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Sample records for mode iii effects

  1. Effects of friction and high torque on fatigue crack propagation in Mode III

    NASA Astrophysics Data System (ADS)

    Nayeb-Hashemi, H.; McClintock, F. A.; Ritchie, R. O.

    1982-12-01

    Turbo-generator and automotive shafts are often subjected to complex histories of high torques. To provide a basis for fatigue life estimation in such components, a study of fatigue crack propagation in Mode III (anti-plane shear) for a mill-annealed AISI 4140 steel (RB88, 590 MN/m2 tensile strength) has been undertaken, using torsionally-loaded, circumferentially-notched cylindrical specimens. As demonstrated previously for higher strength AISI 4340 steel, Mode III cyclic crack growth rates (dc/dN) IIIcan be related to the alternating stress intensity factor ΔKIII for conditions of small-scale yielding. However, to describe crack propagation behavior over an extended range of crack growth rates (˜10-6 to 10-2 mm per cycle), where crack growth proceeds under elastic-plastic and full plastic conditions, no correlation between (dc/dN) III and ΔKIII is possible. Accordingly, a new parameter for torsional crack growth, termed the plastic strain intensity Γ III, is introduced and is shown to provide a unique description of Mode III crack growth behavior for a wide range of testing conditions, provided a mean load reduces friction, abrasion, and interlocking between mating fracture surfaces. The latter effect is found to be dependent upon the mode of applied loading (i.e., the presence of superimposed axial loads) and the crack length and torque level. Mechanistically, high-torque surfaces were transverse, macroscopically flat, and smeared. Lower torques showed additional axial cracks (longitudinal shear cracking) perpendicular to the main transverse surface. A micro-mechanical model for the main radi l Mode III growth, based on the premise that crack advance results from Mode II coalescence of microcracks initiated at inclusions ahead of the main crack front, is extended to high nominal stress levels, and predicts that Mode III fatigue crack propagation rates should be proportional to the range of plastic strain intensity (ΔΓIII if local Mode II growth rates are

  2. Complexation of uranium(VI) and samarium(III) with oxydiacetic acid: temperature effect and coordination modes.

    PubMed

    Rao, Linfeng; Garnov, Alexander Yu; Jiang, Jun; Di Bernardo, Plinio; Zanonato, PierLuigi; Bismondo, Arturo

    2003-06-01

    The complexation of uranium(VI) and samarium(III) with oxydiacetate (ODA) in 1.05 mol kg(-1) NaClO(4) is studied at variable temperatures (25-70 degrees C). Three U(VI)/ODA complexes (UO(2)L, UO(2)L(2)(2-), and UO(2)HL(2)(-)) and three Sm(III)/ODA complexes (SmL(j)((3-2)(j)+) with j = 1, 2, 3) are identified in this temperature range. The formation constants and the molar enthalpies of complexation are determined by potentiometry and calorimetry. The complexation of uranium(VI) and samarium(III) with oxydiacetate becomes more endothermic at higher temperatures. However, the complexes become stronger due to increasingly more positive entropy of complexation at higher temperatures that exceeds the increase in the enthalpy of complexation. The values of the heat capacity of complexation (Delta C(p) degrees in J K(-1) mol(-1)) are 95 +/- 6, 297 +/- 14, and 162 +/- 19 for UO(2)L, UO(2)L(2)(2-), and UO(2)HL(2)(-), and 142 +/- 6, 198 +/- 14, and 157 +/- 19 for SmL(+), SmL(2)(-), and SmL(3)(3-), respectively. The thermodynamic parameters, in conjunction with the structural information from spectroscopy, help to identify the coordination modes in the uranium oxydiacetate complexes. The effect of temperature on the thermodynamics of the complexation is discussed in terms of the electrostatic model and the change in the solvent structure. PMID:12767209

  3. Mode III cleavage of a coin-shaped titanium implant in bone: effect of friction and crack propagation.

    PubMed

    Mathieu, Vincent; Vayron, Romain; Barthel, Etienne; Dalmas, Davy; Soffer, Emmanuel; Anagnostou, Fani; Haiat, Guillaume

    2012-04-01

    Endosseous cementless implants are widely used in orthopaedic, maxillofacial and oral surgery. However, failures are still observed and remain difficult to anticipate as remodelling phenomena at the bone-implant interface are poorly understood. The assessment of the biomechanical strength of the bone-implant interface may improve the understanding of the osseointegration process. An experimental approach based on a mode III cleavage mechanical device aims at understanding the behaviour of a planar bone-implant interface submitted to torsional loading. To do so, coin-shaped titanium implants were inserted on the tibiae of a New Zealand white rabbit for seven weeks. After the sacrifice, mode III cleavage experiments were performed on bone samples. An analytical model was developed to understand the debonding process of the bone-implant interface. The model allowed to assess the values of different parameters related to bone tissue at the vicinity of the implant with the additional assumption that bone adhesion occurs over around 70% of the implant surface, which is confirmed by microscopy images. The approach allows to estimate different quantities related to the bone-implant interface such as: torsional stiffness (around 20.5 N m rad(-1)), shear modulus (around 240 MPa), maximal torsional loading (around 0.056 N.m), mode III fracture energy (around 77.5 N m(-1)) and stress intensity factor (0.27 MPa m(1/2)). This study paves the way for the use of mode III cleavage testing for the investigation of torsional loading strength of the bone-implant interface, which might help for the development and optimization of implant biomaterial, surface treatment and medical treatment investigations. PMID:22402166

  4. Effects of mixed mode I/II loading and grain orientation on crack initiation and stable tearing in 2024-T3 aluminum

    SciTech Connect

    Amstutz, B.E.; Sutton, M.A.; Boone, M.L.; Dawicke, D.S.

    1997-12-01

    The effects of material grain orientation and mixed mode I/II loading on crack initiation and stable tearing in 2.3-mm-thick, unclad 2024-T3 aluminum is experimentally investigated. Mode I experiments were performed on center-cracked specimens with the crack being oriented at various angles relative to the rolling direction. Defining {theta} to be the angle between the normal to the initial crack plane and the loading direction, Mode I/II experiments were performed using an Arcan test fixture for 0{degree} {le} {theta} {le} 90{degree} [corresponding to 90{degree} {ge} {beta} {ge} 0{degree}, where {beta} = atan (K{sub II}/K{sub I})] with the crack oriented either along the rolling direction (T-L) or perpendicular to the rolling direction (L-T). Results indicate that: 1. The Mode I crack tip opening displacement (CTOD) is a strong function of the orientation of the crack relative to the rolling direction; CTOD for a T-L specimen is 0.84 mm, increasing linearly with orientation angle to 1.05 mm for an L-T case. 2. The Mode I/II CTOD increases rapidly during initial increments of crack growth and then decreases towards a constant value as crack growth continues. 3. For {theta} < 68{degree} ({beta} > 29{degree}), all cracks kinked and the Mode I/II plastic zones are similar to rotated Mode I plastic zones throughout the crack growth process. 4. J{sub II} = 0 reasonably predicts the direction of tension-dominated crack growth, but does not predict the transition to shear crack growth which occurs for {theta} {ge} 75{degree}. 5. K{sub II} {ge} K{sub I} for {theta} {approx} 58{degree} ({beta} = 45{degree}) does not quantitatively predict the transition to shear crack growth for {theta} {ge} 75{degree} ({beta} {le} 22{degree}), but does provide an indication of changing conditions in the crack tip region.

  5. Modeling Quantum and Coulomb Effects in Nanoscale Enhancement-Mode Tri-Gate III-V MOSFETs

    NASA Astrophysics Data System (ADS)

    Al-Sibiani, Sameer; Khair, Khadija; Ahmed, Shaikh

    2014-03-01

    Because of limited benefits of strain engineering in extremely scaled silicon devices and lack of demonstration of a performance gain at the product level with nanowires, nanotubes, graphene, and other exotic channel materials, there is a strong motivation to continue device scaling using high-transport III-V (such as InGaAs and InAsSb) channel materials beyond the year 2020. However, there are several challenges with III-V MOSFETs prohibiting their use in high-performance and low-power logic applications. In this work, we investigate the performance of the tri-gate III-V FETs as compared to the planar counterpart, and show how quantum size quantization and random dopant fluctuations (RDF) affect the tri-gate FET characteristics and how to curb these issues. A 3-D fully atomistic quantum-corrected Monte Carlo device simulator has been used in this work. Space-quantization effects have been accounted for via a parameter-free effective potential scheme (and benchmarked against the NEGF approach in the ballistic limit). To treat full Coulomb (electron-ion and electron-electron) interactions, the simulator implements a real-space corrected Coulomb electron dynamics (ED) scheme. Also, the essential bandstructure parameters (bandgap, effective masses, and the density-of-states) have been computed using a 20-band nearest-neighbour sp3d5s* tight-binding scheme.

  6. Adiabatic Survey of Subdwarf B Star Oscillations. III. Effects of Extreme Horizontal Branch Stellar Evolution on Pulsation Modes

    NASA Astrophysics Data System (ADS)

    Charpinet, S.; Fontaine, G.; Brassard, P.; Dorman, Ben

    2002-06-01

    We present the final results of a large, systematic survey of the adiabatic oscillation properties of models of subdwarf B (sdB) stars. This survey is aimed at providing the minimal theoretical background with which to understand the asteroseismological characteristics of the recently discovered class of pulsating sdB stars (the EC 14026 objects). In this paper, the last of a series of three, we consider the effects of stellar evolution on the pulsation eigenmodes of sdB star models. We specifically analyze the adiabatic properties of 149 equilibrium models culled from seven distinct extreme horizontal branch evolutionary sequences. Those have been chosen in order to span fully the region of parameter space where real sdB stars are found. We primarily focus on the evolution of the pulsation periods (P) and the rates of period change (dP/dt), which are both a priori observable quantities. Both the acoustic and gravity branches of stellar oscillations are considered. In light of the results derived in the first two papers of this series, we discuss how the values of P and dP/dt relate to the various structural adjustments that sdB stars undergo during evolution. We find that the acoustic modes react primarily to the secular variations of the surface gravity. In contrast, we identify three main factors that regulate the period evolution of gravity modes: these are the variations brought about by evolution in both the surface gravity and the effective temperature, as well as the onset and growth of a chemical discontinuity between the C-O-enriched nucleus and the helium-rich mantle. We also find, as expected from our previous results, that the period evolution of the pulsation modes in sdB stars is further complicated by trapping effects (microtrapping in the case of p-modes) and by avoided crossings between modes. The latter occur preferentially in certain regions of parameter space. We provide our final results in the form of extensive tabular data in the appendices

  7. Comparison of fatigue crack propagation in Modes I and III

    SciTech Connect

    Ritchie, R.O.

    1985-06-01

    The propagation behavior of fatigue cracks in Mode III (anti-plane shear), measured under cyclic torsion, is described and compared with more commonly encountered behavior under Mode I (tensile opening) loads. It is shown that a unique, global characterization of Mode III growth rates, akin to the Paris ''law'' in Mode I, is only possible if characterizating parameters appropriate to large-scale yielding are employed and allowance is made for crack tip shielding from sliding crack surface interference (i.e., friction and abrasion) between mating fracture surfaces. Based on the crack tip stress and deformation fields for Mode III stationary cracks, the cyclic crack tip displacement, (..delta..CTD/sub III/, and plastic strain intensity range ..delta..GAMMA/sub III/, have been proposed and are found to provide an adequate description of behavior in a range of steels, provided crack surface interference is minimized. The magnitude of this interference, which is somewhat analogous to crack closure in Mode I, is further examined in the light of the complex fractography of torsional fatigue failures and the question of a ''fatigue threshold'' for Mode III crack growth. Finally, micro-mechanical models for cyclic crack extension in anti-plane shear are briefly described, and the contrasting behavior between Mode III and Mode I cracks subjected to simple variable amplitude spectra is examined in terms of the differing role of crack tip blunting and closure in influencing shear, as opposed to tensile opening, modes of crack growth.

  8. Mode III fatigue crack propagation in low alloy steel

    NASA Astrophysics Data System (ADS)

    Ritchie, R. O.; McClintock, F. A.; Nayeb-Hashemi, H.; Ritter, M. A.

    1982-01-01

    To provide a basis for estimating fatigue life in large rotating generator shafts subjected to transient oscillations, a study is made of fatigue crack propagation in Mode III (anti-plane shear) in torsionally-loaded spheroidized AISI4340 steel, and results compared to analogous behavior in Mode I. Torsional S/N curves, determined on smooth bars containing surface defects, showed results surprisingly close to expected unnotched Mode I data, with lifetime increasing from 104 cycles at nominal yield to 106 cycles at half yield. Fatigue crack growth rates in Mode III, measured on circumferentially-notched samples, were found to be slower than in Mode I, although still power-law related to the alternating stress intensity (△K III) for small-scale yielding. Mode III growth rates were only a small fraction (0.002 to 0.0005) of cyclic crack tip displacements (△CTD III) per cycle, in contrast to Mode I where the fraction was much larger (0.1 to 0.01). A micromechanical model for Mode III growth is proposed, where crack advance is considered to take place by a Mode II coalescence of cracks, initiated at inclusions ahead of the main crack front. This mechanism is consistent with the crack increment being a small fraction of △CTDIII per cycle.

  9. Combined mode I-mode III fracture toughness of a particulate reinforced metal-matrix composite

    NASA Technical Reports Server (NTRS)

    Manoharan, M.; Lewandowski, J. J.

    1991-01-01

    The aim of this investigation was to determine the fracture behavior of a particulate reinfored aluminum alloy composite under combined mode I-mode III loading conditions. A modified three-point bend specimen was used to carry out these tests. It was found that the mode I loading condition was energetically most favorable. Addition of mode III components to the system seems to increase the amount of redundant work during fracture without affecting the critical fracture criterion.

  10. Mode III fatigue crack propagation in low alloy steel

    SciTech Connect

    Ritchie, R.O.; McClintock, F.A.; Nayeb-Hashemi, H.; Ritter, M.A.

    1982-01-01

    To provide a basis for estimating fatigue life in large rotating generator shafts subjected to transient oscillations, a study is made of fatigue crack propagation in Mode III (anti-plane shear) in torsionally-loaded spheroidized AISI 4340 steel. Results are compared to analogous behavior in Mode I. The approach investigated the feasibility of using continuum fracture mechanics and preliminary mechanistic modeling to serve as a basis for defect-tolerant life estimation procedures. 38 refs.

  11. Complexation of Curium(III) with DTPA at 10–70 °C: Comparison with Eu(III)–DTPA in Thermodynamics, Luminescence, and Coordination Modes

    SciTech Connect

    Tian, Guoxin; Zhang, Zhiyong; Martin, Leigh R.; Rao, Linfeng

    2015-02-16

    Separation of trivalent actinides (An(III)) from trivalent lanthanides (Ln(III)) is a challenging task because of their nearly identical chemical properties. Diethylenetriaminepentaacetate (DTPA), a key reagent used in the TALSPEAK process that effectively separates An(III) from Ln(III), is believed to play a critical role in the An(III)/Ln(III) separation. However, the underlying principles for the separation based on the difference in the complexation of DTPA with An(III) and Ln(III) remain unclear. In this work, the complexation of DTPA with Cm(III) at 10-70 ºC was investigated by spectrophotometry, luminescence spectroscopy, and microcalorimetry, in conjunction with computational methods. The binding strength, the enthalpy of complexation, the coordination modes, and the luminescence properties are compared between the Cm(III)-DTPA and Eu(III)-DTPA systems. The experimental and computational data have demonstrated that the difference between Cm(III) and Eu(III) in the binding strength with DTPA can be attributed to the stronger covalence bonding between Cm(III) and the nitrogen donors of DTPA.

  12. Is the Pharmacological Mode of Action of Chromium(III) as a Second Messenger?

    PubMed

    Vincent, John B

    2015-07-01

    Although recent studies have shown that chromium (as the trivalent ion) is not an essential trace element, it has been demonstrated to generate beneficial effects at pharmacologically relevant doses on insulin sensitivity and cholesterol levels of rodent models of insulin insensitivity, including models of type 2 diabetes. The mode of action of Cr(III) at a molecular level is still an area of active debate; however, the movement of Cr(III) in the body, particularly in response to changes in insulin concentration, suggests that Cr(III) could act as a second messenger, amplifying insulin signaling. The evidence for the pharmacological mechanism of Cr(III)'s ability to increase insulin sensitivity by acting as a second messenger is reviewed, and proposals for testing this hypothesis are described. PMID:25595680

  13. III-nitride tunable cup-cavities supporting quasi whispering gallery modes from ultraviolet to infrared

    NASA Astrophysics Data System (ADS)

    Shubina, T. V.; Pozina, G.; Jmerik, V. N.; Davydov, V. Yu.; Hemmingsson, C.; Andrianov, A. V.; Kazanov, D. R.; Ivanov, S. V.

    2015-12-01

    Rapidly developing nanophotonics needs microresonators for different spectral ranges, formed by chip-compatible technologies. In addition, the tunable ones are much in demand. Here, we present site-controlled III-nitride monocrystal cup-cavities grown by molecular beam epitaxy. The cup-cavities can operate from ultraviolet to near-infrared, supporting quasi whispering gallery modes up to room temperature. Besides, their energies are identical in large ’ripened’ crystals. In these cavities, the refractive index variation near an absorption edge causes the remarkable effect of mode switching, which is accompanied by the spatial redistribution of electric field intensity with concentration of light into a subwavelength volume. Our results shed light on the mode behavior in semiconductor cavities and open the way for single-growth-run manufacturing the devices comprising an active region and a cavity with tunable mode frequencies.

  14. III-nitride tunable cup-cavities supporting quasi whispering gallery modes from ultraviolet to infrared

    PubMed Central

    Shubina, T. V.; Pozina, G.; Jmerik, V. N.; Davydov, V. Yu.; Hemmingsson, C.; Andrianov, A. V.; Kazanov, D. R.; Ivanov, S. V.

    2015-01-01

    Rapidly developing nanophotonics needs microresonators for different spectral ranges, formed by chip-compatible technologies. In addition, the tunable ones are much in demand. Here, we present site-controlled III-nitride monocrystal cup-cavities grown by molecular beam epitaxy. The cup-cavities can operate from ultraviolet to near-infrared, supporting quasi whispering gallery modes up to room temperature. Besides, their energies are identical in large ’ripened’ crystals. In these cavities, the refractive index variation near an absorption edge causes the remarkable effect of mode switching, which is accompanied by the spatial redistribution of electric field intensity with concentration of light into a subwavelength volume. Our results shed light on the mode behavior in semiconductor cavities and open the way for single-growth-run manufacturing the devices comprising an active region and a cavity with tunable mode frequencies. PMID:26656267

  15. Analysis of mode III crack perpendicular to the interface between two dissimilar strips

    NASA Astrophysics Data System (ADS)

    Matbuly, M. S.

    2008-08-01

    The present work is concerned with the problem of mode III crack perpendicular to the interface of a bi-strip composite. One of these strips is made of a functionally graded material and the other of an isotropic material, which contains an edge crack perpendicular to and terminating at the interface. Fourier transforms and asymptotic analysis are employed to reduce the problem to a singular integral equation which is numerically solved using Gauss-Chebyshev quadrature formulae. Furthermore, a parametric study is carried out to investigate the effects of elastic and geometric characteristics of the composite on the values of stress intensity factor.

  16. III-V-on-silicon anti-colliding pulse-type mode-locked laser.

    PubMed

    Keyvaninia, S; Uvin, S; Tassaert, M; Wang, Z; Fu, X; Latkowski, S; Marien, J; Thomassen, L; Lelarge, F; Duan, G; Lepage, G; Verheyen, P; Van Campenhout, J; Bente, E; Roelkens, G

    2015-07-01

    An anti-colliding pulse-type III-V-on-silicon passively mode-locked laser is presented for the first time based on a III-V-on-silicon distributed Bragg reflector as outcoupling mirror implemented partially underneath the III-V saturable absorber. Passive mode-locking at 4.83 GHz repetition rate generating 3 ps pulses is demonstrated. The generated fundamental RF tone shows a 1.7 kHz 3 dB linewidth. Over 9 mW waveguide coupled output power is demonstrated. PMID:26125366

  17. Subcritical crack growth under mode I, II, and III loading for Coconino sandstone

    NASA Astrophysics Data System (ADS)

    Ko, Tae Young

    In systems subjected to long-term loading, subcritical crack growth is the principal mechanism causing the time-dependent deformation and failure of rocks. Subcritical crack growth is environmentally-assisted crack growth, which can allow cracks to grow over a long period of time at stresses far smaller than their failure strength and at tectonic strain rates. The characteristics of subcritical crack growth can be described by a relationship between the stress intensity factor and the crack velocity. This study presents the results of studies conducted to validate the constant stress-rate test for determining subcritical crack growth parameters in Coconino sandstone, compared with the conventional testing method, the double torsion test. The results of the constant stress-rate test are in good agreement with the results of double torsion test. More importantly, the stress-rate tests can determine the parameter A with a much smaller standard deviation than the double torsion test. Thus the constant stress-rate test seems to be both a valid and preferred test method for determining the subcritical crack growth parameters in rocks. We investigated statistical aspects of the constant stress-rate test. The effects of the number of tests conducted on the subcritical crack growth parameters were examined and minimum specimen numbers were determined. The mean and standard deviation of the subcritical crack growth parameters were obtained by randomly selecting subsets from the original strength data. In addition, the distribution form of the subcritical crack growth parameters and the relation between the parameter n and A were determined. We extended the constant stress-rate test technique to modes II and III subcritical crack growth in rocks. The experimental results of the modes I, II and III tests show that the values of the subcritical crack growth parameters are similar to each other. The subcritical crack growth parameter n value for Coconino sandstone has the range

  18. Helicon modes in uniform plasmas. III. Angular momentum

    NASA Astrophysics Data System (ADS)

    Stenzel, R. L.; Urrutia, J. M.

    2015-09-01

    Helicons are electromagnetic waves with helical phase fronts propagating in the whistler mode in magnetized plasmas and solids. They have similar properties to electromagnetic waves with angular momentum in free space. Helicons are circularly polarized waves carrying spin angular momentum and orbital angular momentum due to their propagation around the ambient magnetic field B0. These properties have not been considered in the community of researchers working on helicon plasma sources, but are the topic of the present work. The present work focuses on the field topology of helicons in unbounded plasmas, not on helicon source physics. Helicons are excited in a large uniform laboratory plasma with a magnetic loop antenna whose dipole axis is aligned along or across B0. The wave fields are measured in orthogonal planes and extended to three dimensions (3D) by interpolation. Since density and B0 are uniform, small amplitude waves from loops at different locations can be superimposed to generate complex antenna patterns. With a circular array of phase shifted loops, whistler modes with angular and axial wave propagation, i.e., helicons, are generated. Without boundaries radial propagation also arises. The azimuthal mode number m can be positive or negative while the field polarization remains right-hand circular. The conservation of energy and momentum implies that these field quantities are transferred to matter which causes damping or reflection. Wave-particle interactions with fast electrons are possible by Doppler shifted resonances. The transverse Doppler shift is demonstrated. Wave-wave interactions are also shown by showing collisions between different helicons. Whistler turbulence does not always have to be created by nonlinear wave-interactions but can also be a linear superposition of waves from random sources. In helicon collisions, the linear and/or orbital angular momenta can be canceled, which results in a great variety of field topologies. The work will

  19. Helicon modes in uniform plasmas. III. Angular momentum

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M.

    2015-09-15

    Helicons are electromagnetic waves with helical phase fronts propagating in the whistler mode in magnetized plasmas and solids. They have similar properties to electromagnetic waves with angular momentum in free space. Helicons are circularly polarized waves carrying spin angular momentum and orbital angular momentum due to their propagation around the ambient magnetic field B{sub 0}. These properties have not been considered in the community of researchers working on helicon plasma sources, but are the topic of the present work. The present work focuses on the field topology of helicons in unbounded plasmas, not on helicon source physics. Helicons are excited in a large uniform laboratory plasma with a magnetic loop antenna whose dipole axis is aligned along or across B{sub 0}. The wave fields are measured in orthogonal planes and extended to three dimensions (3D) by interpolation. Since density and B{sub 0} are uniform, small amplitude waves from loops at different locations can be superimposed to generate complex antenna patterns. With a circular array of phase shifted loops, whistler modes with angular and axial wave propagation, i.e., helicons, are generated. Without boundaries radial propagation also arises. The azimuthal mode number m can be positive or negative while the field polarization remains right-hand circular. The conservation of energy and momentum implies that these field quantities are transferred to matter which causes damping or reflection. Wave-particle interactions with fast electrons are possible by Doppler shifted resonances. The transverse Doppler shift is demonstrated. Wave-wave interactions are also shown by showing collisions between different helicons. Whistler turbulence does not always have to be created by nonlinear wave-interactions but can also be a linear superposition of waves from random sources. In helicon collisions, the linear and/or orbital angular momenta can be canceled, which results in a great variety of field

  20. Comparison of Mode II and III Monotonic and Fatigue Delamination Onset Behavior for Carbon/Toughened Epoxy Composites

    NASA Technical Reports Server (NTRS)

    Li, Jian; OBrien, T. Kevin; Lee, Shaw Ming

    1997-01-01

    Monotonic and fatigue tests were performed to compare the Mode II and III interlaminar fracture toughness and fatigue delamination onset for Tenax-HTA/R6376 carbon/toughened epoxy composites. The Mode II interlaminar fracture toughness and fatigue delamination onset were characterized using the end-notched flexure (ENF) test while the Mode III interlaminar fracture toughness and fatigue delamination onset were characterized by using the edge crack torsion (ECT) test. Monotonic tests show that the Mode III fracture toughness is higher than the Mode II fracture toughness. Both Mode II and III cyclic loading greatly increases the tendency for a delamination to grow relative to a single monotonically increasing load. Under fatigue loading, the Mode III specimen also has a longer life than the Mode II specimen.

  1. Out-of-plane deviation of a mode I+III crack encountering a tougher obstacle

    NASA Astrophysics Data System (ADS)

    Leblond, Jean-Baptiste; Ponson, Laurent

    2016-07-01

    One possible explanation of out-of-plane deviations of cracks loaded in mode I+III was suggested by Gao and Rice in 1986. These authors noted that small in-plane undulations of the crack front, arising from fluctuations of the fracture toughness, should generate a small local mode-II component, causing the crack to depart from planarity. Their analysis is completed here by explicitly calculating the evolution in time of the out-of-plane deviation of a mode-I+III crack encountering a tougher obstacle. The calculation is based on (i) first-order formulae for the stress intensity factors of a crack slightly perturbed within and out of its plane; and (ii) a "double" propagation criterion combining a Griffith condition on the local energy-release rate and a Goldstein-Salganik condition on the local stress intensity factor of mode II. It is predicted that the crack must evolve toward a stationary state, wherein the orthogonal distance from the average fracture plane to the perturbed crack front is constant outside the obstacle and varies linearly across it. We hope that this theoretical prediction will encourage comparison with experiments, and propose a fracture test involving propagation of a mode-I+III crack through a 3D-printed specimen containing some designed obstacle. xml:lang="fr"

  2. The effective degeneracy of protein normal modes.

    PubMed

    Na, Hyuntae; Song, Guang

    2016-01-01

    Normal modes are frequently computed and used to portray protein dynamics and interpret protein conformational changes. In this work, we investigate the nature of normal modes and find that the normal modes of proteins, especially those at the low frequency range (0-600 cm(-1)), are highly susceptible to degeneracy. Two or more modes are degenerate if they have the same frequency and consequently any orthogonal transformation of them also is a valid representation of the mode subspace. Thus, degenerate modes can no longer characterize unique directions of motions as regular modes do. Though the normal modes of proteins are usually of different frequencies, the difference in frequency between neighboring modes is so small that, under even slight structural uncertainty that unavoidably exists in structure determination, it can easily vanish and as a result, a mode becomes effectively degenerate with its neighboring modes. This can be easily observed in that some modes seem to disappear and their matching modes cannot be found when the structure used to compute the modes is modified only slightly. We term this degeneracy the effective degeneracy of normal modes. This work is built upon our recent discovery that the vibrational spectrum of globular proteins is universal. The high density of modes observed in the vibrational frequency spectra of proteins renders their normal modes highly susceptible to degeneracy, under even the smallest structural uncertainty. Indeed, we find the degree of degeneracy of modes is proportional to the density of modes in the vibrational spectrum. This means that for modes at the same frequency, degeneracy is more severe for larger proteins. Degeneracy exists also in the modes of coarse-grained models, but to a much lesser extent than those of all-atom models. In closing, we discuss the implications of the effective degeneracy of normal modes: how it may significantly affect the ways in which normal modes are used in various normal modes

  3. The effective degeneracy of protein normal modes

    NASA Astrophysics Data System (ADS)

    Na, Hyuntae; Song, Guang

    2016-06-01

    Normal modes are frequently computed and used to portray protein dynamics and interpret protein conformational changes. In this work, we investigate the nature of normal modes and find that the normal modes of proteins, especially those at the low frequency range (0–600 cm‑1), are highly susceptible to degeneracy. Two or more modes are degenerate if they have the same frequency and consequently any orthogonal transformation of them also is a valid representation of the mode subspace. Thus, degenerate modes can no longer characterize unique directions of motions as regular modes do. Though the normal modes of proteins are usually of different frequencies, the difference in frequency between neighboring modes is so small that, under even slight structural uncertainty that unavoidably exists in structure determination, it can easily vanish and as a result, a mode becomes effectively degenerate with its neighboring modes. This can be easily observed in that some modes seem to disappear and their matching modes cannot be found when the structure used to compute the modes is modified only slightly. We term this degeneracy the effective degeneracy of normal modes. This work is built upon our recent discovery that the vibrational spectrum of globular proteins is universal. The high density of modes observed in the vibrational frequency spectra of proteins renders their normal modes highly susceptible to degeneracy, under even the smallest structural uncertainty. Indeed, we find the degree of degeneracy of modes is proportional to the density of modes in the vibrational spectrum. This means that for modes at the same frequency, degeneracy is more severe for larger proteins. Degeneracy exists also in the modes of coarse-grained models, but to a much lesser extent than those of all-atom models. In closing, we discuss the implications of the effective degeneracy of normal modes: how it may significantly affect the ways in which normal modes are used in various normal modes

  4. Mixed mode stress field effect in adhesive fracture

    NASA Technical Reports Server (NTRS)

    Anderson, G. P.; Devries, K. L.; Williams, M. L.

    1974-01-01

    Numerical or analytical analyses were performed on seven different test specimens including blister test, 90-degree peel test, torsion test, and various cone tests. These specimens are in general subjected to complex stress fields having various amounts of Mode I, Mode II, and Mode III loads. The specimens were then constructed using polymethyl methacrylate for the adherends and a transparent polyurethane elastomer (Solithane 113) for the adhesive. This combination permitted direct observation of the bondline as load was applied. Although initial debonds as well as bond end termination singularities were present in all specimens, in some cases the debond did not initiate at the singularity points as would normally have been expected. An explanation for this behavior is presented, as well as a comparison of loading mode effect on those specimens for which the debond did propagate from a bond terminus singular point.

  5. Multiple nucleic acid cleavage modes in divergent type III CRISPR systems

    PubMed Central

    Zhang, Jing; Graham, Shirley; Tello, Agnes; Liu, Huanting; White, Malcolm F.

    2016-01-01

    CRISPR-Cas is an RNA-guided adaptive immune system that protects bacteria and archaea from invading nucleic acids. Type III systems (Cmr, Csm) have been shown to cleave RNA targets in vitro and some are capable of transcription-dependent DNA targeting. The crenarchaeon Sulfolobus solfataricus has two divergent subtypes of the type III system (Sso-IIID and a Cmr7-containing variant of Sso-IIIB). Here, we report that both the Sso-IIID and Sso-IIIB complexes cleave cognate RNA targets with a ruler mechanism and 6 or 12 nt spacing that relates to the organization of the Cas7 backbone. This backbone-mediated cleavage activity thus appears universal for the type III systems. The Sso-IIIB complex is also known to possess a distinct ‘UA’ cleavage mode. The predominant activity observed in vitro depends on the relative molar concentration of protein and target RNA. The Sso-IIID complex can cleave plasmid DNA targets in vitro, generating linear DNA products with an activity that is dependent on both the cyclase and HD nuclease domains of the Cas10 subunit, suggesting a role for both nuclease active sites in the degradation of double-stranded DNA targets. PMID:26801642

  6. Cryogenic Interlaminar Fracture Properties of Woven Glass/Epoxy Composite Laminates Under Mixed-Mode I/III Loading Conditions

    NASA Astrophysics Data System (ADS)

    Miura, Masaya; Shindo, Yasuhide; Takeda, Tomo; Narita, Fumio

    2013-08-01

    We characterize the combined Mode I and Mode III delamination fracture behavior of woven glass fiber reinforced polymer (GFRP) composite laminates at cryogenic temperatures. The eight-point bending plate (8PBP) tests were conducted at room temperature, liquid nitrogen temperature (77 K) and liquid helium temperature (4 K) using a new test fixture. A three-dimensional finite element analysis was also performed to calculate the energy release rate distribution along the delamination front, and the delamination fracture toughnesses were evaluated for various mixed-mode I/III ratios. Furthermore, the microscopic examinations of the fracture surfaces were carried out with scanning electron microscopy (SEM), and the mixed-mode I/III delamination fracture mechanisms in the woven GFRP laminates at cryogenic temperatures were assessed. The fracture properties were then correlated with the observed characteristics.

  7. Characterization of the Edge Crack Torsion (ECT) Test for Mode III Fracture Toughness Measurement of Laminated Composites

    NASA Technical Reports Server (NTRS)

    Ratcliffe, James G.

    2004-01-01

    The edge crack torsion (ECT) test is designed to initiate mode III delamination growth in composite laminates. An ECT specimen is a rectangular laminate, containing an edge delamination at the laminate mid-plane. Torsion load is applied to the specimens, resulting in relative transverse shear sliding of the delaminated faces. The test data reduction schemes are intended to yield initiation values of critical mode III strain energy release rate, G(sub IIIc), that are constant with delamination length. The test has undergone several design changes during its development. The objective of this paper was to determine the suitability of the current ECT test design as a mode III fracture test. To this end, ECT tests were conducted on specimens manufactured from IM7/8552 and specimens made from S2/8552 tape laminates. Several specimens, each with different delamination lengths are tested. Detailed, three-dimensional finite element analyses of the specimens were performed. The analysis results were used to calculate the distribution of mode I, mode II, and mode III strain energy release rate along the delamination front. The results indicated that mode III-dominated delamination growth would be initiated from the specimen center. However, in specimens of both material types, the measured values of G(sub IIIc) exhibited significant dependence on delamination length. Furthermore, there was a large amount of scatter in the data. Load-displacement response of the specimens exhibited significant deviation from linearity before specimen failure. X-radiographs of a sample of specimens revealed that damage was initiated in the specimens prior to failure. Further inspection of the failure surfaces is required to identify the damage and determine that mode III delamination is initiated in the specimens.

