js=0.8 T. The optimum design allows for thermally stable grains with grain diameters in the order of 3.3 nm, which supports ultra-high density up to 5-10 Tbit/in 2. The switching field distribution is significantly reduced in bilayer media and graded media compared to single-phase media. For the graded media the switching field distribution is reduced by about a factor of two. For bilayer media the minimum switching field distribution is obtained for soft-layer anisotropies that are about one fifth of the hard-layer anisotropy. The influence of precessional switching on the reversal time and the reversal field is investigated in detail for magnetic bilayers. Exchange spring bilayers can be reversed with field pulses of 20 ps.

  19. Approximate strip exchanging.

    PubMed

    Roy, Swapnoneel; Thakur, Ashok Kumar

    2008-01-01

    Genome rearrangements have been modelled by a variety of primitives such as reversals, transpositions, block moves and block interchanges. We consider such a genome rearrangement primitive Strip Exchanges. Given a permutation, the challenge is to sort it by using minimum number of strip exchanges. A strip exchanging move interchanges the positions of two chosen strips so that they merge with other strips. The strip exchange problem is to sort a permutation using minimum number of strip exchanges. We present here the first non-trivial 2-approximation algorithm to this problem. We also observe that sorting by strip-exchanges is fixed-parameter-tractable. Lastly we discuss the application of strip exchanges in a different area Optical Character Recognition (OCR) with an example.

  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. 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

  2. Theoretical study of the elasticity, mechanical behavior, electronic structure, interatomic bonding, and dielectric function of an intergranular glassy film model in prismatic β-Si3N4

    NASA Astrophysics Data System (ADS)

    Ching, W. Y.; Rulis, Paul; Ouyang, Lizhi; Aryal, Sitaram; Misra, Anil.

    2010-06-01

    Microstructures such as intergranular glassy films (IGFs) are ubiquitous in many structural ceramics. They control many of the important physical properties of polycrystalline ceramics and can be influenced during processing to modify the performance of devices that contain them. In recent years, there has been intense research, both experimentally and computationally, on the structure and properties of IGFs. Unlike grain boundaries or dislocations with well-defined crystalline planes, the atomic scale structure of IGFs, their fundamental electronic interactions, and their bonding characteristics are far more complicated and not well known. In this paper, we present the results of theoretical simulations using ab initio methods on an IGF model in β-Si3N4 with prismatic crystalline planes. The 907-atom model has a dimension of 14.533Å×15.225Å×47.420Å . The IGF layer is perpendicular to the z axis, 16.4Å wide, and contains 72 Si, 32 N, and 124 O atoms. Based on this model, the mechanical and elastic properties, the electronic structure, the interatomic bonding, the localization of defective states, the distribution of electrostatic potential, and the optical dielectric function are evaluated and compared with crystalline β-Si3N4 . We have also performed a theoretical tensile experiment on this model by incrementally extending the structure in the direction perpendicular to the IGF plane until the model fully separated. It is shown that fracture occurs at a strain of 9.42% with a maximum stress of 13.9 GPa. The fractured segments show plastic behavior and the formation of surfacial films on the β-Si3N4 . These results are very different from those of a previously studied basal plane model [J. Chen , Phys. Rev. Lett. 95, 256103 (2005)10.1103/PhysRevLett.95.256103] and add insights to the structure and behavior of IGFs in polycrystalline ceramics. The implications of these results and the need for further investigations are discussed.

  3. The effect of inter-granular constraints on the response of polycrystalline piezoelectric ceramics at the surface and in the bulk

    NASA Astrophysics Data System (ADS)

    Hossain, Mohammad J.; Wang, Zhiyang; Khansur, Neamul H.; Kimpton, Justin A.; Oddershede, Jette; Daniels, John E.

    2016-08-01

    The electro-mechanical coupling mechanisms in polycrystalline ferroelectric materials, including a soft PbZrxTi1-xO3 (PZT) and lead-free 0.9375(Bi1/2Na1/2)TiO3-0.0625BaTiO3 (BNT-6.25BT), have been studied using a surface sensitive low-energy (12.4 keV) and bulk sensitive high-energy (73 keV) synchrotron X-ray diffraction with in situ electric fields. The results show that for tetragonal PZT at a maximum electric field of 2.8 kV/mm, the electric-field-induced lattice strain (ɛ111) is 20% higher at the surface than in the bulk, and non-180° ferroelectric domain texture (as indicated by the intensity ratio I002/I200) is 16% higher at the surface. In the case of BNT-6.25BT, which is pseudo-cubic up to fields of 2 kV/mm, lattice strains, ɛ111 and ɛ200, are 15% and 20% higher at the surface, while in the mixed tetragonal and rhombohedral phases at 5 kV/mm, the domain texture indicated by the intensity ratio, I 111 / I 11 1 ¯ and I002/I200, are 12% and 10% higher at the surface than in the bulk, respectively. The observed difference in the strain contributions between the surface and bulk is suggested to result from the fact that surface grains are not constrained in three dimensions, and consequently, domain reorientation and lattice expansion in surface grains are promoted. It is suggested that the magnitude of property difference between the surface and bulk is higher for the PZT than for BNT-6.25BT due to the level of anisotropy in the strain mechanism. The comparison of the results from different methods demonstrates that the intergranular constraints have a significant influence on the electric-field-induced electro-mechanical responses in polycrystalline ferroelectrics. These results have implications for the design of higher performance polycrystalline piezoelectrics.

  4. Comment on: ``Influence of inter-granular void ratio on monotonic and cyclic undrained shear response of sandy soils'' by M. Belkhatir, A. Arab, H. Missoum, T. Schanz [C. R. Mecanique 338 (2010) 290-303

    NASA Astrophysics Data System (ADS)

    Rahman, Md. Mizanur

    2011-01-01

    The authors should be commended for their interesting experimental work on sandy soils presented in Belkhatir et al. (2010) [1]. They used the inter-granular void ratio, e, to interpret the experimental results and developed some useful correlations with e. However, the Note fails to address the further development of e over a decade to a more generalized form of equivalent granular void ratio, e. This comment aims at adding missing literature on e and presents a re-interpretation of the experimental data based on e. The advantages of using e over e are significant and explained in subsequent sections.

  5. 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.

  6. 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.

  7. 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.

  8. 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…

  9. 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…

  10. 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…

  11. 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…

  12. 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.…

  13. The Children's Art Exchange.

    ERIC Educational Resources Information Center

    Stone, Nancy

    1989-01-01

    Describes Vermont's Art Exchange Program and its goal of sensitizing Soviet and U.S. children to the common humanity they share. Discusses this program's attempts to break down barriers of fear and stereotyping by promoting the exchange of art and writing between children. (KO)

  14. 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…

  15. 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…

  16. 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…

  17. Higher Education Exchange, 2004

    ERIC Educational Resources Information Center

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

    2004-01-01

    The Higher Education Exchange is part of a movement to strengthen higher education's democratic mission and foster a more democratic culture throughout American society. Working in this tradition, the Higher Education Exchange publishes case studies, analyses, news, and ideas about efforts within higher education to develop more democratic…

  18. 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.

  19. A single-center prospective study on the safety of plasma exchange procedures using a double-viral-inactivated and prion-reduced solvent/detergent fresh-frozen plasma as the replacement fluid in the treatment of thrombotic microangiopathy.

    PubMed

    Vendramin, Chiara; McGuckin, Siobhan; Alwan, Ferras; Westwood, John-Paul; Thomas, Mari; Scully, Marie

    2017-01-01

    Patients presenting with acute episodes of thrombotic microangiopathies (TMAs) require urgent access to plasma exchange (PEX). OctaplasLG, a solvent/detergent fresh-frozen plasma product that has undergone viral inactivation and prion reduction step, has been used in our institution since 2013, replacing Octaplas. We prospectively reviewed 981 PEX procedures where OctaplasLG was the replacement fluid in 90 patients admitted acutely with a TMA presentation within our institution from January 1, 2013, to December 31, 2015. We recorded citrate toxicities, plasma reactions, viral transfer, complications related to central venous catheter, and venous thrombotic events (VTEs). Citrate toxicities were 5.4%, plasma reactions were 2%, and all were classified as Grade 1 or 2. VTE had an incidence of 12.2%, although 50% of the episodes occurred in early remission when patients were not receiving PEX. No line insertions complications were recorded. Line-associated infections were 2.2%. Hepatitis B and C serology and human immunodeficiency virus (HIV) were checked on admission. There were four patients who may have had passive transient transfer of hepatitis B antibodies from pooled plasma. No hepatitis C or HIV viral transfer was documented after treatment and no seroconversion was detected after treatment. Our data have demonstrated that the incidence of complications during PEX is low and using OctaplasLG is comparable to the low incidence of reactions. No cases of anaphylaxis, transfusion-related acute lung injury, or fatal plasma reactions were seen. There was no evidence of viral transmission or seroconversion after treatment. © 2016 AABB.

