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Sample records for c14 laves phase

  1. Hydrogen cycling induced diffraction peak broadening in C14 and C15 Laves phases

    International Nuclear Information System (INIS)

    The diffraction peak broadening induced by hydrogen absorption-desorption cycling has been analyzed in four different Laves phase compounds with the C14 and C15 structures. The broadening is due to strain most probably originating from dislocations generated at the interface between the α and β hydride phases in connection with the cell volume difference between the two phases. It has been shown that it is strongly compound dependent. In the case of the C14 structure, the broadening is large and isotropic, and the latter can be related to the isotropy of the elastic constants of the metallic phase. The broadening is less for the compounds with the C15 structure, which can be related to a possibly softer lattice. Better ageing properties after long-term cycling are predicted for this crystal structure

  2. Reaction of hydrogen with the Laves phase (C14) TiCr1.78-xMnx compounds

    International Nuclear Information System (INIS)

    The lattice constants a and c of the as cast hexagonal (C14) Laves phase TiCr1.78-xMnx (x = 0, 0.4, 0.6 and 0.8) have been measured by X-ray diffraction at room temperature as a function of the Mn content. It has been found that a decreases with increasing x while c remains almost unchanged. Being this alloy interesting as material for solid state hydrogen storage, pressure-composition isotherms have been traced on desorption mode for the H2 gas pressure and temperature varying from 10 to 0.01 MPa and from 209 to 307 K, respectively. From the temperature dependence of the plateau pressure the molar quantities ΔH-barH2 and ΔS-barH2 associated with the hydride decomposition have been determined as a function of the Mn content. With increasing x, both ΔH-barH2 and ΔS-barH2 progressively decrease, and the desorption pressure initially decreases (for x ≤ 0.4) then slightly increases. At the same time, the pseudo-plateaus become flatter.

  3. Microstructural Evolution and Compressive Properties of Two-Phase Nb-Fe Alloys Containing the C14 Laves Phase NbFe2 Intermetallic Compound

    Science.gov (United States)

    Li, K. W.; Wang, X. B.; Wang, W. X.; Li, S. M.; Gong, D. Q.; Fu, H. Z.

    2016-02-01

    Microstructural evolution and compressive properties of two-phase Nb-Fe binary alloys based on the C14 Laves phase NbFe2 were characterized at both the hypo- and hypereutectic compositions. The experimental results indicated that the microstructures of the two alloys consisted of fully eutectics containing Fe and NbFe2 phases at the bottom of the ingots corresponding to the largest solidification rates. With the decrease of solidification rate, the microstructures developed into primary Fe (NbFe2) dendrites plus eutectics in the middle and top parts of the ingots. The microstructural evolutions along the axis of the ingots were analyzed by considering the competitive growth between the primary phase and eutectic as well as using microstructure selection models based on the maximum interface temperature criterion. Furthermore, the compressive properties of the two alloys were measured and the enhancements were explained in terms of the second Fe phase and halo toughening mechanisms.

  4. Optimization of Co-content in C14 Laves phase multi-component alloys for NiMH battery application

    International Nuclear Information System (INIS)

    The structural, electrochemical, and gas phase hydrogen storage properties of predominantly C14 crystalline phase alloys with partial replacement by Co (up to 2.5 at%) are reported. Minor phases, including C15 and cubic TiNi, were found by X-ray diffraction and contributed to the improved hydrogen diffusion through the alloy. The optimal Co-content of between 1.0 and 1.5 at% provides easy activation, high gas phase capacity, and a high discharge capacity. An optimized alloy formula also provided the smallest metallic nickel cluster size embedded in the surface oxide and the largest number of nickel clusters. In sealed cell studies, a Co-content of 1.5% gives the best performance in formation, cycle life, and charge retention, but has worse specific power and low temperature performance than some other compositions. The high-rate dischargeabilities at lower rates were found to be limited by surface reactions, not bulk diffusion.

  5. Reaction of hydrogen with the Laves phase (C14) TiCr{sub 1.78-x}Mn{sub x} compounds

    Energy Technology Data Exchange (ETDEWEB)

    Agresti, F. [Universita di Padova, Dipartimento di Ingegneria Meccanica, Settore Materiali and CNISM, via Marzolo 9, 35131 Padova (Italy); Lo Russo, S. [Universita di Padova, Dipartimento di Fisica and CNISM, via Marzolo 8, 35131 Padova (Italy); Maddalena, A.; Principi, G. [Universita di Padova, Dipartimento di Ingegneria Meccanica, Settore Materiali and CNISM, via Marzolo 9, 35131 Padova (Italy); Mazzolai, G. [Universita di Perugia, Dipartimento di Fisica, Via A. Pascoli 5, 06100 Perugia (Italy); Universita Telematica e-Campus, Via Isimbardi 10, Novedrate (Colombia) (Italy); Coluzzi, B.; Biscarini, A. [Universita di Perugia, Dipartimento di Fisica, Via A. Pascoli 5, 06100 Perugia (Italy); Mazzolai, F.M., E-mail: fabio.mazzolai@fisica.unipg.it [Universita di Perugia, Dipartimento di Fisica, Via A. Pascoli 5, 06100 Perugia (Italy); Tuissi, A. [Istituto per l' Energia e le Interfasi, CNR-IENI, C.so Promessi Sposi, 29, Lecco (Italy)

    2009-09-15

    The lattice constants a and c of the as cast hexagonal (C14) Laves phase TiCr{sub 1.78-x}Mn{sub x} (x = 0, 0.4, 0.6 and 0.8) have been measured by X-ray diffraction at room temperature as a function of the Mn content. It has been found that a decreases with increasing x while c remains almost unchanged. Being this alloy interesting as material for solid state hydrogen storage, pressure-composition isotherms have been traced on desorption mode for the H{sub 2} gas pressure and temperature varying from 10 to 0.01 MPa and from 209 to 307 K, respectively. From the temperature dependence of the plateau pressure the molar quantities {Delta}H-bar{sub H{sub 2}} and {Delta}S-bar{sub H{sub 2}} associated with the hydride decomposition have been determined as a function of the Mn content. With increasing x, both {Delta}H-bar{sub H{sub 2}} and {Delta}S-bar{sub H{sub 2}} progressively decrease, and the desorption pressure initially decreases (for x {<=} 0.4) then slightly increases. At the same time, the pseudo-plateaus become flatter.

  6. Ferromagnetism in Laves-phase WFe2 nanoparticles

    OpenAIRE

    Koten, M.A. van; P. Manchanda; B. Balamurugan; Skomski, R.; Sellmyer, D. J.; Shield, J. E.

    2015-01-01

    While rare-earth based Laves phases are known to exhibit large magnetostriction, the magnetic properties of some binary Laves phases containing transition metals alone are not well known. This is because many of these compounds contain refractory elements that complicate melt processing due to high melting temperatures and extensive phase separation. Here, phase-pure WFe2 nanoclusters, with the hexagonal C14 Laves structure, were deposited via inert gas condensation, allowing for the first kn...

  7. Point Defects in Binary Laves-Phase Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Liaw, P.K.; Liu, C.T.; Pike, L.M.; Zhu, J.H.

    1998-11-30

    Point defect mechanisms in the binary C15 NbCr{sub 2} and NbCo{sub 2}, and C14 NbFe{sub 2} systems on both sides of stoichiometry was studied and clarified by both bulk density and X-ray lattice parameter measurements. It was found that the vacancy concentrations in these systems after quenching from 1000 C are essentially zero. The constitutional defects on both sides of stoichiometry for these systems were found to be of the anti-site type in comparison with the model predictions. However, thermal vacancies exhibiting a maximum at the stoichiometric composition were obtained in NbCr{sub 2} laves phase alloys after quenching from 1400 C. These could be completely eliminated by annealing at 1000 C. Anti-site hardening was found on both sides of stoichiometry for all three Laves phase systems studied. Furthermore, the thermal vacancies in NbCr{sub 2} alloys after quenching from 1400 C were found to soften the Laves phase. The anti-site hardening of the Laves phases is similar to that of the B2 compounds, while the thermal vacancy softening is unique to the Laves phase. Both the anti-site defects and thermal vacancies do not significantly affect the fracture toughness of the Laves phases.

  8. Point Defects in Binary Laves-Phase Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Liaw, P.K.; Liu, C.T.; Pike, L.M.; Zhu, J.H.

    1999-01-11

    Point defects in the binary C15 NbCrQ and NbCoz, and C 14 NbFe2 systems on both sides of stoichiometry were studied by both bulk density and X-ray Iattiee parameter measurements. It was found that the vacancy concentrations in these systems after quenching from 1000"C are essentially zero. The constitutional defects on both sides of stoichiometry for these systems were found to be of the anti-site type in comparison with the model predictions. Thermal vacancies exhibiting a maximum at the stoichiometric composition were obtained in NbCr2 Laves phase alloys after quenching from 1400"C. However, there are essentially no thermal vacancies in NbFe2 alloys after quenching from 1300oC. Anti-site hardening was found on both sides of stoichiometry for all the tie Laves phase systems studied, while the thermal vacancies in NbCr2 alloys quenched from 1400'C were found to soften the Laves phase. The anti-site hardening of the Laves phases is similar to that of the B2 compounds and the thermal vacancy softening is unique to the Laves phase. Neither the anti-site defects nor the thermal vacancies affect the fracture toughness of the Laves phases significantly.

  9. Point Defects in Binary Laves-Phase Alloys

    International Nuclear Information System (INIS)

    Point defects in the binary C15 NbCrQ and NbCoz, and C 14 NbFe2 systems on both sides of stoichiometry were studied by both bulk density and X-ray Iattiee parameter measurements. It was found that the vacancy concentrations in these systems after quenching from 1000''C are essentially zero. The constitutional defects on both sides of stoichiometry for these systems were found to be of the anti-site type in comparison with the model predictions. Thermal vacancies exhibiting a maximum at the stoichiometric composition were obtained in NbCr2 Laves phase alloys after quenching from 1400''C. However, there are essentially no thermal vacancies in NbFe2 alloys after quenching from 1300oC. Anti-site hardening was found on both sides of stoichiometry for all the tie Laves phase systems studied, while the thermal vacancies in NbCr2 alloys quenched from 1400'C were found to soften the Laves phase. The anti-site hardening of the Laves phases is similar to that of the B2 compounds and the thermal vacancy softening is unique to the Laves phase. Neither the anti-site defects nor the thermal vacancies affect the fracture toughness of the Laves phases significantly

  10. Ferromagnetism in Laves-phase WFe{sub 2} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Koten, M. A.; Shield, J. E. [Department of Mechanical and Materials Engineering and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0526 (United States); Manchanda, P.; Balamurugan, B.; Skomski, R.; Sellmyer, D. J. [Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299 (United States)

    2015-07-01

    While rare-earth based Laves phases are known to exhibit large magnetostriction, the magnetic properties of some binary Laves phases containing transition metals alone are not well known. This is because many of these compounds contain refractory elements that complicate melt processing due to high melting temperatures and extensive phase separation. Here, phase-pure WFe{sub 2} nanoclusters, with the hexagonal C14 Laves structure, were deposited via inert gas condensation, allowing for the first known measurement of ferromagnetism in this phase, with M{sub S} of 26.4 emu/g (346 emu/cm{sup 3}) and a K{sub U} of 286 kerg/cm{sup 3}, at 10 K, and a T{sub C} of 550 K.

  11. Ferromagnetism in Laves-phase WFe2 nanoparticles

    Directory of Open Access Journals (Sweden)

    M. A. Koten

    2015-07-01

    Full Text Available While rare-earth based Laves phases are known to exhibit large magnetostriction, the magnetic properties of some binary Laves phases containing transition metals alone are not well known. This is because many of these compounds contain refractory elements that complicate melt processing due to high melting temperatures and extensive phase separation. Here, phase-pure WFe2 nanoclusters, with the hexagonal C14 Laves structure, were deposited via inert gas condensation, allowing for the first known measurement of ferromagnetism in this phase, with MS of 26.4 emu/g (346 emu/cm3 and a KU of 286 kerg/cm3, at 10 K, and a TC of 550 K.

  12. Ferromagnetism in Laves-phase WFe2 nanoparticles

    International Nuclear Information System (INIS)

    While rare-earth based Laves phases are known to exhibit large magnetostriction, the magnetic properties of some binary Laves phases containing transition metals alone are not well known. This is because many of these compounds contain refractory elements that complicate melt processing due to high melting temperatures and extensive phase separation. Here, phase-pure WFe2 nanoclusters, with the hexagonal C14 Laves structure, were deposited via inert gas condensation, allowing for the first known measurement of ferromagnetism in this phase, with MS of 26.4 emu/g (346 emu/cm3) and a KU of 286 kerg/cm3, at 10 K, and a TC of 550 K

  13. Peculiarities of U-based Laves phases

    International Nuclear Information System (INIS)

    This contribution focuses on the structural and physical properties of U-based Laves phases. It starts with the structural description of the different type of Laves phases, followed by a brief description of the factors that affect their stability. The majority of the uranium Laves phases show a weakly paramagnetic behaviour. The reason is the compact structure of the phases that leads to small a U-U spacing as well as very high coordination numbers, regarding both the uranium and the ligands sublattices, which brings a strong hybridization with non-f states. However, there are some exceptions of uranium Laves phases that do order magnetically (UFe2, UNi2 and the recently discovered U2Fe3Ge compound). These exceptions are discussed in more detail in the present manuscript.

  14. Laves phases for high temperatures - structure, stability and constitution

    International Nuclear Information System (INIS)

    The effect of alloying with Al on phase stability and crystal structure of the Laves phases NbCo2 and TaFe2 was studied as part of extended work on Laves phases of transition metals. The ternary phases can be described as Nb(Co1-xAlx)2 and Ta(Fe1-xAlx)2 in view of the respective ternary phase diagrams. Melting temperatures and lattice constants have been measured. The phase equilibria between Ta(Fe1-xAlx)2 and bcc Fe-Al, Fe3Al with D03 structure and FeAl with B2 structure have been studied. The cubic C15 structure of NbCo2 transforms to the hexagonal C14 structure in the temperature range 1050 to 1350 C and is unstable for Al contents above 5 at.% Al. The stability of Laves phases with C15 structure is favoured by a high valence electron concentration. (orig.)

  15. Electron concentration and phase stability in NbCr2-based Laves phase alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, J.H.; Liaw, P.K. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering; Liu, C.T. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

    1997-05-12

    Phase stability in NbCr{sub 2}-based transition-metal Laves phases was studied, based on the data reported for binary X-Cr, Nb-X, and ternary Nb-Cr-X phase diagrams. It was shown that when the atomic size ratios are kept identical, the average electron concentration factor, e/a, is the dominating factor in controlling the phase stability of NbCr{sub 2}-based transition-metal Laves phases. The e/a ratios for different Laves polytypes were determined as followed: with e/a < 5.76, the C15 structure is stabilized; at an e/a range of 5.88--7.53, the C14 structure is stabilized; with e/a > 7.65, the C15 structure is stabilized again. A further increase in the electron concentration factor (e/a > 8) leads to the disordering of the alloy. The electron concentration effect on the phase stability of Mg-based Laves phases and transition-metal A{sub 3}B intermetallic compounds is also reviewed and compared with the present observations in transition-metal Laves phases. In order to verify the e/a/phase stability relationship experimentally, additions of Cu (with e/a = 11) were selected to replace Cr in the NbCr{sub 2} Laves phase. Experimental results for the ternary Nb-Cr-Cu system are reported and discussed in terms of the correlation between the e/a ratio and phase stability in NbCr{sub 2}-based Laves phases. A new phase was found, which has an average composition of Nb-47Cr-3Cu. Within the solubility limit, the electron concentration and phase stability relationship is obeyed in the Nb-Cr-Cu system.

  16. Electronic structure and magnetism of AFe2 compounds with C14 and C15 laves structures

    International Nuclear Information System (INIS)

    The d-band densities of states are calculated by the recursion method for the paramagnetic AFe2 compounds with C14 and C15 structures, where A is occupied by 3d (Sc, Ti, V), 4d (Y, Zr, Nb) or 5d (Lu, Hf, Ta) series' elements. The densities of states of the ferromagnetic and antiferromagnetic (Zr/sub 1-x/Nb/sub x/)Fe2 compounds with C15 and C14 structures are calculated. The pseudobinary systems are treated within a virtual crystal approximation. The trends of the crystal structures are related to the d electron number around the A site. Magnetic moment and spontaneous volume magnetostriction are calculated on the basis of the Stoner theory. (author)

  17. First-principles study of structural and electronic properties of Laves phases structures YM2 (M = Cu and Zn

    Directory of Open Access Journals (Sweden)

    Benabadji M.K.

    2013-09-01

    Full Text Available First-principles calculations have been carried out to investigate the structural properties and electronic structure of the main binary Laves phase YCu2 and YZn2 with C14, C14, C36 and CeCu2 structures in Cu-Y-Zn alloy, respectively. The total energies of Laves phases with various occupations of nonequivalent lattice sites in all four structural forms have been calculated Ab initio by a pseudopotential VASP code. The optimized structural parameters were in very good agreement with the experimental values. The calculated heat of formation showed that the CeCu2-YCu2 and YZn2 Laves phase was of the strongest alloying ability and structural stability. The electronic density of states (DOS and charge density distribution were given.

  18. Magnetic structures of Laves phase superlattices

    Science.gov (United States)

    Bentall, M. J.; Cowley, R. A.; Buyers, W. J. L.; Tun, Z.; Lohstroh, W.; Ward, R. C. C.; Wells, M. R.

    2003-07-01

    We present a determination of the magnetic structures of three Laves phase superlattice samples of structure [70/30]60, [150/100]50, and [50/70]60, where the structure is given as [t1 Å DyFe2/t2 Å YFe2]N, grown by molecular beam epitaxy. The experiments were performed using magnetization measurements and neutron scattering measurements at the NRU reactor at Chalk River in Canada. For the [70/30]60 sample, a magnetic field parallel to the scattering vector, Q, was applied to determine the nuclear component of the scattered intensity. The magnetic structure with the field aligned along the [001] had all the moments aligned along the field direction and the magnitude of the moment on the iron site was temperature independent with a value of 2.3(0.3) muB. The moment on the dysprosium site was found to decrease with temperature from about 10 muB to a value of 6(0.5) muB at 300 K. When the field was applied in the [1bar 10] direction the magnetic moments were found to rotate out of the (110) epitaxial plane towards the [110] direction by an angle psi = 10° at 300 K, which increased at 4 K to an angle of psi = 40° close to the [100] out-of-plane direction. For the [150/100]50 sample, when a 6 T magnetic field was applied along the [1bar 10] direction, the main peak of the magnetically sensitive (11bar 1) reflection was found to decrease in intensity while the scattering at the satellite peaks increased. This change in intensity is due to the formation of magnetic exchange springs in the 'soft' YFe2 layers of the superlattice. Detailed measurements around the (11bar 1) reflection and calculations for an exchange spring model give excellent agreement between the model and the experiment. Finally, the [50/70]60 sample showed unexpected behaviour because the moments aligned largely perpendicular to an applied field. This is similar to a spin-flop phase of an antiferromagnet and it is argued that this occurs because the net moments on the DyFe2 and YFe2 layers are nearly

  19. Influence of long heat treatments on the laves phase nucleation in a type 444 ferritic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Juuti, T., E-mail: timo.juuti@oulu.fi [Centre for Advanced Steels Research, Box 4200, FI-90014 University of Oulu (Finland); Rovatti, L. [Centre for Advanced Steels Research, Box 4200, FI-90014 University of Oulu (Finland); Mäkelä, A. [Department of Process and Environmental Engineering, Box 4300, FI-90014 University of Oulu (Finland); Karjalainen, L.P.; Porter, D. [Centre for Advanced Steels Research, Box 4200, FI-90014 University of Oulu (Finland)

    2014-12-15

    Highlights: • Laves in type 444 steel was characterized as hexagonal C14 structured (FeCrSi){sub 2}(MoNb). • Morphology of Laves particles was found dependant on the relationship with α-Fe. • The difference in coherence could be result of nucleation in different process stage. • The lattice parameters of the (FeCrSi){sub 2}(MoNb)-type Laves phase were calculated. - Abstract: Composition, morphology and nucleation of Laves phase particles containing Mo, Nb and Si were investigated in a type 444 (18%Cr–0.4%Nb–0.1%Ti–0.5%Si–2.0%Mo) ferritic stainless steel heat treated at 650 °C for up to 120 h with and without a heat treatment and dissolution treatment at 1050 °C during which all Laves phase dissolve. In situ and extracted precipitate particles were analysed using scanning and transmission electron microscopy, energy-dispersive spectroscopy and X-ray diffraction. An (FeCrSi){sub 2}(MoNb) Laves phase, titanium nitrides and niobium carbides were present in the as-received sheet prior to heat treatment but during treatment at 650 °C the number density and size of Laves phase particles increased substantially within 120 h. The morphology of the hexagonal (FeCrSi){sub 2}(MoNb) Laves phase was characterized as either plate-like or equiaxed depending on whether the particle had an orientation relationship with the matrix or not, i.e. whether the precipitate nucleated during the heat treatment or was present in the as-received material.

  20. Stability of Laves Phases in the Cr Zr System

    Czech Academy of Sciences Publication Activity Database

    Pavlů, Jana; Vřešťál, Jan; Šob, Mojmír

    2009-01-01

    Roč. 33, č. 2 (2009), s. 382-387. ISSN 0364-5916 R&D Projects: GA ČR GA106/07/1078 Institutional research plan: CEZ:AV0Z20410507 Keywords : ab initio calculations * Laves phases * phase diagrams Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.904, year: 2009

  1. Studies of Sn, Co, Al, and Fe additives in C14/C15 Laves alloys for NiMH battery application by orthogonal arrays

    International Nuclear Information System (INIS)

    The effects of Sn, Co, Al, and Fe as additives to C14/C15 Laves phase alloy in nickel metal hydride battery are studied with modified L-16 orthogonal arrays. Sixteen alloys with the general formula Ti9Zr2-wV5Ni38Cr5-xMn16-y-zSnwCoxAlyFez were prepared and made into sealed cells. The main components of these alloys are C14 and C15 structured AB2 phases with significant difference in Ni-content. Other minor phases found are Zr2Ni2Sn, ZrNi, Zr7Ni10, and Zr9Ni11. In the gas phase study, while the variations in pressure-concentration isotherm hysteresis and slope factor are small, the detrimental effects to storage capacity from Sn and Al are more evident than those from Co and Fe. Al lowers the equilibrium pressure plateau while the other three additives raise it. In the electrochemical study, a higher level of Sn promotes a greater content of the Zr2Ni2Sn phase which is less stable in an alkaline environment and has a detrimental effect on both charge retention and cycle life performance. Sn is also not desirable for applications with a demanding request of high-rate and low-temperature performance. The addition of Sn is to ease the activation and to reduce raw material cost by allowing the use of less expensive zirconium source. Adequate amounts of Co and Al addition improve activation, low temperature, and specific power of the battery. Addition of Fe makes activation more difficult and decreases specific power, but improves both charge retention and cycle life. We propose two recipes; one level composed of 1.5% Co and 0.4% Al of additives for power applications and the other with 1% Co and 0.4% Fe for a good balance among other battery properties.

  2. Characterisation of Laves phase precipitation and its correlation to creep rupture strength of ferritic steels

    International Nuclear Information System (INIS)

    The Laves phase precipitation process was characterised by means of field emission scanning electron microscopy to demonstrate its effect on creep rupture strength of steels with a fully ferritic matrix. To eliminate the effects of carbide and carbonitride precipitations so that the creep rupture data can be analysed exclusively in relation to the Laves phase precipitation process, an alloy Fe–9Cr–3Co–3W (wt.%) without C and N additions was used for the study. Creep rupture strengths were measured and volume fraction and particle size of Laves phase precipitates in the ruptured specimens were analysed. It was found that the creep rupture strength started to collapse (or decrease more rapidly) long before the Laves phase precipitation reached equilibrium fraction. This was related to the onset of the coarsening of Laves phase particles, which precipitated only on grain boundaries and hence contributed little to precipitation strengthening. Creep deformation had no effect either on the precipitation kinetics or on the growth kinetics of Laves phase particles. - Highlights: • Laves phase precipitation at 650 °C was characterised for Fe–9Cr–3W–3Co alloy. • Laves phase precipitated predominantly on grain boundaries. • Creep deformation had no effect on Laves phase precipitation and growth kinetics. • Creep strength started to collapse long before Laves phase precipitation is ended. • Collapse of creep strength was attributed to the coarsening of Laves phase particles

  3. Characterisation of Laves phase precipitation and its correlation to creep rupture strength of ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, S.; Yang, M.; Song, X.L.; Tang, S.; Xiang, Z.D., E-mail: zhidongxiang@hotmail.com

    2014-12-15

    The Laves phase precipitation process was characterised by means of field emission scanning electron microscopy to demonstrate its effect on creep rupture strength of steels with a fully ferritic matrix. To eliminate the effects of carbide and carbonitride precipitations so that the creep rupture data can be analysed exclusively in relation to the Laves phase precipitation process, an alloy Fe–9Cr–3Co–3W (wt.%) without C and N additions was used for the study. Creep rupture strengths were measured and volume fraction and particle size of Laves phase precipitates in the ruptured specimens were analysed. It was found that the creep rupture strength started to collapse (or decrease more rapidly) long before the Laves phase precipitation reached equilibrium fraction. This was related to the onset of the coarsening of Laves phase particles, which precipitated only on grain boundaries and hence contributed little to precipitation strengthening. Creep deformation had no effect either on the precipitation kinetics or on the growth kinetics of Laves phase particles. - Highlights: • Laves phase precipitation at 650 °C was characterised for Fe–9Cr–3W–3Co alloy. • Laves phase precipitated predominantly on grain boundaries. • Creep deformation had no effect on Laves phase precipitation and growth kinetics. • Creep strength started to collapse long before Laves phase precipitation is ended. • Collapse of creep strength was attributed to the coarsening of Laves phase particles.

  4. Site occupancies in ternary C15 ordered Laves phases

    International Nuclear Information System (INIS)

    Site occupancies in three C15-structured AB2(X) Laves phases have been determined by Atom Location by CHanneling Enhanced MIcroanalysis (ALCHEMI). In NbCr2(V), the results were consistent with exclusive site occupancies of Nb for the A sublattice and Cr and V for the B sublattice. The B-site occupancy of V is not expected from atom size effects alone. In NbCr2(Ti), the results were consistent with Ti partitioning mostly to the A sites with some anti-site defects likely. In HfV2(Nb), the results were consistent with Nb partitioning between the A and B sites. The results of the ALCHEMI analyses of these ternary C15 Laves phase materials will be discussed with respect to previously determined phase diagrams and first-principles total energy and electronic structure calculations

  5. Interlayer diffusion studies of a Laves phase exchange spring superlattice

    Science.gov (United States)

    Wang, C.; Kohn, A.; Wang, S. G.; Ward, R. C. C.

    2011-03-01

    Rare earth Laves phase (RFe2) superlattice structures grown at different temperatures are studied using x-ray reflectivity (XRR), x-ray diffraction, and transmission electron microscopy. The optimized molecular beam epitaxy growth condition is matched with the XRR simulation, showing minimum diffusion/roughness at the interfaces. Electron microscopy characterization reveals that the epitaxial growth develops from initial 3D islands to a high quality superlattice structure. Under this optimum growth condition, chemical analysis by electron energy loss spectroscopy with high spatial resolution is used to study the interface. The analysis shows that the interface roughness is between 0.6 and 0.8 nm and there is no significant interlayer diffusion. The locally sharp interface found in this work explains the success of simple structural models in predicting the magnetic reversal behavior of Laves exchange spring superlattices.

  6. Study of fatigue and fracture behavior of NbCr{sub 2}-based alloys and intermetallic materials: Phase stability in NbCr{sub 2} Laves phase alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, J.H.; Liaw, P.K. [Univ. of Tennessee, Knoxville, TN (United States); Liu, C.T. [Oak Ridge National Lab., TN (United States)

    1996-08-01

    Phase stability in NbCr{sub 2}-based transition-metal Laves phases is studied in this paper, using data from binary X-Cr, Nb-X, and ternary Nb-Cr-X phase diagrams. It was shown that when the atomic size ratios are kept identical, the average electron concentration factor (e/a = the average number of electrons per atom outside the closed shells of the component atoms) is the determinate factor in controlling the phase stability of NbCr{sub 2}-based transition-metal Laves phases. The e/a ratios for different Laves phase structures were determined as follows: with e/a < 5.76, the C15 structure is stabilized; at an e/a range of 5.88-7.53, the C14 structure is stabilized; with e/a > 7.65, the C15 structure was stabilized again. A further increase in the electron concentration factor (e/a > 8) leads to the disordering of the alloy. The electron concentration effect on the phase stability of transition-metal A{sub 3}B intermetallic compounds and Mg-based Laves phases is also reviewed and compared with the present observations in transition-metal Laves phases.

  7. Investigations on the growth kinetics of Laves phase precipitates in 12% Cr creep-resistant steels: Experimental and DICTRA calculations

    International Nuclear Information System (INIS)

    The growth kinetics of Laves phase precipitates (type Fe2W) in the early stage of creep (650 deg. C for 10,000 h) in two 12% Cr ferrite-martensitic steels has been investigated. In one alloy the Laves phase formed on tempering, while in the second alloy the Laves phase precipitated during creep. Kinetic simulations were performed using the software DICTRA. The particle size of the Laves phase was measured on transmission electron microscopy samples. The equilibrium phase fraction of the Laves phase was reached in the first thousand hours. Simulations of particle growth showed good agreement with the experimental results. Competitive growth between M23C6 and the Laves phase showed that M23C6 carbides reached their equilibrium after 12 days, whereas the Laves phase reached equilibrium after 3 months. Simulations of the influence of the interfacial energy and addition of Co, Cu and Si on Laves phase precipitation are presented.

  8. Summary of workshop on high temperature materials based on Laves phases

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-08-01

    The Offices of Fossil Energy and Basic Energy Sciences of the Department of Energy jointly sponsored the Workshop on High Temperature Materials Based on Laves Phases in conjunction with the Tenth Annual Conference on Fossil Energy Materials held at the Radisson Summit Hill Hotel in Knoxville, Tennessee on May 14-16, 1996. The objective of this workshop was to review the current status and to address critical issues in the development of new-generation high-temperature structural materials based on Laves phases. The one-day workshop included two sessions of overview presentations and a session of discussion on critical scientific and technological issues. The Laves phases represent an abundant class of intermetallic alloys with possible high-temperature structural applications. Laves phases form at or near the AB{sub 2} composition, and there are over 360 binary Laves phases. The ability of these alloys to dissolve considerable amounts of ternary alloying additions provides over 900 combined binary and ternary Laves phases. Many Laves phases have unique properties which make them attractive for high-temperature structural use. At half their homologous temperature, they retain >0.85 of their ambient yield strength, which is higher than all other intermetallics. Many of the Laves phases also have high melting temperatures, excellent creep properties, reasonably low densities, and for alloys containing Cr, Al, Si or Be, good oxidation resistance. Despite these useful properties, the tendency for low-temperature brittleness has limited the potential application of this large class of alloys.

  9. Clean Grain Boundary Found in C14/Body-Center-Cubic Multi-Phase Metal Hydride Alloys

    Directory of Open Access Journals (Sweden)

    Hao-Ting Shen

    2016-06-01

    Full Text Available The grain boundaries of three Laves phase-related body-center-cubic (bcc solid-solution, metal hydride (MH alloys with different phase abundances were closely examined by scanning electron microscopy (SEM, transmission electron microscopy (TEM, and more importantly, electron backscatter diffraction (EBSD techniques. By using EBSD, we were able to identify the alignment of the crystallographic orientations of the three major phases in the alloys (C14, bcc, and B2 structures. This finding confirms the presence of crystallographically sharp interfaces between neighboring phases, which is a basic assumption for synergetic effects in a multi-phase MH system.

  10. Hydrogen diffusion in the Laves-phase compound TiCr1.78

    International Nuclear Information System (INIS)

    The temperature dependence of the Young's modulus and of the internal friction (IF) has been investigated between 80 and 300 K at acoustical frequencies in the hexagonal (C14) Laves-phase TiCr1.78 charged with hydrogen. In this compound H occupies tetrahedral interstitial sites which are grouped in interlinked hexagons. A mechanical relaxation has been found at around 120 K (f = 5.4 kHz), which appears to be due to tunnelling transitions of delocalized H from one hexagon to the other. The rate of H absorption has been investigated at high temperature (660-1200 K) and the H diffusion coefficient has been derived from the pressure measurement as a function of time. A cumulative Arrhenius plot of IF and absorption diffusion data exhibits a non-exponential behaviour, which is due to a change in the diffusion mechanism from over-barrier hopping at high temperature to phonon-assisted tunnelling at low temperature.

  11. Structural, electronic and elastic properties of the Laves phases WFe2, MoFe2, WCr2 and MoCr2 from first-principles

    Science.gov (United States)

    Lv, Z. Q.; Zhang, Z. F.; Zhang, Q.; Wang, Z. H.; Sun, S. H.; Fu, W. T.

    2016-06-01

    A theoretical analysis of the phase stability, electronic and mechanical properties, and Debye temperatures of the C14-type Laves phases (WFe2, MoFe2, WCr2 and MoCr2) has been presented from density functional theory. The phase stability follows the order: WFe2>MoFe2>WCr2>MoCr2. An exchange of electrons takes place between Fe and W/Mo atoms, and there is also electron transfer between Cr and W/Mo. The W-W and Mo-Mo bonds are of the valence character, while the Fe-W/Mo and Cr-W/Mo bonds are of ionic character. The bonding force of A-A is greater than that of A-B in C-14 AB2 type Laves phases (WFe2, MoFe2, WCr2 and MoCr2). The ductility of MoCr2 is higher than others. The hardness of WFe2 (14.1 GPa) is the highest, and the hardness of MoCr2 is the lowest. The incompressibility for these laves phases along c-axis is larger than that along a-axis. The Debye temperature (θD) of MoFe2 is 619 K, which is the highest in those phases. These laves phases also have high melting points, which follows the order: WFe2>MoFe2>WCr2>MoCr2.

  12. Laves-phase in the China Low Activation Martensitic steel after long-term creep exposure

    International Nuclear Information System (INIS)

    Highlights: • The crept specimen was divided into three regions according to stress levels. • The creep stress could enhance the microstructure recovery. • Laves phase showed different features along the length of crept specimen. • The density of Laves phase was high, while its size was small near the neck region. • The creep stress enhanced the formation of Laves phase during creep. - Abstract: Creep test at 600 °C under 130 MPa for the China Low Activation Martensitic (CLAM) steel was performed up to 7913 h in this study. According to the stress level, the crept specimen was divided into three regions in order to investigate the influence of stress on Laves-phase formation. In addition to the expected M23C6 carbide and MX carbonitride, the amount and the size of Laves phase in these three regions on the crept specimen were characterized by transmission electron microscopy. Laves phase could be found in all the regions and the creep stress could promote the formation of Laves phase

  13. Quantification of Laves Phase Particle Size in 9CrW Steel

    DEFF Research Database (Denmark)

    Korcakova, Leona; Hald, John; Somers, Marcel A.J.

    2001-01-01

    Tungsten-alloyed martensic 9Cr steels are applied for streamlines of advanced power plants because of their superior creep performance. Tungsten, as the main new alloying element, induces precipitation of intermetallic Laves phase during long-term exposure at service temperatures around 600 C. The...... growth and coarsening of Laves phase was investigated for the martensitic 9CrW steel P92 after aging and after creep testing at 600 or 650 C for times up to 59,000 h. For measurement of the size of Laves phase particles, field emission gun scanning electron microscopy (FEGSEM) was used along with image...

  14. Quantification of Laves Phase Particle Size in 9CrW Steel

    DEFF Research Database (Denmark)

    Korcakova, Leona; Hald, John; Somers, Marcel A.J.

    2001-01-01

    growth and coarsening of Laves phase was investigated for the martensitic 9CrW steel P92 after aging and after creep testing at 600 or 650 C for times up to 59,000 h. For measurement of the size of Laves phase particles, field emission gun scanning electron microscopy (FEGSEM) was used along with image...... analysis. This technique allows discrimination of Laves phase particles from M23C6 carbides. The measured particle sizes were statistically evaluated and compared with values obtained using energy-filtered transmission electron microscopy(EFTEM)....

  15. Phase stability and defect structure of the C15 Laves phase Nb(Cr,V)2

    International Nuclear Information System (INIS)

    Vanadium alloyed C15 Laves phase based on NbCr2 and phase equilibria in the Nb-Cr-V system have been studied, focusing on the physical metallurgy and defect structures of the C15 phase.Based on the Nb-Cr-V phase diagram established in this work, the defect structure/mechanism in the ternary C15 Laves phase is investigated using a combination of metallography, SEM/EDS, TEM/ALCHEMI, and X-ray powder diffraction. It is found that the C15 phase field of NbCr2 is extended by V alloying up to more than 3 at.% V and V substitutes exclusively on the Cr site instead of the Nb site, although the atomic sizes of the constituent elements indicate rCr V Nb. The lattice constants of the ternary C15 phase Nb(Cr,V)2 increase linearly with increasing V content. The electronic structure and total energy of the C15 intermetallic phase NbCr2 have been calculated using the linear muffin tin orbital (LMTO) method with the atomic sphere approximation (ASA). The electronic band structure and density of electronic states were obtained. The formation and stability of the ternary C15 Laves phase Nb(Cr,V)2, the defect structure/mechanism, and the compositional dependence of the lattice constants are elucidated using a combination of geometric and electronic considerations. These results indicate that the electronic factor may also play an important role, in addition to the atomic size rule, in determining the alloying behavior and the defect structure/mechanism of C15 Laves phases based on NbCr2

  16. Hydrogen diffusion in the Laves-phase compound TiCr{sub 1.78}

    Energy Technology Data Exchange (ETDEWEB)

    Mazzolai, G. [University of Perugia, Department of Physics, Via A. Pascoli 5, 06100 Perugia (Italy); Universita Telematica e-Campus, Via Isimbardi 10, Novedrate (Colombia) (Italy); Coluzzi, B.; Biscarini, A. [University of Perugia, Department of Physics, Via A. Pascoli 5, 06100 Perugia (Italy); Mazzolai, F.M., E-mail: fabio.mazzolai@fisica.unipg.it [University of Perugia, Department of Physics, Via A. Pascoli 5, 06100 Perugia (Italy); Tuissi, A. [Institute for Energy and Interphases, CNR-IENI, C.so Promessi Sposi, 29, Lecco (Italy); Agresti, F.; Principi, G. [University of Padua, Dept. of Mech. Eng., via Marzolo 8, 35131 Padua (Italy); Lo Russo, S. [University of Padua, Physics Dept., via Marzolo 8, 35131 Padua (Italy)

    2009-09-15

    The temperature dependence of the Young's modulus and of the internal friction (IF) has been investigated between 80 and 300 K at acoustical frequencies in the hexagonal (C14) Laves-phase TiCr{sub 1.78} charged with hydrogen. In this compound H occupies tetrahedral interstitial sites which are grouped in interlinked hexagons. A mechanical relaxation has been found at around 120 K (f = 5.4 kHz), which appears to be due to tunnelling transitions of delocalized H from one hexagon to the other. The rate of H absorption has been investigated at high temperature (660-1200 K) and the H diffusion coefficient has been derived from the pressure measurement as a function of time. A cumulative Arrhenius plot of IF and absorption diffusion data exhibits a non-exponential behaviour, which is due to a change in the diffusion mechanism from over-barrier hopping at high temperature to phonon-assisted tunnelling at low temperature.

  17. Investigations on the growth kinetics of Laves phase precipitates in 12% Cr creep-resistant steels: Experimental and DICTRA calculations

    Energy Technology Data Exchange (ETDEWEB)

    Prat, O. [Max Planck Institute fuer Eisenforschung GmbH, Max Planck Strasse 1, 40237 Duesseldorf (Germany)] [Universidad de Concepcion, Departamento de Ingenieria de Materiales, Edmundo Larenas 270, Concepcion (Chile); Garcia, J., E-mail: jose.garcia@helmholtz-berlin.de [Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Rojas, D. [Max Planck Institute fuer Eisenforschung GmbH, Max Planck Strasse 1, 40237 Duesseldorf (Germany); Carrasco, C. [Universidad de Concepcion, Departamento de Ingenieria de Materiales, Edmundo Larenas 270, Concepcion (Chile); Inden, G. [Max Planck Institute fuer Eisenforschung GmbH, Max Planck Strasse 1, 40237 Duesseldorf (Germany)

    2010-10-15

    The growth kinetics of Laves phase precipitates (type Fe{sub 2}W) in the early stage of creep (650 deg. C for 10,000 h) in two 12% Cr ferrite-martensitic steels has been investigated. In one alloy the Laves phase formed on tempering, while in the second alloy the Laves phase precipitated during creep. Kinetic simulations were performed using the software DICTRA. The particle size of the Laves phase was measured on transmission electron microscopy samples. The equilibrium phase fraction of the Laves phase was reached in the first thousand hours. Simulations of particle growth showed good agreement with the experimental results. Competitive growth between M{sub 23}C{sub 6} and the Laves phase showed that M{sub 23}C{sub 6} carbides reached their equilibrium after 12 days, whereas the Laves phase reached equilibrium after 3 months. Simulations of the influence of the interfacial energy and addition of Co, Cu and Si on Laves phase precipitation are presented.

  18. Measuring laves phase particle size and thermodynamic calculating its growth and coarsening behavior in P92 steels

    DEFF Research Database (Denmark)

    Yao, Bing-Yin; Zhou, Rong-Can; Fan, Chang-Xin;

    2010-01-01

    The growth of Laves phase particles in three kinds of P92 steels were investigated. Laves phase particles can be easily separated and distinguished from the matrix and other particles by atom number contrast using comparisons of the backscatter electrons (BSE) images and the secondary electrons (...

  19. Precipitation of Icosahedral Quasicrystalline Phase, R-phase and Laves Phase in Ferritic Alloys

    Institute of Scientific and Technical Information of China (English)

    Keisuke Yamamoto; Yoshisato Kimura; Yoshinao Mishima

    2004-01-01

    Ferritic heat resistant steels involving precipitation of intermetallic phases have drawn a growing interest for the enhancement of creep strength, while the brittleness of the intermetallic phases may lower the toughness of the alloy.Therefore, it is necessary to optimize the dispersion characteristics of the intermetallics phase through microstructural control to minimize the trade-off between the strength and toughness. The effects of α-Fe matrix substructures on the precipitation sequence, morphology, dispersion characteristics, and the stability of the intermetallic phases are investigated in Fe-Cr-W-Co-Si system. The precipitates of the Si-free Fe-10Cr-1.4W-4.5Co (at%) alloy aged at 873K are the R-phase but those of the Si-added Fe-10Cr-1.4W-4.5Co-0.3Si (at%) alloy are the icosahedral quasicrystalline phase. The precipitates in both the Si-free and Si-added alloys aged at 973K are the Laves phase. Matrix of the alloys is controlled by heat treatments as to provide three types of matrix substructures; ferrite, ferrite/martensite mixture and martensite. The hardening behavior of the alloys depends on the matrix substructures and is independent of the kinds of precipitates. In the alloys with ferrite matrix, the peak of hardness during aging at 873K shifts to longer aging time in comparison with that in the alloys with lath martensite matrix which contain numbers of nucleation sites.

  20. Supersaturation of the Al2Y Laves phase by rapid solidification

    International Nuclear Information System (INIS)

    Intermetallic phases often appear to exhibit a restricted compositional range of stability essentially limited to the stoichiometric value. However, there are important exceptions, such as B2 and L12 phases, where relatively wide fields of compositional stability develop. In the well-known B2 phases, such as NiAl, the operation of different defect mechanisms has been extensively documented and has an important impact on the mechanical behavior. The Laves phase class of intermetallics is a good example of a class where most representatives are essentially stoichiometric. However, there are important exceptions, such as NbCr2, where the solubility range is several percent. Although there are a larger number of Laves phases than B2 phases, relatively little is known about the possible defect structures that may be associated with solubility at off-stoichiometric compositions. If the intrinsic stability of a structure allows for departures from stoichiometry, then it may be possible to access even greater levels of departure by rapid solidification processing (RSP). An early report for the Al2Y Laves phase indicates that some departure from stoichiometry is possible during RSP. An assessment of the extent of metastable solubility for Al2Y and an analysis of the intermetallic solubility behavior are reported in the current work

  1. Phase stability of laves intermetallics in a stainless steel-zirconium alloy

    International Nuclear Information System (INIS)

    Phase transformations occurring in a stainless steel-15 wt% zirconium (SS-15Zr) alloy were studied by in situ neutron diffraction. Neutron diffraction patterns as a function of time were obtained on alloys that were held at various elevated temperatures (1084-1275 C). As-cast SS-15Zr alloys contain ferrite, austenite, ZrFe2-type Laves polytypes C36 and C15, and small amounts of a Fe23Zr6-type intermetallic. Annealing at high temperatures resulted in an increase of the Fe23Zr6, intermetallic content. The C15 Laves polytype is the equilibrium phase for T ≤ 1230 C; C36 is the stable polytype at higher temperatures (∼1275 C). Phase changes were slow for temperatures <1100 C.These findings have important implications for use of the SS-15Zr alloy as a nuclear waste form

  2. Computational thermodynamic investigations of growth and coarsening of laves phase precipitates in 12%Cr creep resistant steels

    Energy Technology Data Exchange (ETDEWEB)

    Prat, O.; Rojas, D. [Max-Planck-Institut fuer Eisenforschung GmbH, Duesseldorf (Germany); Garcia, J.; Kaysser-Pyzalla, A.R. [Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH, Berlin (Germany); Bochum Univ. (Germany)

    2010-07-01

    Precipitation phenomena in 12%Cr high alloyed steels have been investigated at creep conditions of 650 and 150 MPa up to 6.500 hours in two different alloys. Growth and coarsening of Laves phase was determined experimentally by measuring the size of Laves phase on crept samples using scanning transmission electron microscopy (STEM). The simulations were performed using the software DICTRA based on the assumption the local equilibrium at the moving phase interface. For equilibrium calculations, the Thermo-Calc software was used. The experimental results were compared with DICTRA simulations, showing good agreement. Both the quantitative metallographic measurements as well as the simulations indicate very low coarsening for Laves Phase. The influence of different elements such as Co, Si and Cu on coarsening for Laves phase was simulated. (orig.)

  3. Deformation at ambient and high temperature of in situ Laves phases-ferrite composites

    International Nuclear Information System (INIS)

    The mechanical behavior of a Fe80Zr10Cr10 alloy has been studied at ambient and high temperature. This Fe80Zr10Cr10 alloy, whoose microstructure is formed by alternate lamellae of Laves phase and ferrite, constitutes a very simple example of an in situ CMA phase composite. The role of the Laves phase type was investigated in a previous study while the present work focuses on the influence of the microstructure length scale owing to a series of alloys cast at different cooling rates that display microstructures with Laves phase lamellae width ranging from ∼50 nm to ∼150 nm. Room temperature compression tests have revealed a very high strength (up to 2 GPa) combined with a very high ductility (up to 35%). Both strength and ductility increase with reduction of the lamella width. High temperature compression tests have shown that a high strength (900 MPa) is maintained up to 873 K. Microstructural study of the deformed samples suggests that the confinement of dislocations in the ferrite lamellae is responsible for strengthening at both ambient and high temperature. The microstructure scale in addition to CMA phase structural features stands then as a key parameter for optimization of mechanical properties of CMA in situ composites. (papers)

  4. Quantification of the Laves phase in advanced 9-12% Cr steels using a standard SEM

    International Nuclear Information System (INIS)

    The precipitates in 9-12% Cr steels are usually quantified using the TEM/EFTEM method in combination with an image analysis routine. Because of the limited spatial area of investigation, a complete statistical quantification and description of Laves-phase precipitation, based on this method, is not possible. To compensate the limited magnification range, a technique has been developed to measure larger particles also using a standard scanning electron microscope (SEM). To enable the scanning of a large specimen area, a special preparation technique, in combination with a self-developed quantification routine, was applied. The growth and coarsening of the Laves phase was investigated for several advanced 9-12% Cr heat-resistant steels at 600 and 650 deg. C. The results are compared with published values obtained from (partly) different measuring techniques as well as to thermodynamic equilibrium calculations

  5. Defects and site occupancies in Nb-Cr-Ti C15 Laves phase alloys

    International Nuclear Information System (INIS)

    A multiply-faulted dipole in the C15 Laves phase of composition Nb15Cr68Ti17 has been characterized. The dislocations all lie along [011] and show no residual contrast when imaged edge-on at B = [0 bar 1 bar 1] indicating that they are edge in character. Given this, the Burgers vectors for the Shockley partials are ± 1/6[2 bar 11] and those of the stair-rods are ± 1/6[0 bar 11]. This is consistent with a g · b analysis which was performed. The stacking fault energy was determined to be 35 mJ/m2 which is higher than the experimental value of 25 mJ/m2 from NbCr2. Simulations are currently underway to understand, given the site occupancies and observed trend in stacking fault energy, whether Ti would be expected to raise the stacking fault energy of the C15 Laves phase

  6. First principles total energy study of NbCr2 + V Laves phase ternary system

    International Nuclear Information System (INIS)

    The C15 NbCr2 + V Laves phase ternary system is studied by using a first-principles, self-consistent, full-potential total energy method. Equilibrium lattice parameters, cohesive energies, density of states and formation energies of substitutional defects are calculated. Results of all these calculations show that in the C15 NbCr2 + V compounds, V atoms substitute Cr atoms only

  7. Microstructures and hydrogenation properties of (ZrTi)(V{sub 1−x}Al{sub x}){sub 2} Laves phase intermetallic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Tiandong; Xue, Xiangyi; Zhang, Tiebang, E-mail: tiebangzhang@nwpu.edu.cn; Hu, Rui; Kou, Hongchao; Li, Jinshan

    2015-10-05

    Highlights: • Role of Al on the microstructure and hydrogenation properties is discussed. • A positive effect in hydrogen dissociation can be introduced by Al on the surface of alloys. • Kinetics and thermodynamic parameters of Zr–Ti–V–Al alloys are obtained. • Partial substitution of Al decreases hysteresis between absorption and desorption. - Abstract: In this work, the (ZrTi)(V{sub 1−x}Al{sub x}){sub 2} (x = 0.02, 0.05, 0.10, 0.15, 0.25) Laves phase intermetallic compounds were prepared by the arc-melting method. The microstructure and phase compositions were examined by SEM and XRD. Hydrogen absorption pressure composition isotherms (P–C isotherms) were obtained by the pressure reduction method using a Sievert type apparatus at different temperatures. The thermodynamic and kinetic properties of the alloys were investigated in this work. The results show that the (ZrTi)(V{sub 1−x}Al{sub x}){sub 2} alloys consist of a dominant C15 Laves phase with cubic structure and a V-based solid solution phase with BCC structure. With further increasing Al content, C15 cubic type Laves phase and C14 hexagonal type Laves phase coexist in the range x ⩾ 0.15 in this (ZrTi)(V{sub 1−x}Al{sub x}){sub 2} alloys. The crystal lattice parameter of the C15 phase increases with the increase of Al content. The PCT curves give the evidence that the maximum hydrogen absorption capacity decreases with the increase of Al content, which results from the existence of ZrAl{sub 2} which hardly absorb hydrogen. There is no obvious hysteresis between absorption and desorption in the (ZrTi)(V{sub 1−x}Al{sub x}){sub 2} alloys at 823 K. The (ZrTi)(V{sub 1−x}Al{sub x}){sub 2} alloys with x = 0.25 preserves higher temperature of phase transformation (β → α). The existence of C14 phase (including ZrV{sub 2} and ZrAl{sub 2}) decreases the stability of hydrides.

  8. Defects and site occupancies in Nb-Cr-Ti C15 Laves phase alloys

    International Nuclear Information System (INIS)

    In the Nb-Cr-Ti system, there is a complete solid solution between NbCr2 and TiCr2 with a significant range of solubility for the C15 phase and a large two-phase region of bcc and C15. The Nb-Cr-Ti phase diagram (950 C isothermal section) is shown. The initial characterization by transmission electron microscopy (TEM) of the defect structure of an alloy of overall composition Nb10Cr75Ti15 is discussed here. Additionally, Atom Location by CHanneling Enhanced MIcroanalysis (ALCHEMI) was employed to examine the site occupancies of the Nb, Cr and Ti in this C15 Laves phase

  9. Laves phases in the V-Zr system below room temperature: Stability analysis using ab initio results and phase digram

    Czech Academy of Sciences Publication Activity Database

    Štrof, J.; Pavlů, Jana; Wdowik, U.; Buršík, Jiří; Šob, Mojmír; Vřešťál, Jan

    2014-01-01

    Roč. 44, MAR (2014), s. 62-69. ISSN 0364-5916 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : laves phases * V-Zr system * ab initio calculations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.370, year: 2014

  10. Nb-Based Laves Phase Alloys Prepared by Laser Surface Remelting

    Science.gov (United States)

    Li, K. W.; Li, S. M.; Wang, X. B.; Zhong, H.; Xue, Y. L.; Fu, H. Z.

    2014-09-01

    The microstructure and mechanical properties of Cr2Nb-based intermetallic matrix composites fabricated by laser surface remelting were investigated at hypoeutectic and hypereutectic compositions. In the hypoeutectic composition, the molten zones under different laser scanning velocities consist of fully α-Cr dendrites, whereas a series of morphology evolutions perpendicular to the scanning direction occurred in the hypereutectic composition: Cr2Nb primary phase + Cr/Cr2Nb eutectic → Cr/Cr2Nb eutectic → α-Cr primary phase + Cr/Cr2Nb eutectic → fully α-Cr dendrite. Based on the maximum growth rate criterion, the microstructure evolutions of the molten zones were analyzed by considering the competitive growth among the α-Cr phase, Cr2Nb Laves phase, and the Cr/Cr2Nb eutectic, which are in agreement with the experimental results. More importantly, the room-temperature fracture toughness values of the hypoeutectic and hypereutectic alloys attain 11.2 MPa m1/2 and 7.9 MPa m1/2, respectively, which increase by eight and six times over the as-cast Cr2Nb Laves phase (1.2 MPa m1/2), respectively. The remarkable enhancements in room-temperature fracture toughness were explained in terms of fine-grain toughening, second Cr phase toughening, and point defects toughening.

  11. Growth Kinetics of Laves Phase and Its Effect on Creep Rupture Behavior in 9Cr Heat Resistant Steel

    Institute of Scientific and Technical Information of China (English)

    Zhi-xin XIA; Chuan-yang WANG; Chen LEI; Yun-ting LAI; Yan-fen ZHAO; Lu ZHANG

    2016-01-01

    The effects of Laves phase formation and growth on creep rupture behaviors of P92 steel at 883 K were studied.The microstructural evolution was characterized using scanning electron microscopy and transmission elec-tron microscopy.Kinetic modeling was carried out using the software DICTRA.The results indicated Fe2 (W,Mo) Laves phase has formed during creep with 200 MPa applied stress at 883 K for 243 h.The experimental results showed a good agreement with thermodynamic calculations.The plastic deformation of laths is the main reason of creep rupture under the applied stress beyond 160 MPa,whereas,creep voids initiated by coarser Laves phase play an effective role in creep rupture under the applied stress lower than 160 MPa.Laves phase particles with the mean size of 243 nm lead to the change of creep rupture feature.Microstructures at the vicinity of fracture surface,the gage portion and the threaded ends of creep rupture specimens were also observed,indicating that creep tensile stress enhances the coarsening of Laves phase.