  8. Dependence of mode I and mixed mode I/III fracture toughness on temperature for a ferritic/martensitic stainless steel

    SciTech Connect

    Li, H.; Jones, R.H.; Gelles, D.S.

    1995-04-01

    The objective is to investigate the dependence of mode I and mixed mode I/III fracture toughness on temperature in the range of {minus}95{degrees}C to 25{degrees}C for a low activation ferritic/martensitic stainless steel (F82-H). Mode I and mixed Mode I/III fracture toughnesses were investigated in the range of {minus}95 to 25{degree}C for a F82-H steel heat-treated in the following way; 1000{degree}C/20 h/air-cooled (AC), 1100{degree}C/7 min/AC, and 700{degree}C/2 h/AC. The results indicate that crack tip plasticity was increased by mixed mode loading, and suggest that at low temperature, mode I fracture toughness is the critical design parameter, but at temperatures above room temperature, expecially concerning fatigure and creep-fatigue crack growth rate, a mixed mode loading may be more harmful than a mode I loading for this steel because a mixed mode loading results in lower fracture toughness and higher crack tip plasticity (or dislocation activity).

  9. Characterization of the Edge Crack Torsion (ECT) Test for Mode III Fracture Toughness Measurement of Laminated Composites

    NASA Technical Reports Server (NTRS)

    Ratcliffe, James G.

    2004-01-01

    The edge crack torsion (ECT) test is designed to initiate mode III delamination growth in composite laminates. The test has undergone several design changes during its development. The objective of this paper was to determine the suitability of the current ECT test design a mode III fracture test. To this end, ECT tests were conducted on specimens manufactured from IM7/8552 and S2/8552 tape laminates. Three-dimensional finite element analyses were performed. The analysis results were used to calculate the distribution of mode I, mode II, and mode III strain energy release rate along the delamination front. The results indicated that mode IIIdominated delamination growth would be initiated from the specimen center. However, in specimens of both material types, the measured values of GIIIc exhibited significant dependence on delamination length. Load-displacement response of the specimens exhibited significant deviation from linearity before specimen failure. X-radiographs of a sample of specimens revealed that damage was initiated in the specimens prior to failure. Further inspection of the failure surfaces is required to identify the damage and determine that mode III delamination is initiated in the specimens.

  10. A comparison of pure mode I and mixed mode I-III cracking of an adhesive containing an open knit cloth carrier

    NASA Technical Reports Server (NTRS)

    Ripling, E. J.; Crosley, P. B.; Johnson, W. S.

    1988-01-01

    Static and fatigue tests were carried out on two commercial modified epoxy film adhesives with a wide open knit polyester carrier in order to compare crack resistance in mode I and mixed mode I-III loading. The carrier cloth is found to have a significant influence on the cracking behavior of the adhesives. The open air net carrier used in this study separates from the adhesive in mode I cracking but shreds during mixed-mode crack extension. This decreases the opening mode toughness but increases the mixed-mode toughness as compared with results obtained earlier using a heavier knit carrier. The results suggest that the type of carrier may have a far larger influence on crack resistance than is generally recognized.

  11. Collisionless microinstabilities in stellarators. III. The ion-temperature-gradient mode

    SciTech Connect

    Plunk, G. G. Helander, P.; Xanthopoulos, P.

    2014-03-15

    We investigate the linear theory of the ion-temperature-gradient (ITG) mode, with the goal of developing a general understanding that may be applied to stellarators. We highlight the Wendelstein 7X (W7-X) device. Simple fluid and kinetic models that follow closely from existing literature are reviewed and two new first-principle models are presented and compared with results from direct numerical simulation. One model investigates the effect of regions of strong localized shear, which are generic to stellarator equilibria. These “shear spikes” are found to have a potentially significant stabilizing affect on the mode; however, the effect is strongest at short wavelengths perpendicular to the magnetic field, and it is found to be significant only for the fastest growing modes in W7-X. A second model investigates the long-wavelength limit for the case of negligible global magnetic shear. The analytic calculation reveals that the effect of the curvature drive enters at second order in the drift frequency, confirming conventional wisdom that the ITG mode is slab-like at long wavelengths. Using flux tube simulations of a zero-shear W7-X configuration, we observe a close relationship to an axisymmetric configuration at a similar parameter point. It is concluded that scale lengths of the equilibrium gradients constitute a good parameter space to characterize the ITG mode. Thus, to optimize the magnetic geometry for ITG mode stability, it may be fruitful to focus on local parameters, such as the magnitude of bad curvature, connection length, and local shear at locations of bad curvature (where the ITG mode amplitude peaks)

  12. Hybrid H-mode scenario with nitrogen seeding and type III ELMs in JET

    NASA Astrophysics Data System (ADS)

    Corre, Y.; Joffrin, E.; Monier-Garbet, P.; Andrew, Y.; Arnoux, G.; Beurskens, M.; Brezinsek, S.; Brix, M.; Buttery, R.; Coffey, I.; Crombe, K.; de La Luna, E.; Felton, R.; Giroud, C.; Hacquin, S.; Hobirk, J.; Huber, A.; Imbeaux, F.; Jachmich, S.; Kempenaars, M.; Litaudon, X.; Leggate, H.; Loarer, T.; Maddison, G.; Rachlew, E.; Rapp, J.; Sauter, O.; Savchkov, A.; Telesca, G.; Widdowson, A.; Zastrow, K. D.; Zimmermann, O.; collaborators, JET-EFDA

    2008-11-01

    The performance of the 'hybrid' H-mode regime (long pulse operation with high neutron fluency) has been extensively investigated in JET during the 2005-2007 experimental campaign up to normalized pressure βN = 3, toroidal magnetic field Bt = 1.7 T, with type I ELMs plasma edge conditions. The optimized external current drive sources, self-generated non-inductive bootstrap current and plasma core stability properties provide a good prospect of achieving a high fusion gain at reduced plasma current for long durations in ITER. One of the remaining issues is the erosion of the divertor target plates associated with the type I ELM regime. A possible solution could be to operate with a plasma edge in the type III ELM regime (reduced transient and stationary heat loads) obtained with impurity seeding. An integrated hybrid type III ELM regime with a normalized pressure βN = 2.6 (PNBI ~ 20-22 MW) and a thermal confinement factor of H_{98}^\\ast (y,2)\\sim 0.83 has been recently successfully developed on JET with nitrogen seeding. This scenario shows good plasma edge condition (compatible with the future ITER-like wall on JET) and moderate MHD activity. In this paper, we report on the experimental development of the scenario (with plasma current Ip = 1.7 MA and magnetic field Bt = 1.7 T) and the trade-off between heat load reduction at the target plates and global confinement due to nitrogen seeding and type III ELM working conditions.

  13. Mode Transitions in Hall Effect Thrusters

    NASA Technical Reports Server (NTRS)

    Sekerak, Michael J.; Longmier, Benjamin W.; Gallimore, Alec D.; Brown, Daniel L.; Hofer, Richard R.; Polk, James E.

    2013-01-01

    Mode transitions have been commonly observed in Hall Effect Thruster (HET) operation where a small change in a thruster operating parameter such as discharge voltage, magnetic field or mass flow rate causes the thruster discharge current mean value and oscillation amplitude to increase significantly. Mode transitions in a 6-kW-class HET called the H6 are induced by varying the magnetic field intensity while holding all other operating parameters constant and measurements are acquired with ion saturation probes and ultra-fast imaging. Global and local oscillation modes are identified. In the global mode, the entire discharge channel oscillates in unison and azimuthal perturbations (spokes) are either absent or negligible. Downstream azimuthally spaced probes show no signal delay between each other and are very well correlated to the discharge current signal. In the local mode, signals from the azimuthally spaced probes exhibit a clear delay indicating the passage of "spokes" and are not well correlated to the discharge current. These spokes are localized oscillations propagating in the ExB direction that are typically 10-20% of the mean value. In contrast, the oscillations in the global mode can be 100% of the mean value. The transition between global and local modes occurs at higher relative magnetic field strengths for higher mass flow rates or higher discharge voltages. The thrust is constant through mode transition but the thrust-to-power decreased by 25% due to increasing discharge current. The plume shows significant differences between modes with the global mode significantly brighter in the channel and the near-field plasma plume as well as exhibiting a luminous spike on thruster centerline. Mode transitions provide valuable insight to thruster operation and suggest improved methods for thruster performance characterization.

  14. Energetic particle effects on global MHD modes

    SciTech Connect

    Cheng, C.Z.

    1990-01-01

    The effects of energetic particles on MHD type modes are studied by analytical theories and the nonvariational kinetic-MHD stability code (NOVA-K). In particular we address the problems of (1) the stabilization of ideal MHD internal kink modes and the excitation of resonant fishbone'' internal modes and (2) the alpha particle destabilization of toroidicity-induced Alfven eigenmodes (TAE) via transit resonances. Analytical theories are presented to help explain the NOVA-K results. For energetic trapped particles generated by neutral-beam injection (NBI) or ion cyclotron resonant heating (ICRH), a stability window for the n=1 internal kink mode in the hot particle beat space exists even in the absence of core ion finite Larmor radius effect (finite {omega}{sub *i}). On the other hand, the trapped alpha particles are found to resonantly excite instability of the n=1 internal mode and can lower the critical beta threshold. The circulating alpha particles can strongly destabilize TAE modes via inverse Landau damping associated with the spatial gradient of the alpha particle pressure. 23 refs., 5 figs.

  15. A Mixed-Mode (I-II) Fracture Criterion for AS4/8552 Carbon/Epoxy Composite Laminate

    NASA Astrophysics Data System (ADS)

    Karnati, Sidharth Reddy

    A majority of aerospace structures are subjected to bending and stretching loads that introduce peel and shear stresses between the plies of a composite laminate. These two stress components cause a combination of mode I and II fracture modes in the matrix layer of the composite laminate. The most common failure mode in laminated composites is delamination that affects the structural integrity of composite structures. Damage tolerant designs of structures require two types of materials data: mixed-mode (I-II) delamination fracture toughness that predicts failure and delamination growth rate that predicts the life of the structural component. This research focuses determining mixed-mode (I-II) fracture toughness under a combination of mode I and mode II stress states and then a fracture criterion for AS4/8552 composite laminate, which is widely used in general aviation. The AS4/8552 prepreg was supplied by Hexcel Corporation and autoclave fabricated into a 20-ply unidirectional laminate with an artificial delamination by a Fluorinated Ethylene Propylene (FEP) film at the mid-plane. Standard split beam specimens were prepared and tested in double cantilever beam (DCB) and end notched flexure modes to determine mode I (GIC) and II (GIIC) fracture toughnesses, respectively. The DCB specimens were also tested in a modified mixed-mode bending apparatus at GIIm /GT ratios of 0.18, 0.37, 0.57 and 0.78, where GT is total and GIIm is the mode II component of energy release rates. The measured fracture toughness, GC, was found to follow the locus a power law equation. The equation was validated for the present and literature experimental data.

  16. A plane stress finite element model for elastic-plastic mode I/II crack growth

    NASA Astrophysics Data System (ADS)

    James, Mark Anthony

    A finite element program has been developed to perform quasi-static, elastic-plastic crack growth simulations. The model provides a general framework for mixed-mode I/II elastic-plastic fracture analysis using small strain assumptions and plane stress, plane strain, and axisymmetric finite elements. Cracks are modeled explicitly in the mesh. As the cracks propagate, automatic remeshing algorithms delete the mesh local to the crack tip, extend the crack, and build a new mesh around the new tip. State variable mapping algorithms transfer stresses and displacements from the old mesh to the new mesh. The von Mises material model is implemented in the context of a non-linear Newton solution scheme. The fracture criterion is the critical crack tip opening displacement, and crack direction is predicted by the maximum tensile stress criterion at the crack tip. The implementation can accommodate multiple curving and interacting cracks. An additional fracture algorithm based on nodal release can be used to simulate fracture along a horizontal plane of symmetry. A core of plane strain elements can be used with the nodal release algorithm to simulate the triaxial state of stress near the crack tip. Verification and validation studies compare analysis results with experimental data and published three-dimensional analysis results. Fracture predictions using nodal release for compact tension, middle-crack tension, and multi-site damage test specimens produced accurate results for residual strength and link-up loads. Curving crack predictions using remeshing/mapping were compared with experimental data for an Arcan mixed-mode specimen. Loading angles from 0 degrees to 90 degrees were analyzed. The maximum tensile stress criterion was able to predict the crack direction and path for all loading angles in which the material failed in tension. Residual strength was also accurately predicted for these cases.

  17. Electromagnetic effects on geodesic acoustic modes

    SciTech Connect

    Bashir, M. F.; Smolyakov, A. I.; Elfimov, A. G.; Melnikov, A. V.; Murtaza, G.

    2014-08-15

    By using the full electromagnetic drift kinetic equations for electrons and ions, the general dispersion relation for geodesic acoustic modes (GAMs) is derived incorporating the electromagnetic effects. It is shown that m = 1 harmonic of the GAM mode has a finite electromagnetic component. The electromagnetic corrections appear for finite values of the radial wave numbers and modify the GAM frequency. The effects of plasma pressure β{sub e}, the safety factor q, and the temperature ratio τ on GAM dispersion are analyzed.

  18. Electrically driven hybrid Si/III-V Fabry-Pérot lasers based on adiabatic mode transformers.

    PubMed

    Ben Bakir, B; Descos, A; Olivier, N; Bordel, D; Grosse, P; Augendre, E; Fulbert, L; Fedeli, J M

    2011-05-23

    We report the first demonstration of an electrically driven hybrid silicon/III-V laser based on adiabatic mode transformers. The hybrid structure is formed by two vertically superimposed waveguides separated by a 100-nm-thick SiO2 layer. The top waveguide, fabricated in an InP/InGaAsP-based heterostructure, serves to provide optical gain. The bottom Si-waveguides system, which supports all optical functions, is constituted by two tapered rib-waveguides (mode transformers), two distributed Bragg reflectors (DBRs) and a surface-grating coupler. The supermodes of this hybrid structure are controlled by an appropriate design of the tapers located at the edges of the gain region. In the middle part of the device almost all the field resides in the III-V waveguide so that the optical mode experiences maximal gain, while in regions near the III-V facets, mode transformers ensure an efficient transfer of the power flow towards Si-waveguides. The investigated device operates under quasi-continuous wave regime. The room temperature threshold current is 100 mA, the side-mode suppression ratio is as high as 20 dB, and the fiber-coupled output power is ~7 mW. PMID:21643289

  19. The equilibrium concentration of hydrogen atoms ahead of a mixed mode I-mode III crack tip in single crystal iron

    SciTech Connect

    Zhang, T.Y.; Hack, J.E.

    1999-01-01

    Calculations of the equilibrium hydrogen concentration profiles about a mixed ode I-mode III crack in single crystal iron were performed. Both material anisotropy and the tetragonal nature of the distortion induced in the iron crystal structure by interstitial hydrogen were incorporated. Results show that, unlike the case of a spherical distortion, a strong coupling exists between the strain field of the interstitial hydrogen and the stress field of the crack for orientations of the crack plane that are not coincident with the cube axes of the lattice. As a result, the predicated enhancement of hydrogen in the crack tip region increases with increasing levels of mode III loading for those orientations. The results may help reconcile conflicting observations concerning the potential role of shear stresses in hydrogen embrittlement and preferential cracking of grains ahead of loaded crack tips in sustained load cracking experiments.

  20. A streamlined failure mode and effects analysis

    SciTech Connect

    Ford, Eric C. Smith, Koren; Terezakis, Stephanie; Croog, Victoria; Gollamudi, Smitha; Gage, Irene; Keck, Jordie; DeWeese, Theodore; Sibley, Greg

    2014-06-15

    Purpose: Explore the feasibility and impact of a streamlined failure mode and effects analysis (FMEA) using a structured process that is designed to minimize staff effort. Methods: FMEA for the external beam process was conducted at an affiliate radiation oncology center that treats approximately 60 patients per day. A structured FMEA process was developed which included clearly defined roles and goals for each phase. A core group of seven people was identified and a facilitator was chosen to lead the effort. Failure modes were identified and scored according to the FMEA formalism. A risk priority number,RPN, was calculated and used to rank failure modes. Failure modes with RPN > 150 received safety improvement interventions. Staff effort was carefully tracked throughout the project. Results: Fifty-two failure modes were identified, 22 collected during meetings, and 30 from take-home worksheets. The four top-ranked failure modes were: delay in film check, missing pacemaker protocol/consent, critical structures not contoured, and pregnant patient simulated without the team's knowledge of the pregnancy. These four failure modes hadRPN > 150 and received safety interventions. The FMEA was completed in one month in four 1-h meetings. A total of 55 staff hours were required and, additionally, 20 h by the facilitator. Conclusions: Streamlined FMEA provides a means of accomplishing a relatively large-scale analysis with modest effort. One potential value of FMEA is that it potentially provides a means of measuring the impact of quality improvement efforts through a reduction in risk scores. Future study of this possibility is needed.

  1. An assessment of BWR (boiling water reactor) Mark III containment challenges, failure modes, and potential improvements in performance

    SciTech Connect

    Schroeder, J.A.; Pafford, D.J.; Kelly, D.L.; Jones, K.R.; Dallman, F.J. )

    1991-01-01

    This report describes risk-significant challenges posed to Mark III containment systems by severe accidents as identified for Grand Gulf. Design similarities and differences between the Mark III plants that are important to containment performance are summarized. The accident sequences responsible for the challenges and the postulated containment failure modes associated with each challenge are identified and described. Improvements are discussed that have the potential either to prevent or delay containment failure, or to mitigate the offsite consequences of a fission product release. For each of these potential improvements, a qualitative analysis is provided. A limited quantitative risk analysis is provided for selected potential improvements. 21 refs., 5 figs., 46 tabs.

  2. Mode I and mixed I/III crack initiation and propagation behavior of V-4Cr-4Ti alloy at 25{degrees}C

    SciTech Connect

    Li, H.X.; Kurtz, R.J.; Jones, R.H.

    1997-04-01

    The mode I and mixed-mode I/III fracture behavior of the production-scale heat (No. 832665) of V-4Cr-4Ti has been investigated at 25{degrees}C using compact tension (CT) specimens for a mode I crack and modified CT specimens for a mixed-mode I/III crack. The mode III to mode I load ratio was 0.47. Test specimens were vacuum annealed at 1000{degrees}C for 1 h after final machining. Both mode I and mixed-mode I/III specimens were fatigue cracked prior to J-integral testing. It was noticed that the mixed-mode I/III crack angle decreased from an initial 25 degrees to approximately 23 degrees due to crack plane rotation during fatigue cracking. No crack plane rotation occurred in the mode I specimen. The crack initiation and propagation behavior was evaluated by generating J-R curves. Due to the high ductility of this alloy and the limited specimen thickness (6.35 mm), plane strain requirements were not met so valid critical J-integral values were not obtained. However, it was found that the crack initiation and propagation behavior was significantly different between the mode I and the mixed-mode I/III specimens. In the mode I specimen crack initiation did not occur, only extensive crack tip blunting due to plastic deformation. During J-integral testing the mixed-mode crack rotated to an increased crack angle (in contrast to fatigue precracking) by crack blunting. When the crack initiated, the crack angle was about 30 degrees. After crack initiation the crack plane remained at 30 degrees until the test was completed. Mixed-mode crack initiation was difficult, but propagation was easy. The fracture surface of the mixed-mode specimen was characterized by microvoid coalescence.

  3. Electroelastic effect of thickness mode langasite resonators.

    PubMed

    Zhang, Haifeng; Turner, Joseph A; Yang, Jiashi; Kosinski, John A

    2007-10-01

    Langasite is a very promising material for resonators due to its good temperature behavior and high piezoelectric coupling, low acoustic loss, and high Q factor. The biasing effect for langasite resonators is crucial for resonator design. In this article, the resonant frequency shift of a thickness-mode langasite resonator is analyzed with respect to a direct current (DC) electric field applied in the thickness direction. The vibration modes of a thin langasite plate fully coated with an electrode are analyzed. The analysis is based on the theory for small fields superposed on a bias in electroelastic bodies and the first-order perturbation integral theory. The electroelastic effect of the resonator is analyzed by both analytical and finite-element methods. The complete set of nonlinear elastic, piezoelectric, dielectric permeability, and electrostrictive constants of langasite is used in the theoretical and numerical analysis. The sensitivity of electroelastic effect to nonlinear material constants is analyzed. PMID:18019250

  4. Effective plasmonic mode-size converter.

    PubMed

    Park, Hae-Ryeong; Park, Jong-Moon; Kim, Min-su; Ju, Jung Jin; Son, Jung-Han; Lee, Myung-Hyun

    2011-10-24

    Plasmonic mode-size converters (PMSCs) for long-range surface plasmon polaritons (LR-SPPs) at the wavelength of 1.55 μm are presented. The PMSC is composed of an insulator-metal-insulator waveguide (IMI-W), a laterally tapered insulator-metal-insulator-metal-insulator waveguide (LT-IMIMI-W), and an IMIMI-W in series. The mode-intensity sizes of the LR-SPPs for the IMI-W and the IMIMI-W were not only calculated using a finite element method but were also experimentally measured. The propagation losses of the IMI-W and the IMIMI-W as well as the coupling losses between them were analyzed by the cut-back method to investigate the effect of LT-IMIMI-Ws. By using the PMSC with a ~27 ° angled LT-IMIMI-W, the coupling loss between a polarization-maintaining fiber and a 3 μm-wide IMIMI-W was reduced by ~3.4 dB. Moreover, the resulting mode-intensity in the output of the PMSC was squeezed to ~35% of the mode-intensity in the input IMI-W. The PMSC may be potentially useful for bridging micro- to nano-plasmonic integrated circuits. PMID:22109009

  5. Characterization of the apoLp-III/LPS complex: insight in the mode of binding interaction

    PubMed Central

    Oztug, Merve; Martinon, Daisy; Weers, Paul M.M.

    2012-01-01

    Apolipoproteins are able to associate with lipopolysaccharides (LPS), potentially providing protection against septic shock. To gain insight in the molecular details of this binding interaction, apolipophorin III (apoLp-III) from Galleria mellonella was used as a model. The binding of apoLp-III to LPS was optimal around 37–40 °C, close to the LPS phase transition temperature. ApoLp-III formed complexes with LPS from E. coli (serotype O55:B5) with a diameter of 24 nm, a molecular weight of ~390 kDa, containing four molecules of apoLp-III and 24 molecules of LPS. The LPS-bound form of the protein was substantially more resistant to guanidine-induced denaturation compared to unbound protein. The denaturation profile displayed a multiphase character with a steep drop in secondary structure between 0–1 M guanidine, and a slower decrease above 1 M guanidine HCl. In contrast, apoLp-III bound to detoxified LPS was only slightly more resistant to guanidine HCl induced denaturation compared to unbound protein. Analysis of size-exclusion FPLC elution profiles of mixtures of apoLp-III with LPS or detoxified LPS indicated a much weaker binding interaction with detoxified LPS compared to intact LPS. These results indicate that apoLp-III initially interacts with exposed carbohydrate regions, but that the lipid A region is required for a more stable LPS binding interaction. PMID:22779761

  6. Period-Luminosity relations derived from the OGLE-III first-overtone mode Cepheids in the Magellanic Clouds

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Anupam; Ngeow, Chow-Choong; Kanbur, Shashi M.; Singh, Harinder P.

    2016-06-01

    We present multiband Period-Luminosity (PL) relations for first-overtone mode Cepheids in the Small Magellanic Cloud (SMC). We derive optical band PL relations and the Wesenheit function using VI mean magnitudes from the Optical Gravitational Lensing Experiment (OGLE-III) survey. We cross-match OGLE-III first-overtone mode Cepheids to the 2MASS and SAGE-SMC catalogues to derive PL relations at near-infrared (JHKs) and mid-infrared (3.6 and 4.5 μm) wavelengths. We test for possible non-linearities in these PL relations using robust statistical tests and find a significant break only in the optical band PL relations at 2.5 d for first-overtone mode Cepheids. We do not find statistical evidence for a non-linearity in these PL relations at 1 d. The multiband PL relations for fundamental-mode Cepheids in the SMC also exhibit a break at 2.5 d. We suggest that the period break around 2.5 d is related to sharp changes in the light-curve parameters for SMC Cepheids. We also derive new optical and mid-infrared band PL relations for first-overtone mode Cepheids in the Large Magellanic Cloud (LMC). We compare multiband PL relations for first-overtone mode Cepheids in the Magellanic Clouds and find a significant difference in the slope of the V-band PL relations but not for I-band PL relations. The slope of PL relations are found to be consistent in most of the infrared bands. A relative distance modulus of Δμ = 0.49 ± 0.02 mag between the two clouds is estimated using multiband PL relations for the first-overtone mode Cepheids in the SMC and LMC.

  7. Failure modes and effects analysis automation

    NASA Technical Reports Server (NTRS)

    Kamhieh, Cynthia H.; Cutts, Dannie E.; Purves, R. Byron

    1988-01-01

    A failure modes and effects analysis (FMEA) assistant was implemented as a knowledge based system and will be used during design of the Space Station to aid engineers in performing the complex task of tracking failures throughout the entire design effort. The three major directions in which automation was pursued were the clerical components of the FMEA process, the knowledge acquisition aspects of FMEA, and the failure propagation/analysis portions of the FMEA task. The system is accessible to design, safety, and reliability engineers at single user workstations and, although not designed to replace conventional FMEA, it is expected to decrease by many man years the time required to perform the analysis.

  8. Blockade of HERG channels by the class III antiarrhythmic azimilide: mode of action

    PubMed Central

    Busch, A E; Eigenberger, B; Jurkiewicz, N K; Salata, J J; Pica, A; Suessbrich, H; Lang, F

    1998-01-01

    The class III antiarrhythmic azimilide has previously been shown to inhibit IKs and IKr in guinea-pig cardiac myocytes and IKs (minK) channels expressed in Xenopus oocytes. Because HERG channels underly the conductance IKr in human heart, the effects of azimilide on HERG channels expressed in Xenopus oocytes were the focus of the present study.In contrast to other well characterized HERG channel blockers, azimilide blockade was reverse use-dependent, i.e., the relative block and apparent affinity of azimilide decreased with an increase in channel activation frequency. Azimilide blocked HERG channels at 0.1 and 1 Hz with IC50 s of 1.4 μM and 5.2  μM respectively.In an envelope of tail test, HERG channel blockade increased with increasing channel activation, indicating binding of azimilide to open channels.Azimilide blockade of HERG channels expressed in Xenopus oocytes and IKr in mouse AT-1 cells was decreased under conditions of high [K+]e, whereas block of slowly activating IKs channels was not affected by changes in [K+]e.In summary, azimilide is a blocker of cardiac delayed rectifier channels, IKs and HERG. Because of the distinct effects of stimulation frequency and [K+]e on azimilide block of IKr and IKs channels, we conclude that the relative contribution of block of each of these cardiac delayed rectifier channels depends on heart frequency. [K+]e and regulatory status of the respective channels. PMID:9484850

  9. Failure-Modes-And-Effects Analysis Of Software Logic

    NASA Technical Reports Server (NTRS)

    Garcia, Danny; Hartline, Thomas; Minor, Terry; Statum, David; Vice, David

    1996-01-01

    Rigorous analysis applied early in design effort. Method of identifying potential inadequacies and modes and effects of failures caused by inadequacies (failure-modes-and-effects analysis or "FMEA" for short) devised for application to software logic.

  10. Evaluation of the split cantilever beam for mode III delamination testing

    NASA Technical Reports Server (NTRS)

    Martin, Roderick, H.

    1991-01-01

    A test rig for testing a thick split cantilever beam for scissoring delamination (mode 3) fracture toughness was developed. A 3-D finite element analysis was conducted on the test specimen to determine the strain energy release rate, G, distribution along the delamination front. The virtual crack closure technique was used to calculate the G components resulting from interlaminar tension, GI, interlaminar sliding shear, GII, and interlaminar tearing shear, GIII. The finite element analysis showed that at the delamination front no GI component existed, but a GII component was present in addition to a GIII component. Furthermore, near the free edges, the GII component was significantly higher than the GIII component. The GII/GIII ratio was found to increase with delamination length but was insensitive to the beam depth. The presence of GII at the delamination front was verified experimentally by examination of the failure surfaces. At the center of the beam, where the failure was in mode 3, there was significant fiber bridging. However, at the edges of the beam where the failure was in mode 3, there was no fiber bridging and mode 2 shear hackles were observed. Therefore, it was concluded that the split cantilever beam configuration does not represent a pure mode 3 test. The experimental work showed that the mode 2 fracture toughness, GIIc, must be less than the mode 3 fracture toughness, GIIIc. Therefore, a conservative approach to characterizing mode 3 delamination is to equate GIIIc to GIIc.

  11. A Mixed-Mode I/II Fracture Criterion and Its Application in Crack Growth Predictions

    NASA Technical Reports Server (NTRS)

    Sutton, Michael A.; Deng, Xiaomin; Ma, Fashang; Newman, James S., Jr.

    1999-01-01

    A crack tip opening displacement (CTOD)-based, mixed mode fracture criterion is developed for predicting the onset and direction of crack growth. The criterion postulates that crack growth occurs in either the Mode I or Mode II direction, depending on whether the maximum in either the opening or the shear component of CTOD, measured at a specified distance behind the crack tip, attains a critical value. For crack growth direction prediction, the proposed CTOD criterion is shown to be equivalent to seven commonly used crack growth criteria under linearly elastic and asymptotic conditions. Under elastic-plastic conditions the CTOD criterion's prediction of the dependence of the crack growth direction on the crack-up mode mixity is in excellent agreement with the Arcan test results. Furthermore, the CTOD criterion correctly predicts the existence of a crack growth transition from mode I to mode II as the mode mixity approaches the mode II loading condition. The proposed CTOD criterion has been implemented in finite element crack growth simulation codes Z1P2DL and FRANC2DL to predict the crack growth paths in (a) a modified Arcan test specimen and fixture made of AL 2024-T34 and (b) a double cantilever beam (DCB) specimen made of AL 7050. A series of crack growth simulations have been carried out for the crack growth tests in the Arcan and DCB specimens and the results further demonstrate the applicability of the mixed mode CTOD fracture criterion crack growth predictions and residual strength analyses for airframe materials.

  12. The Fundamental Solutions for the Stress Intensity Factors of Modes I, II And III. The Axially Symmetric Problem

    NASA Astrophysics Data System (ADS)

    Rogowski, B.

    2015-05-01

    The subject of the paper are Green's functions for the stress intensity factors of modes I, II and III. Green's functions are defined as a solution to the problem of an elastic, transversely isotropic solid with a penny-shaped or an external crack under general axisymmetric loadings acting along a circumference on the plane parallel to the crack plane. Exact solutions are presented in a closed form for the stress intensity factors under each type of axisymmetric ring forces as fundamental solutions. Numerical examples are employed and conclusions which can be utilized in engineering practice are formulated.

  13. (-)-Carvone: antispasmodic effect and mode of action.

    PubMed

    Souza, Fábia Valéria M; da Rocha, Marcelly Barbosa; de Souza, Damião P; Marçal, Rosilene Moretti

    2013-03-01

    (-)-Carvone is a monoterpene ketone found in spearmint (Mentha spicata var. crispa) essential oil that is widely used as an odor and flavor additive. An intestinal antispasmodic effect was recently reported for (-)-carvone, and it has been shown to be more potent than its (+)-antipode. The mechanism of (-)-carvone action in the intestines has not been investigated. To gain a better understanding of the (-)-carvone antispasmodic effect, we investigated its pharmacological effects in the guinea pig ileum. Terminal portions of the ileum were mounted for isotonic contraction recordings. The effect of (-)-carvone was compared with that of the classical calcium channel blocker (CCB) verapamil. In isolated ileal smooth muscle, (-)-carvone did not produce direct contractile or relaxation responses and did not modify electrically elicited contractions or low K(+)-evoked contractions. The submaximal contractions induced by histamine (p<0.001), BaCl2 (p<0.05), and carbachol (p<0.01) were significantly reduced by (-)-carvone. The contractile response elicited by high concentrations of carbachol was reduced but not abolished by (-)-carvone. No additive action was detected with co-incubation of (-)-carvone and verapamil on carbachol-induced contraction. (-)-Carvone reduced the contraction induced by high K(+) and was almost 100 times more potent than verapamil. Thus, (-)-carvone showed a typical and potent CCB-like action. Many effects described for both (-)-carvone and spearmint oil can be explained as a CCB-like mode of action. PMID:23103297

  14. Drift effects on electromagnetic geodesic acoustic modes

    NASA Astrophysics Data System (ADS)

    Sgalla, R. J. F.

    2015-02-01

    A two fluid model with parallel viscosity is employed to derive the dispersion relation for electromagnetic geodesic acoustic modes (GAMs) in the presence of drift (diamagnetic) effects. Concerning the influence of the electron dynamics on the high frequency GAM, it is shown that the frequency of the electromagnetic GAM is independent of the equilibrium parallel current but, in contrast with purely electrostatic GAMs, significantly depends on the electron temperature gradient. The electromagnetic GAM may explain the discrepancy between the f ˜ 40 kHz oscillation observed in tokamak TCABR [Yu. K. Kuznetsov et al., Nucl. Fusion 52, 063044 (2012)] and the former prediction for the electrostatic GAM frequency. The radial wave length associated with this oscillation, estimated presently from this analytical model, is λr ˜ 25 cm, i.e., an order of magnitude higher than the usual value for zonal flows (ZFs).

  15. Drift effects on electromagnetic geodesic acoustic modes

    SciTech Connect

    Sgalla, R. J. F.