  20. Development of a Thin Film Primary Surface Heat Exchanger for Advanced Power Cycles

    SciTech Connect

    Allison, Tim; Beck, Griffin; Bennett, Jeffrey; Hoopes, Kevin; Miller, Larry

    2016-06-29

    This project objective is to develop a high-temperature design upgrade for an existing primary surface heat exchanger so that the redesigned hardware is capable of operation in CO2 at temperatures up to 1,510°F (821°C) and pressure differentials up to 130 psi (9 bar). The heat exchanger is proposed for use as a recuperator in an advanced low-pressure oxy-fuel Brayton cycle that is predicted to achieve over 50% thermodynamic efficiency, although the heat exchanger could also be used in other high-temperature, low-differential pressure cycles. This report describes the progress to date, which includes continuing work performed to select and test new candidate materials for the recuperator redesign, final mechanical and thermal performance analysis results of various redesign concepts, and the preliminary design of a test loop for the redesigned recuperator including a budgetary estimate for detailed test loop design, procurement, and test operation. A materials search was performed in order to investigate high-temperature properties of many candidate materials, including high-temperature strength and nickel content. These properties were used to rank the candidate materials, resulting in a reduced list of nine materials for corrosion testing. Multiple test rigs were considered and analyzed for short-term corrosion testing and Thermal Gravimetric Analysis (TGA) was selected as the most cost-effective option for evaluating corrosion resistance of the candidate materials. In addition, tantalum, niobium, and chromium coatings were identified as potential options for increased corrosion resistance. The test results show that many materials exhibit relatively low weight gain rates, and that niobium and tantalum coatings may improve corrosion resistance for many materials, while chromium coatings appear to oxidize and debond quickly. Metallurgical analysis of alloys was also performed, showing evidence of intergranular attack in 282 that may cause long

  1. The impact of a needle exchange's closure.

    PubMed

    Broadhead, R S; van Hulst, Y; Heckathorn, D D

    1999-01-01

    The Windham, Connecticut, needle exchange closed in May 1997 after becoming embroiled in a public controversy in which it was blamed for the city's drug problem, discarded syringes, and even the economic decline of the city itself. The authors interviewed injection drug users and conducted a community survey of discarded drug paraphernalia to explore the effects of the needle exchange's closure. After the needle exchange was closed in March 1997, the authors re-recruited former participants in an AIDS prevention research project, the majority of whom were clients of the needle exchange. The authors analyzed responses from these respondents' pre-closure interviews and from III post-closure initial interviews and 78 post-closure follow-up interviews as well as data on discarded syringes and "dope bags". Following the closure of the needle exchange, significant increases were found in the percentage of respondents who reported an unreliable source as their primary source of syringes, in respondents' reports of the frequency of reusing syringes, and in the percentage of respondents who reported sharing of syringes. Surveys of outdoor drug-use areas found that the closure of the needle exchange did not reduce the volume of discarded syringes and other drug-injection debris. The problems in Windham that led to the closure of the exchange still remain, and the city's drug injectors are engaging in higher levels of HIV risk behavior.

  2. 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.

  3. 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 Stock Exchange, Inc.; National Stock Exchange, Inc.; Chicago Board Options Exchange, Incorporated; Order... (``ISE''),\\1\\ New York Stock Exchange LLC (``NYSE''), NYSE Amex LLC (``NYSEAmex''), NYSE Arca,...

  4. DIVALENT ION EXCHANGE WITH ALKALI

    SciTech Connect

    Bunge, A.L.; Klein, G.; Radke, C.J.

    1980-05-01

    Exchange of hardness ions is important in enhanced oil recovery with chemical additives. In both micellar-polymer and caustic flooding processes, multivalent ions released from rock surfaces can interact with anionic surfactants, rendering them preferentially oil soluble and/or insoluble in water. Because hardness cations are sparingly soluble and precipitate in alkaline solutions, such solutions may be more efficient as surfactant flood preflushes than are softened brines. Multivalent ion precipitation may also occur in alkaline waterflooding. To permit design of such processes, this paper presents a chromatographic theory for simultaneous ion exchange with precipitation of divalent ions. Theoretical effluent histories and concentration profiles are presented for the cases of finite pulses and continuous injection of hydroxide ions into linear cores. Complete capture of the insoluble salt particles is assumed. Results are given for the case of instantaneous equilibration of the solution with the precipitate, as well for the case of complete nonequilibrium, in which the solid precipitate does not redissolve. The efficiency of alklaine preflushing is shown to depend on the exchange isotherm, initial divalent loading of the rock, injected pH and salinity, the solubility product of the precipitated salt, and pulse size. The effect of slug size on complete equilibrium removal of hardness ions is reduced efficiency with increasing size until a critical volume approximating continuous injection is reached. Increasing injected pH and salinity provides a more favorable response. Experimental data for Berea sandstone and an argillaceous sand compare favorably with the proposed theory.

  5. 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.

  6. Heat and mass exchanger

    DOEpatents

    Lowenstein, Andrew [Princeton, NJ; Sibilia, Marc J [Princeton, NJ; Miller, Jeffrey A [Hopewell, NJ; Tonon, Thomas [Princeton, NJ

    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.

  7. Cryptographic Securities Exchanges

    NASA Astrophysics Data System (ADS)

    Thorpe, Christopher; Parkes, David C.

    While transparency in financial markets should enhance liquidity, its exploitation by unethical and parasitic traders discourages others from fully embracing disclosure of their own information. Traders exploit both the private information in upstairs markets used to trade large orders outside traditional exchanges and the public information present in exchanges' quoted limit order books. Using homomorphic cryptographic protocols, market designers can create "partially transparent" markets in which every matched trade is provably correct and only beneficial information is revealed. In a cryptographic securities exchange, market operators can hide information to prevent its exploitation, and still prove facts about the hidden information such as bid/ask spread or market depth.

  8. 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.

  9. Greywater heat exchanger

    SciTech Connect

    Holmberg, D.

    1983-11-21

    A kilowatt meter and water meter were installed to monitor pregreywater usage. The design considerations, the heat exchanger construction and installation, and the monitoring of usage levels are described.

  10. Exchange donor renal transplantation.

    PubMed

    Kim, Soo Jin; Kim, Myoung Soo; Park, Kiil

    2013-01-01

    Nearly 20 years of experience at Severance Hospital has shown that utilizing exchange donors increases the donor pool safely, with outcomes comparable to living related donor grafts. The exchange donor program is invaluable for incompatible donor-recipient pairs to consecutively proceed to transplantation. Recently, newer desensitization protocols have been devised to approach incompatible donor-recipient pairs, but not without risks. These desensitization protocols may be an alternative when confronting the limitations in the exchange program. Therefore, the exchange program and the desensitization protocols should be complementary, not competing strategies and centers should weigh the merits and limitations of each protocol in each incompatible donor-recipient pair to select the optimal method for a safe and successful transplantation.

  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. Microtube strip heat exchanger

    SciTech Connect

    Doty, F.D.

    1992-07-09

    The purpose of this contract has been to explore the limits of miniaturization of heat exchangers with the goals of (1) improving the theoretical understanding of laminar heat exchangers, (2) evaluating various manufacturing difficulties, and (3) identifying major applications for the technology. A low-cost, ultra-compact heat exchanger could have an enormous impact on industry in the areas of cryocoolers and energy conversion. Compact cryocoolers based on the reverse Brayton cycle (RBC) would become practical with the availability of compact heat exchangers. Many experts believe that hardware advances in personal computer technology will rapidly slow down in four to six years unless lowcost, portable cryocoolers suitable for the desktop supercomputer can be developed. Compact refrigeration systems would permit dramatic advances in high-performance computer work stations with conventional'' microprocessors operating at 150 K, and especially with low-cost cryocoolers below 77 K. NASA has also expressed strong interest in our MTS exchanger for space-based RBC cryocoolers for sensor cooling. 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.

  13. Compact, super heat exchanger

    NASA Technical Reports Server (NTRS)

    Fortini, A.; Kazaroff, J. M.

    1980-01-01

    Heat exchanger uses porous media to enhance heat transfer through walls of cooling channels, thereby lowering wall temperature. Porous media within cooling channel increases internal surface area from which heat can be transferred to coolant. Comparison data shows wall has lower temperature and coolant has higher temperature when porous medium is used within heat exchanger. Media can be sintered powedered metal, metal fibers, woven wire layers, or any porous metal having desired permeability and porosity.

  14. Microtube strip heat exchanger

    NASA Astrophysics Data System (ADS)

    Doty, F. D.

    1990-12-01

    Doty Scientific (DSI) believes their microtube-strip heat exchanger will contribute significantly to the following: (1) the closed Brayton cycles being pursued at MIT, NASA, and elsewhere; (2) reverse Brayton cycle cryocoolers, currently being investigated by NASA for space missions, being applied to MRI superconducting magnets; and (3) high-efficiency cryogenic gas separation schemes for CO2 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 percent and relative pressure drops below 0.1 percent 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 to 10 prototype MTS heat exchangers; test prototype MTS heat exchanger; and verify test through independent means.

  15. Compact, super heat exchanger

    NASA Technical Reports Server (NTRS)

    Fortini, A.; Kazaroff, J. M.

    1980-01-01

    Heat exchanger uses porous media to enhance heat transfer through walls of cooling channels, thereby lowering wall temperature. Porous media within cooling channel increases internal surface area from which heat can be transferred to coolant. Comparison data shows wall has lower temperature and coolant has higher temperature when porous medium is used within heat exchanger. Media can be sintered powedered metal, metal fibers, woven wire layers, or any porous metal having desired permeability and porosity.

  16. 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)

  17. 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.

  18. 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.

  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. 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…

  1. WICHE's PSEP: Professional Student Exchange Program

    ERIC Educational Resources Information Center

    Western Interstate Commission for Higher Education, 2010

    2010-01-01

    The Western Interstate Commission for Higher Education (WICHE) has been providing Western residents with "affordable access to the healthcare professions" for more than 55 years through its Professional Student Exchange Program (PSEP). If an individual enrolls through WICHE's PSEP, he pays reduced tuition at out-of-state public and…

  2. Unusual attempt to direct the growth of bimetallic Ag@Pt nanorods on electrochemically reduced graphene oxide nanosheets by electroless exchange of Cu by Pt for an efficient alcohol oxidation

    NASA Astrophysics Data System (ADS)

    Jeena, S. E.; Gnanaprakasam, P.; Selvaraju, T.

    2017-01-01

    A simple and an efficient tool for the direct growth of bimetallic Ag@Pt nanorods (NRDs) on electrochemically reduced graphene oxide (ERGO) nanosheets was developed at glassy carbon electrode (GCE). Initially, Cu shell was grown on Ag core as Ag@Cu NRD by the seed-mediated growth method. Accordingly, Cu shell has been successfully replaced by Pt using the electroless galvanic replacement method with ease by effective functionalization of L-tryptophan on ERGO surface (L-ERGO), which eventually plays an important role in the direct growth of one-dimensional bimetallic NRDs. As a result, the synthesized Ag@Pt NRD-supported L-ERGO nanosheets (Ag@Pt NRDs/L-ERGO/GCE) were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDAX) and Raman spectroscopy. Anodic stripping voltammetry was used to explore its electrochemical properties. Finally, the developed bimetallic Ag@Pt NRDs/L-ERGO/GCEs were studied as a better electrocatalyst compared to the commercial catalysts such as Pt40/C or Pt20/C-loaded electrode for the oxidation of ethanol or methanol with a high tolerance level and an enhanced current density. In addition, the long-term stability was studied using chronoamperometry for 1000 s at the bimetallic NRD electrode for alcohol oxidation which impedes the fouling properties. The unfavourable and favourable electrooxidation of ethanol at Ag@Cu NRDs/L-ERGO/GCE (a) and Ag@Pt NRDs/L-ERGO/GCE (b) is discussed. The synergistic effect of Ag core and catalytic properties of Pt shell at Ag@Pt NRDs/L-ERGO/GCE tend to strongly minimize the CO poisoning effect and enhanced ethanol electrooxidation.