  12. Stability of self-interstitial clusters with C15 Laves phase structure in iron

    Science.gov (United States)

    Dézerald, L.; Marinica, M.-C.; Ventelon, Lisa; Rodney, D.; Willaime, F.

    2014-06-01

    The energetics and stability of self-interstitial clusters with C15 Laves phase structure in iron are investigated by Density Functional Theory (DFT) calculations. First, the properties of bulk C15 are examined. The C15 structure is shown to be mechanically and dynamically stable. Second, the influence of the calculation scheme on the energy difference between C15, ring and loop configurations of di-, tri-, tetra- and octa-interstitial clusters is studied. These calculations confirm that, according to DFT, the C15 structure has by far the lowest energy of all known configurations of tetra- and octa-interstitial clusters in bcc-Fe.

  13. Laves-phase evolution during aging in 9Cr-1.8W-0.5Mo-VNb steel for USC power plants

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xue, E-mail: wangxue2011@whu.edu.cn [School of Power and Mechanics, Wuhan University, Wuhan 430072 (China); Xu, Qiang [School of Computing and Engineering, The University of Huddersfield, Huddersfield HD1 3DH, England (United Kingdom); Yu, Shu-min; Hu, Lei [School of Power and Mechanics, Wuhan University, Wuhan 430072 (China); Liu, Hong [DongFang Boiler Group Co.,Ltd., Zigong 643001 (China); Ren, Yao-yao [School of Power and Mechanics, Wuhan University, Wuhan 430072 (China)

    2015-08-01

    Long term precipitation and coarsening of Laves-phase in tungsten strengthened 9% Cr steel under thermal aging at 923 K was investigated and reported in this paper. It experimentally measured the evolution of mean particle size, the number density, the volume fraction of Laves-phase precipitates, the partition coefficients of W and Mo in the matrix, as well as the change of hardness. Its main conclusions were: 1) Laves-phase nucleates and grows rapidly on grain boundaries and lath boundaries within the first 1500 h of aging time; 2) The two stages characteristics and kinetics of Laves-phase nucleation and growth which were determined experimentally; 3) The coarsening of Laves-phase is much faster than that of M{sub 23}C{sub 6} carbides; 4) The precipitation of Laves-phase produces a pronounced matrix depletion of W and Mo atoms; and 5) The precipitated Laves-phase gives rise to weaker precipitation strengthening in comparison with M{sub 23}C{sub 6} carbides, and causes the loss of hardness due to the depletion of Mo and W from the solid solution. This paper contributes to the knowledge of kinetics of Laves-phase precipitation and coarsening, providing the essential information for comparative investigation of creep damage mechanisms. This paper also contributes to the understanding the creep damage broadly. - Highlights: • The characteristics of precipitation and coarsening of Laves-phase were determined. • The matrix depletion of W and Mo due to Laves-phase precipitation was quantified. • The effect of precipitated Laves-phase on the hardness was evaluated.

  14. Laves-phase evolution during aging in 9Cr-1.8W-0.5Mo-VNb steel for USC power plants

    International Nuclear Information System (INIS)

    Long term precipitation and coarsening of Laves-phase in tungsten strengthened 9% Cr steel under thermal aging at 923 K was investigated and reported in this paper. It experimentally measured the evolution of mean particle size, the number density, the volume fraction of Laves-phase precipitates, the partition coefficients of W and Mo in the matrix, as well as the change of hardness. Its main conclusions were: 1) Laves-phase nucleates and grows rapidly on grain boundaries and lath boundaries within the first 1500 h of aging time; 2) The two stages characteristics and kinetics of Laves-phase nucleation and growth which were determined experimentally; 3) The coarsening of Laves-phase is much faster than that of M23C6 carbides; 4) The precipitation of Laves-phase produces a pronounced matrix depletion of W and Mo atoms; and 5) The precipitated Laves-phase gives rise to weaker precipitation strengthening in comparison with M23C6 carbides, and causes the loss of hardness due to the depletion of Mo and W from the solid solution. This paper contributes to the knowledge of kinetics of Laves-phase precipitation and coarsening, providing the essential information for comparative investigation of creep damage mechanisms. This paper also contributes to the understanding the creep damage broadly. - Highlights: • The characteristics of precipitation and coarsening of Laves-phase were determined. • The matrix depletion of W and Mo due to Laves-phase precipitation was quantified. • The effect of precipitated Laves-phase on the hardness was evaluated

  15. Precipitation behavior of Laves phase in 10%Cr steel X12CrMoWVNbN10-1-1 during short-term creep exposure

    International Nuclear Information System (INIS)

    Research highlights: → Laves phase precipitates in steel X12 during short-term exposure of 204 h at 650 deg. C and 400 h at 600 deg. C. → Laves phase has stacking faults in it and the SAED patterns of it are characteristic of streaked. → There are two mechanisms of the nucleation and growth for Laves phase present in steel X12. → The size and the number of Laves phase are strongly dependent on temperature, but slightly on stress. → The formation of Laves phase in steel X12 is a thermodynamically possible process. - Abstract: Precipitation behavior of Laves phase in steel X12CrMoWVNbN10-1-1 during short-term (≤400 h) creep exposure was investigated using a transmission electron microscope (TEM) and an ultra high resolution thermal field emission scanning electron microscope (UHR-FESEM). The results demonstrate that Laves phase precipitates are detected in the creep specimens exposed for such a short-term of 400 h at 600 deg. C and 204 h at 650 deg. C. Stacking faults are observed in them and the selected area electron diffraction patterns of the phase are characteristic of streaked. There are two mechanisms of the nucleation and growth for Laves phase, one of which is that Laves phases occur alone on martensite lath boundaries and they are coherent with a grain but grow into the adjacent grain which has no rational orientation relationship with them. The other one is that Laves phases are formed in the regions adjacent to M23C6 particles, and then they grow at the expense of the Cr-rich M23C6 carbides in close vicinity. It is established that the former one is the dominant formation mechanism for Laves phase in steel X12CrMoWVNbN10-1-1. Laves phases prefer to locate on the prior austenite grain boundaries and the martensite lath boundaries. The mean diameter and the number density of the phase show significant change with temperature, but slightly change with stress. Moreover, it is proved that the formation of Laves phase in this steel is a

  16. Multifunctional phenomena in rare-earth intermetallic compounds with a laves phase structure: giant magnetostriction and magnetocaloric effect

    Czech Academy of Sciences Publication Activity Database

    Tereshina, I.; Cwik, J.; Tereshina, Evgeniya; Politova, G.; Burkhanov, G.; Chzhan, V.; Ilyushin, A.; Miller, M.; Zaleski, A.; Nenkov, K.; Schultz, L.

    2014-01-01

    Roč. 50, č. 11 (2014), s. 2504604. ISSN 0018-9464 Institutional support: RVO:68378271 Keywords : giant magnetostriction * Laves phase structure * magnetic anisotropy * magnetocaloric effect * rare- earth intermetallic Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.386, year: 2014

  17. High energy Compton spectroscopy and electronic structure of Laves phase ZrFe2

    Science.gov (United States)

    Bhatt, Samir; Kumar, Kishor; Arora, Gunjan; Bapna, Komal; Ahuja, B. L.

    2016-08-01

    We present the first-ever experimental Compton profile of Laves phase ZrFe2 using indigenous 20 Ci 137Cs Compton spectrometer. To annotate the experimental electron momentum density, we have calculated the theoretical Compton profiles using density functional theory (DFT) and hybridization of Hartree-Fock and DFT within linear combination of atomic orbitals (LCAO) method. The spin-polarized energy bands and density of states are computed using LCAO and full potential-linearized augmented plane wave methods. The revised Perdew-Burke-Ernzerhof functional (for solids) based theoretical profile gives a marginally better agreement with the experimental profile as compared to other approximations considered in the present work. The Fermi surface topology of ZrFe2 is explained in terms of majority- and minority-spin energy bands.

  18. Electronic structure and magnetic properties of selected lanthanide and actinide intermetallic Laves-phase alloys

    International Nuclear Information System (INIS)

    The electronic structure and magnetic properties of some yttrium and uranium Laves-phase pseudobinary alloys with 3d elements have been calculated. The calculations were done by simulating the electronic structure of the alloy by that of an ordered compound with the same stoichiometry. In general a good agreement between the experimental and theoretical magnetic moment was found, indicating that the spurious long-range order of the calculations is of minor importance. A comparison between the present supercell cluster approach and the virtual-crystal approximation for the electronic structure and cohesive properties is presented for Y(Fe0.75Co0.25)2 and U(Fe0.5Ni0.5)2

  19. Electronic properties of Laves phase ZrFe2 using Compton spectroscopy

    Science.gov (United States)

    Bhatt, Samir; Kumar, Kishor; Dashora, Alpa; Ahuja, B. L.

    2016-05-01

    First-ever experimental Compton profile of Laves phase ZrFe2, using indigenous 20 Ci 137Cs Compton spectrometer, is presented. To analyze the experimental electron momentum density, we have deduced the theoretical Compton profiles using density functional theory (DFT) and hybridization of DFT and Hartree-Fock scheme within linear combination of atomic orbitals (LCAO) method. The energy bands and density of states are also calculated using LCAO prescription. The theoretical profile based on local density approximation gives a better agreement with the experimental profile than other reported schemes. The present investigations validate the inclusion of correlation potential of Perdew-Zunger in predicting the electronic properties of ZrFe2.

  20. Precipitation of Laves phase Fe2Mo type in HSLA steel with copper addition and high content of molybdenum

    Directory of Open Access Journals (Sweden)

    S. Pytel

    2010-07-01

    Full Text Available The results of mechanical properties and microstructure of low-carbon copper bearing steel after quenching and tempering at temperaturerange of processing precipitation of particles rich in copper and particles intermetallic phase are presented in this paper. When content molybdenum increases in tempering temperature range from 550°C to 600°C that decrease of the impact energy measured at roomtemperature was observed. Microstructure analysis was conducted by transmission electron microscope (TEM and was disclosed theoccurrence of Fe2Mo Laves phase on crystallites boundaries of retained austenite. Observed sudden drop of ductility in higher-molybdenum content steels (1,88 % and 2,94 % should be connected with occurrence precipitation processes of the hard and brittle Laves phase in range of discussion tempering temperatures.

  1. Direct measurement of carbon solubility in the intermetallic (Fe,Cr)2(Mo,W) Laves phase using atom-probe field-ion microscopy

    International Nuclear Information System (INIS)

    The (Fe,Cr)2(Mo,W) Laves phase found in the studied 10.5% chromium steel, which had been creep tested for nearly 1,500 h at 600 C, contained 0.8 at.% carbon. Thus, the solubility of carbon in this phase cannot be considered to be negligible. When compared with matrix analyses of the same material in the as-tempered state, the matrix surrounding the Laves phase in the creep tested material showed a slight enrichment in carbon. Besides carbon, Laves phase was enriched in silicon (3.7 at.%) and phosphorus (0.7 at.%). Further studies of the role of these elements on the nucleation and stability of Laves phase in 9%--12% chromium steels should be performed

  2. High-temperature- and high-pressure-induced formation of the Laves-phase compound XeS2

    Science.gov (United States)

    Yan, Xiaozhen; Chen, Yangmei; Xiang, Shikai; Kuang, Xiaoyu; Bi, Yan; Chen, Haiyan

    2016-06-01

    We explore the reactivity of xenon with sulfur under high pressure, using unbiased structure searching techniques combined with first-principles calculations, which identify a stable XeS2 compound crystallized in a Laves phase with hypercoordinated (16-fold) Xe at 191 GPa and 0 K. Taking the thermal effects into account, we find that increasing the temperature could further stabilize it. The formation of XeS2 is a consequence of pressure-induced charge transfer from Xe to S atoms and the delocalization of Xe 5 p and S 3 p electrons. Meanwhile, the stabilization into a Laves phase of XeS2 is the result of delocalized chemical bonding and the need for optimum structure packing. The present discussion of the formation mechanism in XeS2 is general, and conclusions can be used to understand the formation of other Laves-phase compounds and the Xe chemistry that allows closed-shell Xe to participate in chemical reactions.

  3. Electronic band structures of AV2 (A = Ta, Ti, Hf and Nb) Laves phase compounds

    International Nuclear Information System (INIS)

    First-principles density functional calculations, using the all-electron full potential linearized augmented plane wave method, have been performed in order to investigate the structural and electronic properties for Laves phase AV2 (A = Ta, Ti, Hf and Nb) compounds. The generalized gradient approximation and the Engel-Vosko-generalized gradient approximation were used. Our calculations show that these compounds are metallic with more bands cutting the Fermi energy (EF) as we move from Nb to Ta, Hf and Ti, consistent with the increase in the values of the density of states at the Fermi level N(EF). N(EF) is controlled by the overlapping of V-p/d, A-d and A-p states around the Fermi energy. The ground state properties of these compounds, such as equilibrium lattice constant, are calculated and compared with the available literature. There is a strong/weak hybridization between the states, V-s states are strongly hybridized with A-s states below and above EF. Around the Fermi energy we notice that V-p shows strong hybridization with A-p states.

  4. Deuterium ordering in Laves phase deuteride YFe2D4.2

    Energy Technology Data Exchange (ETDEWEB)

    Proffen, Thomas Ernst [Los Alamos National Laboratory; Ropka, Joanna [UNIV OF GENEVA; Cerny, Radovan [UNIV OF GENEVA; Paul - Boncour, V [CNRS

    2009-01-01

    The structure of Laves phase deuteride YFe{sub 2}D{sub 4.2} has been investigated by synchrotron and neutron (ToF) powder diffraction experiments between 60 K and 370 K. YFe{sub 2}D{sub 4.2} crystallizes below 323K in fully ordered monoclinic structure (s.g. Pc, Z = 8, a = 5.50663(4), b = 11.4823(1), c = 9.42919(6) {angstrom}, {beta} = 122.3314(5){sup o}, V = 503.765(3) {angstrom}{sup 3} at 290K) containing 4 yttrium, 8 iron and 18 deuterium atoms. Most of D-D distances are within the precision of the diffraction experiment longer than 2.1 {angstrom}, the shortest ones are of 1.96 {angstrom}. Seven iron atoms from eight are coordinated by deuterium in a trigonal bipyramid, similar to that in TiFeD{sub 1.95-2}. The eights iron atom is coordinated by deuterium in a tetrahedral configuration. The iron coordination by deuterium, and iron-deuterium distances points to the importance of the directional bonding between iron and deuterium atoms. The lowering of crystal symmetry due to deuterium ordering occurs at much higher temperature than magnetic order, and is therefore one of the parameters which are at the origin of magnetic transition at lower temperatures.

  5. Laves phases and new compounds based on magnesium for hydrogen storage application

    International Nuclear Information System (INIS)

    This work deals with the study of ternary compounds rare earth - magnesium - nickel used for hydrogen storage. All the compounds are prepared by fusion and by mechanical alloying method. The compounds YNi4-xAlxMg, derived from the cubic Laves phases have been studied in the first part. It reacts reversibly towards hydrogen at atmospheric pressure and room temperature. The structural behaviour during the hydrogen sorption has been studied by in situ XRD. The compound remains cubic with a decrease of the crystallinity. This study is completed by the study of compounds: (i) rich in rare earth (e.g. Gd4NiMg) that absorb hydrogen at room temperature but irreversibly. Structures of both the intermetallic and the hydride have been determined. The decomposition of the hydride at temperature higher than 90 C is also explained. (ii) rich in magnesium. A new compounds with a formulation closed to Mg77Gd9Ni14.5 has been identified and it crystallized with a cubic faces centred structure. (author)

  6. Effect of alloying with Ti, V, Mn on the electrochemical properties of Zr-Cr-Ni based Laves phase and metal hydride electrodes

    International Nuclear Information System (INIS)

    The main phase in Zr(CrxNi1-x)2 Laves phase alloys (0.20≤x≤0.60) changes from C15 to C14 at x=0.45-0.50. Electrodes with Cr content in the range 0.30≤x≤0.50 have favorable electrochemical capacities. The substitution effect of Cr or Ni by V or Mn in the form of Zr(CrxMyNi2-x-y) (M=V or Mn, x + y = 0.7-1.2) on the electrochemical discharge capacity was also studied. The alloys with x + y = 0.7-1.0/AB2 formula have larger hydrogen storage and electrochemical discharge capacities. When Ti is used to partly substitute Zr in TiyZr1-yM2 (y = 0.0-0.3) alloys, the plateau pressure of the hydride tends to increase with increasing y, however, its electrochemical capacity decreases as well due to lower reversible hydrogen storage density. The electrochemical cycling deterioration increases with increasing Ti content. Electrodes with no Ti or very low Ti content preserve 86% of their discharge capacities after 820 cycles under 65% depth of discharge, exhibiting excellent electrochemical stability. (orig.)

  7. The magnetic properties of the Laves-phase system Dy(Co1-xAlx)2

    International Nuclear Information System (INIS)

    Dy(Co1-xAlx)2 alloys exhibit interesting magnetic properties because of the differing nature of the magnetism (localized and band) of their constituents. They crystallize in the Laves-phase MgCu2 crystal structure. Magnetic measurements were performed at temperatures down to 4.2 K and in magnetic fields up to 15 T. The experimental results are compared with theoretical calculations based on the ab initio tight-binding version of the linear muffin-tin orbital method (TB-LMTO). Spin-polarized calculations were performed for experimental lattice constants obtained from X-ray measurements. (orig.)

  8. Magnetostructural phase transitions and magnetocaloric effect in Tb-Dy-Ho-Co-Al alloys with a Laves phase structure

    Science.gov (United States)

    Tereshina, I. S.; Chzhan, V. B.; Tereshina, E. A.; Khmelevskyi, S.; Burkhanov, G. S.; Ilyushin, A. S.; Paukov, M. A.; Havela, L.; Karpenkov, A. Yu.; Cwik, J.; Koshkid'ko, Yu. S.; Miller, M.; Nenkov, K.; Schultz, L.

    2016-07-01

    The influence of simultaneous substitution within the rare earth (R) and Co sublattices on the structural, magnetic, and magnetocaloric properties of the Laves phase RCo2-type compounds is studied. Main attention is devoted to the studies of the magnetostructural phase transitions and the transition types with respect to the alloy composition. Multicomponent alloys Tbx(Dy0.5Ho0.5)1-xCo2 and Tbx(Dy0.5Ho0.5)1-xCo1.75Al0.25 were prepared with the use of high purity metals. Majority of the Tbx(Dy0.5Ho0.5)1-xCo2 alloys exhibit magnetic transitions of the first-order type and a large magnetocaloric effect. The substitution of Al for Co in Tbx(Dy0.5Ho0.5)1-xCo2 increases the Curie temperature (TC) but changes the transition type from first-to the second-order. The discussion of the physical mechanisms behind the observed phenomena is given on the basis of the first principles electronic-structure calculations taking into account both the atomic disorder and the magnetic disorder effects at finite temperatures. The advantage of Al-containing materials is that sufficiently high magnetocaloric effect values are preserved at T > TC.

  9. Determination of site occupancy of additives X (X = V, Mo, W and Ti) in the Nb-Cr-X Laves phase by ALCHEMI

    International Nuclear Information System (INIS)

    Atom location by channeling enhanced microanalysis (ALCHEMI) was carried out to investigate the site occupancy of additives X (X = V, Mo, W and Ti) in the Nb-Cr-X Laves phase. In order to make clear the detailed substitutional behavior of the additives, specimens with different compositions were prepared for each system. In the C15 structure of the Laves phase, fairly strong electron channeling effects were observed under two planar channeling conditions where the incident electron beams were nearly parallel to the (400) and (220) planes. It was shown that V prefers the Cr site, while Mo, W and Ti preferentially occupy the Nb site

  10. Re-Modelling of Laves Phases in the Cr-Nb and Cr-Ta Systems Using First-Principles Results

    Czech Academy of Sciences Publication Activity Database

    Pavlů, Jana; Vřešťál, Jan; Šob, Mojmír

    2009-01-01

    Roč. 33, č. 1 (2009), s. 179-186. ISSN 0364-5916 R&D Projects: GA ČR GA106/07/1078 Institutional research plan: CEZ:AV0Z20410507 Keywords : ab initio calculations * Laves phases * phase diagrams Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.904, year: 2009

  11. Unusual 5f magnetism in the U2Fe3Ge ternary Laves phase: a single crystal study

    International Nuclear Information System (INIS)

    Magnetic properties of the intermetallic compound U2Fe3Ge were studied on a single crystal. The compound crystallizes in the hexagonal Mg2Cu3Si structure, an ordered variant of the MgZn2 Laves structure (C14). U2Fe3Ge displays ferromagnetic order below the Curie temperature TC = 55 K and presents an exception to the Hill rule, as the nearest inter-uranium distances do not exceed 3.2 Å. Magnetic moments lie in the basal plane of the hexagonal lattice, with the spontaneous magnetic moment Ms = 1.0 μB/f.u. at T = 2 K. No anisotropy within the basal plane is detected. In contrast to typical U-based intermetallics, U2Fe3Ge exhibits very low magnetic anisotropy, whose field does not exceed 10 T. The dominance of U in the magnetism of U2Fe3Ge is suggested by the 57Fe Mössbauer spectroscopy study, which indicates very low or even zero Fe moments. Electronic structure calculations are in agreement with the observed easy-plane anisotropy but fail to explain the lack of an Fe contribution to the magnetism of U2Fe3Ge.

  12. Effect of hydrostatic pressure on the elastic properties of some rare earth-iron Laves phase compounds

    International Nuclear Information System (INIS)

    The pressure dependence of the Young's and shear moduli of RFe2(R=Sm, Gd, Tb, Dy, Ho and Er) has been determined at room temperature in the pressure range between 0 and 1 GPa. The elastic moduli of GdFe2, DyFe2, HoFe2 and ErFe2 show a moderate increase with increasing hydrostatic pressure. However, the elastic moduli of SmFe2 and TbFe2 exhibit an initially drastic increase followed by a high, and linear, pressure dependence. From the pressure and temperature derivatives of the elastic moduli of these RFe2 Laves phase compounds the equations of state and the Grueneisen parameters have been derived. The variation of the elastic properties with hydrostatic pressure is compared with the effect of magnetic fields. The anomalous behavior of SmFe2 and TbFe2 is discussed. (author)

  13. Lightweight Intermetallics with Laves Structures as Potential Hydrogen Storage Materials

    Science.gov (United States)

    Billet, Beau Austin

    Hydrogen storage was identified by the US Department of Energy as a "grand challenge" for the implementation of hydrogen-powered fuel cell vehicles for reduced CO2 emissions from transportation vehicles. None of the hydrogen storage options currently developed can satisfy the high gravimetric, volumetric and system design requirements. Intermetallic compounds with Laves structures in the formula of AB2 have long been known to store hydrogen in their interstitial sites to serve as reversible hydrogen storage materials (A and B are metallic elements). They have the potential to be hydrided to a maximum of ~ AB2H6 due to the impeding H-H interactions at neighboring interstitial sites. To achieve the highest weight percent of hydrogen storage in AB2H6, the lowest combined atomic weight of AB2 is required. The CaLi2 compound is the lightest known Laves phase, but it could not maintain its Laves structure when it was hydrided. Existing work of Akiba's group showed that a ternary Laves phase CaLi1.8Mg0.2 could be hydrided to form a hydrogenated Laves phase, but the absorbed hydrogen could not be released for reversible storage. Substitutions (Ca,X)Li1.8Mg0.2 are explored in the present study to see whether heavier elements [X = Sr, Ba and Ce] in small quantities can make the lightweight Laves compounds reversibly store hydrogen. Induction melting was successful in obtaining the desired Laves phases. The base system, CaLi1.8Mg0.2, formed a single phase, consistent with the literature result. Both Ca0.9Ba0.1Li 1.8Mg0.2 and Ca0.9Ce0.1Li1.8Mg 0.2 also formed a single-phase C14 Laves, whereas both Ca0.9Sr 0.1Li1.8Mg0.2 and Ca0.8Sr0.2Li 1.8Mg0.2 formed two seperature Laves phases with the same crystal structure, indicating a phase separation. The Ca0.8Ba 0.2Li1.8Mg0.2 composition completely lost the Laves-phase structure, forming CaLi2, CaMg2, BaLi 4 and Ca. All compounds tested at temperatures from 25 °C to 150 °C show the characteristic "plateau" behavior in the pressure

  14. Importance of magnetic effects on structural properties in Al- and Si- substituted laves phases Fe2Nb and Fe2W

    International Nuclear Information System (INIS)

    Laves phases are promising candidates for the design of new steels with superior mechanical strength. Here we study systematically thermodynamic, structural and magnetic properties in Al- and Si- substituted Laves phase compounds Fe2Nb and Fe2W using first-principles density functional methods. Spin polarized calculations predict that substituting Al atoms for Fe atoms in Fe2Nb is energetically more favorable than substituting Al atoms for Nb atoms. Furthermore, they show that this leads to a significant increase of the lattice constant along the a axis. To investigate the effects of magnetism, non-magnetic calculations are carried out for the same Fe-Nb-Al compounds. Our results show that the inclusion of magnetism is crucial to accurately reproduce experimental data. Based on this insight, theoretical predictions for ternary alloys Fe-Nb-Si, Fe-W-Al and Fe-W-Si are presented.

  15. Synthesis of Iron-Based Laves Phase Containing Praseodymium Magnetostrictive Materials

    Institute of Scientific and Technical Information of China (English)

    Liu Heyan; Dong Bin; Li Songtao; Meng Xiangxi; Gao Jianbo; Qu Jingping; Li Yangxian

    2007-01-01

    The synthesis and magnetostriction of PrxTb1-xFe2, PrxTb1-xFe2B0.2 and PrxTb1-x(Fe0.6Co0.4)2 alloys were investigated in this study. The addition of boron or cobalt atom in PrxTb1-xFe2 could effectively prevent the formation of non-cubic phases, and Pr concentration limit was successfully increased from 0.2 to 0.4. X-ray step scanning for the PrxTb1-xFe2B0.2 and PrxTb1-x(Fe0.6Co0.4)2 alloys showed that PrFe2 possessed a large spontaneous magnetostriction λ111.

  16. Collapse of the magnetic moment under pressure of AFe2 (A=Y, Zr, Lu and Hf) in the cubic Laves phase

    Science.gov (United States)

    Zhang, Wenxu; Zhang, Wanli

    2016-04-01

    The electronic structures of four Laves phase iron compounds (e.g. YFe2, ZrFe2, LuFe2 and HfFe2) have been calculated with a state-of-the-art full potential electronic structure code. Our theoretical work predicted that the magnetic moments collapse under hydrostatic pressure. This feature is found to be universal in these materials. Its electronic origin is provided by the sharp peaks in the density of states near the Fermi level. It is shown that a first order quantum phase transition can be expected under pressure in Y(Zr, or Lu)Fe2, while a second order one in HfFe2. The bonding characteristics are discussed to elucidate the equilibrium lattice constant variation. The large spontaneous volume magnetostriction gives one of the most important characteristics of these compounds. Invar anomalies in these compounds can be partly explained by the current work when the fast continuous magnetic moment decrease with the decrease of the lattice constant was properly considered. This work may be as a first insight into the rich world of quantum phase transition and Invar mechanism in these Laves phase compounds.

  17. Effect of Laves Phase on High-Temperature Deformation and Microstructure Evolution in an 18Cr-2Mo-0.5Nb Ferritic Stainless Steel

    Science.gov (United States)

    Ikeda, Ken-ichi; Yamoah, Nana Kwame Gyan; Reynolds, William T.; Hamada, Jun-ichi; Murayama, Mitsuhiro

    2015-08-01

    Niobium-containing ferritic stainless steels are finding new applications in automotive exhaust components because of their oxidation resistance, thermal fatigue resistance, and high-temperature strength. The mechanical behavior of Nb-containing ferritic steels at service temperatures of 973 K (700 °C) and higher results from the convolution of dynamic microstructural changes including precipitation, precipitate coarsening, strain hardening, recovery, and recrystallization. The relative contributions of these competing processes have yet to be clarified. In this study, the high-temperature flow strength of an 18Cr-2Mo-0.5Nb ferritic stainless steel (SUS 444) was correlated with microstructure under different strain and initial precipitate distributions to clarify the relative role of the strengthening and softening processes. High-temperature tensile tests at 1023 K (750 °C) of un-aged (initial microstructure is precipitate-free) and pre-aged (initial microstructure contains precipitates) samples were carried out and transmission electron microscopy was used to assess dislocation distributions and precipitate morphology. The difference in the stress-strain curves between un-aged and pre-aged samples was drastic; the yield strength of the un-aged sample was twice that of the pre-aged sample, and the un-aged sample exhibits a noticeable yield drop. Transmission electron microscopy revealed a Laves phase nucleated and grew during the high-temperature tensile test in the un-aged sample and the majority of the precipitates in the pre-aged sample were the same Laves phase. Furthermore, a strain effect on precipitate growth was recognized in un-aged and pre-aged conditions by comparing grip (no strain) and gage (strained) sections of tensile samples. The dominant strengthening contribution in un-aged samples is initially the precipitate shearing mechanism and it changes to Orowan strengthening beyond the ultimate tensile strength, whereas the dominant contribution in

  18. Phases and phase equilibria in the Fe-Al-Zr system

    International Nuclear Information System (INIS)

    Isothermal sections at 800, 1000, and 1150 C as well as a tentative partial liquidus surface of the ternary Fe-Al-Zr system were established by means of electron-probe microanalysis, X-ray diffraction, differential thermal analysis, and light-optical as well as scanning electron microscopy. The most prominent features of the ternary phase diagram are the extended homogeneity ranges of the Laves phases. By continuous substitution of Fe by Al, the structure changes three times starting from the cubic C15 structure of Fe2Zr to hexagonal C14 (λ1) back to cubic C15 (λ2) and again to hexagonal C14 (Al2Zr). The various Laves phase fields are separated by very small two-phase fields. Besides the Laves phases λ1 and λ2, three more ternary intermetallic phases were found, whose homogeneity ranges have been determined for the first time. In addition, new results concerning the homogeneity ranges of intermetallic phases in the binary subsystems Fe-Al and Al-Zr are reported. The solubilities of the third components in the binary phases are found to be generally very low with the exception of the Laves phases. As a consequence, extended two-phase fields between the Fe(Al) solid solution and Laves phase or between Fe(Al) solid solution and the ternary ThMn12-type phase τ1 are formed. (orig.)

  19. Structure and hydrogen storage properties of the hexagonal Laves phase Sc(Al{sub 1-x}Ni{sub x}){sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Sahlberg, Martin, E-mail: Martin.sahlberg@kemi.uu.se [Department of Chemistry, The Angstroem Laboratory, Uppsala University, Box 538, SE-751 21 Uppsala (Sweden); Angstroem, Jonas, E-mail: jonas.angstrom@kemi.uu.se [Department of Chemistry, The Angstroem Laboratory, Uppsala University, Box 538, SE-751 21 Uppsala (Sweden); Zlotea, Claudia, E-mail: claudia.zlotea@icmpe.cnrs.fr [Chimie Metallurgique des Terres Rares, Institut de Chimie et des Materiaux de Paris Est, UMR 7182, CNRS, 2-8 rue Henri Dunant, 94320 Thiais Cedex (France); Beran, Premysl, E-mail: pberan@ujf.cas.cz [Nuclear Physics Institute, Academy of Sciences of the Czech Republic, 25068 Rez (Czech Republic); Latroche, Michel, E-mail: michel.latroche@glvt-cnrs.fr [Chimie Metallurgique des Terres Rares, Institut de Chimie et des Materiaux de Paris Est, UMR 7182, CNRS, 2-8 rue Henri Dunant, 94320 Thiais Cedex (France); Pay Gomez, Cesar, E-mail: Cesar.paygomez@kemi.uu.se [Department of Chemistry, The Angstroem Laboratory, Uppsala University, Box 538, SE-751 21 Uppsala (Sweden)

    2012-12-15

    The crystal structures of hydrogenated and unhydrogenated Sc(Al{sub 1-x}Ni{sub x}){sub 2} Laves phases have been studied by combining several diffraction techniques and it is shown that hydrogen is situated interstitially in the A{sub 2}B{sub 2}-sites, which have the maximum number of scandium neighbours. The hydrogen absorption/desorption behaviour has also been investigated. It is shown that a solid solution of hydrogen forms in the mother compound. The hydrogen storage capacity exceeds 1.7 H/f.u. at 374 K, and the activation energy of hydrogen desorption was determined to 4.6 kJ/mol H{sub 2}. It is shown that these compounds share the same local coordination as Frank-Kasper-type approximants and quasicrystals, which opens up the possibility of finding many new hydride phases with these types of crystal structures. - Graphical abstract: The structure of ScNiAlDx, Sc atoms are shown in purple and Ni/Al atoms in blue and the iso-surfaces of deuterium in yellow. Revealed from refinements of neutron powder diffraction data. Highlights: Black-Right-Pointing-Pointer The crystal structure of ScNiAl and ScNiAlDx is reported. Black-Right-Pointing-Pointer We show the hydrogen storage properties of Sc(Al{sub 1-x}Ni{sub x}){sub 2}. Black-Right-Pointing-Pointer We discuss the possibility to store hydrogen in quasicrystals.

  20. Nuclear magnetic resonance studies of hydrogen motion in nanostructured Laves-phase hydrides ZrCr2Hx and TaV2Hx

    Science.gov (United States)

    Soloninin, A. V.; Buzlukov, A. L.; Skripov, A. V.; Aleksashin, B. A.; Tankeyev, A. P.; Yermakov, A. Ye; Mushnikov, N. V.; Uimin, M. A.; Gaviko, V. S.

    2008-07-01

    In order to study the mobility of hydrogen in nanostructured Laves-phase hydrides, we have measured the proton nuclear magnetic resonance (NMR) spectra and the proton spin-lattice and spin-spin relaxation rates in two nanostructured systems prepared by ball milling: ZrCr2H3 and TaV2H1+δ. The proton NMR measurements have been performed at the resonance frequencies of 14, 23.8 and 90 MHz over the temperature ranges 11-424 K (for coarse-grained samples) and 11-384 K (for nanostructured samples). Hydrogen mobility in the ball-milled ZrCr2H3 is found to decrease strongly with increasing milling time. The experimental data suggest that this effect is related to the growth of the fraction of highly distorted intergrain regions where H mobility is much lower than in the crystalline grains. For the nanostructured TaV2H1+δ system, the ball milling is found to lead to a slight decrease in the long-range H mobility and to a suppression of the fast localized H motion in the crystalline grains.

  1. Effect of Ti/Cr content on the microstructures and hydrogen storage properties of Laves phase-related body-centered-cubic solid solution alloys

    International Nuclear Information System (INIS)

    Highlights: • Influences of Ti/Cr to BCC to hydrogen storage properties were reported. • A new activation using hydrogen pressure at 5 MPa was developed. • A discharge capacity of 463 mA h g−1 was reported on a C14(36%)/BCC(64%) alloy. • Increase in Ti/Cr increases storage capacity and decreases high-rate performance. • The high-rate performance was dominated by the surface reaction. - Abstract: A series of BCC/C14 mixed phase alloys with the chemical composition of Ti13.6+xZr2.1V44Cr13.2−xMn6.9Fe2.7Co1.4Ni15.7Al0.3, x = 0, 2, 4, 6, 8, 10, and 12, was fabricated, and their structural, gaseous phase and electrochemical hydrogen storage properties were studied. Raising the maximum pressure for measuring the gaseous hydrogen storage capacity allowed these alloys to reach full activation, and the maximum discharge capacities ranged from 375 to 463 mA h g−1. As the Ti/Cr ratio in the alloy composition increased, the maximum gaseous hydrogen storage capacity improved due to the expansion in both BCC and C14 unit cells. However, reversibility decreased due to the higher stability of the hydride phase, as indicated by the lower equilibrium pressures measured for these alloys. As with most other metal hydride alloys, the electrochemical capacities measured at 50 and 4 mA g−1 fell between the boundaries set by the maximum and reversible gaseous hydrogen storage capacities. The poorer high-rate dischargeability observed with higher Ti/Cr ratios was attributed to the lower surface exchange current (less catalytic). Two other negative impacts observed with higher Ti/Cr ratios in the alloy composition are poorer cycle stability and lower open-circuit voltage

  2. Dating by C14

    International Nuclear Information System (INIS)

    This report summarizes the results of studies made with two assemblies for dating geological and archaeological objects with C14. The advantages and drawbacks of three ways of determining C14 activity in solid, liquid and gaseous substances are discussed. Data are given of the chemical preparation and cleaning of the gaseous carbon compounds ethane, acetylene and carbon dioxide, and the calculation of their C14 activity. The report assesses the mistakes that can be made in determining age by C14, and gives data for geological and archaeological objects in the Soviet Union. (author)

  3. Precipitation of Laves phase Fe2Mo type in HSLA steel with copper addition and high content of molybdenum

    OpenAIRE

    Pytel, S.; Miernik, K.; R. Bogucki

    2010-01-01

    The results of mechanical properties and microstructure of low-carbon copper bearing steel after quenching and tempering at temperaturerange of processing precipitation of particles rich in copper and particles intermetallic phase are presented in this paper. When content molybdenum increases in tempering temperature range from 550°C to 600°C that decrease of the impact energy measured at roomtemperature was observed. Microstructure analysis was conducted by transmission electron microscope (...

  4. Effect of Ti/Cr content on the microstructures and hydrogen storage properties of Laves phase-related body-centered-cubic solid solution alloys

    Energy Technology Data Exchange (ETDEWEB)

    Young, K., E-mail: kwo.young@basf.com [BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309 (United States); Wong, D.F. [BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309 (United States); Department of Chemical Engineering and Materials Science, Wayne State University, MI 48202 (United States); Wang, L. [BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309 (United States)

    2015-02-15

    Highlights: • Influences of Ti/Cr to BCC to hydrogen storage properties were reported. • A new activation using hydrogen pressure at 5 MPa was developed. • A discharge capacity of 463 mA h g{sup −1} was reported on a C14(36%)/BCC(64%) alloy. • Increase in Ti/Cr increases storage capacity and decreases high-rate performance. • The high-rate performance was dominated by the surface reaction. - Abstract: A series of BCC/C14 mixed phase alloys with the chemical composition of Ti{sub 13.6+x}Zr{sub 2.1}V{sub 44}Cr{sub 13.2−x}Mn{sub 6.9}Fe{sub 2.7}Co{sub 1.4}Ni{sub 15.7}Al{sub 0.3}, x = 0, 2, 4, 6, 8, 10, and 12, was fabricated, and their structural, gaseous phase and electrochemical hydrogen storage properties were studied. Raising the maximum pressure for measuring the gaseous hydrogen storage capacity allowed these alloys to reach full activation, and the maximum discharge capacities ranged from 375 to 463 mA h g{sup −1}. As the Ti/Cr ratio in the alloy composition increased, the maximum gaseous hydrogen storage capacity improved due to the expansion in both BCC and C14 unit cells. However, reversibility decreased due to the higher stability of the hydride phase, as indicated by the lower equilibrium pressures measured for these alloys. As with most other metal hydride alloys, the electrochemical capacities measured at 50 and 4 mA g{sup −1} fell between the boundaries set by the maximum and reversible gaseous hydrogen storage capacities. The poorer high-rate dischargeability observed with higher Ti/Cr ratios was attributed to the lower surface exchange current (less catalytic). Two other negative impacts observed with higher Ti/Cr ratios in the alloy composition are poorer cycle stability and lower open-circuit voltage.

  5. Synthesis, phase transformation, and hydrogen storage properties of ball-milled TiV{sub 0.9}Mn{sub 1.1}

    Energy Technology Data Exchange (ETDEWEB)

    Huot, J. [Physics Department and Institut de Recherche sur l' Hydrogene, Universite du Quebec a Trois-Rivieres, 3351, Boul. Des Forges, Trois-Rivieres, Que. G9A 5H7 (Canada)], E-mail: jacques.huot@uqtr.ca; Enoki, H.; Akiba, E. [Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology, AIST Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan)

    2008-04-03

    The milling of body centered cubic (BCC) Laves phase-related alloy of composition TiV{sub 0.9}Mn{sub 1.1} was performed using a planetary mill under inert atmosphere. Starting materials were arc-melted alloys and elements mixtures. The arc-melted alloy consisted of two phases: the C14 Laves phase and a BCC solid solution. It was found that milling of the arc-melted alloy resulted in the disappearance of the C14 Laves phase and the formation of a face centered cubic (FCC) solid solution phase in addition to the BCC solid solution. Milling the pure elements also produced a mixture of FCC and BCC solid solution phases. Extensive milling resulted in a total loss of hydrogen capacity.

  6. Ab initio study of structural stability and electronic properties of Ti{sub 1-x}Mg{sub x}Cr{sub 2} and TiMg{sub x}Cr{sub 2-x} laves phase

    Energy Technology Data Exchange (ETDEWEB)

    Sari, A., E-mail: sari.aouatef@yahoo.fr; Merad, G. [Unité de Recherché Matériaux et Energies Renouvelables. Division d’Etudes et de Prédiction des Matériaux. Université Abou Bekr Belkaid. Tlemcen. Algerie (Algeria)

    2015-03-30

    The structural stability and electronic properties of TiMgCr{sub 2} laves phase have been calculated and compared. It is found that Mg prefer to substitutes titanium than chromium. The values of entalpies of formation show that Ti{sub 1-x}Mg{sub x}Cr{sub 2} may exist for only one concentration x=0.125 and the more favorable alloy is Ti{sub 0.875}Mg{sub 0.125}Cr{sub 2}. For TiCr{sub 2}, the optimized structural parameters were in good agreement with experimental values, while for TiMgCr{sub 2}, there is not experimental data. The electronic densities of states (DOS) are given and the nature of bonds are also discussed.

  7. Photo-Induced Phase Transitions to Liquid Crystal Phases: Influence of the Chain Length from C8E4 to C14E4

    Directory of Open Access Journals (Sweden)

    Simone Techert

    2009-09-01

    Full Text Available Photo-induced phase transitions are characterized by the transformation from phase A to phase B through the absorption of photons. We have investigated the mechanism of the photo-induced phase transitions of four different ternary systems CiE4/alkane (i with n = 8, 10, 12, 14; cyclohexane/H2O. We were interested in understanding the effect of chain length increase on the dynamics of transformation from the microemulsion phase to the liquid crystal phase. Applying light pump (pulse/x-ray probe (pulse techniques, we could demonstrate that entropy and diffusion control are the driving forces for the kind of phase transition investigated.

  8. Photo-induced phase transitions to liquid crystal phases: Influence of the chain length from C8E4 to C14E4.

    OpenAIRE

    Simone Techert; Wilson Quevedo; Gerhard Busse; Marcel Petri

    2009-01-01

    Photo-induced phase transitions are characterized by the transformation from phase A to phase B through the absorption of photons. We have investigated the mechanism of the photo-induced phase transitions of four different ternary systems CiE4/alkane (i) with n = 8, 10, 12, 14; cyclohexane/H2O. We were interested in understanding the effect of chain length increase on the dynamics of transformation from the microemulsion phase to the liquid crystal phase. Applying light pump (pulse)/x-ray pro...

  9. Effects of La-addition to the structure, hydrogen storage, and electrochemical properties of C14 metal hydride alloys

    International Nuclear Information System (INIS)

    Highlights: • La addition to AB2 alloys promotes formation of LaNi phase. • LaNi phase facilitates formation and high-rate operation by increasing surface area. • LaNi phase causes pulverization and degrades the cycle stability. • -40 °C low temperature was much improved with La-addition. - Abstract: The structure of a series AB2 metal hydride alloys, in which La substitutes for Zr (Ti12Zr22.8−xV10Cr7.5Mn8.1Co7.0Ni32.2LaxAl0.4, x = 0 to 5), is studied and correlated to various hydrogen storage properties in both gaseous phase and electrochemical systems. La, instead of entering the main Laves phase, forms a LaNi secondary phase which has very limited solubility with other elements. This phase improves activation of both capacity and high-rate dischargeability through a dramatic increase in surface area due to pulverization. The presence of LaNi phase also improves the high-rate dischargeability, facilitating the bulk diffusion of protons through synergetic effects with the main Laves phase. La-content in the alloys also suppresses the TiNi secondary phase due to competition of Ni with the LaNi phase. The lattice constants and unit cell volume of the main C14 phase decreases as more Zr (relatively large) is substituted out, which leads to a less stable hydride with higher equilibrium plateau pressure, higher ΔH, and lower hydrogen storage capacity. With the addition of La in the alloy samples, C14 and LaNi phase abundances increase while C15 and TiNi phase abundances decrease. At −40 °C, the charge-transfer resistance of the La-containing alloys decreases as a result of increased catalytic ability in the main phase. The lowest overall charge-transfer resistance obtained from electrochemical impedance spectroscopy analysis measured at −40 °C is 11 Ω g

  10. Magnetic percolation and inequivalence of Fe sites in YFex Co2-x (x = 0.03 and 1) Laves phase compounds

    International Nuclear Information System (INIS)

    YCo2 compound is an exchange-enhanced Pauli paramagnet on the verge of being magnetic. Topological or chemical disorder can induce in it ferromagnetic long-range ordering. The influence of Fe substitution and quenched-in topological disorder on the magnetic properties of YFe0.03Co1.97 and YFeCo is studied. Structural and magnetic properties of these compounds are analyzed by means of X-ray diffraction, vibrating sample magnetometry, Moessbauer spectroscopy and AC magnetic susceptibility measurements. All samples crystallize in cubic MgCu2-type phase with lattice constant changing from 7.223 Aa for YCo2 through 7.221 Aa for YFe0.03Co1.97 to 7.313 Aa for YFeCo. Fe atoms are responsible for stabilization of magnetic moments on Co, and mictomagnetism is observed in YFe0.03Co1.97 sample. Upon further substitution, as in YFeCo, long-range ordering appears. The Moessbauer spectra permitted distinction between two magnetically inequivalent Fe sites, as reported earlier for YFe2. (orig.)

  11. Processing ix spent resin waste for C-14 isotope recovery

    International Nuclear Information System (INIS)

    /m3 for the Moderator spent resins generated by CANDU reactors. For an estimated average C-14 activity level of 100 Ci/m3, a total of 400 Ci of C-14 can be produced each year. Based on the current market value of the C-14 isotope, the cost of the demonstration plant can be recovered in less than two years. Upon successful demonstration, the process can be scaled up. The volume of resin wastes produced by the stations can readily supply a full scale production of 2000 Ci or more per annum. Several alternative routes have been considered for this process which include: thermal stripping vs. acid stripping of the spent resins, laser enrichment vs. cryogenic distillation for the enrichment of the gaseous intermediate product, and direct gas phase reaction vs. liquid phase ionic precipitation of the final product. Analysis of the experimental results obtained at Ontario Hydro Research Division and also those reported in the literature has led to the selection of the following process: The C-14 is first removed by acid stripping the resins to form carbon dioxide. The gas is then separated from the carrier gas and converted by reaction with zinc to carbon monoxide, which is cryogenically distilled. Essentially pure C-14 monoxide is obtained and oxidized to produce C-14 dioxide. The gas is then reacted with a suitable hydroxide to produce the desired carbonate product

  12. New Phase in the System Uranium-Molybdenum-Silicon

    International Nuclear Information System (INIS)

    During the investigation of the ternary system uranium-molybdenum-silicon, a new phase with the composition U4Mo5-Si3 was formed. Structure determination exclusively based on the powder data showed that the particular phase belongs to the hexagonal system. Space group P6/mmc or one of the sub-groups is indicated. Unit cell dimensions were found to be a = 5.370A, c = 8 . 582A. A comparison of calculated and observed intensities shows close resemblance to the structure of the Laves phases of the C14-type. (author)

  13. The effect of hydrogen absorption on the structural, electronic and magnetic properties of the C15 Friauf-Laves phase compounds CeFe{sub 2}, CeRu{sub 2} and LaRu{sub 2} : an x-ray absorption spectroscopy (XAS) study

    Energy Technology Data Exchange (ETDEWEB)

    Chaboy, J.; Garcia, J. [CSIC-Univ., Zaragoza (Spain). Inst. de Ciencia de Materiales de Aragon ICMA; Marcelli, A. [INFN, Laboratori Nazionali di Frascati, Rome (Italy)

    1995-08-01

    An x-ray absorption spectroscopy (XAS) investigation of the structural changes occurred upon hydriding in the Friauf-Laves phase compounds CeFe{sub 2}, CeRu{sub 2}and LaRu{sub 2} compounds is presented. The analysis of the extended x-ray absorption spectroscopy (EXAFS) spectra at the L-edges of the rare-earth and at the Fe K-edge indicates that the hydrogenation process leads to the suppression of the long-range crystalline order in all the hydride derivates investigated, as well as the different influence of H{sub 2} in both the rare earth and transition metal sublattices. The correlation between the structural and magnetic changes induced by the hydrogen in the lost matrix is discussed in terms of the modification of the electronic properties, i.e., intermediate-valence of Ce, and of the hybridization between the transition metal and rare-earth.

  14. Determination of the Nb-Cr-Si phase diagram using diffusion multiples

    International Nuclear Information System (INIS)

    A high-efficiency diffusion-multiple approach was employed to determine the phase diagram of the Nb-Cr-Si ternary system which is critical for the design of niobium silicide-based in situ composites. These composites have high potential as a replacement for Ni-base superalloys for jet engine applications. The formation of the Nb(Cr,Si)2 Laves phase is beneficial to the high oxidation resistance of the composites and the Nb-Cr-Si system serves as the base for understanding the Laves phase formation. The results clearly demonstrate the applicability of the diffusion-multiple approach in determining such complex phase diagrams as Nb-Cr-Si which contains 14 phases. Two isothermal sections at 1000 and 1150 deg. C were constructed from the results obtained from diffusion multiples using scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and electron backscatter diffraction (EBSD). Three ternary compounds, CrNbSi, (Cr,Nb)6Si5 and (Cr,Nb)11Si8, were observed at both temperatures, and the C14 Laves phase of the Cr-Nb binary system was stabilized by Si to lower temperatures

  15. Study of fatigue and fracture behavior of NbCr{sub 2}-based alloys: Phase stability in Nb-Cr-Ni ternary system

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, J.H.; Liaw, P.K. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering; Liu, C.T. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

    1997-12-01

    Phase stability in a ternary Nb-Cr-Ni Laves phase system was studied in this paper. Their previous study in NbCr{sub 2}-based transition-metal Laves phases has shown that the average electron concentration factor, e/a, is the dominating factor in controlling the phase stability of NbCr{sub 2}-based Laves phases when the atomic size ratios are kept identical. Since Ni has ten out-shell electrons, the substitution of Ni for Cr in NbCr{sub 2} will increase the average electron concentration of the alloy, thus leading to the change of the crystal structures from C15 to C14. In this paper, a number of pseudo-binary Nb(Cr,Ni){sub 2} alloys were prepared, and the crystal structures of the alloys after a long heat-treatment at 1000 C as a function of the Ni content were determined by the X-ray diffraction technique. The boundaries of the C15/C14 transition were determined and compared to their previous predictions. It was found that the electron concentration and phase stability correlation is obeyed in the Nb-Cr-Ni system. However, the e/a ratio corresponding to the C15/C14 phase transition was found to move to a higher value than the predicted one. The changes in the lattice constant, Vickers hardness and fracture toughness were also determined as a function of the Ni content, which were discussed in light of the phase stability difference of the alloys.