    2015-02-15

    A two fluid model with parallel viscosity is employed to derive the dispersion relation for electromagnetic geodesic acoustic modes (GAMs) in the presence of drift (diamagnetic) effects. Concerning the influence of the electron dynamics on the high frequency GAM, it is shown that the frequency of the electromagnetic GAM is independent of the equilibrium parallel current but, in contrast with purely electrostatic GAMs, significantly depends on the electron temperature gradient. The electromagnetic GAM may explain the discrepancy between the f ∼ 40 kHz oscillation observed in tokamak TCABR [Yu. K. Kuznetsov et al., Nucl. Fusion 52, 063044 (2012)] and the former prediction for the electrostatic GAM frequency. The radial wave length associated with this oscillation, estimated presently from this analytical model, is λ{sub r} ∼ 25 cm, i.e., an order of magnitude higher than the usual value for zonal flows (ZFs)

  16. Fatigue delamination growth in woven glass/epoxy composite laminates under mixed-mode II/III loading conditions at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Takeda, Tomo; Miura, Masaya; Shindo, Yasuhide; Narita, Fumio

    2013-12-01

    We investigate the cryogenic delamination growth behavior in woven glass fiber reinforced polymer (GFRP) composite laminates under mixed-mode II/III fatigue loading. Fatigue delamination tests were conducted with six-point bending plate (6PBP) specimens at room temperature, liquid nitrogen temperature (77 K) and liquid helium temperature (4 K), and the delamination growth rate data for various mixed-mode ratios of Modes II and III were obtained. The energy release rate was evaluated using the three-dimensional finite element method. In addition, the fatigue delamination growth mechanisms were characterized by scanning electron microscopic observations of the specimen fracture surfaces.

  17. 25 CFR 291.15 - How long do Class III gaming procedures remain in effect?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false How long do Class III gaming procedures remain in effect... ENTERPRISES CLASS III GAMING PROCEDURES § 291.15 How long do Class III gaming procedures remain in effect? Class III gaming procedures remain in effect for the duration specified in the procedures or...

  18. Effects of Jigsaw III Technique on Achievement in Written Expression

    ERIC Educational Resources Information Center

    Sahin, Abdullah

    2011-01-01

    The objective of this paper is to compare the Jigsaw III technique (of cooperative learning) with the instructional teacher-centered teaching method in six graders in terms of the effect of written expression on their academic success. The universe of the study consists of 71 sixth-grade students studying during 2009-2010 academic term in a…

  19. Optical modes in slab waveguides with magnetoelectric effect

    NASA Astrophysics Data System (ADS)

    Talebi, Nahid

    2016-05-01

    Optical modes in anisotropic slab waveguides with topological and chiral magnetoelectric effects are investigated analytically, by deriving the closed-form characteristic equations of the modes and hence computing the dispersion-diagrams. In order to compute the characteristic equations, a vector-potential approach is introduced by incorporating a generalized Lorentz gauge, and the Helmholtz equations are derived correspondingly. It will be shown that the formation of the complex modes and hybridization of the optical modes in such slab waveguides is inevitable. Moreover, when the tensorial form of the permittivity in the waveguide allows for a hyperbolic dispersion, complex transition from the photonic kinds of modes to the plasmonic modes is expected.

  20. Mode Contributions to the Casimir Effect

    NASA Astrophysics Data System (ADS)

    Intravaia, F.; Henkel, C.

    2010-04-01

    Applying a sum-over-modes approach to the Casimir interaction between two plates with finite conductivity, we isolate and study the contributions of surface plasmons and Foucault (eddy current) modes. We show in particular that for the TE-polarization eddy currents provide a repulsive force that cancels, at high temperatures, the Casimir free energy calculated with the plasma model.

  1. Electron cyclotron maser emission mode coupling to the z-mode on a longitudinal density gradient in the context of solar type III bursts

    SciTech Connect

    Pechhacker, R.; Tsiklauri, D.

    2012-11-15

    A beam of super-thermal, hot electrons was injected into maxwellian plasma with a density gradient along a magnetic field line. 1.5D particle-in-cell simulations were carried out which established that the EM emission is produced by the perpendicular component of the beam injection momentum. The beam has a positive slope in the distribution function in perpendicular momentum phase space, which is the characteristic feature of a cyclotron maser. The cyclotron maser in the overdense plasma generates emission at the electron cyclotron frequency. The frequencies of generated waves were too low to propagate away from the injection region, hence the wavelet transform shows a pulsating wave generation and decay process. The intensity pulsation frequency is twice the relativistic cyclotron frequency. Eventually, a stable wave packet formed and could mode couple on the density gradient to reach frequencies of the order of the plasma frequency that allowed for propagation. The emitted wave is likely to be a z-mode wave. The total electromagnetic energy generated is of the order of 0.1% of the initial beam kinetic energy. The proposed mechanism is of relevance to solar type III radio bursts, as well as other situations, when the injected electron beam has a non-zero perpendicular momentum, e.g., magnetron.

  2. Achirality in the low temperature structure and lattice modes of tris(acetylacetonate)iron(iii).

    PubMed

    Ellis, Thomas K; Kearley, Gordon J; Piltz, Ross O; Jayasooriya, Upali A; Stride, John A

    2016-05-10

    Tris(acetylacteonate) iron(iii) is a relatively ubiquitous mononuclear inorganic coordination complex. The bidentate nature of the three acetylacteonate ligands coordinating around a single centre inevitably leads to structural isomeric forms, however whether or not this relates to chirality in the solid state has been questioned in the literature. Variable temperature neutron diffraction data down to T = 3 K, highlights the dynamic nature of the ligand environment, including the motions of the hydrogen atoms. The Fourier transform of the molecular dynamics simulation based on the experimentally determined structure was shown to closely reproduce the low temperature vibrational density of states obtained using inelastic neutron scattering. PMID:27109447

  3. Effects of Therapist Response Modes in Brief Psychotherapy.

    ERIC Educational Resources Information Center

    Hill, Clara E.; And Others

    1988-01-01

    Examined therapist response modes in 127 sessions of eight cases of brief psychotherapy with experienced therapists and anxious-depressed clients. Response modes had significant effect on immediate outcome, with self-disclosure, interpretation, approval, and paraphrase being the most helpful response modes. Found large individual differences in…

  4. Optical phonon modes of III-V nanoparticles and indium phosphide/II-VI core-shell nanoparticles: A Raman and infrared study

    NASA Astrophysics Data System (ADS)

    Manciu, Felicia Speranta

    The prospects for realizing efficient nanoparticle light emitters in the visible/near IR for communications and bio-medical applications have benefited from progress in chemical fabrication of nanoparticles. III-V semiconductor nanopaticles such as GaP and InP are promising materials for the development of "blue" and "green" emitters, respectively, due to their large effective bandgaps. Enhanced emission efficiency has been achieved for core-shell nanoparticles, since inorganic shell materials increase electronic tunability and may decrease surface defects that often occur for nanoparticles capped with organic molecules. Also, the emission wavelength of InP nanoparticle cores can be tuned from green to red by changing the shell material in InP/II-VI core-shell nanoparticles. Investigations of phonon modes in nanocrystals are of both fundamental and applied interest. In the former case the optical phonon modes, such as surface/interface modes, are dependent on the nanoparticle dimensions, and also can provide information about dynamical properties of the nanoparticles and test the validity of various theoretical approaches. In the latter case the vibronic properties of nanoparticle emitters are controlled by confined phonons and modifications of the electron-phonon interaction by the confinement. Thus, the objective of the present thesis is the detailed study of the phonon modes of III-V nanoparticles (GaP and InP) and InP/II-VI core-shell nanoparticles by IR absorption and Raman scattering spectroscopies, and an elucidation of their complex vibrational properties. With the exception of three samples (two GaP and one InP), all samples were synthesized by a novel colloidal chemistry method, which does not requires added surfactant, but rather treatment of the corresponding precursors in octadecene noncoordinative solvent. Sample quality was characterized by ED, TEM and X-ray diffraction. Based on a comparison with a dielectric continuum model, the observed features

  5. Different functional modes of p300 in activation of RNA polymerase III transcription from chromatin templates.

    PubMed

    Mertens, Claudia; Roeder, Robert G

    2008-09-01

    Transcriptional coactivators that regulate the activity of human RNA polymerase III (Pol III) in the context of chromatin have not been reported. Here, we describe a completely defined in vitro system for transcription of a human tRNA gene assembled into a chromatin template. Transcriptional activation and histone acetylation in this system depend on recruitment of p300 by general initiation factor TFIIIC, thus providing a new paradigm for recruitment of histone-modifying coactivators. Beyond its role as a chromatin-modifying factor, p300 displays an acetyltransferase-independent function at the level of preinitiation complex assembly. Thus, direct interaction of p300 with TFIIIC stabilizes binding of TFIIIC to core promoter elements and results in enhanced transcriptional activity on histone-free templates. Additional studies show that p300 is recruited to the promoters of actively transcribed tRNA and U6 snRNA genes in vivo. These studies identify TFIIIC as a recruitment factor for p300 and thus may have important implications for the emerging concept that tRNA genes or TFIIIC binding sites act as chromatin barriers to prohibit spreading of silenced heterochromatin domains. PMID:18644873

  6. Different Functional Modes of p300 in Activation of RNA Polymerase III Transcription from Chromatin Templates▿

    PubMed Central

    Mertens, Claudia; Roeder, Robert G.

    2008-01-01

    Transcriptional coactivators that regulate the activity of human RNA polymerase III (Pol III) in the context of chromatin have not been reported. Here, we describe a completely defined in vitro system for transcription of a human tRNA gene assembled into a chromatin template. Transcriptional activation and histone acetylation in this system depend on recruitment of p300 by general initiation factor TFIIIC, thus providing a new paradigm for recruitment of histone-modifying coactivators. Beyond its role as a chromatin-modifying factor, p300 displays an acetyltransferase-independent function at the level of preinitiation complex assembly. Thus, direct interaction of p300 with TFIIIC stabilizes binding of TFIIIC to core promoter elements and results in enhanced transcriptional activity on histone-free templates. Additional studies show that p300 is recruited to the promoters of actively transcribed tRNA and U6 snRNA genes in vivo. These studies identify TFIIIC as a recruitment factor for p300 and thus may have important implications for the emerging concept that tRNA genes or TFIIIC binding sites act as chromatin barriers to prohibit spreading of silenced heterochromatin domains. PMID:18644873

  7. Alpha particle effects on the internal kink modes

    SciTech Connect

    Wu, Yanlin; Cheng, C.Z.

    1994-08-01

    The {alpha}-particle effects on the internal kink mode stability are studied. Finite Grad-Shafranov Shift, plasma {beta}, and plasma shape can significantly enhance the trapped particle drift reversal domain in pitch angle space and reduce average magnetic drift frequency. The drift reversal effect on the ideal kink mode is small, but the {beta}{sub {alpha}} threshold for the fishbone mode can be much lower than previously predicted. In addition, the ion diamagnetic drift has a stronger destabilizing effect.

  8. Effect of thickness and loading mode on the fracture properties of V 4Cr 4Ti at room temperature

    NASA Astrophysics Data System (ADS)

    Li, H.; Kurtz, R. J.; Jones, R. H.

    1998-10-01

    The effect of thickness on the room temperature (RT) mode I fracture behavior of V-4Cr-4Ti has been investigated. Mode I fracture properties were measured from J-integral tests of compact tension (CT) specimens ranging in thickness from 6.4 to 25.4 mm. All specimens were machined in the T-L orientation and vacuum annealed following final machining. Two heats of V-4Cr-4Ti were tested. Specimens 6.4 and 12.7 mm thick were taken from Wah Chang Heat No. 832665. The 25.4 mm thick specimens were obtained from Wah Chang Heat No. 832864. The effect of loading mode on fracture of V-4Cr-4Ti at RT was also studied using material from Heat No. 832665. Mode I fracture behavior was compared to mixed-mode (I/III) fracture properties obtained from modified CT specimens. Crack angles of 0° and 25° were used to vary the ratio of mode III to mode I loading. J- R curves were generated as the basis for determining the affect of loading mode. The specimen loaded in mixed-mode exhibited lower resistance to crack initiation and propagation than pure mode I specimens.

  9. Transfer-printing-based integration of single-mode waveguide-coupled III-V-on-silicon broadband light emitters.

    PubMed

    De Groote, Andreas; Cardile, Paolo; Subramanian, Ananth Z; Fecioru, Alin M; Bower, Christopher; Delbeke, Danae; Baets, Roel; Roelkens, Günther

    2016-06-27

    We present the first III-V opto-electronic components transfer printed on and coupled to a silicon photonic integrated circuit. Thin InP-based membranes are transferred to an SOI waveguide circuit, after which a single-spatial-mode broadband light source is fabricated. The process flow to create transfer print-ready coupons is discussed. Aqueous FeCl3 at 5°C was found to be the best release agent in combination with the photoresist anchoring structures that were used. A thin DVS-BCB layer provides a strong bond, accommodating the post-processing of the membranes. The resulting optically pumped LED has a 3 dB bandwidth of 130 nm, comparable to devices realized using a traditional die-to-wafer bonding method. PMID:27410539

  10. Characteristics of Low-Frequency Molecular Phonon Modes Studied by THz Spectroscopy and Solid-State ab Initio Theory: Polymorphs I and III of Diflunisal.

    PubMed

    Zhang, Feng; Wang, Houng-Wei; Tominaga, Keisuke; Hayashi, Michitoshi

    2016-03-01

    THz absorption spectra of two polymorphs of diflunisal, form I and form III, exhibit distinct features due to the influence of packing conformations on the frequency distributions and IR activities of gamma point phonon modes within the 100 cm(-1) region. In order to understand the origins of these THz modes, we perform a detailed mode analysis. The result shows that although the spectral features are different, these low-frequency phonon modes of the two molecular polymorphs have similar vibrational characteristics in terms of harmonic couplings of intermolecular and intramolecular vibrations. PMID:26808927

  11. The mode III crack problem in bonded materials with a nonhomogeneous interfacial zone

    NASA Technical Reports Server (NTRS)

    Erdogan, F.; Joseph, P. F.; Kaya, A. C.

    1991-01-01

    The mode 3 crack problem for two bonded homogeneous half planes was considered. The interfacial zone was modelled by a nonhomogeneous strip in such a way that the shear modulus is a continuous function throughout the composite medium and has discontinuous derivatives along the boundaries of the interfacial zone. The problem was formulated for cracks perpendicular to the nominal interface and was solved for various crack locations in and around the interfacial region. The asymptotic stress field near the tip of a crack terminating at an interface was examined and it was shown that, unlike the corresponding stress field in piecewise homogeneous materials, in this case the stresses have the standard square root singularity and their angular variation was identical to that of a crack in a homogeneous medium. With application to the subcritical crack growth process in mind, the results given include mostly the stress intensity factors for some typical crack geometries and various material combinations.

  12. Analysis of the Effects of Three Modes of Head Start Delivery. Head Start Delivery Modes Project: Final Report.

    ERIC Educational Resources Information Center

    Peters, Donald L.; And Others

    This study analyzed the critical features of three delivery modes for Head Start services in order to: (1) compare the effects of different delivery modes on the immediate outcomes for children and parents; and (2) explore the pattern of effects both within and across modes to ascertain how the process works. The first mode represented the most…

  13. Plasmon modes of metallic nanowires including quantum nonlocal effects

    SciTech Connect

    Moradi, Afshin

    2015-03-15

    The properties of electrostatic surface and bulk plasmon modes of cylindrical metallic nanowires are investigated, using the quantum hydrodynamic theory of plasmon excitation which allows an analytical study of quantum tunneling effects through the Bohm potential term. New dispersion relations are obtained for each type of mode and their differences with previous treatments based on the standard hydrodynamic model are analyzed in detail. Numerical results show by considering the quantum effects, as the value of wave number increases, the surface modes are slightly red-shifted first and then blue-shifted while the bulk modes are blue-shifted.

  14. Mod 1 wind turbine generator failure modes and effects analysis

    NASA Technical Reports Server (NTRS)

    1979-01-01

    A failure modes and effects analysis (FMEA) was directed primarily at identifying those critical failure modes that would be hazardous to life or would result in major damage to the system. Each subsystem was approached from the top down, and broken down to successive lower levels where it appeared that the criticality of the failure mode warranted more detail analysis. The results were reviewed by specialists from outside the Mod 1 program, and corrective action taken wherever recommended.

  15. a Mossbauer Effect Study of Iron(iii) Dithiocarbamates.

    NASA Astrophysics Data System (ADS)

    Fiddy, Judith Mary

    Available from UMI in association with The British Library. Ever since the pioneering work of Cambi iron(III) trisdithiocarbamates, which have the formula Fe(R _2NCS_2]_3 where R is an alkyl or an aryl group, have formed the basis for understanding spin-state equilibria in iron(III) complexes. Magnetic and infrared studies clearly indicate equilibrium between the high-spin and low-spin states. The Mossbauer spectra, however, show only a single component, indicating rapid relaxation between the two spin states on the Mossbauer timescale. It has been assumed that the spectral parameters are therefore a function of the relative spin-state populations. In this thesis, the results of Mossbauer experiments carried out on a series of iron(III) trisdithiocarbamates with various organic substituents, known to give a range of high-spin and low-spin state populations at room temperature, are presented. An iron(III) bisdithiocarbamate complex, Fe^{57} ((C_5 H_{10})_2NCS _2]_2NCS, was also investigated. The samples were studied at temperatures from 1.3K to 295K, and at pressures between atmospheric pressure and 80kbar at room temperature only. It was found that, in fact, the spin-equilibrium plays only a minor role in determining the Mossbauer spectra of the trisdithiocarbamate compounds. The effects of spin -state relaxation on the temperature dependence of the spectra are, in general, masked by those of slow paramagnetic relaxation which, in contrast to the effects of the spin-equilibrium, are marked and different for each compound. By fitting the spectra to models of paramagnetic relaxation the temperature dependence of the relaxation rates and possible directions of the magnetic hyperfine field relative to the major axis of the electric field gradient were found. The pressure dependence of the spectra was found to be rather similar for all the compounds, the main differences being in the widths and in the asymmetry of the areas of the spectral lines. Both these effects can

  16. Period-Luminosity Relations Derived from the OGLE-III Fundamental Mode Cepheids. II. The Small Magellanic Cloud Cepheids

    NASA Astrophysics Data System (ADS)

    Ngeow, Chow-Choong; Kanbur, Shashi M.; Bhardwaj, Anupam; Singh, Harinder P.

    2015-07-01

    In this paper we present multi-band period-luminosity (P-L) relations for fundamental mode Cepheids in the SMC. The optical VI-band mean magnitudes for these SMC Cepheids were taken from the third phase of the Optical Gravitational Lensing Experiment (OGLE-III) catalog. We also matched the OGLE-III SMC Cepheids to 2MASS and SAGE-SMC catalog to derive mean magnitudes in the JHK-bands and the four Spitzer IRAC bands, respectively. All photometry was corrected for extinction by adopting Zaritsky’s extinction map. Cepheids with periods smaller than ˜2.5 days were removed from the sample. In addition to the extinction corrected P-L relations in nine filters from optical to infrared, we also derived the extinction-free Wesenheit function for these Cepheids. We tested the nonlinearity of these SMC P-L relations (except the 8.0 μ {{m}}-band P-L relation) at 10 days: none of the P-L relations show statistically significant evidence of nonlinearity. When compared to the P-L relations in the LMC, the t-test results revealed that there is a difference between the SMC/LMC P-L slopes only in the V- and J-band. Further, we found excellent agreement between the SMC/LMC Wesenheit P-L slope. The difference in LMC and SMC Period-Wesenheit relation LMC and SMC zero points was found to be {{Δ }}μ =0.483+/- 0.015 mag. This amounts to a difference in distance modulus between the LMC and SMC.

  17. Technology-Enhanced Courses and a Mode III Organization of Instructional Work

    ERIC Educational Resources Information Center

    Rhoades, Gary

    2007-01-01

    Although information technology is increasingly used to deliver distance and conventional courses, there have been few studies of the effect of technology-enhanced education on the organization and purposes of academics' instructional work. I explore this issue in undergraduate and masters level education through the vehicle of case analyses of…

  18. The Effects of Different Delivery Modes in Survey Administration

    ERIC Educational Resources Information Center

    Goho, James

    2003-01-01

    A perennial problem for survey research is achieving adequate response rates. One method for improving rates is to offer multiple modes for response. An associated issue is the effect of differing modes. This research examined both matters using a survey of community college graduates. Fielding consisted of two phases. Phase One offered three…

  19. Letter report seismic shutdown system failure mode and effect analysis

    SciTech Connect

    KECK, R.D.

    1999-09-01

    The Supply Ventilation System Seismic Shutdown ensures that the 234-52 building supply fans, the dry air process fans and vertical development calciner are shutdown following a seismic event. This evaluates the failure modes and determines the effects of the failure modes.

  20. Adamantyl-group containing mixed-mode acrylamide-based continuous beds for capillary electrochromatography. Part III. Optimization of the chromatographic efficiency.

    PubMed

    Al-Massaedh, Ayat Allah; Pyell, Ute

    2014-01-17

    In a previous article we described the synthesis of amphiphilic monolithic stationary phases by in situ free radical copolymerization of cyclodextrin-solubilized N-adamantyl acrylamide, piperazinediacrylamide, methacrylamide and vinylsulfonic acid in aqueous medium in pre-treated fused silica capillaries of 100μ.m I.D. In this work, a series of N-adamantyl-group containing acrylamide-based continuous beds is synthesized under variation of different synthesis parameters. The studied synthesis parameters are (i) concentration of the lyotropic salt ammonium sulfate, (ii) concentration of the initiator ammonium persulfate, and (iii) concentration of the negatively charged monomer vinylsulfonic acid in the polymerization mixture. The influence of the synthesis parameters on the chromatographic efficiency is studied under isocratic conditions for a homologues series of alkylphenones in the reversed-phase mode at constant composition of the mobile phase via capillary electrochromatography with varied electric field strength. With varied concentration of the lyotropic salt ammonium sulfate or varied concentration of the initiator ammonium persulfate in the polymerization mixture, a strong impact on the chromatographic efficiency is observed, while there is only a minor influence when varying the molar fraction of the charged monomer VSA. The absence of a significant influence of extra-column band broadening effects on the determined efficiency is confirmed. There is a good repeatability (with respect to capillary-to-capillary variation and run-to-run variation) reached for the theoretical plate heights obtained for DMF and selected alkylphenones in the reversed-phase mode. PMID:24296296

  1. Effective As(III) Removal by A Multi-Charged Hydroacid Complex Draw Solute Facilitated Forward Osmosis-Membrane Distillation (FO-MD) Processes.

    PubMed

    Ge, Qingchun; Han, Gang; Chung, Tai-Shung

    2016-03-01

    Effective removal of As(III) from water by an oxalic acid complex with the formula of Na3[Cr(C2O4)3] (Na-Cr-OA) is demonstrated via an forward osmosis-membrane distillation (FO-MD) hybrid system in this study. Na-Cr-OA first proved its superiority as a draw solute with high water fluxes and negligible reverse fluxes in FO, then a systematic investigation of the Na-Cr-OA promoted FO process was conducted to ascertain the factors in As(III) removal. Relatively high water fluxes of 28 LMH under the FO mode and 74 LMH under the pressure retarded osmosis (PRO) mode were achieved when using a 1000 ppm As(III) solution as the feed and 1.0 M Na-Cr-OA as the draw solution at 60 °C. As(III) removal with a water recovery up to 21.6% (FO mode) and 48.3% (PRO mode) were also achieved in 2 h. An outstanding As(III) rejection with 30-3000 μg/L As(III) in the permeate was accomplished when As(III) feed solutions varied from 5 × 10(4) to 1 × 10(6) μg/L, superior to the best FO performance reported for As(III) removal. Incorporating MD into FO not only makes As(III) removal sustainable by reconcentrating the Na-Cr-OA solution simultaneously, but also reduces the As(III) concentration below 10 μg/L in the product water, meeting the WHO standard. PMID:26822310

  2. Pulse-mode quantum projection synthesis: Effects of mode mismatch on optical state truncation and preparation

    SciTech Connect

    Oezdemir, Sahin Kaya; Koashi, Masato; Miranowicz, Adam; Imoto, Nobuyuki

    2002-11-01

    Quantum projection synthesis can be used for phase-probability-distribution measurement and optical-state truncation and preparation. The method relies on interfering optical light beams, which is a major challenge in experiments performed by pulsed light sources. In the pulsed regime, the time frequency overlap of the interfering light beams has a major impact on the efficiency of the method. In this paper, the pulse-mode projection-synthesis approach is developed, the mode structures of interfering light beams are characterized, and the effect of this overlap on the fidelity of optical-state truncation and preparation is investigated. By introducing the positive-operator-valued measure for the detection events in the scheme, the effect of mode mismatch between the photon-counting detectors and the incident light beams is also presented.

  3. III-V nanowire growth mechanism: V/III ratio and temperature effects.

    PubMed

    Dayeh, Shadi A; Yu, Edward T; Wang, Deli

    2007-08-01

    We have studied the dependence of Au-assisted InAs nanowire (NW) growth on InAs(111)B substrates as a function of substrate temperature and input V/III precursor ratio using organometallic vapor-phase epitaxy. Temperature-dependent growth was observed within certain temperature windows that are highly dependent on input V/III ratios. This dependence was found to be a direct consequence of the drop in NW nucleation and growth rate with increasing V/III ratio at a constant growth temperature due to depletion of indium at the NW growth sites. The growth rate was found to be determined by the local V/III ratio, which is dependent on the input precursor flow rates, growth temperature, and substrate decomposition. These studies advance understanding of the key processes involved in III-V NW growth, support the general validity of the vapor-liquid-solid growth mechanism for III-V NWs, and improve rational control over their growth morphology. PMID:17608541

  4. Geometric Effects on the Amplification of First Mode Instability Waves

    NASA Technical Reports Server (NTRS)

    Kirk, Lindsay C.; Candler, Graham V.

    2013-01-01

    The effects of geometric changes on the amplification of first mode instability waves in an external supersonic boundary layer were investigated using numerical techniques. Boundary layer stability was analyzed at Mach 6 conditions similar to freestream conditions obtained in quiet ground test facilities so that results obtained in this study may be applied to future test article design to measure first mode instability waves. The DAKOTA optimization software package was used to optimize an axisymmetric geometry to maximize the amplification of the waves at first mode frequencies as computed by the 2D STABL hypersonic boundary layer stability analysis tool. First, geometric parameters such as nose radius, cone half angle, vehicle length, and surface curvature were examined separately to determine the individual effects on the first mode amplification. Finally, all geometric parameters were allowed to vary to produce a shape optimized to maximize the amplification of first mode instability waves while minimizing the amplification of second mode instability waves. Since first mode waves are known to be most unstable in the form of oblique wave, the geometries were optimized using a broad range of wave frequencies as well as a wide range of oblique wave angles to determine the geometry that most amplifies the first mode waves. Since first mode waves are seen most often in flows with low Mach numbers at the edge of the boundary layer, the edge Mach number for each geometry was recorded to determine any relationship between edge Mach number and the stability of first mode waves. Results indicate that an axisymmetric cone with a sharp nose and a slight flare at the aft end under the Mach 6 freestream conditions used here will lower the Mach number at the edge of the boundary layer to less than 4, and the corresponding stability analysis showed maximum first mode N factors of 3.

  5. Failure Modes and Effects Analysis (FMEA) Assistant Tool Feasibility Study

    NASA Technical Reports Server (NTRS)

    Flores, Melissa; Malin, Jane T.

    2013-01-01

    An effort to determine the feasibility of a software tool to assist in Failure Modes and Effects Analysis (FMEA) has been completed. This new and unique approach to FMEA uses model based systems engineering concepts to recommend failure modes, causes, and effects to the user after they have made several selections from pick lists about a component s functions and inputs/outputs. Recommendations are made based on a library using common failure modes identified over the course of several major human spaceflight programs. However, the tool could be adapted for use in a wide range of applications from NASA to the energy industry.

  6. Kinetic effect of toroidal rotation on the geodesic acoustic mode

    SciTech Connect

    Guo, W. Ye, L.; Zhou, D.; Xiao, X.; Wang, S.

    2015-01-15

    Kinetic effects of the toroidal rotation on the geodesic acoustic mode are theoretically investigated. It is found that when the toroidal rotation increases, the damping rate increases in the weak rotation regime due to the rotation enhancement of wave-particle interaction, and it decreases in the strong rotation regime due to the reduction of the number of resonant particles. Theoretical results are consistent with the behaviors of the geodesic acoustic mode recently observed in DIII-D and ASDEX-Upgrade. The kinetic damping effect of the rotation on the geodesic acoustic mode may shed light on the regulation of turbulence through the controlling the toroidal rotation.

  7. Effective field theory from modified gravity with massive modes

    NASA Astrophysics Data System (ADS)

    Capozziello, Salvatore; de Laurentis, Mariafelicia; Paolella, Mariacristina; Ricciardi, Giulia

    2015-10-01

    Massive gravitational modes in effective field theories can be recovered by extending General Relativity and taking into account generic functions of the curvature invariants, not necessarily linear in the Ricci scalar R. In particular, adopting the minimal extension of f(R) gravity, an effective field theory with massive modes is straightforwardly recovered. This approach allows to evade shortcomings like ghosts and discontinuities if a suitable choice of expansion parameters is performed.

  8. Effective transition probability for the Faraday effect of lanthanide(III) ion solutions.

    PubMed

    Miyamoto, Kayoko; Isai, Kento; Suwa, Masayori; Watarai, Hitoshi

    2009-05-13

    The Faraday effects of 14 lanthanide(III) ion solutions were systematically analyzed on the basis of the Faraday C term. The effective transition probability, K, which measures the magneto-optical contribution of the 4f(n) --> 4f(n-1)5d transition to the molar Verdet constant, was determined. Linear correlations between K and the square root of the molar magnetic susceptibility of the lanthanide(III) ions, chi(m)(1/2), were obtained. From the observed new regularity, K for promethium(III) was estimated. PMID:19378955

  9. Complexation of Nd(III) with tetraborate ion and its effect on actinide (III) solubility in WIPP brine

    SciTech Connect

    Borkowski, Marian; Richmann, Michael K; Reed, Donald T; Yongliang, Xiong

    2010-01-01

    The potential importance of tetraborate complexation on lanthanide(III) and actinide(III) solubility is recognized in the literature but a systematic study of f-element complexation has not been performed. In neodymium solubility studies in WIPP brines, the carbonate complexation effect is not observed since tetraborate ions form a moderately strong complex with neodymium(III). The existence of these tetraborate complexes was established for low and high ionic strength solutions. Changes in neodymium(III) concentrations in undersaturation experiments were used to determine the neodymium with tetraborate stability constants as a function of NaCl ionic strength. As very low Nd(III) concentrations have to be measured, it was necessary to use an extraction pre-concentration step combined with ICP-MS analysis to extend the detection limit by a factor of 50. The determined Nd(III) with borate stability constants at infinite dilution and 25 C are equal to log {beta}{sub 1} = 4.55 {+-} 0.06 using the SIT approach, equal to log {beta}{sub 1} = 4.99 {+-} 0.30 using the Pitzer approach, with an apparent log {beta}{sub 1} = 4.06 {+-} 0.15 (in molal units) at I = 5.6 m NaCl. Pitzer ion-interaction parameters for neodymium with tetraborate and SIT interaction coefficients were also determined and reported.

  10. Heterogeneously integrated III-V/Si single mode lasers based on a MMI-ring configuration and triplet-ring reflectors

    NASA Astrophysics Data System (ADS)

    Keyvaninia, S.; Verstuyft, S.; Lelarge, F.; Duan, G.-H.; Messaoudene, S.; Fédéli, J. M.; Geluk, E. J.; De Vries, T.; Smalbrugge, B.; Bolk, J.; Smit, M.; Van Thourhout, D.; Roelkens, G.

    2013-05-01

    In this paper we show that using a DVS-BCB adhesive bonding process compact heterogeneously integrated III-V/silicon single mode lasers can be realized. Two new designs were implemented: in a first design a multimode interferometer coupler (MMI) - ring resonator combination is used to provide a comb-like reflection spectrum, while in a second design a triplet-ring reflector design is used to obtain the same. A broadband silicon Bragg grating reflector is implemented on the other side of the cavity. The III-V optical amplifier is heterogeneously integrated on the 400nm thick silicon waveguide layer, which is compatible with high-performance modulator designs and allows for efficient coupling to a standard 220nm high index contrast silicon waveguide layer. In order to make the optical coupling efficient, both the III-V waveguide and the silicon waveguide are tapered, with a tip width of the III-V waveguide of around 500nm. The III-V thin film optical amplifier is implemented as a 3μm wide mesa etched through to the n-type InP contact layer. In this particular device implementation the amplifier section was 500μm long. mW-level waveguide coupled output power at 20°C and a side mode suppression ratio of more than 40dB is obtained.

  11. Arc fusion splicing effects in large-mode-area single-mode ytterbium-doped fibers.

    PubMed

    Feng, Ting; Jenkins, Micah H; Yan, Fengping; Gaylord, Thomas K

    2013-11-10

    For the first time the effects of arc fusion splicing on the residual stress and refractive index of large-mode-area single-mode ytterbium-doped fibers (YDFs) are investigated using a state-of-the-art three-dimensional concurrent stress-index measurement method. The results, based on a commercially available fiber, describe a host of perturbations that decrease the core/cladding refractive index difference by as much as 1.74 × 10(-3) over an axial length of many hundreds of wavelengths. Simulations indicate that these perturbations result in an expansion of the mode-field-diameter by 39.6% and, based on the measured sample, result in an extra splice loss of 20.8%. The results of this investigation will be useful in the design and optimization of high-power all-fiber YDF lasers and amplifiers. PMID:24216728

  12. Interactions of bis(2,4,4-trimethylpentyl)dithiophosphinate with Nd(III) and Cm(III) in a homogeneous medium: a comparative study of thermodynamics and coordination modes.