  3. 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.

  4. 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.

  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 summary herein.

  6. 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.

  7. 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.

  8. 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).

  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. Better refrigerant exchanger design

    SciTech Connect

    Starczewski, J.

    1985-04-01

    Design methods are presented for freon refrigerant evaporators of a horizontal tubular heat exchanger type. This article is in two parts. The first part deals with refrigerants on the shell side while the second deals with refrigerants on the tube side. The currently used LMTD to calculate surface area with refrigerants boiling inside (or outside) tubes will be shown to be incorrect. Instead, a new concept of mean average heat flux is introduced. The article also proves that the boiling refrigerant heat transfer coefficient varies considerably along heat exchangers.

  11. Dependable Software Technology Exchange

    DTIC Science & Technology

    1993-06-01

    Special Report CMU/SEI-93-SR-04 S~Carnegie-Melion University Software Engineering Institute AD-A267 103 DTIC D•epWebleoftware JEL ECT3 E9 Technology ...16590 ___________ lull! !! l1111 U l111 I lil I --\\t• /" Special Report CMU/SEI-93-SR-04 June 1993 Dependable Software Technology Exchange Charles B...93-SR-4 Dependable Software Technology Exchange Abstract: On March 18 and 19, 1993, the Dependable Real-Time Software project hosted a Dependable

  12. 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.

  13. 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.

  14. Probe Measures Fouling As In Heat Exchangers

    NASA Technical Reports Server (NTRS)

    Marner, Wilbur J.; Macdavid, Kenton S.

    1990-01-01

    Combustion deposits reduce transfer of heat. Instrument measures fouling like that on gas side of heat exchanger in direct-fired boiler or heat-recovery system. Heat-flux probe includes tube with embedded meter in outer shell. Combustion gases flow over probe, and fouling accumulates on it, just as fouling would on heat exchanger. Embedded heat-flow meter is sandwich structure in which thin Chromel layers and middle alloy form thermopile. Users determine when fouling approaches unacceptable levels so they schedule cleaning and avoid decreased transfer of heat and increased drop in pressure fouling causes. Avoids cost of premature, unnecessary maintenance.

  15. 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.

  16. Copper-Exchanged Zeolite L Traps Oxygen

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K.; Seshan, Panchalam K.

    1991-01-01

    Brief series of simple chemical treatments found to enhance ability of zeolite to remove oxygen from mixture of gases. Thermally stable up to 700 degrees C and has high specific surface area which provides high capacity for adsorption of gases. To increase ability to adsorb oxygen selectively, copper added by ion exchange, and copper-exchanged zeolite reduced with hydrogen. As result, copper dispersed atomically on inner surfaces of zeolite, making it highly reactive to oxygen, even at room temperature. Reactivity to oxygen even greater at higher temperatures.

  17. 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.

  18. Probe Measures Fouling As In Heat Exchangers

    NASA Technical Reports Server (NTRS)

    Marner, Wilbur J.; Macdavid, Kenton S.

    1990-01-01

    Combustion deposits reduce transfer of heat. Instrument measures fouling like that on gas side of heat exchanger in direct-fired boiler or heat-recovery system. Heat-flux probe includes tube with embedded meter in outer shell. Combustion gases flow over probe, and fouling accumulates on it, just as fouling would on heat exchanger. Embedded heat-flow meter is sandwich structure in which thin Chromel layers and middle alloy form thermopile. Users determine when fouling approaches unacceptable levels so they schedule cleaning and avoid decreased transfer of heat and increased drop in pressure fouling causes. Avoids cost of premature, unnecessary maintenance.

  19. 75 FR 52558 - Self-Regulatory Organizations; BATS Exchange, Inc.; Chicago Board Options Exchange, Incorporated...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-26

    ... From the Federal Register Online via the Government Publishing Office ] SECURITIES AND EXCHANGE...; BATS Exchange, Inc.; Chicago Board Options Exchange, Incorporated; Chicago Stock Exchange, Inc.; EDGA Exchange, Inc.; EDGX Exchange, Inc.; Financial Industry Regulatory Authority, Inc.; International...

  20. Exchange functionals and potentials

    NASA Astrophysics Data System (ADS)

    Neumann, Ralf; Nobes, Ross H.; Handy, Nicholas C.

    The commonly used exchange-correlation functionals of density functional theory and their potentials are examined numerically following the first such investigation by Perdew. They are also investigated for Ne and Kr. Their behaviour for large gradients of the density and for large distances is not satisfactory. In particular, the correct asymptotic r-1 behaviour is difficult to achieve. Following van Leeuwen and Baerends, this is linked to the energy ɛmax of the highest occupied orbital arising from the Kohn-Sham equations. This deficiency is linked also with the poor prediction of molecular polarizabilities. The Becke-Roussel (BR) exchange functional is examined, which is derived by assuming a hydrogen-like exchange hole at all spatial points, and it has the attraction of being dependent on both the kinetic energy density and the Laplacian of the density and has no adjustable parameters. Becke has presented encouraging results using this functional in a hybrid manner. Fully self-consistent Kohn-Sham calculations are performed using it in combination with Perdew's 1986 correlation functional. The results are very encouraging indeed, so much so that this exchange functional is the best generalized gradient approximation (GGA) yet discovered. In particular, bond lengths of many molecular show a substantial improvement over results from other GGAs. For example, many CH bonds are now within experimental accuracy, instead of being typically 0·02 Å too long. Our ab initio understanding of non-dynamic correlation and dynamic correlation is then linked with density functional theory. It is argued that correlation functionals should pick up the local dynamic correlation, whereas exchange functionals should include non-dynamic correlation effects. For these reasons it is considered that exchange functionals are best modelled on a system for which there is effectively no non-dynamic correlation, for which the optimum example is the Ne atom. Thus, again following Becke and

  1. 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…

  2. 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…

  3. 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.

  4. Conquer heat exchanger fouling

    SciTech Connect

    Mukherjee, R.

    1996-01-01

    Fouling plays a dominant role in heat exchanger performance. It is extremely important to choose the most appropriate type of heat exchanger for a particular application and adopt proper values for fouling resistance. A design practice for shell-and-tube heat exchangers that will limit fouling to a minimum and thus ensure trouble-free operation is essential. Due to the availability of specialized software, the thermal design of heat exchangers has become precise and scientific. The results occasionally have to be tempered with practical experience and engineering judgment, but generally these computer programs are very reliable and authentic. However, the above is true only for determining heat-transfer coefficients and pressure drop. One important area that cannot possibly be addressed by design software is fouling. While a proper selection of fouling resistance is extremely difficult due to the numerous factors involved, a sound design practice will minimize any errors. However, it is important to first understand the phenomenon of fouling. The paper describes what fouling is, types of fouling, factors affecting fouling, providing a fouling allowance, selecting a fouling resistance, and overcoming fouling through better design.

  5. 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.

  6. 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…

  7. Organizing Equity Exchanges

    NASA Astrophysics Data System (ADS)

    Schaper, Torsten

    In the last years equity exchanges have diversified their operations into business areas such as derivatives trading, post-trading services, and software sales. Securities trading and post-trading are subject to economies of scale and scope. The integration of these functions into one institution ensures efficiency by economizing on transactions costs.

  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. 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…

  10. 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…

  11. 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…

  12. 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)

  13. 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…

  14. 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,…

  15. Microtube strip heat exchanger

    NASA Astrophysics Data System (ADS)

    Doty, F. D.

    1991-04-01

    During the last quarter, Doty Scientific, Inc. (DSI) continued to make progress on the microtube strip (MTS) heat exchangers. The team has begun a heat exchanger stress analysis; however, they have been concentrating the bulk of their analytical energies on a computational fluid dynmaics (CFD) model to determine the location and magnitude of shell-side flow maldistribution which decreases heat exchanger effectiveness. DSI received 120 fineblanked tubestrips from Southern Fineblanking (SFB) for manufacturing process development. Both SFB and NIST provided inspection reports of the tubestrips. DSI completed the tooling required to encapsulate a tube array and press tubestrips on the array. Pressing the tubestrips on tube arrays showed design deficiencies both in the tubestrip design and the tooling design. DSI has a number of revisions in process to correct these deficiencies. The research effort has identified a more economical fusible alloy for encapsulating the tube array, and determined the parameters required to successfully encapsulate the tube array with the new alloy. A more compact MTS heat exchanger bank was designed.

  16. Convection and interfacial mass exchange

    NASA Astrophysics Data System (ADS)

    Colinet, P.; Legros, J. C.; Dauby, P. C.; Lebon, G.; Bestehorn, M.; Stephan, P.; Tadrist, L.; Cerisier, P.; Poncelet, D.; Barremaecker, L.

    2005-10-01

    Mass-exchange through fluid interfaces is ubiquitous in many natural and industrial processes. Yet even basic phase-change processes such as evaporation of a pure liquid are not fully understood, in particular when coupled with fluid motions in the vicinity of the phase-change interface, or with microscopic physical phenomena in the vicinity of a triple line (where the interface meets a solid). Nowadays, many industries recognise that this lack of fundamental knowledge is hindering the optimisation of existing processes. Their modelling tools are too dependent on empirical correlations with a limited - and often unknown - range of applicability. In addition to the intrinsic multiscale nature of the phenomena involved in typical industrial processes linked to interfacial mass exchange, their study is highly multi-disciplinary, involving tools and techniques belonging to physical chemistry, chemical engineering, fluid dynamics, non-linear physics, non-equilibrium thermodynamics, chemistry and statistical physics. From the experimental point of view, microgravity offers a unique environment to obtain valuable data on phase-change processes, greatly reducing the influence of body forces and allowing the detailed and accurate study of interfacial dynamics. In turn, such improved understanding leads to optimisation of industrial processes and devices involving phase-change, both for space and ground applications.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Reduce FCCU fouling

    SciTech Connect

    Barlow, R.C.