  16. Effects of Nd-addition on the structural, hydrogen storage, and electrochemical properties of C14 metal hydride alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wong, D.F. [BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309 (United States); Department of Chemical Engineering, Wayne State University, Detroit, MI 48202 (United States); Young, K., E-mail: kwo.young@basf.com [BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309 (United States); Department of Chemical Engineering, Wayne State University, Detroit, MI 48202 (United States); Nei, J.; Wang, L. [BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309 (United States); Ng, K.Y.S. [Department of Chemical Engineering, Wayne State University, Detroit, MI 48202 (United States)

    2015-10-25

    Nd-addition to the AB{sub 2}-based alloy Ti{sub 12}Zr{sub 22.8−x}V{sub 10}Cr{sub 7.5}Mn{sub 8.1}Co{sub 7.0}Ni{sub 32.2}Al{sub 0.4}Nd{sub x} is studied for its effects on the structure, gaseous-phase hydrogen storage, and electrochemical properties. This study follows a series of Cu, Mo, Fe, Y, Si, and La doping studies in similar AB{sub 2}-based alloys. Limited solubility of Nd in the main Laves phase promotes the formation of secondary phases (AB and Zr{sub 7}Ni{sub 10}) to provide catalytic effects and synergies for improved capacity and high-rate dischargeability (HRD) performance. The main C14 storage phase has smaller lattice constants and cell volumes, and these effects reduce the storage capacity at higher Nd levels. Different hydrogen absorption mechanisms can occur in these multi-component, multi-phase alloys depending on the interfaces of the phases, and they have effects on the alloy properties. Higher Nd-levels improve the HRD performance despite having lower bulk diffusion and surface exchange current. Magnetic susceptibility measurements indicate large percentage of larger metallic nickel clusters are present in the surface oxide of alloys with higher Nd-content, and AC impedance studies show very low charge-transfer resistance with high catalytic capability in the alloys. The −40 °C charge-transfer resistance of 8.9 Ω g in this Nd-series of alloys is the lowest measured out of the studies investigating doped AB{sub 2}-based MH alloys for improved low-temperature characteristics. The improvement in HRD and low-temperature performance appears to be related to the proportion of the highly catalytic NdNi-phase at the surface, which must offset the increased bulk diffusion resistance in the alloy. - Graphical abstract: Schematics of hydrogen flow and corresponding PCT isotherms in funneling mode. - Highlights: • Structural and hydrogen storage properties of Nd-substituted AB{sub 2} metal hydride are reported. • Nd contributes to the lowest

  17. Effects of Nd-addition on the structural, hydrogen storage, and electrochemical properties of C14 metal hydride alloys

    International Nuclear Information System (INIS)

    Nd-addition to the AB2-based alloy Ti12Zr22.8−xV10Cr7.5Mn8.1Co7.0Ni32.2Al0.4Ndx is studied for its effects on the structure, gaseous-phase hydrogen storage, and electrochemical properties. This study follows a series of Cu, Mo, Fe, Y, Si, and La doping studies in similar AB2-based alloys. Limited solubility of Nd in the main Laves phase promotes the formation of secondary phases (AB and Zr7Ni10) to provide catalytic effects and synergies for improved capacity and high-rate dischargeability (HRD) performance. The main C14 storage phase has smaller lattice constants and cell volumes, and these effects reduce the storage capacity at higher Nd levels. Different hydrogen absorption mechanisms can occur in these multi-component, multi-phase alloys depending on the interfaces of the phases, and they have effects on the alloy properties. Higher Nd-levels improve the HRD performance despite having lower bulk diffusion and surface exchange current. Magnetic susceptibility measurements indicate large percentage of larger metallic nickel clusters are present in the surface oxide of alloys with higher Nd-content, and AC impedance studies show very low charge-transfer resistance with high catalytic capability in the alloys. The −40 °C charge-transfer resistance of 8.9 Ω g in this Nd-series of alloys is the lowest measured out of the studies investigating doped AB2-based MH alloys for improved low-temperature characteristics. The improvement in HRD and low-temperature performance appears to be related to the proportion of the highly catalytic NdNi-phase at the surface, which must offset the increased bulk diffusion resistance in the alloy. - Graphical abstract: Schematics of hydrogen flow and corresponding PCT isotherms in funneling mode. - Highlights: • Structural and hydrogen storage properties of Nd-substituted AB2 metal hydride are reported. • Nd contributes to the lowest transfer resistance at −40 °C among other modifiers to AB2 alloy. • AB and Zr7Ni10

  18. Microsynthesis of C-14 labelled environmental chemicals

    International Nuclear Information System (INIS)

    Intention of these studies was to produce C-14 labelled environmental chemicals by means of optimizing the reaction conditions of any individual known synthesis step and to reduce the portion of not usable side-products to a minimum. By means of appropriate working techniques it was possible to largely avoid losses during preparation analysis (extraction, evaporation of diluting solutions, dehydration of reaction products etc.). (orig./HBr)

  19. Measurement of C-14 distribution in forest around nuclear facilities

    International Nuclear Information System (INIS)

    A simple analytical method of C-14 measurement using fast bomb combustion and liquid scintillation counting (LSC) has been developed for measuring C-14 distribution in the terrestrial environment. Specific activities of C-14 in cedar leaves and soils collected from an area around nuclear facilities and control areas were measured using this method. Depth distribution of Cs-137 in soils was also measured at the same sampling sites and compared with the depth distribution of C-14. C-14 specific activity in cedar leaves examined around nuclear facilities exceeded that in the control areas by 8 to 30 mBq (g carbon)-1. The depth distribution of C-14 in forest soil shows that C-14 has peak values in the top 10 cm of the soil profiles ascribed to the highest bomb C-14 level in the 1960's. The data were made available to assess the behavior of fallout C-14 in the surface environment. (author)

  20. Long-term bone retention of C-14 following oral administration of C-14-xylose

    International Nuclear Information System (INIS)

    Oral administration of C-14-labeled xylose followed by measurement of C-14 activity in the breath has become a clinically useful test for diagnosis of small bowel bacterial overgrowth. However, accurate biodistribution and radiation dosimetry information was not available in the literature, so the true radiation exposure of the human subjects was not known. The purpose of this study was to determine the actual biodistribution data for orally administered C-14-xylose. A series of rats were given the material orally and sacrificed at various ages, up to 1 month after dosing. Tissues and fluids were solubilized and counted by liquid scintillation counting. Exhaled C-14-carbon dioxide was measured by trapping the gas in ethanolamine. Approximately two-thirds of the administered dose was absorbed from the GI tract and eventually appeared in the breath and urine. Much of the dose was not found in the major organs within the first day; it was presumed to be in the fatty tissue or muscle, which were not sampled. After most of the C-14 had disappeared from the GI and urinary tract, however, the bone retained a significant amount of radioactivity: approximately 5-6% of the administered dose was found in bone at one week, and remained at one month. These findings suggest that radiation exposure to the skeleton is long-term, much greater in magnitude than previously estimated, and suggests that the value of the test should be reevaluated in the light of the long-term radiation burden to the skeleton, especially in young patients

  1. Assessment of C-14 discharge through liquid waste of NPP

    International Nuclear Information System (INIS)

    Radioactivity and annual discharge rate oc C-14 through the liquid waste of nuclear power plant was investigated using a Carbon sampling kit developed by KEPRI for the analysis of C-14 level of ground water samples near NPP. From the results of periodic samplings and C-14 radioactivity measurements, we realized that the amount of C-14 discharge through the liquid waste is ignorable compared to that through the stack and proportional to H-3 level of liquid waste

  2. Determination of representative nitrogen contents for the activity calculation of core components with respect to the C-14 activity

    Energy Technology Data Exchange (ETDEWEB)

    Kruse, Philipp [GNS Gesellschaft fuer Nuklear-Service mbH, Essen (Germany); Huettner, Frank [Vattenfall Europe Nuclear, Hamburg (Germany); Phlippen, Peter-Wilhelm [WTI GmbH, Juelich (Germany)

    2015-10-15

    For the final repository Konrad during operating and decommissioning phase, ten radionuclides and two radionuclide groups are restricted regarding their maximum storable activity quantities. One of the ten relevant radionuclides is C-14. The determination of the C-14 activities within activation calculations is currently performed with conservative assumptions. With the results of the presented analysis a method for a realistic determination of representative C-14 contents of irradiated steels is available now. The relevant N-14 contents as a source for the C-14 amount are lower than previously estimated.

  3. Laves intermetallics in stainless steel-zirconium alloys

    International Nuclear Information System (INIS)

    Laves intermetallics have a significant effect on properties of metal waste forms being developed at Argonne National Laboratory. These waste forms are stainless steel-zirconium alloys that will contain radioactive metal isotopes isolated from spent nuclear fuel by electrometallurgical treatment. The baseline waste form composition for stainless steel-clad fuels is stainless steel-15 wt.% zirconium (SS-15Zr). This article presents results of neutron diffraction measurements, heat-treatment studies and mechanical testing on SS-15Zr alloys. The Laves intermetallics in these alloys, labeled Zr(Fe,Cr,Ni)2+x, have both C36 and C15 crystal structures. A fraction of these intermetallics transform into (Fe,Cr,Ni)23Zr6 during high-temperature annealing; the authors have proposed a mechanism for this transformation. The SS-15Zr alloys show virtually no elongation in uniaxial tension, but exhibit good strength and ductility in compression tests. This article also presents neutron diffraction and microstructural data for a stainless steel-42 wt.% zirconium (SS-42Zr) alloy

  4. Review of C-14 inventory for the SFR facility

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Graham; Merino, Joan; Kerrigan, Emma

    2002-08-01

    The Swedish Radiation Protection Authority (SSI) is currently reviewing SKB's continuing assessment for disposal of radioactive waste to the SFR facility at Forsmark. Among the wastes disposed are reactor operating wastes. Among the relevant radionuclides is C-14, which is relatively difficult to measure and to control because of its mobility. This report documents a review of the C-14 inventory material submitted by SKB for the SFR-facility, to determine its validity and comment on the appropriate assumptions for C-14 content of wastes due to be disposed of to the SFR. The review is based on information provided by SSI as well as other relevant international experience. Conclusions are drawn upon: the chemical form of the C-14 in the waste from BWRs and PWRs; the production rate of C-14 in BWRs and PWRs and quantification of the source term in the IEX waste; the distribution of the C-14 in the IEX waste from BWR between the resins used for treatment of the primary cooling water and the resins used for treatment of the condensate water; quantification of the uncertainties. A suggestion is made that the C-14 inventory could be better developed based upon a mass balance assessment of all the C-14 produced in reactors, and its ultimate fate in effluent and solid wastes, taking account of the reactor specific operational factors identified in the review as relevant to C-14 inventory assessment.

  5. Review of C-14 inventory for the SFR facility

    International Nuclear Information System (INIS)

    The Swedish Radiation Protection Authority (SSI) is currently reviewing SKB's continuing assessment for disposal of radioactive waste to the SFR facility at Forsmark. Among the wastes disposed are reactor operating wastes. Among the relevant radionuclides is C-14, which is relatively difficult to measure and to control because of its mobility. This report documents a review of the C-14 inventory material submitted by SKB for the SFR-facility, to determine its validity and comment on the appropriate assumptions for C-14 content of wastes due to be disposed of to the SFR. The review is based on information provided by SSI as well as other relevant international experience. Conclusions are drawn upon: the chemical form of the C-14 in the waste from BWRs and PWRs; the production rate of C-14 in BWRs and PWRs and quantification of the source term in the IEX waste; the distribution of the C-14 in the IEX waste from BWR between the resins used for treatment of the primary cooling water and the resins used for treatment of the condensate water; quantification of the uncertainties. A suggestion is made that the C-14 inventory could be better developed based upon a mass balance assessment of all the C-14 produced in reactors, and its ultimate fate in effluent and solid wastes, taking account of the reactor specific operational factors identified in the review as relevant to C-14 inventory assessment

  6. Microstructure and mechanical properties of laser melting deposited Ti2Ni3Si/NiTi Laves alloys

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Two Ti2Ni3Si/NiTi Laves phase alloys with chemical compositions of Ni-39Ti-11 Si and Ni-42Ti-8Si (%, mole fraction, the same below), respectively, were fabricated by the laser melting deposition manufacturing process, aiming at studying the effect of Ti,Si contents on microstructure and mechanical properties of the alloys. The Ni-39Ti-llSi alloy consisting of Ti2Ni3Si primary dendrites and Ti2Ni3Si/NiTi eutectic matrix is a conventional hypereutectic Laves phase alloy while the Ni-42Ti-8Si alloy being made up of NiTi primary dendrites uniformly distributed in Ti2Ni3Si/NiTi eutectic is a new hypoeutectic alloy. Mechanical properties of the alloys were investigated by nano-indentation test. The results show that the decrease of Si and the increase of Ti contents change the microstructures of the alloys from hypereutectic to hypoeutectic, which influences the mechanical properties of the alloys remarkably. Corrosion behaviors of the alloys were also evaluated by potentiodynamic anodic polarization curves.

  7. Capture reactions on C-14 in nonstandard big bang nucleosynthesis

    Science.gov (United States)

    Wiescher, Michael; Gorres, Joachim; Thielemann, Friedrich-Karl

    1990-01-01

    Nonstandard big bang nucleosynthesis leads to the production of C-14. The further reaction path depends on the depletion of C-14 by either photon, alpha, or neutron capture reactions. The nucleus C-14 is of particular importance in these scenarios because it forms a bottleneck for the production of heavier nuclei A greater than 14. The reaction rates of all three capture reactions at big bang conditions are discussed, and it is shown that the resulting reaction path, leading to the production of heavier elements, is dominated by the (p, gamma) and (n, gamma) rates, contrary to earlier suggestions.

  8. Quantum Phase Transitions and Multicriticality in Ta(Fe1-xVx)2

    Science.gov (United States)

    Brando, Manuel; Kerkau, Alexander; Todorova, Adriana; Yamada, Yoshihiro; Khuntia, Panchanan; Förster, Tobias; Burkhard, Ulrich; Baenitz, Michael; Kreiner, Guido

    2016-08-01

    We present a comprehensive study of synthesis, structure analysis, transport and thermodynamic properties of the C14 Laves phase Ta(Fe1-xVx)2. Our measurements confirm the appearance of spin-density wave (SDW) order within a dome-like region of the x-T phase diagram with vanadium content 0.02 AFM) ones. This results in an exchange-enhanced susceptibility and in the suppression of the SDW transition temperature for x AFM energy scales have similar strength and the system remains paramagnetic down to 2 K with an extremely large Stoner enhancement factor of about 400. Here, spin fluctuations dominate the temperature dependence of the resistivity ρ ∝ T3/2 and of the specific heat C/T ∝ -log(T) which deviate from their conventional Fermi liquid forms, inferring the presence of a quantum critical point of dual nature.

  9. Biokinetics and dosimetry of radioactively labelled organic C-14 compounds

    International Nuclear Information System (INIS)

    The report starts with summarising research work and the resulting scientific information in connection with the dosimetry of C-14 labelled organic compounds. Biokinetic models are developed for compounds such as benzene, phenol, aniline, nitrobenzene, and a selection of pharmaceuticals, in order to show the radioactivity distribution after administration of the C-14 labelled substances. Based on the those models, dose coefficients and excretion rates are derived. The following synoptic view of the available data library leads on to a discussion of various aspects, as eg. the question of whether and how monitoring for detection of incorporation of C-14 administered with labelled organic compounds is possible. None of the questions and aspects arising in connection with this subject can be adequately dealt with in the present document, but concepts and methods are presented which permit an interpretation of radioactivity excretion data measured after incorporation of C-14 labelled organic substances. (orig./CB)

  10. Root-Uptake of C-14 Acetic Acid by Various Plants and C-14 Dynamics Surrounding the Experimental Tessera

    International Nuclear Information System (INIS)

    Carbon-14 (C-14, t1/2 = 5.73x103 yrs) from radioactive waste is one of the most important radioactive nuclides for environmental assessment in the context of geological disposal, and understanding the transfer of radioactive elements to plants is essential for public health safety. In order to obtain fundamental knowledge, culture experiments using marigold (Tagetes patula L.), tall fescue (Festuca arundinacea S.), paddy rice (Oryza sativa L.), radish (Raphanus sativus L.), and carrot (Daucus carota L.) plants were conducted to examine root-uptake and dynamics of C-14 in the laboratory. The C-14 radioactivity in each plant part (e.g. shoot, root, edible part, etc.), medium (e.g. culture solution, sand, etc.), and air was determined. The distribution of C-14 in the plants was visualized using autoradiography. For a comparison, autoradiography was also done using Na-22. Results of the present study indicated that C-14 labeled CO2 gas was released from the culture solution to the atmosphere. Clear autoradiography images were observed in plants for the shoots and lower roots which were soaked in the culture solution. The upper roots which were not soaked in the culture solution were not clearly imaged. In the radiotracer experiment using Na-22, a clear image was observed for the whole carrot seedling, even including the upper root, on the autoradiography. However, the amounts of C-14 acetic acid absorbed by all the plants through their roots were considered to be very small. Inorganic carbon transformed from C-14 acetic acid would be taken up by plants through the roots, and some fraction of C-14 would be assimilated into the shoots by photosynthesis. (authors)

  11. Metabolism and translocation of C14-trazine in growing corn

    International Nuclear Information System (INIS)

    Movement, translocation and metabolism of C14-atrazine in corn grown under conventional and no-till management was studied in the agro-ecosystem chamber (150x50x100 cm). C14-atrazine, and commercial atrazine which is aatrex-nie-0 were applied at 14 uCi and 128 mg (a.i) per chamber. After growing, the determination of volatilization, degradation in soil, and translocation into other parts of corn plant have been investigated after application in the certain period of time on 0, 1, 3, 5, 7, 15, 30, 45, 65 and 85 days, respectively. The volatilization was highest just after treatment and then became lower as time increased and as well as residues discovered in the soil. Its metabolites were discovered in both soil and air but C14-conjugated atrazine was found in root, stem, and corn leaves

  12. Influence of air temperature and humidity on simultaneous collection of H-3 and C-14 by mono-ethanolamine solution

    International Nuclear Information System (INIS)

    Lumagel Plus scintillator was selected as the most suitable scintillator for simultaneous collection of H-3 and C-14 by using mono-ethanolamin (MEA) solution. The influence of air temperature and humidity on the collection efficiency of H-3 and C-14 was examined. As the result, when the weight of water in MEA was less than 1000 mg, the samples became colorless without separation into two phases, and the collection efficiency of 99% and more was obtained for C-14 within the collection time of 3.7 hours. On the other hand, the collection efficiency for H-3 decreased with increase of the weight of water in the collected air, but it was more than 90% even at high temperature of 30°C and high relative humidity of 90%. It was found that this method is practically useful for simultaneous determination of H-3 and C-14 concentration in air. (author)

  13. Hyperfine field and induced moment of {sup 181}Ta in the rare earth-iron laves compounds

    Energy Technology Data Exchange (ETDEWEB)

    Komissarova, B.A.; Ryasny, G.K.; Shpinkova, L.G.; Sorokin, A. A. [Institute of Nuclear Physics, Moscow State University, Moscow (Russian Federation); Tsvyashchenko, A.V.; Fomicheva, L.N. [Institute of High Pressure Physics, Russian Academy of Sciences, Moscow (Russian Federation); Denisova, A.S. [Institute of Crystallography, Russian Academy of Sciences, Moscow (Russian Federation)

    1998-12-01

    The hyperfine magnetic fields and their temperature dependence for {sup 181}Ta in ErFe{sub 2} and TmFe{sub 2} have been measured by the TDPAC method. Respectively, the following values were obtained at T approx 80 K: 16 . 3(2) T and 17. 6(2) T. These data complete those for other RFe2 Laves phases (except CeFe{sub 2}) obtained earlier and are discussed in common in the framework of the model predicting the induction of the localised 5d moment at Ta ions due to 5d-3d band hybridisation enhanced by the 4f-5d interaction. Copyright (1998) Australian Journal of Physics 28 refs., 1 tab., 4 figs.

  14. Preparation of toluenes specifically labelled with C-14

    International Nuclear Information System (INIS)

    The attempt to prepare toluene-2 C-14 starting from ethyl acetoacetate failed because the reaction of sodium ethyl acetoacetate with dibromopropane could not be performed. This labelling was also attempted starting from methyl tetrahydropyran. This synthesis was not successful because the preparationof 2-methyl pimelic acid was impossible. Labellimg of carbon-3 of toluene starting from succinic acid could not be carried out because the Grignard reaction of a-ketoglutaric acid as unsuccessful. The radioactive syntheses started from propanediol resp. from c-butyrolactone. (The labelling of carbon-3 of toluene was not possible in this case because the reduction of malonic acid to propanediol could not be carried out). The synthesis course was identical for all labellings. The synthesis differed only in the introduction of the activiy from potassium cyanide C-14. The starting compounds were reacted to propanedinitril, which was saponified to glutaric acid. The acid was reduced to pentanediol. From the diol, dibromopentane was produced. Reaction with potassium cyanide yielded, after saponification, pimelic acid. The acid was cyclizated to cyclohexanone, which was reduced to cyclohexanol. The OH group was replaced by bromine and subsequently by a methyl group. Dehydration yielded toluene. The following labellings were carried out: Toluene-2, -2.6, -1.2.6, -1.2 C-14. (G.G.)

  15. Last fra kornede materialer på begrænsningsvægge i lave lagerbygninger

    DEFF Research Database (Denmark)

    Møller, S.

    Rapporten indeholder forudsætninger og retningslinier for den statiske beregning af lave lagerbygninger, fx. plansiloer i landbruget. I to hovedkapitler gives data og formler til lastbestemmelse som grundlag for brudundersøgelse og deformationsundersøgelse, samt et eksempel på lastberegning....

  16. MICADAS C-14 AMS applications in environmental research in Hungary

    International Nuclear Information System (INIS)

    Radiocarbon (C-14) analyses are applied in environmental protection, archaeology, geology, hydrology, climatology and other scientific branches in Hungary since the 1980’s. In 2011 a more modern AMS technology took over our old C-14 radiometric (GPC) method, which is based on isotope separation by accelerator mass spectrometry. AMS method requires much less sample quantity (0.1-100 mg) than the older GPS technique and gives ten times higher throughput. For our laboratory a MICADAS type AMS system was developed by ETHZ (Zürich, Switzerland) in connection with environmental research, equipped with a gas inlet system to transfer CO2 gas sample into the AMS ion source. Final acceptance of the EnvironMICADAS was completed at Debrecen, Hungary the autumn of 2011. In the first three year of operation more than 8000 targets were analyzed in the new AMS lab of Hungary. Analytical performance, novel technical developments, interesting samples and results will be presented in this talk. (author)

  17. Crystal-Structure Analysis with Moments of the Density-of-States: Application to Intermetallic Topologically Close-Packed Phases

    Directory of Open Access Journals (Sweden)

    Thomas Hammerschmidt

    2016-02-01

    Full Text Available The moments of the electronic density-of-states provide a robust and transparent means for the characterization of crystal structures. Using d-valent canonical tight-binding, we compute the moments of the crystal structures of topologically close-packed (TCP phases as obtained from density-functional theory (DFT calculations. We apply the moments to establish a measure for the difference between two crystal structures and to characterize volume changes and internal relaxations. The second moment provides access to volume variations of the unit cell and of the atomic coordination polyhedra. Higher moments reveal changes in the longer-ranged coordination shells due to internal relaxations. Normalization of the higher moments leads to constant (A15,C15 or very similar (χ, C14, C36, μ, and σ higher moments of the DFT-relaxed TCP phases across the 4d and 5d transition-metal series. The identification and analysis of internal relaxations is demonstrated for atomic-size differences in the V-Ta system and for different magnetic orderings in the C14-Fe 2 Nb Laves phase.

  18. C-14/I-29 Preservation and Hold Time Survey

    Energy Technology Data Exchange (ETDEWEB)

    Kitchen, S. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-04-08

    Preservation and hold time of radionuclides must account for both nuclear half-lives and nonnuclear loss mechanisms, but variations in the latter are often neglected. Metals-based defaults are inappropriate for long-lived non-metals C-14 and I-129, which are vulnerable to chemical and biological volatilization. Non-acidification is already widely practiced for them. Recommended addition measures from radiological and chemical literature include glass containers where possible, water filtration where possible, headspace minimization, light shielding, cold (4°C) storage and unfiltered water hold time of 28 days. Soil hold time may need to be shortened when water-logged, excessively sandy, or still adjusting to significant new contamination.

  19. Bond Rupture following C14 and T3 Beta Decay

    International Nuclear Information System (INIS)

    As a result of nuclear transformations an atom acquires a recoil energy, and a portion of this energy becomes associated with the chemical bond or bonds joining the activated atom to the molecule. Usually sufficient energy is deposited in these bonds to permit the activated atom to dissociate from the remainder of the molecule. Bond-rupture, however, usually does not occur with 100% efficiency. Momentum transfer to an atom in a molecule (internal excitation and bond-rupture) have been discussed recently with reference to activation of atoms joined to a molecule by only one bond. Additional molecules are considered in the present paper, and data presented on the net recoil energy required for bond- rupture, the rotational and vibrational excitation energies received by the rupturing bond, the internal energy of the radical originally bonded to the activated atom, and the kinetic energy of the radicals. It is shown that, on the average, the recoil energy that must be acquired by the activated atom in order to rupture from the molecule is about 25% greater than that calculated assuming a pseudo-diatomic molecule. Data are also presented for certain C14 and T3 beta-decay recoil processes. For C14O2 it is calculated that a net N14 recoil energy s 1.92 times the ON-O+ bond dissociation energy is required for bond-rupture. Since the NO+2 product may possess about 0.6 to 1.0 eV of electronic excitation energy, the ON-O+ bond dissociation energy is not uniquely defined. The calculated value of non-bond-rupture is 73 - 87% in good agreement with the reported experimental value of 81%. Similar data are also presented for such molecules as CH3T, C2H5T, C3H7T, and C142H6. (author)

  20. (CH4)-C-14 Measurements in Greenland Ice: Investigating Last Glacial Termination CH4 Sources

    DEFF Research Database (Denmark)

    Petrenko, V. V.; Smith, A. M.; Brook, E. J.;

    2009-01-01

    contributions to this increase. We present measurements of (CH4)-C-14 in glacial ice, targeting this transition, performed by using ice samples obtained from an ablation site in west Greenland. Measured (CH4)-C-14 values were higher than predicted under any scenario. Sample (CH4)-C-14 appears to be elevated by...

  1. Enhanced magnetoelastic effect in Laves (Tb,Dy)Fe2 alloys with the joint introduction of Pr and Nd

    Science.gov (United States)

    Song, X. H.; Liu, J. J.; Wei, S. H.; Zhu, X. Y.; Li, F.; Zhang, Z. R.; Si, P. Z.; Ren, W. J.

    2016-06-01

    The structural and magnetoelastic properties of (Tb0.3Dy0.7)1-x(Pr0.5Nd0.5)xFe1.93 (0 ≤ x ≤ 0.20) polycrystalline alloys have been investigated by means of X-ray diffraction (XRD), a vibrating sample magnetometer and a standard strain gauge technique. A single (Tb,Dy,Pr,Nd)Fe2 Laves phase with a cubic MgCu2-type structure is formed when x ≤ 0.12, while a small amount of impurities appear when x ≥ 0.15. The easy magnetization direction at room temperature is detected toward axis. The analysis of XRD, magnetization and magnetostriction shows that the Pr and Nd elements joint introduction into (Tb,Dy)Fe2 system can reduce the magnetocrystalline anisotropy and improve the magnetoelastic properties. The (Tb0.3Dy0.7)0.88(Pr0.5Nd0.5)0.12Fe1.93 alloy exhibits a high low-field magnetostriction λ a (~314 ppm/1 kOe), a large spontaneous magnetostriction coefficient λ 111 (~1710 ppm), a giant saturation magnetostriction λ S (~1060 ppm) and the low magnetocrystalline anisotropy at room temperature, and may make it a promising candidate for magnetostriction applications.

  2. Electro-removal of H-3 and C-14 contained in scintillation liquid absorbed in soils type Phaeozem; Electrorremocion de H-3 y C-14 contenidos en liquido de centelleo absorbidos en suelos tipo Phaeozem

    Energy Technology Data Exchange (ETDEWEB)

    Valdovinos, V.; Bustos, E. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Parque Tecnologico Queretaro s/n, San Fandila, 76703 Pedro Escobedo, Queretaro (Mexico); Monroy G, F., E-mail: vvaldovinos@cideteq.mx [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2014-10-15

    This paper presents the results of electro-removal, an electrochemical treatment in soils contaminated with H-3 and C-14 contained in scintillation liquids absorbed in soils. For this purpose the best electrochemical conditions were used, which are: scintillation liquid Ultima Gold Xr, water (1:1) and 1 m A in the passage of current. The media were characterized before and after of applying the different potentials by various analytical techniques, such as: liquids by gas chromatography with a flame ionization detector, solids and liquids by Fourier transform infrared spectroscopy (Ftir) and electrodes by scanning electron microscopy with elemental analysis by energy-dispersive X-ray spectroscopy. Later standard samples with H-3 and C-14 were prepared and the electrochemical treatment was applied to previously established conditions. After electrochemical treatment the scintillation liquid characterization was performed by gas chromatography and a scintillation counter to see the disintegrations per minute. According to results of Ftir, soils show no deterioration and in the liquid phase the amount of water increases as the applied potential, due to oxidation-reduction reactions where happen modification or mineralization of organic molecules (H{sub 2}O and CO{sub 2} formation). In 4 h of treatment, removal percentages in the liquid phase, were: 53.6% of H-3 and 11.6% of C-14. (Author)

  3. Preparation of C14-labelled tetrazolium salts and tracer study of the tetrazene-formazan rearrangement

    International Nuclear Information System (INIS)

    The preparation of [5-C14]-TTC, [5, 5'-di-C14]NT (neotetrazolium) and [5, 5'-di-C14]-BT (tetrazolium blue) starting from benzaldehyde- [1-C14] has been accomplished. The yields for both mono- and ditetrazolium salts are high, and the products can be obtained with high sp. activity. The purity of the samples was investigated by paper chromatography. In the case of ditetrazolium salts some impurities could be detected and conclusions drawn as to their structure and quantity. A method has been developed to prepare C14- labelled ditetrazolium salts of high purity. The formation of the formazan, the precursor of the tetrazolium salt, goes through an unstable intermediate of tetrazene-type structure which rearranges rapidly in basic medium, to yield the formazan. The tetrazene intermediate can be isolated under suitable conditions. By using C14-labelled benzaldehyde phenylhydrazone this rearrangement was investigated and a verification of its intramolecular character given. (author)

  4. Electro-removal of H-3 and C-14 contained in scintillation liquid absorbed in soils type Phaeozem

    International Nuclear Information System (INIS)

    This paper presents the results of electro-removal, an electrochemical treatment in soils contaminated with H-3 and C-14 contained in scintillation liquids absorbed in soils. For this purpose the best electrochemical conditions were used, which are: scintillation liquid Ultima Gold Xr, water (1:1) and 1 m A in the passage of current. The media were characterized before and after of applying the different potentials by various analytical techniques, such as: liquids by gas chromatography with a flame ionization detector, solids and liquids by Fourier transform infrared spectroscopy (Ftir) and electrodes by scanning electron microscopy with elemental analysis by energy-dispersive X-ray spectroscopy. Later standard samples with H-3 and C-14 were prepared and the electrochemical treatment was applied to previously established conditions. After electrochemical treatment the scintillation liquid characterization was performed by gas chromatography and a scintillation counter to see the disintegrations per minute. According to results of Ftir, soils show no deterioration and in the liquid phase the amount of water increases as the applied potential, due to oxidation-reduction reactions where happen modification or mineralization of organic molecules (H2O and CO2 formation). In 4 h of treatment, removal percentages in the liquid phase, were: 53.6% of H-3 and 11.6% of C-14. (Author)

  5. C-14 Measurements of Ice Samples from the Juvfonne Ice Tunnel, Jotunheimen, Southern Norway-Validation of a C-14 Dating Technique for Glacier Ice

    OpenAIRE

    Zapf, Alexander; A. Nesje; Szidat, Sönke; L. Wacker; Schwikowski, Margit

    2013-01-01

    Establishing precise age-depth relationships of high-alpine ice cores is essential in order to deduce conclusive paleoclimatic information from these archives. Radiocarbon dating of carbonaceous aerosol particles incorporated in such glaciers is a promising tool to gain absolute ages, especially from the deepest parts where conventional methods are commonly inapplicable. In this study, we present a new validation for a published C-14 dating method for ice cores. Previously C-14-dated horizons...

  6. Phase Composition of a CrMo0.5NbTa0.5TiZr High Entropy Alloy: Comparison of Experimental and Simulated Data

    Directory of Open Access Journals (Sweden)

    Fan Zhang

    2013-09-01

    Full Text Available Microstructure and phase composition of a CrMo0.5NbTa0.5TiZr high entropy alloy were studied in the as-solidified and heat treated conditions. In the as-solidified condition, the alloy consisted of two disordered BCC phases and an ordered cubic Laves phase. The BCC1 phase solidified in the form of dendrites enriched with Mo, Ta and Nb, and its volume fraction was 42%. The BCC2 and Laves phases solidified by the eutectic-type reaction, and their volume fractions were 27% and 31%, respectively. The BCC2 phase was enriched with Ti and Zr and the Laves phase was heavily enriched with Cr. After hot isostatic pressing at 1450 °C for 3 h, the BCC1 dendrites coagulated into round-shaped particles and their volume fraction increased to 67%. The volume fractions of the BCC2 and Laves phases decreased to 16% and 17%, respectively. After subsequent annealing at 1000 °C for 100 h, submicron-sized Laves particles precipitated inside the BCC1 phase, and the alloy consisted of 52% BCC1, 16% BCC2 and 32% Laves phases. Solidification and phase equilibrium simulations were conducted for the CrMo0.5NbTa0.5TiZr alloy using a thermodynamic database developed by CompuTherm LLC. Some discrepancies were found between the calculated and experimental results and the reasons for these discrepancies were discussed.

  7. Linear C32H66 hydrocarbon in the mixed state with C10H22, C12H26, C14H30, C16H34 and C18H38: Comparison of strength of phases and role of tunnel-like defects

    Indian Academy of Sciences (India)

    P B Shashikanth; P B V Prasad

    2003-02-01

    Strengths of m, o and phases of linear dotriacontane hydrocarbon in mixed state with certain shorter chain length homologues (SMOLLENCs), estimated from powder XRD analysis, are compared. The results suggest strong evidence in favour of tunnel-like defects (TLIDs).

  8. Future needs and requirements for AMS C-14 standards and reference materials

    NARCIS (Netherlands)

    Scott, EM; Boaretto, E; Bryant, C; Cook, GT; Gulliksen, S; Harkness, DD; Heinemeier, J; McGee, E; Naysmith, P; Possnert, G; van der Plicht, H; van Strydonck, M; Cook, Gordon T.

    2004-01-01

    C-14 measurement uses a number of standards and reference materials with different properties. Historically the absolute calibration of C-14 measurement was tied to 1890 wood, through the 'primary' standard of NBS-OxI (produced by the National Bureau of Standards, now NIST - National Institute of St

  9. Accelerator mass spectrometry measurements of the C-13(n,gamma)C-14 and N-14(n,p)C-14 cross sections

    OpenAIRE

    Wallner, A.; Bichler, M.; Buczak, K.; Dillmann, I.; Kaeppeler, F.; A. Karakas; Lederer, C.; Lugaro, M.; Mair, K.; A.Mengoni; Schaetzel, G.; P. Steier; Trautvetter, H. P.

    2016-01-01

    The technique of accelerator mass spectrometry (AMS), offering a complementary tool for sensitive studies of key reactions in nuclear astrophysics, was applied for measurements of the C-13(n,gamma)C-14 and the N-14(n,p)C-14 cross sections, which act as a neutron poison in s-process nucleosynthesis. Solid samples were irradiated at Karlsruhe Institute of Technology with neutrons closely resembling a Maxwell-Boltzmann distribution for kT = 25 keV, and also at higher energies between En = 123 an...

  10. Elastic constants of a Laves phase compound: C15 NbCr2

    International Nuclear Information System (INIS)

    The single-crystal elastic constants of C15 NbCr2 have been computed by using a first-principles, self-consistent, full-potential total energy method. From these single-crystal elastic constants the isotropic elastic moduli are calculated using the Voigt and Reuss averages. The calculated values are in fair agreement with the experimental values. The implications of the results are discussed with regards to Poisson's ratio and the direction dependence of Young's modulus

  11. Electronic structure, cohesive, and magnetic properties of the actinide-iridium Laves phases

    International Nuclear Information System (INIS)

    The electronic structure of the isostructural AIr2 systems (A = Th, Pa, U, Np, Pu, and Am) has been obtained by means of the scalar relativistic and fully relativistic linear muffin-tin orbital techniques. Ground-state properties such as lattice constants and onset of magnetic order have been calculated and compared with measured data. The hybridization between the actinide 5f and the ligand 5d states and the direct 5f wave-function overlap are found to be of comparable importance for the bandwidth of the itinerant 5f states. The anomalous paramagnetism of PuIr2 can be explained only by a fully relativistic treatment

  12. Electronic structure, cohesive, and magnetic properties of the actinide-iridium Laves phases

    DEFF Research Database (Denmark)

    Eriksson, O.; Johansson, B.; Brooks, M. S. S.; Skriver, Hans Lomholt

    1989-01-01

    The electronic structure of the isostructural AIr2 systems (A=Th, Pa, U, Np, Pu, and Am) has been obtained by means of the scalar relativistic and fully relativistic linear muffin-tin orbital techniques. Ground-state properties such as lattice constants and onset of magnetic order have been...

  13. X-ray magnetic circular dichroism experiments and theory of transuranium Laves phase compounds

    Czech Academy of Sciences Publication Activity Database

    Wilhelm, F.; Eloirdi, R.; Rusz, Ján; Springell, R.; Colineau, E.; Griveau, J.C.; Oppeneer, P. M.; Caciuffo, R.; Rogalev, A.; Lander, G.H.

    2013-01-01

    Roč. 88, č. 2 (2013), "024424-1"-"024424-14". ISSN 1098-0121 Institutional support: RVO:68378271 Keywords : electronic -structure * uranium-compounds * self-absorption * moments Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.664, year: 2013

  14. Algal C-14 and total carbon metabolisms 2. Experimental observations with the diatom Skeletonema costatum

    DEFF Research Database (Denmark)

    Williams, P.J.L.; Robinson, C.; Søndergaard, M.; Jespersen, A.M.; Bentley, T.L.; Lefevre, D.; Richardson, Katherine; Riemann, B.

    1996-01-01

    Three sets of comparisons of net and gross inorganic carbon assimilation and C-14 uptake were made with an axenic culture of Skeletonema costatum. The comparisons showed that in the physiological window studied (10-20% of the intrinsic generation time and gross photosynthesis/respiration ratios of......2. The conclusion drawn was that over the time scale studied, the C-14 technique was measuring net photosynthesis, consistent with essentially 100% recycling of respiratory CO2. The study has shown that we now possess the basis to make a rigorous analysis of net, gross CO2 fixation and net C-14...

  15. Synthesis and structural characterization of (C14H16N2)3 (C14H17N2)2 [-Mo8 O26

    Indian Academy of Sciences (India)

    Ikram Zebiri; Sihem Boufas; Salima Mosbah; Leïla Bencharif; Mustapha Bencharif

    2015-10-01

    A novel polyoxomolybdate (C14H16N2)3 (C14H17N2)2 [-Mo8 O26] (1) has been synthesized from hydrothermal reaction of tolidine and molybdenum trioxide in water and characterized by its IR and UV spectra, 1H NMR, cyclic voltammetry and single crystal X-ray diffraction. Compound 1 crystallizes in the triclinic crystal system, space group P$\\bar{ı}$, with the crystal cell parameters of =11.5360 Å, =11.6080 Å, =15.2520 Å, =72.50° , =79.46° , =86.91° , =1915.00 Å3 and =1. The asymmetric unit of the crystal structure of (C14H16N2)3 (C14H17N2)2 [-Mo8 O26] contains -octamolybdate [-Mo8 O26]4− anions, two tolidine molecules and shows the presence of monoprotonated tolidine cations. One tolidine molecule and a -Mo8 O26 polyanions species lie across crystallographic inversion centres while the two tolidine molecules occupy general sites.

  16. Spectral analysis of colour-quenched and chemically quenched C-14 samples; Estudio espectral de muestras de C-14 con extincion quimica y por color en centelleo liquido

    Energy Technology Data Exchange (ETDEWEB)

    Scott, P. E.; Grau, A.

    1987-07-01

    In this paper pairs of pulse height distribution curves, of C-14 samples, colour-quenched and chemically quenched was obtained. The possibility to choose a counting window in order to obtain the counting efficiency curves, for both type of quenching was studied. (Author) 7 refs.

  17. Algal C-14 and total carbon metabolisms 2. Experimental observations with the diatom Skeletonema costatum

    DEFF Research Database (Denmark)

    Williams, P.J.L.; Robinson, C.; Søndergaard, M.;

    1996-01-01

    of 2-3), C-14 uptake into the particulate plus the dissolved fractions approximated to net photosynthesis. Rate constants derived from the chemically determined changes were used to parameterize models that accounted for the respiration of photosynthetic products and for the recycling of respiratory CO......2. The conclusion drawn was that over the time scale studied, the C-14 technique was measuring net photosynthesis, consistent with essentially 100% recycling of respiratory CO2. The study has shown that we now possess the basis to make a rigorous analysis of net, gross CO2 fixation and net C-14......Three sets of comparisons of net and gross inorganic carbon assimilation and C-14 uptake were made with an axenic culture of Skeletonema costatum. The comparisons showed that in the physiological window studied (10-20% of the intrinsic generation time and gross photosynthesis/respiration ratios...

  18. The metabolism of C14-labeled phenylalanine and tyrosine in malaria-infected Culex-females

    International Nuclear Information System (INIS)

    Culex females are fed on C14-phenylalanine or C14-tyrosine in sugar solution. Autoradiographic studies on homogenated females 1 or 4 days after feeding, show that the labeled amino acids are metabolized on the first day and are not detectable on the fourth day. After increase of the amino acid concentration by saturation of the sugar solution with the unlabeled amino acid, the labeled acid and its metabolites are visible over a longer period of time. Phenylalanine is metabolized to tyrosine and at least four other substances. Radioactivity on the starting point of the chromatogram can be interpreted as incorporation of tyrosine into proteins. After infection with Plasmodium cathemerium, and feeding of C14-phenylalanine C14-tyrosine is demonstrable over a longer period. (orig.)

  19. Chemical Characterization and Removal of C-14 from Irradiated Graphite-12010

    International Nuclear Information System (INIS)

    Quantities of irradiated graphite waste are expected to drastically increase, which indicates the need for a graphite waste management strategy. Of greatest concern for long-term disposal of irradiated graphite is carbon-14 (C-14), with a half-life of 5730 years. Study of irradiated graphite from nuclear reactors indicates C-14 is concentrated on the outer 5 mm of the graphite structure. The aim of the research described here is to identify the chemical form of C-14 in irradiated graphite and develop a practical method by which C-14 can be removed. Characterization of pre- and post-irradiation graphite was conducted to determine bond type, functional groups, location and concentration of C-14 and its precursors via the use of surface sensitive characterization techniques. Because most surface C-14 originates from neutron activation of nitrogen, an understanding of nitrogen bonding to graphite may lead to a greater understanding of the formation pathway of C-14. However, no single technique provides a complete picture. Therefore, a portfolio of techniques has been developed, with each technique providing another piece to the puzzle that is the chemical nature of the C-14. Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and Raman Spectroscopy were used to evaluate the morphological features of graphite samples. The concentration, chemical composition, and bonding characteristics of C-14 and its precursors were determined through X-ray Photoelectron Spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectrometry (SIMS), and Auger and Energy Dispersive X-ray Analysis Spectroscopy (EDX). High-surface-area graphite foam, POCOFoamR, was exposed to liquid nitrogen and irradiated. Characterization of this material has shown C-14 to C-12 ratios of 0.035. This information was used to optimize the thermal treatment of graphite. Thermal treatment of irradiated graphite as reported by Fachinger et al. (2007) uses naturally adsorbed oxygen complexes to gasify

  20. Evaluation of surface dose rate on C-14 scrubber and gas bag

    International Nuclear Information System (INIS)

    In CANDU(Canadian Deuterium Uranium) reactors, purge and discharge of moderator cover gas has been performed via vapor recovery system. The methods employed in C-14 removal are mainly based on reactions of CO2 with absorber of adsorbent. In order to choose an optimum process, we should consider the characteristics of the process, such as, temperature, pressure, humidity etc. and surface dose rate on C-14 scrubber and gas bag to estimate job-related personnel doses. Assuming that the whole C-14 scrubber was completely replaced after one-cycle operation, and that its C-14 activity for one-cycle operation was 40 mCi, we calculated the surface dose rate at the six points of the C-14 scrubber. This calculation showed that the dose rate on the surface of cartridge was only 1.25μSυ/hγ because of low energy of β ray. It is concluded, therefore, that the cartridge change-out is safe because the operation of C-14 removal system causes only a small increase in dose rate

  1. Development of adsorbent for C-14 Gas trapping and characteristics evaluation

    International Nuclear Information System (INIS)

    Desorption characteristics of C-14 adsorbed on spent resin as H14CO3 ion type by applying various stripping solutions were analyzed, and some experiments for gasification of C-14 to CO2 gas with were also performed. Based on these results, the process concept for spent resin treatment was suggested. Real spent resin was prepared from sampling in storage tank in site 1 of Wolseung Nuclear Power Plant. Desorption characteristics of C-14 and cations of Cs, Co from spent IRN-150 resin was evaluated. Desorption efficiency of C-14 from spent resin by using H3PO4 desorption solution was over 96% regardless of C-14 amount on initial spent resin when comparing a activity of C-14 on initial spent resin. Also, desorption percent of cation of Cs, Co from anion ion-exchange resin (IRN-77) showed that Co-60 was below 1%, Cs-134, 137 was in a range of 2 ∼ 5%. Fundamental studies include an development of adsorbent manufacturing technology and its performance evaluation for C-14 gas trapping, the adsorption process by adopting gas circulation method was suggested for the design of 14CO2 gas treatment system generated from spent resin treatment process. In order to predict adsorbent performance of CO2 trapping, modelling was carried out to verify the breakthrough curves of CO2 trapping by using soda lime adsorbent. The effect of humidity on CO2 trapping by using soda lime adsorbent was modelled via chemical reaction in porous media. Assessment of the state-of-the-arts on the solidification of the used adsorbent showed that the cement matrix would be the best-available binder from the view points of the matrix compatibility, properties of the final waste form, simplicity of the process and relatively low cost

  2. République de Djibouti : coulée de lave de l'Ardoukôba

    OpenAIRE

    Pouyllau, Stéphane

    2009-01-01

    Coulée de lave de l'Ardoukôba, datant de l'éruption de 1978. Hauteur 6 à 8 m dans le champ de la photographie. Le volcan Ardoukôba est un volcan rouge actif de la région de Tadjourah. Il est né en 1978 et n'a connu qu'une éruption (du 7 au 14 nov. 1978).

  3. The C-14(alpha, gamma)O-18 reaction at astrophysical energies

    International Nuclear Information System (INIS)

    The C-14(alpha, gamma)O-18 reaction rate is estimated for temperatures important for He flashes in white dwarfs and for nonhomogeneous big-bang nucleosynthesis. If available, the resonant contributions to the rate are derived using recent experimental data. The direct capture rate is evaluated on the basis of a microscopic multichannel calculation of the C-14(alpha, gamma)O-18 reaction. Possible interference contributions are discussed. The present rate is compared to previous estimates of Hashimoto et al. (1986) and of Buchmann et al. (1988). 23 refs

  4. The C-14(alpha, gamma)O-18 reaction at astrophysical energies

    Energy Technology Data Exchange (ETDEWEB)

    Funck, C.; Langanke, K. (Muenster Universitaet (Germany, F.R.))

    1989-09-01

    The C-14(alpha, gamma)O-18 reaction rate is estimated for temperatures important for He flashes in white dwarfs and for nonhomogeneous big-bang nucleosynthesis. If available, the resonant contributions to the rate are derived using recent experimental data. The direct capture rate is evaluated on the basis of a microscopic multichannel calculation of the C-14(alpha, gamma)O-18 reaction. Possible interference contributions are discussed. The present rate is compared to previous estimates of Hashimoto et al. (1986) and of Buchmann et al. (1988). 23 refs.

  5. Synthesis and magnetostrictive properties of Pr1-xDyx(Fe0.8Co0.2)1.93 cubic Laves compounds

    Science.gov (United States)

    Shi, Y. G.; Chen, Z. Y.; Wang, L.; Hu, C. C.; Pan, Q.; Shi, D. N.

    2016-05-01

    The structure, magnetic properties and magnetostriction of high-pressure synthesized Pr1-xDyx(Fe0.8Co0.2)1.93 compounds were investigated. These compounds, which could not be readily synthesized under ambient pressure, exhibit single cubic Laves phase owing to the effects of high-pressure annealing. The Curie temperature increases with increasing x, indicating that 3d-4f coupling becomes stronger with the increase of Dy concentration. The saturation magnetization decreases with increasing x, which can be ascribed to the competition of sublattice magnetization. The easy magnetization direction of the compound lies along with x ≤ 0.05 while lies along when x ≥ 0.10. Meanwhile, the low-field magnetostriction λ∥ - λ⊥ of the compound system peaks at x = 0.05 and then decreases with increasing x, which reveals that the composition anisotropy compensation between Pr3+ and Dy3+ might be realized in Pr1-xDyx(Fe0.8Co0.2)1.93 system. Pr0.95Dy0.05(Fe0.8Co0.2)1.93 compound combines a large low-field magnetostriction (648 ppm at 3 kOe) and the merits of low-cost raw materials, which may make it a potential material for magnetostrictive application.

  6. C-14 and temperature variation around and after AD 775 - after the Dark Age Grand Minimum

    Science.gov (United States)

    Neuhäuser, Ralph; Neuhäuser, Dagmar L.

    2016-04-01

    We have compiled an extensive catalog of aurora observations from the Far and Near East as well as Europe for the time from AD 550 to 845. From historic observations of aurorae and sunspots as well as the C-14 and Be-10 data, we can date the end of the Dark Age grand minimum to about AD 690; we see strong activity after this period. We can fix the solar activity Schwabe cycle maxima and minima in the 7th and 8th centuries.. The strong 14-C increase in data with 1-yr time resolution in the AD 770s (e.g. Miyake et al. 2012) is still a matter of debate, e.g. a solar super-flare. In the last three millennia, there were two more strong rapid rises in 14-C - around BC 671 and AD 1795. All three 14-C variations are embedded in similar evolution of solar activity, as we can show with various solar activity proxies; secular evolution of solar wind plays an important role. The rises of 14-C - within a few years each - can be explained by a sudden strong decrease in solar modulation potential leading to increased radioisotope production. The strong rises around AD 775 and 1795 are due to three effects: (i) very strong activity in the previous cycles (i.e. very low 14-C level), (ii) the declining phase of a very strong Schwabe cycle, and (iii) a phase of very weak activity after the strong 14-C rise - very short and/or weak cycle(s) like the suddenly starting Dalton minimum. In addition to arXiv:1503.01581 and arXiv:1508.06745, we also discuss the temperature depression and new quasi-annual 10-Be data. If a temperature depression right after AD 775 for a few decades can be confirmed, this would be fully consistent with our suggestion: reduced solar activity since AD 775 (for a few decades like in the Dalton minimum). Otherwise, one would not expect such a temperature depression after a solar super-flare.

  7. Spectral analysis of colour-quenched and chemically quenched C-14 samples

    International Nuclear Information System (INIS)

    In this paper pairs of pulse height distribution curves, of C-14 samples, colour-quenched and chemically quenched was obtained. The possibility to choose a counting window in order to obtain the counting efficiency curves, for both type of quenching was studied. (Author) 7 refs

  8. Producing a new in-house C-14 standard by irradiating graphite

    International Nuclear Information System (INIS)

    Full text: Accelerator mass spectrometry (AMS) always performs measurements relative to a standard, which significantly improves the precision. C-14 measurements need a chemical treatment to transform carbon into graphite, to be used in the popular Cs-sputter sources. A homogeneous bulk of several gram of graphite containing C-14 would allow to study the performance of the mass spectrometer independent of sample preparation chemistry. Unfortunately, this material is not available so far. The aim was to produce such a new in-house standard for the VERA facility (University of Vienna). We started from dead (p.e. no C-14) graphite powder and irradiated it with thermal neutrons at the TRIGA Mark II reactor from the Institute of Atomic and Subatomic Physics (TU Vienna). Via the 13C(n, γ)14C reaction we produced a C-14 isotopic abundance in the natural range of ∼10-12. The challenge of this work was to deal with an inhomogeneous neutron flux and the low cross section for the mentioned above reaction, compared to the much more efficient 14N(n,p)14C. The homogeneity of the produced material was successfully verified by measurements of small aliquots. (author)

  9. Langtidseffekter av lave omega-3 nivåer i fôr på laksens helse

    OpenAIRE

    Ruyter, Bente; Bou, Marta; Bæverfjord, Grete; Østbye, Tone-Kari K; Ytrestøyl, Trine; Bjerke, Målfrid Tofteberg; Sigholt, Trygve; Berge, Gerd Marit

    2016-01-01

    Omega-3 fettsyrer er helt sentrale for en rekke biologiske funksjoner i kroppen, som for eksempel cellenes oppbygging, avlesing av arvematerialet og inflammasjons-respons. Det er for øvrig relativt lite kunnskap om hvor lite omega-3 i fôret oppdrettslaksen kan klare seg med uten at det går ut over helse og velferd. Hensikten med dette prosjektet har dermed vært å øke kunnskapen om hvilke konsekvenser lave nivåer av EPA og DHA i fôret til laks, over store deler av livssyklus, vil ha for fisken...

  10. Upper and lower bounds for the connective constants of self-avoiding walks on the Archimedean and Laves lattices

    International Nuclear Information System (INIS)

    We give improved upper and lower bounds for the connective constants of self-avoiding walks on a class of lattices, including the Archimedean and Laves lattices. The lower bounds are obtained by using Kesten's method of irreducible bridges, with an appropriate generalization for weakly regular lattices. The upper bounds are obtained as the largest eigenvalue of a certain transfer matrix. The obtained bounds show that, in the studied class of lattices, the connective constant is increasing in the average degree of the lattice. We also discuss an alternative measure of average degree

  11. Phase Composition of a CrMo0.5NbTa0.5TiZr High Entropy Alloy: Comparison of Experimental and Simulated Data

    OpenAIRE

    Fan Zhang; Senkov, Oleg N.; Jonathan D. Miller

    2013-01-01

    Microstructure and phase composition of a CrMo0.5NbTa0.5TiZr high entropy alloy were studied in the as-solidified and heat treated conditions. In the as-solidified condition, the alloy consisted of two disordered BCC phases and an ordered cubic Laves phase. The BCC1 phase solidified in the form of dendrites enriched with Mo, Ta and Nb, and its volume fraction was 42%. The BCC2 and Laves phases solidified by the eutectic-type reaction, and their volume fractions were 27% and 31%, respectively....

  12. Multiscale modeling of the stability of intermetallic phases

    Czech Academy of Sciences Publication Activity Database

    Vřešťál, Jan; Pavlů, Jana; Šob, Mojmír

    Daegu, 2009. s. 75-75. [The Korean Institute of Metals and Materials 2009 Fall Conference. 22.10.2009-23.10.2009, Daegu] Institutional research plan: CEZ:AV0Z20410507 Keywords : ab initio calculations * Laves and sigma phases * thermodynamic modelling Subject RIV: BJ - Thermodynamics

  13. Structural, electronic, and linear optical properties of organic photovoltaic PBTTT-C14 crystal

    Science.gov (United States)

    Li, Long-Hua; Kontsevoi, Oleg Y.; Rhim, S. H.; Freeman, Arthur J.

    2013-04-01

    Poly(2,5-bis(3-tetradecylthiophen-2yl)thieno(3,2-b)thiophene) (PBTTT-C14) is an important electro-optical polymer, whose three-dimensional crystal structure is somewhat ambiguous and the fundamental electronic and linear optical properties are not well known. We carried out first-principles calculations to model the crystal structure and to study the effect of side-chains on the physical structure and electronic properties. Our calculations suggest that the patterns of side-chain has little direct effect on the valence band maximum and conduction band minimum but they do have impact on the bandgap through changing the π-π stacking distance. By examining the band structure and wave functions, we conclude that the fundamental bandgap of the PBTTT-C14 crystal is determined by the conduction band energy at the Q point. The calculations indicate that the bandgap of PBTTT-C14 crystal may be tunable by introducing different side-chains. The significant peak in the imaginary part of the dielectric function arises from transitions along the polymer backbone axis, as determined by the critical-point analysis and the large optical transition matrix elements in the direction of the backbone.

  14. The re-establishment in the scaling factor of radiation dose rates (C-14) of homogeneous solid wastes in PWR

    International Nuclear Information System (INIS)

    The scaling factor of the isotope ratio C-14/Co-60 of the wastes generated at Ikata power plant exceeded 10 times of the current scaling factor. The reason of this fact was examined. Then, the scaling factor for C-14 in PWR plants was re-estimated. (M.H.)

  15. C-14 concentration measurement in aqueous samples using direct absorption method and liquid scintillation counting

    International Nuclear Information System (INIS)

    Cernavoda Nuclear Power Station is the only nuclear power plant in Romania and the only CANDU reactor operating in Europe. The Cernavoda Unit 1 is a pressurized heavy water reactor (PHWR) fuelled with natural uranium and moderated and cooled by heavy water. The routine operation of this type reactor and its auxiliary process systems results in the production of a variety of solid, liquid and gaseous radioactive wastes. Carbon-14 is produced mainly via a neutron capture reaction of oxygen-17 in the CANDU reactor. CANDU production and emission rates of C-14 are higher than those of other types of commercial reactors such as light water reactors and gas-cooled reactors. In order to fulfill the exigency of the monitoring program, we propose several studies to optimize C-14 determination in water samples. A complete C-14 measurement procedure adequate for natural level water samples has been developed. The characteristics and specificity of this new measurement technique are discussed and several comparisons with concurrent methods are investigated. Special emphases have been done for sample preparation technique and the direct absorption method has been used with few home-made improvements in order to increase the reproducibility and accuracy of this simple and less-time consumer method. The results confirmed the validity of the sample preparation and measurement procedures, providing an increased reproducibility compared to traditional techniques. A validation test using CaCO3 resulted from oyster shell and marble provided a mean value of 0.2137±0.0039 Bq/gC for an efficiency value of about 64% and a background value of 2.22cpm. The routine procedure was applied on different type of water. (author)

  16. Use of miniature C-14 counters in dating and authentication in the museum

    Energy Technology Data Exchange (ETDEWEB)

    Harbottle, G.; Sayre, E.V.; Stoenner, R.W.