    PubMed

    Xu, Chao; Rao, Linfeng

    2014-11-01

    Complexation of Nd(III) and Cm(III) with purified Cyanex301 (ammonium bis(2,4,4-trimethylpentyl)dithiophosphinate, denoted as HL) was studied in 1 % v/v water/ethanol under identical conditions by spectrophotometry and microcalorimetry. For Nd(III) , three successive complexes, NdL(2+) , NdL2 (+) , and NdL3 , formed in the solution. In contrast, four complexes, CmL(2+) , CmL2 (+) , CmL3 , and CmL4 (-) formed during the titration with Cm. Fluorescence lifetime measurements provided additional insight into the complexation of Cm(III) with Cyanex301. The stepwise stability constants for the CmLj ((3-j)+) (j=1-3) complexes are about one order of magnitude higher than the corresponding NdLj ((3-j)+) complexes. The enthalpies of complexation are endothermic for both Nd(III) and Cm(III) , suggesting that the energy required for desolvation exceeds the energy gained from the cation/ligand combination. Specifically, the enthalpy of complexation for CmL(2+) is 3.5 kJ mol(-1) less endothermic than that of NdL(2+) , implying stronger covalent interaction in CmL(2+) than NdL(2+) . However, the enthalpies of complexation for CmL2 (+) and NdL2 (+) are nearly identical, and the enthalpy of complexation for CmL3 (aq) becomes more endothermic than that for NdL3 (aq). The observations suggest that, in the ethanol/water media, the overall energetics of the Cm(III) /Nd(III) complexation with Cyanex301 could depend on a number of factors, including the extent of covalency, the degree of desolvation, and the coordination modes. PMID:25213623

  13. Neoclassical viscosity effects on resistive magnetohydrodynamic modes in toroidal geometry

    SciTech Connect

    Yang, J.G.; Oh, Y.H.; Choi, D.I. ); Kim, J.Y.; Horton, W. )

    1992-03-01

    The flux-surface-averaged linearized resistive magnetohydrodynamic (MHD) boundary-layer equations including the compressibility, diamagnetic drift, and neoclassical viscosity terms are derived in toroidal geometry. These equations describe the resistive layer dynamics of resistive MHD modes over the collisionality regime between the banana plateau and the Pfirsch--Schlueter. From the resulting equations, the effects of neoclassical viscosity on the stability of the tearing and resistive ballooning modes are investigated numerically. Also, a study is given for the problem of how the neoclassical resistive MHD mode is generated as the collisionality is reduced. It is shown that the neoclassical viscosity terms give a significant destabilizing effect for the tearing and resistive ballooning modes. This destabilization comes mainly from the reduction of the stabilizing effect of the parallel ion sound compression by the ion neoclassical viscosity. In the banana-plateau collisionality limit, where the compressibility is negligible, the dispersion relations of the tearing and resistive ballooning modes reduce to the same form, with the threshold value of the driving force given by {Delta}{sub {ital c}}=0. On the other hand, with the finite neoclassical effect it is found that the neoclassical resistive MHD instability is generated in agreement with previous results. Furthermore, it is shown that this later instability can be generated in a wide range of the collisionality including near the Pfirsch--Schlueter regime as well as the banana-plateau regime, suggesting that this mode is a probable cause of anomalous transport.

  14. Aggregated enhanced Raman scattering in Fe(III)PPIX solutions: the effects of concentration and chloroquine on excitonic interactions.

    PubMed

    Webster, Grant T; McNaughton, Don; Wood, Bayden R

    2009-05-14

    Resonance Raman spectra of hematin and hemin solutions are reported for 413 and 514 nm excitation wavelengths. Enhancement of A1g modes (1569 and 1370 cm(-1)) and B1g modes (1124 and 755 cm(-1)) as a function of increased concentration are observed when irradiating with 514 nm laser excitation but not 413 nm. This can be rationalized by considering an excitonic coupling mechanism. As the concentration of hematin increases there is an increased probability of supramolecular interactions between iron(III) protoporphyrin IX (Fe(III)PPIX) units occurring. The Fe(III)PPIX concentration reaches a saturation point in solution and excitonic coupling reaches a maximum causing the enhancement profile to plateau when applying 514 nm excitation. In contrast, when using 413 nm excitation there were no changes in band intensity with increased concentration showing that excitonic coupling through supramolecular interactions for aggregated solutions is wavelength dependent. Electronic absorption spectra show that as the concentration of Fe(III)PPIX increases in solution the Soret band is slightly blue shifted and the Q-band significantly broadens supporting the excitonic hypothesis. Understanding the mechanism that accounts for the Raman photophysical behavior of hemes at high concentrations provided an indirect method to monitor antimalarial drug interactions. A second aim was to investigate chloroquine binding to Fe(III)PPIX-OH/H2O monomers, pi-pi dimers and micro-oxo dimers formed in highly concentrated solutions approaching those of the digestive vacuole of the P. falciparum malaria parasite using excitonic Raman enhancement. It was hypothesized that the Raman excitonic enhancement mechanism could be impeded in heme aggregated solutions by the addition of chloroquine. This would result in a reduction in heme bands associated with the A1g modes including nu4. Resonance Raman spectra recorded using 514 nm excitation show that chloroquine (CQ) acts as a molecular spacer and binds

  15. Survey mode effects on valuation of environmental goods.

    PubMed

    Bell, Jason; Huber, Joel; Viscusi, W Kip

    2011-04-01

    This article evaluates the effect of the choice of survey recruitment mode on the value of water quality in lakes, rivers, and streams. Four different modes are compared: bringing respondents to one central location after phone recruitment, mall intercepts in two states, national phone-mail survey, and an Internet survey with a national, probability-based panel. The modes differ in terms of the representativeness of the samples, non-response rates, sample selection effects, and consistency of responses. The article also shows that the estimated value of water quality can differ substantially depending on the survey mode. The national Internet panel has the most desirable properties with respect to performance on the four important survey dimensions of interest. PMID:21695037

  16. Plasma Oscillations and Operational Modes in Hall Effect Thrusters

    NASA Astrophysics Data System (ADS)

    Sekerak, Michael J.

    Mode transitions have been commonly observed in Hall effect thruster (HET) operation where a small change in a thruster operating parameter such as discharge voltage, magnetic field or mass flow rate causes the thruster discharge current mean value and oscillation amplitude to increase significantly. In this study, mode transitions in HETs are induced by varying the magnetic field intensity while holding all other operating parameters constant and measurements are acquired with high-speed probes and ultra-fast imaging. Two primary oscillatory modes were identified and extensively characterized called global oscillation mode and local oscillation mode. In the global mode, the entire discharge channel oscillates in unison and azimuthal perturbations (spokes) are either absent or negligible. Downstream azimuthally spaced probes show no signal delay between each other and are very well correlated to the discharge current signal. In the local mode, signals from the azimuthally spaced probes exhibit a clear delay indicating the passage of spokes. These spokes are localized oscillations in discharge current density propagating in the E x B direction that are typically 10-20% of the mean value. In contrast, the oscillations in the global mode can be 100% of the mean discharge current density value. The spoke velocity is determined from high-speed image analysis using three methods yielding values between 1500 and 2200 m/s across a range of magnetic field settings. The transition between global and local modes occurs at higher relative magnetic field strengths for higher mass flow rates or higher discharge voltages. It is proposed that mode transitions represent de-stabilization of the ionization front similar to excitation of the well-studied Hall thruster breathing mode, which is supported by time-resolved simulations of the discharge channel plasma. The thrust is approximately constant in both modes, but the thrust-to-power and anode efficiency decrease in global mode

  17. Effects of voids on delamination behavior under static and fatigue mode I and mode II

    NASA Astrophysics Data System (ADS)

    Abdelal, Nisrin Rizek

    Composite materials have become materials of choice for wind turbine blade manufacturing due to their high specific stiffness, strength and fatigue life. Glass fiber composites are used extensively in light-weight structural components for wind turbines, aircrafts, marine craft and high performance automobile because glass fiber is inexpensive and usually provides high strength to weight ratio and good in-plane mechanical properties. The high cycle fatigue resistance of composite materials used in wind turbine blades has been recognized as a major uncertainty in predicting the reliability of wind turbines over their design lifetime. Blades are expected to experience 108 to 109 fatigue cycles over a 20 to 30 year lifetime. Delamination or interlaminar failure is a serious failure mode observed in composite structures. Even partial delamination will lead to a loss of local stiffness, which can preclude buckling failure. Manufacturing process defects such as voids and fiber waviness degrade the fatigue life and delamination resistance of the blade's composite. This research describes the effect of voids on static and fatigue interlaminar fracture behavior under mode I and mode II loading of wind turbine glass fiber composites. Samples with different void volume fractions in the 0.5%-7% range were successfully obtained by varying the vacuum in the hand layup vacuum bagging manufacturing process. Void content was characterized using four different methods; ultrasonic scanning, epoxy burn off, serial sectioning and X-Ray computed tomography. The effect of voids on both mode I and mode II interlaminar fracture toughness under static and fatigue loading was investigated. Finally, fractographic analysis (using optical and scanning electron microscopy) was conducted. The results showed that voids leads to slight reduction in static modes I and II interlaminar fracture toughness. In addition, voids lead to a decrease in modes I and II maximum cyclic strain energy release

  18. Development of fracture facets from a crack loaded in mode I+III: Solution and application of a model 2D problem

    NASA Astrophysics Data System (ADS)

    Leblond, Jean-Baptiste; Frelat, Joël

    2014-03-01

    It is experimentally well-known that a crack loaded in mode I+III propagates through formation of discrete fracture facets inclined at a certain tilt angle on the original crack plane, depending on the ratio of the mode III to mode I initial stress intensity factors. Pollard et al. (1982) have proposed to calculate this angle by considering the tractions on all possible future infinitesimal facets and assuming shear tractions to be zero on that which will actually develop. In this paper we consider the opposite case of well-developed facets; the stress field near the lateral fronts of such facets becomes independent of the initial crack and essentially 2D in a plane perpendicular to the main direction of crack propagation. To determine this stress field, we solve the model 2D problem of an infinite plate containing an infinite periodic array of cracks inclined at some angle on a straight line, and loaded through uniform stresses at infinity. This is done first analytically, for small values of this angle, by combining Muskhelishvili's (1953) formalism and a first-order perturbation procedure. The formulae found for the 2D stress intensity factors are then extended in an approximate way to larger angles by using another reference solution, and finally assessed through comparison with some finite element results. To finally illustrate the possible future application of these formulae to the prediction of the stationary tilt angle, we introduce the tentative assumption that the 2D mode II stress intensity factor is zero on the lateral fronts of the facets. An approximate formula providing the tilt angle as a function of the ratio of the mode III to mode I stress intensity factors of the initial crack is deduced from there. This formula, which slightly depends on the type of loading imposed, predicts somewhat smaller angles than that of Pollard et al. (1982).

  19. Effects of Ca2+ on refolding of the recombinant hemolytic lectin CEL-III.

    PubMed

    Hisamatsu, Keigo; Unno, Hideaki; Goda, Shuichiro; Hatakeyama, Tomomitsu

    2009-05-01

    CEL-III is a hemolytic lectin isolated from Cucumaria echinata. Although recombinant CEL-III (rCEL-III) expressed in Escherichia coli showed very weak hemolytic activity compared with native protein, it was considerably enhanced by refolding in the presence of Ca(2+). This suggests that Ca(2+) supported correct folding of the carbohydrate-binding domains of rCEL-III, leading to effective binding to the cell surface and subsequent self-oligomerization. PMID:19420692

  20. Complex modes and effective refractive index in 3D periodic arrays of plasmonic nanospheres.

    PubMed

    Campione, Salvatore; Steshenko, Sergiy; Albani, Matteo; Capolino, Filippo

    2011-12-19

    We characterize the modes with complex wavenumber for both longitudinal and transverse polarization states (with respect to the mode traveling direction) in three dimensional (3D) periodic arrays of plasmonic nanospheres, including metal losses. The Ewald representation of the required dyadic periodic Green's function to represent the field in 3D periodic arrays is derived from the scalar case, which can be analytically continued into the complex wavenumber space. We observe the presence of one longitudinal mode and two transverse modes, one forward and one backward. Despite the presence of two modes for transverse polarization, we notice that the forward one is "dominant" (i.e., it contributes most to the field in the array). Therefore, in case of transverse polarization, we describe the composite material in terms of a homogenized effective refractive index, comparing results from (i) modal analysis, (ii) Maxwell Garnett theory, (iii) Nicolson-Ross-Weir retrieval method from scattering parameters for finite thickness structures (considering different thicknesses, showing consistency of results), and (iv) the fitting of the fields obtained through HFSS simulations. The agreement among the different methods justifies the performed homogenization procedure in case of transverse polarization. PMID:22274192

  1. Experimental and simulation predicted crack paths for al-2024-t351 under mixed-mode i/ii fatigue loading using an arcan fixture

    NASA Astrophysics Data System (ADS)

    Miller, Eileen

    Mixed mode I/II fatigue experiments and simulations are performed for an Arcan fixture and a 6.35mm thick Al-2024-T351 specimen. Experiments were performed for Arcan loading angles that gave rise to a range of Mode I/II crack tip conditions from 0 ¡U ¦¤KII/¦¤KI ¡U ¡TH. Measurements include the crack paths, loading cycles and maximum and minimum loads for each loading angle. Simulations were performed using three-dimensional finite element analysis (3D-FEA) with 10-noded tetrahedral elements via CRACK3D. While modeling the entire fixture-specimen geometry, a modified version of VCCT with automatic crack tip re-meshing and a maximum normal stress criterion were used to predict the direction of crack growth. Results indicate excellent agreement between experiments and simulations for the measured crack paths during the first several millimeters of crack extension.

  2. Possible confirmation of the existence of the ergoregion by the Kerr quasinormal mode in gravitational waves from a Population III massive black hole binary

    NASA Astrophysics Data System (ADS)

    Kinugawa, Tomoya; Nakano, Hiroyuki; Nakamura, Takashi

    2016-03-01

    The existence of the ergoregion of the Kerr space-time has not yet been confirmed observationally. We show that the confirmation would be possible by observing the quasinormal mode in gravitational waves. As an example, using the recent population synthesis results of Population III (Pop III) binary black holes, we find that the peak of the final merger mass (M_f) is about 50 M_{⊙}, while the fraction of the final spin q_f = a_f/M_f > 0.7 needed for the confirmation of a part of the ergoregion is {˜ }77%. To confirm the frequency of the quasinormal mode, SNR > 35 is needed. The standard model of Pop III population synthesis tells us that the event rate for the confirmation of more than 50% of the ergoregion by second generation gravitational wave detectors is {˜ }2.3 events yr^{-1 (SFR_p/(10^{-2.5} M_⊙ yr^{-1} Mpc^{-3}))} \\cdot ([f_b/(1+f_b)]/0.33), where SFR_p and f_b are the peak value of the Pop III star formation rate and the fraction of binaries, respectively.

  3. Effects of mode-mode and isospin-isospin correlations on domain formation of disoriented chiral condensates

    SciTech Connect

    Ikezi, N.; Asakawa, M.; Tsue, Y.

    2006-04-15

    The effects of mode-mode and isospin-isospin correlations on nonequilibrium chiral dynamics are investigated by using the method of the time-dependent variational approach with squeezed states as trial states. Our numerical simulations show that large domains of the disoriented chiral condensate (DCC) are formed because of the combined effect of the mode-mode and isospin-isospin correlations. Moreover, it is found that, when the mode-mode correlation is included, the DCC domain formation is accompanied by the amplification of the quantum fluctuation, which implies the squeezing of the state. However, neither the DCC domain formation nor the amplification of the quantum fluctuation is observed if only the isospin-isospin correlation is included. This suggests that the mode-mode coupling plays a key role in the DCC domain formation.

  4. Polarization Effects in Group III-Nitride Materials and Devices

    NASA Astrophysics Data System (ADS)

    Wei, Qiyuan

    Group III-nitride semiconductors have wide application in optoelectronic devices. Spontaneous and piezoelectric polarization effects have been found to be critical for electric and optical properties of group III-nitrides. In this dissertation, firstly, the crystal orientation dependence of the polarization is calculated and in-plane polarization is revealed. The in-plane polarization is sensitive to the lateral characteristic dimension determined by the microstructure. Specific semi-polar plane growth is suggested for reducing quantum-confined Stark effect. The macroscopic electrostatic field from the polarization discontinuity in the heterostructures is discussed, b ased on that, the band diagram of InGaN/GaN quantum well/barrier and AlGaN/GaN heterojunction is obtained from the self-consistent solution of Schrodinger and Poisson equations. New device design such as triangular quantum well with the quenched polarization field is proposed. Electron holography in the transmission electron microscopy is used to examine the electrostatic potential under polarization effects. The measured potential energy profiles of heterostructure are compared with the band simulation, and evidences of two-dimensional hole gas (2DHG) in a wurtzite AlGaN/ AlN/ GaN superlattice, as well as quasi two-dimensional electron gas (2DEG) in a zinc-blende AlGaN/GaN are found. The large polarization discontinuity of AlN/GaN is the main source of the 2DHG of wurtzite nitrides, while the impurity introduced during the growth of AlGaN layer provides the donor states that to a great extent balance the free electrons in zinc-blende nitrides. It is also found that the quasi-2DEG concentration in zinc-blende AlGaN/GaN is about one order of magnitude lower than the wurtzite AlGaN/GaN, due to the absence of polarization. Finally, the InAlN/GaN lattice-matched epitaxy, which ideally has a zero piezoelectric polarization and strong spontaneous polarization, is experimentally studied. The breakdown in

  5. Langmuir mixing effects on global climate: WAVEWATCH III in CESM

    NASA Astrophysics Data System (ADS)

    Li, Qing; Webb, Adrean; Fox-Kemper, Baylor; Craig, Anthony; Danabasoglu, Gokhan; Large, William G.; Vertenstein, Mariana

    2016-07-01

    Large-Eddy Simulations (LES) have shown the effects of ocean surface gravity waves in enhancing the ocean boundary layer mixing through Langmuir turbulence. Neglecting this Langmuir mixing process may contribute to the common shallow bias in mixed layer depth in regions of the Southern Ocean and the Northern Atlantic in most state-of-the-art climate models. In this study, a third generation wave model, WAVEWATCH III, has been incorporated as a component of the Community Earth System Model, version 1.2 (CESM1.2). In particular, the wave model is now coupled with the ocean model through a modified version of the K-Profile Parameterization (KPP) to approximate the influence of Langmuir mixing. Unlike past studies, the wind-wave misalignment and the effects of Stokes drift penetration depth are considered through empirical scalings based on the rate of mixing in LES. Wave-Ocean only experiments show substantial improvements in the shallow biases of mixed layer depth in the Southern Ocean. Ventilation is enhanced and low concentration biases of pCFC-11 are reduced in the Southern Hemisphere. A majority of the improvements persist in the presence of other climate feedbacks in the fully coupled experiments. In addition, warming of the subsurface water over the majority of global ocean is observed in the fully coupled experiments with waves, and the cold subsurface ocean temperature biases are reduced.

  6. The congruency sequence effect transfers across different response modes.

    PubMed

    Weissman, Daniel H; Colter, Katelyn; Drake, Brittany; Morgan, Christina

    2015-10-01

    The congruency effect observed in distracter interference tasks is usually smaller after incongruent relative to congruent trials. However, the nature of control processes underlying this congruency sequence effect (CSE) remains a topic of active debate. For example, while some researchers have suggested that these processes are recruited only when participants utilize the same response mode (e.g., the same hand) to respond in consecutive trials, others have argued that these processes can operate independently of response mode. To distinguish between these views, we investigated whether changes of response mode across consecutive trials influence the CSE in a prime-probe task (Experiment 1) or a flanker task (Experiment 2). Such changes did not influence the CSE in either task. Further, the CSE was significant even when participants utilized different response modes (i.e., different hands) to respond in consecutive trials. These findings indicate that control processes underlying the CSE can operate independently of response mode and thereby clarify the nature of control processes that minimize distraction from irrelevant stimuli. PMID:26343331

  7. Nonlinear simulations of particle source effects on edge localized mode

    SciTech Connect

    Huang, J.; Tang, C. J.; Chen, S. Y.; Wang, Z. H.

    2015-12-15

    The effects of particle source (PS) with different intensities and located positions on Edge Localized Mode (ELM) are systematically studied with BOUT++ code. The results show the ELM size strongly decreases with increasing the PS intensity once the PS is located in the middle or bottom of the pedestal. The effects of PS on ELM depend on the located position of PS. When it is located at the top of the pedestal, peeling-ballooning (P-B) modes can extract more free energy from the pressure gradient and grow up to be a large filament at the initial crash phase and the broadening of mode spectrum can be suppressed by PS, which leads to more energy loss. When it is located in the middle or bottom of the pedestal, the extraction of free energy by P-B modes can be suppressed, and a small filament is generated. During the turbulence transport phase, the broader mode spectrum suppresses the turbulence transport when PS is located in the middle, while the zonal flow plays an important role in damping the turbulence transport when PS is located at the bottom.

  8. Nonlinear simulations of particle source effects on edge localized mode

    NASA Astrophysics Data System (ADS)

    Huang, J.; Chen, S. Y.; Wang, Z. H.; Tang, C. J.

    2015-12-01

    The effects of particle source (PS) with different intensities and located positions on Edge Localized Mode (ELM) are systematically studied with BOUT++ code. The results show the ELM size strongly decreases with increasing the PS intensity once the PS is located in the middle or bottom of the pedestal. The effects of PS on ELM depend on the located position of PS. When it is located at the top of the pedestal, peeling-ballooning (P-B) modes can extract more free energy from the pressure gradient and grow up to be a large filament at the initial crash phase and the broadening of mode spectrum can be suppressed by PS, which leads to more energy loss. When it is located in the middle or bottom of the pedestal, the extraction of free energy by P-B modes can be suppressed, and a small filament is generated. During the turbulence transport phase, the broader mode spectrum suppresses the turbulence transport when PS is located in the middle, while the zonal flow plays an important role in damping the turbulence transport when PS is located at the bottom.

  9. Enhancing Effective Chemistry Learning through Hypermedia Instructional Mode of Delivery

    ERIC Educational Resources Information Center

    Abanikannda, Mutahir Oluwafemi

    2016-01-01

    This study provides a framework for the production of Hypermedia Instructional package. It also assessed the effectiveness of hypermedia instructional mode of delivery on students? performance in Chemistry. This is with a view of improving the learning of Chemistry which may eventually help to improve students? performance. The developmental study…

  10. Verification of gyrokinetic particle simulation of current-driven instability in fusion plasmas. III. Collisionless tearing mode

    NASA Astrophysics Data System (ADS)

    Liu, Dongjian; Bao, Jian; Han, Tao; Wang, Jiaqi; Lin, Zhihong

    2016-02-01

    A finite-mass electron fluid model for low frequency electromagnetic fluctuations, particularly the collisionless tearing mode, has been implemented in the gyrokinetic toroidal code. Using this fluid model, linear properties of the collisionless tearing mode have been verified. Simulations verify that the linear growth rate of the single collisionless tearing mode is proportional to De2, where De is the electron skin depth. On the other hand, the growth rate of a double tearing mode is proportional to De in the parameter regime of fusion plasmas.

  11. Radiation effects on III-V heterostructure devices

    NASA Astrophysics Data System (ADS)

    Jun, Bongim

    The neutron and electron radiation effects in III-V compound semiconductor heterostructure devices are studied in this thesis. Three types of devices investigated are AlGaAs/GaAs high electron mobility transistors (HEMTs), AlGaAs/InGaAs/GaAs heterostructure insulated gate field effect transistors (HIGFETs), and InP/InGaAs/InGaAs single heterojunction bipolar transistors (SHBTs). HEMTs and HIGFETs are primarily investigated for neutron irradiation effects. Detailed optimized processing of HEMT devices is introduced. Numerical as well as analytical models that incorporate radiation-induced degradation effects in HEMTs and HIGFETs are developed. The most prominent radiation effects appearing on both HEMT and HIGFET devices are increase of threshold voltage (VT) and decrease of transconductance (gm) as radiation dose increases. These effects are responsible for drain current degradation under given bias conditions after irradiation. From our experimental neutron irradiation study and our theoretical models, we concluded that threshold voltage increase is due to the radiation-induced acceptor-like (negatively charged) traps in the GaAs channel region removing carriers. The mobility degradation in the channel is responsible for gm decrease. Series resistance increase is also related to carrier removal and mobility degradation. Traps introduced in the GaAs region affect the device performance more than the traps in the AlGaAs doped region. V T and gm of HIGFET devices are less affected by neutron radiation than they are in HEMTs. This difference is attributed to different shapes of the quantum well in the two devices. The main effects of electron and neutron irradiation of SHBTs are decrease of collector current (IC), decrease of common-emitter DC gain, increase of the collector output conductance (DeltaI C/DeltaVCE), and increase of collector-collector offset voltage. The decrease of breakdown voltage of reverse biased base-emitter junction diode is responsible for

  12. Failure Modes and Effects Analysis (FMEA): A Bibliography

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Failure modes and effects analysis (FMEA) is a bottom-up analytical process that identifies process hazards, which helps managers understand vulnerabilities of systems, as well as assess and mitigate risk. It is one of several engineering tools and techniques available to program and project managers aimed at increasing the likelihood of safe and successful NASA programs and missions. This bibliography references 465 documents in the NASA STI Database that contain the major concepts, failure modes or failure analysis, in either the basic index of the major subject terms.

  13. Effect of Population III Multiplicity on Dark Star Formation

    NASA Technical Reports Server (NTRS)

    Stacy, Athena; Pawlik, Andreas H.; Bromm, Volker; Loeb, Abraham

    2012-01-01

    We numerically study the mutual interaction between dark matter (DM) and Population III (Pop III) stellar systems in order to explore the possibility of Pop III dark stars within this physical scenario. We perform a cosmological simulation, initialized at z approx. 100, which follows the evolution of gas and DM. We analyze the formation of the first mini halo at z approx. 20 and the subsequent collapse of the gas to densities of 10(exp 12)/cu cm. We then use this simulation to initialize a set of smaller-scale 'cut-out' simulations in which we further refine the DM to have spatial resolution similar to that of the gas. We test multiple DM density profiles, and we employ the sink particle method to represent the accreting star-forming region. We find that, for a range of DM configurations, the motion of the Pop III star-disk system serves to separate the positions of the protostars with respect to the DM density peak, such that there is insufficient DM to influence the formation and evolution of the protostars for more than approx. 5000 years. In addition, the star-disk system causes gravitational scattering of the central DM to lower densities, further decreasing the influence of DM over time. Any DM-powered phase of Pop III stars will thus be very short-lived for the typical multiple system, and DM will not serve to significantly prolong the life of Pop III stars.

  14. Stabilization effect of Weibel modes in relativistic laser fusion plasma

    NASA Astrophysics Data System (ADS)

    Belghit, Slimen; Sid, Abdelaziz

    2016-06-01

    In this work, the Weibel instability (WI) due to inverse bremsstrahlung (IB) absorption in a laser fusion plasma has been investigated. The stabilization effect due to the coupling of the self-generated magnetic field by WI with the laser wave field is explicitly shown. In this study, the relativistic effects are taken into account. Here, the basic equation is the relativistic Fokker-Planck (F-P) equation. The main obtained result is that the coupling of self-generated magnetic field with the laser wave causes a stabilizing effect of excited Weibel modes. We found a decrease in the spectral range of Weibel unstable modes. This decreasing is accompanied by a reduction of two orders in the growth rate of instable Weibel modes or even stabilization of these modes. It has been shown that the previous analysis of the Weibel instability due to IB has overestimated the values of the generated magnetic fields. Therefore, the generation of magnetic fields by the WI due to IB should not affect the experiences of an inertial confinement fusion.

  15. Failure mode and effect analysis-based quality assurance for dynamic MLC tracking systems

    SciTech Connect

    Sawant, Amit; Dieterich, Sonja; Svatos, Michelle; Keall, Paul

    2010-12-15

    Purpose: To develop and implement a failure mode and effect analysis (FMEA)-based commissioning and quality assurance framework for dynamic multileaf collimator (DMLC) tumor tracking systems. Methods: A systematic failure mode and effect analysis was performed for a prototype real-time tumor tracking system that uses implanted electromagnetic transponders for tumor position monitoring and a DMLC for real-time beam adaptation. A detailed process tree of DMLC tracking delivery was created and potential tracking-specific failure modes were identified. For each failure mode, a risk probability number (RPN) was calculated from the product of the probability of occurrence, the severity of effect, and the detectibility of the failure. Based on the insights obtained from the FMEA, commissioning and QA procedures were developed to check (i) the accuracy of coordinate system transformation, (ii) system latency, (iii) spatial and dosimetric delivery accuracy, (iv) delivery efficiency, and (v) accuracy and consistency of system response to error conditions. The frequency of testing for each failure mode was determined from the RPN value. Results: Failures modes with RPN{>=}125 were recommended to be tested monthly. Failure modes with RPN<125 were assigned to be tested during comprehensive evaluations, e.g., during commissioning, annual quality assurance, and after major software/hardware upgrades. System latency was determined to be {approx}193 ms. The system showed consistent and accurate response to erroneous conditions. Tracking accuracy was within 3%-3 mm gamma (100% pass rate) for sinusoidal as well as a wide variety of patient-derived respiratory motions. The total time taken for monthly QA was {approx}35 min, while that taken for comprehensive testing was {approx}3.5 h. Conclusions: FMEA proved to be a powerful and flexible tool to develop and implement a quality management (QM) framework for DMLC tracking. The authors conclude that the use of FMEA-based QM ensures

  16. The effect of mixed mode precracking on the mode 1 fracture toughness of composite laminates

    NASA Technical Reports Server (NTRS)

    Shankar, Prashanth; Bascom, Williard D.; Nairn, John A.

    1993-01-01

    We subjected double cantilever beam specimens from four different composite materials to mixed-mode precracking. Three different precracking mode 1 to mode 2 ratios were used--1 to 4, 1 to 1, and 4 to 1. Following precracking the specimens were tested for mode I fracture toughness. The mixed-mode precracking often influenced the mode 1 toughness and its influence persisted for as much as 60 mm of mode 1 crack growth. We tested composites with untoughened matrices, composites with rubber-toughened matrices, and composites with interlayer toughening. Depending on material type and precracking mode ratio, the precracking could cause either a significant increase or a significant decrease in the mode 1 fracture toughness.

  17. Asymmetric large-mode-area photonic crystal fiber structure with effective single-mode operation: design and analysis.

    PubMed

    Saini, Than Singh; Kumar, Ajeet; Sinha, Ravindra Kumar

    2016-03-20

    The asymmetrical structure of photonic crystal fiber has been reported for a large mode area with the single-mode operation. The design works on the principle of bend-induced mode filtering. The proposed structure can be designed (i) by introducing down-doped material rods in place of nine air holes of the inner ring near the core of the structure and (ii) by increasing the diameter of the rest of the three air holes of the same ring in the direction of bending. These three air holes together with nine down-doped material rods control the mode field inside the core region and hence the bending losses of the modes. The single-mode operation is ensured by introducing high bend loss for the first higher order mode and very low bend loss for the fundamental mode. The finite-element-method-based anisotropic perfectly matched layer boundary condition has been applied for accurate analysis of bend loss of the structure. Numerical results show that effective single-mode operation can be ensured with a mode area as large as 1530  μm2 at bend state with a bend radius of 30 cm. The proposed photonic crystal optical fiber with such a large mode area can have potential applications in compact high-power delivery devices such as high-power fiber lasers and amplifiers. PMID:27140567

  18. Mode splitting effect in FEMs with oversized Bragg resonators

    NASA Astrophysics Data System (ADS)

    Peskov, N. Yu.; Kaminsky, A. K.; Kuzikov, S. V.; Perelstein, E. A.; Sedykh, S. N.; Sergeev, A. S.

    2016-07-01

    Splitting of the fundamental mode in an oversized Bragg resonator with a step of the corrugation phase, which operates over the feedback loop involving the waveguide waves of different transverse structures, was found to be the result of mutual influence of the neighboring zones of the Bragg scattering. Theoretical description of this effect was developed within the framework of the advanced (four-wave) coupled-wave approach. It is shown that mode splitting reduces the selective properties, restricts the output power, and decreases the stability of the narrow-band operating regime in the free-electron maser (FEM) oscillators based on such resonators. The results of the theoretical analysis were confirmed by 3D simulations and "cold" microwave tests. Experimental data on Bragg resonators with different parameters in a 30-GHz FEM are presented. The possibility of reducing the mode splitting by profiling the corrugation parameters is shown. The use of the mode splitting effect for the output power enhancement by passive compression of the double-frequency pulse generated in the FEM with such a resonator is discussed.

  19. Effects of magnetosonic perturbations on electron temperature gradient driven modes and the stability of skin depth sized electron ballooning modes

    SciTech Connect

    Joiner, N.; Hirose, A.

    2007-11-15

    The effect of the magnetosonic perturbation {delta}B{sub parallel} on the growth of electron temperature gradient driven (ETG) modes and electron temperature gradient driven ballooning modes [Hirose, Plasma Phys. Control. Fusion 49, 145 (2007)] is investigated using local gyrokinetic analysis and numerical solution, with supporting simulations from the initial value code GS2 [Kotschenreuther, et al., Comp. Phys. Commun. 88, 128 (1996)]. The effect of {delta}B{sub parallel} on the ETG mode is found to depend on the competition between two physical processes related to magnetosonic compression. Local analysis of the ballooning mode appears to significantly overestimate growth rates of this instability. The electron temperature gradient driven ballooning mode has been observed in GS2 simulations. However, this work supports the conclusion that this instability will be subdominant to the ETG mode in normal tokamak regimes.

  20. The effect of the edge current density on confinement and kink mode stability in H-mode and VH-mode discharges

    SciTech Connect

    Ferron, J.R.; Lao, L.L.; Osborne, T.H.; Strait, E.J.; Taylor, T.S.; Thompson, S.J.; Turnbull, A.D.; Sauter, O.