    1986-07-01

    Fouling of equipment in fluid catalytic cracking units can significantly affect unit operation by reducing the necessary transfer of heat in heat exchangers, by restricting unit thruput due to increased pressure drop and, in general, by reducing the overall operating efficiency of the production unit. A loss in heat transfer can result in increased fuel costs to operate the unit or may affect product separation when the lost heat cannot be replaced by other means. The physical restriction of flow can cause production limitations due to increased pressure drop in the system. Pumparound or recycle stream flows may have to be reduced, which will affect heat recovery and product separation. Pluggage in the separation towers can also restrict necessary separation efficiencies and subsequent product separation. The overall unit performance can be adversely affected, even when the flexibility of unit operations exists to compensate for the effects of fouling.

  5. 78 FR 5236 - Self-Regulatory Organizations; National Stock Exchange, Inc.; Notice of Filing and Immediate...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-24

    ... increase efficiency and reduce financial risk by allowing the Exchange to draft against the Clearing Member... reduce financial risk by allowing the Exchange to draft against the Clearing Member's account the amount... via check or bank transfer, which is designed to increase efficiency and reduce financial risk. The...

  6. 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.

  7. 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.

  8. 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.

  9. 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.…

  10. Geology Exchange Program

    NASA Astrophysics Data System (ADS)

    Because geology professors cannot bring ore deposits from around the globe into their classrooms, the next best thing is to take their students to the deposits, according to David Norman, an associate professor of geochemistry at New Mexico Tech and Angus Moore of the Royal School of Mines. They organized a new exchange program between the New Mexico Institute of Mining and Technology in Socorro, N.M., and the Royal School of Mines in London, England. In May, 14 students from England toured deposits in New Mexico, Arizona, Utah, and Colorado; in the photograph, Norman (on the right) describes a rock from a New Mexico ore deposit to some of the visitors from England. In early June a contingency from New Mexico Tech began studying deposits in England, Spain, and Portugal. Norman and Moore say that the exchange program may be expanded next year.

  11. 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)

  12. 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.

  13. 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.

  14. Armed Services Exchange Regulations

    DTIC Science & Technology

    1986-12-15

    itemc and brands as approved Remover; nail polish Rouge; including eye makeup Shampoo Shaving accessories and supplies Skin creams and lotions Soap...morale, welfare, and recrea- tion (MWR) activities, military exchanges have the dual mission of providing authorized patrons with articles and services...Further delegating of this authority is prohibited. Deviations shall be authorized only after judicious review and shall he granted primarily on the

  15. Optimizing exchanger design early

    SciTech Connect

    Lacunza, M.; Vaschetti, G.; Campana, H.

    1987-08-01

    It is not practical for process engineers and designers to make a rigorous economic evaluation for each component of a process due to the loss of time and money. But, it's very helpful and useful to have a method for a quick design evaluation of heat exchangers, considering their important contribution to the total fixed investment in a process plant. This article is devoted to this subject, and the authors present a method that has been proved in some design cases. Linking rigorous design procedures with a quick cost-estimation method provides a good technique for obtaining the right heat exchanger. The cost will be appropriate, sometimes not the lowest because of design restrictions, but a good approach to the optimum in an earlier process design stage. The authors intend to show the influence of the design variables in a shell and tube heat exchanger on capital investment, or conversely, taking into account the general limiting factors of the process such as thermodynamics, operability, corrosion, etc., and/or from the mechanical design of the calculated unit. The last is a special consideration for countries with no access to industrial technology or with difficulties in obtaining certain construction materials or equipment.

  16. Scraped surface heat exchangers.

    PubMed

    Rao, Chetan S; Hartel, Richard W

    2006-01-01

    Scraped surface heat exchangers (SSHEs) are commonly used in the food, chemical, and pharmaceutical industries for heat transfer, crystallization, and other continuous processes. They are ideally suited for products that are viscous, sticky, that contain particulate matter, or that need some degree of crystallization. Since these characteristics describe a vast majority of processed foods, SSHEs are especially suited for pumpable food products. During operation, the product is brought in contact with a heat transfer surface that is rapidly and continuously scraped, thereby exposing the surface to the passage of untreated product. In addition to maintaining high and uniform heat exchange, the scraper blades also provide simultaneous mixing and agitation. Heat exchange for sticky and viscous foods such as heavy salad dressings, margarine, chocolate, peanut butter, fondant, ice cream, and shortenings is possible only by using SSHEs. High heat transfer coefficients are achieved because the boundary layer is continuously replaced by fresh material. Moreover, the product is in contact with the heating surface for only a few seconds and high temperature gradients can be used without the danger of causing undesirable reactions. SSHEs are versatile in the use of heat transfer medium and the various unit operations that can be carried out simultaneously. This article critically reviews the current understanding of the operations and applications of SSHEs.

  17. Exchange-driven growth.

    PubMed

    Ben-Naim, E; Krapivsky, P L

    2003-09-01

    We study a class of growth processes in which clusters evolve via exchange of particles. We show that depending on the rate of exchange there are three possibilities: (I) Growth-clusters grow indefinitely, (II) gelation-all mass is transformed into an infinite gel in a finite time, and (III) instant gelation. In regimes I and II, the cluster size distribution attains a self-similar form. The large size tail of the scaling distribution is Phi(x) approximately exp(-x(2-nu)), where nu is a homogeneity degree of the rate of exchange. At the borderline case nu=2, the distribution exhibits a generic algebraic tail, Phi(x) approximately x(-5). In regime III, the gel nucleates immediately and consumes the entire system. For finite systems, the gelation time vanishes logarithmically, T approximately [lnN](-(nu-2)), in the large system size limit N--> infinity. The theory is applied to coarsening in the infinite range Ising-Kawasaki model and in electrostatically driven granular layers.

  18. 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

  19. Enhanced Mr and (BH)max in anisotropic R2Fe14B/α-Fe composite magnets via intergranular magnetostatic coupling

    NASA Astrophysics Data System (ADS)

    Gabay, A. M.; Marinescu, M.; Hadjipanayis, G. C.

    2006-04-01

    Composite magnets were prepared by hot pressing followed by hot deformation of blends composed of Nd14Fe79.5Ga0.5B6 or (Nd0.75Dy0.25)14Fe79.5Ga0.5B6 ribbon powders as a high-coercivity component and Fe powder as a high-magnetization component. The addition of 15 wt % α-Fe to (Nd0.75Dy0.25)14Fe79.5Ga0.5B6 increases the remanent magnetization of the hot-deformed magnets from 10.6 to 12.04 kG, while the maximum energy product is also increased from 27.3 to 29.5 MG Oe for hot-deformed magnets with 10 wt % α-Fe addition. Microstructure investigations of the composite magnets revealed the size of the Fe particles in the micrometer range, exceeding by far the size for effective exchange interactions. Despite a less refined microstructure, the particular layered configuration of the composite magnets gives rise to a positive magnetostatic coupling of the grains and therefore a unitary magnetic behavior with enhanced magnetic properties. The cooperative demagnetization process, together with the magnetic coupling of the grains, was pointed out through a smooth demagnetization curve and a sharp single peak of the irreversible susceptibility.

  20. 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%.

  1. Exchange living-donor kidney transplantation: merits and limitations.

    PubMed

    Huh, Kyu Ha; Kim, Myoung Soo; Ju, Man Ki; Chang, Hye Kyung; Ahn, Hyung Joon; Lee, Su Hyung; Lee, Jong Hoon; Kim, Soon Il; Kim, Yu Seun; Park, Kiil

    2008-08-15

    The shortage of donor organs is one of the major barriers to transplantation worldwide. After the success of the direct exchange donor (swap) program in Korea since 1991, we have developed a swap-around program. However, reports on the long-term outcomes of exchange donor programs are scarce. From September 1995 to September 2006, we performed 1193 cases of renal transplantation, including 398 cases from living-unrelated donors. The living-unrelated donors included 129 exchange donors and 269 nonexchange donors. We compared the outcomes of the exchange program with that of the nonexchange program, and examined the merits and limitations of the exchange program. The reasons for the exchange program were ABO incompatibility (n=84, 65.1%), human leukocyte antigen mismatching beyond our criteria (n=39, 30.2%), or positive lymphocyte crossmatch (n=6, 4.7%). The overall 10-year graft survival (86.3%) of exchange transplantation was comparable with that of nonexchange (82.3%) or one- haplotype matched living-related (81.2%) transplantation (P=0.2994). In multivariate analysis, exchange versus nonexchange donors did not affect graft survival. The proportion of blood-type O donors was much lower in the exchange group (29.5%) than in the nonexchange group (42.4%; P=0.026). Blood-type O kidneys were preferentially allocated to blood-type O recipients (78.9%) in the exchange group as compared with the nonexchange group (54.4%; P=0.007). We achieved excellent outcomes by using a donor exchange program as an option to reduce the donor organ shortage. However, the exchange donor program has no added benefit for blood-type O recipients.

  2. 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.

  3. 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.

  4. Pressurized-Flat-Interface Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Voss, F. E.; Howell, H. R.; Winkler, R. V.

    1990-01-01

    High thermal conductance obtained without leakage between loops. Heat-exchanger interface enables efficient transfer of heat between two working fluids without allowing fluids to intermingle. Interface thin, flat, and easy to integrate into thermal system. Possible application in chemical or pharmaceutical manufacturing when even trace contamination of process stream with water or other coolant ruins product. Reduces costs when highly corrosive fluids must be cooled or heated.

  5. 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.

  6. Characterization of various losses in a cryogenic counterflow heat exchanger

    NASA Astrophysics Data System (ADS)

    Aminuddin, Mohammad; Zubair, Syed M.

    2014-11-01

    A detailed assessment of irreversibility, predominantly heat in-leak and axial wall conduction, is essential in accurately predicting the performance of high effectiveness heat exchangers employed in cryogenic applications. Integration into a refrigeration system as well requires consideration of parasitic heat loss by conduction from exchanger cold end to the adjacent components. Governing equations incorporating these effects in a counterflow exchanger are solved numerically and the model predictions evaluated for heat exchanger ineffectiveness and heat loss by conduction. The optimum performance mandates minimization of both. Although ineffectiveness decreases at higher longitudinal conduction, cold end loss increases with deterioration of the overall performance. Utilizing lower heat capacity rate hot fluid, nevertheless, reduces the cold end loss. Heat in-leak is relatively high with concurrent consideration of axial wall conduction and has adverse consequence on heat exchanger effectiveness. Analysis of the net heat transferred to lower stages of refrigeration reveals a critical NTU.