    1983-01-01

    Curators often do not understand the basis for the C-14 method of age determination and its limitations. Purpose of this paper is to describe the underlying principles, and how these must influence the interpretation of the radiocarbon measurement of a museum specimen in terms of age. Several techniques for that measurement are described briefly, focussing on the miniature proportional counters that were developed for the Smithsonian Institution, and three museum problems are described which were attacked, and some interesting further research on museum objects that has been proposed. Finally some projections on the future applications of the different methods are made, in the context of museum work.

  17. Use of miniature C-14 counters in dating and authentication in the museum

    International Nuclear Information System (INIS)

    Curators often do not understand the basis for the C-14 method of age determination and its limitations. Purpose of this paper is to describe the underlying principles, and how these must influence the interpretation of the radiocarbon measurement of a museum specimen in terms of age. Several techniques for that measurement are described briefly, focussing on the miniature proportional counters that were developed for the Smithsonian Institution, and three museum problems are described which were attacked, and some interesting further research on museum objects that has been proposed. Finally some projections on the future applications of the different methods are made, in the context of museum work

  18. Uptake of C-14 tagged acetate by rice in a paddy soil-to-rice plant system

    International Nuclear Information System (INIS)

    Geological disposal of Transuranic (TRU) waste is planned to avoid radiation exposure to the public. One of the dominant nuclides contributing to the dose from TRU waste is C-14, which is long-lived and has very poor sorption properties on natural geological media. Therefore, there are some concerns regarding possible migration of C-14 to the living environments. For the public health safety, it is necessary to clarify pathways of C-14 to human beings in the environment. Intake of C-14 from food source is one of important pathways. In the present study, we examined transfer of C-14 to various parts of rice plant in a paddy soil-to-rice plant system. Rice seedlings in Wagner pots (n=12) were grown for about two months from 7 May 2012 under natural light. The grown plants were moved to a closed chamber on 5 July 2012. The rice plants were grown without water supply from 5 July 2012, and then one liter of C-14 tagged acetate (1.85 MBq) was supplied to the rice plants in the spiked group (n=8) just once on 9 July 2012. For the rice plants in the control group (n=4), uncontaminated water was supplied. These rice plants were air-dried after a harvest on 23 August 2012 and divided into four parts: white rice, bran, rice husk, and the stem and leaf part. The activities of C-14 in the divided parts and air-dried soil samples were determined with a liquid scintillation counting system. Radiocarbon was detected even in the rice plants of the control group. However, the C-14 activity in the soil of the control group was less than the detection limit (1.0 Bq/g). The C-14 activities for the control group decreased in the order of rice husk, bran, white rice, and the stem and leaf part. The detection of C-14 in the control group may be caused by the release of C-14 tagged carbon dioxide from the spiked group. That is, C-14 tagged acetate was converted to carbon dioxide by microbial activity in the spiked group, and then some of the released carbon dioxide was assimilated into

  19. Uptake of C-14 tagged acetate by rice in a paddy soil-to-rice plant system

    Energy Technology Data Exchange (ETDEWEB)

    Ishii, Nobuyoshi; Tagami, Keiko; Uchida, Shigeo [Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba 263-8555 (Japan)

    2014-07-01

    Geological disposal of Transuranic (TRU) waste is planned to avoid radiation exposure to the public. One of the dominant nuclides contributing to the dose from TRU waste is C-14, which is long-lived and has very poor sorption properties on natural geological media. Therefore, there are some concerns regarding possible migration of C-14 to the living environments. For the public health safety, it is necessary to clarify pathways of C-14 to human beings in the environment. Intake of C-14 from food source is one of important pathways. In the present study, we examined transfer of C-14 to various parts of rice plant in a paddy soil-to-rice plant system. Rice seedlings in Wagner pots (n=12) were grown for about two months from 7 May 2012 under natural light. The grown plants were moved to a closed chamber on 5 July 2012. The rice plants were grown without water supply from 5 July 2012, and then one liter of C-14 tagged acetate (1.85 MBq) was supplied to the rice plants in the spiked group (n=8) just once on 9 July 2012. For the rice plants in the control group (n=4), uncontaminated water was supplied. These rice plants were air-dried after a harvest on 23 August 2012 and divided into four parts: white rice, bran, rice husk, and the stem and leaf part. The activities of C-14 in the divided parts and air-dried soil samples were determined with a liquid scintillation counting system. Radiocarbon was detected even in the rice plants of the control group. However, the C-14 activity in the soil of the control group was less than the detection limit (1.0 Bq/g). The C-14 activities for the control group decreased in the order of rice husk, bran, white rice, and the stem and leaf part. The detection of C-14 in the control group may be caused by the release of C-14 tagged carbon dioxide from the spiked group. That is, C-14 tagged acetate was converted to carbon dioxide by microbial activity in the spiked group, and then some of the released carbon dioxide was assimilated into

  20. Dehydrocyclization of 2,2-dimethyl-4-(methyl-C14)-pentane and 3-(methyl-C14)-heptane over chromia-alumina

    International Nuclear Information System (INIS)

    The relative specific activities of the products obtained by processing the above C14-labelled hydrocarbons over a potassium and cerium-promoted chromia-alumina catalyst have been measured. Products were separated by gas-chromatographic techniques, burnt to carbon dioxide and assayed as barium carbonate, using an end-window Geiger-Mueller tube. The distribution of radioactivity between side chain and ring in the aromatic products was assessed by dealkylation over fluorinated alumina catalyst and the distribution between α and β carbon atoms of ethylbenzene, produced from methylheptane, by dealkylation to toluene and benzene over a nickel catalyst. The results obtained with the first compound are consistent with an over-all mechanism in which methyl groups at both ends of the molecule become attached at adjacent sites on the catalyst surface. Rearrangement at the trisubstituted end of the molecule to give a six-membered ring, followed by dehydrogenation, gives p-xylene with 50% activity in the methyl groups. Toluene produced during cyclization has an activity distribution indicating that rearrangement also occurs to a lesser extent at the other end of the molecule. The dehydrocyclization of methylheptane leads to the formation of the expected aromatics. However, the activity distribution shows that these have not arisen entirely by a simple ring-closure mechanism; a probable mechanism is the formation and subsequent rearrangement of C5, C6 and C7 ring intermediates, tending to randomize the distribution of active carbon. The labelled hydrocarbons were prepared on a one-gram scale by a Grignard reaction using a novel decomposition step. (author)

  1. COMPARATIVE ANALYSIS OF MODELS OF RAILWAY LOADS C14 AND LM71 FOR GIRDER BRIDGES

    Directory of Open Access Journals (Sweden)

    V. Artomov

    2014-01-01

    Full Text Available Purpose. The article analyzes the railway load LM71 for the purpose of its application in national design projects of the railway girder bridges. Purpose of the article is harmonization of national design codes of enginnering structures with the European standards (Eurocodes. Methodology. Analytical calculation methods (influence lines, the matrix analysis and computer programming are used in the article. Findings. Deflected mode parameters of the railway bridges under the influence of loads C14 and LM71 have certain differences. The extent of these differences depends on length, material of drift structures and also on dynamic coefficients. These dependences should be considered in national design codes and in harmonized with Eurocodes standards. In the further researches relationships between load C14 and models SW, HSLM taking into account various dynamic effects and trains speedis planned to determine. Originality. The presented results, in particular deflected mode parameters (including loads with dynamic coefficients, obtained for the first time. Practical value. Results of research are used in National Annex to the National Standard of Ukraine NSTU-N B EN 1991-2:2010. Eurocode 1. Actions on structures. Part 2. Traffic loads on bridges (EN 1991-2:2003.

  2. Effective modern C++ 42 specific ways to improve your use of C++11 and C++14

    CERN Document Server

    Meyers, Scott

    2015-01-01

    At first glance, C++11 and C++14 are defined by the new features they introduce, e.g., auto type declarations, move semantics, lambda expressions, and concurrency support. Information on these features is easy to come by, but learning to apply them effectively (such that the resulting software is correct, efficient, maintainable, and portable) is more challenging. That’s the role of this book. It describes how to write effective software using C++11 and C++14, i.e., using modern C++. Topics include: * The pros and cons of uniform initialization, noexcept specifications, perfect forwarding, and smart pointer make functions. * The relationships among std::move, std::forward, rvalues references, and universal references. * The most effective forms of lambda capture. * How best practices in “old” C++ programming (i.e., C++98) require revision for modern C++. Effective Modern C++ follows the proven format of Scott Meyers’ earlier Effective books (Effective C++, More Effective C++, and Effective STL), but c...

  3. Chemoenzymatic synthesis and antileukemic activity of novel C9- and C14-functionalized parthenolide analogs.

    Science.gov (United States)

    Tyagi, Vikas; Alwaseem, Hanan; O'Dwyer, Kristen M; Ponder, Jessica; Li, Qi Ying; Jordan, Craig T; Fasan, Rudi

    2016-09-01

    Parthenolide is a naturally occurring terpene with promising anticancer properties, particularly in the context of acute myeloid leukemia (AML). Optimization of this natural product has been challenged by limited opportunities for the late-stage functionalization of this molecule without affecting the pharmacologically important α-methylene-γ-lactone moiety. Here, we report the further development and application of a chemoenzymatic strategy to afford a series of new analogs of parthenolide functionalized at the aliphatic positions C9 and C14. Several of these compounds were determined to be able to kill leukemia cells and patient-derived primary AML specimens with improved activity compared to parthenolide, exhibiting LC50 values in the low micromolar range. These studies demonstrate that different O-H functionalization chemistries can be applied to elaborate the parthenolide scaffold and that modifications at the C9 or C14 position can effectively enhance the antileukemic properties of this natural product. The C9-functionalized analogs 22a and 25b were identified as the most interesting compounds in terms of antileukemic potency and selectivity toward AML versus healthy blood cells. PMID:27396927

  4. Phase Transformation in Cast Superaustenitic Stainless Steels

    Energy Technology Data Exchange (ETDEWEB)

    Nathaniel Steven Lee Phillips

    2006-12-12

    Superaustenitic stainless steels constitute a group of Fe-based alloys that are compositionally balanced to have a purely austenitic matrix and exhibit favorable pitting and crevice corrosion resistant properties and mechanical strength. However, intermetallic precipitates such as sigma and Laves can form during casting or exposure to high-temperature processing, which degrade the corrosion and mechanical properties of the material. The goal of this study was to accurately characterize the solid-solid phase transformations seen in cast superaustenitic stainless steels. Heat treatments were performed to understand the time and temperature ranges for intermetallic phase formations in alloys CN3MN and CK3MCuN. Microstructures were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy and wavelength dispersive spectroscopy (EDS, WDS). The equilibrium microstructures, composed primarily of sigma and Laves within purely austenitic matrices, showed slow transformation kinetics. Factors that determine the extent of transformation, including diffusion, nucleation, and growth, are discussed.

  5. Hyperfine fields and magnetic momente in Laves intermetallic compounds AFe2(A=Zr, Y, Sc and Gd)

    International Nuclear Information System (INIS)

    Hyperfine fields (HFF) on impurity nuclei 27Al and 45Sc in the Laves cubic compounds ZrFe2, YFe2, ScFe2 and GdFe2 are measured by the method of pulsed nuclear magnetic resonance at 4.2 K. Using the data on 57Fe ad 27Al HFF the contributions to 57Fe HFF from local magnetic momentum of iron atoms μ0(Fe) are singled out, the values μ0(Fe) amd μ(A) are estimated. It is shown that HFF on 45Sc nuclei contain both contributions from local magnetic momentum of scandium atoms and from magnetic momenta of atoms in the nearest spheres. The contributions are evaluated for ZrFe2 and ScFe2

  6. Paleoclimatic information from deuterium and oxygen-18 in C-14 dated North Saharian groundwaters; groundwater formation in the past

    International Nuclear Information System (INIS)

    A statistical presentation of C-14 groundwater ages for various regions of the Northern Sahara reflects the alternating sequence of humid and arid periods in the late Pleistocene and Holocene. Groundwaters older than 20000 y B.P. are found all over the Sahara. Isoline-presentation of the Continental Effect in deuterium and oxygen-18 of Saharian groundwater is similar to the one in modern European groundwater. This similarity proves the Western Drift influence when in the past winter rains were sufficient for groundwater formation in the Sahara (great pluvial). The postpluvial humid phases of the Sahara during the Holocene were probably of decreasing importance from west to east. The lower deuterium excess d = delta D - 8 x delta18O observed in old Saharian groundwaters is interpreted to be due to a lower moisture deficit of the air over the ocean during the last ice-age. Extremely high D- and O-18 contents of modern groundwater in the Sahel zone south of the Sahara are probably due to summer rain originating from tropical rain forest evapotranspiration. (orig.)

  7. Can the C-14 urea breath test reflect the extent and degree of ongoing helicobacter pylori infection

    International Nuclear Information System (INIS)

    The C-14 urea breath test (C-14 UBT) is the most specific noninvasive method to detect Helicobacter (H) pylori infection. We investigated if the C-14 UBT can reflect the presence and degree of H. pylori detected by gastroduodenoscopic biopsies (GBx). One hundred fifty patients (M:F=83:67,age 48.6±11.2 yrs) underwent C-14 UBT, rapid urease test (CLO test) and GBx on the same day. For the C-14 UBT, a single breath sample was collected at 10 minutes after ingestion of C-14 urea (137 KBq) capsule and counting was done in a liquid scintillation counter for 1 minute, and the results were classified as positive (≥200 dpm), intermediate ( 50 ∼ 199 dpm) or negative ( < 50 dpm). The results of CLO tests were classified as positive or negative according to color change. The results of GBx on giemsa stain were graded 0 (normal) to 4(diffuse) according to the distribution of H. pylori by the Wyatt method. We compared C-14 UBT results with GBx grade as a gold standard. In the assessment of the presence of H. pylori infection, the C-14 UBT global performance yielded sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of 92.5%, 88.4%, 97.1%, 88.4% and 91.3%, respectively. However, the CLO test had sensitivity, specificity, PPV, NPV and accuracy of 83.2%, 81.4%, 91.8%, 81.4% and 82.7%, respectively. The quantitative values of the C-14 UBT were 45 ± 27 dpm in grade 0, 707 ±584 dpm in grade 1, 1558±584 dpm in grade 2, 1851±604 dpm in grade 3, and 2719 ± 892 dpm in grade 4. A significant correlation (r=0.848, p<0.01) was found between C-14 UBT and the grade of distribution of H. pylori infection on GBx with giemsa stain. We conclude that the C-14 UBT is a highly accurate, simple and noninvasive method for the diagnosis of ongoing H. pylori infection and reflects the degree of bacterial distribution

  8. TL, OSL and C-14 dating results of the sediments and bricks from mummified nuns' grave.

    Science.gov (United States)

    Tudela, Diego R G; Tatumi, Sonia H; Yee, Márcio; Brito, Silvio L M; Morais, José L; Morais, Daisy de; Piedade, Silvia C; Munita, Casimiro S P; Hazenfratz, Roberto

    2012-06-01

    This paper presents the results of TL and OSL dating of soil and fragments of bricks from a grave, which was occupied by two mummified nuns, found at "Luz" Monastery, located in the state of São Paulo, Brazil. The TL and OSL ages were compared to C-14 dating ones obtained from bone collagens of the mummies. The majority of the ages is related to the eighteenth century. The gamma-ray spectroscopy was used to evaluate natural radioisotope concentrations in the samples, and by using these concentrations the annual dose rates, from 3.0 to 5.3 Gy/kyr, were obtained. Neutron activation analysis was performed and the radioisotope contents results are in agreement with those obtained by gamma-ray spectroscopy. The contents of U, Th and Ce elements were higher than those found in usual sediments. PMID:22569952

  9. TL, OSL and C-14 dating results of the sediments and bricks from mummified nuns' grave

    International Nuclear Information System (INIS)

    This paper presents the results of TL and OSL dating of soil and fragments of bricks from a grave, which was occupied by two mummified nuns, found at 'Luz' Monastery, located in the state of Sao Paulo, Brazil. The TL and OSL ages were compared to C-14 dating ones obtained from bone collagens of the mummies. The majority of the ages is related to the eighteenth century. The gamma-ray spectroscopy was used to evaluate natural radioisotope concentrations in the samples, and by using these concentrations the annual dose rates, from 3.0 to 5.3 Gy/kyr, were obtained. Neutron activation analysis was performed and the radioisotope contents results are in agreement with those obtained by gamma-ray spectroscopy. The contents of U, Th and Ce elements were higher than those found in usual sediments. (author)

  10. Bioaccumulation of sediment-bound Cr-51, Ni-63 and C-14 by benthic invertebrates

    International Nuclear Information System (INIS)

    Sediments in many areas of the Baltic Sea are highly contaminated with particle-reactive trace metals and/or radionuclides. These may be re-mobilised into aquatic food chains by bioaccumulation into benthic organisms. In this study, we examined and compared assimilation efficiencies and bioaccumulation kinetics (rates of uptake and elimination) of sediment-associated Cr-51, Ni-63 and organic-associated C- 14 in three common benthic invertebrates from the Baltic Sea (the bivalve Macoma balthica, the amphipod Monoporeia affinis and the priapulid worm Halicryptus spinulosus). There were differences between animals and radionuclides in both the rate of uptake and elimination and the maximum amount accumulated. Understanding how and to what degree different deposit-feeding benthic invertebrates are exposed to and bio-accumulate sediment-associated metals are important for both ecological risk assessment and management decisions in coastal ecosystems. (author)

  11. Segregation effects and phase developments during solidification of alloy 625

    DEFF Research Database (Denmark)

    Højerslev, Christian; Tiedje, Niels Skat; Hald, John

    2006-01-01

    material contained gamma-phase, Laves phase and, if carbon was dissolved in the liquid, niobium rich carbides formed. Molybdenum and niobium showed strong tendencies to segregate. Their segregation was balanced by inverse segregation of nickel and iron. The chromium concentration remained almost constant...... in gamma in the entire matrix material. Addition of carbon did not cause detectable alterations of the material that experienced planar front solidification. However, it promoted the formation of niobium rich carbides in the material that solidified eutectic-like. Thus, this material differed from...... that of the pure sample in constitution, and consequently in gamma-phase composition. Niobium rich carbides formed prior to Laves phase; in carbon rich volumes only the carbides form. As compared to the pure sample, the sample enriched in iron had decreased global minimal solute concentration in the...

  12. Study of carbon-isotope exchange reactions between potassium cyanide and some carbonates, and their use for obtaining C14-labelled potassium cyanide

    International Nuclear Information System (INIS)

    The authors examine the results of a study on the isotope exchange of potassium cyanide with compounds differing greatly from it both in composition and structure, such as carbonates of alkaline and alkali-earth metals. The carbon-isotope exchange reaction in the KC12N-BaC14O3 system was studied at 600-800oC. The ratio between the components of this system and those given below agreed with the equimolecular ratio. The authors show that at high temperatures complete exchange between these compounds can be secured. The exchange reaction begins when the cyanide melt is formed; later it occurs between the liquid and the solid phases, and its speed increases with temperature; at 800oC it is completed in 2 h. With carbonates of alkali metals the exchange reaction occurs in the melt and is completed at lower temperatures. The authors obtained cyanide-labelled potassium by the following method : (1) The isotope exchange reaction KC12N-BaC14O3 is produced at 800oC in 2 h. (2) The mixture KCN+BaCO3 is separated by extracting the KCN with liquid ammonia in a circulating extractor. By exchanging the equimolecular quantities KCN and BaCO3, potassium cyanide is obtained with a chemical yield of more than 90% and a basic-substance content of 96-97%. By using BaCO3 with a high specific activity (60-70 mc/g), a KCN specific activity of over 80 mc/g may be obtained. The barium carbonate depleted of isotope C14 regenerates after the ammonia extraction without appreciable loss. (author)

  13. Magnetic quenching of the electric quadrupole interaction of 181Ta in ferromagnetic laves phases AFe2 (A = Zr, Y, Lu)

    International Nuclear Information System (INIS)

    The results of time-differential perturbed angular correlation (TDPAC) measurements of the anisotropy of the 133 to 482 keV γ-ray cascade in 181Ta are presented. The damping of the precession amplitudes in the TDPAC spectra is considered to be due to the electric quadrupole interaction of nuclei with randomly distributed electric field gradients (EFG). The perturbation of the correlation then can be accounted for by a parameter ΓQ which characterizes the width of the EFG distribution. The ΓQ values for 181Ta in ZrFe2, YFe2, and LuFe2 in para- and ferromagnetic states are given and discussed. Results indicate very strong influence of the state of magnetic ordering on the electric quadrupole interaction constant in the studied substances

  14. Structure and hydrogen storage properties of the hexagonal Laves phase Sc(Al1-xNix)(2)

    Czech Academy of Sciences Publication Activity Database

    Sahlberg, M.; Angstrom, J.; Zlotea, C.; Beran, Přemysl; Latroche, M.; Gomez, C. P.

    2012-01-01

    Roč. 196, DEC 2012 (2012), s. 132-137. ISSN 0022-4596 R&D Projects: GA MŠk(XE) LM2011019 Institutional support: RVO:61389005 Keywords : metal hydrides * hydrogen storage * X-ray diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.040, year: 2012

  15. Ingestion dose pathway parameters of H-3 and C-14 in Korea

    Energy Technology Data Exchange (ETDEWEB)

    Yang-Geun Chung; Gab-Bock Lee; Sun-Young Bang [Korea Electric Power Research Institute (Korea, Republic of); Seung-Ong Lee [Korea Hydro and Nuclear Power Cooperation (Korea, Republic of)

    2006-07-01

    Full text of publication follows: H-3 and C-14 are the main nuclides for public ingestion dose around nuclear power plants in Korea. Key parameters of H-3 and C-14 ingestion dose pathways are the fractions of moisture, hydrogen, and carbon in agricultural vegetation. In this study, representative values of the moisture, hydrogen, and carbon contents for categorized food groups were established. The food stuffs are classified into four groups such as grain, leafy vegetable, root vegetable, and fruit. Methods Weighting factors for individual food items were considered to calculate representative values of each food group using the 2001-2002 national dietary survey, published by the Ministry of Health and Welfare (MOHW). The weighting factor for individual food stuff was determined by the ratio of each food item to the total intake of each food group. Representative values of the moisture, hydrogen, and carbon contents for the four food groups were calculated using the annual weighting factor and the fractions of moisture, hydrogen, and carbon of individual food stuff based on the sixth revision of Food Composition Table published by the Rural Living Science Research Institute (RLSI). Results The weighting factor of rice in grain group was 95% on a yearly basis. Those of Chinese cabbage in leafy vegetable group and radish in root vegetable group were 58% and 52%, respectively. The fruit consumption varied with seasons. Annual weighting factors of apple, persimmon, water melon, and pear in fruit were 21%, 18%, 17%, and 15%, respectively. The respective fractions of moisture in grain, leafy vegetable, root vegetable, and fruit were 10.8%, 93.0%, 88.3%, and 88.0%: those of hydrogen were 5.6%, 0.4%, 0.7%, and 0.74%: those of carbon were 39.68%, 2.84%, 4.98%, and 5.23%. The hydrogen fraction of root vegetable was 75% larger than that of leafy vegetable. The values of moisture, hydrogen, and carbon contents in agricultural vegetation calculated from the Food Composition

  16. TL, OSL and C-14 dating results of the sediments and bricks from mummified nuns' grave

    Directory of Open Access Journals (Sweden)

    Diego R.G. Tudela

    2012-06-01

    Full Text Available This paper presents the results of TL and OSL dating of soil and fragments of bricks from a grave, which was occupied by two mummified nuns, found at "Luz" Monastery, located in the state of São Paulo, Brazil. The TL and OSL ages were compared to C-14 dating ones obtained from bone collagens of the mummies. The majority of the ages is related to the eighteenth century. The gamma-ray spectroscopy was used to evaluate natural radioisotope concentrations in the samples, and by using these concentrations the annual dose rates, from 3.0 to 5.3 Gy/kyr, were obtained. Neutron activation analysis was performed and the radioisotope contents results are in agreement with those obtained by gamma-ray spectroscopy. The contents of U, Th and Ce elements were higher than those found in usual sediments.Este artigo apresenta os resultados de datação por TL e OSL de solos, e fragmentos de tijolos de um túmulo, que foi ocupado por duas freiras mumificadas encontradas no Mosteiro da "Luz", localizado no Estado de São Paulo, Brasil. As idades encontradas por TL e OSL foram comparadas às obtidas a partir de C-14 dos colágenos contidos em amostras de osso das múmias. A maioria das idades obtidas são do século XVIII. A espectroscopia de radiação-gama foi utilizada para avaliar concentrações de radioisótopos naturais nas amostras e para calcular as taxas de dose anual que resultaram em 3,0 a 5,3 Gy/kano. As concentrações radioativas são próximas daquelas obtidas através de Análise por Ativação de Nêutrons. Os conteúdos de elementos U, Th e Ce são superiores aos encontrados na maioria dos sedimentos.

  17. A role in immunity for Arabidopsis cysteine protease RD21, the ortholog of the tomato immune protease C14.

    Directory of Open Access Journals (Sweden)

    Takayuki Shindo

    Full Text Available Secreted papain-like Cys proteases are important players in plant immunity. We previously reported that the C14 protease of tomato is targeted by cystatin-like EPIC proteins that are secreted by the oomycete pathogen Phytophthora infestans (Pinf during infection. C14 has been under diversifying selection in wild potato species coevolving with Pinf and reduced C14 levels result in enhanced susceptibility for Pinf. Here, we investigated the role C14-EPIC-like interactions in the natural pathosystem of Arabidopsis with the oomycete pathogen Hyaloperonospora arabidopsidis (Hpa. In contrast to the Pinf-solanaceae pathosystem, the C14 orthologous protease of Arabidopsis, RD21, does not evolve under diversifying selection in Arabidopsis, and rd21 null mutants do not show phenotypes upon compatible and incompatible Hpa interactions, despite the evident lack of a major leaf protease. Hpa isolates express highly conserved EPIC-like proteins during infections, but it is unknown if these HpaEPICs can inhibit RD21 and one of these HpaEPICs even lacks the canonical cystatin motifs. The rd21 mutants are unaffected in compatible and incompatible interactions with Pseudomonas syringae pv. tomato, but are significantly more susceptible for the necrotrophic fungal pathogen Botrytis cinerea, demonstrating that RD21 provides immunity to a necrotrophic pathogen.

  18. Changes in ocean meridional overturning circulation over glacial termination I - The global record of marine C-14 paleoreservoir ages 23 - 13 cal. ka

    International Nuclear Information System (INIS)

    Dramatic climate changes occurred during early last deglacial times, 19.0-14.5 cal. ka. They were linked to most fundamental recent changes in ocean circulation, which likely contributed to major shifts in CO2 transfer from ocean to atmosphere. Marine radiocarbon (C-14) paleoreservoir ages provide unique new insights into the fate of paleo-water masses associated with changes in meridional overturning circulation (MOC). These ages are monitored at an ever growing number of key locations in all three oceans by means of a new C-14 plateau tuning technique. Opposite trends in paleoreservoir ages indicate a short-lasting phase of deep and intermediate-water formation in the North Pacific 17.5 to less than 14.6 cal. ka. This event was coeval with a brief northward reversal of Denmark Strait Overflow waters in the North Atlantic, the source region of modern global MOC, and a dramatic cooling of North Atlantic and Eurasian climate (Heinrich-1 event)

  19. Determination of the carbon content of domestic farm produces to estimate offsite C-14 ingestion dose

    International Nuclear Information System (INIS)

    The carbon content of grains, leafy and root vegetables, and fruits which the Koreans usually eat were calculated to use in the estimation of offsite C-14 ingestion dose. With the data of food intake per day in the Report on 1998 national health and nutrition survey- dietary intake survey, 5 age-group integrate d intake of the 4 farm produce groups were extracted for food items and the amount. Intake percentage in each food group were taken as food weighing factor for the foods. Carbon content was calculated using protein, fat, and carbohydrate content of the foods, and multiplied by the corresponding food weighing factor to derive the content of the food groups. The calculated carbon content of grains, leafy and root vegetables, and fruits were 39.%, 4.2%, 8.0%, and 5.9% respectively. Grains and fruits were not much different from ODCM for carbon content, but vegetables were higher by 0.7%∼4.5%

  20. Comparison of fusion cross sections for 10B + 16O and 12C + 14N systems

    International Nuclear Information System (INIS)

    The cross sections for fusion are compared for the 10B + 16O and 12C + 14N system for bombarding energies up to 17 MeV/A. The energy spectra, angular distribution and relative yields of the evaporation residues are extracted and, by comparison to simple kinematical analysis and Hauser-Feshbach calculations, it is concluded that they are consistent with complete fusion and equilibrium decay. Coincidence measurements for the 14N + 12C system at Esub(14N) = 182 MeV are also presented and confirm the identification of evaporation residues based on singles measurements of the Z distributions. The excitation functions for fusion for the 14N + 12C and 10B + 16O systems show significant differences that cannot be explained in terms of simple macroscopical models. For the highest energies studied the fusion cross sections decrease as 1/Esub(cm) for both systems, confirming the existence of a maximum absolute angular momentum limit of approximately 27h. (author)

  1. Surface adsorption of sulfonated poly(phenylene sulfone)/C14TAB mixtures and its correlation with foam film stability.

    Science.gov (United States)

    Uhlig, Martin; Miller, Reinhard; Klitzing, Regine von

    2016-07-21

    Polyelectrolyte/surfactant mixtures of rigid monosulfonated poly(phenylene sulfone) (sPSO2-220) and tetradecyl trimethylammonium bromide (C14TAB) were investigated by surface tension, surface elasticity and foam film stability measurements. The results were compared to former measurements of polyelectrolyte/surfactant mixtures containing more flexible polyelectrolytes (PAMPS or PSS and C14TAB). For all polyelectrolyte/surfactant mixtures an increased surface adsorption in comparison to the pure surfactant was detected. Moreover, sPSO2-220/C14TAB mixtures showed a much higher surface activity and foam film stability than mixtures with more flexible polyelectrolytes. The results presented give insight into the surface adsorption and foam film formation of rigid polyelectrolyte/surfactant mixtures. Therefore, this study helps to understand the role of polyelectrolyte backbone rigidity in the formation and stabilization of foam films made from polyelectrolyte/surfactant mixtures. PMID:27338310

  2. The stepwise selection for ketoconazole resistance induces upregulation of C14-demethylase (CYP51 in Leishmania amazonensis

    Directory of Open Access Journals (Sweden)

    Valter Viana Andrade-Neto

    2012-05-01

    Full Text Available Ketoconazole is a clinically safe antifungal agent that also inhibits the growth of Leishmania spp. A study was undertaken to determine whether Leishmania parasites are prone to becoming resistant to ketoconazole by upregulating C14-demethylase after stepwise pharmacological pressure. Leishmania amazonensis promastigotes [inhibitory concentration (IC50 = 2 µM] were subjected to stepwise selection with ketoconazole and two resistant lines were obtained, La8 (IC50 = 8 µM and La10 (IC50 = 10 µM. As a result, we found that the resistance level was directly proportional to the C14-demethylase mRNA expression level; we also observed that expression levels were six and 12 times higher in La8 and La10, respectively. This is the first demonstration that L. amazonensis can up-regulate C14-demethylase in response to drug pressure and this report contributes to the understanding of the mechanisms of parasite resistance.

  3. Wine ethanol C-14 as a tracer for fossil fuel CO2 emissions in Europe: Measurements and model comparison

    OpenAIRE

    Palstra, Sanne W. L.; Karstens, Ute; Streurman, Harm-Jan; Meijer, Harro A.J.

    2008-01-01

    C-14 (radiocarbon) in atmospheric CO2 is the most direct tracer for the presence of fossil-fuel-derived CO2 (CO2-ff). We demonstrate the C-14 measurement of wine ethanol as a way to determine the relative regional atmospheric CO2-ff concentration compared to a background site ("regional CO2-ff excess'') for specific harvest years. The carbon in wine ethanol is directly back traceable to the atmospheric CO2 that the plants assimilate. An important advantage of using wine is that the atmosphere...

  4. p73 G4C14 to A4T14 polymorphism is associated with colorectal cancer risk and survival

    Institute of Scientific and Technical Information of China (English)

    Kyung-Eun; Lee; Young-Seoub; Hong; Byoung-Gwon; Kim; Na-Young; Kim; Kyoung-Mu; Lee; Jong-Young; Kwak; Mee-Sook; Roh

    2010-01-01

    AIM:To analyze the association between the p73 G4C14-to-A4T14 polymorphism(a.k.a.,the GC/AT variation) and colorectal cancer risk and survival in the Korean population,and to evaluate the relationships between p73 polymorphism and the p73 protein expression or clinicopathological characteristics of colorectal cancer.METHODS:Three hundred and eighty-three histologically confirmed cases and 469 healthy controls,recruited at one teaching hospital in Pusan,Korea from 2001 and 2007,were genotyped for p73 G4C14-t...

  5. High temperature deformation and ternary alloying of NbCr2 Laves intermetallics

    International Nuclear Information System (INIS)

    A study has been conducted to examine the effect of ternary alloying elements on high temperature deformation of the C15 NbCr2 based intermetallics in Nb-Cr-X (X = V, Mo and W) alloy systems, which have attractive properties as high temperature structural materials. The high temperature deformation of the C15 NbCr2 intermetallics can be improved by two alloying methods. One method is based on geometrical consideration for site occupation and atomic size factor of component elements and additive elements in the single phase C15 lattice; addition of Mo and V can promote dislocation movement without introducing significant hardening. The other method is based on microstructural modification through ternary alloying; moderate addition of these elements results in a variety of duplex microstructure consisting of the C15 phase and bcc solid solution without forming any intermediate phases, and can enhance the high temperature deformability. Particularly, alloys with duplex microstructure equilibrating with Cr-rich bcc solid solution is shown to exhibit superior deformability. Also, lattice property of the additive atoms in the C15 structure and phase relation between the C15 structure and the bcc solid solution are investigated by OM, XRD, TEM and ALCHEMI observations and then discussed in association with observed mechanical behavior

  6. Phase diagram determination and thermodynamic modeling of the Cu-Mg-Si system

    Directory of Open Access Journals (Sweden)

    Zhao J.

    2016-01-01

    Full Text Available 13 ternary Cu-Mg-Si alloys were prepared by means of the powder metallurgy method. Phase equilibria at 500 and 700 oC of the Cu-Mg-Si system were determined using X-ray diffraction analysis (XRD. The existence of 3 ternary compounds in this system was verified: CuMgSi_Sigma (Cu16Mg6Si7, Tau (Cu3Mg2Si, and Laves ((Cu0.8Si0.22(Mg0.88Cu0.12. A thermodynamic modeling for the Cu-Mg-Si system was then conducted on the basis of the experimental data obtained in this work and those critically reviewed from the literature. The complex phase relationship between Laves phase and other phases has been successfully modeled in this work. Comparisons between the calculated and the measured phase diagrams show that most of the experimental data can be reproduced by the presently obtained thermodynamic parameters.

  7. Dating raised bogs : New aspects of AMS C-14 wiggle matching, a reservoir effect and climatic change

    NARCIS (Netherlands)

    Kilian, MR; VanDerPlicht, J; VanGeel, B; Geel, B. van

    1995-01-01

    High resolution AMS dating of Holocene raised bog deposits (Engbertsdijksvenen, The Netherlands) shows natural C-14 variations (wiggles) which can be matched with the dendrochronological calibration curve. Comparison of our results with other, conventionally dated peat cores and the Delta(14)C recor

  8. Rapid graphite target preparation with sealed tube zinc reduction method for C-14 dating by MICADAS

    International Nuclear Information System (INIS)

    Complete text of publication follows. In most cases the last step of the sample preparation for 14C dating by AMS is to produce graphite from the pure CO2 gas samples. Catalytic reaction is generally used to produce graphite for which stabilized temperature reaction cells are developed in certain laboratories. The properties (e.g. purity, conductivity) of the produced graphite vitally influence the quality of the AMS measurement. Although the internationally validated hydrogen reduction graphitization line of Hertelendi Laboratory of ATOMKI is able to produce high quality graphite for AMS C-14 analyses, the throughput of the prepared targets is highly limited. In this study we were looking for a rapid production and low cost graphitization method, whereby we are capable to handle numerous biomedical and environmental samples per day. The sealed tube zinc reduction method mostly suits to these criteria (Figure 1). We have adapted the method in ATOMKI and the goal of our study was to find out the proper conditions of the graphitization process. We have analyzed how does the graphitization time (240 - 3720 min) and the amount of zinc (30, 50 and 80 mg) and titanium hydride (7, 10 and 12 mg) reagents influence the value of the 12C ion current and the measured radiocarbon content of the sample and how big the caused isotope fractionation. Important task was to reach the achievable minimum background level and decrease the δ13C shift as minimal as possible. We have also investigated the reproducibility of graphitization process and examined the radiocarbon content of graphite targets made of oxalic acid standard (NIST-SRM-4990c). All of the graphite targets were prepared in ATOMKI laboratory and the AMS measurements were carried out on the MICADAS type accelerator mass spectrometer, developed and hosted in ETHZ, Zuerich. The amount of TiH2 we have examined does not have any kind of influence on the important features of the produced graphite. On the other hand the

  9. Investigation of phases obtained from the Ce.sub.20./sub.Ru.sub.60./sub.Si.sub.20./sub. composition

    Czech Academy of Sciences Publication Activity Database

    Vejpravová, J.; Sechovský, V.; Prokleška, J.; Daniš, S.; Jurek, Karel

    2008-01-01

    Roč. 466, 1-2 (2008), s. 17-25. ISSN 0925-8388 Institutional research plan: CEZ:AV0Z10100521 Keywords : rare earth compounds * laves phase * superconductivity * ternary Ce-Ru-Si system Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.510, year: 2008

  10. Phase diagram and inhomogeneity of (TbDy)-Fe(T) (T=Mn, Co, Al, Ti) systems

    International Nuclear Information System (INIS)

    The Tb-Dy-Fe ternary phase diagram and its Tb0.3Dy0.7-Fe section in the region of the magnetostrictive Laves phase have been investigated. Different segregation behavior for Tb and Dy was proposed and experimentally confirmed. The deviation of the TbDyFe Laves phase composition from its stoichiometric composition and the small Fe solubility range of the Laves phase were also determined. Based on phase selection theory, the pseudocongruent crystallization of REFe2 phase was confirmed. The inhomogeneity of Tb0.3Dy0.7(FeT)1.95 (T=Mn, Co, Al, Ti) alloys has also been investigated. Substitution of Fe by T elements always gave inhomogeneous as-cast alloys. The new phases Fe2Ti and RE2(FeCo) were observed. Obvious composition variations of Tb(Dy) and Fe(Mn) were found, which could be explained as resulting from microsegregation. Homogeneous phases could be obtained after homogenizing annealing while the new phases and the high Tb content in the RE phase remained. The effects of the inhomogeneity on the alloy magnetostrictive properties were also discussed. (orig.)

  11. Models used in the SFR1 SAR-08 and KBS-3H safety assessments for calculation of C-14 doses

    International Nuclear Information System (INIS)

    This report presents a set of simplified models for assessment of human exposures resulting from potential underground releases of C-14. These models were used in the SFR1 SAR08 and KBS-3H safety assessments. The proposed models can be used to assess continuous, as well as pulse-like C-14 releases, to various types of biosphere objects: forest ecosystems, agricultural lands, sea basins and lakes. It is also possible to make assessments of exposures resulting from the use of contaminated fresh waters, for example from an impacted well, for irrigation of vegetables. Models are also proposed for scenarios where lakes and sea basins are transformed into terrestrial objects due to land rise, filling of lakes and other natural or human induced processes. The exposure pathways considered in dose calculations with the models are: ingestion of contaminated food and water for both terrestrial and aquatic ecosystems, inhalation of contaminated air for terrestrial ecosystems. The exposure by external irradiation is not considered, as C-14 is a pure low energy beta emitter. The report provides an overview of the behaviour of C-14 in the environment, including an outline of the conceptual assumptions implicit in the proposed models. The proposed models are based on the so-called specific activity approach, which has been recommended by the UNSCEAR and the IAEA for assessment of doses resulting from C-14 releases to the environment from nuclear installations. The equations for estimation of the C-14 specific activities in environmental compartments have been derived from a combination of several realistic and conservative assumptions, which are documented and justified in the report. The models can be used in safety assessments of geological repositories of radioactive waste, to carry out cautious, but still not over conservative dose estimations, which can be compared with regulatory dose constrains. Comparative studies with the models indicate that the worse case situations

  12. Influence of N-15 enrichment on neutronics, costs and C-14 production in nitride fuel cycle scenarios

    International Nuclear Information System (INIS)

    The C-14 production for different closed fuel cycle scenarios has been investigated. If nitride fuel is used in fast reactors and ADSs dedicated to management of plutonium and minor actinides, an N-15 enrichment level of about 99% is required for the nitride cores to produce the same amount of C-14 as the oxide cores in the power park. The corresponding cost penalty for fuel fabrication is estimated to be larger than 25%. If reprocessing is included in the costs for fuel operations, the penalty is of the order of 5-10%, provided that a closed gas cycle is implemented for the fabrication. If nitride fuels are used only for minor actinide management in ADS, the required enrichment level is about 93%, and the cost penalty is less than 10%. (author)

  13. Reexposure and advection of C-14-depleted organic carbon from old deposits at the upper continental slope

    OpenAIRE

    Tesi, Tommaso; Goñi, Miguel A.; Langone, Leonardo; Puig, Pere; Canals, Miquel; Nittrouer, Charles A.; Durrieu De Madron, Xavier; Calafat, Antoni; Palanques, Albert; Heussner, Serge; Davies, Maureen H.; Drexler, Tina M.; Fabres, Joan; Miserocchi, Stefano

    2010-01-01

    Outcrops of old strata at the shelf edge resulting from erosive gravity-driven flows have been globally described on continental margins. The reexposure of old strata allows for the reintroduction of aged organic carbon (OC), sequestered in marine sediments for thousands of years, into the modern carbon cycle. This pool of reworked material represents an additional source of C-14-depleted organic carbon supplied to the ocean, in parallel with the weathering of fossil organic carbon delivered ...

  14. The use of C-14 as tracer in the carbon flow assimilated by the plants (maize, sugar cane, bean)

    International Nuclear Information System (INIS)

    The flow of carbon in three different crops (maize, beans and sugar cane) was studied by use of C-14. The plants were exposed to an atmosphere with a constant concentration of the tracer for 12 hours in a biosynthesis chamber. The detection of the isotope permitted the distribution and concentration of the photosynthetates in the various organs of the plants to be followed. (M.A.C.)

  15. Application of the Trojan Horse Method to study neutron induced reactions: the O-17(n, alpha)C-14 reaction

    Czech Academy of Sciences Publication Activity Database

    Gulino, M.; Spitaleri, C.; Guardo, G. L.; Lamia, L.; Cherubini, S.; Burjan, Václav; Hons, Zdeněk; Kroha, Václav; La Cognata, M.; Mrázek, Jaromír

    Les Ulis: E D P Sciences, 2014, 07008. ISBN 978-2-7598-1176-2. ISSN 2100-014X. [International Nuclear Physics Conference (INPC 2013). Firenze (IT), 02.06.2013-07.06.2013] R&D Projects: GA MŠk(CZ) LH11001; GA ČR GAP203/10/0310 Institutional support: RVO:61389005 Keywords : cross-section * elements * C-14 Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  16. 40 CFR 721.642 - Amines, N-(C14-18 and C16-16 unsaturated alkyl)] dipropylene-tri-, tripropylenetetra-, and...

    Science.gov (United States)

    2010-07-01

    ... unsaturated alkyl)] dipropylene-tri-, tripropylenetetra-, and tetrapropylenepenta-. 721.642 Section 721.642... Amines, N-(C14-18 and C16-16 unsaturated alkyl)] dipropylene-tri-, tripropylenetetra-, and... substances amines, N-(C14-18 and C16-18 unsaturated alkyl)] dipropylenetri-, (PMN...

  17. Release and transport of gaseous C-14 from a nuclear waste repository in an unsaturated medium

    International Nuclear Information System (INIS)

    The potential nuclear waste repository at Yucca Mountain is to be in partially saturated rock. Released radioactive gases such as 14CO2 could have a direct pathway to the biosphere. We study the release of 14C released as 14CO2 from partly failed nuclear waste containers by analyzing the flow of gas into and out of a container. We analyze the transport of released 14CO2 in an unsaturated, fractured, porous medium with gas-phase advection and dispersion. We calculate the inhalation dose to a maximally exposed individual above ground, based on some conservative assumptions about release from containers. For the assumed parameter values, a simple atmospheric diffusion model gives very small doses when compared to background radiation doses. 12 refs., 4 figs., 1 tab

  18. Identification of Site of Morphine Action in Pregnant Wistar Rat Placenta Tissue: A C14-Morphine Study

    Directory of Open Access Journals (Sweden)

    Leila Dehghani

    2012-01-01

    Full Text Available Objective: In previous studies it has been emphasized that the site of morphine action may be either in the embryo or the placenta. In the present study, we attempt to identify the site of morphine action on the fetal section of Wistar rat placenta by using C14-morphine.Materials and Methods: In this study (experimental, female Wistar rats (weights: 170-200 g were mated with male rats and their coupling times recorded. Experimental groups received daily doses of 0.05 mg/ml of C14-morphine in their drinking water. On the 9th and14th embryonic days, the pregnant rats were anesthetized and the placenta and uterus surgically removed. Placentas were fixed in 10% formalin for two weeks, then processed, sectioned in 5 μm and 25 μm thicknesses, and fixed on glass slides for further evaluation. The 25 μm sections were delivered to black and white film for three days. Films were processed and evaluated with a digital inverse microscope for possible radiological impression. The 5 μm sections were processed for hematoxylin and eosin (H&E staining, and evaluated by light microscope and MOTIC software.Results: Our results indicated that the site of action of C14-morphine was possibly located on the blood plexus of the fetal portion of the placenta. In addition, oral morphine consumption was shown to inhibit fetal and maternal placental development in the experimental groups.Conclusion: We conclude that morphine’s effectiveness on the reduction of embryo growth and development may be via its effects on the blood plexus of the fetal section of the placenta.

  19. Laves相和Z相对P92钢蠕变的影响%INFLUENCE OF LAVES- PHASE AND Z- PHASE UPON CREEP OF P92 STEEL

    Institute of Scientific and Technical Information of China (English)

    姜运建; 张文建; 李文彬

    2009-01-01

    综合国内外的研究成果,论述了Laves相和Z相对提高P92钢蠕变性能的影响.结果表明,Laves相形成初期对提高P92钢蠕变断裂强度有利,但当Laves相达到一定尺寸后对提高蠕变断裂强度不利;Z相析出不但增加了蠕变孔洞出现的几率,而且会造成MX相在基体中的减少,降低MX弥散强化的作用,Z相的析出对P92钢蠕变断裂有不良影响.

  20. Design, Synthesis and Biological Evaluation of Novel C14-C3’BzN–Linked Macrocyclic Taxoids¶

    OpenAIRE

    Sun, Liang; Geng, Xudong; Geney, Raphaël; Li, Yuan; Li, Zhong; Lauher, Joseph W.; Xia, Shujun; Horwitz, Susan B.; Veith, Jean M.; Pera, Paula; Bernacki, Ralph J.; Ojima, Iwao

    2008-01-01

    Novel macrocyclic paclitaxel congeners were designed to mimic the bioactive conformation of paclitaxel. Computational analysis of the “REDOR-Taxol” structure revealed that this structure could be rigidified by connecting the C14 position of the baccatin moiety and the ortho position of C3’N-benzoyl group (C3’BzN), which are ca. 7.5 Å apart, with a short linker (4−6 atoms). 7-TES-14β-allyloxybaccatin III and (3R,4S)-1-(2-alkenylbenzoyl)-β-lactams were selected as key components and the Ojima-H...

  1. Synthesis and characterization of C14TAB passivated cerium oxide nanoparticles prepared by co-precipitation route

    Science.gov (United States)

    Krishna Chandar, N.; Jayavel, R.

    2014-04-01

    A facile co-precipitation route has been employed to synthesize cerium oxide (CeO2) nanoparticles using cationic surfactant (tetradecyltrimethyl ammonium bromide, C14TAB) and cerium nitrate hexahydrate at room temperature. X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscope (TEM), selected area electron diffraction (SAED), fourier transform infrared spectroscopy (FT-IR), UV-vis spectrophotometer and photoluminescence spectroscopy (PL) were employed to characterize the as-prepared sample. The XRD pattern showed cubic fluorite structure of CeO2 without any impurity peaks, revealing high purity of the sample. The lattice strain experienced by the sample was analyzed using Williamson-Hall plot. FTIR studies confirmed the presence of C14TAB on the CeO2 nanoparticles. TEM revealed that the as-prepared CeO2 sample consists of uniform particles with particle size of 10 nm. The red shift phenomenon was observed in UV-vis spectrum, which was further supported by PL studies.

  2. Effect of Deleterious Phases on Corrosion Resistance of Duplex Stainless Steel (2205)

    OpenAIRE

    AbdulKadar M. Godil; Hitesh A. Narsia; M. N. Patel; Mr. Paresh U. Haribhakti

    2013-01-01

    Duplex stainless steel is a Ferritic(BCC)-Austenitic(FCC) steel, covers the advantages of both Austenitic and Ferritic Stainless steels. They having good mechanical and corrosion resistance properties are widely used in many industries like chemical plants, refineries for critical equipments such as pressure vessels, heatexchangers, water heaters. Major problem occurs with duplex steels when they are worked or heated above about temperature of 280°C. Detrimental phases like Sigma, Chi, Laves ...

  3. C10~C14烷基糖苷的合成及其作为乳化剂的应用%Synthesis of C10-C14 alkyl polyglycoside and their application as emulsifiers

    Institute of Scientific and Technical Information of China (English)

    陈馥; 庞敏; 吴柯颖; 杨媚

    2015-01-01

    采用直接法合成了碳链长度为 C10~C14的烷基糖苷(APG),用红外光谱对产品结构进行了表征,研究了烷基糖苷浓度及碳链长度对产品表、界面性质的影响。结果表明:随烷基糖苷浓度增大,水溶液表面张力、柴油-水界面张力降逐渐降低,而起泡性、泡沫稳定性逐渐增强。烷基糖苷碳链越长,临界胶束浓度(cmc)值越低;水溶液表面张力、柴油-水界面张力越低,起泡性、泡沫稳定性越强。基于烷基糖苷良好的表、界面性质,将其作为乳化剂制备成乳液,并与常见非离子表面活性剂 OP-10制备的乳液进行了对比。烷基糖苷乳化性随浓度增大、碳链长度增长而增强;乳液微观形态表明不同碳链烷基糖苷形成乳状液稳定性、液滴均一性、填充性均优于 OP-10稳定的乳液;稳定时间对乳液微观形态影响不大。所合成烷基糖苷中性能最优的为 C14APG。%Alkyl polyglycosides (APGs) with different carbon chains from C10 to C14 were synthesized and characterized with infrared spectroscopy. The influence of APG concentration and carbon chain length on the surface and interfacial properties were both studied. The results showed that the surface tension and diesel-water interfacial tension were gradually decreased with increasing the concentration of APG,while the capacity of foaming,foam stabiling and emulsifying were enhanced. On the other hand,with increasing carbon chain length,the critical micelle concentration (cmc) value of APG, surface tension,and diesel-water interfacial tension were decreased,while the capacity of foaming, foam stabiling and emulsifying were enhanced on the contrary. Because of their good surface and interfacial properties,APGs were applied to prepare emulsion as emulsifier. This work showed that the capacity of emulsifying was enhanced with increasing APGs concentration and carbon chain length. Furthermore,the micromorphology

  4. The age of olfactory bulb neurons in humans: an application of dating microgram DNA samples with the C14 bomb peak

    International Nuclear Information System (INIS)

    Full text: The determination of C14 levels in genomic DNA can be used to retrospectively establish the birth date of cells in the human body which was pioneered at the Karolinska Institute. Aboveground nuclear weapons testing between 1950 and 1963 doubled the atmospheric C14 content. After the Partial Nuclear Test Ban Treaty in 1963 the excess C14 decreased again by exchange of carbon dioxide between atmosphere, biosphere and the ocean. As a consequence all humans who lived in the second half of the 20th century have been labelled with this rapidly changing excess C14. During the last years the amount of carbon required for a C14 Accelerator Mass Spectrometry (AMS) measurement at the VERA Laboratory in Vienna was reduced to such an extent (mg to μg) that investigations of neurons of particularly interesting small sections of the human brain became possible. C14 measurements of < 5μg carbon DNA samples with an overall precision of 2.0 to 2.5% were achieved. This allowed to study neurogenesis in the human olfactory bulb, which turned out to take place primarily at birth with <1% of these neurons being exchanged at a later time. This identifies a fundamental difference in the plasticity of the human brain compared to other mammals. (author)

  5. Observation and analysis of incomplete fusion reactions induced by (12C, 14N, 16O, 22Ne) ions

    International Nuclear Information System (INIS)

    The mechanism of the reactions induced by heavy ions has been studied. The experiments were concerned with incident channels which lead to the formation of intermediate nuclei with atomic mass (6412C, 14N, 16O, 22Ne) as projectiles respectively. The detection of light fragments (2< Z<12) is studied. A three solid-state-detector telescope, with associated electronics is used which allows the separation of reaction products according to their charge. The main features of deep inelastic collisions are discussed: large kinetic energy loss, and important nucleon transfer as a function of the angular detection. The time evolution of the reaction has been studied, then the results are compared with a scattering model suggested by Noremberg. A theoretical calculation based on both classical and statistical approaches giving the total cross-sections for any exit channel has been proposed

  6. TL, OSL and C-14 dating results of the sediments and bricks from mummified nuns' grave

    Energy Technology Data Exchange (ETDEWEB)

    Tudela, Diego R.G.; Tatumi, Sonia H.; Yee, Marcio; Brito, Silvio L.M., E-mail: tatumi@fatecsp.br [Faculdades de Tecnologia de Sao Paulo (FATECs/CEETEPS/UNESP), Sao Paulo, SP (Brazil). Centro Estadual de Educacao Tecnologica Paula Souza; Morais, Jose L.; Morais, Daisy de; Piedade, Silvia C. [Universidade de Sao Paulo (USP), SP (Brazil). Museu de Arqueologia e Etnologia; Munita, Casimiro S.P.; Hazenfratz, Roberto [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2012-06-15

    This paper presents the results of TL and OSL dating of soil and fragments of bricks from a grave, which was occupied by two mummified nuns, found at 'Luz' Monastery, located in the state of Sao Paulo, Brazil. The TL and OSL ages were compared to C-14 dating ones obtained from bone collagens of the mummies. The majority of the ages is related to the eighteenth century. The gamma-ray spectroscopy was used to evaluate natural radioisotope concentrations in the samples, and by using these concentrations the annual dose rates, from 3.0 to 5.3 Gy/kyr, were obtained. Neutron activation analysis was performed and the radioisotope contents results are in agreement with those obtained by gamma-ray spectroscopy. The contents of U, Th and Ce elements were higher than those found in usual sediments. (author)

  7. Analysis of LMD data of core coming from Ta(15C, 14C+n)Ta Coulomb breakup reaction

    International Nuclear Information System (INIS)

    It is well established fact that the neutron-halo nucleus is a loosely bound exotic nuclear state where in the valence neutron is found mostly at a much larger distance from the remaining core. The development of radioactive ion beams (RI) has provided a great opportunity to explore various peculiar properties of such nuclear systems. Consequently lots of efforts have been made on theoretical and experimental fronts to understand the exotic features of halo nuclei. One of the clear manifestations of exotic properties of isotopes lying near neutron drip line is the loss of magicity and the tendency to posses prolate deformation. In this conference contribution, we study Ta(15C, 14C+n)Ta Coulomb breakup reaction with a special emphasis on the study of effects of deformation and to investigate the possibility of occupying d-orbital by valence neutron in 15 C

  8. Accelerated molecular evolution of insect orthologues of ERG28/C14orf1: a link with ecdysteroid metabolism?

    Indian Academy of Sciences (India)

    Reiner A. Veitia; Laurence D. Hurst

    2001-04-01

    We have analysed the evolution of ERG28/C14orf1, a gene coding for a protein involved in sterol biosynthesis. While primary sequence of the protein is well conserved in all organisms able to synthesize sterols de novo, strong divergence is noticed in insects, which are cholesterol auxotrophs. In spite of this virtual acceleration, our analysis suggests that the insect orthologues are evolving today at rates similar to those of the remaining members of the family. A plausible way to explain this acceleration and subsequent stabilization is that Erg28 plays a role in at least two different pathways. Discontinuation of the cholesterogenesis pathway in insects allowed the protein to evolve as much as the function in the other pathway was not compromised.