    1994-07-01

    The effect of the local current density in the outer portion of a tokamak discharge [J({rho} {approximately} a)] is discussed in three situations. In a H-mode discharge, a strong reduction of J({rho} {approximately} a) results in the loss of the H-mode pressure pedestal. A smaller reduction in J({rho} {approximately} a) can prevent the transition from H-mode to VH-mode. Finally, a sufficiently large value of J({rho} {approximately} a) accompanied by a sufficiently large value of the pressure gradient in the same region of the discharge, can destabilize low-n (e.g., n = 1 to 5) kink-type modes in a VH-mode discharge. Conference Information: European conference on controlled fusion and plasma physics, Montpellier (France), 26 Jun - 1 Jul 1994

  1. Application of failure mode and effects analysis to treatment planning in scanned proton beam radiotherapy

    PubMed Central

    2013-01-01

    Background A multidisciplinary and multi-institutional working group applied the Failure Mode and Effects Analysis (FMEA) approach to the actively scanned proton beam radiotherapy process implemented at CNAO (Centro Nazionale di Adroterapia Oncologica), aiming at preventing accidental exposures to the patient. Methods FMEA was applied to the treatment planning stage and consisted of three steps: i) identification of the involved sub-processes; ii) identification and ranking of the potential failure modes, together with their causes and effects, using the risk probability number (RPN) scoring system, iii) identification of additional safety measures to be proposed for process quality and safety improvement. RPN upper threshold for little concern of risk was set at 125. Results Thirty-four sub-processes were identified, twenty-two of them were judged to be potentially prone to one or more failure modes. A total of forty-four failure modes were recognized, 52% of them characterized by an RPN score equal to 80 or higher. The threshold of 125 for RPN was exceeded in five cases only. The most critical sub-process appeared related to the delineation and correction of artefacts in planning CT data. Failures associated to that sub-process were inaccurate delineation of the artefacts and incorrect proton stopping power assignment to body regions. Other significant failure modes consisted of an outdated representation of the patient anatomy, an improper selection of beam direction and of the physical beam model or dose calculation grid. The main effects of these failures were represented by wrong dose distribution (i.e. deviating from the planned one) delivered to the patient. Additional strategies for risk mitigation, easily and immediately applicable, consisted of a systematic information collection about any known implanted prosthesis directly from each patient and enforcing a short interval time between CT scan and treatment start. Moreover, (i) the investigation of

  2. EFFECTS OF ASYMMETRIC FLOWS IN SOLAR CONVECTION ON OSCILLATION MODES

    SciTech Connect

    Baldner, Charles S.; Schou, Jesper

    2012-11-20

    Many helioseismic measurements suffer from substantial systematic errors. A particularly frustrating one is that time-distance measurements suffer from a large center to limb effect which looks very similar to the finite light travel time, except that the magnitude depends on the observable used and can have the opposite sign. This has frustrated attempts to determine the deep meridional flow in the solar convection zone, with Zhao et al. applying an ad hoc correction with little physical basis to correct the data. In this Letter, we propose that part of this effect can be explained by the highly asymmetrical nature of the solar granulation which results in what appears to the oscillation modes as a net radial flow, thereby imparting a phase shift on the modes as a function of observing height and thus heliocentric angle.

  3. Failure Mode Effects Analysis for an Accelerator Control System

    SciTech Connect

    Hartman, Steven M

    2009-01-01

    Failure mode effects analysis (FMEA) has been used in industry for design, manufacturing and assembly process quality control. It describes a formal approach for categorizing how a process may fail and for prioritizing failures based on their severity, frequency and likelihood of detection. Experience conducting a partial FMEA of an accelerator subsystem and its related control system will be reviewed. The applicability of the FMEA process to an operational accelerator control system will be discussed.

  4. Effects of difructose anhydride III (DFA III) administration on bile acids and growth of DFA III-assimilating bacterium Ruminococcus productus on rat intestine.

    PubMed

    Minamida, Kimiko; Kaneko, Maki; Ohashi, Midori; Sujaya, I Nengah; Sone, Teruo; Wada, Masaru; Yokota, Atsushi; Hara, Hiroshi; Asano, Kozo; Tomita, Fusao

    2005-06-01

    The growth of DFA III-assimilating bacteria in the intestines of rats fed 3% DFA III for 2 weeks was examined. Sixty-four percent of the DFA III intake had been assimilated on day 3 of ingestion, and almost all of the DFA III was assimilated at the end of the experiment. The DFA III-assimilating bacterium, Ruminococcus productus, in DFA III-fed rats was in the stationary state of 10(8)-10(9) cells/g dry feces within a week from 10(6) cells/g dry feces on day 1 of DFA III ingestion. The number of R. productus cells was associated with the amount of DFA III excreted in the feces. The acetic acid produced from DFA III by R. productus lowered the cecal pH to 5.8. In control-fed rats and DFA III-fed rats, 94% of secondary bile acids and 94% of primary bile acids, respectively, were accounted for in the total bile acids analyzed. DFA III ingestion increased the ratio of primary bile acids and changed the composition of fecal bile acids. In conclusion, R. productus assimilated DFA III, produced short chain fatty acids, and the cecal pH was lowered. The acidification of rat intestine perhaps inhibited secondary bile acid formation and decreased the ratio of secondary bile acids. Therefore, it is expected that DFA III may prevent colorectal cancer and be a new prebiotic candidate. PMID:16233830

  5. The Effect of Administration Mode on Test Performance and Score Precision, and Some Factors Contributing to Mode Differences.

    ERIC Educational Resources Information Center

    Pommerich, Mary

    This paper considers differences in modes of test administration, addressing three questions: (1) Do examinees respond to items in the same way across administration modes and computer interface variations? (2) What are some of the factors that can contribute to modal effects? and (3) Can item parameters calibrated from paper and pencil…

  6. Microstructural effects on fracture toughness of polycrystalline ceramics in combined mode I and mode II loading

    NASA Technical Reports Server (NTRS)

    Singh, D.; Shetty, D. K.

    1988-01-01

    Fracture toughness of polycrystalline alumina and ceria partially-stabilized tetragonal zirconia (CeO2-TZP) ceramics were assessed in combined mode I and mode II loading using precracked disk specimens in diametral compression. Stress states ranging from pure mode I, combined mode I and mode II, and pure mode II were obtained by aligning the center crack at specific angles relative to the loading diameter. The resulting mixed-mode fracture toughness envelope showed significant deviation to higher fracture toughness in mode II relative to the predictions of the linear elastic fracture mechanics theory. Critical comparison with corresponding results on soda-lime glass and fracture surface observations showed that crack surface resistance arising from grain interlocking and abrasion was the main source of the increased fracture toughness in mode II loading of the polycrystalline ceramics. The normalized fracture toughness for pure mode II loading, (KII/KIc), increased with increasing grain size for the CeO2-TZP ceramics. Quantitative fractography confirmed an increased percentage of transgranular fracture of the grains in mode II loading.

  7. 25 CFR 291.13 - When do Class III gaming procedures for an Indian tribe become effective?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false When do Class III gaming procedures for an Indian tribe... ECONOMIC ENTERPRISES CLASS III GAMING PROCEDURES § 291.13 When do Class III gaming procedures for an Indian tribe become effective? Upon approval of Class III gaming procedures for the Indian tribe under...

  8. Acoustic attenuation, phase and group velocities in liquid-filled pipes III: nonaxisymmetric propagation and circumferential modes in lossless conditions.

    PubMed

    Baik, Kyungmin; Jiang, Jian; Leighton, Timothy G

    2013-03-01

    Equations for the nonaxisymmetric modes that are axially and circumferentially propagating in a liquid-filled tube with elastic walls surrounded by air/vacuum are presented using exact elasticity theory. Dispersion curves for the axially propagating modes are obtained and verified through comparison with measurements. The resulting theory is applied to the circumferential modes, and the pressures and the stresses in the liquid-filled pipe are calculated under external forced oscillation by an acoustic source. This provides the theoretical foundation for the narrow band acoustic bubble detector that was subsequently deployed at the Target Test Facility (TTF) of the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL), TN. PMID:23463995

  9. Magnetospheric filter effect for Pc 3 Alfven mode waves

    NASA Technical Reports Server (NTRS)

    Zhang, X.; Comfort, R. H.; Gallagher, D. L.; Green, J. L.; Musielak, Z. E.; Moore, T. E.

    1995-01-01

    We present a ray-tracing study of the propagation of Pc 3 Alfven mode waves originating at the dayside magnetopause. This study reveals interesting features of magnetospheric filter effect for these waves. Pc 3 Alfven mode waves cannot penetrate to low Earth altitudes unless the wave frequency is below approximately 30 mHz. Configurations of the dispersion curves and the refractive index show that the gyroresonance and pseudo-cutoff introduced by the heavy ion O(+) block the waves. When the O(+) concentration is removed from the plasma composition, the barriers caused by the O(+) no longer exist, and waves with much higher frequencies than 30 mHz can penetrate to low altitudes. The result that the 30 mHz or lower frequency Alfven waves can be guided to low altitudes agrees with ground-based power spectrum observation at high altitudes.

  10. Magnetospheric filter effect for Pc 3 Alfven mode waves

    NASA Technical Reports Server (NTRS)

    Zhang, X.; Comfort, R. H.; Gallagher, D. L.; Green, J. L.; Musielak, Z. E.; Moore, T. E.

    1994-01-01

    We present a ray-tracing study of the propagation of Pc 3 Alfven mode waves originating at the dayside magnetopause. This study reveals interesting features of a magnetospheric filter effect for these waves. Pc 3 Alfven mode waves cannot penetrate to low Earth altitudes unless the wave frequency is below approximately 30 mHz. Configurations of the dispersion curves and the refractive index show that the gyroresonance and pseudo-cutoff introduced by the heavy ion O(+) block the waves. When the O(+) concentration is removed from the plasma composition, the barriers caused by the O(+) no longer exist, and waves with much higher frequencies than 30 mHz can penetrate to low altitudes. The result that the 30 mHz or lower frequency Alfven waves can be guided to low altitudes agrees with ground-based power spectrum observations at high latitudes.

  11. Atomic physics effects on tokamak edge drift-tearing modes

    SciTech Connect

    Hahm, T.S.

    1993-03-01

    The effects of ionization and charge exchange on the linear stability of drift-tearing modes are analytically investigated. In particular, the linear instability threshold {Delta}{sup Th}, produced by ion sound wave coupling is modified. In the strongly collisional regime, the ionization breaks up the near cancellation of the perturbed electric field and the pressure gradient along the magnetic field, and increases the threshold. In the semi-collisional regime, both ionization and charge exchange act as drag on the ion parallel velocity, and consequently decrease the threshold by reducing the effectiveness of ion sound wave propagation.

  12. Atomic physics effects on tokamak edge drift-tearing modes

    SciTech Connect

    Hahm, T.S.

    1993-03-01

    The effects of ionization and charge exchange on the linear stability of drift-tearing modes are analytically investigated. In particular, the linear instability threshold [Delta][sup Th], produced by ion sound wave coupling is modified. In the strongly collisional regime, the ionization breaks up the near cancellation of the perturbed electric field and the pressure gradient along the magnetic field, and increases the threshold. In the semi-collisional regime, both ionization and charge exchange act as drag on the ion parallel velocity, and consequently decrease the threshold by reducing the effectiveness of ion sound wave propagation.

  13. Linear canonical transformations of coherent and squeezed states in the Wigner phase space. III - Two-mode states

    NASA Technical Reports Server (NTRS)

    Han, D.; Kim, Y. S.; Noz, Marilyn E.

    1990-01-01

    It is shown that the basic symmetry of two-mode squeezed states is governed by the group SP(4) in the Wigner phase space which is locally isomorphic to the (3 + 2)-dimensional Lorentz group. This symmetry, in the Schroedinger picture, appears as Dirac's two-oscillator representation of O(3,2). It is shown that the SU(2) and SU(1,1) interferometers exhibit the symmetry of this higher-dimensional Lorentz group. The mathematics of two-mode squeezed states is shown to be applicable to other branches of physics including thermally excited states in statistical mechanics and relativistic extended hadrons in the quark model.

  14. Proton irradiation effects on advanced digital and microwave III-V components

    SciTech Connect

    Hash, G.L.; Schwank, J.R.; Shaneyfelt, M.R.; Sandoval, C.E.; Connors, M.P.; Sheridan, T.J.; Sexton, F.W.; Slayton, E.M.; Heise, J.A.; Foster, C.

    1994-09-01

    A wide range of advanced III-V components suitable for use in high-speed satellite communication systems were evaluated for displacement damage and single-event effects in high-energy, high-fluence proton environments. Transistors and integrated circuits (both digital and MMIC) were irradiated with protons at energies from 41 to 197 MeV and at fluences from 10{sup 10} to 2 {times} 10{sup 14} protons/cm{sup 2}. Large soft-error rates were measured for digital GaAs MESFET (3 {times} 10{sup {minus}5} errors/bit-day) and heterojunction bipolar circuits (10{sup {minus}5} errors/bit-day). No transient signals were detected from MMIC circuits. The largest degradation in transistor response caused by displacement damage was observed for 1.0-{mu}m depletion- and enhancement-mode MESFET transistors. Shorter gate length MESFET transistors and HEMT transistors exhibited less displacement-induced damage. These results show that memory-intensive GaAs digital circuits may result in significant system degradation due to single-event upset in natural and man-made space environments. However, displacement damage effects should not be a limiting factor for fluence levels up to 10{sup 14} protons/cm{sup 2} [equivalent to total doses in excess of 10 Mrad(GaAs)].

  15. Fiber pressure sensors based on periodical mode coupling effects

    NASA Astrophysics Data System (ADS)

    Lotem, Haim; Wang, Wen C.; Wang, Michael; Schaafsma, David; Skolnick, Bob; Grebel, Haim

    2005-05-01

    Fiber optic sensor technology offers the possibility of implementing low weight, high performance and cost effective health and damage assessment for infrastructure elements. Common fiber sensors are based on the effect of external action on the spectral response of a Fabry-Perot or a Bragg grating section, or on the modal dynamics in multimode (MM) fiber. In the latter case, the fiber itself acts as the sensor, giving it the potential for large range coverage. We were interested in this type of sensor because of its cost advantage in monitoring structural health. In the course of the research, a new type of a rugged modal filter device, based on off-center splicing, was developed. This device, in combination with a MM fiber, was found to be a potential single point-pressure sensing device. Additionally, by translating the pressing point along a MM sensing fiber with a constant load and speed, a sinusoidal intensity modulation was observed. This harmonic behavior, during load translation, is explained by the theory of mode coupling and dispersion. The oscillation period, L~0.43. mm, obtained at 980 nm in a Corning SMF-28 fiber, corresponds to the wavevector difference, Db, between the two-coupled modes, by L = 2p/Db. An additional outcome of the present research is the observation that the response of the loaded MM fiber is strongly dependent on the polarization state of the light traveling along the MM fiber due to different response of the modes to polarization active elements. Our main conclusions are that in MM fiber optic sensor design, special cautions need to be taken in order to stabilize the system, and that the sensitivity along a MM fiber sensor is periodic with a period of ~ 0.4 - 0.5 mm, depending on various fiber parameters and excited modes.

  16. Hydrodynamic effects of the tip movement on surface nanobubbles: a combined tapping mode, lift mode and force volume mode AFM study.

    PubMed

    Walczyk, Wiktoria; Hain, Nicole; Schönherr, Holger

    2014-08-28

    We report on an Atomic Force Microscopy (AFM) study of AFM tip-nanobubble interactions in experiments conducted on argon surface nanobubbles on HOPG (highly oriented pyrolytic graphite) in water in tapping mode, lift mode and Force Volume (FV) mode AFM. By subsequent data acquisition on the same nanobubbles in these three different AFM modes, we could directly compare the effect of different tip-sample interactions. The tip-bubble interaction strength was found to depend on the vertical and horizontal position of the tip on the bubble with respect to the bubble center. The interaction forces measured experimentally were in good agreement with the forces calculated using the dynamic interaction model. The strength of the hydrodynamic effect was also found to depend on the direction of the tip movement. It was more pronounced in the FV mode, in which the tip approaches the bubble from the top, than in the lift mode, in which the tip approaches the bubble from the side. This result suggests that the direction of tip movement influences the bubble deformation. The effect should be taken into account when nanobubbles are analysed by AFM in various scanning modes. PMID:24988375

  17. Impurity effects on trapped electron mode in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Du, Huarong; Wang, Zheng-Xiong; Dong, J. Q.

    2016-07-01

    The effects of impurity ions on the trapped electron mode (TEM) in tokamak plasmas are numerically investigated with the gyrokinetic integral eigenmode equation. It is shown that in the case of large electron temperature gradient ( η e ), the impurity ions have stabilizing effects on the TEM, regardless of peaking directions of their density profiles for all normalized electron density gradient R / L n e . Here, R is the major radius and L n e is the electron density gradient scale length. In the case of intermediate and/or small η e , the light impurity ions with conventional inwardly (outwardly) peaked density profiles have stabilizing effects on the TEM for large (small) R / L n e , while the light impurity ions with steep inwardly (outwardly) peaked density profiles can destabilize the TEM for small (large) R / L n e . Besides, the TEM driven by density gradient is stabilized (destabilized) by the light carbon or oxygen ions with inwardly (outwardly) peaked density profiles. In particular, for flat and/or moderate R / L n e , two independent unstable modes, corresponding respectively to the TEM and impurity mode, are found to coexist in plasmas with impurity ions of outwardly peaked density profiles. The high Z tungsten impurity ions play a stronger stabilizing role in the TEM than the low Z impurity ions (such as carbon and oxygen) do. In addition, the effects of magnetic shear and collision on the TEM instability are analyzed. It is shown that the collisionality considered in this work weakens the trapped electron response, leading to a more stable TEM instability, and that the stabilizing effects of the negative magnetic shear on the TEM are more significant when the impurity ions with outwardly peaked density profile are taken into account.

  18. Development and Application of Benchmark Examples for Mixed-Mode I/II Quasi-Static Delamination Propagation Predictions

    NASA Technical Reports Server (NTRS)

    Krueger, Ronald

    2012-01-01

    The development of benchmark examples for quasi-static delamination propagation prediction is presented and demonstrated for a commercial code. The examples are based on finite element models of the Mixed-Mode Bending (MMB) specimen. The examples are independent of the analysis software used and allow the assessment of the automated delamination propagation prediction capability in commercial finite element codes based on the virtual crack closure technique (VCCT). First, quasi-static benchmark examples were created for the specimen. Second, starting from an initially straight front, the delamination was allowed to propagate under quasi-static loading. Third, the load-displacement relationship from a propagation analysis and the benchmark results were compared, and good agreement could be achieved by selecting the appropriate input parameters. Good agreement between the results obtained from the automated propagation analysis and the benchmark results could be achieved by selecting input parameters that had previously been determined during analyses of mode I Double Cantilever Beam and mode II End Notched Flexure specimens. The benchmarking procedure proved valuable by highlighting the issues associated with choosing the input parameters of the particular implementation. Overall the results are encouraging, but further assessment for mixed-mode delamination fatigue onset and growth is required.

  19. The Emotional Child Witness Effect Survives Presentation Mode.

    PubMed

    Melinder, Annika; Burrell, Lisa; Eriksen, Maria Olaussen; Magnussen, Svein; Wessel, Ellen

    2016-01-01

    The emotional witness effect - the phenomenon whereby people are affected by the emotional manner in which a witness presents testimony - constitutes a possible source of wrongful decisions in legal contexts. One stereotypical view of abused children is that they should be sad when talking about their experiences of maltreatment, whereas children may in fact express a variety of emotional expressions when talking about abusive events. This raises the question as to whether there is an optimal mode in which to present child victim testimony that could reduce the possible influence of displayed emotions. In the present study, mock police interviews were carried out with female child actors, role-playing the victims of physical abuse by their stepfather, telling the same story with four emotional expressions (neutral, sad, angry, or positive). Laypersons (N = 465) were presented with the interviews as transcripts with the emotional reactions of the child witness noted, audio recordings, or videotaped recordings. Participants then rated the credibility of the victim witness. Replicating previous results, the "sad" expression elicited the highest credibility ratings across all modes of presentations. Presentation mode affected ratings of credibility, with the transcript versions resulting in the highest ratings. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26990221

  20. Estimation of the isotope effect on the lattice thermal conductivity of group IV and group III-V semiconductors

    NASA Astrophysics Data System (ADS)

    Morelli, D. T.; Heremans, J. P.; Slack, G. A.

    2002-11-01

    The isotope effect on the lattice thermal conductivity for group IV and group III-V semiconductors is calculated using the Debye-Callaway model modified to include both transverse and longitudinal phonon modes explicitly. The frequency and temperature dependences of the normal and umklapp phonon-scattering rates are kept the same for all compounds. The model requires as adjustable parameters only the longitudinal and transverse phonon Grüneisen constants and the effective sample diameter. The model can quantitatively account for the observed isotope effect in diamond and germanium but not in silicon. The magnitude of the isotope effect is predicted for silicon carbide, boron nitride, and gallium nitride. In the case of boron nitride the predicted increase in the room-temperature thermal conductivity with isotopic enrichment is in excess of 100%. Finally, a more general method of estimating normal phonon-scattering rate coefficients for other types of solids is presented.

  1. Effects of Humidity on Non-Hermetically Packaged III-V Structures and Devices

    NASA Technical Reports Server (NTRS)

    Leon, R.; Martin, S.; Lee, T.; Okuno, J.; Ruiz, R.; Gauldin, R.; Gaidis, M.; Smith, R.

    1999-01-01

    High humidity and temperature test (known as 85/85 tests) were performed on various III-V devices and structures to determine environmental effects in non-hermetically packaged GaAs membrane mixer diodes.

  2. Effects of damping on mode shapes, volume 1

    NASA Technical Reports Server (NTRS)

    Gates, R. M.

    1977-01-01

    Displacement, velocity, and acceleration admittances were calculated for a realistic NASTRAN structural model of space shuttle for three conditions: liftoff, maximum dynamic pressure and end of solid rocket booster burn. The realistic model of the orbiter, external tank, and solid rocket motors included the representation of structural joint transmissibilities by finite stiffness and damping elements. Methods developed to incorporate structural joints and their damping characteristics into a finite element model of the space shuttle, to determine the point damping parameters required to produce realistic damping in the primary modes, and to calculate the effect of distributed damping on structural resonances through the calculation of admittances.

  3. Failure modes and effects analysis in clinical engineering.

    PubMed

    Willis, G

    1992-01-01

    Failure modes and effects analysis (FMEA) is a proactive quality assurance procedure that has been commonly used to address potential design flaws and product misuses during the design stage of a product's life. FMEA is becoming commonplace among manufacturing companies but is relatively unknown outside of manufacturing circles. One potential new application of FMEA is by medical device end-users who could address design or functional concerns specific to their situation. The continued increase in the amount and complexity of medical instrumentation necessitates an aggressive stance towards safety in each hospital, such as is recommended in this paper. PMID:10117004

  4. Effects of mean flow on duct mode optimum suppression rates

    NASA Technical Reports Server (NTRS)

    Kraft, R. E.; Wells, W. R.

    1976-01-01

    The nature of the solution to the convected acoustic wave equation and associated boundary conditions for rectangular ducts containing uniform mean flow is examined in terms of the complex mapping between the wall admittance and characteristic mode eigenvalues. It is shown that the Cremer optimum suppression criteria must be modified to account for the effects of flow below certain critical values of the nondimensional frequency parameter of duct height divided by sound wavelength. The implications of these results on the design of low frequency suppressors are considered.

  5. Kinetic description of collective oscillations in a system of parametric spin waves. III. Long-wave collective modes

    SciTech Connect

    Morozov, V.G.; Mukhai, A.N.

    1988-10-01

    Long-wave collective oscillations in a system of parametric spin waves of a ferromagnet are studied on the basis of the kinetic equations for the Wigner distribution functions of the magnons. A study is made of the linear response of the magnetization m to a change in the internal field h (in the case of deviation of a packet of parametric waves from a stationary state), and boundary-value problem for finding the eigenfrequencies of the collective modes in a sample of finite volume is formulated. It is shown that allowance for the influence of the boundary conditions leads to discreteness of the frequency spectrum of the collective modes in the region of wave numbers q of the order of the reciprocal sample dimension L/sup /minus/1/. For a spherical sample, expressions are obtained for the discrete frequencies of long-wave collective modes corresponding to oscillations with longitudinal component h/sub z/ of the internal field that does not depend on the coordinate z. Criteria for stability of stationary states of the ferromagnet with respect to the excitation of auto-oscillations are obtained.

  6. Development and Application of Benchmark Examples for Mixed-Mode I/II Quasi-Static Delamination Propagation Predictions

    NASA Technical Reports Server (NTRS)

    Krueger, Ronald

    2012-01-01

    The development of benchmark examples for quasi-static delamination propagation prediction is presented. The example is based on a finite element model of the Mixed-Mode Bending (MMB) specimen for 50% mode II. The benchmarking is demonstrated for Abaqus/Standard, however, the example is independent of the analysis software used and allows the assessment of the automated delamination propagation prediction capability in commercial finite element codes based on the virtual crack closure technique (VCCT). First, a quasi-static benchmark example was created for the specimen. Second, starting from an initially straight front, the delamination was allowed to propagate under quasi-static loading. Third, the load-displacement as well as delamination length versus applied load/displacement relationships from a propagation analysis and the benchmark results were compared, and good agreement could be achieved by selecting the appropriate input parameters. The benchmarking procedure proved valuable by highlighting the issues associated with choosing the input parameters of the particular implementation. Overall, the results are encouraging, but further assessment for mixed-mode delamination fatigue onset and growth is required.

  7. Reflective liquid crystal light valve with hybrid field effect mode

    NASA Technical Reports Server (NTRS)

    Boswell, Donald D. (Inventor); Grinberg, Jan (Inventor); Jacobson, Alexander D. (Inventor); Myer, Gary D. (Inventor)

    1977-01-01

    There is disclosed a high performance reflective mode liquid crystal light valve suitable for general image processing and projection and particularly suited for application to real-time coherent optical data processing. A preferred example of the device uses a CdS photoconductor, a CdTe light absorbing layer, a dielectric mirror, and a liquid crystal layer sandwiched between indium-tin-oxide transparent electrodes deposited on optical quality glass flats. The non-coherent light image is directed onto the photoconductor; this reduces the impedance of the photoconductor, thereby switching the AC voltage that is impressed across the electrodes onto the liquid crystal to activate the device. The liquid crystal is operated in a hybrid field effect mode. It utilizes the twisted nematic effect to create a dark off-state (voltage off the liquid crystal) and the optical birefringence effect to create the bright on-state. The liquid crystal thus modulates the polarization of the coherent read-out or projection light responsively to the non-coherent image. An analyzer is used to create an intensity modulated output beam.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  9. Failure mode and effects analysis application to critical care medicine.

    PubMed

    Duwe, Beau; Fuchs, Barry D; Hansen-Flaschen, John

    2005-01-01

    In July 2001, the United States Joint Commission on Accreditation of Health care Organizations adopted a new leadership standard that requires department heads in health care organizations to perform at least one Failure Mode and Effects Analysis (FMEA) every year. This proactive approach to error prevention has proven to be highly effective in other industries, notably aerospace, but remains untested in acute care hospitals. For several reasons, the intensive care unit (ICU) potentially is an attractive setting for early adoption of FMEA; however, successful implementation of FMEA in ICUs is likely to require strong, effective leadership and a sustained commitment to prevent errors that may have occurred rarely or never before in the local setting. This article describes FMEA in relation to critical care medicine and reviews some of the attractive features together with several potential pitfalls that are associated with this approach to error prevention in ICUs. PMID:15579350

  10. Effects of ionic strength and fulvic acid on adsorption of Tb(III) and Eu(III) onto clay

    NASA Astrophysics Data System (ADS)

    Poetsch, Maria; Lippold, Holger

    2016-09-01

    High salinity and natural organic matter are both known to facilitate migration of toxic or radioactive metals in geochemical systems, but little is known on their combined effect. We investigated complexation of Tb(III) and Eu(III) (as analogues for trivalent actinides) with fulvic acid and their adsorption onto a natural clay in the presence of NaCl, MgCl2 and CaCl2 up to very high ionic strengths. 160Tb, 152Eu and 14C-labelled fulvic acid were employed as radiotracers, allowing investigations at very low concentrations according to probable conditions in far-field scenarios of nuclear waste repositories. A combined Kd approach (Linear Additive Model) was tested for suitability in predicting solid-liquid distribution of metals in the presence of organic matter based on the interactions in the constituent subsystems. In this analysis, it could be shown that high ionic strength does not further enhance the mobilizing potential of humic matter. A quantitative reproduction of the influence of fulvic acid failed for most systems under study. Assumptions and limitations of the model are discussed.

  11. Effects of ionic strength and fulvic acid on adsorption of Tb(III) and Eu(III) onto clay.

    PubMed

    Poetsch, Maria; Lippold, Holger

    2016-09-01

    High salinity and natural organic matter are both known to facilitate migration of toxic or radioactive metals in geochemical systems, but little is known on their combined effect. We investigated complexation of Tb(III) and Eu(III) (as analogues for trivalent actinides) with fulvic acid and their adsorption onto a natural clay in the presence of NaCl, MgCl2 and CaCl2 up to very high ionic strengths. (160)Tb, (152)Eu and (14)C-labelled fulvic acid were employed as radiotracers, allowing investigations at very low concentrations according to probable conditions in far-field scenarios of nuclear waste repositories. A combined Kd approach (Linear Additive Model) was tested for suitability in predicting solid-liquid distribution of metals in the presence of organic matter based on the interactions in the constituent subsystems. In this analysis, it could be shown that high ionic strength does not further enhance the mobilizing potential of humic matter. A quantitative reproduction of the influence of fulvic acid failed for most systems under study. Assumptions and limitations of the model are discussed. PMID:27454893

  12. Effect of multiperforated plates on the acoustic modes in combustors

    NASA Astrophysics Data System (ADS)

    Gullaud, Elsa; Mendez, Simon; Sensiau, Claude; Nicoud, Franck; Poinsot, Thierry

    2009-06-01

    The analytical model derived by Howe assessing the acoustic effect of perforated plates has been implemented in a 3D Helmholtz solver. This solver allows one to compute the acoustic modes of industrial chambers taking into account the multiperforated plates present for the cooling of the walls. An academic test case consisting of two coaxial cylinders, with the inner one being perforated is used to validate the implementation in the general purpose AVSP code. This case is also used to show the effects of the presence of the plates. In particular, the sensitivity of the acoustic damping to the bias flow speed will be studied. A maximum absorption speed is shown, and the behaviour towards an infinite speed will be illustrated by the academic case. Computations are also conducted in the case of an industrial helicopter chamber. The value of the maximum absorption speed is discussed to explain why the modes are in fact not much absorbed by the perforated plates, and that the frequencies are the same as for walls. To cite this article: E. Gullaud et al., C. R. Mecanique 337 (2009).

  13. Gravitational Effects on Collective Modes of Superfluid Shells

    NASA Astrophysics Data System (ADS)

    Padavić, Karmela; Sun, Kuei; Lannert, Courtney; Vishveshwara, Smitha

    We study the effects of gravity on collective excitations of shell-shaped Bose-Einstein condensates (BECs). Superfluid shells are of general interest as examples of hollow geometries that can be produced in ultracold atoms in bubble-trap potentials or optical lattices. Our approach to analyzing superfluid shells is based on a Gross-Pitaevskii mean field theory and hydrodynamic equations derived from it. Considering a spherically symmetric BEC in general, there are distinct collective excitation spectra for the cases of a fully filled sphere and a very thin shell. Furthermore, an adiabatic change in the potential producing a slow transition from one geometry to the other shows a characteristic evolution. Given that in most realistic experimental conditions gravity cannot be neglected we investigate its effects on the equilibrium profile and the collective modes in the very thin shell limit. We analytically obtain the full excitation spectrum for the thin shell geometry and account for gravity perturbatively at length and energy scales that describe a stable matter-wave bubble. We find that gravity breaks spherical symmetry of the equilibrium density profile and affects the collective excitations by coupling adjacent modes in the angular direction.

  14. Scaling of divertor power footprint width in RF-heated type-III ELMy H-mode on the EAST superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Wang, L.; Guo, H. Y.; Xu, G. S.; Liu, S. C.; Gan, K. F.; Wang, H. Q.; Gong, X. Z.; Liang, Y.; Zou, X. L.; Hu, J. S.; Chen, L.; Xu, J. C.; Liu, J. B.; Yan, N.; Zhang, W.; Chen, R.; Shao, L. M.; Ding, S.; Hu, G. H.; Feng, W.; Zhao, N.; Xiang, L. Y.; Liu, Y. L.; Li, Y. L.; Sang, C. F.; Sun, J. Z.; Wang, D. Z.; Ding, H. B.; Luo, G. N.; Chen, J. L.; Gao, X.; Hu, L. Q.; Wan, B. N.; Li, J.; the EAST Team

    2014-11-01

    Dedicated experiments for the scaling of divertor power footprint width have been performed in the ITER-relevant radio-frequency (RF)-heated H-mode scheme under the lower single null, double null and upper single null divertor configurations in the Experimental Advanced Superconducting Tokamak (EAST) under lithium wall coating conditioning. A strong inverse scaling of the edge localized mode (ELM)-averaged power fall-off width with the plasma current (equivalently the poloidal field) has been demonstrated for the attached type-III ELMy H-mode as λq \\propto Ip-1.05 by various heat flux diagnostics including the divertor Langmuir probes (LPs), infra-red (IR) thermograph and reciprocating LPs on the low-field side. The IR camera and divertor LP measurements show that λq,IR ≈ {λq,div{-LPs}}/{1.3}=1.15Bp,omp-1.25 , in good agreement with the multi-machine scaling trend during the inter-ELM phase between type-I ELMs or ELM-free enhanced Dα (EDA). H-mode. However, the magnitude is nearly doubled, which may be attributed to the different operation scenarios or heating schemes in EAST, i.e., dominated by electron heating. It is also shown that the type-III ELMs only broaden the power fall-off width slightly, and the ELM-averaged width is representative for the inter-ELM period. Furthermore, the inverse Ip (Bp) scaling appears to be independent of the divertor configurations in EAST. The divertor power footprint integral width, fall-off width and dissipation width derived from EAST IR camera measurements follow the relation, λint ≅ λq + 1.64S, yielding λ_intEAST =(1.39+/- 0.03)λqEAST +(0.97+/- 0.35) mm . Detailed analysis of these three characteristic widths was carried out to shed more light on their extrapolation to ITER.

  15. Retrieval Mode Distinguishes the Testing Effect from the Generation Effect

    ERIC Educational Resources Information Center

    Karpicke, Jeffrey D.; Zaromb, Franklin M.

    2010-01-01

    A series of four experiments examined the effects of generation vs. retrieval practice on subsequent retention. Subjects were first exposed to a list of target words. Then the subjects were shown the targets again intact for Read trials or they were shown fragments of the targets. Subjects in Generate conditions were told to complete the fragments…

  16. Mode Transitions in Magnetically Shielded Hall Effect Thrusters

    NASA Technical Reports Server (NTRS)

    Sekerak, Michael J.; Longmier, Benjamin W.; Gallimore, Alec D.; Huang, Wensheng; Kamhawi, Hani; Hofer, Richard R.; Jorns, Benjamin A.; Polk, James E.