  7. Gas Exchange of Algae

    PubMed Central

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

    1967-01-01

    The oxygen production of a photosynthetic gas exchanger containing Chlorella pyrenoidosa (1% packed cell volume) was measured when various concentrations of carbon dioxide were present within the culture unit. The internal carbon dioxide concentrations were obtained by manipulating the entrance gas concentration and the flow rate. Carbon dioxide percentages were monitored by means of electrodes placed directly in the nutrient medium. The concentration of carbon dioxide in the nutrient medium which produced maximal photosynthesis was in the range of 1.5 to 2.5% by volume. Results were unaffected by either the level of carbon dioxide in the entrance gas or the rate of gas flow. Entrance gases containing 2% carbon dioxide flowing at 320 ml/min, 3% carbon dioxide at 135 ml/min, and 4% carbon dioxide at 55 ml/min yielded optimal carbon dioxide concentrations in the particular unit studied. By using carbon dioxide electrodes implanted directly in the gas exchanger to optimize the carbon dioxide concentration throughout the culture medium, it should be possible to design more efficient large-scale units. PMID:4382391

  8. High flux heat exchanger

    NASA Astrophysics Data System (ADS)

    Flynn, Edward M.; Mackowski, Michael J.

    1993-01-01

    This interim report documents the results of the first two phases of a four-phase program to develop a high flux heat exchanger for cooling future high performance aircraft electronics. Phase 1 defines future needs for high flux heat removal in advanced military electronics systems. The results are sorted by broad application categories: (1) commercial digital systems, (2) military data processors, (3) power processors, and (4) radar and optical systems. For applications expected to be fielded in five to ten years, the outlook is for steady state flux levels of 30-50 W/sq cm for digital processors and several hundred W/sq cm for power control applications. In Phase 1, a trade study was conducted on emerging cooling technologies which could remove a steady state chip heat flux of 100 W/sq cm while holding chip junction temperature to 90 C. Constraints imposed on heat exchanger design, in order to reflect operation in a fighter aircraft environment, included a practical lower limit on coolant supply temperature, the preference for a nontoxic, nonflammable, and nonfreezing coolant, the need to minimize weight and volume, and operation in an accelerating environment. The trade study recommended the Compact High Intensity Cooler (CHIC) for design, fabrication, and test in the final two phases of this program.

  9. 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.

  10. Harnessing Private-Sector Innovation to Improve Health Insurance Exchanges.

    PubMed

    Gresenz, Carole Roan; Hoch, Emily; Eibner, Christine; Rudin, Robert S; Mattke, Soeren

    2016-05-09

    Overhauling the individual health insurance market-including through the creation of health insurance exchanges-was a key component of the Patient Protection and Affordable Care Act's multidimensional approach to addressing the long-standing problem of the uninsured in the United States. Despite succeeding in enrolling millions of Americans, the exchanges still face several challenges, including poor consumer experience, high operational and development costs, and incomplete market penetration. In light of these challenges, analysts considered a different model for the exchanges-privately facilitated exchanges-which could address these challenges and deepen the Affordable Care Act's impact. In this model, the government retains control over sovereign exchange functions but allows the private sector to assume responsibility for more-peripheral exchange functions, such as developing and sustaining exchange websites. Although private-sector entities have already undertaken exchange-related functions on a limited basis, privately facilitated exchanges could conceivably relieve the government of its responsibility for front-end website operations and consumer decision-support functions entirely. A shift to privately facilitated exchanges could improve the consumer experience, increase enrollment, and lower costs for state and federal governments. A move to such a model requires, nonetheless, managing its risks, such as reduced consumer protection, increased consumer confusion, and the possible lack of a viable revenue base for privately facilitated exchanges, especially in less populous states. On net, the benefits are large enough and the risks sufficiently manageable to seriously consider such a shift. This paper provides background information and more detail on the analysts' assessment.

  11. Na/Ca exchange and contraction of the heart

    PubMed Central

    Ottolia, Michela; Torres, Natalia; Bridge, John H. B.; Philipson, Kenneth D.; Goldhaber, Joshua I.

    2013-01-01

    Sodium-calcium exchange (NCX) is the major calcium (Ca) efflux mechanism of ventricular cardiomyocytes. Consequently the exchanger plays a critical role in the regulation of cellular Ca content and hence contractility. Reductions in Ca efflux by the exchanger, such as those produced by elevated intracellular sodium (Na) in response to cardiac glycosides, raise sarcoplasmic reticulum (SR) Ca stores. The result is an increased Ca transient and cardiac contractility. Enhanced Ca efflux activity by the exchanger, for example during heart failure, may reduce diadic cleft Ca and excitation-contraction (EC) coupling gain. This aggravates the impaired contractility associated with SR Ca ATPase dysfunction and reduced SR Ca load in failing heart muscle. Recent data from our laboratories indicate that NCX can also impact the efficiency of EC coupling and contractility independent of SR Ca load through diadic cleft priming with Ca during the upstroke of the action potential. PMID:23770352

  12. 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.

  13. 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.

  14. Imaging Local Diffusive Dynamics Using Diffusion Exchange Spectroscopy MRI

    NASA Astrophysics Data System (ADS)

    Benjamini, Dan; Komlosh, Michal E.; Basser, Peter J.

    2017-04-01

    The movement of water between microenvironments presents a central challenge in the physics of soft matter and porous media. Diffusion exchange spectroscopy (DEXSY) is a powerful 2D nuclear magnetic resonance method for measuring such exchange, yet it is rarely used because of its long scan time requirements. Moreover, it has never been combined with magnetic resonance imaging (MRI). Using probability theory, we vastly reduce the required data, making DEXSY MRI feasible for the first time. Experiments are performed on a composite nerve tissue phantom with restricted and free water-exchanging compartments.

  15. Ion exchange properties of Japanese natural zeolites in seawater.

    PubMed

    Wajima, Takaaki

    2013-01-01

    Ion exchange properties of five different Japanese natural zeolites in seawater were examined. Sodium ions could be reduced by all zeolites, although anions, Cl(-) and SO(4)(2-), in seawater showed barely changes. Natural zeolite desalination treatment mainly depends on the ion exchange between Na(+), K(+) and Mg(2+) in seawater and Ca(2+) in natural zeolite. This study found that mordenite is superior to clinoptilolite for use in Na(+) reduction. Mordenite with high cation exchange capacity containing Ca(2+) resulted in the highest Na(+) reduction from seawater.

  16. Miniature Joule - Thomson liquefier with sintered heat exchanger

    NASA Astrophysics Data System (ADS)

    Eugeniusz, Bodio; Maciej, Chorowski; Marta, Wilczek; Arkadiusz, Bozek

    Conventional Joule-Thomson refrigerators are made with finned, capillary tubing for the heat exchanger and a throttling valve for reducing the pressure [1]. A new kind of recuperative miniature heat-exchanger can be developed if a powder metallurgy technology is used. A high pressure capillary tube is sintered with metal powder. The grains of metal should be ball shaped or similar. In result of sintering process a good thermal contact between an outside tube surface and powder grains is achieved. The heat exchange surface is well developed and a porous sinter acts as a low pressure gas canal.

  17. 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.

  18. 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.

  19. 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.

  20. Characteristics of model heat exchanger

    NASA Astrophysics Data System (ADS)

    Kolínský, Jan

    2017-09-01

    The aim of this paper is thermal analysis of model water to water heat exchanger at different mass flow rates. Experimental study deals with determination of total heat transfer - power of the heat exchanger. Furthermore the paper deals with analysis of heat exchanger charakcteristic using a definition of thermal efficiency. It is demonstrated that it is advisable to monitor the dependence of thermal efficiency and flow ratio.

  1. Developing bulk exchange spring magnets

    DOEpatents

    Mccall, Scott K.; Kuntz, Joshua D.

    2017-06-27

    A method of making a bulk exchange spring magnet by providing a magnetically soft material, providing a hard magnetic material, and producing a composite of said magnetically soft material and said hard magnetic material to make the bulk exchange spring magnet. The step of producing a composite of magnetically soft material and hard magnetic material is accomplished by electrophoretic deposition of the magnetically soft material and the hard magnetic material to make the bulk exchange spring magnet.

  2. 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.

  3. 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.

  4. 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.

  5. LIGHTWEIGHT METAL FOIL HEAT EXCHANGERS,

    DTIC Science & Technology

    HEAT EXCHANGERS, FOILS(MATERIALS), AEROSPACE CRAFT, HYDROGEN, TEST METHODS, STRUCTURES, HEAT TRANSFER, NIOBIUM, FLUID FLOW, FRICTION, ALUMINUM ALLOYS, NICKEL ALLOYS, ALUMINUM , TITANIUM ALLOYS, RAMJET ENGINES.

  6. Exchange-donor renal transplantation.

    PubMed

    Huh, Kyu Ha; Kim, Hyun Jung; Jeon, Kyung Ock; Kiml, Beom Seok; Kim, Yu Seun; Park, Kill

    2009-01-01

    Exchange-donor programs may prevent the current loss of many suitable living donors. Both incompatible donor-recipient pairs--with ABO incompatibility or positive cross-matches--and compatible pairs who wish to locate more suitable donors should be encouraged to participate in exchange-donor programs. Advantages and limitations of exchange-donor programs must be carefully explained to prevent interfamilial conflict. Exchange-donor programs may relieve shortages of donor organs and offer good posttransplant outcomes. Therefore, this program should be widely implemented.

  7. 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.