  9. Comparison of the Quantitative Values of C-14 and C-13 UBT to Reflect the Presence and Degree of Ongoing Helicobacter pylori Infection

    International Nuclear Information System (INIS)

    A urea breath test (UBT) using C-14 or C-13 has been developed for identifying Helicobacter (H) pylori infection on the basis of urease production with release of labeled CO2. We investigated if the C-14 and C-13 UBT have the difference to reflect the presence and degree of H. pylori infection detected by gastroduodenoscopic biopsies (GBx) in the same patients. Thirty eight patients (M:F=28:10, age 53.4±13.0 yrs) with upper gastrointestinal symptoms such as indigestion, gastric fullness or pain consecutively underwent C-14 UBT, GBx and C-13 UBT within one week before medications. For the C-14 UBT, a single breath sample was collected at 10 minutes after ingestion of C-14 urea (37 KBq) capsule and counting was done in a liquid scintillation counter for 1 minute, and the results were classified as positive (≥200 dpm), intermediate (50∼199 dpm) or negative (<50 dpm). For the C-13 UBT, the results were classified as positive (≥2.5) or negative (<2.5). The results of GBx with Giemsa stain were graded 0 (normal) to 4 (diffuse) according to the distribution of H. pylori by the Wyatt method. We compared C-14 UBT and C-13 UBT results with GBx grade as a gold standard. The prevalence of H. pylori infection by GBx with Giemsa stain was 25/38 (65.8%). In the assessment of the presence of H. pylori infection, the C-14 UBT global performance yielded sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of 92.0%, 92.3%, 95.8%, 91.7% and 92.1%, respectively. However, the C-13 UBT had sensitivity, specificity, PPV, NPV and accuracy of 96.0%, 84.6%, 92.3%, 91.7% and 92.1%, respectively. The more significant correlation in C-14 than C-13 UBT (r=0.948 vs r=0.819, p<0.001) was found between the value of UBT and the grade of distribution of H. pylori infection. We conclude that the diagnostic performance between C-14 and C-13 UBT to detect H. pylori infection is not significantly different, but the value of C-14 UBT more

  10. Comparison of the Quantitative Values of C-14 and C-13 UBT to Reflect the Presence and Degree of Ongoing Helicobacter pylori Infection

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Seok Tae; Kim, Dong Wook; Jeong, Hwan Jeong; Sohn, Myung Hee [Chonbuk National University Medical School, Jeonju (Korea, Republic of)

    2008-06-15

    A urea breath test (UBT) using C-14 or C-13 has been developed for identifying Helicobacter (H) pylori infection on the basis of urease production with release of labeled CO{sub 2}. We investigated if the C-14 and C-13 UBT have the difference to reflect the presence and degree of H. pylori infection detected by gastroduodenoscopic biopsies (GBx) in the same patients. Thirty eight patients (M:F=28:10, age 53.4{+-}13.0 yrs) with upper gastrointestinal symptoms such as indigestion, gastric fullness or pain consecutively underwent C-14 UBT, GBx and C-13 UBT within one week before medications. For the C-14 UBT, a single breath sample was collected at 10 minutes after ingestion of C-14 urea (37 KBq) capsule and counting was done in a liquid scintillation counter for 1 minute, and the results were classified as positive ({>=}200 dpm), intermediate (50{approx}199 dpm) or negative (<50 dpm). For the C-13 UBT, the results were classified as positive ({>=}2.5) or negative (<2.5). The results of GBx with Giemsa stain were graded 0 (normal) to 4 (diffuse) according to the distribution of H. pylori by the Wyatt method. We compared C-14 UBT and C-13 UBT results with GBx grade as a gold standard. The prevalence of H. pylori infection by GBx with Giemsa stain was 25/38 (65.8%). In the assessment of the presence of H. pylori infection, the C-14 UBT global performance yielded sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of 92.0%, 92.3%, 95.8%, 91.7% and 92.1%, respectively. However, the C-13 UBT had sensitivity, specificity, PPV, NPV and accuracy of 96.0%, 84.6%, 92.3%, 91.7% and 92.1%, respectively. The more significant correlation in C-14 than C-13 UBT (r=0.948 vs r=0.819, p<0.001) was found between the value of UBT and the grade of distribution of H. pylori infection. We conclude that the diagnostic performance between C-14 and C-13 UBT to detect H. pylori infection is not significantly different, but the value of C-14 UBT

  11. Efficiency of vanilla, patchouli and ylang ylang essential oils stabilized by iron oxide@C14 nanostructures against bacterial adherence and biofilms formed by Staphylococcus aureus and Klebsiella pneumoniae clinical strains.

    Science.gov (United States)

    Bilcu, Maxim; Grumezescu, Alexandru Mihai; Oprea, Alexandra Elena; Popescu, Roxana Cristina; Mogoșanu, George Dan; Hristu, Radu; Stanciu, George A; Mihailescu, Dan Florin; Lazar, Veronica; Bezirtzoglou, Eugenia; Chifiriuc, Mariana Carmen

    2014-01-01

    Biofilms formed by bacterial cells are associated with drastically enhanced resistance against most antimicrobial agents, contributing to the persistence and chronicization of the microbial infections and to therapy failure. The purpose of this study was to combine the unique properties of magnetic nanoparticles with the antimicrobial activity of three essential oils to obtain novel nanobiosystems that could be used as coatings for catheter pieces with an improved resistance to Staphylococcus aureus and Klebsiella pneumoniae clinical strains adherence and biofilm development. The essential oils of ylang ylang, patchouli and vanilla were stabilized by the interaction with iron oxide@C14 nanoparticles to be further used as coating agents for medical surfaces. Iron oxide@C14 was prepared by co-precipitation of Fe+2 and Fe+3 and myristic acid (C14) in basic medium. Vanilla essential oil loaded nanoparticles pelliculised on the catheter samples surface strongly inhibited both the initial adherence of S. aureus cells (quantified at 24 h) and the development of the mature biofilm quantified at 48 h. Patchouli and ylang-ylang essential oils inhibited mostly the initial adherence phase of S. aureus biofilm development. In the case of K. pneumoniae, all tested nanosystems exhibited similar efficiency, being active mostly against the adherence K. pneumoniae cells to the tested catheter specimens. The new nanobiosystems based on vanilla, patchouli and ylang-ylang essential oils could be of a great interest for the biomedical field, opening new directions for the design of film-coated surfaces with anti-adherence and anti-biofilm properties. PMID:25375335

  12. Efficiency of Vanilla, Patchouli and Ylang Ylang Essential Oils Stabilized by Iron Oxide@C14 Nanostructures against Bacterial Adherence and Biofilms Formed by Staphylococcus aureus and Klebsiella pneumoniae Clinical Strains

    Directory of Open Access Journals (Sweden)

    Maxim Bilcu

    2014-11-01

    Full Text Available Biofilms formed by bacterial cells are associated with drastically enhanced resistance against most antimicrobial agents, contributing to the persistence and chronicization of the microbial infections and to therapy failure. The purpose of this study was to combine the unique properties of magnetic nanoparticles with the antimicrobial activity of three essential oils to obtain novel nanobiosystems that could be used as coatings for catheter pieces with an improved resistance to Staphylococcus aureus and Klebsiella pneumoniae clinical strains adherence and biofilm development. The essential oils of ylang ylang, patchouli and vanilla were stabilized by the interaction with iron oxide@C14 nanoparticles to be further used as coating agents for medical surfaces. Iron oxide@C14 was prepared by co-precipitation of Fe+2 and Fe+3 and myristic acid (C14 in basic medium. Vanilla essential oil loaded nanoparticles pelliculised on the catheter samples surface strongly inhibited both the initial adherence of S. aureus cells (quantified at 24 h and the development of the mature biofilm quantified at 48 h. Patchouli and ylang-ylang essential oils inhibited mostly the initial adherence phase of S. aureus biofilm development. In the case of K. pneumoniae, all tested nanosystems exhibited similar efficiency, being active mostly against the adherence K. pneumoniae cells to the tested catheter specimens. The new nanobiosystems based on vanilla, patchouli and ylang-ylang essential oils could be of a great interest for the biomedical field, opening new directions for the design of film-coated surfaces with anti-adherence and anti-biofilm properties.

  13. MEF2 and NR2F2 cooperate to regulate Akr1c14 gene expression in mouse MA-10 Leydig cells.

    Science.gov (United States)

    Di-Luoffo, M; Brousseau, C; Tremblay, J J

    2016-03-01

    Leydig cells are essential for male reproductive development and health throughout life. Production of androgens [testosterone, dihydrotestosterone (DHT)] as well as intermediate steroids [progesterone, dihydroprogesterone (DHP)] is tightly regulated. In the mouse, the 3α-hydroxysteroid dehydrogenase enzyme (3α-HSD, AKR1C14) catalyses the interconversion of DHP and DHT into less potent steroids. Despite its importance, nothing is currently known regarding the regulation of Akr1c14 expression in Leydig cells. Recently, the transcription factors MEF2 and NR2F2 were identified in the mouse testis including in Leydig cells where they were found to regulate expression of genes involved in steroidogenesis. Analyses of transcriptomic data from MEF2- or NR2F2-deficient MA-10 Leydig cells revealed a significant decrease in Akr1c14 mRNA levels. Using qPCR, we confirmed that Akr1c14 mRNA levels were decreased in MEF2- and in NR2F2-deficient conditions. Conversely, overexpression of MEF2A or/and NR2F2 in MA-10 Leydig cells led to an increase in endogenous Akr1c14 mRNA levels. Recruitment of MEF2 and NR2F2 to the Akr1c14 promoter was confirmed by ChIP while DNA precipitation assays revealed direct binding of MEF2 but not NR2F2 to this region. In functional promoter studies, NR2F2 was found to activate the Akr1c14 promoter while MEF2A on its own had no effect. Combination of both NR2F2 and MEF2A led to a cooperative activation of the Akr1c14 promoter and this required intact MEF2 and NR2F2 elements. Finally, co-immunoprecipitation experiments showed that MEF2 and NR2F2 are present in the same protein complex. In conclusion, our results identify a novel cooperation between MEF2 factors and NR2F2 in the expression of the Akr1c14 gene involved in the regulation of DHP/DHT levels. PMID:26748576

  14. Ti12.5Zr21V10Cr8.5MnxCo1.5Ni46.5-x AB2-type metal hydride alloys for electrochemical storage application: Part 1. Structural characteristics

    Science.gov (United States)

    Bendersky, L. A.; Wang, K.; Levin, I.; Newbury, D.; Young, K.; Chao, B.; Creuziger, A.

    2012-11-01

    The microstructures of a series of AB2-based metal hydride alloys (Ti12.5Zr21V10Cr8.5MnxCo1.5Ni46.5-x) designed to have different fractions of non-Laves secondary phases were studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectrometry, and electron backscatter diffraction. The results indicate that the alloys contain a majority of hydrogen storage Laves phases and a minority of fine-structured non-Laves phases. Formation of the phases is accomplished by dendritic growth of a hexagonal C14 Laves phase. The C14 phase is followed by either a peritectic solidification of a cubic C15 Laves phase (low Mn containing alloys) or a C14 phase of different composition (high Mn containing alloys), and finally a B2 phase formed in the interdendritic regions (IDR). The interdendritic regions may then undergo further solid-state transformation into Zr7Ni10-type, Zr9Ni11-type and TiNi-type phases. As the Mn content in the alloy increases, the fraction of the C14 phase increases, whereas the fraction of C15 decreases. In the IDRs when the alloy's Mn content increases the Zr9Ni11 phases and Zr7Ni10 phase fraction first increases and then decreases, while the TiNi-based phase fraction first increases and then stabilized at 0.02. IDR compositions can be generally expressed as (Ti,Zr,V,Cr,Mn,Co)50Ni50, which accounted for 7-10% of the overall alloy volume fraction.

  15. Estimation of cancerolytic properties of thionine from plants seeds by inclusion of C14-thymidine in tumoral cells

    International Nuclear Information System (INIS)

    Full text: It has been earlier shown that cysteine rich peptides - thionine from seeds of various plants possess expressed fungitoxic activity. It is connected to influence of thionine on cellular membranes of fungi. It was possible to assume that the substances showing cytotoxic activity will be active in relation to tumoral cells. We isolated peptide fractions from seeds bamia (Hibiscus esculentus), kenaf (Hibiscus cannabinus), abutilon (Abutilon theophrasti), euphorbia (Euphorbia virgata), palma Christi (Ricinus communis) and horse sorrel (Rumex confertus) and studied their antineoplastic and fungitoxic activity. Antiproliferative action of peptides to melanoma cells of mice was estimated in cytotoxic test by inclusion of C14-thymidine to DNA. This researches have shown that peptides from seeds of horse sorrel and palma Christi did not change a level of synthesis of DNA while peptides from euphorbia and bamia considerably reduced inclusion of labeled nucleotide to DNA and suppressed growth of tumoral cells on 14 and 39 % accordingly. Parallel tests of these peptides on fungitoxic activity in relation to virulent strains of Verticillium dahliae have shown suppression of conidial growth on 17 and 26 % accordingly. Thus, peptides from seeds of bamia and euphorbia possess the expressed property to suppress growth of tumoral cells and can be used at creation a new cancerolytic preparations for treatment of human cancer. Work is executed under the financial support of fundamental grants F - 4.19 and F-4.1.44

  16. Estimation of deposition velocities of HT and 14CO2 and their fluxes from surface environment with a development of a simultaneous sampling system for the speciation of atmospheric H-3 and C-14

    International Nuclear Information System (INIS)

    Concerning atmospherically released tritium (T) and C-14 we have developed a new method, which can analyze their fluxes and the deposition velocities. Firstly, a simultaneous sampling system for the speciation of atmospheric tritium and C-14 has been developed. This system determines varieties of chemical forms of tritium and C-14, namely tritiated water (HTO), elemental tritium gas (HT) and tritiated methane (CH3T) for tritium, 14CO2 and 14C H4 for C-14, respectively. Secondly, a new method was developed to determine HT and 14CO2 deposition velocities. This method can determine their fluxes and the deposition velocities without any tritium and C-14 sources. (author)

  17. A transport and fate model of C-14 in a bay of the Baltic Sea at SFR. Today and in future

    International Nuclear Information System (INIS)

    The environmental transport and fate of a hypothetical release of radioactive carbon-14 from SFR-1 (the final repository for radioactive operational waste) was investigated using an ecosystem modelling approach. The approach involved identification, quantification and dynamic modelling of the main flows and storages of carbon both in the physical environment and in the food web. Carbon-14 was in the model introduced into the food web via photosynthesising organisms. Contamination of the aquatic ecosystem above SFR-1 was then assessed assuming a release of 5.13 x 107 Bq/year for 1,000 years. Modelling results were used to estimate steady-state C-14 concentrations in biota, exposure (Gy) of biota and dose (Sv) to humans consuming contaminated organisms both if the discharge occurred today (2000 AD)and if it occurred in the future (4000 AD). Since the modelled area is characterised by a fast water exchange, most of the discharged C-14 was flushed out of the system more or less immediately (99.8% and 98.4% at 2000 AD and 4000 AD, respectively). However, a small fraction of the discharge was assimilated by primary producers (0.18% and 2.11%), which enabled subsequent transfer of C-14 to organisms at higher trophic levels (e.g. fish, seals and humans). The exported C-14 from the area was diluted to very low concentrations in the large recipient outside. Estimated exposures were very low, and differed significantly among the studied biota (17.2 x 10-12 to 2.3 x 10-6 Gy). In general the highest exposures were observed in benthic plants and benthic grazers followed by fish and benthos. Humans consuming large quantities of locally produced food (e.g.fish, mussels and algae) will receive an exposure in case of C-14 contamination. Estimated doses to humans were approximately 10-100 nSv per year, which is significantly lower than restrictions by the authorities. The developed model was also used to evaluate implications of various assumptions concerning the route of C-14 entry

  18. A transport and fate model of C-14 in a bay of the Baltic Sea at SFR. Today and in future

    Energy Technology Data Exchange (ETDEWEB)

    Kumblad, L. [Stockholm Univ. (Sweden). Dept. of Systems Ecology

    2001-06-01

    The environmental transport and fate of a hypothetical release of radioactive carbon-14 from SFR-1 (the final repository for radioactive operational waste) was investigated using an ecosystem modelling approach. The approach involved identification, quantification and dynamic modelling of the main flows and storages of carbon both in the physical environment and in the food web. Carbon-14 was in the model introduced into the food web via photosynthesising organisms. Contamination of the aquatic ecosystem above SFR-1 was then assessed assuming a release of 5.13 x 10{sup 7} Bq/year for 1,000 years. Modelling results were used to estimate steady-state C-14 concentrations in biota, exposure (Gy) of biota and dose (Sv) to humans consuming contaminated organisms both if the discharge occurred today (2000 AD)and if it occurred in the future (4000 AD). Since the modelled area is characterised by a fast water exchange, most of the discharged C-14 was flushed out of the system more or less immediately (99.8% and 98.4% at 2000 AD and 4000 AD, respectively). However, a small fraction of the discharge was assimilated by primary producers (0.18% and 2.11%), which enabled subsequent transfer of C-14 to organisms at higher trophic levels (e.g. fish, seals and humans). The exported C-14 from the area was diluted to very low concentrations in the large recipient outside. Estimated exposures were very low, and differed significantly among the studied biota (17.2 x 10{sup -12} to 2.3 x 10{sup -6} Gy). In general the highest exposures were observed in benthic plants and benthic grazers followed by fish and benthos. Humans consuming large quantities of locally produced food (e.g.fish, mussels and algae) will receive an exposure in case of C-14 contamination. Estimated doses to humans were approximately 10-100 nSv per year, which is significantly lower than restrictions by the authorities. The developed model was also used to evaluate implications of various assumptions concerning the

  19. Thermodynamic parameters of hydrogen solution in the Laves phase Ti(Cr,Mn)1.78 at high temperature and low pressure

    International Nuclear Information System (INIS)

    Hydrogen absorption has been studied in two compounds of the series TiCr1.78-xMnx at high temperature and low H contents nH (nH = H/Me < 0.035). From the Sieverts law, which has been found to hold, the partial standard molar enthalpy and entropy have been derived. It has been found that substitution of Mn for Cr leads to a decrease in the atomic volume and in parallel to an increase in the partial molar enthalpy of the H solution

  20. A time dependent kinetic small angle neutron scattering study of a novel YFe phase

    International Nuclear Information System (INIS)

    Crystallization of amorphous Y67Fe33 into the YFe2 C15 Laves phase via a novel ‘YFe’ intermediate phase has been observed through to completion using time-resolved small angle neutron scattering (SANS). The nucleation and growth kinetics of the phase transformations have been studied at annealing temperatures below the crystallization temperatures for both the ‘YFe’ phase and the YFe2 phase. The SANS results agree with previously reported neutron diffraction and SANS data. At the annealing temperatures of 360, 370 and 380 ° C, changes in the scattering intensity I(Q) occur as a result of the contrast between the amorphous matrix and the nucleating and growing Y and ‘YFe’ phases. Critical scattering occurs during each of the isotherms, relating to the full crystallization of Y67Fe33, and extrapolation gives a crystallization temperature of 382 ° C. Beyond critical scattering, isotherms at 435, 450, and 465 ° C reveal the details of the continuing transformation of the ‘YFe’ intermediate phase into the YFe2 C15 Laves phase. (paper)

  1. Thermodynamic and structural study of the Zr-Ni-Cr ternary system (Zr<50 at%) and of its equilibria with hydrogen: electrochemical application; Etude thermodynamique et structurale du systeme ternaire Zr-Ni-Cr (Zr<50at%) et de ses equilibres avec l`hydrogene: application electrochimique

    Energy Technology Data Exchange (ETDEWEB)

    Joubert, J.M.

    1995-07-12

    In the frame of the research on intermetallic compounds for nickel-hydride battery application, attention is focused on AB{sub 2} alloys so called Laves phases. ZrCr{sub 2}, for example, exhibits a large hydrogen capacity but a too low hydride formation equilibrium pressure for practical application. Moreover, the electrolyte (concentrated potassium hydroxide) involves surface passivation through blocking electrochemical mechanisms. First, the study is devoted to the adjustment of the hydride thermodynamic properties regarded to electrochemical application. This was achieved on ZrCr{sub 2} by substitution of chromium by nickel. In a second part surface properties are modified by the precipitation of secondary phases in equilibrium with the Laves phase. The Zr-Ni-Cr phase diagram has been determined at 1000 deg C in the ZrCr{sub 2}-ZrNi-Ni-Cr region and has revealed large solubility of nickel in C14 and C15 Laves phases as well as equilibrium of these phases with three Zr-Ni intermetallic compounds. The knowledge of this diagram has allowed the synthesis of biphasic alloys where the Laves phase of constant composition is in equilibrium with a secondary phase at variable rate. The study of hydrogenation properties of Laves phases has shown the possibility of adjusting the equilibrium pressure of its hydrides to electrochemical application keeping high hydrogen capacity. The hydrogenation properties of secondary phases were also characterized. Finally, it appeared that secondary phases precipitation with increasing rate in the Laves phase matrix produces a spectacular increase of electrochemical capacities. Such an effect of hydrogen by the modification of the surface in contact with electrolyte and by the diffusion of hydrogen from electrolyte to the Laves through the secondary phase when present. (author)

  2. Initial study on Z-phase strengthened 9-12% Cr steels by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fang; Andren, Hans-Olof [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Applied Physics

    2010-07-01

    The microstructure of two different types of Z-phase strengthened experimental steels, CrNbN-based or CrTaN-based, was investigated. Both steels underwent aging at 650 C for relatively short period of time, 24 hours or 1005 hours. Atom probe tomography was used to study the chemical composition of the matrix and precipitates, and the size and number density of the small precipitates. Both steels contain Laves phase at prior austenite grain boundaries and martensitic lath boundaries. The CrTaN-based steel was found more promising due to its finer and more densely distributed precipitates after 1005 hour aging. (orig.)

  3. Genes encoding chimeras of Neurospora crassa erg-3 and human TM7SF2 proteins fail to complement Neurospora and yeast sterol C-14 reductase mutants

    Indian Academy of Sciences (India)

    A Prakash; Durgadas P Kasbekar

    2002-03-01

    The human gene TM7SF2 encodes a polypeptide (SR-1) with high sequence similarity to sterol C-14 reductase, a key sterol biosynthetic enzyme in fungi, plants and mammals. In Neurospora and yeast this enzyme is encoded by the erg-3 and erg24 genes respectively. In an effort to demonstrate sterol C-14 reductase activity for SR-1 we constructed six recombinant genes coding for chimeras of the Neurospora erg-3 and SR-1 protein sequences and tested them for complementation of the Neurospora erg-3 mutant. To our surprise, all the chimeras failed to complement erg-3. A few of the chimeric proteins were also tested against the yeast erg24 mutant, but again there was no complementation. We discuss some reasons that might account for these unexpected findings.

  4. Energy loss effect on color center creation in LiF crystals under irradiation with 12C, 14N, 40Ar, 84Kr, and 130Xe ions

    International Nuclear Information System (INIS)

    Color center creation in LiF crystals irradiated with 12C, 14N, 40Ar, 84Kr, and 130Xe MeV ions were studied as a function of the absorbed energy (fluence). For light ions (12C, 14N) the saturation of single F centers takes place at higher absorbed energy (5 × 1023 eV/cm3) than that for 40Ar, 84Kr and 130Xe ions (∼1023 eV/cm3). The saturation concentration of F centers for 12C and 14N (2 × 1019 cm−3) is twice of that for the heavier ions. Further irradiation with light ions decreases concentration of F centers, presumably due to aggregation, whereas for heavy ions the saturation concentration remains approximately the same that can be explained by much stronger recombination losses within single tracks

  5. Experimental-study of the interactions between a natural C-14 radiolabeled sediment and a deposit-feeding bivalve : Abra alba

    OpenAIRE

    Amouroux, JM; Gremare, A.; Cahet, G

    1991-01-01

    Changes of radioactivity in a natural C-14 labelled sediment were monitored over a 120-hour period in the presence and in the absence of the deposit-feeding bivalve Abra alba. In both cases, the sediment showed great instability during the first ten hours of the experiment. The consequences of this result on the experimental protocol used for the study of the interactions between natural sediments and deposit-feeders are discussed. In controls, the instability is produced by an initial decrea...

  6. Status quo of the storage of C-14 containing waste from German high-temperature and research reactors and the strategy for their future storage

    International Nuclear Information System (INIS)

    The German research reactors and the high-temperature reactors (AVR, THTR 300) used graphite as reflector and/or moderator materials. Due to the activation of these materials there exists a significant amount of C-14, H-3 and Co-60.The project included the assessment of the respective amount of materials from all facilities, the legal framework for interim storage, transport and final disposal.

  7. Gas phase migration of C-14 through barrier materials applicable for use in a high-level nuclear waste repository located in tuff

    International Nuclear Information System (INIS)

    A study of the movement of 14CO2 through proposed barrier media has been conducted. Diffusion coefficients for crushed tuff, bentonite and a 90:10% by wt. mixture of crushed tuff and bentonite were measured for two diffusion lengths. The ability of 14CO2 to penetrate a microsilica-containing portland cement mortar proposed for repository use was also examined. The specimens were subjected to uniaxially-applied compressive loads prior to the diffusion tests to simulate the onset of environmentally-induced microcracks. 91 refs., 14 figs., 15 tabs

  8. Radiation-induced phase development in AISI 316

    International Nuclear Information System (INIS)

    During irradiation at temperatures between 460 and 6500C, the alloy AISI 316 decomposes into an austenite matrix of altered composition and some mixture of six possible precipitate phases. These phases are γ', G, eta-silicide, M23C6, M6C, and Laves. The balance of phases developed is exceptionally sensitive to a large number of material and environmental variables and frequently varies within a single grain. All of these phases are found to be either naturally rich in nickel and silicon or to become progressively enriched in these elements as the irradiation proceeds. The precipitates can be considered to be classified as thermally stable but modified, irradiation-enhanced, irradiation-induced, and irradiation-transformed

  9. Dual isotope (13C-14C) Studies of Water-Soluble Organic Carbon (WSOC) Aerosols in South and East Asia

    OpenAIRE

    Kirillova, Elena N.

    2013-01-01

    Atmospheric aerosols may be emitted directly as particles (primary) or formed from gaseous precursors (secondary) from different natural and anthropogenic sources. The highly populated South and East Asia regions are currently in a phase of rapid economic growth to which high emissions of carbonaceous aerosols are coupled. This leads to generally poor air quality and a substantial impact of anthropogenic aerosols on the regional climate. However, the emissions of different carbon aerosol comp...

  10. Electrospray LC-MS and the use of controlled isotope (12C : 14C) dosing for the structural elucidation of soil metabolites of a cereal herbicide

    International Nuclear Information System (INIS)

    DE-570 is a herbicide developed by Dow AgroSciences LLC for the control of broad leaf weeds in cereal crops. Laboratory metabolism studies to determine the route and rate of degradation of 14C labelled DE-570 in soil indicated the formation of a number of metabolites which required identification to satisfy European and North American regulatory guidelines. This paper describes the work carried out by Electrospray (ESI) LC-MS for the structural elucidation of these metabolites and discusses a novel approach of using controlled isotopic (12C/14C) dosing of the parent herbicide to aid the metabolite identification process

  11. Hofmann elimination of p-nitrophenylethyl-1-C-14-trimethylammonium bromide: a carbon-14 isotope effect study (Preprint no. AR-24)

    International Nuclear Information System (INIS)

    The alpha carbon isotope effects in the Hofmann elimination of p-nitrophenylethyl-1-C-14-trimethylammonium bromide compound have been measured under changing buffer concentrations with a view to correlate mechanistic change. Since there are alpha-carbon isotope effects and the effects are small it is quite likely that the reaction is of the ElcB type, predominately irreversible, with the incursion of slightly increasing fractions of reaction by the reversible mechanism as the buffer concentration is increased. (author). 4 refs., 2 tab

  12. C-14 and Ar-39 content in a ground water aquifer in the Saarland - comparison of two ground water isotope dating methods

    International Nuclear Information System (INIS)

    For the Ar-39 groundwater ages found an age comparison is made with ground waters investigated for C-14, Kr-85 and H-3 contents. The location of investigation is a sandstone aquifer of Southern Saarland. The underground production of Ar-39 the hydrological applicability. In granite, the average concentration of U, Th, K, and Cl with an average porosity of 1% and complete diffusion of the isotopes Ar-39 and Cl-36 produced underground can be as high as 105% for Ar-39 moderated and 16% Cl-36 moderated in the interstitial water. (DG)

  13. Compatibility of technologies with regulations in the waste management of H-3, I-129, C-14, and Kr-85. Part I. Initial information base

    Energy Technology Data Exchange (ETDEWEB)

    Trevorrow, L.E.; Vandegrift, G.F.; Kolba, V.M.; Steindler, M.J.

    1983-08-01

    This report summarizes the information base that was collected and reviewed in preparation for carrying out an analysis of the compatibility with regulations of waste management technologies for disposal of H-3, I-129, C-14, and Kr-85. Based on the review of this literature, summaries are presented here of waste-form characteristics, packaging, transportation, and disposal methods. Also discussed are regulations that might apply to all operations involved in disposal of the four nuclides, including the processing of irradiated fuel in a fuel reprocessing plant, packaging, storage, transport, and final disposal. The compliance assessment derived from this information is reported in a separate document. 309 references.

  14. Compatibility of technologies with regulations in the waste management of H-3, I-129, C-14, and Kr-85. Part I. Initial information base

    International Nuclear Information System (INIS)

    This report summarizes the information base that was collected and reviewed in preparation for carrying out an analysis of the compatibility with regulations of waste management technologies for disposal of H-3, I-129, C-14, and Kr-85. Based on the review of this literature, summaries are presented here of waste-form characteristics, packaging, transportation, and disposal methods. Also discussed are regulations that might apply to all operations involved in disposal of the four nuclides, including the processing of irradiated fuel in a fuel reprocessing plant, packaging, storage, transport, and final disposal. The compliance assessment derived from this information is reported in a separate document. 309 references

  15. Supported Ionic Liquid Phase (SILP) Catalysis for the Production of Acetic acid by Methanol Carbonylation

    OpenAIRE

    Hanning, Christopher William; Fehrmann, Rasmus; Riisager, Anders

    2012-01-01

    Denne afhandling omhandler udviklingen af en ny kemisk proces. Ved at benytte et rhodium-kompleks i en supporteret ionisk væskefase (Supported Ionic Liquid Phase, “SILP”) som katalysator for carbonyleringsreaktionen mellem methanol og kulilte kan eddikesyre fremstilles. Carbonyleringen af methanol bruges til industriel fremstilling af eddikesyre på megaton-skala, hvilket er et vigtigt udgangsstof for at lave plastik, fibre, tekstiler og bindere som f.eks. lim. Ved at anvende SILP-båret kataly...

  16. Phase diagram determination and thermodynamic modeling of the Cu-Mg-Si system

    OpenAIRE

    Zhao J; Zhou J.; Liu S.; Du Y.; Tang S.; Yang Y

    2016-01-01

    13 ternary Cu-Mg-Si alloys were prepared by means of the powder metallurgy method. Phase equilibria at 500 and 700 oC of the Cu-Mg-Si system were determined using X-ray diffraction analysis (XRD). The existence of 3 ternary compounds in this system was verified: CuMgSi_Sigma (Cu16Mg6Si7), Tau (Cu3Mg2Si), and Laves ((Cu0.8Si0.2)2(Mg0.88Cu0.12)). A thermodynamic modeling for the Cu-Mg-Si system was then conducted on the basis of the experimental data obtained...

  17. Correlation factors for C-14, Cl-36, Ni-59, Ni-63, Mo-93, Tc-99, I-129 and Cs-135. In operational waste for SFR 1

    Energy Technology Data Exchange (ETDEWEB)

    Lindgren, Maria; Pettersson, Michael; Wiborgh, Marie (Kemakta AB, Stockholm (SE))

    2007-01-15

    The use of correlation factors is one possibility to estimate a reference radionuclide inventory for the purpose of safety assessment studies, when waste-type specific information is not at hand. The correlation factor approach requires that there is a correlation between the activity content of the difficult-to-measure nuclide and the key nuclide. A safety assessment of a future deep repository for low and intermediate level waste (SFL 3-5) was conducted during the second half of the 1990's. Within that project, correlation factors for estimating the inventory of radionuclides which are difficult to measure experimentally were developed. These factors have also partly been used to estimate a reference inventory for SFR 1. Based on a literature survey and recent reports published by SKB, it is concluded that new information is available making an update of some correlation factors relevant. For these radionuclides, reported data from estimations and measurements of radionuclide content and correlation factors in different types of radioactive wastes are summarised. The data is evaluated and updated correlation factors representative for fresh waste for eight radionuclides (C-14, Cl-36, Ni-59, Ni-63, Mo-93, Tc-99, I-129 and Cs-135) are suggested. New information from measurements in Swedish NPP has made it possible to define factors that are BWR and PWR specific for C-14, Ni-59 and Ni-63. The uncertainties in suggested data and the applicability of the correlation factors for estimates of the radionuclide content in operational waste are commented upon

  18. Characterization of recent Lake Tahoe fault activity: Combining Sub-Meter Resolution Seismic Imagery with AMS C-14 Dated Submerged Paleo-Surfaces.

    Science.gov (United States)

    Dingler, J. A.; Kent, G. M.; Babcock, J. A.; Driscoll, N. W.; Harding, A. J.; Gayes, P. T.; Karlin, B.; Morgan, C. W.; Heyvaert, A.; Richards, B. C.

    2002-12-01

    Deformational strain within the Lake Tahoe Basin was mapped during previous campaigns using a combination of high resolution seismic CHIRP, multi-beam swath bathymetry, and airborne laser altimetry. These previous campaigns identified submerged paleo-shorelines of Pleistocene to early Holocene age, which act as a tectonic strain marker due to fault related disruptions of this once flat surface, as well as significantly offset fault scarps. Building upon this previous work, specific sites were selected for additional investigation with seismic CHIRP and AMS C-14 dated vibra and piston cores. The combination of these three techniques is ideally suited for quantifying recent fault activity through the correlation of paleo-surfaces and accurate age determinations. Initial analysis of seismic CHIRP and piston coring conducted in Emerald Bay shows a complex normal fault system with a sedimentation rate much higher than other parts of the lake. Seismic CHIRP conducted near Zephyr Cove was able to image multiple paleo-shorelines. Vibra coring of these same surfaces recovered sands of the same consistency as beach sand. Additional piston cores were collected at various lake locations below 400 m depth, including two cores taken across the Stateline Fault. Core analysis and AMS C-14 dating combined with site-specific seismic CHIRP, and previous mapping, will improve chronological control on the fault activity within the Lake Tahoe Basin.

  19. Correlation factors for C-14, Cl-36, Ni-59, Ni-63, Mo-93, Tc-99, I-129 and Cs-135. In operational waste for SFR 1

    International Nuclear Information System (INIS)

    The use of correlation factors is one possibility to estimate a reference radionuclide inventory for the purpose of safety assessment studies, when waste-type specific information is not at hand. The correlation factor approach requires that there is a correlation between the activity content of the difficult-to-measure nuclide and the key nuclide. A safety assessment of a future deep repository for low and intermediate level waste (SFL 3-5) was conducted during the second half of the 1990's. Within that project, correlation factors for estimating the inventory of radionuclides which are difficult to measure experimentally were developed. These factors have also partly been used to estimate a reference inventory for SFR 1. Based on a literature survey and recent reports published by SKB, it is concluded that new information is available making an update of some correlation factors relevant. For these radionuclides, reported data from estimations and measurements of radionuclide content and correlation factors in different types of radioactive wastes are summarised. The data is evaluated and updated correlation factors representative for fresh waste for eight radionuclides (C-14, Cl-36, Ni-59, Ni-63, Mo-93, Tc-99, I-129 and Cs-135) are suggested. New information from measurements in Swedish NPP has made it possible to define factors that are BWR and PWR specific for C-14, Ni-59 and Ni-63. The uncertainties in suggested data and the applicability of the correlation factors for estimates of the radionuclide content in operational waste are commented upon

  20. Development of technologies for the waste management of I-129, Kr-85, C-14 and tritium in the Fed. Rep. of Germany

    International Nuclear Information System (INIS)

    The main source of I-129, Kr-85, C-14 and tritium in Germany will be a 10-15 GWe LWR fuel reprocessing plant (FRP), expected to be in operation in the mid nineties. Guidelines for release regulations and development efforts are discussed. It has been recommended to limit the annual I-129 release to less than 0.2 curie. The uncontrolled release of Kr-85, C-14 or tritium via the stack resulting from the 15 GWe power will not exceed the limits derived from the German radiation protection ordinary. The development and hot demonstration of a Kr-85 control technology is recommended in view of the anticipated increasing use of nuclear power in the future. Commercial use of Xe and Kr may also contribute to the incentive for recovery. It would be simple to recover 14CO2 once separated in the course of the I-129 or Kr-85 removal operations. Tritiated waste water once it has been separated in the course of processing, should not be deliberately released. Therefore, tritium control technology is being developed. General concepts and the present status of reference and back-up technologies as well as additional research in view of advanced processes are summarized

  1. Improved insulin sensitivity after exercise training is linked to reduced plasma C14:0 ceramide in obesity and type 2 diabetes

    DEFF Research Database (Denmark)

    Kasumov, Takhar; Solomon, Thomas; Hwang, Calvin; Huang, Hazel; Haus, Jacob M; Zhang, Renliang; Kirwan, John P

    2015-01-01

     = 0.009) ceramide were negatively correlated with the increase in insulin sensitivity. CONCLUSIONS: Ceramides are linked to exercise training-induced improvements in insulin sensitivity, and plasma C14:0 ceramide may provide a specific target for investigating lipid-related insulin resistance in......OBJECTIVE: To assess the effect of exercise training on insulin sensitivity and plasma ceramides in obesity and type 2 diabetes (T2D). METHODS: Twenty-four adults with obesity and normal glucose tolerance (NGT, n = 14) or diabetes (n = 10) were studied before and after a 12-week supervised exercise......-training program (5 days/week, 1 h/day, 80-85% of maximum heart rate). Changes in body composition were assessed using hydrostatic weighing and computed tomography. Peripheral tissue insulin sensitivity was assessed by a 40 mU/m(2) /min hyperinsulinemic euglycemic clamp. Plasma ceramides (C14:0, C16:0, C18:0, C18...

  2. Constitution of the ternary system Cr–Ni–Ti

    International Nuclear Information System (INIS)

    Highlights: •Reaction scheme and liquidus surface for Cr-Ni-Ti are given. •In the ternary the C14-type Laves phase coexists with the liquid phase. •Two ternary eutectics are identified. -- Abstract: The nature of solid–liquid phase equilibria in the ternary system Cr–Ni–Ti was investigated using electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and differential thermal analysis. Literature data on solid state phase equilibria are confirmed. The Cr2Ti Laves phase modifications coexisting with Ni–Ti phases are clarified to be hexagonal C14-type and cubic C15-type. The C14-type Laves phase γCr2Ti is found to coexist with the liquid phase. It forms in the pseudobinary peritectic reaction pmax1 from L + β(Cr,Ti) at 1389 °C. On further cooling γCr2Ti + NiTi solidify at 1202 °C in the pseudobinary eutectic emax2. In the Cr-rich part of the system ternary eutectics occur at 1216 °C (E1: L = Ni3Ti + (Ni) + β(Cr,Ti)) and 1100 °C (E2: L = NiTi + Ni3Ti + β(Cr,Ti)), respectively. No ternary eutectic is found in the Ti-rich part. Rather the eutectic trough ends in the binary eutectic L = NiTi2 + β(Ti)

  3. A transcript profiling approach reveals an abscisic acid-specific glycosyltransferase (UGT73C14 induced in developing fiber of Ligon lintless-2 mutant of cotton (Gossypium hirsutum L..

    Directory of Open Access Journals (Sweden)

    Matthew K Gilbert

    Full Text Available Ligon lintless-2, a monogenic dominant cotton (Gossypium hirsutum L. fiber mutation, causing extreme reduction in lint fiber length with no pleiotropic effects on vegetative growth, represents an excellent model system to study fiber elongation. A UDP-glycosyltransferase that was highly expressed in developing fibers of the mutant Ligon lintless-2 was isolated. The predicted amino acid sequence showed ~53% similarity with Arabidopsis UGT73C sub-family members and the UDP-glycosyltransferase was designated as UGT73C14. When expressed in Escherichia coli as a recombinant protein with a maltose binding protein tag, UGT73C14 displayed enzymatic activity toward ABA and utilized UDP-glucose and UDP-galactose as the sugar donors. The recombinant UGT73C14 converted natural occurring isoform (+-cis, trans-ABA better than (+-trans, trans-ABA and (--cis, trans-ABA. Transgenic Arabidopsis plants constitutively overexpressing UGT73C14 did not show phenotypic changes under standard growth conditions. However, the increased glycosylation of ABA resulted in phenotypic changes in post-germinative growth and seedling establishment, confirming in vivo activity of UGT73C14 for ABA. This suggests that the expression level of UGT73C14 is regulated by the observed elevated levels of ABA in developing fibers of the Li 2 mutant line and may be involved in the regulation of ABA homeostasis.

  4. Primary productivity C-14 and algal assay in the study of water pollution effects in the Citarum River and Jatiluhur Reservoir

    International Nuclear Information System (INIS)

    Water quality of the Citarum River and the Jatiluhur Reservoir in Indonesia was evaluated using C-14 radioisotope. A close relationship between the abiotic (physical and chemical) and the biotic (algal growth potential, primary productivity, chlorophylla and diversity index of planktonic and benthic macroinvertebrate) parameters was obtained. Algal growth potential to abiotic parameters relationship has the highest correlation coefficient and can be used as a pollution indicator. The other biotic parameters do not show clear relationship with the abiotic parameters. The Citarum water quality is the lowest in those locations which receive human and industrial waste from Bandung and its environment. This water cannot be used for drinking purposes and fishery. The water quality in other locations of the river, however, meets the criteria for agriculture. Agricultural waste does not show any drastic effect on the water quality profile due to non-polluted characteristics of its sources

  5. C-14 dating and C-13/C-12 isotopic ratio in soils covered by natural vegetation of cerrado-floresta ecosystem at Humaita (AM)/Brazil

    International Nuclear Information System (INIS)

    The most recent evidences show that in the Amazon region significant climatic changes occurred in the Quaternary, with emphasis to the dry periods during the Pleistocene and increased precipitation in the Holocene. In this region are found areas with characteristics of cerrado, surrounded by tropical rain forest. The evaluations of soil, vegetation and climate interactions for the formation of these areas are important. Carbon isotopes (12 C, 13 C, 14 C) have been applied in soil organic matter (SOM) of Humaita region, southern Amazon, to evaluate changes in vegetation communities during the Holocene. Isotopic composition of SOM in the deeper part of the soil profiles, shows that probably in the early Holocene the forest has been in the area today occupied by the cerrado vegetation. The results of SOM in the shallow part of soil profiles characterize perfectly the three types of actual vegetation communities. (author)

  6. The measurement of neutron differential scattering cross sections for 12C, 14N and 16O in the energy range 20-26 Mev

    International Nuclear Information System (INIS)

    The Ohio University Beam Swinger provides a high resolution, low back-ground time-of-flight facility for the measurement of elastic and inelastic neutron scattering. It has been used to obtain a comprehensive set of differential scattering cross sections for 12C, 14N, 16O and 40Ca between 18 and 26 MeV. The elastic cross sections can be used directly to obtain partial kerma factors and, combined with the known total cross sections, provide accurate values for the reaction cross sections. Angular distributions have been measured for inelastic scattering from all the nuclear levels that cannot decay by particle emission thus providing (by subtraction) a limit on the sum of all charged-particle producing reactions. The integrated cross sections for inelastic scattering from some particle-unstable states in 12C are in excellent agreement with the cross sections for three-body breakup obtained by Antolkovic et al. The differential data have been used, together with higher energy proton scattering data to produce energy-dependent optical model parameters for each of these nuclei in the energy range 20-60 MeV. It has been found that the elastic differential cross sections at theta > 1000 for 12C, 14N and 16O cannot be well described by a spherical optical model. Explicit consideration of coupled-channel effects, and in the case of 12C, deformation of the ground state, improves the agreement between calculation and experiment. Heavy ion recoil kerma factors and reaction cross sections have been obtained for each element and compared with previous calculations and measurements

  7. Test of the suitability of ECOPATH/ECOSIM modelling software as a compliment to estimate flows of carbon, C-14 and radionuclides in the Oeregrundsgrepen area

    Energy Technology Data Exchange (ETDEWEB)

    Sandberg, Johannes [Stockholm Univ. (Sweden). Dept. of Systems Ecology

    2004-04-01

    In this study it was evaluated whether the ECOPATH with ECOSIM software could be used as a standard platform to facilitate for radioecologists to construct and study transport and accumulation of radionuclides in aquatic food webs. The evaluation was based upon: 1) a previously published food web model of carbon/carbon-14 flow for the Oeregrundsgrepen area, Baltic Sea, 2) a generic model, 3) an ECOSIM model and 4) an ECOTRACE model. The results presented clearly shows that there is great potential for a successful development of this scientific approach in the future. The original carbon flows and assumptions was easily incorporated into the ECOPATH with ECOSIM modelling environment. The carbon flows differed only negligible between the two models, except for the benthic flows, which was more accurately described in this study. Further, by using ECOPATH it was easily discovered that the growth efficiencies used in the original model was quite high, being 47% for most of the heterotrophs, which are high from an ecological point of view. However, that is probably due to differences in how the carbon flows have been estimated in the original versus the present study. It is likely, however that the carbon demand has been underestimated in the original model. The generic model was parameterised from data available through the software as well from the diets and assumptions used in the original carbon model. The use of these parameters resulted in carbon flows, which was between 0.7 to 11 times the flows estimated by the ECOPATH model. The difference was greatest for primary producers being 3.7 to 11 times the original flows. Thus, depending on the question one is addressing it was suggested that the use of generic parameters is best for making test models of carbon and radionuclide flows in ecosystems, where the data set for validation is limited. Finally, the ECOPATH and ECOSIM model was well suited to drive a C-14 flow model, such as ECOTRACER for each of the

  8. Test of the suitability of ECOPATH/ECOSIM modelling software as a compliment to estimate flows of carbon, C-14 and radionuclides in the Oeregrundsgrepen area

    International Nuclear Information System (INIS)

    In this study it was evaluated whether the ECOPATH with ECOSIM software could be used as a standard platform to facilitate for radioecologists to construct and study transport and accumulation of radionuclides in aquatic food webs. The evaluation was based upon: 1) a previously published food web model of carbon/carbon-14 flow for the Oeregrundsgrepen area, Baltic Sea, 2) a generic model, 3) an ECOSIM model and 4) an ECOTRACE model. The results presented clearly shows that there is great potential for a successful development of this scientific approach in the future. The original carbon flows and assumptions was easily incorporated into the ECOPATH with ECOSIM modelling environment. The carbon flows differed only negligible between the two models, except for the benthic flows, which was more accurately described in this study. Further, by using ECOPATH it was easily discovered that the growth efficiencies used in the original model was quite high, being 47% for most of the heterotrophs, which are high from an ecological point of view. However, that is probably due to differences in how the carbon flows have been estimated in the original versus the present study. It is likely, however that the carbon demand has been underestimated in the original model. The generic model was parameterised from data available through the software as well from the diets and assumptions used in the original carbon model. The use of these parameters resulted in carbon flows, which was between 0.7 to 11 times the flows estimated by the ECOPATH model. The difference was greatest for primary producers being 3.7 to 11 times the original flows. Thus, depending on the question one is addressing it was suggested that the use of generic parameters is best for making test models of carbon and radionuclide flows in ecosystems, where the data set for validation is limited. Finally, the ECOPATH and ECOSIM model was well suited to drive a C-14 flow model, such as ECOTRACER for each of the

  9. Synthesis and Structural Characterization of Two Molybdenum—phosphate Cluster Compounds:(C14N14H63)Na(H2Mo6P4O31)2·8H2O and (C14N14H63)Na(H2Mo6P4O31)2·5H2O

    Institute of Scientific and Technical Information of China (English)

    温福山; 陈伟; 等

    2002-01-01

    (C14N14H63)Na(H2Mo6P4O31)2·8H2O with amine-separatecd sodium molybdenumphosphate clusters and (C14N14H63)Na(H2Mo6P4O31)2·5H2O (2) with H-bonded cluster layers were synthesized from hydrothermal systems.Compound 1 crystal-lizes in the triclinic space group P-↑1 with a=1.27445(2) nm,b=1.37183(3)nm,c=1.41515(3) nm,α=100.497(1)°,β=109.064(1)° and γ=115.498(1)°,Whereas compound 2 has a monoclinic space group P21/n with a=1.3418(5)nm,b=2.7787(12)nm,c=2.0314(10)nm and β=96.571(14)° There exist protonated ethylenediamine cations and H2O molecules between adjacent clusters,connecting the clusters through H-bonds.

  10. C-14-activity incorporation into the protein of fetal organs of guinea pigs with different maternal placental blood flow and fetal arterial O2-saturation

    International Nuclear Information System (INIS)

    In anaesthesised gravid guinea-pigs the dilate, end section of a placental radial artery was connected to the A.carotis via a flow meter and a throttle in order to measure and widely alter the maternal placental blood flow. Blood samples are taken from the fetal A.carotis, the fetal arterial O2-saturation and the Hb-content were determined. By altering the maternal placental blood circulation the fetal arterial O2-concentration can stabilised at various levels. In order to study the protein synthesis, under these conditions one infused 185 kBq C-14-leucine over a period of 3 hours into the jugular vein of the fetus. During infusion the radioactive concentrations in whole plasma and plasma water were measured. After the infusion the radioactive concentrations in the tissue fluid, the intracellular fluid and the acid-insoluble tissue fraction (protein) of the heart, kidenys, liver, the muscles of the upper end lower part of the body, the brain and the placenta were measured. The following deductions were drawn from the findings: The maternal placental blood flow vitally influences the activity incorporation per activity concentration in the plasma water. These findings agree with the hypotheses that the maternal blood circulation has an essential influence on the fetal proteins synthesis and that this influence can be attributed to the connection between placenta connection blood flow and oxygen saturation of fetal arterial blood. (orig.)

  11. Ternary mixtures of alkyltriphenylphosphonium bromides (C12TPB, C14TPB and C16TPB) in aqueous medium: their interfacial, bulk and fluorescence quenching behaviour

    Indian Academy of Sciences (India)

    Gargi Basu Ray; Soumen Ghosh; Satya P Moulik

    2010-03-01

    The self-aggregation behaviour of ternary mixtures of alkyl (C$_{12}^{-}$, C$_{14}^{-}$ and C$_{16}^{-}$) triphenylphosphonium bromides was studied by conductometry and tensiometry. The pure surfactants showed two Critical Micellar Concentrations (CMCs) by conductometry, but their ternary mixtures produce single CMC both by conductometry and tensiometry. The CMC values determined were found to be lower than that obtained from Clint equation suggesting synergistic interaction among the monomers within the micelles. Their bulk properties, like fraction of counterions bound to the micelles and free energy of micellization were evaluated. Interfacial parameters, like surface excess, minimum head group area of monomer and free energy of adsorption were also assessed. Interfacial adsorption was found to be more spontaneous than micellization. The head group area per monomer in ternary systems was larger than pure systems due to stronger electrostatic repulsion among the charged head groups. The values of the packing parameters supported the pure as well as ternary micelles to be spherical. The TPB surfactants efficiently quenched pyrene fluorescence; the performances of the homologues in this respect were assessed.

  12. Determination of deep water circulation in the East Atlantic Ocean by means of a box-model based evaluation of C-14 measurements and other tracer data

    International Nuclear Information System (INIS)

    Radiocarbon (C-14) measurements proved to be an efficient means of determining the average, large-area deep water circulation in the Atlantic Ocean. The thesis under review explains and discusses measurements carried out in the equatorial West Atlantic and North Atlantic Ocean. The samples have been taken during mission 56 of the RS 'meteor' in spring 1981. The gas has been obtained by vacuum extraction and the measurements have been performed in proportional counter tubes, the error to be accounted for amounting to 2per mille. These measured data, together with measurements of the potential temperatures, the silicate and CO2 concentrations, and measured data from the South-East Atlantic Ocean, have been used to calculate on the basis of a box model of the Atlantic Ocean the deep water flow from the West to the East Atlantic Ocean, the deep water circulation between the various East Atlantic basins, and the turbulent diffusion coefficients required to parameterize the deep water mixing processes. (orig./HP)

  13. Phase stability of oxide dispersion-strengthened ferritic steels in neutron irradiation

    International Nuclear Information System (INIS)

    Oxide dispersion-strengthened ferritic steels were irradiated by neutrons up to 21 dpa and studied by microstructural observation and microchemical analysis. The original high dislocation density did not change after neutron irradiation, indicating that the dispersed oxide particles have high stability under neutron irradiation. However, there is potential for recoil resolution of the oxide particles due to ballistic ejection at high dose. From the microchemical analysis, it was implied that some of the complex oxides have a double-layer structure, such that TiO2 occupied the core region and Y2O3 the outer layer. Such a structure may be more stable than the simple mono-oxides. Under high-temperature irradiation, Laves phase was the predominant precipitate occurring at grain boundaries α phase and χ phase were not observed in this study

  14. Phase equilibria in the Ni-Cr-Ti system at 850 C

    International Nuclear Information System (INIS)

    The isothermal cross-section through the ternary phase diagram Ni-Cr-Ti at 850 C was constructed by means of diffusion couples and equilibrated alloys. No ternary phases exist in the system at this temperature. The topology of the isotherm is largely determined by the presence of the TiCr2-Laves phases which are in equilibrium with the binary Ti-Ni intermetallics. About 10 at.% of Ni can be dissolved in the hexagonal β-TiCr2 at 850 C, and the solubility of nickel in cubic α-TiCr2 is approximately 4 at.%. A small amount of nickel or chromium increases the stability of the b.c.c. β-Ti structure. At this temperature the β-Ti(Ni)-based solid solution can dissolve up to 18 at.% of Cr. (orig.)