    2014-01-01

    A mode transition study is conducted in magnetically shielded thrusters where the magnetic field magnitude is varied to induce mode transitions. Three different oscillatory modes are identified with the 20-kW NASA-300MS-2 and the 6-kW H6MS: Mode 1) global mode similar to unshielded thrusters at low magnetic fields, Mode 2) cathode oscillations at nominal magnetic fields, and Mode 3) combined spoke, cathode and breathing mode oscillations at high magnetic fields. Mode 1 exhibits large amplitude, low frequency (1-10 kHz), breathing mode type oscillations where discharge current mean value and oscillation amplitude peak. The mean discharge current is minimized while thrust-to-power and anode efficiency are maximized in Mode 2, where higher frequency (50-90 kHz), low amplitude, cathode oscillations dominate. Thrust is maximized in Mode 3 and decreases by 5-6% with decreasing magnetic field strength. The presence or absence of spokes and strong cathode oscillations do not affect each other or discharge current. Similar to unshielded thrusters, mode transitions and plasma oscillations affect magnetically shielded thruster performance and should be characterized during system development.

  17. [Failure mode and effect analysis: application in chemotherapy].

    PubMed

    Chuang, Ching-Hui; Chuang, Sheu-Wen

    2009-08-01

    Medical institutions are increasingly concerned about ensuring the safety of patients under their care. Failure mode and effect analysis (FMEA) is a qualitative approach based on a proactive process. Strongly promoted by the Joint Commission Accredited of Health Organization (JCAHO) since 2002, FMEA has since been adopted and widely practiced in healthcare organizations to assess and analyze clinical error events. FMEA has proven to be an effective method of minimizing errors in both manufacturing and healthcare industries. It predicts failure points in systems and allows an organization to address proactively the causes of problems and prioritize improvement strategies. The application of FMEA in chemotherapy at our department identified three main failure points: (1) inappropriate chemotherapy standard operating procedures (SOPs), (2) communication barriers, and (3) insufficient training of nurses. The application of FMEA in chemotherapy is expected to enhance the sensitivity and proactive abilities of healthcare practitioners during potentially risky situations as well as to improve levels of patient care safety. PMID:19634100

  18. Failure modes and effects analysis (RADL Item 2-23)

    SciTech Connect

    1980-04-01

    The Pilot Plant is a central receiver design concept. It is comprised of five major subsystems as shown schematically, plus a set of equipment (Plant Support Subsystem) used to support total plant operation. The failure modes and effects analysis (FMEA) is a bottom-up analysis used to identify the failure characteristics of the system (total equipment used to produce electrical power), that is, the failure of a single component is assumed and the effect of that failure upon the system is determined. The FMEA is concerned with the plant from an operational standpoint (i.e., the production of electrical power). This analysis was performed to the component level. This was interpreted as a valve, computer, measurement sensor and its associated signal conditioning, an electronic black box, etc.

  19. Application of failure mode and effects analysis (FMEA) to pretreatment phases in tomotherapy.

    PubMed

    Broggi, Sara; Cantone, Marie Claire; Chiara, Anna; Di Muzio, Nadia; Longobardi, Barbara; Mangili, Paola; Veronese, Ivan

    2013-01-01

    The aim of this paper was the application of the failure mode and effects analysis (FMEA) approach to assess the risks for patients undergoing radiotherapy treatments performed by means of a helical tomotherapy unit. FMEA was applied to the preplanning imaging, volume determination, and treatment planning stages of the tomotherapy process and consisted of three steps: 1) identification of the involved subprocesses; 2) identification and ranking of the potential failure modes, together with their causes and effects, using the risk probability number (RPN) scoring system; and 3) identification of additional safety measures to be proposed for process quality and safety improvement. RPN upper threshold for little concern of risk was set at 125. A total of 74 failure modes were identified: 38 in the stage of preplanning imaging and volume determination, and 36 in the stage of planning. The threshold of 125 for RPN was exceeded in four cases: one case only in the phase of preplanning imaging and volume determination, and three cases in the stage of planning. The most critical failures appeared related to (i) the wrong or missing definition and contouring of the overlapping regions, (ii) the wrong assignment of the overlap priority to each anatomical structure, (iii) the wrong choice of the computed tomography calibration curve for dose calculation, and (iv) the wrong (or not performed) choice of the number of fractions in the planning station. On the basis of these findings, in addition to the safety strategies already adopted in the clinical practice, novel solutions have been proposed for mitigating the risk of these failures and to increase patient safety. PMID:24036868

  20. Adsorption of fluoride on synthetic iron (III), zirconium(IV) and binary iron(III)-zirconium (IV) oxides: comparative assessment on pH effect and isotherm.

    PubMed

    Biswas, Krishna; Bandhopadhyay, Durjoy; Ghosh, Uday Chand

    2008-04-01

    Fluoride is an accumulative poison at high dose of intake for humans and animals. In the present study, the sorption of fluoride from aqueous solution has been investigated on synthetic hydrous ferric oxide (HFO), hydrous zirconium oxide (HZO) and hydrous zirconium(IV)-iron(III) oxide (HZFO) by batch mode experiments. Both HFO and HZFO were crystalline and HZO was amorphous in nature. The parametes studied were the effect of pH and sorption equilibriums. The results showed increase in fluoride-sorption with increasing pH from nearly 2.0 to 5.0, 4.6 and 6.8 for HFO, HZO and HZFO, respectively. Analysis of temperature dependent sorption data obtained at equilibrium solution pH 6.8 (+/- 0.2) has been described by the Langmuir, Freundlich, Temkin and Redlich-Peterson isotherm model equations. The present sorption data fit, in general, found very well with the Langmuir and Redlich-Peterson models; and the data fit for HZFO and HFO found to increase, but for HZO the data found to decrease with increasing temperature. The computed thermodynamic parameters such as deltaG0, delltaH0 and deltaS0 from the Langmuir equilibrium constant (b, L/Umg) values show that the fluoride-sorption on HZFO was more spontaneous and endothermic process compared to HFO. The deltaH0 value obtained for fluoride adsorption on HZO indicates exothermic nature. PMID:19295101

  1. Resistivity and sheared rotation effects on the toroidal external kink mode

    NASA Astrophysics Data System (ADS)

    Cole, A. J.; Brennan, D. P.; Finn, J. M.

    2014-10-01

    We present PEST-III analysis of the toroidal external kink with plasma resistivity and sheared rotation for a range of equilibria varying elongation, driven unstable by increasing β. The results show that the typical ordering for marginally stable β values is βrp,rw <βrp,iw <βip,rw <βip,iw , where rp,ip signify resistive or ideal plasma, and iw,rw indicate ideal wall or resistive wall (no-wall). The two resistive plasma β limits are significantly lower than the two ideal plasma values. We vary aspects of the tearing layer physics by means of a variational principle with Padé approximants, and compare with a general computational solution for the layers to gain insight. We also include pressure gradient and local velocity shear within the layers. Global rotation shear Ω' is included in the form of a relative rotation of the q = 2 , 3 , ... surfaces and we investigate the resultant effect on the poloidal mode number spectrum. We then present a model for active feedback control, which is the toroidal generalization building on recent results in cylindrical mode control theory [D. P. Brennan and J. M. Finn, submitted to Phys. Plasmas (2014)].

  2. Iron (III) Matrix Effects on Mineralization and Immobilization of Actinides

    SciTech Connect

    Cynthia-May S. Gong; Tyler A. Sullens; Kenneth R. Czerwinski

    2006-01-01

    Abstract - A number of models for the Yucca Mountain Project nuclear waste repository use studies of actinide sorption onto well-defined iron hydroxide materials. In the case of a waste containment leak, however, a complex interaction between dissolved waste forms and failed containment vessel components can lead to immediate precipitation of migratory iron and uranyl in the silicate rich near-field environment. Use of the Fe(III) and UO22+ complexing agent acetohydroxamic acid (AHA) as a colorimetric agent for visible spectrophotometry is well-known. Using the second derivative of these spectra a distinct shift in iron complexation in the presence of silicate is seen that is not seen with uranyl or alone. Silica also decreases the ability of uranyl and ferric solutions to absorb hydroxide, hastening precipitation. These ferric silicate precipitates are highly amorphous and soluble. Precipitates formed in the presence of uranyl below ~1 mol% exhibit lower solubility than precipitates from up to 50 mol % and of uranyl silicates alone.

  3. An effective model for microscopic intrinsic localized modes.

    SciTech Connect

    Kalosakas, G.; Bishop, A. R.

    2001-01-01

    We present a system of coupled degrees of freedom that can effectively describe the localization of intra-molecular excitations in the charge transfer solid PtCl. These excitations correspond to the Raman active motion of chlorines (symmetric Pt - Cl stretching). By fitting two parameters of the model we obtain an accurate description of the strong red-shifts that appear in the overtone Raman spectra of the isotopically pure material. The resulting intrinsic localized modes extend on length scales of the order of nanometers. With the same set of parameters the model can reproduce the specific structure of the Raman spectra of naturally abundant PtCl, which contains a random distribution of chloride isotopes.

  4. Radiology failure mode and effect analysis: what is it?

    PubMed

    Abujudeh, Hani H; Kaewlai, Rathachai

    2009-08-01

    Proactive prevention of medical errors is critical in medical practice. Root cause analysis (RCA) is a conventional method used to deal with errors that result in an adverse event. However, RCA has several limitations. An analytic method for health care risk management, health care failure mode and effect analysis (FMEA), has been introduced relatively recently. Health care FMEA combines several existing analytic approaches into one simple tool with which to analyze a particular health care process, determine the risks associated with it, and develop corrective actions and outcome measures. The authors provide a brief history of health care FMEA, describe its validation process, and relate their experience with its use in a radiology department. PMID:19703888

  5. Diamagnetic drift effects on the low-n magnetohydrodynamic modes at the high mode pedestal with plasma rotation

    NASA Astrophysics Data System (ADS)

    Zheng, L. J.; Kotschenreuther, M. T.; Valanju, P.

    2014-06-01

    The diamagnetic drift effects on the low-n magnetohydrodynamic instabilities at the high-mode (H-mode) pedestal are investigated in this paper with the inclusion of bootstrap current for equilibrium and rotation effects for stability, where n is the toroidal mode number. The AEGIS (Adaptive EiGenfunction Independent Solutions) code [L. J. Zheng and M. T. Kotschenreuther, J. Comp. Phys. 211 (2006)] is extended to include the diamagnetic drift effects. This can be viewed as the lowest order approximation of the finite Larmor radius effects in consideration of the pressure gradient steepness at the pedestal. The H-mode discharges at Jointed European Torus is reconstructed numerically using the VMEC code [P. Hirshman and J. C. Whitson, Phys. Fluids 26, 3553 (1983)], with bootstrap current taken into account. Generally speaking, the diamagnetic drift effects are stabilizing. Our results show that the effectiveness of diamagnetic stabilization depends sensitively on the safe factor value (qs) at the safety-factor reversal or plateau region. The diamagnetic stabilization are weaker, when qs is larger than an integer; while stronger, when qs is smaller or less larger than an integer. We also find that the diamagnetic drift effects also depend sensitively on the rotation direction. The diamagnetic stabilization in the co-rotation case is stronger than in the counter rotation case with respect to the ion diamagnetic drift direction.

  6. Failure mode and weakening effect of water on sandstone

    NASA Astrophysics Data System (ADS)

    Baud, Patrick; Zhu, Wenlu; Wong, Teng-Fong

    2000-07-01

    Previous studies have shown that brittle strength of a rock is generally reduced in the presence of water. However, for siliciclastic rocks, there is a paucity of data on the waterweakening behavior in the cataclastic flow regime. To compare the weakening effect of water in the brittle faulting and cataclastic flow regime, triaxial compression experiments were conducted on the Berea, Boise, Darley Dale, and Gosford sandstones (with nominal porosities ranging from 11% to 35%) under nominally dry and saturated conditions at room temperature. Inelastic behavior and failure mode of the nominal dry samples were qualitatively similar to those of water-saturated samples. At elevated pressures, shear localization was inhibited, and all the samples failed by strain hardening. The compactive yield strengths (associated with the onset of shear-enhanced compaction) in the saturated samples were lower than those in the dry samples deformed under comparable pressure conditions by 20% to 70%. The reductions of brittle strength in the presence of water ranged from 5% to 17%. The water-weakening effects were most and least significant in the Gosford and Berea sandstones, respectively. The relation between water weakening and failure mode is consistently explained by micromechanical models formulated on the basis that the specific surface energy in the presence of water is lowered than that in vacuum by the ratio λ. In accordance with the Hertzian fracture model the initial yield stress in the compactive cataclastic flow regime scales with the grain-crushing pressure, which is proportional to λ3/2. In the brittle faulting regime, damage mechanics models predict that the uniaxial compressive strength scales with λ1/2. In the presence of water the confined brittle strength is lower due to reductions of both the specific surface energy and friction coefficient.

  7. Can dispersal mode predict corridor effects on plant parasites?

    SciTech Connect

    Sullivan, Lauren, L.; Johnson, Brenda, L.; Brudvig, Lars, A.; Haddad, Nick, M.

    2011-08-01

    Habitat corridors, a common management strategy for increasing connectivity in fragmented landscapes, have experimentally validated positive influences on species movement and diversity. However, long-standing concerns that corridors could negatively impact native species by spreading antagonists, such as disease, remain largely untested. Using a large-scale, replicated experiment, we evaluated whether corridors increase the incidence of plant parasites. We found that corridor impacts varied with parasite dispersal mode. Connectivity provided by corridors increased incidence of biotically dispersed parasites (galls on Solidago odora) but not of abiotically dispersed parasites (foliar fungi on S. odora and three Lespedeza spp.). Both biotically and abiotically dispersed parasites responded to edge effects, but the direction of responses varied across species. Although our results require additional tests for generality to other species and landscapes, they suggest that, when establishing conservation corridors, managers should focus on mitigating two potential negative effects: the indirect effects of narrow corridors in creating edges and direct effects of corridors in enhancing connectivity of biotically dispersed parasites.

  8. Investigation of ELM [edge localized mode] Dynamics with the Resonant Magnetic Perturbation Effects

    SciTech Connect

    Pankin, Alexei Y.; Kritz, Arnold H.

    2011-07-19

    Topics covered are: anomalous transport and E x B flow shear effects in the H-mode pedestal; RMP (resonant magnetic perturbation) effects in NSTX discharges; development of a scaling of H-mode pedestal in tokamak plasmas with type I ELMs (edge localized modes); and divertor heat load studies.

  9. The Games Children Play III: More Comments on Effective Teaching

    ERIC Educational Resources Information Center

    Humphries, Charlotte A.; Ashy, Madge

    2013-01-01

    In the years since the authors published two articles with tips for effective teaching, they have acquired and developed more advice and impressions on teaching. This article presents ideas that can help physical educators become increasingly effective in their teaching.

  10. Twist effect and sensing of few mode polymer fibre Bragg gratings

    NASA Astrophysics Data System (ADS)

    Yan, Binbin; Luo, Yanhua; Bhowmik, Kishore; Rajan, Ginu; Ji, Minning; Wen, Jianxiang; Peng, Gang-Ding

    2016-01-01

    For the development of the twist sensor based on few mode polymer optical fibre (POF) gratings, we investigated the twist effect of few mode (FM) POF Bragg gratings with large twist, and found the twist effect on reflection is highly mode dependent-insignificant on the fundamental mode and considerable on higher order modes, which seems closely related to the symmetry of modal field. In addition, Bragg wavelengths of both the fundamental mode and higher modes red-shift with the twisting and blue-shift with the twist releasing, and they almost display the similar response trend without any mode dependence. Further analysis found that the red-shift of the Bragg wavelength should be attributed to the redistribution of the pre-strain applied upon the POF, activated by twist. Finally, based on the reflection response to the twist, one kind of twist sensing scheme with few mode POF gratings has been demonstrated, showing great potential as a twist sensor.

  11. The effect of ligand dynamics on heme electronic transition band III in myoglobin.

    PubMed

    Nienhaus, Karin; Lamb, Don C; Deng, Pengchi; Nienhaus, G Ulrich

    2002-02-01

    Band III is a near-infrared electronic transition at ~13,000 cm(-1) in heme proteins that has been studied extensively as a marker of protein conformational relaxation after photodissociation of the heme-bound ligand. To examine the influence of the heme pocket structure and ligand dynamics on band III, we have studied carbon monoxide recombination in a variety of myoglobin mutants after photolysis at 3 K using Fourier transform infrared temperature-derivative spectroscopy with monitoring in three spectral ranges, (1) band III, the mid-infrared region of (2) the heme-bound CO, and (3) the photodissociated CO. Here we present data on mutant myoglobins V68F and L29W, which both exhibit pronounced ligand movements at low temperature. From spectral and kinetic analyses in the mid-infrared, a small number of photoproduct populations can be distinguished, differing in their distal heme pocket conformations and/or CO locations. We have decomposed band III into its individual photoproduct contributions. Each photoproduct state exhibits a different "kinetic hole-burning" (KHB) effect, a coupling of the activation enthalpy for rebinding to the position of band III. The analysis reveals that the heme pocket structure and the photodissociated CO markedly affect the band III transition. A strong kinetic hole-burning effect results only when the CO ligand resides in the docking site on top of the heme group. Migration of CO away from the heme group leads to an overall blue shift of band III. Consequently, band III can be used as a sensitive tool to study ligand dynamics after photodissociation in heme proteins. PMID:11806945

  12. Mode competition effects in free electron lasers and gyrotrons

    SciTech Connect

    Levush, B.; Antonsen, T.M.

    1990-01-01

    In many cases in high frequency, high power coherent radiation generators (such as free electron laser and gyrotrons) the linear gain is positive for many modes and therefore these modes will grow and compete for the beam energy. The questions related to mode competition, coherency of the radiation and maximization of the interaction efficiency are of great importance. To address these issues simple multi-mode models have been formulated. This paper is a short review of the recent results from both simulation and analyses of these models. 3 figs.

  13. The effect of initial conditions on the electromagnetic radiation generation in type III solar radio bursts

    SciTech Connect

    Schmitz, H.; Tsiklauri, D.

    2013-06-15

    Extensive particle-in-cell simulations of fast electron beams injected in a background magnetised plasma with a decreasing density profile were carried out. These simulations were intended to further shed light on a newly proposed mechanism for the generation of electromagnetic waves in type III solar radio bursts [D. Tsiklauri, Phys. Plasmas, 18, 052903 (2011)]. The numerical simulations were carried out using different density profiles and fast electron distribution functions. It is shown that electromagnetic L and R modes are excited by the transverse current, initially imposed on the system. In the course of the simulations, no further interaction of the electron beam with the background plasma could be observed.

  14. OCEAN OUTFALLS. III: EFFECT OF DIFFUSER DESIGN ON SUBMERGED WASTEFIELD

    EPA Science Inventory

    The effects of spacing and jet momentum flux on the characteristics of submerged wastefields produced by multi-port ocean outfalls in linearly stratified currents were investigated experimentally. Within the range studied the primary effect of these variables is on the rise heigh...

  15. Effects of Al(III) and nano-Al13 species on malate dehydrogenase activity.

    PubMed

    Yang, Xiaodi; Cai, Ling; Peng, Yu; Li, Huihui; Chen, Rong Fu; Shen, Ren Fang

    2011-01-01

    The effects of different aluminum species on malate dehydrogenase (MDH) activity were investigated by monitoring amperometric i-t curves for the oxidation of NADH at low overpotential using a functionalized multi-wall nanotube (MWNT) modified glass carbon electrode (GCE). The results showed that Al(III) and Al(13) can activate the enzymatic activity of MDH, and the activation reaches maximum levels as the Al(III) and Al(13) concentration increase. Our study also found that the effects of Al(III) and Al(13) on the activity of MDH depended on the pH value and aluminum speciation. Electrochemical and circular dichroism spectra methods were applied to study the effects of nano-sized aluminum compounds on biomolecules. PMID:22163924

  16. Dislocation effects in FinFETs for different III-V compound semiconductors

    NASA Astrophysics Data System (ADS)

    Hur, Ji-Hyun; Jeon, Sanghun

    2016-04-01

    While Si-based devices are facing the limits of scaling, III-V materials, having high mobility, have attracted more and more attention. However, their advantages are obtained by ignoring the drawbacks of inevitably present dislocations. In this paper, we present a theoretical model that describes the degradation in carrier mobility caused by these inevitable charged dislocations in nanometer-sized, quantum-confined III-V compound semiconductor fin-shaped field effect transistors. We conclude that the Fermi-level pinning effect needs to be resolved to give carriers high enough energy (Fermi energy in the channel) to effectively ignore Coulomb scattering of charges at dislocations in a channel made by III-V compound semiconductors.

  17. Effects of subchronic exposure to Caramel Colour III on the immune system in mice.

    PubMed

    Thuvander, A; Oskarsson, A

    1994-01-01

    Administration of Caramel Colour III is associated with lymphopenia in laboratory animals, especially if the animals are fed a vitamin B6-deficient diet. Recently, functional immunological alterations in rats exposed to Caramel Colour III have been reported. The component of Caramel Colour III that is responsible for the immunological effects has been shown to be 2-acetyl-4-tetrahydroxybutyl imidazole (THI). In the present study, female Balb/c mice fed a diet with a relatively high vitamin B6 content were exposed to 2 or 10% of a commercial Caramel Colour III preparation with a low THI content (less than 25 ppm) in the drinking water for 9 wk. Although this treatment did not induce a lymphopenia in the exposed mice, flow cytometric analysis of lymphocyte subpopulations demonstrated reductions in the CD4+ and CD8+ cell populations. In addition, the proliferative response of spleen cells to B and T cell mitogens was significantly reduced in the mice exposed to 2% Caramel Colour III. No changes were observed in natural killer cell activity or in the humoral antibody response to a viral antigen. The results indicate that Caramel Colour III that meets the specified limit of less than 25 mg THI/kg may, nevertheless, interfere with the lymphoid system in mice with an adequate vitamin B6 status. PMID:8132168

  18. Effects of reactive Mn(III)-oxalate complexes on structurally intact plant cell walls

    NASA Astrophysics Data System (ADS)

    Summering, J. A.; Keiluweit, M.; Goni, M. A.; Nico, P. S.; Kleber, M.

    2011-12-01

    Lignin components in the in plant litter are commonly assumed to have longer residence times in soil than many other compounds, which are supposedly, more easily degradable. The supposed resistance of lignin compounds to decomposition is generally attributed to the complex chain of biochemical steps required to create footholds in the non-porous structure of ligno-cellulose in cell walls. Interestingly, Mn(III) complexes have shown the ability to degrade ligno-cellulose. Mn(III) chelated by ligands such as oxalate are soluble oxidizers with a high affinity for lignin structures. Here we determined (i) the formation and decay kinetics of the Mn(III)-oxalate complexes in aqueous solution and (ii) the effects that these complexes have on intact ligno-cellulose. UV/vis spectroscopy and iodometric titrations confirmed the transient nature of Mn(III)-oxalate complexes with decay rates being in the order of hours. Zinnia elegans tracheary elements - a model ligno-cellulose substrate - were treated with Mn(III)-oxalate complexes in a newly developed flow-through reactor. Soluble decomposition products released during the treatment were analyzed by GC/MS and the degree of cell integrity was measured by cell counts, pre- and post-treatment counts indicate a decrease in intact Zinnia elegans as a result of Mn(III)-treatment. GC/MS results showed the release of a multitude of solubilized lignin breakdown products from plant cell walls. We conclude that Mn(III)-oxalate complexes have the ability to lyse intact plant cells and solubilize lignin. Lignin decomposition may thus be seen as resource dependent, with Mn(III) a powerful resource that should be abundant in terrestrial characterized by frequent redox fluctuations.

  19. Effectiveness of Urban Shelter-in-Place. III: Commercial Districts

    SciTech Connect

    Chan, Wanyu R.; Chan, Wanyu R.; Nazaroff, William W.; Price, Phillip N.; Gadgil, Ashok J.

    2007-12-28

    In the event of a toxic chemical release to the atmosphere, shelter-in-place (SIP) is an emergency response option available to protect public health. This paper is the last in a three-part series that examines the effectiveness of SIP at reducing adverse health effects in communities. We model a hypothetical chemical release in an urban area, and consider SIP effectiveness in protecting occupants of commercial buildings. Building air infiltration rates are predicted from empirical data using an existing model. We consider the distribution of building air infiltration rates both with mechanical ventilation systems turned off and with the systems operating. We also consider the effects of chemical sorption to indoor surfaces and nonlinear chemical dose-response relationships. We find that commercial buildings provide effective shelter when ventilation systems are off, but that any delay in turning off ventilation systems can greatly reduce SIP effectiveness. Using a two-zone model, we find that there can be substantial benefit by taking shelter in the inner parts of a building that do not experience direct air exchange with the outdoors. Air infiltration rates vary substantially among buildings and this variation is important in quantifying effectiveness for emergency response. Community-wide health metrics, introduced in the previous papers in this series, can be applied in pre-event planning and to guide real-time emergency response.

  20. Failure mode and effects analysis: too little for too much?

    PubMed

    Dean Franklin, Bryony; Shebl, Nada Atef; Barber, Nick

    2012-07-01

    Failure mode and effects analysis (FMEA) is a structured prospective risk assessment method that is widely used within healthcare. FMEA involves a multidisciplinary team mapping out a high-risk process of care, identifying the failures that can occur, and then characterising each of these in terms of probability of occurrence, severity of effects and detectability, to give a risk priority number used to identify failures most in need of attention. One might assume that such a widely used tool would have an established evidence base. This paper considers whether or not this is the case, examining the evidence for the reliability and validity of its outputs, the mathematical principles behind the calculation of a risk prioirty number, and variation in how it is used in practice. We also consider the likely advantages of this approach, together with the disadvantages in terms of the healthcare professionals' time involved. We conclude that although FMEA is popular and many published studies have reported its use within healthcare, there is little evidence to support its use for the quantitative prioritisation of process failures. It lacks both reliability and validity, and is very time consuming. We would not recommend its use as a quantitative technique to prioritise, promote or study patient safety interventions. However, the stage of FMEA involving multidisciplinary mapping process seems valuable and work is now needed to identify the best way of converting this into plans for action. PMID:22447819

  1. Antidiabetic Effect and Mode of Action of Cytopiloyne

    PubMed Central

    Chang, Cicero Lee-Tian; Liu, Hsien-Yueh; Kuo, Tien-Fen; Hsu, Yi-Jou; Shen, Ming-Yi; Pan, Chien-Yuan

    2013-01-01

    Cytopiloyne was identified as a novel polyacetylenic compound. However, its antidiabetic properties are poorly understood. The aim of the present study was to investigate the anti-diabetic effect and mode of action of cytopiloyne on type 2 diabetes (T2D). We first evaluated the therapeutic effect of cytopiloyne on T2D in db/db mice. We found that one dose of cytopiloyne reduced postprandial glucose levels while increasing blood insulin levels. Accordingly, long-term treatment with cytopiloyne reduced postprandial blood glucose levels, increased blood insulin, improved glucose tolerance, suppressed the level of glycosylated hemoglobin A1c (HbA1c), and protected pancreatic islets in db/db mice. Next, we studied the anti-diabetic mechanism of action of cytopiloyne. We showed that cytopiloyne failed to decrease blood glucose in streptozocin- (STZ-)treated mice whose β cells were already destroyed. Additionally, cytopiloyne dose dependently increased insulin secretion and expression in β cells. The increase of insulin secretion/expression of cytopiloyne was regulated by protein kinase Cα (PKCα) and its activators, calcium, and diacylglycerol (DAG). Overall, our data suggest that cytopiloyne treats T2D via regulation of insulin production involving the calcium/DAG/PKCα cascade in β cells. These data thus identify the molecular mechanism of action of cytopiloyne and prove its therapeutic potential in T2D. PMID:23573144

  2. Finite Larmor radius effects on the coupled trapped electron and ion temperature gradient modes

    SciTech Connect

    Sandberg, I.; Isliker, H.; Pavlenko, V. P.

    2007-09-15

    The properties of the coupled trapped electron and toroidal ion temperature gradient modes are investigated using the standard reactive fluid model and taking rigorously into account the effects attributed to the ion polarization drift and to the drifts associated with the lowest-order finite ion Larmor radius effects. In the flat density regime, where the coupling between the modes is relatively weak, the properties of the unstable modes are slightly modified through these effects. For the peak density regions, where the coupling of the modes is rather strong, these second-order drifts determine the spectra of the unstable modes near the marginal conditions.

  3. Flare loop radiative hydrodynamics. III - Nonlocal radiative transfer effects

    NASA Technical Reports Server (NTRS)

    Canfield, R. C.; Fisher, G. H.; Mcclymont, A. N.

    1983-01-01

    The study has three goals. The first is to demonstrate that processes exist whose intrinsic nonlocal nature cannot be represented by local approximations. The second is to elucidate the physical nature and origins of these nonlocal processes. The third is to suggest that the methods and results described here may prove useful in constructing semiempirical models of the chromosphere by means more efficient than trial and error. Matrices are computed that describe the effect of a temperature perturbation at an arbitrary point in the loop on density, hydrogen ionized fraction, total radiative loss rate, and radiative loss rate of selected hydrogen lines and continua at all other points. It is found that the dominant nonlocal radiative transfer effects can be separated into flux divergence coefficient effects and upper level population effects. The former are most important when the perturbation takes place in a region of significant opacity. Upper level population effects arise in both optically thick and thin regions in response to nonlocal density, ionization, and interlocking effects.

  4. Mixed Mode Effects in a Community College Graduate Survey.

    ERIC Educational Resources Information Center

    Goho, James

    This paper describes the results of research evaluating the use of mixed-mode surveys in institutional research. Surveys were administered to 1999-2000 graduates at Red River Community College in 2 phases. Phase 1 offered three modes of response: mail, Web-based, and touch-tone data entry (TDE). Phase 2 (administered to non-respondents of Phase 1)…

  5. Pulsatile Support Mode of BJUT-II Ventricular Assist Device (VAD) has Better Hemodynamic Effects on the Aorta than Constant Speed Mode: A Primary Numerical Study

    PubMed Central

    Gu, Kaiyun; Gao, Bin; Chang, Yu; Zeng, Yi

    2016-01-01

    Background BJUT-II VAD is a novel left ventricular assist device (LVADs), directly implanted into the ascending aorta. The pulsatile support mode is proposed to achieve better unloading performance than constant speed mode. However, the hemodynamic effects of this support mode on the aorta are still unclear. The aim of this study was to clarify the hemodynamic effects BJUT-II VAD under pulsatile support mode on the aorta. Material/Methods Computational fluid dynamics (CFD) studies, based on a patient-specific aortic geometric model, were conducted. Wall shear stress (WSS), averaged WSS (avWSS), oscillatory shear index (OSI), and averaged helicity density (Ha) were calculated to compare the differences in hemodynamic effects between pulsatile support mode and constant speed mode. Results The results show that avWSS under pulsatile support mode is significantly higher than that under constant speed mode (0.955Pa vs. 0.675Pa). Similarly, the OSI value under pulsatile mode is higher than that under constant speed mode (0.104 vs. 0.057). In addition, Ha under pulsatile mode for all selected cross-sections is larger than that under constant mode. Conclusions BJUT-II VAD, under pulsatile control mode, may prevent atherosclerosis lesions and aortic remodeling. The precise effects of pulsatile support mode on atherosclerosis and aortic remodeling need to be further studied in animal experiments. PMID:27363758

  6. Pulsatile Support Mode of BJUT-II Ventricular Assist Device (VAD) has Better Hemodynamic Effects on the Aorta than Constant Speed Mode: A Primary Numerical Study.

    PubMed

    Gu, Kaiyun; Gao, Bin; Chang, Yu; Zeng, Yi

    2016-01-01

    BACKGROUND BJUT-II VAD is a novel left ventricular assist device (LVADs), directly implanted into the ascending aorta. The pulsatile support mode is proposed to achieve better unloading performance than constant speed mode. However, the hemodynamic effects of this support mode on the aorta are still unclear. The aim of this study was to clarify the hemodynamic effects BJUT-II VAD under pulsatile support mode on the aorta. MATERIAL AND METHODS Computational fluid dynamics (CFD) studies, based on a patient-specific aortic geometric model, were conducted. Wall shear stress (WSS), averaged WSS (avWSS), oscillatory shear index (OSI), and averaged helicity density (Ha) were calculated to compare the differences in hemodynamic effects between pulsatile support mode and constant speed mode. RESULTS The results show that avWSS under pulsatile support mode is significantly higher than that under constant speed mode (0.955Pa vs. 0.675Pa). Similarly, the OSI value under pulsatile mode is higher than that under constant speed mode (0.104 vs. 0.057). In addition, Ha under pulsatile mode for all selected cross-sections is larger than that under constant mode. CONCLUSIONS BJUT-II VAD, under pulsatile control mode, may prevent atherosclerosis lesions and aortic remodeling. The precise effects of pulsatile support mode on atherosclerosis and aortic remodeling need to be further studied in animal experiments. PMID:27363758

  7. Constructing an effective prevention mechanism for MSW lifecycle using failure mode and effects analysis.

    PubMed

    Chen, Ying-Chu; Wu, Wen-Fang

    2015-12-01

    Municipal solid waste in Taiwan is a valuable source of renewable energy. Phases of municipal solid waste lifecycle (classification, disposal, storage, collection and transportation) before incineration or landfilled face various potential failures. Applying a proper technique to eliminate or decrease potential failures is desirable and needed. Failure Modes and Effects Analysis to municipal solid waste lifecycle was found in literature. This study utilized the Failure Modes and Effects Analysis as a convenient technique for determining, classifying and analyzing common failures in the municipal solid waste lifecycle. As a result, an appropriate risk scoring of severity, occurrence, and detection of failure modes and computing the Risk Priority Number for identifying the high potential failure modes were made. Nineteen failure modes were identified, and nine of them were ranked as the priority items for improvement. Recommended actions for all failure modes were suggested. Occurrences of failures were remarkably reduced after implementing the procedure for six months. The results of this study have minimized potential failures and brought continuous improvement, thus achieving a better protection of the environment. PMID:26372404

  8. Computer Communication Modes and Their Effect on Student Attitudes Towards Programming.

    ERIC Educational Resources Information Center

    Boillot, Michel

    The effect of different communicating modes to computers on students' attitudes toward programing was studied. In a computer-related course, 13 students used batch processing mode to solve problems on the computer, while 12 other students used conversational mode to solve the same problems. It was found that those students accessing the computer…

  9. REVIEWS OF THE ENVIRONMENTAL EFFECTS OF POLLUTANTS: III. CHROMIUM

    EPA Science Inventory

    The report is a review of the scientific literature on the biological and environmental effects of chromium. Included in the review are a general summary and a comprehensive discussion of the following topics as related to chromium and specific chromium compounds: physical and ch...