  8. Fibrinogen Reduction During Selective Plasma Exchange due to Membrane Fouling.

    PubMed

    Ohkubo, Atsushi; Okado, Tomokazu; Miyamoto, Satoko; Hashimoto, Yurie; Komori, Shigeto; Yamamoto, Motoki; Maeda, Takuma; Itagaki, Ayako; Yamamoto, Hiroko; Seshima, Hiroshi; Kurashima, Naoki; Iimori, Soichiro; Naito, Shotaro; Sohara, Eisei; Uchida, Shinichi; Rai, Tatemitsu

    2017-06-01

    Fibrinogen is substantially reduced by most plasmapheresis modalities but retained in selective plasma exchange using Evacure EC-4A10 (EC-4A). Although EC-4A's fibrinogen sieving coefficient is 0, a session of selective plasma exchange reduced fibrinogen by approximately 19%. Here, we investigated sieving coefficient in five patients. When the mean processed plasma volume was 1.15 × plasma volume, the mean reduction of fibrinogen during selective plasma exchange was approximately 15%. Fibrinogen sieving coefficient was 0 when the processed plasma volume was 1.0 L, increasing to 0.07 when the processed plasma volume was 3.0 L, with a mean of 0.03 during selective plasma exchange. When fibrinogen sieving coefficient was 0, selective plasma exchange reduced fibrinogen by approximately 10%. Scanning electron microscopy images revealed internal fouling of EC-4A's hollow fiber membrane by substances such as fibrinogen fibrils. Thus, fibrinogen reduction by selective plasma exchange may be predominantly caused by membrane fouling rather than filtration. © 2017 International Society for Apheresis, Japanese Society for Apheresis, and Japanese Society for Dialysis Therapy.

  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. 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).

  11. 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.

  12. 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

  13. 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.

  14. International Cell Exchange, 1994.

    PubMed

    Lau, M; Terasaki, P I; Park, M S

    1994-01-01

    1. We summarize typings of 40 cells for Class I antigens and 20 cultured cell lines for Class II antigens through the International Cell Exchange in 1994. Serologic Class II typings were compared with DNA typings for the same 20 cells. Two hundred eighty-one laboratories participated in the monthly Class I Serum Exchange. One hundred nineteen serology laboratories and 74 DNA laboratories reported Class II specificities on a monthly basis. 2. The average detection levels, as well as the high detection levels, were determined for 16 A-locus and 27 B-locus antigens. Mean detection rates of 95% or greater average detection were obtained for 12 A-locus and 10 B-locus antigens. Lower than 80% agreement was calculated for one A-locus antigen (A74) and 7 B-locus (B46, B48, B61, B67, B73, B75, B77) antigens. 3. We compared discrepancy rates of 10 A-locus and 7 B-locus antigens typed 3 times or more. The false-negative discrepancy rates, i.e. how often the antigen was missed, were greater for more of the B-locus specificities than for the A-locus antigens. B62, having the highest false-positive rate, tended to be overassigned. The discrepancy rates, especially the false-negative rate, for B70 were shown to decrease over a 7-year period. 4. In 1994, 8 laboratories attained records of total no misses for all analyzed antigens. Twelve laboratories had final records of only one discrepancy, and 5 laboratories had impressive perfect records (zero false negatives and false positives) for their yearly antigen reports. 5. Retyping of 12 Class I and 8 Class II reference cells showed improved detection of antigens. Results of a donor typed 4 times over 11 years demonstrated marked improvement, nearly doubling for A33, B38, and B75. Two cells first typed in 1991, then retyped in 1994, showed improved detection for Class II splits by serology and DNA typing. 6. We updated the list of sequenced Class I Exchange cells. Seven new cells were added as well as confirmatory sequence data for A

  15. 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.

  16. 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.…

  17. O(+) charge exchange in the polar wind

    NASA Astrophysics Data System (ADS)

    Barakat, A. R.; Schunk, R. W.

    1984-11-01

    O(+) density and flux profiles are calculated for a steady state polar wind flow of O(+) ions and electrons along geomagnetic field lines in the polar cap. Profiles are computed both with and without allowance for accidentally resonant charge exchange (ARCE) between O(+) and H. It is found that ARCE acts to reduce the limiting O(+) escape flux by less than 30 percent for typical atmospheric conditions and by only a factor of about 3.5 for atmospheres with low exospheric temperatures. Allowing for ARCE, the limiting O(+) escape flux is of the order of 5 x 10 to the 8th to 9th/cu cm/s, depending on the atmospheric conditions. This indicates that, contrary to previous predictions, there is no O(+) charge exchange barrier and it is therefore not necessary to have an acceleration mechanism at low altitudes in order to have an appreciable O(+) escape flux.

  18. Pulmonary gas exchange in diving.

    PubMed

    Moon, R E; Cherry, A D; Stolp, B W; Camporesi, E M

    2009-02-01

    Diving-related pulmonary effects are due mostly to increased gas density, immersion-related increase in pulmonary blood volume, and (usually) a higher inspired Po(2). Higher gas density produces an increase in airways resistance and work of breathing, and a reduced maximum breathing capacity. An additional mechanical load is due to immersion, which can impose a static transrespiratory pressure load as well as a decrease in pulmonary compliance. The combination of resistive and elastic loads is largely responsible for the reduction in ventilation during underwater exercise. Additionally, there is a density-related increase in dead space/tidal volume ratio (Vd/Vt), possibly due to impairment of intrapulmonary gas phase diffusion and distribution of ventilation. The net result of relative hypoventilation and increased Vd/Vt is hypercapnia. The effect of high inspired Po(2) and inert gas narcosis on respiratory drive appear to be minimal. Exchange of oxygen by the lung is not impaired, at least up to a gas density of 25 g/l. There are few effects of pressure per se, other than a reduction in the P50 of hemoglobin, probably due to either a conformational change or an effect of inert gas binding.

  19. Separation of intra- and intergranular magnetotransport properties in nanocrystalline diamond films on the metallic side of the metal-insulator transition

    NASA Astrophysics Data System (ADS)

    Janssens, S. D.; Pobedinskas, P.; Vacik, J.; Petráková, V.; Ruttens, B.; D'Haen, J.; Nesládek, M.; Haenen, K.; Wagner, P.

    2011-08-01

    A systematic study on the morphology and electronic properties of thin heavily boron-doped nanocrystalline diamond (NCD) films is presented. The films have nominally the same thickness (≈150 nm) and are grown with a fixed B/C ratio (5000 ppm) but with different C/H ratios (0.5-5%) in the gas phase. The morphology of the films is investigated by x-ray diffraction and atomic force microscopy measurements, which confirm that lower C/H ratios lead to a larger average grain size. Magnetotransport measurements reveal a decrease in resistivity and a large increase in mobility, approaching the values obtained for single-crystal diamond as the average grain size of the films increases. In all films, the temperature dependence of resistivity decreases with larger grains and the charge carrier density and mobility are thermally activated. It is possible to separate the intra- and intergrain contributions for resistivity and mobility, which indicates that in these complex systems Matthiessen's rule is followed. The concentration of active charge carriers is reduced when the boron-doped NCD is grown with a lower C/H ratio. This is due to lower boron incorporation, which is confirmed by neutron depth profiling.

  20. Improvement of magnetic intergranular isolation and evaluation of read/write characteristics on SmCo 5 perpendicular magnetic thin films

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    SmCo 5 alloy is a promising candidate for ultra-high-density perpendicular magnetic recording (PMR) media because of its high uniaxial magnetocrystalline anisotropy Ku of more than 1.1×10 8 erg/cm 3. Previously, we successfully achieved high Ku in a sputter-deposited SmCo 5 thin film by introducing a Cu/Ti dual underlayer. However, in order to apply the SmCo 5 films to practical PMR media, it is necessary to decrease medium noise. A granulated magnetic film comprising of small and magnetically decoupled grains is effective in reducing the medium noise. In this paper, we have proposed a new granular film that is fabricated by partial thermodiffusion of Cu between the Sm-Co continuous layer and the Cu underlayer, which is granulated using compositional segregation caused by the addition of Ta 2O 5. We have analyzed the magnetic properties, magnetic domain size, and magnetization reversal process of the proposed SmCo 5 film. The magnetic domain size decreased and the magnetization reversal process changed from the magnetic-wall-motion mode to a coherent rotation mode to some extent on isolation of magnetic grains. The read/write characteristics of granulated SmCo 5 double-layered media were also evaluated. The medium noise decreased and the signal-to-noise ratio increased for the granulated double-layered (PMR) medium.

  1. 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)

  2. 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.

  3. The Transatlantic Orientation Exchange Project

    ERIC Educational Resources Information Center

    Gisevius, Annette; Weber, Robin A.

    2009-01-01

    The Transatlantic Orientation Exchange/Multiplikatorenschulung im transatlan-tischen Austausch is a collaboration between volunteers and staff in both the US and German AFS organizations. The goal of the project is to increase the level of intercultural learning of German and US secondary education exchange participants and their host families.…

  4. Macroreticular chelating ion-exchangers.

    PubMed

    Hirsch, R F; E Gancher, R; Russo, F R

    1970-06-01

    Two macroreticular chelating ion-exchangers have been prepared and characterized. One contains the iminodiacetate group and the second contains the arsonate group as the ion-exchanging site. The macroreticular resins show selectivities among metal ions similar to those of the commercially available naicroreticular chelating resins. Chromatographie separations on the new resins are rapid and sharp.

  5. The Transatlantic Orientation Exchange Project

    ERIC Educational Resources Information Center

    Gisevius, Annette; Weber, Robin A.

    2009-01-01

    The Transatlantic Orientation Exchange/Multiplikatorenschulung im transatlan-tischen Austausch is a collaboration between volunteers and staff in both the US and German AFS organizations. The goal of the project is to increase the level of intercultural learning of German and US secondary education exchange participants and their host families.…

  6. 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.

  7. The NESACS Exchange with Germany

    ERIC Educational Resources Information Center

    Hoffman, Morton Z.; Tanner, Ruth; Strem, Michael

    2007-01-01

    The Northeastern Section of the American Chemical Society (NESACS) is going to host visit to the representatives of the German Chemical Society (GDCh) at their annual exchange program this year. The delegation is expected to spotlight the ACS international effects, in addition to the advantages of the exchange between the two organizations.

  8. 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…

  9. 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

  10. 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.

  11. 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

  12. 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.

  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. Aluminum heat exchanger

    SciTech Connect

    Koisuka, M.; Aoki, H.

    1986-11-04

    This patent describes a heat exchanger comprising a flat metal tube for conducting fluid having opposite first and second ends, of metal fins fixed onto outer surfaces of the flat metal tube, first and second header pipes fixedly mounted on the opposite ends of the flat metal tube, respectively, so that the flat metal tube communicates with the interior of the header pipes. Each of the header pipes has a first end that is open and a second end that is closed. An inlet tube is connected to the first end of the first header pipe, and an outlet tube is connected to the first end of the second header pipe. The improvement described here comprises one of the inlet and outlet tubes having an end portion inserted into the first end of the corresponding interconnected header pipe. The end portion has a cut-away portion in the form of a first axial slit extending axially inwardly from an open end at the adjacent end of the one tube. The first axial slit has an axial intermediate portion slightly smaller than the thickness of the flat metal tube, and a tapered portion diverging towards the open end of the first axial slit, and the first end of the flat metal tube extends into the corresponding interconnected header pipe and is closely fitted into the first axial slit.