  15. Prevalence of Helicobacter Pylori Infection in School and Pre-School Aged Children with C-14 Urea Breath Test and the Association with Familial and Environmental Factors

    Science.gov (United States)

    Çınar, Alev; Sadıç, Murat; İkbal Atılgan, Hasan; Baskın, Aylin; Koca, Gökhan; Demirel, Koray; Korkmaz, Meliha

    2015-01-01

    Objective: To investigate the prevalence of Helicobacter pylori (Hp) infection in pre-school and school age children with C-14 urea breath test, and to explore its association with age and socioeconomic factors in Turkey. Methods: Hp infection status was determined by using Urea Breath Test (UBT). Patients who had previous gastric surgery, Hp eradication treatment or equivocal UBT results were excluded. A questionnaire was administered to elicit information on gender, age, ABO/Rh blood group type, presence of gastric disease in the family, domestic animal in the household, and treatment for idiopathic Iron Deficiency Anemia (IDA). Results: This retrospective study included 500 pediatric patients (179 boys, 321 girls, mean age 10.7±4.3 years) of whom 62 (12.4%) were aged ≤6 years and 438 (87.6%) were aged 7 to 16 years. Helicobacter pylori (Hp) was positive in 245 (49%) cases. In the pre-school age group, 21/62 cases (34%) had positive UBT while in the school age group 224/438 children (51%) had positive UBT. A family history of dyspepsia and pet ownership were not associated with Hp positivity. Hp positive 76 (29.8%) children were on IDA treatment but this was not statistically significant. Conclusion: The Hp infection positivity rate was 49% in the pediatric age study group. The positivity rate was significantly lower at preschool age than school age, and it increased with age. There was no association with gender, ABO/Rh blood groups, presence of domestic pets, IDA, or history of gastric disease in the family. PMID:26316471

  16. Association of the p73 Gene G4C14-to-A4T14 Polymorphism with Increased Gastric Cancer Risk in a Northwestern Chinese Population

    Institute of Scientific and Technical Information of China (English)

    Weihua Zhang; Xudong Wang; Xiaodong Xie; Fengxia Guo; Rong Yang; Yuhua Liu; Shijian Xu; Yajun Yang

    2008-01-01

    OBJECTIVE To evaluate the p73 gene G4C14-to-A4T14 double nucleotide polvmorphism with both increased gastric cancer(GC)risk and different histological subtypes of GC in a northwestern Chinese population.METHODS Genotyping of the polymorphism of the p73 gene was conducted with PCR-CTPP.RESULTS All 385 GC patients including 305 diffuse-type and 80 intestinal-type cases and 412 healthy controls were investigated.The frequencies of p73 AT/AT,AT/GC,and GC/GC KenotVpes were 28.1%,47.1%,and 24.8% in the controls,and were 22.0%,45.0%,and 33.0% in GC cases respectively;the GC/GC homozygote frequency was higher in GC cases,mainly in diffuse type compared to the controls with OR=1.71(1.16~2.51)and 1.87 (95% CI,1.24~2.81)respectively.The results showed that carriers of the p73 G4A GC/GC homozygote had a 1.71-time higher risk of GC,especially of the diffuse-tvpe GC compared to the controls.The carriers of the AT/GC heterozygote also had a slightly increased risk of GC cancer, mainly on intestinal-type GC This is the first report that the p73 G4A double-nucleotide polymorphism is associated with an increased risk of diffuse-type gastric cancer.CONCLUTION The p73 G4A GC/GC genotype is associated with an increased risk of gastric cancer,especially of the GC diffuse-type.

  17. Prevalence of Helicobacter Pylori Infection in School and Pre-School Aged Children with C-14 Urea Breath Test and the Association with Familial and Environmental Factors

    Directory of Open Access Journals (Sweden)

    Alev Çınar

    2015-06-01

    Full Text Available Objective: To investigate the prevalence of Helicobacter pylori (Hp infection in pre-school and school age children with C-14 urea breath test, and to explore its association with age and socioeconomic factors in Turkey. Methods: Hp infection status was determined by using Urea Breath Test (UBT. Patients who had previous gastric surgery, Hp eradication treatment or equivocal UBT results were excluded. A questionnaire was administered to elicit information on gender, age, ABO/Rh blood group type, presence of gastric disease in the family, domestic animal in the household, and treatment for idiopathic Iron Deficiency Anemia (IDA. Results: This retrospective study included 500 pediatric patients (179 boys, 321 girls, mean age 10.7±4.3 years of whom 62 (12.4% were aged ≤6 years and 438 (87.6% were aged 7 to 16 years. Helicobacter pylori (Hp was positive in 245 (49% cases. In the pre-school age group, 21/62 cases (34% had positive UBT while in the school age group 224/438 children (51% had positive UBT. A family history of dyspepsia and pet ownership were not associated with Hp positivity. Hp positive 76 (29.8% children were on IDA treatment but this was not statistically significant. Conclusion: The Hp infection positivity rate was 49% in the pediatric age study group. The positivity rate was significantly lower at preschool age than school age, and it increased with age. There was no association with gender, ABO/Rh blood groups, presence of domestic pets, IDA, or history of gastric disease in the family.

  18. Some new experimental results on the Zr-Nb-Fe system

    International Nuclear Information System (INIS)

    The scope of this study is the identification and characterization of intermetallic phases and their binary and ternary fields in the Zr-Nb-Fe phase diagram. A construction of the central region of the phase diagram at 900 oC was proposed using new experimental results obtained by optical and scanning electron microscopies, X-ray diffraction and microprobe analysis. In addition to the well-known Laves C15-type (ZrNb)Fe2 phase (the polytypic C14 and C36 structures were not detected in the studied compositions), another Laves C14-type phase was found (Zr(NbFe)2). Watson and Bennett maps helped to predict the occurrence of both of these phases. Moreover, the validity of the Pettifor prediction model for Laves phases in pseudobinary systems with transition elements was checked, verifying the obtained experimental results in the Zr-Nb-Fe system. On the other hand it was determined that the Zr-Nb-Fe ternary system at 900 oC, as it happens in the binary Zr-Nb system, would have a miscibility gap (β-Zr + β-Nb) in the 25-70 at.% Nb composition range, accepting up to 3 at.% Fe approximately

  19. Unusual phase behavior of decane-dodecane mixtures confined in SBA-15: Size effect on binary phase diagram

    Institute of Scientific and Technical Information of China (English)

    Hai Rong Pei; Xiao Yan; Xiao Zheng Lan

    2012-01-01

    Phase behavior of normal decane-dodecane (n-C10H22-C12H26,C10-C12) system confined in SBA-15 (Santa Barbara Amorphous,pore diameters 3.8,7.8,and 17.2 nm) has been studied by using differential scanning calorimetry.It has been found solid-liquid phase diagram of the C 10-C12/SBA-15 system is composed of a straight line (3.8 nm),a curve (7.8 nm) and a loop line (17.2 nm).The growth of the phase diagram clearly shows the size effect on phase behavior of binary alkanes.Phase behavior has been compared among the systems C10H22-C12H26/SBA-15,C12H26-C14H30/SBA-15 and C14H30-C16H34/SBA-15.

  20. Characterization of oxidation products on a ZrFe{sub 2}-type laves intermetallic exposed to 200{degree}C steam.

    Energy Technology Data Exchange (ETDEWEB)

    Abraham, D. P.; Dietz, N.; Finnegan, N.

    2000-11-20

    The release of radioactive elements from the stainless steel-15 wt% zirconium (SS-15Zr) metal waste form will be governed by the corrosion behavior of ZrFe{sub 2}-type intermetallics phases present in the alloy. In this article, oxidation products that formed on a ZrFe{sub 2}-type intermetallic sample exposed to 200 C steam were characterized by Auger Electron Spectroscopy (AES) and Transmission Electron Microscopy (TEM). The data revealed two oxide layers on the sample surface: an outer crystalline iron-oxide layer and an inner amorphous zirconium-rich layer believed to be zirconium oxide. Thermodynamic considerations indicate that the zirconium-rich layer formed first. The iron-oxide layer appears to have resulted from the diffusion of iron through the zirconium-rich layer to the oxide-vapor interface.

  1. Transformation of MX into Z-phase in 9-12% Cr model alloys

    Energy Technology Data Exchange (ETDEWEB)

    Danielsen, H.K. [Technical Univ. of Denmark, Lyngby (Denmark). Dept. of Mechanical Engineering; Cipolla, L. [Technical Univ. of Denmark, Lyngby (Denmark). Dept. of Mechanical Engineering; Centro Sviluppo Materiali S.p.A, (CSM), Rome (Italy); Venditti, D. [Centro Sviluppo Materiali S.p.A, (CSM), Rome (Italy); Hald, J. [Technical Univ. of Denmark, Lyngby (Denmark). Dept. of Mechanical Engineering; DONG Energy A/S (Denmark); Vattenfall (Denmark)

    2010-07-01

    Three 9-12%Cr model alloys were designed with the purpose of studying the nucleation and precipitation kinetics of modified Z-phase, CR(V,Nb)N. The alloys were similar except for changes in the Cr and Nb contents, which allowed easy comparisons to estimate the effect these elements. The interferences from the presence of carbides and Laves phases were avoided by keeping the C, W and Mo contents as low as possible. Transmission Electron Microscopy of extraction replicas and quantitative X-Ray Diffraction analysis of extracted particles were used to follow the evolutions of phase composition, phase morphology and phase fraction of Z-phase during ageing at 650 C up to 10,000h. The Z-phase appears to nucleate by diffusion of Cr atoms into (V,Nb)N particles which subsequently convert into cubic or tetragonal Z-phase. Studies at various temperatures indicate that Z-phase development proceeds fastest at 650 C and comparison of the alloys indicate that Z-phase precipitation is greatly enhanced by elements such as Cr and Nb. (orig.)

  2. LINE LISTS FOR THE A 2Π-X 2Σ+ (RED) AND B 2Σ+-X 2Σ+ (VIOLET) SYSTEMS OF CN, 13C14N, AND 12C15N, AND APPLICATION TO ASTRONOMICAL SPECTRA

    International Nuclear Information System (INIS)

    New red and violet system line lists for the CN isotopologues 13C14N and 12C15N have been generated. These new transition data are combined with those previously derived for 12C14N, and applied to the determination of CNO abundances in the solar photosphere and in four red giant stars: Arcturus, the bright, very low-metallicity star HD 122563, and the carbon-enhanced metal-poor stars HD 196944 and HD 201626. When both red and violet system lines are detectable in a star, their derived N abundances are in good agreement. The mean N abundances determined in this work are also generally in accord with published values

  3. Ti–V–Mn based metal hydrides for hydrogen storage

    International Nuclear Information System (INIS)

    Highlights: •Ti0.47V0.46Mn and Ti0.50V0.51Mn alloys were produced by arc melting. •Compositional differences led to different unit cell volumes for the C14 Laves phase. •Change in composition caused a significant change in plateau pressure and hysteresis. -- Abstract: Two Ti–V–Mn BCC-Laves phase alloys with the nominal composition Ti0.5V0.5±xMn (x = −0.04 and 0.01), were synthesised by arc melting. This compositional difference resulted in different compositions and unit cell volumes for the C14 Laves phase. Ti0.47V0.46Mn and Ti0.50V0.51Mn demonstrated reversible hydrogen sorption capacities of 1.53 and 1.56 ± 0.05 wt.% (at 120 bar H2 at 303 K) respectively, however, the change in composition results in a small change in the enthalpy of hydride decomposition, and a significant change in plateau pressure and hysteresis. This may allow for the plateau pressure to be tuned to meet the requirements of different solid-state hydrogen storage applications

  4. Dirac metal to topological metal transition at a structural phase change in Au2Pb and prediction of Z2 topology for the superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Schoop, Leslie M.; Xie, Lilia S.; Chen, Ru; Gibson, Quinn D.; Lapidus, Saul H.; Kimchi, Itamar; Hirschberger, Max; Haldolaarachchige, Neel; Ali, Mazhar N.; Belvin, Carina A.; Liang, Tian; Neaton, Jeffrey B.; Ong, N P; Vishwanath, Ashvin; Cava, R. J.

    2015-06-23

    Three-dimensionalDirac semimetals (DSMs) arematerials that have masslessDirac electrons and exhibit exotic physical properties. It has been suggested that structurally distorting a DSM can create a topological insulator but this has not yet been experimentally verified. Furthermore, Majorana fermions have been theoretically proposed to exist inmaterials that exhibit both superconductivity and topological surface states. Herewe showthat the cubic Laves phase Au2Pb has a bulk Dirac cone that is predicted to gap on cooling through a structural phase transition at 100 K. The low temperature phase can be assigned a Z(2) = -1 topological index, and this phase becomes superconducting below 1.2 K. These characteristics make Au2Pb a unique platform for studying the transition between bulk Dirac electrons and topological surface states as well as studying the interaction of superconductivity with topological surface states, combining many different properties of emergent materials-superconductivity, bulk Dirac electrons, and a topologically nontrivial Z(2) invariant.

  5. The Cr–Fe–Nb ternary system: Experimental isothermal sections at 700 °C, 1050 °C and 1350 °C

    Energy Technology Data Exchange (ETDEWEB)

    Jacob, Aurélie, E-mail: a.jacob@fz-juelich.de [Forschungszentrum Juelich, IEK-2, 52425 Juelich (Germany); Schmetterer, Clemens [Forschungszentrum Juelich, IEK-2, 52425 Juelich (Germany); Fraunhofer-UMSICHT, 92237 Sulzbach-Rosenberg (Germany); Grüner, Daniel; Wessel, Egbert [Forschungszentrum Juelich, IEK-2, 52425 Juelich (Germany); Hallstedt, Bengt [Institute for Materials Applications in Mechanical Engineering, RWTH Aachen University, Augustinerbach 4, 52062 Aachen (Germany); Singheiser, Lorenz [Forschungszentrum Juelich, IEK-2, 52425 Juelich (Germany)

    2015-11-05

    The Cr–Fe–Nb system is an important constituent system in the development of Laves-phase reinforced steels. It contains two Laves-phase polytypes, i.e. C14–Fe{sub 2}Nb and C15–Cr{sub 2}Nb. While the first forms a substantial ternary solid solution with Cr, the latter only shows a limited solubility for Fe. The phase equilibria in the Cr–Fe–Nb system are shown in three isothermal sections at 700, 1050 and 1350 °C. Scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM/EDX), X-ray diffraction (XRD) and electron back scatter diffraction (EBSD) were used to determine the phase equilibria from which the isothermal sections were constructed. - Highlights: • Determination of Phase Equilibria in the Cr–Fe–Nb system at 700, 1050 and 1350 °C. • Isothermal sections at 700, 1050 and 1350 °C were established. • Homogeneity range of Laves phases were determined. • Solubility of Fe and Cr and lattice parameter evolution in the ternary phases were determined.

  6. Crystal structure analysis of 1-Butil-3-Siyano-4-Metil-5(2-Tiyazolilhidrazon) Piridin-2,6-Dion(C14H15N5O2S) by X-ray diffraction

    International Nuclear Information System (INIS)

    In this study, the crystal structure and molecular conformation of 1-butyl-3-cyano-4-methyl-5- (2-thiazolylhydrazone) pyridine-2.6-dione (C14H15N5O2S) has been determined from X-ray diffraction data. Monoazo disperse dyes. such as (C14H15N5O25S), are widely used in the textile industry as synthetic coloring materials. The unit cell parameters were obtained from photographic data and it was found that the crystal belongs to P1- space group of the tricilinic system. Intensity date were collected on an Enraf-Nonius CAD4 diffractometer equipped with MoKa radiation. The structure was solved by direct methods using SIMPELBB and refined by full-matrix least squares in the MolEN software. Some crystal data were determined. As the result of our structure analysis, it was shown that the structure has hydrazone tautomer form and there is a hydrogen bond between the nitrogen atom N4 and the 6-oxo group (NH...O = 2.53 A angstrom) molecular geometry was defined by PARSTBS and it was seen that the skeleton of the molecule is almost planar with te exception of butyl group

  7. Phase stability and swelling in the V-series alloys

    International Nuclear Information System (INIS)

    The response of the V-series alloys to irradiation to a fluence of 7 x 1022 n/cm2 at 5930C covers a range of behavior from a minimum swelling of 0.6% (V4) to a maximum of 8.1% (V5). The major phases identified in the V series alloys examined after irradiation to 7 x 1022 n/cm2 at 5930C are TiC and laves. Between the fluences of 2 x 1022 n/cm2 and 7 x 1022 n/cm2 the compositions of the precipitates identified do not vary significantly. Results of this investigation indicate that the minimum amount of titanium in solution should be approx. 0.16 wt %. Higher levels of titanium in solution will promote more efficient pinning of the dislocation structure and result in lower swelling. Silicon levels greater than 0.5 wt % promote severe phase instabilities which deplete the matrix of elements which suppress swelling. The irradiation performance of this type alloy depends upon the achievement of a uniform distribution of Ti and a balance of Ti, Si, and C in solution which will encourage precipitation of TiC during service

  8. Computational thermodynamics aided design of novel ferritic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ying [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Chen, Tianyi [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Tan, Lizhen [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-06-30

    With the aid of computational thermodynamics, Ni was identified to suppress the liquidus temperature of Fe2Zr and four Fe-Cr-Ni-Zr alloys were designed to study the Ni effect on the phase stability of Fe2Zr laves_phase. These alloys were fabricated through traditional arc-metling, followed by annealing at 1000 C for 336 hours and 700 C for 1275 hours. The microstructure were examined and characterized by SEM BSE image, EDS compositional mapping and point scan, XRD and TEM analysis. The major results were summarized below: 1)For investigated alloys with 12wt% Cr, 3~6wt% Zr and 3~9 wt%Ni, the phases in equilibrium with the BCC phase are C15_Laves phase, Fe23Zr6 phase. The volume fraction of intermetallic phases increases with Ni and Zr contents. 2)Instead of (Fe,Cr)2Zr C14_Laves phase, Ni stabilizes the C15_Laves structure in Fe-Cr-Ni-Zr alloys by substituting Fe and Cr atoms with Ni atoms in the first sublattice. 3)Fe23Zr6, that is metastable in the Fe-Cr-Zr ternary, is also stabilized by Ni addition. 4)Ni7Zr2 phase was observed in samples with high Ni/Zr ratio. Extensive solubility of Fe was identified in the phase. The microstructural and composition results obtained from this study will be incorportated into the the Fe-Cr-Ni-Zr database. The current samples will be subjected to ion irradiaition to be compared with those results for Fe-Cr-Zr alloys. Additional alloys will be designed to form (Fe,Cr,Ni)2Zr nanoprecipitates for further studies.

  9. Phase Transformation and Magnetostriction of (R-Pr)(Fe-T)2 (R=Dy, Tb; T=Co, Ni)

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Structure and magnetostriction of Dy1-xPrxFe2 (0 ≤x≤0.5), Dy0.6Pr0.4(Fe1-yTy)2 (0<y<0.6), and Tb1-zPrz(Fe0.4Co0.6)2 (0≤z≤1.0) alloys (T=Co, Ni) have been investigated. It is found that the matrix of the alloys Dy1-xPrxFe2 is a single phase (Dy, Pr)Fe2 with MgCu2-type structure and the second phase is (Dy, Pr)Fe3 when x≤0.2. The amount of (Dy, Pr)Fe3 phase increases with increasing Pr content and becomes the main phase when x=0.4. The matrix of Dy1-xPrxFe2 is found to be the (Dy, Pr)2Fe17 phase with Th2Zn17-type structure when x=0.5. It is found that the amount of the cubic Laves phase (Dy, Pr)(Fe, Co)2 in the Dy0.6Pr0.4(Fe1-yCoy)2 increases with increasing Co concentration when 0≤y≤0.6. The substi tution of Ni for Fe is nearly not favorable for the formation of the cubic Laves phase (Dy, Pr)(Fe, Ni)2 in (Dy1-xPrx)Fe2. The matrix of (Tbl-zPrz)(Fe0.4Co0.6)2 is a (Tb, Pr)(Fe, Co)2 phase with the MgCu2-type cubic Laves structure and a second phase of small amount is (Tb, Pr)(Fe, Co)3 phase when z≤0.2, z=0.5 and 1.0. When 0.2<z≤0.4, the amount of the (Tb, Pr)(Fe, Co)3 phase with PuNi3-type structure increases with increasing z and becomes the main phase when z=0.4. When 0.5<z≤0.6 the amount of the (Tb, Pr)(Fe, Co)3 phase increases sharply, whereas for 0.6<z≤0.8 it decreases with increasing z. The polycrystalline magnetostriction, λ‖ - λ┴, at room temperature of Dy1-xPrxFe2 exhibits a peak when x=0.3. The λ‖ - λ for Dy0.6Pr0.4(Fel-yMy)2 (M=Co, Ni) and Tb1-zPrz(Fe0.4Co0.6)2 is also examined.

  10. Phase stability in the ternary Re–W–Zr system

    International Nuclear Information System (INIS)

    Graphical abstract: Display Omitted - Abstract: The irregular shape of the χ phase in the ternary system Re–W–Zr has been investigated. Both experimental measurements (joint Rietveld refinement of neutron and X-ray diffraction data) and density functional theory (DFT) calculations were used in order to obtain the site occupancies and to determine the reason why this phase is so deeply stabilized in the ternary system. In particular, the DFT calculations of all the system compounds allowed us to assess the relative phase stability and to reproduce well the experimental phase diagram isothermal section without any adjustable parameter, including the C14-to-C15 transition. In the course of this study a partial reinvestigation of the binary Re–Zr system has been performed that concluded on the absence in the phase diagram of the previously reported Zr2Re phase. Instead, the phase Zr21Re25 was proven

  11. Genèse des magmas associés à l'ouverture d'un domaine océanique : Géochimie des laves du Nord-Est de l'Afrique (Mer Rouge-Afar) et d'Arabie

    OpenAIRE

    Barrat, Jean-Alix

    1991-01-01

    L'existence d'un point chaud localisé en Afar est confirmée. Principalement deux composants mantelliques interviennent dans la genèse des laves du Sud de la Mer Rouge et d'Afar: un manteau appauvri en LREE et une source présentant des caractéristiques du pôle HIMU. Certains basaltes des plateaux éthiopiens et d'Afar (en particulier ceux émis avant l'ouverture du Golfe de Tadjoura) sont contaminés par la croûte continentale. Les résultats analytiques présentés ici, suggèrent que certains basal...

  12. Standardization of C-14 by tracing method

    International Nuclear Information System (INIS)

    The standardization of a 14C radioactive solution by means of the efficiency tracing technique is described. The 14C is a beta pure emitter with endpoint energy of 156 keV decaying to the ground state of 14N. The activity measurement was performed in a 4πβ-γ coincidence system, measuring the pure beta emitter mixed with a beta gamma emitter, which provides the beta detection efficiency. The radionuclide 60Co, which decays by beta particle followed by two gamma rays, was used as tracer and the efficiency was obtained by selecting the 1173 keV plus 1332 keV total energy absorption peak at the gamma channel. Known aliquots of the tracer, previously standardized by 4πβ (PC)-γ coincidence, were mixed with known aliquots of 14C. The sources of 14C + 60Co were prepared by dropping known aliquots from each radioactive solution. The events were registered by a Software Coincidence System (SCS). The activity of the solution was determined by using the extrapolation technique, changing the beta efficiency by pulse height discrimination. In order to determine the final activity, a Monte Carlo simulation was used to calculate the extrapolation curve. All the uncertainties involved were treated rigorously, by means of the covariance analysis methodology. Measurements using a HIDEX, a commercial liquid scintillator system, were carried out and the results were compared with the tracing technique, showing a good agreement. (author)

  13. C-14 measurements in organic sediments

    International Nuclear Information System (INIS)

    Full text: The CO2 direct absorption method of preparing samples for radiocarbon analysis by liquid scintillation counting has been successfully applied in many laboratories primarily for 'dating' the groundwater. Even if the method follows the similar principle as by the benzene synthesis method, time less consuming by the direct absorption method is a strong motivation enhancing the type of samples that can be prepared by this method. The samples used to settle the procedure were various types of soil and slurry from the bottom sediments in rivers and lakes. The carbon occurring in those samples can be inorganic or organic carbon. Inorganic carbon can be analyzed by direct absorption method rather easy by sample acidification and CO2 capture. In this work it has been investigated a hybrid method that connects the wet oxidation of organic carbon with direct absorption method. The wet oxidation with potassium dichromate 1N solution, in presence of concentrated sulphuric acid and silver sulphate was applied to samples, prior acidification to release inorganic carbon as CO2. To overcome the concern of incomplete digestion of organic matter, the procedure was conducted by extensive heating of the sample during wet oxidation process. Possibilities of occurrence of isotopic fractionation during CO2 production from raw material were investigated by measuring δ13C from sample and the CO2 obtained. Special attention was paid to sample preparation technique and the 'direct absorption method' has been used with few 'home-made' improvements in order to increase the reproducibility and accuracy of this simple and less-time consuming method. (authors)

  14. Neutron diffraction studies of metal hydrides alloys for hydrogen storage

    International Nuclear Information System (INIS)

    In this paper we present results obtained from two different classes of metal hydrides. First, we will discuss the effect of ball milling on the hydrogen storage properties of magnesium hydride. High energy milling of MgD2 produces a nanocrystalline structure made of a mixture of β-MgD2 and the high temperature/high pressure phase γ-MgD2. Neutron powder diffraction showed that the ball-milled β-MgD2 and γ-MgD2 structures are distorted compared to the same phases synthesised at high-pressure and high temperature. The Mg-D bond lengths are modified in β-MgD2. In γ-MgD2 phase, only one bond length is changed. This may be the explanation for the limited amount of γ-MgD2 synthesized by energetic ball milling. The second case is the crystal structure of a new class of metal hydrides, the so called 'Laves phase related BCC solid solution'. From neutron diffraction, we found that two phases are present in the as-cast alloy TiV0.9Mn1.1. One is a BCC solid solution, the other is a C14 Laves phase. We found that in the C14 phase there is a preferential site for titanium atoms while the vanadium and manganese atoms are distributed on the other two sites. (author)

  15. Morphotropic Phase Boundaries in Tb1-xDyxFe2 alloys

    Science.gov (United States)

    Bergstrom, Richard, Jr.

    Magnetostrictive alloys, materials that change in dimension under an applied magnetic field, are desired candidates for transducers. Unfortunately, common magnetostrictive metals, alloys, and oxides produce such small strains that they are not a viable option. In the early 1960's rare earths were found to possess extraordinary magnetostriction values at cryogenic temperatures. When alloyed with traditional transition metals they form a Laves phase compound of the form AB2. These Laves phase compounds have shown large magnetostriction values, up to 2500μepsilon in TbFe2. A major drawback to using these materials as transducers is their huge magnetocrystalline anisotropy constants, K1 and K2. However, it was found that TbFe2 and DyFe2 have opposing signs of K1 and K2. A pseudo-binary alloy, Tb1-xDyxFe2 (Terfenol-D) TDFx, was formed to decrease the total magnetocrystalline anisotropy. The anisotropy reached a room temperature minimum for TDF73. It is suspected that this minimum of the anisotropy is accompanied by a morphotropic phase boundary (MPB) at which the crystal structure changes from tetragonal to rhombohedral. Unraveling the nature of the temperature and composition dependence of the magnetic and crystalline properties along this MPB is the primary focus of this thesis. The structure of the TDF alloys was probed through macroscopic and microscopic techniques. The maximum in the DC magnetization at the transition temperature from tetragonal to rhombohedral broadens as the transition temperature is increased. This is attributed to decreasing anisotropy at increased temperature. Synchrotron and neutron powder diffraction are utilized to elucidate the microscopic changes in the structure and magnetism. Neutron powder diffraction results were somewhat inconclusive but were sufficient to produce magnetic moments that were invariant, within experimental error, across the transition region. Synchrotron powder diffraction was used to probe the structure at

  16. Enhancement of cerium and hydrogen storage property of a low-cost Ti-V based BCC alloy prepared by commercial ferrovanadium

    Institute of Scientific and Technical Information of China (English)

    米菁; 吕芳; 刘晓鹏; 蒋利军; 李志念; 王树茂

    2010-01-01

    Based on the analysis of XRD, SEM, P-C-isotherm measurements and absorption kinetics simulation, it was indicated that Ce addition was an effective way to inhibit the formation of C14 Laves phase, improve flatness of the plateau, increase hydrogen diffusion rate and enlarge hydrogen storage capacity. The hydrogenation capacity of Ti27.25Cr28.05V37.25Fe7.45Ce1.0 alloy prepared by commercial ferrovanadium was 3.56 wt.% measured at 298 K. The dehydrogenation capacity was 2.25 wt.% and 2.54 wt.% measured at 343...

  17. Neutron diffraction studies of the cubic ZrCr2Dsub(x) and ZrV2Dsub(x)(Hsub(x)) phases

    International Nuclear Information System (INIS)

    Deuterides of ZrCr2 and both hydrides and deuterides of ZrV2 were studied by neutron diffraction in order to determine the relative occupancies of the different types of tetrahedral sites existing in the C15 Friauf-Laves phases. In ZrV2, within the range of stoichiometry used, both Zr2V2 and ZrV3 sites are occupied by deuterium with the relative occupancies depending on the total absorption. In ZrCr2 only the Zr2Cr2 site is progressively filled until the formula approaches ZrCr2Dsub(3.5), near the experimental limit of absorption, at which point a minor amount of deuterium may enter ZrCr3 sites. (Auth.)

  18. Microstructural characterization of second phases in X10CrMoVNb9-1 and 12CrMoWCuVNb steels after long steam exposure time at 550 C

    Energy Technology Data Exchange (ETDEWEB)

    Rodak, Kinga; Hernas, Adam [Silesian Univ. of Technology, Inst. of Materials Science, Katowice (Poland); Vodarek, Vlastimil [VSB-Technical Univ. of Ostrava (Czech Republic)

    2015-07-15

    Microstructural changes in high alloy (9-12% Cr) creep resistant martensitic X10CrMoVNb9-1 and 12CrMoW . CuVNb steels after 100 000 h of steam exposure at 550 C have been studied using scanning transmission electron microscopy. Precipitates were identified using electron diffraction patterns and energy dispersive X-ray spectroscopy analysis. After long time exposure, a significant coarsening of M{sub 23}C{sub 6} carbides, and intensive precipitation of the coarse Laves phase were observed. Moreover, in the 12CrMoW . CuVNb steel, a low amount of the modified Z-phase particles was detected. The microstructures of the X10Cr . MoVNb9-1 and 12CrMoWCuVNb steels after 100 000 h of exposure differ in several aspects.

  19. Aggregation in water micellar dilutes solutions of three nonionic classic surfactants: C10E7 and C12E7 and C14E7 study by SANS method

    International Nuclear Information System (INIS)

    Full text: Three nonionic classic surfactants C10E7 ( hepta ethylene glycol monodecyl ether ) and C12E7 ( hepta ethylene glycol monododecyl ether ) and C14E7 ( tetra ethylene glycol monotetradecyl ether ) in water solutions [1-2,4-5 ] were investigated for six temperatures between 10 and 35 degree Celsius) in dilute solutions for concentrations: c1 = 0.17%, c2 = 0.5% and 1% with two methods - tensiometric and small-angle neutron scattering ( SANS ) on SANS diffractometer Yellow Submarine at Budapest Neutron Center, Budapest ( Hungary ) and on SANS spectrometer (YuMO) of the IBR-2 on pulsed neutron source [3] at FLNP, JINR in Dubna ( Russia ). Measurements have covered Q range from 8x10-3 to 0.4 Amstrong-1. The micellar solutions were prepared in D2O since the contrast between the micelles and the solvent in neutron experiments is better with D2O than with H2O. It was obtained as the result that the shape of micelles changes depending on surfactant concentration and temperature. At lower concentrations and temperatures micelles are prolate ellipsoids but at higher concentrations and temperature are rather cylinders. (author)

  20. Moon Phases

    Science.gov (United States)

    Riddle, Bob

    2010-01-01

    When teaching Moon phases, the focus seems to be on the sequence of Moon phases and, in some grade levels, how Moon phases occur. Either focus can sometimes be a challenge, especially without the use of models and observations of the Moon. In this month's column, the author describes some of the lessons that he uses to teach the phases of the Moon…

  1. Low-density, refractory multi-principal element alloys of the Cr–Nb–Ti–V–Zr system: Microstructure and phase analysis

    International Nuclear Information System (INIS)

    The crystal structure, microstructure, density and Vickers hardness of four multi-principal element alloys, NbTiVZr, NbTiV2Zr, CrNbTiZr, and CrNbTiVZr, are reported. The characteristics of these potential new high-temperature structural alloys are explored. The alloys were prepared by vacuum arc melting followed by hot isostatic pressing (at 1200 °C, 207 MPa for 1 h) and homogenization annealing (at 1200 °C for 24 h). The alloys have densities of 6.52, 6.34, 6.67 and 6.57 g cm−3, and Vickers microhardness values of 3.29, 2.99, 4.10 and 4.72 GPa, respectively. The NbTiVZr alloy is essentially a single-phase alloy consisting of a coarse-grained disordered body-centered cubic (bcc) phase with fine, submicron-size precipitates inside the grains. The NbTiV2Zr alloy contains three disordered bcc phases. The CrNbTiZr and CrNbTiVZr alloys contain a disordered bcc phase and an ordered Laves phase. The lattice parameters and compositions of the identified phases are reported. The experimental data are compared with the results of the thermodynamic modeling of non-equilibrium and equilibrium phases in these alloys

  2. Microstructural evolution and creep of Fe-Al-Ta alloys

    Energy Technology Data Exchange (ETDEWEB)

    Prokopcakova, Petra; Svec, Martin [Technical University of Liberec (Czech Republic). Dept. of Material Science; Palm, Martin [Max-Planck-Institut fuer Eisenforschung GmbH, Duesseldorf (Germany). Structure and Nano-/Micromechanics of Materials

    2016-05-15

    The microstructural evolution in Fe-Al-Ta alloys containing 23 - 31 at.% Al and 1.5 - 2.2 at.% Ta has been studied in the temperature range 650 - 750 C by annealing for 1, 10, 100 and 1 000 h. The experiments confirm that in this temperature range the precipitation of the stable hexagonal C14 Laves phase is preceded by formation of coherent, metastable L2{sub 1} Heusler phase precipitates within the Fe-Al matrix. However, precipitates of C14 are observed after much shorter annealing times than previously assumed. Creep strength increases substantially with increasing Al content of the alloys because the solid solubility for Ta in the Fe-Al matrix increases with increasing Al content and solid-solution hardening contributes substantially to the observed high creep strength. It may therefore be that the microstructural changes during creep have no noticeable effect on creep strength.

  3. Microstructural evolution and creep of Fe-Al-Ta alloys

    International Nuclear Information System (INIS)

    The microstructural evolution in Fe-Al-Ta alloys containing 23 - 31 at.% Al and 1.5 - 2.2 at.% Ta has been studied in the temperature range 650 - 750 C by annealing for 1, 10, 100 and 1 000 h. The experiments confirm that in this temperature range the precipitation of the stable hexagonal C14 Laves phase is preceded by formation of coherent, metastable L21 Heusler phase precipitates within the Fe-Al matrix. However, precipitates of C14 are observed after much shorter annealing times than previously assumed. Creep strength increases substantially with increasing Al content of the alloys because the solid solubility for Ta in the Fe-Al matrix increases with increasing Al content and solid-solution hardening contributes substantially to the observed high creep strength. It may therefore be that the microstructural changes during creep have no noticeable effect on creep strength.

  4. Can Early Life-Stages of the Marine Fish Sparus aurata be Useful for the Evaluation of the Toxicity of Linear Alkylbenzene Sulphonates Homologues (LAS C10-C14 and Commercial LAS?

    Directory of Open Access Journals (Sweden)

    M. Hampel

    2002-01-01

    Full Text Available Most commercial household cleaning agents and personal care products contain the anionic surfactant linear alkylbenzene sulphonates (LAS as the active compound. After their use they are discharged, theoretically after adequate wastewater treatment, into receiving waters finally reaching estuaries and coastal waters. Laboratory toxicity tests are useful tools in determining at which concentration a certain wastewater compound becomes hazardous for an existing group of organisms. Early life-stage toxicity tests include exposure during the most sensitive development period of the organism. In fish, this type of assay has shown to predict accurately maximum acceptable toxicant concentration (MATC values (comprised in the range defined by the NOEC and LOEC in fish early life-stage tests. For this reason, larvae of the seabream, Sparus aurata, were exposed to increasing concentrations of LAS homologues (C10-C14 and commercial LAS. Obtained LC50 values ranged between 0.1 and 3.0 mg l-1 and were compared with LC50 values of previous hatching experiments with the same species. Larvae proved to be more sensitive to LAS exposure of individual homologues than eggs, except in the case of commercial LAS. LC50 values can be directly employed to determine their potential risk in a concrete environment with known pollutant concentrations. Dividing the LC50 value with the found homologue concentration and extrapolating with certain security factors proposed by different environmental organisms, potentially hazardous pollutant concentrations may be detected. Average estuarine or coastal LAS concentrations are generally below toxicity limits for this kind of organism, considering that the average alkyl chain length of commercial LAS is 11.6 carbon atoms.

  5. Effect of Deleterious Phases on Corrosion Resistance of Duplex Stainless Steel (2205

    Directory of Open Access Journals (Sweden)

    AbdulKadar M. Godil

    2013-07-01

    Full Text Available Duplex stainless steel is a Ferritic(BCC-Austenitic(FCC steel, covers the advantages of both Austenitic and Ferritic Stainless steels. They having good mechanical and corrosion resistance properties are widely used in many industries like chemical plants, refineries for critical equipments such as pressure vessels, heatexchangers, water heaters. Major problem occurs with duplex steels when they are worked or heated above about temperature of 280°C. Detrimental phases like Sigma, Chi, Laves and Alpha prime form when the Duplex steels are treated above this temperature and they retard the properties of Duplex stainless steels. They also cause embrittlement above temperature of 475°C called “475°C embrittlement”. During welding of duplex steels, Secondary austenite also forms, which is also one of the harmful phases in duplex steels. Among all of these phases, Sigma (σ is extremely harmful to the corrosion resistance of steel. Due to these limitations duplexgrades are not used above certain temperature ranges. In this experimental work a plate of duplex grade 2205 in hot worked condition was procured from TCR Advanced Engineering Pvt. Ltd., GIDC, Vadodara. Initially chemical composition of the plate was checked with emission spectrometer, tensile test and hardness tests werecarried out for comparing with the standard data. As there was no Sigma phase detected when tested with ASTM 930 in the received sample, Sigma phase was intentionally produced by giving heat treatment in the range of 700-850°C. Sigma phases were quantified with ASTM 930 practice A, by electrolytic etching with 40% NaOH. The effect of Sigma phase on corrosion resistance was measured by ASTM G48. The pitting corrosion resistance was evaluated in terms of average pit depth and overall corrosion rate.

  6. Investigation of the isothermal precipitation behaviour of nickel-base alloys using electrochemical phase extraction

    International Nuclear Information System (INIS)

    Electrochemical phase extraction methods have been developed empirically for the selective separation of the precipitates in metallic materials. A detailed description of the process has been undertaken to allow optimization for various nickel-base alloys. For this part of the investigation, 16 model alloys were prepared as test electrodes and the electrolyte composition was varied over a wide range. The results enabled a series of effects to be explained on the basis of electrochemical data. The large number of test parameters limited the scope of the preliminary experiments and the range of model alloys used. In the nickel-base alloys, titanium carbo-nitride and primary M6C precipitates were identified. During isothermal ageing, M23C6 (except in Alloy KSN), Ni3Al (in INCONEL 617), Laves phases (in Hastelloy X and INCONEL 617), M12C (in HASTELLOY X and INCONEL 617) and α-tungsten (in the tungsten-containing alloys) were precipitated. The precipitation behaviour changed in the alloys investigated from intracrystalline to intercrystalline with increasing ageing temperature. The intracrystalline secondary precipitations affect the microhardness, structure and the solid-solution lattice. (orig.)

  7. Effect of component substitution on the magnetic properties of Zr2Co11 phase and rapidly quenched Zr2Co11 - based alloys

    International Nuclear Information System (INIS)

    Magnetic properties of homogenized ingots and rapidly quenched ribbons of (Zr1-xMx)16.4Co83.6 with M=Ti, Nb, Y, Gd and Zr16.4(Co1-yM*y)83.6 with M*= Mn, Fe, Ni, Cu, Al, Ga, Si are studied. The phase composition of the alloys is determined with the help of thermomagnetic analysis and, in specific cases, with the use of X-ray diffraction analysis and electron microscopical data. It is ascertained that a part of zirconium in a phase Zr2Co11 can be replaced by titanium and niobium. The solubility of rare earth elements is noted to be not revealed. Cobalt is partially replaced by Al, Cu, Ga, Si, Ni and Fe in a 2:11 phase, and Mn stabilizes the structure of a Laves phase with unexpectedly strong ferromagnetic properties. For magnetic hardness of the rapidly quenched alloys the introduction of Ti is appeared to be most beneficial. This element enhances noticeably the coercive force and hysteresis loop rectangularity and, as it takes place, it does not change practically magnetic properties of a 2:11 phase but suppresses the formation of dendrites on its crystallization. A small increase of the coercive force is also observed on addition of Cu and Al

  8. Microstructural characterization of second phase irradiated Zircaloy-4 particles

    International Nuclear Information System (INIS)

    X-ray diffraction diagrams of neutron irradiated Zircaloy-4 were obtained at the LNLS with the aim to obtain bulk information about the amorphization process in which the Zircaloy-4 second phase particles (SPPs) undergoes due to neutron irradiation. Owing to the low concentration of the SPPs in the alloy (∼0.4 V %), no data regarding to the bulk were obtained until now. The synchrotron experiences allowed to detect five of the more intense lines of the phase C 14 (SPPs structure) in unirradiated Zircaloy-4: (110) θ, (103) θ, (112) θ, (201) θ and (004) θ in the 34 degrees ≤ θ2≤45 degrees Bragg angle range and others of minor intensity. The diagrams of the samples irradiated at moderate doses (1020n/cm2) show these lines even in the as received samples. In contrast, none of these lines are observed for high fluence samples (∼1022neutrons/cm2). In addition, in similar high fluence samples annealed 24 h or 72 h at 600 C degrees the intensity rises just at the 2q range where the C 14 lines were observed, showing a wide peak. That peak is interpreted as a result of the superposition of unresolved diffraction lines corresponding to the Zircaloy SPPs which are in a reconstitution process of crystallization. Analytical Electron Microscopy techniques were used, in order to study the effects on the Zircaloy-4 SPPs and compared with samples of the same material without irradiation. Spots in SAD patterns of non irradiated SPPS, evidences the presence of a C 14 structure, but in irradiated SSP SAD patterns evidences the beginning of an amorphization process. Another important feature to point out is the different Fe / Cr ratio presented in both irradiated and non irradiated SSPs. In non irradiated precipitates the Fe / Cr ratio is approximately 1.5, while in irradiated precipitates the Fe / Cr ratio becomes near 1.0. (author)

  9. Study of the mechanical behavior of the hydride blister/rim structure in Zircaloy-4 using in-situ synchrotron X-ray diffraction

    Science.gov (United States)

    Lin, Jun-li; Han, Xiaochun; Heuser, Brent J.; Almer, Jonathan D.

    2016-04-01

    High-energy synchrotron X-ray diffraction was utilized to study the mechanical response of the f.c.c δ hydride phase, the intermetallic precipitation with hexagonal C14 lave phase and the α-Zr phase in the Zircaloy-4 materials with a hydride rim/blister structure near one surface of the material during in-situ uniaxial tension experiment at 200 °C. The f.c.c δ was the only hydride phase observed in the rim/blister structure. The conventional Rietveld refinement was applied to measure the macro-strain equivalent response of the three phases. Two regions were delineated in the applied load versus lattice strain measurement: a linear elastic strain region and region that exhibited load partitioning. Load partitioning was quantified by von Mises analysis. The three phases were observed to have similar elastic modulus at 200 °C.

  10. Phase transitions

    CERN Document Server

    Solé, Ricard V

    2011-01-01

    Phase transitions--changes between different states of organization in a complex system--have long helped to explain physics concepts, such as why water freezes into a solid or boils to become a gas. How might phase transitions shed light on important problems in biological and ecological complex systems? Exploring the origins and implications of sudden changes in nature and society, Phase Transitions examines different dynamical behaviors in a broad range of complex systems. Using a compelling set of examples, from gene networks and ant colonies to human language and the degradation o

  11. Thermodynamic assessment of the Fe-Hf binary system

    International Nuclear Information System (INIS)

    The Fe-Hf system was critically assessed by means of the Calphad approach. The solution phases (liquid, BCC, FCC and HCP) were described with the sublattice formalism and the excess model with the Redlich-Kister equation by imposing additional constraints to avoid the appearance of unwanted inverted miscibility gap in the liquid phase during the phase diagram calculation up to 6000 K. The λ sub-stoichiometric intermetallic compound, which melts congruently and has an homogeneity range, was treated as the usual C14 Laves phases, with the formula (Fe)0.6667(Hf,Fe)0.3333, by a two-sublattice model with Fe alone in the first sublattice and Fe and Hf in the second one. The others polytypes Fe2HfHT, Fe2HfLT as well as FeHf2 were treated as stoichiometric compounds. The calculated phase diagram and thermodynamic properties are in good agreement with the experimental data

  12. Venus Phasing.

    Science.gov (United States)

    Riddle, Bob

    1997-01-01

    Presents a science activity designed to introduce students to the geocentric and heliocentric models of the universe. Helps students discover why phase changes on Venus knocked Earth out of the center of the universe. (DKM)

  13. Phase field

    International Nuclear Information System (INIS)

    In this work, the phase-field method and its application to microstructure evolution in reactor fuel and clad are discussed. The examples highlight the capability of the phase-field method to capture evolution processes that are influenced by both thermal and elastic stress fields that are caused by microstructural changes in the solid-state. The challenges that need to be overcome before the technique can become predictive and material-specific are discussed. (authors)

  14. Kinetic and Microstructure of SiC Deposited from SiCl4-CH4-H2%SiC14-CH4-H2系统沉积碳化硅动力学与微结构

    Institute of Scientific and Technical Information of China (English)

    杨艳; 张伟刚

    2009-01-01

    Silicon carbide was prepared from SiCl4-CH4-H2 gaseous precursors by isothermal, isobaric chemical vapor deposition (CVD) at atmospheric pressure and temperatures ranging from 900 C to 1100 C. Kinetic studies showed that carbosilane of SiH2Cl2, SiHCl3 and SiCI2 formed from decomposition of SiCI4 and CH4 contributed to the deposition of hexangular facet and granular pebble structured SiC. An average apparent activation energy of 152 ldmol ' was determined. The overall CVD process was controlled not only by the surface reactions but also by complex gas phase reactions. The as-deposited thin film was characterized using scanning electron microscopy, X-ray diffraction and transmission electron microscopy, these analysis showed that the deposited thin film consisted of pure phase of the β-SiC, the growth morphology of β-SiC differs from hexangular facet to granular pebble structures, which varied with substrate length and CVD temperature.

  15. Phase Vocoder

    Directory of Open Access Journals (Sweden)

    J.L. Flanagan

    2013-08-01

    Full Text Available A vocoder technique is described in which speech signals are represented by their short-time phase and amplitude spectra. A complete transmission system utilizing this approach is simulated on a digital computer. The encoding method leads to an economy in transmission bandwidth and to a means for time compression and expansion of speech signals.

  16. Phase diagrams

    International Nuclear Information System (INIS)

    The description is presented of binary phase diagrams of titanium alloyed with the following elements: silver, aluminium, arsenic, gold, boron, barium, beryllium, bismuth, carbon, calcium, cadmium, cobalt, chromium, copper, iron, gallium, germanium, hydrogen, hafnium, indium, iridium, potassium, lithium, magnesium, manganese, molybdenum, nitrogen, sodium, niobium, nickel, oxygen, osmium, phosphorus, lead, palladium, platinum, plutonium, rhenium, lanthanium, cerium, preseodymium, neodymium, gadolinium, erbium, terbium, thulium, lutetium, rhodium, ruthenium, scandium, silicon, tin, strontium, tantalum, technetium, thorium, uranium, vanadium, tungsten, yttrium, ytterbium, zinc and zirconium

  17. Mechanisms of improving the cyclic stability of V-Ti-based hydrogen storage electrode alloys

    International Nuclear Information System (INIS)

    Research highlights: → The corrosion resistance of V-based phase is much lower than that of C14 Laves phase of V-Ti-based alloys. → The addition of Cr which mostly distributes in V-based phase can effectively increase the anti-corrosion ability of V-Ti-based alloys. → The addition of Cr which mostly distributes in V-based phase can effectively increase the anti-corrosion ability of V-Ti-based alloys. - Abstract: In this work, the mechanisms of improving the cyclic stability of V-Ti-based hydrogen storage electrode alloys were investigated systemically. Several key factors for example corrosion resistance, pulverization resistance and oxidation resistance were evaluated individually. The V-based solid solution phase has much lower anti-corrosion ability than C14 Laves phase in KOH solution, and the addition of Cr in V-Ti-based alloys can suppress the dissolution of the main hydrogen absorption elements of the V-based phase in the alkaline solution. During the charge/discharge cycling, the alloy particles crack or break into several pieces, which accelerates their corrosion/oxidation and increases the contact resistance of the alloy electrodes. Proper decreasing the Vickers hardness and enhancing the fracture toughness can increase the pulverization resistance of the alloy particles. The oxidation layer thickness on the alloy particle surface obviously increases during charge/discharge cycling. This deteriorates their electro-catalyst activation to the electrochemical reaction, and leads to a quick degradation. Therefore, enhancing the oxide resistance can obviously improve the cyclic stability of V-Ti-based hydrogen storage electrode alloys.

  18. NiAl-based Polyphase in situ Composites in the NiAl-Ta-X (X = Cr, Mo, or V) Systems

    Science.gov (United States)

    Johnson, D. R.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

    1995-01-01

    Polyphase in situ composites were generated by directional solidification of ternary eutectics. This work was performed to discover if a balance of properties could be produced by combining the NiAl-Laves phase and the NiAl-refractory metal phase eutectics. The systems investigated were the Ni-Al-Ta-X (X = Cr, Mo, or V) alloys. Ternary eutectics were found in each of these systems and the eutectic composition, temperature, and morphology were determined. The ternary eutectic systems examined were the NiAl-NiAlTa-(Mo, Ta), NiAl-(Cr, Al) NiTa-Cr, and the NiAl-NiAlTa-V systems. Each eutectic consists of NiAl, a C14 Laves phase, and a refractory metal phase. Directional solidification was performed by containerless processing techniques in a levitation zone refiner to minimize alloy contamination. Room temperature fracture toughness of these materials was determined by a four-point bend test. Preliminary creep behavior was determined by compression tests at elevated temperatures, 1100-l400 K. Of the ternary eutectics, the one in the NiAl-Ta-Cr system was found to be the most promising. The fracture toughness of the NiAl-(Cr, Al)NiTa-Cr eutectic was intermediate between the values of the NiAl-NiAlTa eutectic and the NiAl-Cr eutectic. The creep strength of this ternary eutectic was similar to or greater than that of the NiAl-Cr eutectic.

  19. Phase Structural Characteristics of ZrV2 Thin Film Prepared by Magnetron Sputtering

    Institute of Scientific and Technical Information of China (English)

    XU Shi-Lin; SHI Li-Qun

    2005-01-01

    @@ The thin film metal hydride has become an emerging field of research in metal hydride batteries for its good mechanical and hydrogenation properties. ZrV2 thin films have been prepared using a dc magnetron sputtering method, and the phase structure is investigated. Only amorphous or crystalline Zr and V mixture phases are achieved when substrates are heated during either to 400℃ or to 550 ℃. The annealing causes segregation of Zr and V in the film induced by strain-driven diffusion and interdiffusion between substrate Mo and film elements at high temperature, which results in the formation of mixture phases of C14, C15, Zr and V, but the content of C15 phase is not higher compared with that in the bulk material.

  20. Topologically close-packed phases in binary transition-metal compounds: matching high-throughput ab initio calculations to an empirical structure map

    International Nuclear Information System (INIS)

    In steels and single-crystal superalloys the control of the formation of topologically close-packed (TCP) phases is critical for the performance of the material. The structural stability of TCP phases in multi-component transition-metal alloys may be rationalized in terms of the average valence-electron count N-bar and the composition-dependent relative volume-difference ΔV/V-bar . We elucidate the interplay of these factors by comparing density-functional theory calculations to an empirical structure map based on experimental data. In particular, we calculate the heat of formation for the TCP phases A15, C14, C15, C36, χ, μ and σ for all possible binary occupations of the Wyckoff positions. We discuss the isovalent systems V/Nb–Ta to highlight the role of atomic-size difference and observe the expected stabilization of C14/C15/C36/μ by ΔV/V-bar at ΔN = 0 in V–Ta. In the systems V/Nb–Re, we focus on the well-known trend of A15 → σ → χ stability with increasing N-bar and show that the influence of ΔV/V-bar is too weak to stabilize C14/C15/C36/μ in Nb–Re. As an example for a significant influence of both N-bar and ΔV/V-bar , we also consider the systems Cr/Mo–Co. Here the sequence A15 → σ → χ is observed in both systems but in Mo–Co the large size-mismatch stabilizes C14/C15/C36/μ. We also include V/Nb–Co that cover the entire valence range of TCP stability and also show the stabilization of C14/C15/C36/μ. Moreover, the combination of a large volume-difference with a large mismatch in valence-electron count reduces the stability of the A15/σ/χ phases in Nb–Co as compared to V–Co. By comparison to non-magnetic calculations we also find that magnetism is of minor importance for the structural stability of TCP phases in Cr/Mo–Co and in V/Nb–Co. (paper)

  1. New roles for icosahedral clusters in intermetallic phases: micelle-like segregation of Ca-Cd and Cu-Cd interactions in Ca10Cd27Cu2.