  10. Chunking Method of Teaching and Studying (III): Test Effects.

    ERIC Educational Resources Information Center

    Furukawa, James M.; Cohen, Nancy

    The effects of specific testing procedures on learning were studied, using the chunking method of teaching and studying, which involves the learning of small units of information. The size of the unit is related to the student's cognitive processing capacity (CPC)--the amount of material recalled after a brief exposure. Subjects were undergraduate…

  11. Effect of chirality on domain wall dynamics in molecular ferrimagnet [MnII(HL-pn)(H2O)][MnIII(CN)6]·2H2O

    NASA Astrophysics Data System (ADS)

    Mushenok, F.; Koplak, O.; Morgunov, R.

    2011-11-01

    In this paper we distinguish the contributions of switching, slide, creep and Debye relaxation modes of the domain wall dynamics to the low-frequency magnetic properties of chiral and racemic [MnII(HL-pn)(H2O)][MnIII(CN)6]·2H2O molecular ferrimagnets. We demonstrate that crystal and spin chirality affects the characteristic transition temperatures between different modes. In chiral crystals, transitions to the creep and Debye relaxation modes were observed at T = 7 K and 5 K, whereas in racemic crystals the same transitions occurred at higher temperatures T = 13 K and 9 K, respectively. Difference of the Peierls relief in chiral and racemic crystals is a possible reason of the chirality effect on the domain walls dynamics.

  12. Exponential synchronization of coupled switched neural networks with mode-dependent impulsive effects.

    PubMed

    Wenbing Zhang; Yang Tang; Qingying Miao; Wei Du

    2013-08-01

    This paper investigates the synchronization problem of coupled switched neural networks (SNNs) with mode-dependent impulsive effects and time delays. The main feature of mode-dependent impulsive effects is that impulsive effects can exist not only at the instants coinciding with mode switching but also at the instants when there is no system switching. The impulses considered here include those that suppress synchronization or enhance synchronization. Based on switching analysis techniques and the comparison principle, the exponential synchronization criteria are derived for coupled delayed SNNs with mode-dependent impulsive effects. Finally, simulations are provided to illustrate the effectiveness of the results. PMID:24808570

  13. Effective band structure of random III-V alloys

    NASA Astrophysics Data System (ADS)

    Popescu, Voicu; Zunger, Alex

    2010-03-01

    Random substitutional alloys have no long range order (LRO) or translational symmetry so rigorously speaking they have no E(k) band structure or manifestations thereof. Yet, many experiments on alloys are interpreted using the language of band theory, e.g. inferring Van Hove singularities, band dispersion and effective masses. Many standard alloy theories (VCA- or CPA-based) have the LRO imposed on the alloy Hamiltonian, assuming only on-site disorder, so they can not be used to judge the extent of LRO that really exists. We adopt the opposite way, by using large (thousand atom) randomly generated supercells in which chemically identical alloy atoms are allowed to have different local environments (a polymorphous representation). This then drives site-dependent atomic relaxation as well as potential fluctuations. The eigenstates from such supercells are then mapped onto the Brillouin zone (BZ) of the primitive cell, producing effective band dispersion. Results for (In,Ga)X show band-like behaviour only near the centre and faces of the BZ but rapidly lose such characteristics away from γ or for higher bands. We further analyse the effects of stoichiometry variation, internal relaxation, and short-range order on the alloy band structure.

  14. FMEA, the alternative process hazard method. [Failure Mode Effects Analysis

    SciTech Connect

    Goyal, R.K. )

    1993-05-01

    Failure mode effects analysis (FMEA) is an old reliability/assurance tool finding its way into the HPI. Not popular yet, this hazard technique has some viable applications that can improve hazard assessment data. Notably, FMEA studies can identify possible areas for improvement that may have not been discovered using other methods. Also, FMEA is not as labor intensive and costly as other process hazard analysis (PHA) methods. PSHA 1910.119 set in place an informational structure whose main purpose is the reduction of potential accidents and minimizing risks in the event of an accident. Consequently, HPI operators must evaluate their process systems and identify potential major hazards, such as fires, explosions and accidental release of toxic/hazardous chemicals, and protect their facilities, employees, the public and the environment. But, which PHA method(s) apply to a particular plant or process still remains a difficult question. This paper describes what FMEA is; types of FMEA; how to conduct a FMEA study; comparison with HAZOP (hazard and operability study); computer software; applicability of FMEA; and examples of its use.

  15. The Worker Exposure Failure Modes and Effects Analysis

    SciTech Connect

    Cadwallader, L.C.

    2005-05-15

    The Worker Exposure Failure Modes and Effects Analysis (WE-FMEA) is a new approach to quantitatively evaluate worker risks from possible failures of co-located equipment in the complex environment of a magnetic or inertial fusion experiment. For next-step experiments such as the International Thermonuclear Experimental Reactor (ITER) or the National Ignition Facility (NIF), the systems and equipment will be larger, handle more throughput or power, and will, in general, be more robust than past experiments. These systems and equipment are necessary to operate the machine, but the rooms are congested with equipment, piping, and cables, which poses a new level of hazard for workers who will perform hands-on maintenance. The WE-FMEA systematically analyzes the nearby equipment and the work environment for equipment failure or inherent hazards, and then develops exposure scenarios. Once identified, the exposure scenarios are evaluated for the worker hazards and quantitative worker risk is calculated. Then risk scenarios are quantitatively compared to existing statistical data on worker injuries; high-risk scenarios can be identified and addressed in more detail to determine the proper means to reduce, mitigate, or protect against the hazard. The WE-FMEA approach is described and a cooling system maintenance example is given.

  16. THE EFFECTS OF CURRENT FLOW ON BIOELECTRIC POTENTIAL : III. NITELLA.

    PubMed

    Blinks, L R

    1936-11-20

    String galvanometer records show the effect of current flow upon the bioelectric potential of Nitella cells. Three classes of effects are distinguished. 1. Counter E.M.F'S, due either to static or polarization capacity, probably the latter. These account for the high effective resistance of the cells. They record as symmetrical charge and discharge curves, which are similar for currents passing inward or outward across the protoplasm, and increase in magnitude with increasing current density. The normal positive bioelectric potential may be increased by inward currents some 100 or 200 mv., or to a total of 300 to 400 mv. The regular decrease with outward current flow is much less (40 to 50 mv.) since larger outward currents produce the next characteristic effect. 2. Stimulation. This occurs with outward currents of a density which varies somewhat from cell to cell, but is often between 1 and 2 microa/cm.(2) of cell surface. At this threshold a regular counter E.M.F. starts to develop but passes over with an inflection into a rapid decrease or even disappearance of positive P.D., in a sigmoid curve with a cusp near its apex. If the current is stopped early in the curve regular depolarization occurs, but if continued a little longer beyond the first inflection, stimulation goes on to completion even though the current is then stopped. This is the "action current" or negative variation which is self propagated down the cell. During the most profound depression of P.D. in stimulation, current flow produces little or no counter E.M.F., the resistance of the cell being purely ohmic and very low. Then as the P.D. begins to recover, after a second or two, counter E.M.F. also reappears, both becoming nearly normal in 10 or 15 seconds. The threshold for further stimulation remains enhanced for some time, successively larger current densities being needed to stimulate after each action current. The recovery process is also powerful enough to occur even though the original

  17. Photophysical effects of metal-carbon sigma bonds in ortho-metalated complexes of Ir(III) and Rh(III)

    SciTech Connect

    Sprouse, S.; King, K.A.; Spellane, P.J.; Watts, R.J.

    1984-10-31

    Dichloro-bridged dimers of the type (M(L)/sub 2/Cl)/sub 2/, where L is 2-phenylpyridine (ppy) or benzo(h)quinoline (bzq) and M is Rh(III) or Ir(III), have been characterized by /sup 13/C and /sup 1/H NMR spectroscopies and by absorption and emission spectroscopies. The NMR results confirm previous formulations of the complexes as dichloro-bridged ortho-metalated dimers in halocarbon solvents but indicate that they are cleaved to monomeric species of the type M(L)/sub 2/CIS in ligating solvents such as dimethylformamide (S = solvent). The absorption spectra of each of the complexes contain several low-energy bands which are assigned as metal-to-ligand charge-transfer (MLCT) transitions. All four of the dimers emit light following photoexcitation of their glassy solutions at 77 K. Their emission spectra and lifetimes lead to assignments of their emitting states as intraligand for the Rh(III) dimers and MLCT for the Ir(III) dimers. The Ir(III) dimers are also found to emit light following excitation at 295 K in deaerated dichloromethane. No emission is seen from the Rh(III) dimers under these conditions. Comparison of these results with previous results from studies of similar Rh(III) and Ir(III) complexes of 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen) indicates that the ortho-metalated ligands are considerably higher than bpy and phen in the spectrochemical series. In addition to raising the energy of ligand field excited states in their complexes, relative to similar bpy and phen species, they induce lower energy charge-transfer transitions. These effects are consistent with the synergistic function of the ortho-metalated ligands as both strong sigma donors and ..pi.. acceptors.

  18. Selective Recovery of Chromium from Precipitates Containing d Elements and Actinides: III. Effect of S2O8 2-

    SciTech Connect

    Fedoseev, A. M.; Shilov, V. P.; Budantseva, N. A.; Yusov, A. B.; Delegard, Calvin H.

    2002-07-15

    The interaction of Cr(III) hydroxides and mixed Fe(III)-Cr(III) and Ni(II)-Cr(III) hydroxides with persulfate ions has been investigated in alkaline media by a spectrophotometric method. The stoichiometric yield of Cr(VI) corresponds to a molar ratio of S2O82-:Cr(III) close to 1.5. The initial rate of the reaction is described by the equation d[Cr(III)]/dt = k[Cr(III)][S2O82-][NaOH]. The activation energy in the range 41.5-95?C is 53 kJ/mole. The V0 value is higher than the rate of thermal decomposition of persulfate; i.e. Cr(III) hydroxide reacts directly with S2O82-. The oxidation of NiCr2O4?nH2O and mixed Fe(III)-Cr(III) hydroxides proceeds faster than oxidation of pure Cr(III) hydroxide. The acceleration is explained by the catalytic effect of Fe(III) and Ni(II). Additions of Co(II) and Cu(II) also accelerate the oxidation. Pu(IV) in alkaline media is oxidized to higher more soluble states by persulfate but may be reduced by the action of appropriate reducing agents.

  19. Collisionless microtearing modes in hot tokamaks: Effect of trapped electrons

    SciTech Connect

    Swamy, Aditya K.; Ganesh, R.; Brunner, S.; Vaclavik, J.; Villard, L.

    2015-07-15

    Collisionless microtearing modes have recently been found linearly unstable in sharp temperature gradient regions of large aspect ratio tokamaks. The magnetic drift resonance of passing electrons has been found to be sufficient to destabilise these modes above a threshold plasma β. A global gyrokinetic study, including both passing electrons as well as trapped electrons, shows that the non-adiabatic contribution of the trapped electrons provides a resonant destabilization, especially at large toroidal mode numbers, for a given aspect ratio. The global 2D mode structures show important changes to the destabilising electrostatic potential. The β threshold for the onset of the instability is found to be generally downshifted by the inclusion of trapped electrons. A scan in the aspect ratio of the tokamak configuration, from medium to large but finite values, clearly indicates a significant destabilizing contribution from trapped electrons at small aspect ratio, with a diminishing role at larger aspect ratios.

  20. The effect of magnetopause motion on fast mode resonance

    NASA Astrophysics Data System (ADS)

    Hartinger, M. D.; Welling, D.; Viall, N. M.; Moldwin, M. B.; Ridley, A.

    2014-10-01

    The Earth's magnetosphere supports several types of ultralow frequency (ULF) waves. These include fast mode resonance (FMR): cavity modes, waveguide modes, and tunneling modes/virtual resonance. The magnetopause, often treated as the outer boundary for cavity/waveguide modes in the dayside magnetosphere, is not stationary. A rapidly changing outer boundary condition—e.g., due to rapid magnetopause motion—is not favorable for FMR generation and may explain the sparseness of FMR observations in the outer magnetosphere. We examine how magnetopause motion affects the dayside magnetosphere's ability to sustain FMR with idealized Space Weather Modeling Framework (SWMF) simulations using the BATS-R-US global magnetohydrodynamic (MHD) code coupled with the Ridley Ionosphere Model (RIM). We present observations of FMR in BATS-R-US, reproducing results from other global MHD codes. We further show that FMR is present for a wide range of solar wind conditions, even during periods with large and rapid magnetopause displacements. We compare our simulation results to FMR observations in the dayside magnetosphere, finding that FMR occurrence does not depend on solar wind dynamic pressure, which can be used as a proxy for dynamic pressure fluctuations and magnetopause perturbations. Our results demonstrate that other explanations besides a nonstationary magnetopause—such as the inability to detect FMR in the presence of other ULF wave modes with large amplitudes—are required to explain the rarity of FMR observations in the outer magnetosphere.

  1. Effect of material perception on mode of color appearance.

    PubMed

    Kuriki, Ichiro

    2015-01-01

    The mode of color appearance (mode) is a concept suggesting that variations in a medium that emits, transmits, or reflects light can cause differences in color appearance. For example, the same light beams that appear brown (or gray) when reflected from a given object surface may appear orange (or white) when emitted from a light source. The present study investigated the relationships between material perception and perceived mode, especially in terms of luminosity. In the experiment, a rotating spheroid was presented with surrounds of various luminance levels. The surface texture of the spheroid was either matte gray (three surface reflectance levels) or one of two fabrics. The participants were asked to evaluate the luminosity (mode) and perceived reflectance of the object. The results show that the mode perception is clearly different from the lightness perception. The luminosity was fit with a linear function of the lightness scale in CIE (Commission Internationale de l'Éclairage) L* value of the object surface, unless the material of the surface was identifiable. To conclude, the luminosity (mode) perception can be strongly affected by the material percept, and the luminosity perception of the same object can vary when its surface property is ambiguous. PMID:26057547

  2. Effects of PECS Phase III Application Training on Independent Mands in Young Children with Autism

    ERIC Educational Resources Information Center

    Love, Jessica June

    2013-01-01

    The purpose of this study was to examine the effects of PECS phase III application training on independent mands in young children with autism. Participants were five children with autism ranging from ages 2 to 4 years old. A multiple baseline across participants was used to evaluate acquisition of independent correct mands across baseline and…

  3. The competitive effects of Ca(II) on Eu(III) sorption to goethite

    SciTech Connect

    Gall, E.J.; Snyder, L.I.; Bryce, A.L.

    1995-12-01

    Predictive modeling of the transport of trivalent rare earth and actinide elements in the geosphere is difficult as the mechanism of lanthanide sorption in natural systems is not well understood. Experimental data demonstrating rare earth sorption to soil components under environmentally realistic conditions is lacking. In this presentation, we report on the competitive effects of the presence of a major cation, Ca(II), on the sorption of Eu(III) to goethite. pH sorption edges and isotherms will be presented for both of these elements. Variables considered are ionic strength as well as Ca(II) and Eu(III) concentrations. Finally, mechanisms of lanthanide sorption will be discussed.

  4. Oxygen effect in the radiolysis of proteins. III. Haemoglobin.

    PubMed

    Puchała, M; Schuessler, H

    1993-08-01

    Radiolysis of haemoglobin was carried out in phosphate buffer under air, N2 or N2O and with and without ethanol. Radiation products were separated by SDS-PAGE. The loss of subunits and simultaneous aggregation and fragmentation of haemoglobin was measured, if OH-radicals were unscavenged. There was no sensitizing effect of oxygen on the degradation process. Radiation-induced fragmentation was not a random process, but produced specific fragments. The estimated molecular weights of these fragments gave further support to the assumption that the aminoacyl-proline peptide group is the preferential breaking site if OH radicals react with proteins in the presence of oxygen. In contrast with lactate dehydrogenase and bovine serum albumin such fragmentation was observed not only after aerobic radiolysis but also under anaerobic conditions. This difference must be caused by the Feporphyrin system which reacts with H2O2 under release of oxygen. If haemoglobin was irradiated under air the yield of aggregates was much lower than under N2O or N2. PMID:8103537

  5. Influence of retrieval mode on effects of production: Evidence for costs in free recall.

    PubMed

    Mama, Yaniv; Icht, Michal

    2016-06-01

    Study modality (visual, auditory) of words as well as production mode (reading aloud, writing down) have been shown to influence the production effect (PE). When study words are presented visually, reading them aloud yields superior memory. However, when the same study words are presented aurally, writing them down leads to superior memory. Missing in PE studies is the variable of retrieval mode (written, aloud), which was addressed in the present study. In a pair of experiments, we manipulated the 3 variables-study modality, production mode, and retrieval mode-in a factorial fashion. With visual study, aloud production mode (vocalizing) was found to be superior to written production, in both retrieval modes (written and aloud). However, the difference between the productions was significantly smaller in the aloud retrieval mode relative to the written retrieval mode. With auditory study, written production mode was superior to aloud production mode, in the written as well as in the aloud retrieval modes. Here, the difference between the productions was significantly smaller in the written relative to the aloud retrieval mode. In other words, the difference between productions was smaller for the retrieval mode that matched the superior production. We interpret these findings using a retrieval-cost account. (PsycINFO Database Record PMID:27244359

  6. Effects of travel mode on exposures to particulate air pollution.

    PubMed

    Briggs, David J; de Hoogh, Kees; Morris, Chloe; Gulliver, John

    2008-01-01

    Monitoring was carried out of particulate concentrations whilst simultaneously walking and driving 48 routes in London, UK. Monitoring was undertaken during May and June 2005. Route lengths ranged from 601 to 1351 m, and most routes were travelled in both directions. Individual journey times ranged from 1.5 to 15 min by car (average 3.7 min) and 7.3 to 30 min (average 12.8 min) whilst walking; car trips were therefore repeated up to 5 times for each single walking trip and the results averaged for the route. Car trips were made with windows closed and the ventilation system on a moderate setting. Results show that mean exposures while walking are greatly in excess of those while driving, by a factor 4.7 for the coarse particle mass (PM10-PM2.5), 2.2 for the fine particle mass (PM2.5-PM1), 1.9 for the very fine particle mass (mode from car to walking in response to policies aimed at encouraging a modal shift in travel behavior are thus likely to experience considerably increased journey-time personal exposures to traffic-related air pollution. More effort is consequently needed to increase separation between road vehicles and pedestrians if negative effects of these policies are to be avoided. PMID:17688949

  7. Effects of Fe(III) and organic matter additions on methanogenic activity and Fe(III) reduction in boreal lake and wetland sediments

    NASA Astrophysics Data System (ADS)

    Karvinen, Anu; Lehtinen, Lotta; Kankaala, Paula

    2013-04-01

    We studied potential methane production and Fe(III) reduction activity in lake sediments and wetland peat sampled from 14 sites in southern and eastern Finland. The concentration of total iron in the sediments and peat varied between 0.5 and 1200 ppm and their organic matter content (loss of ignition) varied between 1-98% of dry weight. Also the effects of added amorphous Fe(III) oxyhydroxide and organic matter (ammoniumacetate and/or sodiumacetate) on methanogenic and Fe(III) reduction activities were studied in anaerobic laboratory incubations (in vitro) lasting 5-20 days at 15 °C in darkness. Potential methane production and the effects of iron and acetate additions were highly variable between lake and peatland sites. The highest methanogenic potential was generally measured in productive littoral sites, especially in those dominated by Phragmites australis vegetation stands. In these sediments the total iron concentrations were high and acetate additions clearly increased methane production whereas Fe(III) additions decreased it. Our results demonstrate that microbial Fe(III) reduction plays an important role in the anaerobic organic matter decomposition in many boreal lakes.

  8. Mixed-mode fracture of ceramics

    SciTech Connect

    Petrovic, J.J.

    1985-01-01

    The mixed-mode fracture behavior of ceramic materials is of importance for monolithic ceramics in order to predict the onset of fracture under generalized loading conditions and for ceramic composites to describe crack deflection toughening mechanisms. Experimental data on surface flaw mixed-mode fracture in various ceramics indicate that the flaw-plane normal stress at fracture decreases with increasing in-flaw-plane shear stress, although present data exhibit a fairly wide range in details of this sigma - tau relationship. Fracture from large cracks suggests that Mode II has a greater effect on Mode I fracture than Mode III. A comparison of surface flaw and large crack mixed-mode I-II fracture responses indicated that surface flaw behavior is influenced by shear resistance effects.

  9. Alpha-particle effects on ballooning flute modes in tokamaks

    SciTech Connect

    Andrushchenko, Z.N.; Bijko, A.Y.; Cheremnykh, O.K. )

    1990-11-01

    In this paper a more accurate dispersion equation for ideal ballooning flute modes in a plasma with alpha particles is obtained. It is shown that circulating and trapped alpha particles generate the eigenbranches of the mode oscillations with frequencies {omega} {approx lt} {omega}{sub *i}, where {omega}{sub *i}, is the ion drift frequency. The relevant growth rates and frequencies are found. It is ascertained that in the frequency range {omega}{sub *i} {lt} {omega} {lt} {bar {omega}{sub Db}}, where {bar {omega}{sub Db}} is the magnetic drift frequency average over a bounce period, trapped alpha particles may generate forced oscillations that influence the ideal ballooning flute mode stability boundary. It is shown that the stability may be improved for certain plasma parameters and trapped alpha-particle pressures.

  10. EFFECTS OF A DEEP MIXED SHELL ON SOLAR g-MODES, p-MODES, AND NEUTRINO FLUX

    SciTech Connect

    Wolff, Charles L.

    2009-08-10

    A mixed-shell model that reflects g-modes away from the Sun's center is developed further by calibrating its parameters and evaluating a mixing mechanism: buoyancy. The shell roughly doubles g-mode oscillation periods and would explain why there is no definitive detection of their periods. But the shell has only minor effects on most p-modes. The model provides a mechanism for causing short-term fluctuations in neutrino flux and makes plausible the correlations between this flux and solar activity levels. Relations are derived for a shell heated asymmetrically by transient increases in nuclear burning in small 'hot spots'. The size of these spots and the timing of a heating event are governed by sets(l) of standing asymptotic g-modes, coupled by a maximal principle that greatly enhances their excitation and concentrates power toward the equator, assisting the detection of higher-l sets. Signals from all sets, except one, in the range 2 {<=} l {<=} 8 are identified by difference periods between consecutive radial states using the method of Garcia et al. and reinterpreting their latest spectrum. This confirms two detections of sets in a similar range of l by their rotation rates. The mean radius of shell mixing is r{sub m} = 0.16 R{sub sun}, which improves an earlier independent estimate of 0.18 by the author. The shell may cause the unexplained dip in measured sound speed at its location. Another sound speed error, centered near 0.67 R{sub sun}, and reversing flows in the same place with a period originally near 1.3 yr suggest that the g-modes are depositing there about 3% of the solar luminosity. That implies the shell at r{sub m} is receiving a similar magnitude of power, which would be enough energy to mix the corresponding shell in a standard solar model in <<10{sup 7} yr.

  11. Strain-effect transistors: Theoretical study on the effects of external strain on III-nitride high-electron-mobility transistors on flexible substrates

    SciTech Connect

    Shervin, Shahab; Asadirad, Mojtaba; Kim, Seung-Hwan; Ravipati, Srikanth; Lee, Keon-Hwa; Bulashevich, Kirill; Ryou, Jae-Hyun

    2015-11-09

    This paper presents strain-effect transistors (SETs) based on flexible III-nitride high-electron-mobility transistors (HEMTs) through theoretical calculations. We show that the electronic band structures of InAlGaN/GaN thin-film heterostructures on flexible substrates can be modified by external bending with a high degree of freedom using polarization properties of the polar semiconductor materials. Transfer characteristics of the HEMT devices, including threshold voltage and transconductance, are controlled by varied external strain. Equilibrium 2-dimensional electron gas (2DEG) is enhanced with applied tensile strain by bending the flexible structure with the concave-side down (bend-down condition). 2DEG density is reduced and eventually depleted with increasing compressive strain in bend-up conditions. The operation mode of different HEMT structures changes from depletion- to enchantment-mode or vice versa depending on the type and magnitude of external strain. The results suggest that the operation modes and transfer characteristics of HEMTs can be engineered with an optimum external bending strain applied in the device structure, which is expected to be beneficial for both radio frequency and switching applications. In addition, we show that drain currents of transistors based on flexible InAlGaN/GaN can be modulated only by external strain without applying electric field in the gate. The channel conductivity modulation that is obtained by only external strain proposes an extended functional device, gate-free SETs, which can be used in electro-mechanical applications.

  12. Strain-effect transistors: Theoretical study on the effects of external strain on III-nitride high-electron-mobility transistors on flexible substrates

    NASA Astrophysics Data System (ADS)

    Shervin, Shahab; Kim, Seung-Hwan; Asadirad, Mojtaba; Ravipati, Srikanth; Lee, Keon-Hwa; Bulashevich, Kirill; Ryou, Jae-Hyun

    2015-11-01

    This paper presents strain-effect transistors (SETs) based on flexible III-nitride high-electron-mobility transistors (HEMTs) through theoretical calculations. We show that the electronic band structures of InAlGaN/GaN thin-film heterostructures on flexible substrates can be modified by external bending with a high degree of freedom using polarization properties of the polar semiconductor materials. Transfer characteristics of the HEMT devices, including threshold voltage and transconductance, are controlled by varied external strain. Equilibrium 2-dimensional electron gas (2DEG) is enhanced with applied tensile strain by bending the flexible structure with the concave-side down (bend-down condition). 2DEG density is reduced and eventually depleted with increasing compressive strain in bend-up conditions. The operation mode of different HEMT structures changes from depletion- to enchantment-mode or vice versa depending on the type and magnitude of external strain. The results suggest that the operation modes and transfer characteristics of HEMTs can be engineered with an optimum external bending strain applied in the device structure, which is expected to be beneficial for both radio frequency and switching applications. In addition, we show that drain currents of transistors based on flexible InAlGaN/GaN can be modulated only by external strain without applying electric field in the gate. The channel conductivity modulation that is obtained by only external strain proposes an extended functional device, gate-free SETs, which can be used in electro-mechanical applications.

  13. Coherence Effects of Caroli-de Gennes-Matricon Modes in Nodal Topological Superconductors

    NASA Astrophysics Data System (ADS)

    Tsutsumi, Yasumasa; Kato, Yusuke

    2016-05-01

    Coherence effects by the impurity scattering of Caroli-de Gennes-Matricon (CdGM) modes in a vortex for nodal topological superconductors have been studied. The coherence effects reflect a topological number defined on a particular momentum space avoiding the superconducting gap nodes. First, we analytically derived the eigenvalue and eigenfunction of the CdGM modes, including the zero-energy modes, in a nodal topological superconducting state without impurities, where we focused on a possible superconducting state of UPt3 as an example. Then, we studied impurity effects on the CdGM modes by introducing the impurity self-energy, which are dominated by the coherence factor depending on the eigenfunction of the CdGM modes. For the zero-energy CdGM modes, the coherence factor vanishes in a certain momentum range, which is guaranteed by topological invariance characterized by the one-dimensional winding number.

  14. Increasing Facilitator Effectiveness by Bridging Two Modes of Consciousness.

    ERIC Educational Resources Information Center

    Alperson, Erma Dosamantes

    To fully explore the range of our human consciousness, we must have access to all available modes of experiencing: the bodily-implicit and the rational-explicit. To the extent that we become alienated from our bodily-felt side, we respond solely in terms of what the external situation demands. We lose sight of our own feelings and needs and…

  15. The effect of reactor geometry on frontal polymerization spin modes

    NASA Astrophysics Data System (ADS)

    Pojman, John A.; Masere, Jonathan; Petretto, Enrico; Rustici, Mauro; Huh, Do-Sung; Kim, Min Suk; Volpert, Vladimir

    2002-03-01

    Using reactors of different sizes and geometries the dynamics of the frontal polymerization of 1,6-hexanediol diacrylate (HDDA) and pentaerythritol tetraacrylate (PETAC), with ammonium persulfate as the initiator were studied. For this system, the frontal polymerization exhibits complex behavior that depends on the ratio of the monomers. For a particular range of monomers concentration, the polymerization front becomes nonplanar, and spin modes appear. By varying the reactor diameter, we experimentally confirmed the expected shift of the system to a greater number of "hot spots" for larger diameters. For square test tubes a "zig-zag" mode was observed for the first time in frontal polymerization. We confirmed the viscosity-dependence of the spin mode instabilities. We also observed novel modes in cylinder-inside-cylinder reactors. Lastly, using a conical reactor with a continuously varying diameter, we observed what may be evidence for bistability depending on the direction of propagation. We discuss these finding in terms of the standard linear stability analysis for propagating fronts.

  16. Failure mode and effects analysis outputs: are they valid?

    PubMed Central

    2012-01-01

    Background Failure Mode and Effects Analysis (FMEA) is a prospective risk assessment tool that has been widely used within the aerospace and automotive industries and has been utilised within healthcare since the early 1990s. The aim of this study was to explore the validity of FMEA outputs within a hospital setting in the United Kingdom. Methods Two multidisciplinary teams each conducted an FMEA for the use of vancomycin and gentamicin. Four different validity tests were conducted: · Face validity: by comparing the FMEA participants’ mapped processes with observational work. · Content validity: by presenting the FMEA findings to other healthcare professionals. · Criterion validity: by comparing the FMEA findings with data reported on the trust’s incident report database. · Construct validity: by exploring the relevant mathematical theories involved in calculating the FMEA risk priority number. Results Face validity was positive as the researcher documented the same processes of care as mapped by the FMEA participants. However, other healthcare professionals identified potential failures missed by the FMEA teams. Furthermore, the FMEA groups failed to include failures related to omitted doses; yet these were the failures most commonly reported in the trust’s incident database. Calculating the RPN by multiplying severity, probability and detectability scores was deemed invalid because it is based on calculations that breach the mathematical properties of the scales used. Conclusion There are significant methodological challenges in validating FMEA. It is a useful tool to aid multidisciplinary groups in mapping and understanding a process of care; however, the results of our study cast doubt on its validity. FMEA teams are likely to need different sources of information, besides their personal experience and knowledge, to identify potential failures. As for FMEA’s methodology for scoring failures, there were discrepancies between the teams’ estimates

  17. Effects of Composition Mode and Self-Perceived Computer Skills on Essay Scores of Sixth Graders

    ERIC Educational Resources Information Center

    Burke, Jennifer N.; Cizek, Gregory J.

    2006-01-01

    This study was conducted to gather evidence regarding effects of the mode of writing (handwritten vs. word-processed) on compositional quality in a sample of sixth grade students. Questionnaire data and essay scores were gathered to examine the effect of composition mode on essay scores of students of differing computer skill levels. The study was…

  18. Refractive index sensing characteristic of single-mode-multimode-single-mode fiber structure based on self-imaging effect

    NASA Astrophysics Data System (ADS)

    Bai, Xuekun; Wang, Haotian; Wang, Shaofei; Pu, Shengli; Zeng, Xianglong

    2015-10-01

    We research the refractive index (RI) sensing characteristic based on the bandpass spectrum caused by the self-imaging effect in the single-mode-multimode-single-mode (SMS) fiber structure theoretically and experimentally. A new selectable parameter, i.e., no-core fiber (NCF) length, is investigated for improving the sensitivity of the sensor. The results show that the sensor's sensitivity will be enhanced by shortening the NCF length when the self-imaging number remains constant. Experimentally, a maximum sensitivity of 1923 nm/RIU (RI unit) has been achieved when the RI ranges from 1.334 to 1.434. This work demonstrates a method to improve the sensitivity of SMS-fiber-structure-based RI sensors featuring a low cost, compact size, low insert loss, and high sensitivity optical fiber RI sensor.

  19. Phosphorylation by PKA and Cdk5 Mediates the Early Effects of Synapsin III in Neuronal Morphological Maturation.

    PubMed

    Piccini, Alessandra; Perlini, Laura E; Cancedda, Laura; Benfenati, Fabio; Giovedì, Silvia

    2015-09-23

    central role in early stages of neuronal development involving neuronal survival, polarization, and neuritic growth and that these effects are dependent on phosphorylation by cAMP-dependent protein kinase and cyclin-dependent protein kinase-5. These results explain the recently described neurodevelopmental defects in the migration and orientation of Synapsin III-depleted cortical neurons and support the potential association of Synapsin III with neurodevelopmental disorders such as schizophrenia. PMID:26400944

  20. Effect of tris(3-hydroxy-4-pyridinonate) iron(III) complexes on iron uptake and storage in soybean (Glycine max L.).

    PubMed

    Santos, Carla S; Carvalho, Susana M P; Leite, Andreia; Moniz, Tânia; Roriz, Mariana; Rangel, António O S S; Rangel, Maria; Vasconcelos, Marta W

    2016-09-01

    Iron deficiency chlorosis (IDC) is a serious environmental problem affecting the growth of several crops in the world. The application of synthetic Fe(III) chelates is still one of the most common measures to correct IDC and the search for more effective Fe chelates remains an important issue. Herein, we propose a tris(3-hydroxy-4-pyridinonate) iron(III) complex, Fe(mpp)3, as an IDC corrector. Different morphological, biochemical and molecular parameters were assessed as a first step towards understanding its mode of action, compared with that of the commercial fertilizer FeEDDHA. Plants treated with the pyridinone iron(III) complexes were significantly greener and had increased biomass. The total Fe content was measured using ICP-OES and plants treated with pyridinone complexes accumulated about 50% more Fe than those treated with the commercial chelate. In particular, plants supplied with compound Fe(mpp)3 were able to translocate iron from the roots to the shoots and did not elicit the expression of the Fe-stress related genes FRO2 and IRT1. These results suggest that 3,4-HPO iron(III) chelates could be a potential new class of plant fertilizing agents. PMID:27156133

  1. Effect of Deformation Mode on the Wear Behavior of NiTi Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Yan, Lina; Liu, Yong

    2016-06-01

    Owing to good biocompatibility, good fatigue resistance, and excellent superelasticity, various types of bio-medical devices based on NiTi shape memory alloy (SMA) have been developed. Due to the complexity in deformation mode in service, for example NiTi implants, accurate assessment/prediction of the surface wear process is difficult. This study aims at providing a further insight into the effect of deformation mode on the wear behavior of NiTi SMA. In the present study, two types of wear testing modes were used, namely sliding wear mode and reciprocating wear mode, to investigate the effect of deformation mode on the wear behavior of NiTi SMA in both martensitic and austenitic states. It was found that, when in martensitic state and under high applied loads, sliding wear mode resulted in more surface damage as compared to that under reciprocating wear mode. When in austenitic state, although similar trends in the coefficient of friction were observed, the coefficient of friction and surface damage in general is less under reciprocating mode than under sliding mode. These observations were further discussed in terms of different deformation mechanisms involved in the wear tests, in particular, the reversibility of martensite variant reorientation and stress-induced phase transformation, respectively.