  15. Starrett City energy exchange

    SciTech Connect

    Not Available

    1982-01-01

    The Starrett City/26th Ward Energy Project is a joint effort of Starrett City (a privately owned and operated 5881-unit high rise housing complex located in Brooklyn, NY) and the city of New York Department of Environmental Protection to develop the means to utilize waste-derived energy produced as by-products of municipal waste water treatment. Starrett City, a development of over 20,000 residents with its own schools, shopping and community centers, and power plant, is located directly across the street from the City of New York's 26th Ward Water Pollution Control Plant. Out of five energy exchange options, a cooperative project team recommended three: (1) transmitting all digester gas from the 26th Ward wastewater sewage-treatment facility to Starrett's cogeneration-type total energy plant (TEP), (2) piping hot water from the Starrett TEP to provide space and process heat to the 26th Ward, and (3) pumping treated effluent from the 26th Ward to the TEP to eliminate the need for Starrett's cooling tower. Starrett City assumed all installation and maintenance costs, both on city property and the TEP. Starrett projects a 53$ million saving in fuel costs over the next 20 years. The project will serve as a model for similar energy resource development efforts and offer the rationale for the private sector and municipalities to build together for the future.

  16. 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.

  17. 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.

  18. Effects of apolipoproteins on the kinetics of cholesterol exchange

    SciTech Connect

    Letizia, J.Y.; Phillips, M.C. )

    1991-01-22

    The effects of apolipoproteins on the kinetics of cholesterol exchange have been investigated by monitoring the transfer of ({sup 14}C)cholesterol from donor phospholipid/cholesterol complexes containing human apolipoproteins A, B, or C. Negatively charged discoidal and vesicular particles containing purified apolipoproteins complexed with lipid and a trace of ({sup 14}C)cholesterol were incubated with a 10-fold excess of neutral, acceptor, small unilamellar vesicles. The donor and acceptor particles were separated by chromatogrphy of DEAE-Sepharose, and the rate of movement of labeled cholesterol was analyzed as a first-order exchange process. The kinetics of exchange of cholesterol from both vesicular and discoidal complexes that contain apoproteins are consistent with an aqueous diffusion mechanism, as has been established previously for PC/cholesterol SUV. Apolipoproteins A-I, A-II, reduced and carboxymethylated A-11, and B-100 present in SUV at the same lipid/protein (w/w) ratio all enhance the rate of cholesterol exchange to about the same degree. Cholesterol molecules exchange more rapidly from discoidal complexes. Generally, as the diameter of apoprotein/phospholipid/cholesterol discs decreases, t{sub 1/2} for cholesterol exchange decreases. Since small bilayer discs have a relatively high ratio of boundary to face surface area, cholesterol molecules desorb more rapidly than from larger discs. The modulation of lipid packing by the apoprotein molecules present at the surface of lipoprotein particles affects the rate of cholesterol exchange from such particles.

  19. Exact exchange with non-orthogonal generalized Wannier functions.

    PubMed

    Mountjoy, Jeff; Todd, Michelle; Mosey, Nicholas J

    2017-03-14

    The evaluation of exact exchange (EXX) is an important component of quantum chemical calculations performed with ab initio and hybrid density functional methods. While evaluating exact exchange is routine in molecular quantum chemical calculations performed with localized basis sets, the non-local nature of the exchange operator presents a major impediment to the efficient use of exact exchange in calculations that employ planewave basis sets. Non-orthogonal generalized Wannier functions (NGWFs) corresponding to planewave expansions of localized basis functions are an alternative form of basis set that can be used in quantum chemical calculations. The periodic nature of these functions renders them suitable for calculations of periodic systems, while the contraction of sets of planewaves into individual basis functions reduces the number of variational parameters, permitting the construction and direct diagonalization of the Fock matrix. The present study examines how NGWFs corresponding to Fourier series representations of conventional atom-centered basis sets can be used to evaluate exact exchange in periodic systems. Specifically, an approach for constructing the exchange operator with NGWFs is presented and used to perform Hartree-Fock calculations with a series of molecules in periodically repeated simulation cells. The results demonstrate that the NGWF approach is significantly faster than the EXX method, which is a standard approach for evaluating exact exchange in periodic systems.

  20. Exact exchange with non-orthogonal generalized Wannier functions

    NASA Astrophysics Data System (ADS)

    Mountjoy, Jeff; Todd, Michelle; Mosey, Nicholas J.

    2017-03-01

    The evaluation of exact exchange (EXX) is an important component of quantum chemical calculations performed with ab initio and hybrid density functional methods. While evaluating exact exchange is routine in molecular quantum chemical calculations performed with localized basis sets, the non-local nature of the exchange operator presents a major impediment to the efficient use of exact exchange in calculations that employ planewave basis sets. Non-orthogonal generalized Wannier functions (NGWFs) corresponding to planewave expansions of localized basis functions are an alternative form of basis set that can be used in quantum chemical calculations. The periodic nature of these functions renders them suitable for calculations of periodic systems, while the contraction of sets of planewaves into individual basis functions reduces the number of variational parameters, permitting the construction and direct diagonalization of the Fock matrix. The present study examines how NGWFs corresponding to Fourier series representations of conventional atom-centered basis sets can be used to evaluate exact exchange in periodic systems. Specifically, an approach for constructing the exchange operator with NGWFs is presented and used to perform Hartree-Fock calculations with a series of molecules in periodically repeated simulation cells. The results demonstrate that the NGWF approach is significantly faster than the EXX method, which is a standard approach for evaluating exact exchange in periodic systems.

  1. T2-Filtered T2 - T2 Exchange NMR

    NASA Astrophysics Data System (ADS)

    d'Eurydice, Marcel Nogueira; Montrazi, Elton Tadeu; Fortulan, Carlos Alberto; Bonagamba, Tito José

    2016-05-01

    This work introduces an alternative way to perform the T2 - T2 Exchange NMR experiment. Rather than varying the number of π pulses in the first CPMG cycle of the T2 - T2 Exchange NMR pulse sequence, as used to obtain the 2D correlation maps, it is fixed and small enough to act as a short T2-filter. By varying the storage time, a set of 1D measurements of T2 distributions can be obtained to reveal the effects of the migration dynamics combined with relaxation effects. This significantly reduces the required time to perform the experiment, allowing a more in-depth study of exchange dynamics and relaxation processes with improved signal-to-noise ratio. These aspects stand as basis of this novel experiment, T2-Filtered T2 - T2 Exchange NMR or simply T2 F-TREx.

  2. Van der Waals density functional: An appropriate exchange functional

    NASA Astrophysics Data System (ADS)

    Cooper, Valentino R.

    2010-04-01

    In this Rapid Communication, an exchange functional which is compatible with the nonlocal Rutgers-Chalmers correlation functional [van der Waals density functional (vdW-DF)] is presented. This functional, when employed with vdW-DF, demonstrates remarkable improvements on intermolecular separation distances while further improving the accuracy of vdW-DF interaction energies. The key to the success of this three-parameter functional is its reduction in short-range exchange repulsion through matching to the gradient expansion approximation in the slowly varying/high-density limit while recovering the large reduced gradient, s , limit set in the revised Perdew-Burke-Ernzerhof (revPBE) exchange functional. This augmented exchange functional could be a solution to long-standing issues of vdW-DF lending to further applicability of density-functional theory to the study of relatively large, dispersion bound (van der Waals) complexes.

  3. 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.

  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.

  5. 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.

  6. Methods for measuring exchangeable protons in glycosaminoglycans.

    PubMed

    Beecher, Consuelo N; Larive, Cynthia K

    2015-01-01

    Recent NMR studies of the exchangeable protons of GAGs in aqueous solution, including those of the amide, sulfamate, and hydroxyl moieties, have demonstrated potential for the detection of intramolecular hydrogen bonds, providing insights into secondary structure preferences. GAG amide protons are observable by NMR over wide pH and temperature ranges; however, specific solution conditions are required to reduce the exchange rate of the sulfamate and hydroxyl protons and allow their detection by NMR. Building on the vast body of knowledge on detection of hydrogen bonds in peptides and proteins, a variety of methods can be used to identify hydrogen bonds in GAGs including temperature coefficient measurements, evaluation of chemical shift differences between oligo- and monosaccharides, and relative exchange rates measured through line shape analysis and EXSY spectra. Emerging strategies to allow direct detection of hydrogen bonds through heteronuclear couplings offer promise for the future. Molecular dynamic simulations are important in this effort both to predict and confirm hydrogen bond donors and acceptors.

  7. Titanium for condenser and heat exchanger service

    SciTech Connect

    Mountford, J.A. Jr.

    1996-12-31

    The use of titanium for heat exchanger service has increased dramatically over the past 20 years and continues to expand into many additional market applications. Its greatest use (as both tubing and tubesheets) is in utility steam condensers where tens of millions of feet are produced annually to service plants throughout the world with the harshest of cooling waters. Many additional utility in-plant heat exchangers use titanium as well, as do industries to include the Navy and marine, offshore oil, petrochemical processing, PTA, LNG, desalination, salt production, refinery, refrigeration and air conditioning, among others. With its virtual immunity to all natural and harsh waters (including seawater, brackish, fresh, chloride laden, etc.) and to MIC, titanium eliminates the corrosion problems and concerns related to cooling waters, the effects of tube cleaning operations necessary to eliminate normal debris and fouling, and stagnant or no flow conditions. This paper will review where and why titanium is used as exemplified in its corrosion immunity ranges and heat transfer comparisons, while providing updates on the development of newer available grades and more recent applications. Where thought to be used only in specific plant areas, titanium can and should be considered for providing uncompromised service to reduce maintenance and eliminate persistent corrosion problems in the many other areas where heat exchangers are required.

  8. Post-quantum key exchange protocols

    NASA Astrophysics Data System (ADS)

    Li, Xiangdong; Leung, Lin; Kwan, Andis Chi-Tung; Zhang, Xiaowen; Kahanda, Dammika; Anshel, Michael

    2006-05-01

    If an eavesdropper Eve is equipped with quantum computers, she can easily break the public key exchange protocols used today. In this paper we will discuss the post-quantum Diffie-Hellman key exchange and private key exchange protocols.