    Science.gov (United States)

    Hadler, Amelia B; Harris, Nicholas A; Fredrickson, Daniel C

    2013-11-20

    Despite significant progress in the structural characterization of the quasicrystalline state, the chemical origins of long- and short-range icosahedral order remain mysterious and a subject of debate. In this Article, we present the crystal structure of a new complex intermetallic phase, Ca10Cd27Cu2 (mC234.24), whose geometrical features offer clues to the driving forces underlying the icosahedral clusters that occur in Bergman-type quasicrystals. Ca10Cd27Cu2 adopts a C-centered monoclinic superstructure of the 1/1 Bergman approximant structure, in which [110] layers of Bergman clusters in the 1/1 structure are separated through the insertion of additional atoms (accompanied by substantial positional disorder). An examination of the coordination environments of Ca and Cu (in the ordered regions) reveals that the structure can be viewed as a combination of coordination polyhedra present in the nearest binary phases in the Ca-Cd-Cu compositional space. A notable feature is the separation of Ca-Cd and Cu-Cd interactions, with Bergman clusters emerging as Ca-Cd Friauf polyhedra (derived from the MgZn2-type CaCd2 phase) encapsulate a Cu-Cd icosahedron similar to those appearing in Cu2Cd5. DFT chemical pressure calculations on nearby binary phases point to the importance of this segregation of Ca-Cd and Cu-Cd interactions. The mismatch in atomic size between Cu and Cd leads to an inability to satisfy Ca-Cu and Ca-Cd interactions simultaneously in the Friauf polyhedra of the nearby Laves phase CaCd2. The relegation of the Cu atoms to icosahedra prevents this frustration while nucleating the formation of Bergman clusters. PMID:24147875

  2. Experimental investigation of the U–Zr–Al ternary phase diagram: Isothermal sections at 673 K and 1073 K

    Energy Technology Data Exchange (ETDEWEB)

    Moussa, C.; Désévédavy, F.; Noël, H.; Pasturel, M.; Gouttefangeas, F. [ISCR/CSM, Université de Rennes1, UMR-CNRS 6226, Campus de Beaulieu, 263 Avenue du Général Leclerc, 35042 Rennes Cedex, France, (France); Dubois, S. [CEA/DEN/DEC, Cadarache, 13108 St. Paul Lez Durance (France); Stepnik, B. [AREVA/CERCA, 10 Rue Juliette Récamier, 69006 Lyon (France); Tougait, O., E-mail: tougait@univ-rennes1.fr [ISCR/CSM, Université de Rennes1, UMR-CNRS 6226, Campus de Beaulieu, 263 Avenue du Général Leclerc, 35042 Rennes Cedex, France, (France); UCCS, UMR 8181 CNRS, Université Lille 1, ENSCL, Avenue Mendeleiev, 59655 Villeneuve d’Ascq Cedex (France)

    2015-06-15

    Highlights: • Isothermal sections of the U–Zr–Al system were investigated for 673 K and 1073 K. • The crystallographic properties of the equilibrium phases were checked. • The ternary extension of both unary and binary phases was determined. • The solubility of Al into UZr{sub 2} (δ-phase) was assessed by diffusion couples. • The microstructure of quenched alloys is discussed. - Abstract: Isothermal sections at 673 K and 1073 K of the ternary U–Zr–Al system were established in the whole concentration range, by means of powder X-ray diffraction, scanning electron microscopy–energy dispersive X-ray spectroscopy and differential thermal analysis. All measured compositions and unit-cell refinements were performed at room temperature from quenched samples annealed at 1073 K and 673 K for four and eight weeks respectively. For both temperatures, the Al-rich corner of the phase diagram is characterized by extended homogeneity ranges due to mutual exchange between U and Zr in UAl{sub 3} (cubic, AuCu{sub 3}-type) and in the Laves phase UAl{sub 2} (cubic, MgCu{sub 2}-type). Minute U solubility in ZrAl{sub 2} (hexagonal, MgZn{sub 2}-type) and in Zr{sub 2}Al (hexagonal, Ni{sub 2}In-type) was evaluated to be of the order of 1 at.% U. For the other binary compounds, the solubility of the third component was found negligible. At 1073 K, the solid solution based on γU (cubic, W-type) which covers the U–Zr binary axis up to 95.5 at.% Zr, allows also some limited solubility of Al [maximum of 5 at.%]. For Al-content below 66 at.%, most of the phase relations comprise equilibria between the Zr–Al binaries and the γ(U,Zr,Al) solid solution. At 673 K, the U–Zr axis is found in agreement with the literature data and no Al solubility could be detected in αU, αZr and UZr{sub 2} (δ phase). The phase relations are mainly established between Zr–Al binaries and αU. For monolithic UMo fuel with a Zr diffusion barrier foil cladded with Al, the main interaction

  3. Experimental investigation of the U–Zr–Al ternary phase diagram: Isothermal sections at 673 K and 1073 K

    International Nuclear Information System (INIS)

    Highlights: • Isothermal sections of the U–Zr–Al system were investigated for 673 K and 1073 K. • The crystallographic properties of the equilibrium phases were checked. • The ternary extension of both unary and binary phases was determined. • The solubility of Al into UZr2 (δ-phase) was assessed by diffusion couples. • The microstructure of quenched alloys is discussed. - Abstract: Isothermal sections at 673 K and 1073 K of the ternary U–Zr–Al system were established in the whole concentration range, by means of powder X-ray diffraction, scanning electron microscopy–energy dispersive X-ray spectroscopy and differential thermal analysis. All measured compositions and unit-cell refinements were performed at room temperature from quenched samples annealed at 1073 K and 673 K for four and eight weeks respectively. For both temperatures, the Al-rich corner of the phase diagram is characterized by extended homogeneity ranges due to mutual exchange between U and Zr in UAl3 (cubic, AuCu3-type) and in the Laves phase UAl2 (cubic, MgCu2-type). Minute U solubility in ZrAl2 (hexagonal, MgZn2-type) and in Zr2Al (hexagonal, Ni2In-type) was evaluated to be of the order of 1 at.% U. For the other binary compounds, the solubility of the third component was found negligible. At 1073 K, the solid solution based on γU (cubic, W-type) which covers the U–Zr binary axis up to 95.5 at.% Zr, allows also some limited solubility of Al [maximum of 5 at.%]. For Al-content below 66 at.%, most of the phase relations comprise equilibria between the Zr–Al binaries and the γ(U,Zr,Al) solid solution. At 673 K, the U–Zr axis is found in agreement with the literature data and no Al solubility could be detected in αU, αZr and UZr2 (δ phase). The phase relations are mainly established between Zr–Al binaries and αU. For monolithic UMo fuel with a Zr diffusion barrier foil cladded with Al, the main interaction product is expected to involve the U-based alloy with the

  4. Permanent magnetism of intermetallic compounds between light and heavy transition-metal elements

    International Nuclear Information System (INIS)

    First-principle calculations are used to investigate the intrinsic magnetic properties of intermetallic alloys of the type XMn, where X is a 4d or 5d element and M is Fe or Co. Emphasis is on the hexagonal C14 Laves-phase 1:2 and 1:5 alloys, the latter crystallizing in the CaCu5 structure. These series are of interest in permanent magnetism from fundamental and practical viewpoints, respectively. In the former, the unit cells form a prototypical motif where a heavy atom with high spin–orbit coupling and magnetocrystalline anisotropy is surrounded by many somewhat smaller M atoms with high magnetization, and the latter are Laves-phase derivatives of renewed interest in permanent magnetism. Our DFT calculations predict magnetic moments, magnetizations and anisotropies, as well as formation energies. The results are analyzed across the 4d and 5d series, especially with respect to hybridization effects between 3d and 4d/5d bands. (paper)

  5. Permanent magnetism of intermetallic compounds between light and heavy transition-metal elements

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, P; Kashyap, A; Balamurugan, B; Shield, JE; Sellmyer, DJ; Skomski, R

    2014-01-27

    First-principle calculations are used to investigate the intrinsic magnetic properties of intermetallic alloys of the type XMn, where X is a 4d or 5d element and M is Fe or Co. Emphasis is on the hexagonal C14 Laves-phase 1:2 and 1:5 alloys, the latter crystallizing in the CaCu5 structure. These series are of interest in permanent magnetism from fundamental and practical viewpoints, respectively. In the former, the unit cells form a prototypical motif where a heavy atom with high spin-orbit coupling and magnetocrystalline anisotropy is surrounded by many somewhat smaller M atoms with high magnetization, and the latter are Laves-phase derivatives of renewed interest in permanent magnetism. Our DFT calculations predict magnetic moments, magnetizations and anisotropies, as well as formation energies. The results are analyzed across the 4d and 5d series, especially with respect to hybridization effects between 3d and 4d/5d bands.

  6. Studies of Ti1.5Zr5.5V0.5(MxNi1-x)9.5 (M = Cr, Mn, Fe, Co, Cu, Al): Part 2. Hydrogen storage and electrochemical properties

    International Nuclear Information System (INIS)

    In Part 2 of this two part series of papers, the gas phase and electrochemical properties of the quinary alloy Ti1.5Zr5.5V0.5(MxNi1-x)9.5 with M = Cr, Mn, Fe, Co, Cu, or Al and x = 0.1 or 0.2 are studied and compared to the structural properties reported in Part 1. The electrochemical properties of the alloys are strongly related to the non-Laves phases. For example, the Zr7Ni10 phase provides a more catalytic surface and improves the high rate discharge capability of the alloy at the expense of discharge capacity due to the higher Ni to Zr ratio; the Zr9Ni11 phase, on the contrary, improves the discharge capacity but hinders the high rate discharge capability. In the Laves phases, C14 provides a stable hydride with lower equilibrium pressure, higher gas phase storage capacity and lower electrochemical rate capability. The C15 phase provides a less stable hydride with higher equilibrium pressure, lower gas phase storage capacity and higher electrochemical storage capacity. The main effect of each modifying element can be summarized as follows: Mn is the most beneficial substitution element found in this study. Mn increases both the gas phase and electrochemical capacities with good reversibility; it also improves the activation, hydrogen diffusion, surface reaction, and high rate discharge capability. Co increases the degree of disorder in the alloy, reduces both gas phase and electrochemical capacities, destabilizes the hydride, improves activation, and reduces surface reactivity. Fe decreases the gas phase capacity but improves the electrochemical discharge capacity. Fe facilities activation, but its surface reaction is the least active among the substituents used in this study. Al, Cr, and Cu are less desirable because they reduce: (1) the electrochemical and gas phase capacities, (2) the reversibility, and (3) the rate capability. They also slow activation.

  7. Hydrogen storage in TiCr1.2(FeV)x BCC solid solutions

    International Nuclear Information System (INIS)

    The Ti-V-based BCC solid solutions have been considered attractive candidates for hydrogen storage due to their relatively large hydrogen absorbing capacities near room temperature. In spite of this, improvements of some issues should be achieved to allow the technological applications of these alloys. Higher reversible hydrogen storage capacity, decreasing the hysteresis of PCI curves, and decrease in the cost of the raw materials are needed. In the case of vanadium-rich BCC solid solutions, which usually have large hydrogen storage capacities, the search for raw materials with lower cost is mandatory since pure vanadium is quite expensive. Recently, the substitutions of vanadium in these alloys have been tried and some interesting results were achieved by replacing vanadium by commercial ferrovanadium (FeV) alloy. In the present work, this approach was also adopted and TiCr1.2(FeV)x alloy series was investigated. The XRD patterns showed the co-existence of a BCC solid solution and a C14 Laves phase in these alloys. SEM analysis showed the alloys consisted of dendritic microstructure and C14 colonies. The amount of C14 phase increases when the amount of (FeV) decreases in these alloys. Concerning the hydrogen storage, the best results were obtained for the TiCr1.2(FeV)0.4 alloy, which achieved 2.79 mass% of hydrogen storage capacity and 1.36 mass% of reversible hydrogen storage capacity

  8. Hydrogen storage in TiCr{sub 1.2}(FeV){sub x} BCC solid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Sydney F. [Institut de Recherche sur l' hydrogene, Universite du Quebec a Trois-Rivieres 3351, Boul. des Forges, Trois-Rivieres, Quebec G9A 5H7 (Canada)], E-mail: sfsantos91@yahoo.com.br; Huot, Jacques [Institut de Recherche sur l' hydrogene, Universite du Quebec a Trois-Rivieres 3351, Boul. des Forges, Trois-Rivieres, Quebec G9A 5H7 (Canada)

    2009-03-20

    The Ti-V-based BCC solid solutions have been considered attractive candidates for hydrogen storage due to their relatively large hydrogen absorbing capacities near room temperature. In spite of this, improvements of some issues should be achieved to allow the technological applications of these alloys. Higher reversible hydrogen storage capacity, decreasing the hysteresis of PCI curves, and decrease in the cost of the raw materials are needed. In the case of vanadium-rich BCC solid solutions, which usually have large hydrogen storage capacities, the search for raw materials with lower cost is mandatory since pure vanadium is quite expensive. Recently, the substitutions of vanadium in these alloys have been tried and some interesting results were achieved by replacing vanadium by commercial ferrovanadium (FeV) alloy. In the present work, this approach was also adopted and TiCr{sub 1.2}(FeV){sub x} alloy series was investigated. The XRD patterns showed the co-existence of a BCC solid solution and a C14 Laves phase in these alloys. SEM analysis showed the alloys consisted of dendritic microstructure and C14 colonies. The amount of C14 phase increases when the amount of (FeV) decreases in these alloys. Concerning the hydrogen storage, the best results were obtained for the TiCr{sub 1.2}(FeV){sub 0.4} alloy, which achieved 2.79 mass% of hydrogen storage capacity and 1.36 mass% of reversible hydrogen storage capacity.

  9. Microscopic investigation of the 14C + 14C interactions

    International Nuclear Information System (INIS)

    In this communication, we show that a phenomenological imaginary part added to a nucleus-nucleus interaction calculated microscopically enables one to obtain quantitative agreement with experiment. (orig./HSI)

  10. ROOT 6 and beyond: TObject, C++14 and many cores.

    Science.gov (United States)

    Bellenot, B.; Canal, Ph; Couet, O.; Ganis, G.; Mato, P.; Moneta, L.; Naumann, A.; Piparo, D.

    2015-12-01

    Following the release of version 6, ROOT has entered a new area of development. It will leverage the industrial strength compiler library shipping in ROOT 6 and its support of the C++11/14 standard, to significantly simplify and harden ROOT's interfaces and to clarify and substantially improve ROOT's support for multi-threaded environments. This talk will also recap the most important new features and enhancements in ROOT in general, focusing on those allowed by the improved interpreter and better compiler support, including I/O for smart pointers, easier type safe access to the content of TTrees and enhanced multi processor support.

  11. THE NEW GRONINGEN C-14 DATA-BASE

    NARCIS (Netherlands)

    VANDERPLICHT, J

    1992-01-01

    The Groningen Radiocarbon Data base has been operating on an Apple IIe PC until recently. Both software and hardware of this data base made exchange with other systems very difficult. Therefore, the data base has been transferred to an IBM AT compatible computer. A new program has been written in Tu

  12. Phase contrast image synthesis

    DEFF Research Database (Denmark)

    Glückstad, J.

    1996-01-01

    A new method is presented for synthesizing arbitrary intensity patterns based on phase contrast imaging. The concept is grounded on an extension of the Zernike phase contrast method into the domain of full range [0; 2 pi] phase modulation. By controlling the average value of the input phase...... function and by choosing appropriate phase retardation at the phase contrast filter, a pure phase to intensity imaging is accomplished. The method presented is also directly applicable in dark field image synthesis....

  13. Phase contrast image synthesis

    DEFF Research Database (Denmark)

    Glückstad, J.

    A new method is presented for synthesizing arbitrary intensity patterns based on phase contrast imaging. The concept is grounded on an extension of the Zernike phase contrast method into the domain of full range [0; 2 pi] phase modulation. By controlling the average value of the input phase funct...... function and by choosing appropriate phase retardation at the phase contrast filter, a pure phase to intensity imaging is accomplished. The method presented is also directly applicable in dark field image synthesis....

  14. Effect of tempering treatment before aging on the microstructure and mechanical properties of ferritic heat-resistant steels

    International Nuclear Information System (INIS)

    This study investigated the effect of the tempering before aging on the precipitation of Laves phase and mechanical properties of 10Cr-6W and 10Cr-6W-3Co ferritic heat-resistant steels. Laves phase was precipitated by aging, which increased tensile strength but decreased elongation and impact value. Toughness was rapidly decreased by the presence of the very fine disk-like Laves phase precipitated at early aging stage. Strength and impact value were decreased by tempering treatment and that is due to the increase of the particle number per unite area and to larger particle size of Laves phase. Laves phase increased by adding Co, and consequently strength was increased and elongation and toughness were decreased

  15. Electron microscopy study of direct laser deposited IN718

    Energy Technology Data Exchange (ETDEWEB)

    Ding, R.G., E-mail: r.ding@bham.ac.uk [School of Metallurgy and Materials, The University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Huang, Z.W.; Li, H.Y. [School of Metallurgy and Materials, The University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Mitchell, I.; Baxter, G. [Rolls-Royce plc., Derby DE24 8BJ (United Kingdom); Bowen, P. [School of Metallurgy and Materials, The University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)

    2015-08-15

    The microstructure of direct laser deposited (DLD) IN718 has been investigated in detail using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results confirm that the dendrite core microstructure can be linked to the cooling rate experienced during the deposition. A ~ 100 μm wide δ partially dissolved region in the IN718 substrate was observed close to the substrate/deposit boundary. In the deposited IN718, γ/Laves eutectic constituent is the predominant minor microconstituent. Irregular and regular (small) (Nb,Ti)C carbides and a mixture of the carbides and Laves were observed. Most M{sub 3}B{sub 2} borides were nucleated around a (Nb,Ti)C carbide. Needles of δ phase precipitated from the Laves phase were also observed. A complex constituent (of Laves, δ, α-Cr, γ″, and γ matrix) is reported in IN718 for the first time. The formation of α-Cr particles could be related to Cr rejection during the formation and growth of Cr-depleted δ phase. - Highlights: • Secondary phases in IN718 deposits were identified using electron diffraction and EDS. • MC, M{sub 3}B{sub 2}, γ/Laves eutectic and γ/NbC/Laves eutectic were observed. • Needle-like δ phases were precipitated from the Laves phase. • A complex constituent (Laves, δ, α-Cr, γ″ and γ) was reported for the first time.

  16. Spin-glass behavior of Zr(Fe{sub x}Cr{sub 1-x}){sub 2} compounds

    Energy Technology Data Exchange (ETDEWEB)

    Coaquira, J.A.H. E-mail: coaquira@macbeth.if.usp.br; Rechenberg, H.R

    2001-05-01

    The magnetic properties of C14 Laves-phase Zr(Fe{sub x}Cr{sub 1-x}){sub 2} (0.7{<=}x{<=}0.85) alloys have been investigated. Arrott plots showed evidence of ferromagnetic ordering for alloys with x>0.7 but not for x=0.7. Zero field cooling/field cooling magnetization and Moessbauer spectroscopy data indicated spin-glass-like freezing for the sample with x=0.7 and a reentrant spin-glass behavior for samples with x>0.7. Dynamical behavior of the spin-glass sample (x=0.7) was studied by means of AC susceptibility. Two critical lines described by T{sub f}(H)-T(0){approx}H{sup 2/{delta}} were obtained with {delta}=4.4 and 2.5, respectively.

  17. Band structure and itinerant magnetism in quantum critical NbFe2

    Energy Technology Data Exchange (ETDEWEB)

    Subedi, A. P. [University of Tennessee, Knoxville (UTK); Singh, David J [ORNL

    2010-01-01

    We report first-principles calculations of the band structure and magnetic ordering in the C14 Laves phase compound NbFe{sub 2}. The magnetism is itinerant in the sense that the moments are highly dependent on ordering. We find an overestimation of the magnetic tendency within the local spin-density approximation, similar to other metals near magnetic quantum critical points. We also find a competition between different magnetic states due to band-structure effects. These lead to competing magnetic tendencies due to competing interlayer interactions, one favoring a ferrimagnetic solution and the other an antiferromagnetic state. While the structure contains Kagome lattice sheets, which could, in principle, lead to strong magnetic frustration, the calculations do not show dominant nearest-neighbor antiferromagnetic interactions within these sheets. These results are discussed in relation to experimental observations.

  18. Phase locked loop

    OpenAIRE

    Beek, van, P.; Klumperink, Eric Antonius Maria; Nauta, Bram; Vaucher, Cicero Silveira

    2007-01-01

    A phase locked loop comprising a phase detector ( 100 ) for determining a phase difference between a reference signal (Ref) and mutually phase shifted signals (I, Q) to generate frequency control signals (U, D), the phase detector ( 100 ) comprising: means ( 10 ) for obtaining a first one of said frequency control signals (U, D) by binary multiplication of the reference signal (Ref) and one of the relative phase shifted signals (I, Q); and means ( 20 ) for obtaining a second one of said frequ...

  19. Phase equilibrium engineering

    CERN Document Server

    Brignole, Esteban Alberto

    2013-01-01

    Traditionally, the teaching of phase equilibria emphasizes the relationships between the thermodynamic variables of each phase in equilibrium rather than its engineering applications. This book changes the focus from the use of thermodynamics relationships to compute phase equilibria to the design and control of the phase conditions that a process needs. Phase Equilibrium Engineering presents a systematic study and application of phase equilibrium tools to the development of chemical processes. The thermodynamic modeling of mixtures for process development, synthesis, simulation, design and

  20. Phase stability of V-Ta alloy using cluster expansion and Monte Carlo techniques

    International Nuclear Information System (INIS)

    Phase diagram of V-Ta alloy is studied by DFT total energy calculations combined with the cluster expansion (CE) and Monte Carlo techniques. In the CE method, the problem of computing the energies of the 2N possible configurations of a binary alloy is exactly mapped into a generalized Ising Hamiltonian: E(σ) = ΣαmαJαiϵσi>, where α is a cluster of atoms. The sum is over all clusters α that are not equivalent by a symmetry operation of the lattice, whereas the average is taken over all clusters β that are equivalent to α by symmetry. The coefficients Jα embody the energetics of the alloy and are the effective cluster interactions (ECI). These J's are determined from the energies of a small set of ordered configurations through a least-squares fit minimization. ATAT was used for constructing the CE and calculation of thermodynamic properties. Electronic structure calculations of ordered configurations, required for the construction of CE, are performed using VASP with GGA and PAW datasets. The free energies and phase boundaries of the alloy are calculated using Monte Carlo simulations in which the energetic is specified by the CE Hamiltonian. Our Monte Carlo simulation samples a semi-grand canonical ensemble in which the chemical potential and the temperature are specified externally. The composition is allowed to vary with the constraint of fixed total number of particles. Our CE of V-Ta alloy based on the bcc lattice includes 48 input structures, involves seven ECl, consisting of five pairs and an empty cluster and a point interaction, and samples all the configurations containing up to 12 atoms per unit cell. Nevertheless, our CE does not find any bee compound ground state, which is in agreement with experiment. Cluster expansion of V-Ta, based on the C15 Laves lattice establishes readily that V2Ta is the ground state composition. The phase boundaries computed using these two CE in the Monte Carlo simulations are, as shown in the figure, found to be in

  1. CrowdPhase: crowdsourcing the phase problem

    Energy Technology Data Exchange (ETDEWEB)

    Jorda, Julien; Sawaya, Michael R. [Institute for Genomics and Proteomics, 611 Charles Young Drive East, Los Angeles, CA 90095 (United States); Yeates, Todd O., E-mail: yeates@mbi.ucla.edu [Institute for Genomics and Proteomics, 611 Charles Young Drive East, Los Angeles, CA 90095 (United States); Molecular Biology Institute, 611 Charles Young Drive East, Los Angeles, CA 90095 (United States); University of California, 611 Charles Young Drive East, Los Angeles, CA 90095 (United States)

    2014-06-01

    The idea of attacking the phase problem by crowdsourcing is introduced. Using an interactive, multi-player, web-based system, participants work simultaneously to select phase sets that correspond to better electron-density maps in order to solve low-resolution phasing problems. The human mind innately excels at some complex tasks that are difficult to solve using computers alone. For complex problems amenable to parallelization, strategies can be developed to exploit human intelligence in a collective form: such approaches are sometimes referred to as ‘crowdsourcing’. Here, a first attempt at a crowdsourced approach for low-resolution ab initio phasing in macromolecular crystallography is proposed. A collaborative online game named CrowdPhase was designed, which relies on a human-powered genetic algorithm, where players control the selection mechanism during the evolutionary process. The algorithm starts from a population of ‘individuals’, each with a random genetic makeup, in this case a map prepared from a random set of phases, and tries to cause the population to evolve towards individuals with better phases based on Darwinian survival of the fittest. Players apply their pattern-recognition capabilities to evaluate the electron-density maps generated from these sets of phases and to select the fittest individuals. A user-friendly interface, a training stage and a competitive scoring system foster a network of well trained players who can guide the genetic algorithm towards better solutions from generation to generation via gameplay. CrowdPhase was applied to two synthetic low-resolution phasing puzzles and it was shown that players could successfully obtain phase sets in the 30° phase error range and corresponding molecular envelopes showing agreement with the low-resolution models. The successful preliminary studies suggest that with further development the crowdsourcing approach could fill a gap in current crystallographic methods by making it

  2. CrowdPhase: crowdsourcing the phase problem

    International Nuclear Information System (INIS)

    The idea of attacking the phase problem by crowdsourcing is introduced. Using an interactive, multi-player, web-based system, participants work simultaneously to select phase sets that correspond to better electron-density maps in order to solve low-resolution phasing problems. The human mind innately excels at some complex tasks that are difficult to solve using computers alone. For complex problems amenable to parallelization, strategies can be developed to exploit human intelligence in a collective form: such approaches are sometimes referred to as ‘crowdsourcing’. Here, a first attempt at a crowdsourced approach for low-resolution ab initio phasing in macromolecular crystallography is proposed. A collaborative online game named CrowdPhase was designed, which relies on a human-powered genetic algorithm, where players control the selection mechanism during the evolutionary process. The algorithm starts from a population of ‘individuals’, each with a random genetic makeup, in this case a map prepared from a random set of phases, and tries to cause the population to evolve towards individuals with better phases based on Darwinian survival of the fittest. Players apply their pattern-recognition capabilities to evaluate the electron-density maps generated from these sets of phases and to select the fittest individuals. A user-friendly interface, a training stage and a competitive scoring system foster a network of well trained players who can guide the genetic algorithm towards better solutions from generation to generation via gameplay. CrowdPhase was applied to two synthetic low-resolution phasing puzzles and it was shown that players could successfully obtain phase sets in the 30° phase error range and corresponding molecular envelopes showing agreement with the low-resolution models. The successful preliminary studies suggest that with further development the crowdsourcing approach could fill a gap in current crystallographic methods by making it

  3. Berry Phases and Quantum Phase Transitions

    CERN Document Server

    Hamma, A

    2006-01-01

    We study the connection between Berry phases and quantum phase transitions of generic quantum many-body systems. Consider sequences of Berry phases associated to sequences of loops in the parameter space whose limit is a point. If the sequence of Berry phases does not converge to zero, then the limit point is a quantum critical point. Quantum critical points are associated to failures of adiabaticity. We discuss the remarkable example of the anisotropic XY spin chain in a transverse magnetic field and detect the XX region of criticality.

  4. INTERGRANULAR PHASES IN ELECTROCERAMICS

    OpenAIRE

    Metz, R; Brieu, M.; Legros, R.; Rousset, A.

    1990-01-01

    The stability of the resistivity of N.T.C. thermistors is improved by the presence of precipitated phases in the vicinity of the spinel phase. The electron microscopy study allows one to make sure that the barium does not enter the spinel spinel structure but rather the grains of spinel phase are coated with insulating phase. It can be suggested that the insulating phase could built-up diffusion barriers.

  5. Hydrogen storage characteristics of Ti45Zr38Ni17−xCox (x = 4, 8) alloy and quasicrystal powders produced by mechanical alloying

    International Nuclear Information System (INIS)

    Highlights: •Ti–Zr–Ni–Co amorphous phase was formed directly by mechanical alloying. •Ti–Zr–Ni–Co quasicrystal phase was formed by subsequent annealing. •The hydrogen capacity at 573 K for the quasicrystal sample was about 58at%. •The quasicrystal samples transformed to several hydrides after hydrogenation. •The activation energies for hydrogen desorption were measured. -- Abstract: The effect of substitution of Co for Ni on hydrogen storage characteristics of Ti–Zr–Ni/Co powders (Ti45Zr38Ni17−xCox (x = 4, 8)) produced by mechanical alloying (MA) was investigated. The final product after MA was amorphous for all the powders, but subsequent annealing caused the formation of the icosahedral quasicrystal (i) phase with a Ti2Ni type crystal and a C14 like Laves phases. The amount of i-phase decreased, and reversely those of Ti2Ni and the Laves phases increased with increasing the amount of Co. After hydrogenation at 573 K and at an initial hydrogen pressure of 3.8 MPa, the maximum hydrogen concentration for the annealed powders reached was about 58 at%, and all the phases in the powders transformed to metallic hydrides ((Zr,Ti)H2, Ni(Zr,Ti)H3 and Co(Zr,Ti)H3). Because of the formation of several hydrides, accelerated hydrogen desorption occurred at several temperatures. The activation energies for hydrogen desorption varied from about 70 kJ/mol to 180 kJ/mol

  6. Industrialization of Polymer Solar Cells – phase 1

    OpenAIRE

    Lauritzen, Hanne; Bork, Jakob; Andersen, Rasmus B.; Bentzen, Barbara; Krebs, Frederik C.

    2012-01-01

    Plastsolceller har unikke egenskaber som lav vægt, lav tykkelse og mekanisk robusthed. Endvidere kan solcellens størrelse, form og krumning i stor udtrækning tilpasses dens anvendelse. Dette åbner for design af omkostnings- og energi-effektive anvendelser samt for æstetiske løsninger. Plastsolcellen fremstilles i en rulle-til-rulle proces, hvilket giver et stort potentiale med henblik på produktionsomkostninger i den helt lave ende ved høje produktionsvolumener. Dette gælder ikke kun for selv...

  7. Entropy Variation in the Two-dimensional Phase Transition of Anthracene Adsorbed at the Hg Electrode/Ethylene Glycol Solution Interface

    Directory of Open Access Journals (Sweden)

    Claudio Fontanesi

    2010-03-01

    Full Text Available The adsorption of anthracene (C14H10, at the mercury electrode/ethylene glycol (EG solution interface, is characterized by a low and almost constant capacity (about 8 μF cm−2 region (capacitive “pit” or “plateau” in capacity vs. potential curves, upon selection of suitable values of temperature, bulk concentration and applied potential values. This result is rationalized assuming the occurrence of a 2D phase transition between two distinct adsorbed phases: (i a “disordered” phase, characterized by a flat “parallel” disposition of the aromatic moiety on the electrode surface (ii an “ordered” phase, characterized by a “perpendicular” disposition of the aromatic moiety on the electrode surface. The experimental evidence is rationalized by considering the chemical potential as an explicit function of the “electric field/adsorbed molecule” interaction. Such a modelistic approach enables the determination of the relevant standard entropy variation.

  8. High temperature phase equilibria and phase diagrams

    CERN Document Server

    Kuo, Chu-Kun; Yan, Dong-Sheng

    2013-01-01

    High temperature phase equilibria studies play an increasingly important role in materials science and engineering. It is especially significant in the research into the properties of the material and the ways in which they can be improved. This is achieved by observing equilibrium and by examining the phase relationships at high temperature. The study of high temperature phase diagrams of nonmetallic systems began in the early 1900s when silica and mineral systems containing silica were focussed upon. Since then technical ceramics emerged and more emphasis has been placed on high temperature

  9. Simplified phase detector

    Science.gov (United States)

    Hershey, L. M.

    1979-01-01

    Tanlick sine-wave phase detector gives dc output voltage nearly proportional to phase difference between oscillator signal and reference signal. Device may be used for systems in which signal-to-noise ratio is high.

  10. Gas phase ion chemistry

    CERN Document Server

    Bowers, Michael T

    1979-01-01

    Gas Phase Ion Chemistry, Volume 2 covers the advances in gas phase ion chemistry. The book discusses the stabilities of positive ions from equilibrium gas-phase basicity measurements; the experimental methods used to determine molecular electron affinities, specifically photoelectron spectroscopy, photodetachment spectroscopy, charge transfer, and collisional ionization; and the gas-phase acidity scale. The text also describes the basis of the technique of chemical ionization mass spectrometry; the energetics and mechanisms of unimolecular reactions of positive ions; and the photodissociation

  11. Spectral phase conjugation via extended phase matching

    OpenAIRE

    Tsang, Mankei

    2005-01-01

    It is shown that the copropagating three-wave-mixing parametric process, with appropriate type-II extended phase matching and pumped with a short second-harmonic pulse, can perform spectral phase conjugation and parametric amplification, which shows a threshold behavior analogous to backward wave oscillation. The process is also analyzed in the Heisenberg picture, which predicts a spontaneous parametric down conversion rate in agreement with the experimental result reported by Kuzucu et al. [...

  12. Electrochemical and metallurgical characterization of ZrCr{sub 1-x}NiMo{sub x} AB{sub 2} metal hydride alloys

    Energy Technology Data Exchange (ETDEWEB)

    Erika, Teliz [Universidad de la República, Facultad de Ciencias, Laboratorio de Electroquímica Fundamental, Núcleo Interdisciplinario Ingeniería Electroquímica, Igua 4225, CP 11400 Montevideo (Uruguay); Ricardo, Faccio [Universidad de la República, Crystallography, Solid State and Materials Laboratory (Cryssmat-Lab), DETEMA, Centro NanoMat, Polo Tecnológico de Pando, Espacio Interdisciplinario, Facultad de Química, Montevideo (Uruguay); Fabricio, Ruiz [Consejo Nacional de Investigaciones Científicas y Técnicas , CONICET, Av. Rivadavia 1917, C1033AAJ Ciudad de Buenos Aires (Argentina); Centro Atómico Bariloche , Comisión Nacional de Energía Atómica (CAB-CNEA), Av. Bustillo 9500, CP 8400 S.C. de Bariloche, RN (Argentina); Fernando, Zinola [Universidad de la República, Facultad de Ciencias, Laboratorio de Electroquímica Fundamental, Núcleo Interdisciplinario Ingeniería Electroquímica, Igua 4225, CP 11400 Montevideo (Uruguay); and others

    2015-11-15

    The effects of partial replacement of chromium by molybdenum was studied on the structure and electrochemical kinetic properties of ZrCr{sub 1-x}NiMo{sub x}(x = 0.0, 0.3 and 0.6) metal hydride alloys. The arc-melting prepared alloys were metallurgically characterized by X-ray diffraction and energy dispersive spectroscopy microanalysis, which showed AB{sub 2} (with hexagonal C14 structure) and Zr{sub x}Ni{sub y} (Zr{sub 7}Ni{sub 10}, Zr{sub 9}Ni{sub 11}) phases. After a partial substitution of chromium by molybdenum, secondary phases monotonically increase with the C14 unit cell volume indicating that most of molybdenum atoms locate in the B-site. The alloys were electrochemically characterized using charge/discharge cycling, electrochemical impedance spectroscopy and rate capability experiments that allowed the determination of hydriding reaction kinetic parameters. The presence of molybdenum produces a positive effect for hydrogen diffusion in the alloy lattice, and ZrCr{sub 0.7}NiMo{sub 0.3} alloy depicts the better kinetics associated with a fast activation, lower charge transfer resistance and the best high rate discharge behavior. This fact would be related to a lower diffusion time constant and a bigger value of the product between exchange density current and surface active area. There is a trade-off in the amounts of secondary phase and Laves phases in order to improve the kinetic performance. - Highlights: • Metallurgical characterization evidences the presence of Zr{sub x}Ni{sub y} and C14 phases. • The partial replacement of Cr by Mo promotes the segregation of Zr{sub x}Ni{sub y} phase. • The incorporation of molybdenum improves the kinetics for the hydriding process. • Mo produces a decrease in the diffusion time constant.

  13. Electrochemical and metallurgical characterization of ZrCr1-xNiMox AB2 metal hydride alloys

    International Nuclear Information System (INIS)

    The effects of partial replacement of chromium by molybdenum was studied on the structure and electrochemical kinetic properties of ZrCr1-xNiMox(x = 0.0, 0.3 and 0.6) metal hydride alloys. The arc-melting prepared alloys were metallurgically characterized by X-ray diffraction and energy dispersive spectroscopy microanalysis, which showed AB2 (with hexagonal C14 structure) and ZrxNiy (Zr7Ni10, Zr9Ni11) phases. After a partial substitution of chromium by molybdenum, secondary phases monotonically increase with the C14 unit cell volume indicating that most of molybdenum atoms locate in the B-site. The alloys were electrochemically characterized using charge/discharge cycling, electrochemical impedance spectroscopy and rate capability experiments that allowed the determination of hydriding reaction kinetic parameters. The presence of molybdenum produces a positive effect for hydrogen diffusion in the alloy lattice, and ZrCr0.7NiMo0.3 alloy depicts the better kinetics associated with a fast activation, lower charge transfer resistance and the best high rate discharge behavior. This fact would be related to a lower diffusion time constant and a bigger value of the product between exchange density current and surface active area. There is a trade-off in the amounts of secondary phase and Laves phases in order to improve the kinetic performance. - Highlights: • Metallurgical characterization evidences the presence of ZrxNiy and C14 phases. • The partial replacement of Cr by Mo promotes the segregation of ZrxNiy phase. • The incorporation of molybdenum improves the kinetics for the hydriding process. • Mo produces a decrease in the diffusion time constant

  14. Generalized phase contrast:

    DEFF Research Database (Denmark)

    Glückstad, Jesper; Palima, Darwin

    (GPC) method including an overview of the range of current and potential applications of GPC in wavefront sensing and phase imaging, structured laser illumination and image projection, optical trapping and manipulation, and optical encryption and decryption. The GPC method goes further than the......Generalized Phase Contrast elevates the phase contrast technique not only to improve phase imaging but also to cross over and interface with diverse and seemingly disparate fields of contemporary optics and photonics. This book presents a comprehensive introduction to the Generalized Phase Contrast...

  15. Generalized Phase Contrast

    CERN Document Server

    Glückstad, Jesper

    2009-01-01

    Generalized Phase Contrast elevates the phase contrast technique not only to improve phase imaging but also to cross over and interface with diverse and seemingly disparate fields of contemporary optics and photonics. This book presents a comprehensive introduction to the Generalized Phase Contrast (GPC) method including an overview of the range of current and potential applications of GPC in wavefront sensing and phase imaging, structured laser illumination and image projection, optical trapping and manipulation, and optical encryption and decryption. The GPC method goes further than the restrictive assumptions of conventional Zernike phase contrast analysis and achieves an expanded range of validity beyond weak phase perturbations. The generalized analysis yields design criteria for tuning experimental parameters to achieve optimal performance in terms of accuracy, fidelity and light efficiency. Optimization can address practical issues, such as finding an optimal spatial filter for the chosen application, ...

  16. Morphology, deformation, and defect structures of TiCr2 in Ti-Cr alloys

    International Nuclear Information System (INIS)

    The morphologies and defect structures of TiCr2 in several Ti-Cr alloys have been examined by optical metallography, x-ray diffraction, and transmission electron microscopy (TEM), in order to explore the room-temperature deformability of the Laves phase TiCr2. The morphology of the Laves phase was found to be dependent upon alloy composition and annealing temperature. Samples deformed by compression have also been studied using TEM. Comparisons of microstructures before and after deformation suggest an increase in twin, stacking fault, and dislocation density within the Laves phase, indicating some but not extensive room-temperature deformability

  17. Gymnastics in Phase Space

    Energy Technology Data Exchange (ETDEWEB)

    Chao, Alexander Wu; /SLAC

    2012-03-01

    As accelerator technology advances, the requirements on accelerator beam quality become increasingly demanding. Facing these new demands, the topic of phase space gymnastics is becoming a new focus of accelerator physics R&D. In a phase space gymnastics, the beam's phase space distribution is manipulated and precision tailored to meet the required beam qualities. On the other hand, all realization of such gymnastics will have to obey accelerator physics principles as well as technological limitations. Recent examples of phase space gymnastics include Emittance exchanges, Phase space exchanges, Emittance partitioning, Seeded FELs and Microbunched beams. The emittance related topics of this list are reviewed in this report. The accelerator physics basis, the optics design principles that provide these phase space manipulations, and the possible applications of these gymnastics, are discussed. This fascinating new field promises to be a powerful tool of the future.

  18. Gymnastics in Phase Space

    International Nuclear Information System (INIS)

    As accelerator technology advances, the requirements on accelerator beam quality become increasingly demanding. Facing these new demands, the topic of phase space gymnastics is becoming a new focus of accelerator physics R and D. In a phase space gymnastics, the beam's phase space distribution is manipulated and precision tailored to meet the required beam qualities. On the other hand, all realization of such gymnastics will have to obey accelerator physics principles as well as technological limitations. Recent examples of phase space gymnastics include Emittance exchanges, Phase space exchanges, Emittance partitioning, Seeded FELs and Microbunched beams. The emittance related topics of this list are reviewed in this report. The accelerator physics basis, the optics design principles that provide these phase space manipulations, and the possible applications of these gymnastics, are discussed. This fascinating new field promises to be a powerful tool of the future.

  19. Cosmological phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Kolb, E.W. [Fermi National Accelerator Lab., Batavia, IL (United States)]|[Chicago Univ., IL (United States)

    1993-10-01

    If modern ideas about the role of spontaneous symmetry breaking in fundamental physics are correct, then the Universe should have undergone a series of phase transitions early in its history. The study of cosmological phase transitions has become an important aspect of early-Universe cosmology. In this lecture I review some very recent work on three aspects of phase transitions: the electroweak transition, texture, and axions.

  20. Phasing Into Retirement

    OpenAIRE

    Steven G. Allen; Clark, Robert L.; Linda S. Ghent

    2003-01-01

    To help workers navigate the transition from work to retirement more effectively, employers have been launching phased retirement programs, which allow older employees to work part-time and receive full retirement benefits. This paper examines the experience of the phased retirement system for tenured faculty in the University of North Carolina system over the years 1996-98. After phased retirement was introduced, there was a sizable increase in the overall separation rate in the system. The ...

  1. Cosmological phase transitions

    International Nuclear Information System (INIS)

    If modern ideas about the role of spontaneous symmetry breaking in fundamental physics are correct, then the Universe should have undergone a series of phase transitions early in its history. The study of cosmological phase transitions has become an important aspect of early-Universe cosmology. In this lecture I review some very recent work on three aspects of phase transitions: the electroweak transition, texture, and axions

  2. Super phase array

    Energy Technology Data Exchange (ETDEWEB)

    Wee, W H; Pendry, J B [Condensed Matter Theory Group Department of Physics Imperial College London London SW7 2AZ (United Kingdom)], E-mail: w.wee07@imperial.ac.uk

    2010-03-15

    For a long time phase arrays have been used in a variety of wave transmission applications because of their simplicity and versatility. Conventionally there is a trade-off between the compactness of a phase array and its directivity. In this paper we demonstrate how by embedding a normal phase array within a superlens (made of negative refractive index material) we can overcome this constraint and create compact phase arrays with a virtual extent much larger than the physical size of the array. In this paper we also briefly discuss the apparent unphysical field divergences in superlenses and how to resolve this issue.

  3. Super phase array

    International Nuclear Information System (INIS)

    For a long time phase arrays have been used in a variety of wave transmission applications because of their simplicity and versatility. Conventionally there is a trade-off between the compactness of a phase array and its directivity. In this paper we demonstrate how by embedding a normal phase array within a superlens (made of negative refractive index material) we can overcome this constraint and create compact phase arrays with a virtual extent much larger than the physical size of the array. In this paper we also briefly discuss the apparent unphysical field divergences in superlenses and how to resolve this issue.

  4. Solid phase transformations II

    CERN Document Server

    Čermák, J

    2009-01-01

    This topical volume includes ten invited papers that cover selected areas of the field of solid phase transformations. The first two contributions represent a burgeoning branch; that of the computer simulation of physical phenomena. The following three articles deal with the thermodynamics of phase transformations as a basic theory for describing the phenomenology of phase changes in matter. The next paper describes the interconnections between structural stability and the electronic structure of phases. Two further articles are devoted to displacive transformations; a field where there are ma

  5. Dual phase evolution

    CERN Document Server

    Green, David G; Abbass, Hussein A

    2014-01-01

    This book explains how dual phase evolution operates in all these settings and provides a detailed treatment of the subject. The authors discuss the theoretical foundations for the theory, how it relates to other phase transition phenomena and its advantages in evolutionary computation and complex adaptive systems. The book provides methods and techniques to use this concept for problem solving. Dual phase evolution concerns systems that evolve via repeated phase shifts in the connectivity of their elements. It occurs in vast range of settings, including natural systems (species evolution, landscape ecology, geomorphology), socio-economic systems (social networks) and in artificial systems (annealing, evolutionary computing).

  6. Dual Phase Cosmic Rays

    OpenAIRE

    Shurtleff, Richard

    2007-01-01

    A calculation based on flat spacetime symmetries shows how there can be two quantum phases. For one, extreme phase change determines a conventional classical trajectory and four-momentum, i.e. mass times four-velocity. The other phase occurs in an effective particle state, with the effective energy and momentum being the rate of change of the phase with respect to time and distance. A cosmic ray proton moves along a classical trajectory, but exists in an effective particle state with an effec...

  7. Phases of gauge theories

    International Nuclear Information System (INIS)

    One of the most fundamental questions we can ask about a given gauge theory is its phase diagram. In the Standard Model, we observe three fundamentally different types of behavior: QCD is in a confined phase at zero temperature, while the electroweak sector of the Standard Model combines Coulomb and Higgs phases. Our current understanding of the phase structure of gauge theories owes much to the modern theory of phase transitions and critical phenomena, but has developed into a subject of extensive study. After reviewing some fundamental concepts of phase transitions and finite-temperature gauge theories, we discuss some recent work that broadly extends our knowledge of the mechanisms that determine the phase structure of gauge theories. A new class of models with a rich phase structure has been discovered, generalizing our understanding of the confinement–deconfinement transition in finite-temperature gauge theories. Models in this class have spacetime topologies with one or more compact directions. On R3 × S1, the addition of double-trace deformations or periodic adjoint fermions to a gauge theory can yield a confined phase in the region where the S1 circumference L is small, so that the coupling constant is small, and semiclassical methods are applicable. In this region, Euclidean monopole solutions, which are constituents of finite-temperature instantons, play a crucial role in the calculation of a non-perturbative string tension. We review the techniques used to analyze this new class of models and the results obtained so far, as well as their application to finite-temperature phase structure, conformal phases of gauge theories and the large-N limit. (topical review)

  8. Pétrologie, géochronologie (K-Ar) et géochimie élémentaire et isotopique (Sr, Nd, Hf, Pb) de laves anciennes de la Réunion : Implications sur la construction de l’édifice volcanique

    OpenAIRE

    Smietana, Magali

    2011-01-01

    The volcanic system of La Reunion is made of the coalescent Piton des Neiges and Piton de la Fournaise edifices. Its formation, associated with the activity of a mantle plume, is characterized by phases of submarine and subaerial growth, followed by a period of destruction, as described in the classical model proposed for Hawaiian Island volcanoes. Previous studies showed that the subaerial activity of La Reunion would have started around 2.2 Ma ago. Geochemical analyses carried out on the pr...

  9. Phase ii Wage Controls

    Science.gov (United States)

    Mitchell, Daniel J. B.

    1974-01-01

    This study summarizes Phase ii Pay Board standards, assessing their effectiveness, and concluding that they had a significant impact on wage increases in new union agreements, less effect on deferred increases and nonunion wages, and little effect on aggregate income shares. The Phase ii experience can provide guidance for future control programs.…

  10. UPVG phase 2 report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-08-01

    The Utility PhotoVoltaic Group (UPVG), supported by member dues and a grant from the US Department of Energy, has as its mission the acceleration of the use of cost-effective small-scale and emerging large-scale applications of photovoltaics for the benefit of electric utilities and their customers. Formed in October, 1992, with the support of the American Public Power Association, Edison Electric Institute, and the National Rural Electric Cooperative Association, the UPVG currently has 90 members from all sectors of the electric utility industry. The UPVG`s efforts as conceived were divided into four phases: Phase 0--program plan; Phase 1--organization and strategy development; Phase 2--creating market assurance; and Phase 3--higher volume purchases. The Phase 0 effort developed the program plan and was completed early in 1993. The Phase 1 goal was to develop the necessary background information and analysis to lead to a decision as to which strategies could be undertaken by utilities to promote greater understanding of PV markets and achieve increased volumes of PV purchases. This report provides the details of the UPVG`s Phase 2 efforts to initiate TEAM-UP, its multiyear, 50-MW hardware initiative.

  11. Lunar Phases Planisphere

    Science.gov (United States)

    Shawl, Stephen J.

    2010-01-01

    This paper describes a lunar phases planisphere with which a user can answer questions about the rising and setting times of the Moon as well as questions about where the Moon will be at a given phase and time. The article contains figures that can be photocopied to make the planisphere. (Contains 2 figures.)

  12. Sampler bias -- Phase 1

    International Nuclear Information System (INIS)

    This documents Phase 1 determinations on sampler induced bias for four sampler types used in tank characterization. Each sampler, grab sampler or bottle-on-a-string, auger sampler, sludge sampler and universal sampler, is briefly discussed and their physical limits noted. Phase 2 of this document will define additional testing and analysis to further define Sampler Bias

  13. Templated blue phases.

    Science.gov (United States)

    Ravnik, Miha; Fukuda, Jun-ichi

    2015-11-21

    Cholesteric blue phases of a chiral liquid crystal are interesting examples of self-organised three-dimensional nanostructures formed by soft matter. Recently it was demonstrated that a polymer matrix introduced by photopolymerization inside a bulk blue phase not only stabilises the host blue phase significantly, but also serves as a template for blue phase ordering. We show with numerical modelling that the transfer of the orientational order of the blue phase to the surfaces of the polymer matrix, together with the resulting surface anchoring, can account for the templating behaviour of the polymer matrix inducing the blue phase ordering of an achiral nematic liquid crystal. Furthermore, tailoring the anchoring conditions of the polymer matrix surfaces can bring about orientational ordering different from those of bulk blue phases, including an intertwined complex of the polymer matrix and topological line defects of orientational order. Optical Kerr response of templated blue phases is explored, finding large Kerr constants in the range of K = 2-10 × 10(-9) m V(-2) and notable dependence on the surface anchoring strength. More generally, the presented numerical approach is aimed to clarify the role and actions of templating polymer matrices in complex chiral nematic fluids, and further to help design novel template-based materials from chiral liquid crystals. PMID:26412643

  14. Phases of cluster states

    International Nuclear Information System (INIS)

    The question of phases and phase transitions of cluster states is reviewed. First some features of the vibron model are recalled, then its extensions are investigated. Preliminary results are also presented from a study on the cluster-shell competition. (authors)

  15. Quantum phase transitions

    International Nuclear Information System (INIS)

    In recent years, quantum phase transitions have attracted the interest of both theorists and experimentalists in condensed matter physics. These transitions, which are accessed at zero temperature by variation of a non-thermal control parameter, can influence the behaviour of electronic systems over a wide range of the phase diagram. Quantum phase transitions occur as a result of competing ground state phases. The cuprate superconductors which can be tuned from a Mott insulating to a d-wave superconducting phase by carrier doping are a paradigmatic example. This review introduces important concepts of phase transitions and discusses the interplay of quantum and classical fluctuations near criticality. The main part of the article is devoted to bulk quantum phase transitions in condensed matter systems. Several classes of transitions will be briefly reviewed, pointing out, e.g., conceptual differences between ordering transitions in metallic and insulating systems. An interesting separate class of transitions is boundary phase transitions where only degrees of freedom of a subsystem become critical; this will be illustrated in a few examples. The article is aimed at bridging the gap between high-level theoretical presentations and research papers specialized in certain classes of materials. It will give an overview on a variety of different quantum transitions, critically discuss open theoretical questions, and frequently make contact with recent experiments in condensed matter physics

  16. UPVG phase 2 report

    International Nuclear Information System (INIS)

    The Utility PhotoVoltaic Group (UPVG), supported by member dues and a grant from the US Department of Energy, has as its mission the acceleration of the use of cost-effective small-scale and emerging large-scale applications of photovoltaics for the benefit of electric utilities and their customers. Formed in October, 1992, with the support of the American Public Power Association, Edison Electric Institute, and the National Rural Electric Cooperative Association, the UPVG currently has 90 members from all sectors of the electric utility industry. The UPVG's efforts as conceived were divided into four phases: Phase 0--program plan; Phase 1--organization and strategy development; Phase 2--creating market assurance; and Phase 3--higher volume purchases. The Phase 0 effort developed the program plan and was completed early in 1993. The Phase 1 goal was to develop the necessary background information and analysis to lead to a decision as to which strategies could be undertaken by utilities to promote greater understanding of PV markets and achieve increased volumes of PV purchases. This report provides the details of the UPVG's Phase 2 efforts to initiate TEAM-UP, its multiyear, 50-MW hardware initiative

  17. The vector resultant phase shifter

    International Nuclear Information System (INIS)

    A new type of voltage controlled phase shifter developed by HIRFL laboratory is better than mechanical phase shifter in all respects of performance, price, and reliability. It's principle is based on vector composition, so this new phase shifter is called vector resultant voltage controlled phase shifter. This new phase shifter has been applied in HIRFL phase stabilization system and satisfactory result has been obtained

  18. Quantum Enhanced Phase Retrieval

    CERN Document Server

    Liberman, Liat; Poem, Eilon; Silberberg, Yaron

    2015-01-01

    The retrieval of phases from intensity measurements is a key process in many fields in science, from optical microscopy to x-ray crystallography. Here we study phase retrieval of a one-dimensional multi-phase object that is illuminated by quantum states of light. We generalize the iterative Gerchberg-Saxton algorithm to photon correlation measurements on the output plane, rather than the standard intensity measurements. We report a numerical comparison of classical and quantum phase retrieval of a small one-dimensional object of discrete phases from its far-field diffraction. While the classical algorithm was ambiguous and often converged to wrong solutions, quantum light produced a unique reconstruction with smaller errors and faster convergence. We attribute these improvements to a larger Hilbert space that constrains the algorithm.