  2. Effect of Deformation Mode on the Wear Behavior of NiTi Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Yan, Lina; Liu, Yong

    2016-05-01

    Owing to good biocompatibility, good fatigue resistance, and excellent superelasticity, various types of bio-medical devices based on NiTi shape memory alloy (SMA) have been developed. Due to the complexity in deformation mode in service, for example NiTi implants, accurate assessment/prediction of the surface wear process is difficult. This study aims at providing a further insight into the effect of deformation mode on the wear behavior of NiTi SMA. In the present study, two types of wear testing modes were used, namely sliding wear mode and reciprocating wear mode, to investigate the effect of deformation mode on the wear behavior of NiTi SMA in both martensitic and austenitic states. It was found that, when in martensitic state and under high applied loads, sliding wear mode resulted in more surface damage as compared to that under reciprocating wear mode. When in austenitic state, although similar trends in the coefficient of friction were observed, the coefficient of friction and surface damage in general is less under reciprocating mode than under sliding mode. These observations were further discussed in terms of different deformation mechanisms involved in the wear tests, in particular, the reversibility of martensite variant reorientation and stress-induced phase transformation, respectively.

  3. Anharmonicity effects in the frictionlike mode of graphite

    NASA Astrophysics Data System (ADS)

    Menéndez, C.; Lobato, A.; Abbasi-Pérez, D.; Fernández-Núñez, J.; Baonza, V. G.; Recio, J. M.

    2016-04-01

    Graphite is a prototypical solid lubricant demanding a thorough understanding of its low-friction behavior. The E2 g(1) Raman active vibrational mode of graphite is associated with the rigid-layer relative movement of its graphene sheets. Thus, this mode can provide a good means of exploring the low resistance of graphene layers to slip with respect to each other. To take advantage of this fact, the anharmonicity of the E2 g(1) mode has to be carefully characterized and evaluated since the atomic arrangement of carbon atoms in the ambient condition ABA stacking of graphite evidences potential asymmetry. The calculated one-dimensional energetic profile of the E2 g(1) mode reveals this local anisotropy around the energy minima and can be microscopically interpreted in terms of electron density interactions. Morse-type potentials accurately fit the energetic profiles at different interlayer separations, and provide simple analytical expressions for evaluating harmonic and anharmonic contributions to the Γ -point E2 g(1) frequency ωE2g(1 ) under a perturbative algebraic treatment. We quantify how the anharmonic contribution increases with the available energy (E ) at zero pressure, and how this contribution decreases as hydrostatic pressure (p ) or uniaxial stress is applied for a given available energy. The calculated ωE2g(1 )-p and ωE2g(1 )-E trends indicate an increasing (decreasing) of frictional forces in graphite with pressure (temperature). Our conclusions are supported by the good agreement of the calculated frequencies with existing Raman experiments under hydrostatic pressure conditions.

  4. Quantum cascade emission in the III-nitride material system designed with effective interface grading

    SciTech Connect

    Song, Alex Y. Huang, Tzu-Yung; Zah, Chung-En; Gmachl, Claire F.; Bhat, Rajaram; Wang, Jie; Allerman, Andrew A.

    2015-09-28

    We report the realization of quantum cascade (QC) light emission in the III-nitride material system, designed with effective interface grading (EIG). EIG induces a continuous transition between wells and barriers in the quantum confinement, which alters the eigenstate system and even delocalizes the states with higher energy. Fully transverse-magnetic spontaneous emission is observed from the fabricated III-nitride QC structure, with a center wavelength of ∼4.9 μm and a full width at half maximum of ∼110 meV, both in excellent agreement with theoretical predictions. A multi-peak photo-response spectrum is also measured from the QC structure, which again agrees well with theoretical calculations and verifies the effects of EIG.

  5. Gd(III) complexes for electron-electron dipolar spectroscopy: Effects of deuteration, pH and zero field splitting.

    PubMed

    Garbuio, Luca; Zimmermann, Kaspar; Häussinger, Daniel; Yulikov, Maxim

    2015-10-01

    Spectral parameters of Gd(III) complexes are intimately linked to the performance of the Gd(III)-nitroxide or Gd(III)-Gd(III) double electron-electron resonance (DEER or PELDOR) techniques, as well as to that of relaxation induced dipolar modulation enhancement (RIDME) spectroscopy with Gd(III) ions. These techniques are of interest for applications in structural biology, since they can selectively detect site-to-site distances in biomolecules or biomolecular complexes in the nanometer range. Here we report relaxation properties, echo detected EPR spectra, as well as the magnitude of the echo reduction effect in Gd(III)-nitroxide DEER for a series of Gadolinium(III) complexes with chelating agents derived from tetraazacyclododecane. We observed that solvent deuteration does not only lengthen the relaxation times of Gd(III) centers but also weakens the DEER echo reduction effect. Both of these phenomena lead to an improved signal-to-noise ratios or, alternatively, longer accessible distance range in pulse EPR measurements. The presented data enrich the knowledge on paramagnetic Gd(III) chelate complexes in frozen solutions, and can help optimize the experimental conditions for most types of the pulse measurements of the electron-electron dipolar interactions. PMID:26342680

  6. Gd(III) complexes for electron-electron dipolar spectroscopy: Effects of deuteration, pH and zero field splitting

    NASA Astrophysics Data System (ADS)

    Garbuio, Luca; Zimmermann, Kaspar; Häussinger, Daniel; Yulikov, Maxim

    2015-10-01

    Spectral parameters of Gd(III) complexes are intimately linked to the performance of the Gd(III)-nitroxide or Gd(III)-Gd(III) double electron-electron resonance (DEER or PELDOR) techniques, as well as to that of relaxation induced dipolar modulation enhancement (RIDME) spectroscopy with Gd(III) ions. These techniques are of interest for applications in structural biology, since they can selectively detect site-to-site distances in biomolecules or biomolecular complexes in the nanometer range. Here we report relaxation properties, echo detected EPR spectra, as well as the magnitude of the echo reduction effect in Gd(III)-nitroxide DEER for a series of Gadolinium(III) complexes with chelating agents derived from tetraazacyclododecane. We observed that solvent deuteration does not only lengthen the relaxation times of Gd(III) centers but also weakens the DEER echo reduction effect. Both of these phenomena lead to an improved signal-to-noise ratios or, alternatively, longer accessible distance range in pulse EPR measurements. The presented data enrich the knowledge on paramagnetic Gd(III) chelate complexes in frozen solutions, and can help optimize the experimental conditions for most types of the pulse measurements of the electron-electron dipolar interactions.

  7. Effect of substrate discontinuities on the propagating surface plasmon polariton modes in gold nanobars

    NASA Astrophysics Data System (ADS)

    Johns, Paul; Yu, Kuai; Devadas, Mary Sajini; Li, Zhongming; Major, Todd A.; Hartland, Gregory V.

    2014-11-01

    The surface plasmon polariton (SPP) modes of gold nanobars (nanowires with rectangular dimensions) have been investigated by scanning pump-probe microscopy. In these experiments the nanobars were suspended over trenches cut in glass coverslips, and propagating SPP modes were launched in the supported portion of the nanobar by focusing a near-IR pump laser beam at the end of the nanobar. Transient absorption images were then collected by scanning the probe laser over the nanobar using a galvo-mirror system. The images show that the trench has a large effect on the SPP modes, specifically, for approximately half the nanowires the propagation length is significantly reduced after the trench. Finite element calculations were performed to understand this effect. The calculations show that the pump laser excites bound and leaky modes (modes that have their fields localized at the nanobar/glass or nanobar/air interfaces, respectively) in the supported portions of the nanobars. These modes propagate along the nanobar. When they meet the trench their field distributions are altered. The modes that derive from the bound mode are strongly damped over the trench. Thus, the bound mode is not reconstituted on the opposite side of the trench, and only the leaky mode contributes to the signal. Because the bound and leaky modes can have different propagation lengths, the propagation lengths measured in our experiments can change from one side of the trench to the other. The results show how the substrate can be engineered to control the SPP modes in metal nanostructures.The surface plasmon polariton (SPP) modes of gold nanobars (nanowires with rectangular dimensions) have been investigated by scanning pump-probe microscopy. In these experiments the nanobars were suspended over trenches cut in glass coverslips, and propagating SPP modes were launched in the supported portion of the nanobar by focusing a near-IR pump laser beam at the end of the nanobar. Transient absorption images

  8. 75 FR 11530 - Crystal Lake Wind III, LLC, et al.; Notice of Effectiveness of Exempt Wholesale Generator Status

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-11

    ... Energy Regulatory Commission Crystal Lake Wind III, LLC, et al.; Notice of Effectiveness of Exempt Wholesale Generator Status March 4, 2010. Docket Nos. Crystal Lake Wind III, LLC EG10-6-000 GardenGarden Wind, LLC EG10-7-000 Star Point Wind Project LLC EG10-8-000 Nacogdoches Power, LLC EG10-9-000...

  9. The Effect of Plasma Shape on H-Mode Pedestal Characteristics on DIII-D

    SciTech Connect

    T.H. Osborne; J.R. Ferron; R.J. Groebner; L.L. Lao; A.W. Leonard; R. Maingi; R.L. Miller; A.D. Turnbull; M.R. Wade; J.G. Watkins

    1999-12-01

    The characteristics of the H-mode are studied in discharges with varying triangularity and squareness. The pressure at the top of the H-mode pedestal increases strongly with triangularity primarily due to an increase in the margin by which the edge pressure gradient exceeds the ideal ballooning mode first stability limit. Two models are considered for how the edge may exceed the ballooning mode limit. In one model [1], access to the ballooning mode second stable regime allows the edge pressure gradient and associated bootstrap current to continue to increase until an edge localized, low toroidal mode number, ideal kink mode is destabilized. In the second model [2], the finite width of the H-mode transport barrier, and diamagnetic effects raise the pressure gradient limit above the ballooning mode limit. We observe a weak inverse dependence of the width of the H-mode transport barrier, {Delta}, on triangularity relative to the previously obtained [3] scaling {Delta} {infinity} ({beta}{sub P}{sup PED}){sup 1/2}. The energy loss for Type I ELMs increases with triangularity in proportion to the pedestal energy increase. The temperature profile is found to respond stiffly to changes in T{sup PED} at low temperature, while at high temperature the response is additive. The response of the density profile is also found to play a role in the response of the total stored energy to changes in the W{sup PED}.

  10. Curvature effect on tearing modes in presence of neoclassical friction

    SciTech Connect

    Maget, Patrick; Mellet, Nicolas; Meshcheriakov, Dmytro; Garbet, Xavier; Lütjens, Hinrich

    2013-11-15

    Neoclassical physics (here associated to the poloidal variation of the magnetic field strength along field lines in a tokamak) is well known for driving self-generated plasma current and nonlinear magnetic islands associated to it in high performance, ITER relevant plasma discharges. It is demonstrated that the neoclassical friction between a magnetic perturbation and plasma flow already impacts magnetic islands in the linear regime, by inducing a weakening of curvature stabilization for tearing modes. This conclusion holds in particular for regimes where convection is influencing the pressure dynamics, as shown using a simple analytical model and confirmed in full Magneto-Hydro-Dynamics simulations.

  11. A destabilizing effect of rotation shear on magnetohydrodynamic ballooning modes

    SciTech Connect

    Connor, J. W.; Hastie, R. J.; Webster, A. J.

    2007-04-15

    The destabilization of ideal magnetohydrodynamic ballooning modes at finite rotation shear is demonstrated for the model s-{alpha} equilibrium by exploiting low magnetic shear, s, to simplify the two-dimensional stability problem to a one-dimensional eigenvalue problem. This simpler calculation captures the same features as exhibited by a full two-dimensional treatment, namely that stable values in the s-{alpha} stability diagram become unstable above a critical rotation shear. The first and second stability boundaries at low s are calculated as functions of rotation shear.

  12. Finite Larmor radius effects on the (m = 2, n = 1) cylindrical tearing mode

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Chowdhury, J.; Parker, S. E.; Wan, W.

    2015-04-01

    New field solvers are developed in the gyrokinetic code GEM [Chen and Parker, J. Comput. Phys. 220, 839 (2007)] to simulate low-n modes. A novel discretization is developed for the ion polarization term in the gyrokinetic vorticity equation. An eigenmode analysis with finite Larmor radius effects is developed to study the linear resistive tearing mode. The mode growth rate is shown to scale with resistivity as γ ˜ η1/3, the same as the semi-collisional regime in previous kinetic treatments [Drake and Lee, Phys. Fluids 20, 1341 (1977)]. Tearing mode simulations with gyrokinetic ions are verified with the eigenmode calculation.

  13. Global particle-in-cell simulations of plasma pressure effects on Alfvenic modes

    SciTech Connect

    Mishchenko, Alexey; Koenies, Axel; Hatzky, Roman

    2011-01-15

    Global linear gyrokinetic particle-in-cell simulations of electromagnetic modes in realistic tokamak geometry are reported. The effect of plasma pressure on Alfvenic modes is studied. It is shown that the fast-particle pressure can considerably affect the shear Alfven wave continuum structure and hence the toroidicity-induced gap in the continuum. It is also found that the energetic ions can substantially reduce the growth rate of the ballooning modes (and perhaps completely stabilize them in a certain parameter range). Ballooning modes are found to be the dominant instabilities if the bulk-plasma pressure gradient is large enough.

  14. A study of the relative effectiveness and cost of computerized information retrieval in the interactive mode

    NASA Technical Reports Server (NTRS)

    Smetana, F. O.; Furniss, M. A.; Potter, T. R.

    1974-01-01

    Results of a number of experiments to illuminate the relative effectiveness and costs of computerized information retrieval in the interactive mode are reported. It was found that for equal time spent in preparing the search strategy, the batch and interactive modes gave approximately equal recall and relevance. The interactive mode however encourages the searcher to devote more time to the task and therefore usually yields improved output. Engineering costs as a result are higher in this mode. Estimates of associated hardware costs also indicate that operation in this mode is more expensive. Skilled RECON users like the rapid feedback and additional features offered by this mode if they are not constrained by considerations of cost.

  15. Effect of toroidal magnetic field on n = 1 mode stability in rotamak plasmas

    SciTech Connect

    Yang, X.; Goss, J.; Kalaria, D.; Huang, T. S.

    2011-08-15

    To study the effect of toroidal magnetic field on n = 1 mode stability, a series of experiments with linearly ramping the axial current I{sub z}, which makes field-reversed configuration (FRC) to spherical tokamak (ST) transition, have been conducted in rotamak. Results clearly demonstrate that the tilt mode can be completely suppressed by small I{sub z} around 0.4 kA (in comparison with 2.0 kA plasma current). An unknown new mode with larger magnetic perturbations is triggered when I{sub z} reaches 0.5 kA. This instability mode keeps saturation while plasma current is boosted when I{sub z} is in the range of 0.6-1.4 kA. When I{sub z} exceeds 1.6 kA, the new mode suddenly disappears and discharge is free from instability modes.

  16. The effect of lanthanum(III) and cerium(III) ions between layers of manganese oxide on water oxidation.

    PubMed

    Najafpour, Mohammad Mahdi; Isaloo, Mohsen Abbasi; Hołyńska, Małgorzata; Shen, Jian-Ren; Allakhverdiev, Suleyman I; Allakhverdiev, Suleyman

    2015-12-01

    Manganese oxide structure with lanthanum(III) or cerium(III) ions between the layers was synthesized by a simple method. The ratio of Mn to Ce or La in samples was 0.00, 0.04, 0.08, 0.16, 0.32, 0.5, 0.82, or 1.62. The compounds were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction studies, and atomic absorption spectroscopy. The compounds show efficient catalytic activity of water oxidation in the presence of cerium(IV) ammonium nitrate with a turnover frequency of 1.6 mmol O2/mol Mn.s. In contrast to the water-oxidizing complex in Photosystem II, calcium(II) has no specific role to enhance the water-oxidizing activity of the layered manganese oxides and other cations can be replaced without any significant decrease in water-oxidizing activities of these layered Mn oxides. Based on this and previously reported results from oxygen evolution in the presence of H 2 (18) O, we discuss the mechanism and the important factors influencing the water-oxidizing activities of the manganese oxides. PMID:25701552

  17. Effect of Pulse Duration on Polytetrafluoroethylene Shocked above the Crystalline Phase II-Iii Transition

    NASA Astrophysics Data System (ADS)

    Brown, E. N.; Gray, G. T.; Rae, P. J.; Trujillo, C. P.; Bourne, N. K.

    2007-12-01

    We present an experimental study of crystalline structure evolution of polytetrafluoroethylene (PTFE) due to pressure-induced phase transitions in a semi-crystalline polymer using soft-recovery, shock-loading techniques coupled with mechanical and chemical post-shock analysis. Gas-launched, plate impact experiments have been performed on pedigreed PTFE 7C, mounted in momentum-trapped, shock assemblies, with impact pressures above and below the phase II to phase III crystalline transition. Below the phase transition only subtle changes were observed in the crystallinity, microstructure, and mechanical response of PTFE. Shock loading of PTFE 7C above the phase II-III transition was seen to cause both an increase in crystallinity from 38% to ˜53% and a finer crystalline microstructure, and changed the yield and flow stress behavior. We particularly focus on the effect of pulse duration on the microstructure evolution.

  18. Shock Pulse Effects in PTFE Shocked Through the Crystalline Phase II--III Transition

    NASA Astrophysics Data System (ADS)

    Brown, Eric N.; Gray, George T., III; Rae, Philip J.; Bourne, Neil K.

    2008-03-01

    We present an experimental study of crystalline structure evolution of polytetrafluoroethylene (PTFE) due to pressure-induced phase transitions in a semi-crystalline polymer using soft-recovery, shock-loading techniques coupled with mechanical and chemical post-shock analysis. Gas-launched, plate impact experiments have been performed on pedigreed PTFE 7C, mounted in momentum-trapped, shock assemblies, with impact pressures above and below the phase II to phase III crystalline transition. Below the phase transition only subtle changes were observed in the crystallinity, microstructure, and mechanical response of PTFE. Shock loading of PTFE 7C above the phase II--III transition was seen to cause both an increase in crystallinity from 38% to ˜53% (by Differential Scanning Calorimetry, DSC) and a finer crystalline microstructure, and changed the yield and flow stress behavior. We particularly focus on the effect of pulse duration on the microstructure evolution.

  19. Effect of Pulse Duration on Polytetrafluoroethylene Shocked Above the Crystalline Phase II--III Transition

    NASA Astrophysics Data System (ADS)

    Brown, Eric N.; Gray, George T., III; Rae, Philip J.; Trujillo, Carl P.; Bourne, Neil K.

    2007-06-01

    We present an experimental study of crystalline structure evolution of polytetrafluoroethylene (PTFE) due to pressure-induced phase transitions in a semi-crystalline polymer using soft-recovery, shock-loading techniques coupled with mechanical and chemical post-shock analysis. Gas-launched, plate impact experiments have been performed on pedigreed PTFE 7C, mounted in momentum-trapped, shock assemblies, with impact pressures above and below the phase II to phase III crystalline transition. Below the phase transition only subtle changes were observed in the crystallinity, microstructure, and mechanical response of PTFE. Shock loading of PTFE 7C above the phase II--III transition was seen to cause both an increase in crystallinity from 38% to ˜53% (by Differential Scanning Calorimetry, DSC) and a finer crystalline microstructure, and changed the yield and flow stress behavior. We particularly focus on the effect of pulse duration on the microstructure evolution.

  20. Effect of substrate discontinuities on the propagating surface plasmon polariton modes in gold nanobars.

    PubMed

    Johns, Paul; Yu, Kuai; Devadas, Mary Sajini; Li, Zhongming; Major, Todd A; Hartland, Gregory V

    2014-11-01

    The surface plasmon polariton (SPP) modes of gold nanobars (nanowires with rectangular dimensions) have been investigated by scanning pump-probe microscopy. In these experiments the nanobars were suspended over trenches cut in glass coverslips, and propagating SPP modes were launched in the supported portion of the nanobar by focusing a near-IR pump laser beam at the end of the nanobar. Transient absorption images were then collected by scanning the probe laser over the nanobar using a galvo-mirror system. The images show that the trench has a large effect on the SPP modes, specifically, for approximately half the nanowires the propagation length is significantly reduced after the trench. Finite element calculations were performed to understand this effect. The calculations show that the pump laser excites bound and leaky modes (modes that have their fields localized at the nanobar/glass or nanobar/air interfaces, respectively) in the supported portions of the nanobars. These modes propagate along the nanobar. When they meet the trench their field distributions are altered. The modes that derive from the bound mode are strongly damped over the trench. Thus, the bound mode is not reconstituted on the opposite side of the trench, and only the leaky mode contributes to the signal. Because the bound and leaky modes can have different propagation lengths, the propagation lengths measured in our experiments can change from one side of the trench to the other. The results show how the substrate can be engineered to control the SPP modes in metal nanostructures. PMID:25321926

  1. Anion Effects on Lanthanide(III) Tetrazole-1-acetate Dinuclear Complexes Showing Slow Magnetic Relaxation and Photofluorescent Emission.

    PubMed

    Lu, Ying-Bing; Jiang, Xiao-Ming; Zhu, Shui-Dong; Du, Zi-Yi; Liu, Cai-Ming; Xie, Yong-Rong; Liu, Liang-Xian

    2016-04-18

    Three types of lanthanide complexes based on the tetrazole-1-acetic acid ligand and the 2,2'-bipyridine coligand were prepared and characterized by single-crystal X-ray diffraction, IR spectroscopy, and elemental analyses; the formulas of these complexes are [Ln2(1-tza)4(NO3)2(2,2'-bipy)2] (Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5)), [Dy2(1-tza)4Cl2(2,2'-bipy)2] (6), and [Yb2(1-tza)4(NO3)2(2,2'-bipy)2] (7) (1-tza = tetrazole-1-acetate and 2,2'-bipy = 2,2'-bipyridine). They are dinuclear complexes possessing similar structures but different lanthanide(III) ion coordination geometries because of the distinction of peripheral anions (such as NO3(-) and Cl(-)) and the effect of lanthanide contraction. The variable-temperature magnetic susceptibilities of 1-6 were measured. Both Dy(III) complexes (5 and 6) display field-induced single-molecule magnet behaviors. Ab initio calculations revealed that the Dy(III) complex 6 possesses a more anisotropic Dy(III) ion in comparison to that in 5. The room-temperature photoluminescence spectra of Sm(III) (1), Eu(III) (2), Tb(III) (4), and Dy(III) (5 and 6) complexes exhibit strong characteristic emissions in the visible region, whereas the Yb(III) (7) complex shows near-infrared (NIR) luminescence. PMID:27023680

  2. Neoclassical effects on the stabilization of tearing mode by current modulation

    SciTech Connect

    Yang, Xiaoqing Wang, Shaojie; Yang, Weihong

    2014-02-15

    The neoclassical effects on the stabilization of tearing modes by current modulation have been investigated. Neoclassical effects enhance the resistivity and reduce the resistive diffusion time of the modulation current. Therefore, the oscillating current can penetrate deeper into the plasma. With an oscillating loop voltage, the plasma oscillates radially at the Ware-pinch velocity. These neoclassical effects improve the efficiency of tearing mode stabilization by the current modulation.

  3. Effect of density gradients in confined supersonic shear layers. Part 2: 3-D modes

    NASA Technical Reports Server (NTRS)

    Peroomian, Oshin; Kelly, R. E.

    1994-01-01

    The effect of basic flow density gradients on the supersonic wall modes were investigated in Part 1 of this analysis. In that investigation only the 2-D modes were studied. Tam and Hu investigated the 3-D modes in a confined vortex sheet and reported that the first 2-D Class A mode (A01) had the highest growth rate compared to all other 2-D and 3-D modes present in the vortex sheet for that particular set of flow patterns. They also showed that this result also held true for finite thickness shear layers with delta(sub w) less than 0.125. For free shear layers, Sandham and Reynolds showed that the 3-D K-H mode became the dominant mode for M(sub c) greater than 0.6. Jackson and Grosch investigated the effect of crossflow and obliqueness on the slow and fast odes present in a M(sub c) greater than 1 environment and showed that for certain combination of crossflow and wave angles the growth rates could be increased by up to a factor of 2 with respect to the 2-D case. The case studied here is a confined shear layer shown in Part 1. All solution procedures and basic low profiles are the same as in Part 1. The effect of density gradients on the 3-D modes present in the density ratios considered in Part 1 are investigated.

  4. The gallium(III)-salicylidene acylhydrazide complex shows synergistic anti-biofilm effect and inhibits toxin production by Pseudomonas aeruginosa.

    PubMed

    Rzhepishevska, Olena; Hakobyan, Shoghik; Ekstrand-Hammarström, Barbro; Nygren, Yvonne; Karlsson, Torbjörn; Bucht, Anders; Elofsson, Mikael; Boily, Jean-François; Ramstedt, Madeleine

    2014-09-01

    Bacterial biofilms cause a range of problems in many areas and especially in health care. Biofilms are difficult to eradicate with traditional antibiotics and consequently there is a need for alternative ways to prevent and/or remove bacterial biofilms. Furthermore, the emergence of antibiotic resistance in bacteria creates a challenge to find new types of antibiotics with a lower evolutionary pressure for resistance development. One route to develop such drugs is to target the so called virulence factors, i.e. bacterial systems used when bacteria infect a host cell. This study investigates synergy effects between Ga(III) ions, previously reported to suppress biofilm formation and growth in bacteria, and salicylidene acylhydrazides (hydrazones) that have been proposed as antivirulence drugs targeting the type three secretion system used by several Gram-negative pathogens, including Pseudomonas aerugionosa, during bacterial infection of host cells. A library of hydrazones was screened for: Fe(III) binding, enhanced anti-biofilm effect with Ga(III) on P. aeruginosa, and low cytotoxicity to mammalian cells. The metal coordination for the most promising ligand, 2-Oxo-2-[N-(2,4,6-trihydroxy-benzylidene)-hydrazino]-acetamide (ME0163) with Ga(III) was investigated using extended X-ray absorption fine structure spectroscopy as well as density functional theory. The results showed that Ga(III) chelates the hydrazone with 5- and 6-membered chelating rings, and that the Ga(III)-ME0163 complex enhanced the antibiofilm effect of Ga(III) while suppressing the type three secretion system in P. aeruginosa. The latter effect was not observed for the hydrazone alone and was similar for Ga(III)-citrate and Ga(III)-ME0163 complexes, indicating that the inhibition of virulence was caused by Ga(III). PMID:24837331

  5. Mass effect of redox reactions: A novel mode for surface plasmon resonance-based bioanalysis.

    PubMed

    Yuan, Pei-Xin; Deng, Sheng-Yuan; Xin, Peng; Ji, Xu-Bo; Shan, Dan; Cosnier, Serge

    2015-12-15

    The pursuit of more specific and sensitive response is a perpetual goal for modern bioassays. This work proposed a novel label-free strategy about redox-related mass effect based on the surface plasmon resonance (SPR) technique for ultrasensitive determination of DNA. The protocol starts with the modification of SPR gilded disk with the capture DNA (cDNA). After the conjugation of immobilized cDNA with the target DNA (tDNA), the hybridization chain reaction was triggered by the introduction of mutual partial complementary primers to elongate the terminal into a nanoscale duplex. As it is reported that porphyrin could intercalate into the grooves of the double-stranded DNA (dsDNA) scaffold, multiple positive-charged Fe(III)meso-tetra(N-methyl-4-pyridyl) porphine (FeTMPyP) with symmetric structure were uptaken for in situ formation of porphyrin-dsDNA complex. Given FeTMPyP a highly efficient catalysis for the peroxide reduction, its presence as a biomimetic cofactor was validated via circular dichroism and UV-vis spectroscopy, demonstrating a tight binding as well as high catalytic activity and stability. Using 4-chloro-1-naphthol as a proton donor, the catalytic reduction of H2O2 would oxidize it into insoluble benzo-4-chloro-hexadienone, which simultaneously deposited on the heterogeneous interface, leading to a significant amplification in both SPR response and topological height profile. The signal increment was proportional to the concentration of tDNA, thus an ultrasensitive SPR-based DNA assay was developed with a linear range over four orders of magnitudes and a sub-femtomolar detection limit of 0.73 fM. The developed methodology exemplifies a different way of thinking about mass-sensing modes, extending conventional SPR-based DNA analysis to relevant biomedical applications. PMID:26141105

  6. Effect of Pressure Anisotropy on Relativistic Slow-Mode Shocks

    NASA Astrophysics Data System (ADS)

    Tenbarge, Jason; Hazeltine, Richard; Mahajan, Swadesh

    2009-11-01

    Shock mediated reconnection is a possible source for the high-energy non-thermal emissions observed in astrophysical systems such as pulsars and magnetars, gamma-ray bursts, and active galactic nuclei. In such strongly magnetized environments, strong gyrotropic anisotropy in the pressure is expected to occur due to synchrotron emission and various instabilities. A newly developed covariant fluid modelfootnotetextJ. M. TenBarge, R. D. Hazeltine, and S. M. Mahajan, Phys. Plasmas 15, 062112 (2008). for magnetized plasmas, incorporating pressure anisotropy but neglecting heat flow, is used to study Petschek type reconnection in a pair plasma governed by slow-mode shocks. The plasma parameters are found to be strongly modified by anisotropy on both sides of the shock.

  7. Matrix resin effects in composite delamination - Mode I fracture aspects

    NASA Technical Reports Server (NTRS)

    Hunston, Donald L.; Moulton, Richard J.; Johnston, Norman J.; Bascom, Willard D.

    1987-01-01

    A number of thermoset, toughened thermoset, and thermoplastic resin matrix systems were characterized for Mode I critical strain energy release rates, and their composites were tested for interlaminar critical strain energy release rates using the double cantilever beam method. A clear correlation is found between the two sets of data. With brittle resins, the interlaminar critical strain energy release rates are somewhat larger than the neat resin values due to a full transfer of the neat resin toughness to the composite and toughening mechanisms associated with crack growth. With tougher matrices, the higher critical strain energy release rates are only partially transferred to the composites, presumably because the fibers restrict the crack-tip deformation zones.

  8. Failure modes and effects analysis of fusion magnet systems

    SciTech Connect

    Zimmermann, M; Kazimi, M S; Siu, N O; Thome, R J

    1988-12-01

    A failure modes and consequence analysis of fusion magnet system is an important contributor towards enhancing the design by improving the reliability and reducing the risk associated with the operation of magnet systems. In the first part of this study, a failure mode analysis of a superconducting magnet system is performed. Building on the functional breakdown and the fault tree analysis of the Toroidal Field (TF) coils of the Next European Torus (NET), several subsystem levels are added and an overview of potential sources of failures in a magnet system is provided. The failure analysis is extended to the Poloidal Field (PF) magnet system. Furthermore, an extensive analysis of interactions within the fusion device caused by the operation of the PF magnets is presented in the form of an Interaction Matrix. A number of these interactions may have significant consequences for the TF magnet system particularly interactions triggered by electrical failures in the PF magnet system. In the second part of this study, two basic categories of electrical failures in the PF magnet system are examined: short circuits between the terminals of external PF coils, and faults with a constant voltage applied at external PF coil terminals. An electromagnetic model of the Compact Ignition Tokamak (CIT) is used to examine the mechanical load conditions for the PF and the TF coils resulting from these fault scenarios. It is found that shorts do not pose large threats to the PF coils. Also, the type of plasma disruption has little impact on the net forces on the PF and the TF coils. 39 refs., 30 figs., 12 tabs.

  9. Linear and nonlinear effect of sheared plasma flow on resistive tearing modes

    SciTech Connect

    Hu, Qiming Hu, Xiwei; Yu, Q.

    2014-12-15

    The effect of sheared plasma flow on the m/n = 2/1 tearing mode is studied numerically (m and n are the poloidal and toroidal mode numbers). It is found that in the linear phase the plasma flow with a weak or moderate shear plays a stabilizing effect on tearing mode. However, the mode is driven to be more unstable by sufficiently strong sheared flow when approaching the shear Alfvén resonance (AR). In the nonlinear phase, a moderate (strong) sheared flow leads to a smaller (larger) saturated island width. The stabilization of tearing modes by moderate shear plasma flow is enhanced for a larger plasma viscosity and a lower Alfvén velocity. It is also found that in the nonlinear phase AR accelerates the plasma rotation around the 2/1 rational surface but decelerates it at the AR location, and the radial location satisfying AR spreads inwards towards the magnetic axis.

  10. The Hall dynamo effect and nonlinear mode coupling during sawtooth magnetic reconnection

    SciTech Connect

    Ding, W. X.; Brower, D. L.; Deng, B. H.; Almagri, A. F.; Craig, D.; Fiksel, G.; Mirnov, V.; Prager, S. C.; Sarff, J. S.; Svidzinski, V.

    2006-11-15

    During magnetic reconnection associated with sawtooth activity in a reversed field pinch, we observe a large fluctuation-induced Hall electromotive force, <{delta}Jx{delta}B>/n{sub e}e, which is capable of modifying the equilibrium current. This Hall dynamo effect is determined in the hot plasma core by laser Faraday rotation which measures equilibrium and fluctuating magnetic field and current density. We find that the Hall dynamo is strongest when nonlinear mode coupling between three spatial Fourier modes of the resistive tearing instability is present. Mode coupling alters the phase relation between magnetic and current density fluctuations for individual Fourier modes leading to a finite Hall effect. Detailed measurements of the spatial and temporal dynamics for the dominant core resonant mode under various plasma configurations are described providing evidence regarding the origin of the Hall dynamo.