  9. 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.

  10. 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.

  11. Heat exchanger using graphite foam

    DOEpatents

    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. 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.

  13. 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.

  14. 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

    ... From the Federal Register Online via the Government Publishing Office SECURITIES AND EXCHANGE COMMISSION Application of Topaz Exchange, LLC for Registration as a National Securities Exchange; Findings, Opinion, and Order of the Commission July 26, 2013. I. Introduction On July 3, 2012, Topaz Exchange, LLC (``Topaz Exchange'' or ``Exchange'')...

  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

    ...; 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.; New York Stock Exchange LLC; NYSE Amex LLC; NYSE Arca, Inc.; Notice of Designation of Longer Period...

  16. 75 FR 53366 - Self-Regulatory Organizations; BATS Exchange, Inc.; Chicago Board Options Exchange, Incorporated...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-31

    ...; 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.; New York Stock Exchange LLC; NYSE Amex LLC; NYSE Arca, Inc.; Notice of Designation of Longer Period...

  17. 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

  18. 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.

  19. Intraocular lens exchange for high myopia in pseudophakic children.

    PubMed

    Kraus, C L; Trivedi, R H; Wilson, M E

    2016-09-01

    PurposeThe purpose of this study was to examine the preoperative factors and postoperative outcomes following intraocular lens (IOL) exchange for high myopia in pseudophakic children.MethodsThe medical records of all patients undergoing IOL exchange for high myopia were retrospectively reviewed.ResultsA total of 15 eyes were identified that had undergone an IOL exchange for myopic shift. Average age of cataract extraction (CE) was 5.4 months. In all, 10/15 had a unilateral cataract. IOL exchange usually occurred at an average of 6 years following cataract surgery. The average spherical equivalent (SE) of the refractive error at that time was -9.6 D. Following IOL exchange, SE was -1.3 D. A two-line reduction in best-corrected visual acuity was observed in 1/13 of our patients for whom pre- and post-exchange data were available. The average axial length (AL) of the eye undergoing the IOL exchange was 24.0 mm, average AL in the non-operative eye was 22.1 mm. On average, the operative eyes grew 4.4 mm and the non-operative eyes 3.02 mm. No adverse events were seen in the operative eyes.ConclusionYounger age at the time of CE creates a greater likelihood of AL elongation and predisposes a child to myopic shift. IOL exchange should be considered an option to reduce anisometropia and associated aniseikonia to improve visual outcomes. Successful visual rehabilitation and predictable post-exchange refractions were seen with our patients.

  20. Sodium-calcium exchanger in cultured human retinal pigment epithelium.

    PubMed

    Mangini, N J; Haugh-Scheidt, L; Valle, J E; Cragoe, E J; Ripps, H; Kennedy, B G

    1997-12-01

    Regulation of intracellular free Ca2+ concentration ([Ca2+]i) by an Na+/Ca2+ exchanger was studied in cultures of human retinal pigment epithelial cells using Ca(2+)-indicator dyes (fura-2 and fluo-3) and digital fluorescence imaging. Mean resting [Ca2+]i of cultured RPE in a control Ringer solution was 189 +/- 16 nM. Replacing extracellular Na+ with N-methyl-D-glucamine elicited a two-fold rise in [Ca2+]i; the magnitude of the [Na+]o-free-induced rise in [Ca2+]i varied as a function of extracellular [Ca2+]. The [Na+]o-free response was not significantly affected by the Ca2+ channel blocker nifedipine, or by pretreatment with thapsigargin which depletes intracellular Ca2+ stores. By contrast, the [Na+]o-free-induced rise in [Ca2+]i was significantly reduced by CBDMB, an amiloride derivative that is highly selective for Na+/Ca2+ exchange inhibition. These findings indicate that removal of extracellular Na+ promotes net [Ca2+]i gain via Na+/Ca2+ exchange. Western and Northern blot analyses, respectively, confirmed the presence of Na+/Ca2+ exchanger protein and mRNA in cultures of human RPE. Specifically, Western blot analysis of whole cell lysates of cultured RPE using a polyclonal antibody made against the canine cardiac exchanger identified a major band at approximately 126 kD. Northern blot analysis of total human RPE RNA using a restriction fragment cRNA probe coding for the canine cardiac Na+/Ca2+ exchanger showed that the major exchanger-related transcript was approximately 6.8 kb. In sum, our findings demonstrate the presence of a cardiac-exchanger-related transcript was approximately 6.8 kb. In sum, our findings demonstrate the presence of a cardiac-type Na+/Ca2+ exchanger in cultures of human RPE.

  1. 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.

  2. 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.

  3. 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.

  4. Phase Change Material Heat Exchangers

    NASA Image and Video Library

    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 ...

  5. Definition of Magnetic Exchange Length

    SciTech Connect

    Abo, GS; Hong, YK; Park, J; Lee, J; Lee, W; Choi, BC

    2013-08-01

    The magnetostatic exchange length is an important parameter in magnetics as it measures the relative strength of exchange and self-magnetostatic energies. Its use can be found in areas of magnetics including micromagnetics, soft and hard magnetic materials, and information storage. The exchange length is of primary importance because it governs the width of the transition between magnetic domains. Unfortunately, there is some confusion in the literature between the magnetostatic exchange length and a similar distance concerning magnetization reversal mechanisms in particles known as the characteristic length. This confusion is aggravated by the common usage of two different systems of units, SI and cgs. This paper attempts to clarify the situation and recommends equations in both systems of units.

  6. 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.

  7. Toward Uniformity in Exchange Communication

    ERIC Educational Resources Information Center

    Shinn, Isabella

    1972-01-01

    Instant communication, characterized by brevity, should be the practice of exchange librarians trading titles on the international level. Guidelines for a multilingual, many-purpose form letter, which could achieve uniformity, are presented. (14 references) (Author/SJ)

  8. Mass exchange processes with input

    NASA Astrophysics Data System (ADS)

    Krapivsky, P. L.

    2015-05-01

    We investigate a system of interacting clusters evolving through mass exchange and supplemented by input of small clusters. Three possibilities depending on the rate of exchange generically occur when input is homogeneous: continuous growth, gelation, and instantaneous gelation. We mostly study the growth regime using scaling methods. An exchange process with reaction rates equal to the product of reactant masses admits an exact solution which allows us to justify the validity of scaling approaches in this special case. We also investigate exchange processes with a localized input. We show that if the diffusion coefficients are mass-independent, the cluster mass distribution becomes stationary and develops an algebraic tail far away from the source.

  9. Polar Aprotic Modifiers for Chromatographic Separation and Back-Exchange Reduction for Protein Hydrogen/Deuterium Exchange Monitored by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

    PubMed Central

    Valeja, Santosh G.; Emmett, Mark R.; Marshall, Alan G.

    2013-01-01

    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. PMID:22298288

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. Theoretical study of the elasticity, mechanical behavior, electronic structure, interatomic bonding, and dielectric function of an intergranular glassy film model in prismatic {beta}-Si{sub 3}N{sub 4}

    SciTech Connect

    Ching, W. Y.; Rulis, Paul; Aryal, Sitaram; Ouyang, Lizhi; Misra, Anil

    2010-06-01

    Microstructures such as intergranular glassy films (IGFs) are ubiquitous in many structural ceramics. They control many of the important physical properties of polycrystalline ceramics and can be influenced during processing to modify the performance of devices that contain them. In recent years, there has been intense research, both experimentally and computationally, on the structure and properties of IGFs. Unlike grain boundaries or dislocations with well-defined crystalline planes, the atomic scale structure of IGFs, their fundamental electronic interactions, and their bonding characteristics are far more complicated and not well known. In this paper, we present the results of theoretical simulations using ab initio methods on an IGF model in {beta}-Si{sub 3}N{sub 4} with prismatic crystalline planes. The 907-atom model has a dimension of 14.533 A x 15.225 A x 47.420 A . The IGF layer is perpendicular to the z axis, 16.4 A wide, and contains 72 Si, 32 N, and 124 O atoms. Based on this model, the mechanical and elastic properties, the electronic structure, the interatomic bonding, the localization of defective states, the distribution of electrostatic potential, and the optical dielectric function are evaluated and compared with crystalline {beta}-Si{sub 3}N{sub 4}. We have also performed a theoretical tensile experiment on this model by incrementally extending the structure in the direction perpendicular to the IGF plane until the model fully separated. It is shown that fracture occurs at a strain of 9.42% with a maximum stress of 13.9 GPa. The fractured segments show plastic behavior and the formation of surfacial films on the {beta}-Si{sub 3}N{sub 4}. These results are very different from those of a previously studied basal plane model [J. Chen et al., Phys. Rev. Lett. 95, 256103 (2005)] and add insights to the structure and behavior of IGFs in polycrystalline ceramics. The implications of these results and the need for further investigations are discussed.

  16. Exchange factor method: An alternative basis for zonal analysis of radiating enclosures

    SciTech Connect

    Larson, M.E.; Howell, J.R.

    1985-11-01

    In zonal analysis of an enclosure containing a radiatively participating medium, the volume and bounding surface are divided into volume and area elements which are assumed to be isothermal. For a system of M elements consisting of N surfaces and GAMMA volume elements (M = N+GAMMA), M/sup 2/ relationships (direct- or total-exchange areas of conventional zonal analysis) define all possible radiant interchange between element pairs. Due to reciprocity there are at most M(M+1)/2 unique direct-exchange areas. The use of symmetry may greatly reduce the number of unique exchange areas. In the alternative form presented, exchange factors are defined such that a gray medium's gas-to-gas exchange factors describe only the redistribution of radiative source terms. Only surface-to-surface and surface-to-gas (gas-to-surface) relationships are required to wholly define the system in radiative equilibrium. That is, a system in radiative equilibrium may be characterized by as many as GAMMA(GAMMA+1)/2 fewer factors. These same exchange factors may be augmented by gas-to-gas exchange factors to analyze media not in radiative equilibrium. In an isotropically scattering, gray medium, exchange factors are functions of system geometry and total extinction only. The degree of extinction due to scattering does not affect exchange factor. Transformations between direct-exchange areas and exchange factors are developed.

  17. 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.

  18. 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.

  19. 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…

  20. 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.