  19. Source Wavelet Phase Extraction

    Science.gov (United States)

    Naghadeh, Diako Hariri; Morley, Christopher Keith

    2016-06-01

    Extraction of propagation wavelet phase from seismic data can be conducted using first, second, third and fourth-order statistics. Three new methods are introduced, which are: (1) Combination of different moments, (2) Windowed continuous wavelet transform and (3) Maximum correlation with cosine function. To compare different methods synthetic data with and without noise were chosen. Results show that first, second and third order statistics are not able to preserve wavelet phase. Kurtosis can preserve propagation wavelet phase but signal-to-noise ratio can affect the extracted phase using this method. So for data set with low signal-to-noise ratio, it will be unstable. Using a combination of different moments to extract the phase is more robust than applying kurtosis. The improvement occurs because zero phase wavelets with reverse polarities have equal maximum kurtosis values hence the correct wavelet polarity cannot be identified. Zero-phase wavelets with reverse polarities have minimum and maximum values for a combination of different-moments method. These properties enable the technique to handle a finite data segment and to choose the correct wavelet polarity. Also, the existence of different moments can decrease sensitivity to outliers. A windowed continuous wavelet transform is more sensitive to signal-to-noise ratio than the combination of different-moments method, also if the scale for the wavelet is incorrect it will encounter with more problems to extract phase. When the effects of frequency bandwidth, signal-to-noise ratio and analyzing window length are considered, the results of extracting phase information from data without and with noise demonstrate that combination of different-moments is superior to the other methods introduced here.

  20. Atomic phase diagram

    Institute of Scientific and Technical Information of China (English)

    LI Shichun

    2004-01-01

    Based on the Thomas-Fermi-Dirac-Cheng model, atomic phase diagram or electron density versus atomic radius diagram describing the interaction properties of atoms of different kinds in equilibrium state is developed. Atomic phase diagram is established based on the two-atoms model. Besides atomic radius, electron density and continuity condition for electron density on interfaces between atoms, the lever law of atomic phase diagram involving other physical parameters is taken into account, such as the binding energy, for the sake of simplicity.

  1. Phase transformation and diffusion

    CERN Document Server

    Kale, G B; Dey, G K

    2008-01-01

    Given that the basic purpose of all research in materials science and technology is to tailor the properties of materials to suit specific applications, phase transformations are the natural key to the fine-tuning of the structural, mechanical and corrosion properties. A basic understanding of the kinetics and mechanisms of phase transformation is therefore of vital importance. Apart from a few cases involving crystallographic martensitic transformations, all phase transformations are mediated by diffusion. Thus, proper control and understanding of the process of diffusion during nucleation, g

  2. Dirac's Quantum Phase Problem

    OpenAIRE

    Sperling, J.; Vogel, W

    2009-01-01

    In 1927 the great physicist Paul A. M. Dirac failed to provide a consistent quantum description of the phase of a radiation field. Only one year later, he developed the famous Dirac theory of the electron, which led to the anti-particle -- the positron. We show that the reason for Dirac's failure with the phase problem bears a striking resemblance to his ingenious insight into the nature of the electron. For a correct quantum description of the phase of a radiation field it is necessary to ta...

  3. Martensitic phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Petry, W.; Neuhaus, J. [Techn. Universitaet Muenchen, Physik Department E13, Munich (Germany)

    1996-11-01

    Many elements transform from a high temperature bcc phase to a more dense packed temperature phase. The great majority of these transitions are of 1st order, displacive and reconstructive. The lattice potentials which govern these martensitic transitions can be probed by inelastic neutron scattering, thereby answering fundamental questions like : Will the transition be announced by dynamical or static fluctuations? What are the trajectories for the displacements needed for the transformation? Does the vibrational entropy stabilize the high temperature phase? Are the unusual transport properties in these materials related to their ability to transform? (author) 17 figs., 1 tab., 46 refs.

  4. Gas Phase Nanoparticle Synthesis

    Science.gov (United States)

    Granqvist, Claes; Kish, Laszlo; Marlow, William

    This book deals with gas-phase nanoparticle synthesis and is intended for researchers and research students in nanomaterials science and engineering, condensed matter physics and chemistry, and aerosol science. Gas-phase nanoparticle synthesis is instrumental to nanotechnology - a field in current focus that raises hopes for environmentally benign, resource-lean manufacturing. Nanoparticles can be produced by many physical, chemical, and even biological routes. Gas-phase synthesis is particularly interesting since one can achieve accurate manufacturing control and hence industrial viability.

  5. Phase transitions modern applications

    CERN Document Server

    Gitterman, Moshe

    2014-01-01

    This book provides a comprehensive review of the theory of phase transitions and its modern applications, based on the five pillars of the modern theory of phase transitions i.e. the Ising model, mean field, scaling, renormalization group and universality. This expanded second edition includes, along with a description of vortices and high temperature superconductivity, a discussion of phase transitions in chemical reaction and moving systems. The book covers a close connection between phase transitions and small world phenomena as well as scale-free systems such as the stock market and the Internet. Readership: Scientists working in different fields of physics, chemistry, biology and economics as well as teaching material for undergraduate and graduate courses.

  6. Now entering phase two...

    CERN Multimedia

    Katarina Anthony

    2012-01-01

    Building on the success of their feasibility phase, the CLIC test facility, CTF3, has just launched into a five-year project development phase. This will involve detailed performance optimisation studies, marking the project’s transition from pure research and development to prototyping and construction.   CLIC accelerator modules under construction at CERN. “With the feasibility phase now complete, we have established that CLIC can be built,” says Roberto Corsini, CLIC Collaboration spokesperson. “Now we want to be sure that it can provide the luminosity and energy performance needed. We will be looking at the engineering, performance and cost of a real CLIC machine also seeing if we can reduce it.” CTF3’s second phase will focus on selected performance-related research areas for further investigation. The largest of these involves the construction and testing of several authentic CLIC accelerator modules that are currently being ...

  7. Dual Phase Cosmic Rays

    CERN Document Server

    Shurtleff, Richard

    2008-01-01

    A calculation based on flat spacetime symmetries shows how there can be two quantum phases. For one, extreme phase change determines a conventional classical trajectory and four-momentum, i.e. mass times four-velocity. The other phase occurs in an effective particle state, with the effective energy and momentum being the rate of change of the phase with respect to time and distance. A cosmic ray proton moves along a classical trajectory, but exists in an effective particle state with an effective energy that depends on the local gravitational potential. Assumptions are made so that a cosmic ray proton in an ultra-high energy state detected near the Earth was in a much less energetic state in interstellar space. A 300 EeV proton incident on the Earth was a 2 PeV proton in interstellar space. The model predicts such protons are in states with even more energy near the Sun than when near the Earth.

  8. Dirac's Quantum Phase Problem

    CERN Document Server

    Sperling, J

    2009-01-01

    In 1927 the great physicist Paul A. M. Dirac failed to provide a consistent quantum description of the phase of a radiation field. Only one year later, he developed the famous Dirac theory of the electron, which led to the anti-particle -- the positron. We show that the reason for Dirac's failure with the phase problem bears a striking resemblance to his ingenious insight into the nature of the electron. For a correct quantum description of the phase of a radiation field it is necessary to take the polarisation into account. Similarly to the introduction of the anti-particle of the electron, the inclusion of the second polarisation resolves the inconsistency of the quantum phase problem. This also leads to new insight into the quantum measurement problem of time.

  9. FEL phased array configurations

    Science.gov (United States)

    Shellan, Jeffrey B.

    1986-01-01

    The advantages and disadvantages of various phased array and shared aperture concepts for FEL configurations are discussed. Consideration is given to the characteristics of intra- and inter-micropulse phasing; intra-macropulse phasing; an internal coupled resonator configuration; and an injection locked oscillator array. The use of a master oscillator power amplifier (MOPA) configuration with multiple or single master oscillators for FELs is examined. The venetian blind, rotating plate, single grating, and grating rhomb shared aperture concepts are analyzed. It is noted that the shared aperture approach using a grating rhomb and the MOPA concept with a single master oscillator and a coupled resonator are useful for FEL phased array configurations; and the MOPA concept is most applicable.

  10. Phase angle measurement techniques

    Energy Technology Data Exchange (ETDEWEB)

    Madge, R.; Fischer, D.

    1996-01-01

    Real-time measure of the power transfer across a transmission line was discussed. Phase angle measurement techniques, algorithms and applications relevant to power utilities were assessed. Phase-based applications compute the voltage angle difference between two stations, thereby allowing for power transfer calculations and power system control applications. A list of phase angle measurement applications was provided. It includes frequency measurement, state estimation, adaptive relaying, power system control, system restoration, real power flow monitoring and stability assessment, reactive power requirements monitoring, HVDC modulation, subsynchronous resonance, sequence of event recording, and loss reduction and fault location. The optimum timing requirement was determined for each application. Among the timing systems available today, the Global Positioning System (GPS), supported by powerful computers and other custom hardware, is the only tool that can provide the accuracy and coverage needed by today`s power system applications. Commercially available equipment for phase angle measurements was also reviewed. 30 refs., 32 tabs., 5 figs.

  11. The SAT phase transition

    Institute of Scientific and Technical Information of China (English)

    许可; 李未

    1999-01-01

    Phase transition is an important feature of SAT problem. For random k-SAT model, it is proved that as r(ratio of clauses to variables) increases, the structure of solutions will undergo a sudden change like satisfiability phase transition when r reaches a threshold point (r=rcr). This phenomenon shows that the satisfying truth assignments suddenly shift from being relatively different from each other to being very similar to each other.##属性不符

  12. Compressive Phase Contrast Tomography

    OpenAIRE

    Maia, F. R. N. C.; MacDowell, A.; Marchesini, S.; Padmore, H. A.; Parkinson, D. Y.; PIEN., J.; Schirotzek, A.; Yang, C

    2010-01-01

    When x-rays penetrate soft matter, their phase changes more rapidly than their amplitude. In- terference effects visible with high brightness sources creates higher contrast, edge enhanced images. When the object is piecewise smooth (made of big blocks of a few components), such higher con- trast datasets have a sparse solution. We apply basis pursuit solvers to improve SNR, remove ring artifacts, reduce the number of views and radiation dose from phase contrast datasets collected at the Hard...

  13. Compressive Phase Contrast Tomography

    OpenAIRE

    Maia, Filipe

    2010-01-01

    When x-rays penetrate soft matter, their phase changes more rapidly than their amplitude. Interference effects visible with high brightness sources creates higher contrast, edge enhanced images. When the object is piecewise smooth (made of big blocks of a few components), such higher contrast datasets have a sparse solution. We apply basis pursuit solvers to improve SNR, remove ring artifacts, reduce the number of views and radiation dose from phase contrast datasets collected at the Hard X-R...

  14. Kinetics of phase change

    OpenAIRE

    Faleiros A.C.; Rabelo T.N.; Thim G.P.; Oliveira M.A.S.

    2000-01-01

    The kinetic model for change of phases developed by M. Avrami at the end of the thirties has been used to describe the temporal behavior of phase changes. Until today this model is studied and adapted to include broader hypotheses. However, the mathematical format presented by M. Avrami is difficult to be understood by beginners. The purpose of this work is to clarify the mathematical treatment of Avrami's work, going straightforward to the arguments that led to his main results.

  15. Kinetics of phase change

    Directory of Open Access Journals (Sweden)

    A.C. Faleiros

    2000-07-01

    Full Text Available The kinetic model for change of phases developed by M. Avrami at the end of the thirties has been used to describe the temporal behavior of phase changes. Until today this model is studied and adapted to include broader hypotheses. However, the mathematical format presented by M. Avrami is difficult to be understood by beginners. The purpose of this work is to clarify the mathematical treatment of Avrami's work, going straightforward to the arguments that led to his main results.

  16. Efficient Bayesian Phase Estimation

    Science.gov (United States)

    Wiebe, Nathan; Granade, Chris

    2016-07-01

    We introduce a new method called rejection filtering that we use to perform adaptive Bayesian phase estimation. Our approach has several advantages: it is classically efficient, easy to implement, achieves Heisenberg limited scaling, resists depolarizing noise, tracks time-dependent eigenstates, recovers from failures, and can be run on a field programmable gate array. It also outperforms existing iterative phase estimation algorithms such as Kitaev's method.

  17. Two phase sampling

    CERN Document Server

    Ahmad, Zahoor; Hanif, Muhammad

    2013-01-01

    The development of estimators of population parameters based on two-phase sampling schemes has seen a dramatic increase in the past decade. Various authors have developed estimators of population using either one or two auxiliary variables. The present volume is a comprehensive collection of estimators available in single and two phase sampling. The book covers estimators which utilize information on single, two and multiple auxiliary variables of both quantitative and qualitative nature. Th...

  18. Faster Phase Estimation

    OpenAIRE

    Svore, Krysta M; Hastings, Matthew B.; Freedman, Michael

    2013-01-01

    We develop several algorithms for performing quantum phase estimation based on basic measurements and classical post-processing. We present a pedagogical review of quantum phase estimation and simulate the algorithm to numerically determine its scaling in circuit depth and width. We show that the use of purely random measurements requires a number of measurements that is optimal up to constant factors, albeit at the cost of exponential classical post-processing; the method can also be used to...

  19. Computing quantum phase transitions

    OpenAIRE

    Vojta, Thomas

    2007-01-01

    This article first gives a concise introduction to quantum phase transitions, emphasizing similarities with and differences to classical thermal transitions. After pointing out the computational challenges posed by quantum phase transitions, a number of successful computational approaches is discussed. The focus is on classical and quantum Monte Carlo methods, with the former being based on the quantum-to classical mapping while the latter directly attack the quantum problem. These methods ar...

  20. Quantitative phase spectroscopy

    OpenAIRE

    Rinehart, Matthew; Zhu, Yizheng; Wax, Adam

    2012-01-01

    Quantitative phase spectroscopy is presented as a novel method of measuring the wavelength-dependent refractive index of microscopic volumes. Light from a broadband source is filtered to an ~5 nm bandwidth and rapidly tuned across the visible spectrum in 1 nm increments by an acousto-optic tunable filter (AOTF). Quantitative phase images of semitransparent samples are recovered at each wavelength using off-axis interferometry and are processed to recover relative and absolute dispersion measu...

  1. Digital Receiver Phase Meter

    Science.gov (United States)

    Marcin, Martin; Abramovici, Alexander

    2008-01-01

    The software of a commercially available digital radio receiver has been modified to make the receiver function as a two-channel low-noise phase meter. This phase meter is a prototype in the continuing development of a phase meter for a system in which radiofrequency (RF) signals in the two channels would be outputs of a spaceborne heterodyne laser interferometer for detecting gravitational waves. The frequencies of the signals could include a common Doppler-shift component of as much as 15 MHz. The phase meter is required to measure the relative phases of the signals in the two channels at a sampling rate of 10 Hz at a root power spectral density digital receiver. The input RF signal is first fed to the input terminal of an analog-to-digital converter (ADC). To prevent aliasing errors in the ADC, the sampling rate must be at least twice the input signal frequency. The sampling rate of the ADC is governed by a sampling clock, which also drives a digital local oscillator (DLO), which is a direct digital frequency synthesizer. The DLO produces samples of sine and cosine signals at a programmed tuning frequency. The sine and cosine samples are mixed with (that is, multiplied by) the samples from the ADC, then low-pass filtered to obtain in-phase (I) and quadrature (Q) signal components. A digital signal processor (DSP) computes the ratio between the Q and I components, computes the phase of the RF signal (relative to that of the DLO signal) as the arctangent of this ratio, and then averages successive such phase values over a time interval specified by the user.

  2. Electron microscope phase enhancement

    Science.gov (United States)

    Jin, Jian; Glaeser, Robert M.

    2010-06-15

    A microfabricated electron phase shift element is used for modifying the phase characteristics of an electron beam passing though its center aperture, while not affecting the more divergent portion of an incident beam to selectively provide a ninety-degree phase shift to the unscattered beam in the back focal plan of the objective lens, in order to realize Zernike-type, in-focus phase contrast in an electron microscope. One application of the element is to increase the contrast of an electron microscope for viewing weakly scattering samples while in focus. Typical weakly scattering samples include biological samples such as macromolecules, or perhaps cells. Preliminary experimental images demonstrate that these devices do apply a ninety degree phase shift as expected. Electrostatic calculations have been used to determine that fringing fields in the region of the scattered electron beams will cause a negligible phase shift as long as the ratio of electrode length to the transverse feature-size aperture is about 5:1. Calculations are underway to determine the feasibility of aspect smaller aspect ratios of about 3:1 and about 2:1.

  3. Cosmological phase transitions

    International Nuclear Information System (INIS)

    If the universe stated from conditions of high temperature and density, there should have been a series of phase transitions associated with spontaneous symmetry breaking. The cosmological phase transitions could have observable consequences in the present Universe. Some of the consequences including the formation of topological defects and cosmological inflation are reviewed here. One of the most important tools in building particle physics models is the use of spontaneous symmetry breaking (SSB). The proposal that there are underlying symmetries of nature that are not manifest in the vacuum is a crucial link in the unification of forces. Of particular interest for cosmology is the expectation that are the high temperatures of the big bang symmetries broken today will be restored, and that there are phase transitions to the broken state. The possibility that topological defects will be produced in the transition is the subject of this section. The possibility that the Universe will undergo inflation in a phase transition will be the subject of the next section. Before discussing the creation of topological defects in the phase transition, some general aspects of high-temperature restoration of symmetry and the development of the phase transition will be reviewed. 29 references, 1 figure, 1 table

  4. Compressed sensing phase retrieval with phase diversity

    Science.gov (United States)

    Qin, Shun; Hu, Xinqi; Qin, Qiong

    2014-01-01

    The compressed sensing (CS) theory shows that sparse signal can be reconstructed accurately with some randomly observed measurements that are much fewer than what traditional method requires. Since it takes structure of signals into consideration, it has many advantages in the structured signals process. With CS, measuring can be speeded up and the cost of hardware can be decreased significantly. However, it faces great challenge in the amplitude-only measurement. In this article, we study the magnitude-only compressed sensing phase retrieval (CSPR) problem, and propose a practical recovery algorithm. In our algorithm, we introduce the powerful Hybrid-Input-Output algorithm with phase diversity to make our algorithm robust and efficient. A relaxed ℓ0 norm constrain is also introduced to help PR find a sparse solution with fewer measurements, which is demonstrated to be essential and effective to CSPR. We finally successfully apply it into complex-valued object recovery in THz imaging. The numerical results show that the proposed algorithm can recover the object pretty well with fewer measurements than what PR traditionally requires.

  5. The Importance of Rare-Earth Additions in Zr-Based AB2 Metal Hydride Alloys

    Directory of Open Access Journals (Sweden)

    Kwo-Hsiung Young

    2016-07-01

    Full Text Available Effects of substitutions of rare earth (RE elements (Y, La, Ce, and Nd to the Zr-based AB2 multi-phase metal hydride (MH alloys on the structure, gaseous phase hydrogen storage (H-storage, and electrochemical properties were studied and compared. Solubilities of the RE atoms in the main Laves phases (C14 and C15 are very low, and therefore the main contributions of the RE additives are through the formation of the RENi phase and change in TiNi phase abundance. Both the RENi and TiNi phases are found to facilitate the bulk diffusion of hydrogen but impede the surface reaction. The former is very effective in improving the activation behaviors. −40 °C performances of the Ce-doped alloys are slightly better than the Nd-doped alloys but not as good as those of the La-doped alloys, which gained the improvement through a different mechanism. While the improvement in ultra-low-temperature performance of the Ce-containing alloys can be associated with a larger amount of metallic Ni-clusters embedded in the surface oxide, the improvement in the La-containing alloys originates from the clean alloy/oxide interface as shown in an earlier transmission electron microscopy study. Overall, the substitution of 1 at% Ce to partially replace Zr gives the best electrochemical performances (capacity, rate, and activation and is recommended for all the AB2 MH alloys for electrochemical applications.

  6. Introduction to phasing

    International Nuclear Information System (INIS)

    This introductory paper to the CCP4 weekend on experimental phasing introduces the concept of the ‘phase problem’ for non-experts. Modern methods of phasing are explored, including some recent examples that can be downloaded as tutorials. When collecting X-ray diffraction data from a crystal, we measure the intensities of the diffracted waves scattered from a series of planes that we can imagine slicing through the crystal in all directions. From these intensities we derive the amplitudes of the scattered waves, but in the experiment we lose the phase information; that is, how we offset these waves when we add them together to reconstruct an image of our molecule. This is generally known as the ‘phase problem’. We can only derive the phases from some knowledge of the molecular structure. In small-molecule crystallography, some basic assumptions about atomicity give rise to relationships between the amplitudes from which phase information can be extracted. In protein crystallography, these ab initio methods can only be used in the rare cases in which there are data to at least 1.2 Å resolution. For the majority of cases in protein crystallography phases are derived either by using the atomic coordinates of a structurally similar protein (molecular replacement) or by finding the positions of heavy atoms that are intrinsic to the protein or that have been added (methods such as MIR, MIRAS, SIR, SIRAS, MAD, SAD or combinations of these). The pioneering work of Perutz, Kendrew, Blow, Crick and others developed the methods of isomorphous replacement: adding electron-dense atoms to the protein without disturbing the protein structure. Nowadays, methods from small-molecule crystallography can be used to find the heavy-atom substructure and the phases for the whole protein can be bootstrapped from this prior knowledge. More recently, improved X-ray sources, detectors and software have led to the routine use of anomalous scattering to obtain phase information from

  7. Crystal structure, phase transitions and ferroelastic properties of [(CH 3) 2NH 2] 3[Bi 2Cl 9

    Science.gov (United States)

    Wojtaś, M.; Bator, G.; Jakubas, R.; Zaleski, J.; Kosturek, B.; Baran, J.

    2003-07-01

    A sequence of structural phase transitions in [(CH 3) 2NH 2] 3[Bi 2Cl 9] (DMACB) is established on the basis of differential scanning calorimetry (DSC) and dilatometric studies. Four phase transitions are found: at 367/369, 340/341, 323/325 and 285/292 K (on cooling/heating). The crystal structure of DMACB is determined at 350 K. It crystallizes in monoclinic space group P2 1/ n: a=8.062(2), b=21.810(4), c=14.072(3) Å, β=92.63(3)°, Z=4, R1=0.0575, w R2=0.1486. The crystal is built of the double chain anions ("pleated ribbon structure") and the dimethylammonium cations. Dielectric studies in the frequency range 75 kHz-900 MHz indicate relatively fast reorientation of the dimethylammonium cations over the I, II, III and IV phases. Infrared spectra are recorded in the temperature range 40-300 K and analyzed in region assigned to the symmetric and asymmetric NC 2 stretching vibrations. Optical observations show the existence of the ferroelastic domain structure over all phases below 367 K. The possible mechanisms of phase transitions are discussed on the basis of presented results.

  8. Combustion 2000: Phase II

    Energy Technology Data Exchange (ETDEWEB)

    Unknown

    1999-11-01

    The goals of the program are to develop a coal-fired high performance power generation system (HIPPS) that is capable of: thermal efficiency (HHV) {ge} 47%; NOx, SOx, and particulates {le} 10% NSPS (New Source Performance Standard); coal providing {ge} 65% of heat input; all solid wastes benign; and cost of electricity {le} 90% of present plants. Phase 1, which began in 1992, focused on the analysis of various configurations of indirectly fired cycles and on technical assessments of alternative plant subsystems and components, including performance requirements, developmental status, design options, complexity and reliability, and capital and operating costs. Phase 1 also included preliminary R and D and the preparation of designs for HIPPS commercial plants approximately 300 MWe in size. This Phase, Phase 2, had as its initial objective the development of a complete design base for the construction and operation of a HIPPS prototype plant to be constructed in Phase 3. As part of a descoping initiative, the Phase 3 program has been eliminated and work related to the commercial plant design has been ended. The rescoped program retained a program of engineering research and development focusing on high temperature heat exchangers, e.g. HITAF development (Task 2); a rescoped Task 6 that is pertinent to Vision 21 objectives and focuses on advanced cycle analysis and optimization, integration of gas turbines into complex cycles, and repowering designs; and preparation of the Phase 2 Technical Report (Task 8). This rescoped program deleted all subsystem testing (Tasks 3, 4,and 5) and the development of a site-specific engineering design and test plan for the HIPPS prototype plant (Task 7). Work reported herein is from: Task 2.1 HITAF Combustors; Task 2.2 HITAF Air Heaters; and Task 6 HIPPS Commercial Plant Design Update.

  9. Optical Phase Imaging Using Synthetic Aperture Illumination and Phase Retrieval

    CERN Document Server

    Lee, Dennis J

    2016-01-01

    We perform quantitative phase imaging using phase retrieval to implement synthetic aperture imaging. Compared to digital holography, the developed technique is simpler, less expensive, and more stable.

  10. Single-phase to three-phase power conversion interface

    Science.gov (United States)

    Wu, Jinn-Chang; Wang, Yung-Shan; Jou, Hurng-Liahng; Lu, Wei-Tso

    2016-07-01

    This study proposes a single-phase to three-phase power conversion interface which converts the power from a single-phase utility to three-phase power for a three-phase load. The proposed single-phase to three-phase power conversion interface comprises a bridge-type switch set, a set of three-phase inductors, a transformer set and a set of three-phase capacitors. A current-mode control controls the switching of bridge-type switch set, to generate a set of nonzero-sequence (NZS) currents and a set of zero-sequence (ZS) currents. The transformer set is used to decouple the NZS currents and the ZS currents. The NZS currents are used to generate a high-quality three-phase voltage that supplies power to a three-phase load. The ZS currents flow to the single-phase utility so that the utility current is sinusoidal and in phase with the utility voltage. Accordingly, only a bridge-type switch set is used in the single-phase to three-phase power conversion interface to simply the power circuit. A prototype is developed and tested to verify the performance of the proposed single-phase to three-phase power conversion interface.

  11. Controllable tomography phase microscopy

    Science.gov (United States)

    Xiu, Peng; Zhou, Xin; Kuang, Cuifang; Xu, Yingke; Liu, Xu

    2015-03-01

    Tomography phase microscopy (TPM) is a new microscopic method that can quantitatively yield the volumetric 3D distribution of a sample's refractive index (RI), which is significant for cell biology research. In this paper, a controllable TPM system is introduced. In this system a circulatory phase-shifting method and piezoelectric ceramic are used which enable the TPM system to record the 3D RI distribution at a more controllable speed, from 1 to 40 fps, than in the other TPM systems reported. The resolution of the RI distribution obtained by this controllable TPM is much better than that in images recorded by phase contrast microscopy and interference tomography microscopy. The realization of controllable TPM not only allows for the application of TPM to the measurement of kinds of RI sample, but also contributes to academic and technological support for the practical use of TPM.

  12. Phase trombones with bending

    Energy Technology Data Exchange (ETDEWEB)

    Courant, E.D. [Brookhaven National Lab., Upton, NY (United States); Garren, A.

    1985-10-01

    The phase shifting trombones considered up to now for SSC application consisted of sets of evenly spaced quadrupoles separated by drift spaces. One such trombone was placed between a dispersion suppressor and a crossing insertion, so that the trombone had zero dispersion. With such trombones, it is possible to change {beta}{sup *} at constant tune, or to change the tunes by several units without altering the cell phase advances in the arcs. An objection to the above type of phase trombone is that it adds to the circumference, since no bending is included. This objection may or may not be valid depending on the potential usefulness of the drift spaces in them. In this note the authors show an alternative trombone design in which dipoles are included between the quadrupoles as in the normal arc cells. Since these trombones have dispersion, they are placed at the ends of the arcs, to be followed in turn by the dispersion suppressors and crossing insertions.

  13. Electroweak phase transitions

    International Nuclear Information System (INIS)

    An analytic treatment of the one Higgs doublet, electroweak phase transition is given. The phase transition is first order, occurs by the nucleation of thin walled bubbles and completes at a temperature where the order parameter, left-angle φ right-angle T is significantly smaller than it is when the origin becomes absolutely unstable. The rate of anomalous baryon number violation is an exponentially function of left-angle φ right-angle T. In very minimal extensions of the standard model it is quite easy to increase left-angle φ right-angle T so that anomalous baryon number violation is suppressed after completion of the phase transition. Hence baryogenesis at the electroweak phase transition is tenable in minimal of the standard model. In some cases additional phase transitions are possible. For a light Higgs boson, when the top quark mass is sufficiently large, the state where the Higgs field has a vacuum expectation value left-angle φ right-angle = 246 GeV is not the true minimum of the Higgs potential. When this is the case, and when the top quark mass exceeds some critical value, thermal fluctuations in the early universe would have rendered the state left-angle φ right-angle = 246 GeV unstable. The requirement that the state left-angle φ right-angle = 246 GeV is sufficiently long lived constrains the masses of the Higgs boson and the top quark. Finally, we consider whether local phase transitions can be induced by heavy particles which act as seeds for deformations in the scalar field

  14. Phase coexistence in nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Gulminelli, F

    2003-05-01

    In this work the general theory of first order phase transitions in finite systems is discussed, with a special emphasis to the conceptual problems linked to a thermodynamic description for small, short-lived systems de-exciting in the vacuum as nuclear samples coming from heavy ion collisions. After a short review of the general theory of phase transitions in the framework of information theory; we will present the different possible extensions to the field of finite systems. The concept of negative heat capacity, developed in the early seventies in the context of self-gravitating systems, will be reinterpreted in the general framework of convexity anomalies of thermo-statistical potentials. The connection with the distribution of the order parameter will lead us to a definition of first order phase transitions in finite systems based on topology anomalies of the event distribution in the space of observations. A careful study of the thermodynamic limit will provide a bridge with the standard theory of phase transitions and show that in a wide class of physical situations the different statistical ensembles are irreducibly inequivalent. In the second part of the paper we will apply the theoretical ideas developed in the first part to the possible observation of a liquid-to-gas-like phase transition in heavy ion collisions. The applicability of equilibrium concepts in a dynamical collisional process without boundary conditions will first be critically discussed. The observation of abnormally large partial energy fluctuations in carefully selected samples of collisions detected with the MULTICS-Miniball array will then be reported as a strong evidence of a first order phase transition with negative heat capacity in the nuclear equation of state. (author)

  15. Phase coexistence in nuclei

    International Nuclear Information System (INIS)

    In this work the general theory of first order phase transitions in finite systems is discussed, with a special emphasis to the conceptual problems linked to a thermodynamic description for small, short-lived systems de-exciting in the vacuum as nuclear samples coming from heavy ion collisions. After a short review of the general theory of phase transitions in the framework of information theory; we will present the different possible extensions to the field of finite systems. The concept of negative heat capacity, developed in the early seventies in the context of self-gravitating systems, will be reinterpreted in the general framework of convexity anomalies of thermo-statistical potentials. The connection with the distribution of the order parameter will lead us to a definition of first order phase transitions in finite systems based on topology anomalies of the event distribution in the space of observations. A careful study of the thermodynamic limit will provide a bridge with the standard theory of phase transitions and show that in a wide class of physical situations the different statistical ensembles are irreducibly inequivalent. In the second part of the paper we will apply the theoretical ideas developed in the first part to the possible observation of a liquid-to-gas-like phase transition in heavy ion collisions. The applicability of equilibrium concepts in a dynamical collisional process without boundary conditions will first be critically discussed. The observation of abnormally large partial energy fluctuations in carefully selected samples of collisions detected with the MULTICS-Miniball array will then be reported as a strong evidence of a first order phase transition with negative heat capacity in the nuclear equation of state. (author)

  16. Gas phase ion chemistry

    CERN Document Server

    Bowers, Michael T

    1979-01-01

    Gas Phase Ion Chemistry, Volume 1 covers papers on the advances of gas phase ion chemistry. The book discusses the advances in flow tubes and the measurement of ion-molecule rate coefficients and product distributions; the ion chemistry of the earth's atmosphere; and the classical ion-molecule collision theory. The text also describes statistical methods in reaction dynamics; the state selection by photoion-photoelectron coincidence; and the effects of temperature and pressure in the kinetics of ion-molecule reactions. The energy distribution in the unimolecular decomposition of ions, as well

  17. Phase Contrast Imaging

    DEFF Research Database (Denmark)

    1996-01-01

    The invention relates to a method and a system for synthesizing a prescribed intensity pattern based on phase contrast imaging that is not based on the assumption of prior art methods that the pahase shift phi is less than 1 radian. An improved method based on a simple imaging operation with a si......The invention relates to a method and a system for synthesizing a prescribed intensity pattern based on phase contrast imaging that is not based on the assumption of prior art methods that the pahase shift phi is less than 1 radian. An improved method based on a simple imaging operation...

  18. Compressive Phase Contrast Tomography

    CERN Document Server

    Maia, F R N C; Marchesini, S; Padmore, H A; Parkinson, D Y; Pien, J; Schirotzek, A; Yang, C; 10.1117/12.861946

    2010-01-01

    When x-rays penetrate soft matter, their phase changes more rapidly than their amplitude. In- terference effects visible with high brightness sources creates higher contrast, edge enhanced images. When the object is piecewise smooth (made of big blocks of a few components), such higher con- trast datasets have a sparse solution. We apply basis pursuit solvers to improve SNR, remove ring artifacts, reduce the number of views and radiation dose from phase contrast datasets collected at the Hard X-Ray Micro Tomography Beamline at the Advanced Light Source. We report a GPU code for the most computationally intensive task, the gridding and inverse gridding algorithm (non uniform sampled Fourier transform).

  19. Understanding quantum phase transitions

    CERN Document Server

    Carr, Lincoln

    2010-01-01

    Quantum phase transitions (QPTs) offer wonderful examples of the radical macroscopic effects inherent in quantum physics: phase changes between different forms of matter driven by quantum rather than thermal fluctuations, typically at very low temperatures. QPTs provide new insight into outstanding problems such as high-temperature superconductivity and display fundamental aspects of quantum theory, such as strong correlations and entanglement. Over the last two decades, our understanding of QPTs has increased tremendously due to a plethora of experimental examples, powerful new numerical meth

  20. Electronic phase transitions

    CERN Document Server

    Kopaev, YuV

    1992-01-01

    Electronic Phase Transitions deals with topics, which are presently at the forefront of scientific research in modern solid-state theory. Anderson localization, which has fundamental implications in many areas of solid-state physics as well as spin glasses, with its influence on quite different research activities such as neural networks, are two examples that are reviewed in this book. The ab initio statistical mechanics of structural phase transitions is another prime example, where the interplay and connection of two unrelated disciplines of solid-state theory - first principle ele

  1. Compressive Phase Contrast Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Maia, Filipe; MacDowell, Alastair; Marchesini, Stefano; Padmore, Howard A.; Parkinson, Dula Y.; Pien, Jack; Schirotzek, Andre; Yang, Chao

    2010-09-01

    When x-rays penetrate soft matter, their phase changes more rapidly than their amplitude. Interference effects visible with high brightness sources creates higher contrast, edge enhanced images. When the object is piecewise smooth (made of big blocks of a few components), such higher contrast datasets have a sparse solution. We apply basis pursuit solvers to improve SNR, remove ring artifacts, reduce the number of views and radiation dose from phase contrast datasets collected at the Hard X-Ray Micro Tomography Beamline at the Advanced Light Source. We report a GPU code for the most computationally intensive task, the gridding and inverse gridding algorithm (non uniform sampled Fourier transform).

  2. Solid phase transformations

    CERN Document Server

    Čermák, J

    2008-01-01

    This special-topic book, devoted to ""Solid Phase Transformations"" , covers a broad range of phenomena which are of importance in a number of technological processes. Most commercial alloys undergo thermal treatment after casting, with the aim of imparting desired compositions and/or optimal morphologies to the component phases. In spite of the fact that the topic has lain at the center of physical metallurgy for a long time, there are numerous aspects which are wide open to potential investigative breakthroughs. Materials with new structures also stimulate research in the field, as well as n

  3. Phase stability of V-Ta and Ti-Tm (Tm=V, Nb, Mo, Ta) alloys using cluster expansion and Monte Carlo simulation techniques

    International Nuclear Information System (INIS)

    Phase diagram of V-Ta alloy is studied by DFT total energy calculations combined with the cluster expansion (CE) and Monte Carlo (MC) simulation techniques. In the cluster expansion method, the problem of computing the energies of the 2N possible configurations of a binary alloy crystal with N lattice sites is exactly mapped into a generalized Ising Hamiltonian E(σ) = Σαmα/α(Πİ∈βσİ) where α is a cluster of atoms. The sum is over all clusters α that are not equivalent by a symmetry operation of the lattice, whereas the average is taken overall clusters β that are equivalent to α by symmetry. The coefficients Jα embody the energetics of the alloy and are called the effective cluster interactions (ECI). These J's are determined from the energies of a small set of ordered configurations through a least-squares fit minimization. Alloy Theory Automated Toolkit was used for constructing the CE and calculation of thermodynamic properties. Electronic structure calculations of ordered configurations, required for the construction of CE, are performed using VASP with PAW datasets and GGA. The free energies and phase boundaries of the alloy are calculated using MC simulations in which the energetics is specified by the CE Hamiltonian. The MC simulation samples a semi-grand canonical ensemble in which the chemical potential and the temperature are specified externally. The composition is allowed to vary with the constraint of fixed total number of particles. The CE of V-Ta alloy based on the bcc lattice includes 48 input structures, involves seven ECI, consisting of five pairs and an empty cluster and a point interaction, and samples all the configurations containing up to 12 atoms per unit cell. Nevertheless, the CE does not find any bcc compound ground state, which is in agreement with experiment. Cluster expansion of V-Ta, based on the C15 Laves lattice establishes readily that V2Ta is the ground state composition. The phase boundaries, computed using

  4. Comparison of three-phase modulation with two-phase and four-phase modulation

    Science.gov (United States)

    Pierce, J. R.

    1980-01-01

    For a constant added noise density at high signal-to-noise ratios and for the same error rate, three-phase PSK requires about 0.75 dB less energy per bit than two-phase or four-phase PSK. However, at very low signal-to-noise ratios, three-phase PSK requires about 0.74 dB more energy per bit of channel capacity than two-phase or four-phase PSK.

  5. Advanced Virgo phase cameras

    Science.gov (United States)

    van der Schaaf, L.; Agatsuma, K.; van Beuzekom, M.; Gebyehu, M.; van den Brand, J.

    2016-05-01

    A century after the prediction of gravitational waves, detectors have reached the sensitivity needed to proof their existence. One of them, the Virgo interferometer in Pisa, is presently being upgraded to Advanced Virgo (AdV) and will come into operation in 2016. The power stored in the interferometer arms raises from 20 to 700 kW. This increase is expected to introduce higher order modes in the beam, which could reduce the circulating power in the interferometer, limiting the sensitivity of the instrument. To suppress these higher-order modes, the core optics of Advanced Virgo is equipped with a thermal compensation system. Phase cameras, monitoring the real-time status of the beam constitute a critical component of this compensation system. These cameras measure the phases and amplitudes of the laser-light fields at the frequencies selected to control the interferometer. The measurement combines heterodyne detection with a scan of the wave front over a photodetector with pin-hole aperture. Three cameras observe the phase front of these laser sidebands. Two of them monitor the in-and output of the interferometer arms and the third one is used in the control of the aberrations introduced by the power recycling cavity. In this paper the working principle of the phase cameras is explained and some characteristic parameters are described.

  6. Temperature stabilized phase detector

    Science.gov (United States)

    Lo, Y.

    1981-01-01

    The construction, tests, and performance of a temperature stabilized phase detector are discussed. It has a frequency stability of 5 parts in 10 to the 16th power at 100 MHz, with a temperature step of 20 C (15 to 35 C).

  7. The geometric phase

    International Nuclear Information System (INIS)

    In 1983 the author found a geometric effect exists in the quantum waves that describe matter and its interactions on the smallest scales. In this case the anholonomy appears in a system's wave function (the mathematical description of a system's physical state) after the system has been transported around a cyclic circuit on an abstract surface in parameter space. He calls this anholonomy the geometric phase, because it manifests itself specifically as a shift in the wave function's phase: a quantity that describes where the wave function is in its oscillatory cycle at any given time and place. It so happens that the geometric phase provides an elegant explanation of various quantum-mechanical phenomena in systems whose environment undergoes a cyclic change: neutrons that pass through a helical magnetic field, polarized light in a coiled optic fiber and charged particles circling an isolated magnetic field. Perhaps more surprising is the fact that the geometric phase can also be generalized to applications in classical physics. Among other things, it offers a new way to describe the behavior of such textbook objects as pendulums

  8. Photoinduced phase transitions

    CERN Document Server

    Nasu, K

    2004-01-01

    A new class of insulating solids was recently discovered. Whenirradiated by a few visible photons, these solids give rise to amacroscopic excited domain that has new structural and electronicorders quite different from the starting ground state. This occurrenceis called "photoinduced phase transition", and this multi-authoredbook reviews recent theoretical and experimental studies of this newphenomenon.

  9. Noise and Phase Transitions

    Science.gov (United States)

    Chen, Zhi; Yu, Clare C.

    2006-03-01

    Noise is present in many physical systems and is often viewed as a nuisance. Yet it can also be a probe of microscopic fluctuations. There have been indications recently that the noise in the resistivity increases in the vicinity of the metal-insulator transition. But what are the characteristics of the noise associated with well-understood first and second order phase transitions? It is well known that critical fluctuations are associated with second order phase transitions, but do these fluctuations lead to enhanced noise? We have addressed these questions using Monte Carlo simulations to study the noise in the 2D Ising model which undergoes a second order phase transition, and in the 5-state Potts model which undergoes a first order phase transition. We monitor these systems as the temperature drops below the critical temperature. At each temperature, after equilibration is established, we obtain the time series of quantities characterizing the properties of the system, i.e., the energy and magnetization per site. We apply different methods, such as the noise power spectrum, the Detrended Fluctuation Analysis (DFA) and the second spectrum of the noise, to analyze the fluctuations in these quantities.

  10. Theory of alloy phases

    Energy Technology Data Exchange (ETDEWEB)

    Watson, R.E.; Ehrenreich, H.; Bennett, L.H.

    1977-01-01

    Various non-thermodynamic approaches to understanding and predicting phase diagrams are explored from the viewpoint of solid-state physics. The review is intended to indicate the scope of activity and some of the progress which has been made. (GHT)

  11. diffusive phase separation

    Directory of Open Access Journals (Sweden)

    Nobuyuki Kenmochi

    1996-01-01

    w is constrained to have double obstacles σ*≤w≤σ* (i.e., σ* and σ* are the threshold values of w. The objective of this paper is to discuss the semigroup {S(t} associated with the phase separation model, and construct its global attractor.

  12. SSIP Phase I Roadmap

    Science.gov (United States)

    Vinh, Megan; Lucas, Anne; Taylor, Cornelia; Kelley, Grace; Kasprzak, Christina

    2014-01-01

    This roadmap provides a description of the activities involved in the development of the State Systemic Improvement Plan (SSIP) (SPP/APR Indicators C11 and B17) due to the Office of Special Education Programs (OSEP) on April 1, 2015. The roadmap is intended to support states with completing Phase I of the SSIP process. This document provides…

  13. Fun with Phase Changes

    Science.gov (United States)

    Purvis, David

    2006-01-01

    A lot of good elementary science involves studying solids, liquids, and gases, and some inquiry-based activities that are easy to set up and do. In this article, the author presents activities pertaining to simple phase change. Using water as the example, these activities introduce upper-grade students to the idea of the arrangement of molecules…

  14. Rolling Cylinder Phase 1

    DEFF Research Database (Denmark)

    Margheritini, Lucia; Taraborrelli, Valeria Taraborrelli

    Margheritini and Valeria Taraborrelli(valeria.taraborrelli@hotmail.it) with a total of 3 day visit from the developers. Laboratory tests in irregular waves will be performed by Lucia Margheritini. The report is aimed at the first stage testing of the Rolling Cylinder wave energy device. This phase includes...

  15. Numerical modeling of microstructure evolution during laser additive manufacturing of a nickel-based superalloy

    International Nuclear Information System (INIS)

    A multi-scale model that combines the finite element method and stochastic analysis is developed to simulate the evolution of the microstructure of an Nb-bearing nickel-based superalloy during laser additive manufacturing solidification. Through the use of this model, the nucleation and growth of dendrites, the segregation of niobium (Nb) and the formation of Laves phase particles during the solidification are investigated to provide the relationship between the solidification conditions and the resultant microstructure, especially in the morphology of Laves phase particles. The study shows that small equiaxed dendrite arm spacing under a high cooling rate and low temperature gradient to growth rate (G/R) ratio is beneficial for forming discrete Laves phase particles. In contrast, large columnar dendrite arm spacing under a low cooling rate and high G/R ratio tends to produce continuously distributed coarse Laves phase particles, which are known to be detrimental to mechanical properties. In addition, the improvement of hot cracking resistance by controlling the morphology of Laves phase particles is discussed by analyzing the cracking pattern and microstructure in the laser deposited material. This work provides valuable understanding of solidification microstructure development in Nb-bearing nickel-based superalloys, like IN 718, during laser additive manufacturing and constitutes a fundamental basis for controlling the microstructure to minimize the formation of deleterious Laves phase particles

  16. Gouy phase compensation in quasi-phase matching

    OpenAIRE

    Major, Huw E.; Gawith, Corin B.E.; Smith, Peter G. R.

    2008-01-01

    In any focussed nonlinear interaction the focus induced phase shift, known as the Gouy phase shift, provides an imperfection in phase matching for any linearly invariant material. However, using an appropriately designed quasi-phase matched structure it is theoretically possible to compensate for the deleterious effects of the Gouy phase shift, allowing a symmetric frequency response and tighter optimal focussing than in a uniform material.

  17. Stochastic modelling of two-phase flows including phase change

    International Nuclear Information System (INIS)

    Stochastic modelling has already been developed and applied for single-phase flows and incompressible two-phase flows. In this article, we propose an extension of this modelling approach to two-phase flows including phase change (e.g. for steam-water flows). Two aspects are emphasised: a stochastic model accounting for phase transition and a modelling constraint which arises from volume conservation. To illustrate the whole approach, some remarks are eventually proposed for two-fluid models. (authors)

  18. Phase Operator and Phase State in Thermo Field Dynamics

    Science.gov (United States)

    Fan, Hong-Yi; Jiang, Nian-Quan

    We extend the Susskind-Glogower phase operator and phase state in quantum optics to thermo field dynamics (TFD). Based on the thermo entangled state representation, we introduce thermo excitation and de-excitation operators with which the phase operator and phase state in TFD can be constructed. The phase state treated as a limiting case of a new SU(1, 1) coherent states is also exhibited.

  19. Phase Computations and Phase Models for Discrete Molecular Oscillators.

    OpenAIRE

    Demir, Alper; Şuvak, Önder

    2012-01-01

    RESEARCH Open Access Phase computations and phase models for discrete molecular oscillators Onder Suvak* and Alper Demir Abstract Background: Biochemical oscillators perform crucial functions in cells, e.g., they set up circadian clocks. The dynamical behavior of oscillators is best described and analyzed in terms of the scalar quantity, phase. A rigorous and useful definition for phase is based on the so-called isochrons of oscillators. Phase computation techniques for ...

  20. Quantitative Phase Imaging Using Multi-Wavelength Optical Phase Unwrapping

    OpenAIRE

    Warnasooriya, Nilanthi; Kim, Myung K.

    2010-01-01

    In summary, this chpater demonstrates the effectiveness of the multi-wavelength optical unwrapping method. To our knowledge this is the first time that three wavelengths have been used in interferometry for phase unwrapping without increasing phase noise. Unlike conventional software phase unwrapping methods that fail when there is high phase noise and when there are irregularities in the object, the multi-wavelength optical phase unwrapping method can be used with any type of object. Softwar...

  1. Quantitative Phase Microscopy: how to make phase data meaningful

    OpenAIRE

    Goldstein, Goldie; Creath, Katherine

    2014-01-01

    The continued development of hardware and associated image processing techniques for quantitative phase microscopy has allowed superior phase data to be acquired that readily shows dynamic optical volume changes and enables particle tracking. Recent efforts have focused on tying phase data and associated metrics to cell morphology. One challenge in measuring biological objects using interferometrically obtained phase information is achieving consistent phase unwrapping and -dimensions and cor...

  2. Phase II Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Schuknecht, Nate [Project Manager; White, David [Principle Investigator; Hoste, Graeme [Research Engineer

    2014-09-11

    The SkyTrough DSP will advance the state-of-the-art in parabolic troughs for utility applications, with a larger aperture, higher operating temperature, and lower cost. The goal of this project was to develop a parabolic trough collector that enables solar electricity generation in the 2020 marketplace for a 216MWe nameplate baseload power plant. This plant requires an LCOE of 9¢/kWhe, given a capacity factor of 75%, a fossil fuel limit of 15%, a fossil fuel cost of $6.75/MMBtu, $25.00/kWht thermal storage cost, and a domestic installation corresponding to Daggett, CA. The result of our optimization was a trough design of larger aperture and operating temperature than has been fielded in large, utility scale parabolic trough applications: 7.6m width x 150m SCA length (1,118m2 aperture), with four 90mm diameter × 4.7m receivers per mirror module and an operating temperature of 500°C. The results from physical modeling in the System Advisory Model indicate that, for a capacity factor of 75%: The LCOE will be 8.87¢/kWhe. SkyFuel examined the design of almost every parabolic trough component from a perspective of load and performance at aperture areas from 500 to 2,900m2. Aperture-dependent design was combined with fixed quotations for similar parts from the commercialized SkyTrough product, and established an installed cost of $130/m2 in 2020. This project was conducted in two phases. Phase I was a preliminary design, culminating in an optimum trough size and further improvement of an advanced polymeric reflective material. This phase was completed in October of 2011. Phase II has been the detailed engineering design and component testing, which culminated in the fabrication and testing of a single mirror module. Phase II is complete, and this document presents a summary of the comprehensive work.

  3. Phase-only optical encryption

    DEFF Research Database (Denmark)

    Mogensen, P.C.; Glückstad, J.

    2000-01-01

    We have implemented a phase-only optical encryption and decryption system with a readout based on the generalized phase-contrast method. The experimental system has been implemented with Liquid-crystal spatial light modulators to generate binary phase-encrypted masks and a decrypting key. A phase...

  4. Geometric Properties of Quantum Phases

    OpenAIRE

    P. Bracken

    2006-01-01

    The Aharonov-Anandan phase is introduced from a physical point of view. Without reference to any dynamical equation, this phase is formulated by defining an appropriate connection on a specific fibre bundle. The holonomy element gives the phase. By introducing another connection, the Pancharatnam phase formula is derived following a different procedure.

  5. Phase estimation in optical interferometry

    CERN Document Server

    Rastogi, Pramod

    2014-01-01

    Phase Estimation in Optical Interferometry covers the essentials of phase-stepping algorithms used in interferometry and pseudointerferometric techniques. It presents the basic concepts and mathematics needed for understanding the phase estimation methods in use today. The first four chapters focus on phase retrieval from image transforms using a single frame. The next several chapters examine the local environment of a fringe pattern, give a broad picture of the phase estimation approach based on local polynomial phase modeling, cover temporal high-resolution phase evaluation methods, and pre

  6. Experimental study of the phase equilibria in the Mg–Zn–Ag ternary system at 300 °C

    International Nuclear Information System (INIS)

    Highlights: • The phase equilibria of Mg–Zn–Ag system at 300 °C were determined. • A bcc continuous ternary solid solution forms between MgAg (bcc-B2) and AgZn (bcc-A2) was determined. • The extended solid solubilities of the sub-binary compounds were also determined. - Abstract: The phase equilibria in the Mg–Zn–Ag ternary system at 300 °C were investigated using three diffusion couples and 35 key samples. Scanning electron microscopy (SEM) equipped with energy-dispersive spectroscope (EDS) and X-ray diffraction (XRD) techniques were used for homogeneity ranges and crystal structure determination. Large solid solubility limits, due to substitution among Mg, Zn and Ag atoms in Mg3Ag and MgZn2 phases, were observed in the present work. Solid solubility limits of Ag and Zn in the hcp (Mg) phase were found to be less than 1 at.%. The extended solid solubilities of the Mg12Zn13, Mg2Zn3, MgZn2 (C14), Mg2Zn11, Ag5Zn8 and hcp (AgZn3) sub-binary compounds were also determined in the Mg–Zn–Ag ternary system. In addition, a bcc continuous ternary solid solution forms between MgAg (bcc-B2) and AgZn (bcc-A2) at 300 °C

  7. Phase retrieval and norm retrieval

    OpenAIRE

    Bahmanpour, Saeid; Cahill, Jameson; Casazza, Peter G.; Jasper, John; Woodland, Lindsey M.

    2014-01-01

    Phase retrieval has become a very active area of research. We will classify when phase retrieval by Parseval frames passes to the Naimark complement and when phase retrieval by projections passes to the orthogonal complements. We introduce a new concept we call norm retrieval and show that this is what is necessary for passing phase retrieval to complements. This leads to a detailed study of norm retrieval and its relationship to phase retrieval. One fundamental result: a frame $\\{\\varphi_i\\}...

  8. Engineering Holographic Superconductor Phase Diagrams

    OpenAIRE

    Chen, Jiunn-Wei; Dai, Shou-Huang; Maity, Debaprasad; Zhang, Yun-Long(State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, 100190, China)

    2016-01-01

    We study how to engineer holographic models with features of a high temperature superconductor phase diagram. We introduce a field in the bulk which provides a tunable "doping" parameter in the boundary theory. By designing how this field changes the effective masses of other order parameter fields, desired phase diagrams can be engineered. We give examples of generating phase diagrams with phase boundaries similar to a superconducting dome and an anti-ferromagnetic phase by including two ord...

  9. Phase modulated multiphoton microscopy

    CERN Document Server

    Karki, Khadga Jung; Pullerits, Tonu

    2015-01-01

    We show that the modulation of the phases of the laser beams of ultra-short pulses leads to modulation of the two photon fluorescence intensity. The phase modulation technique when used in multi-photon microscopy can improve the signal to noise ratio. The technique can also be used in multiplexing the signals in the frequency domain in multi-focal raster scanning microscopy. As the technique avoids the use of array detectors as well as elaborate spatiotemporal multiplexing schemes it provides a convenient means to multi-focal scanning in axial direction. We show examples of such uses. Similar methodology can be used in other non-linear scanning microscopies, such as second or third harmonic generation microscopy.

  10. Measurement by phase severance

    International Nuclear Information System (INIS)

    It is claimed that the measurement process is more accurately described by ''quasi-local phase severance'' than by ''wave function collapse''. The approach starts from the observation that the usual route to quantum mechanics starting from the Hamilton-Jacobi equations throws away half the degrees of freedom, namely, the classical initial state parameters. To overcome this difficulty, the full set of Hamilton-Jacobi equations is interpreted as operator equations acting on a state vector. The measurement theory presented is based on the conventional S-matrix boundary condition of N/sub A/ free particles in the distant past and N/sub B/ free particles in the distant future and taking the usual free particle wave functions, multiplied by phase factors

  11. Phase-Measuring System

    Science.gov (United States)

    Davis, W. T.

    1986-01-01

    System developed and used at Langley Research Center measures phase between two signals of same frequency or between two signals, one of which is harmonic multiple of other. Simple and inexpensive device combines digital and analog components to give accurate phase measurements. One signal at frequency f fed to pulse shaper, produces negative pulse at time t4. Pulse applied to control input of sample-and-hold module 1. Second signal, at frequency nf, fed to zero-crossover amplifier, producing square wave at time t. Signal drives first one-shot producing narrow negative pulse at t1. Signal then drives second one-shot producing narrow positive pulse at time t2. This pulse used to turn on solid-state switch and reset integrator circuit to zero.

  12. Optically interconnected phased arrays

    Science.gov (United States)

    Bhasin, Kul B.; Kunath, Richard R.

    1988-01-01

    Phased-array antennas are required for many future NASA missions. They will provide agile electronic beam forming for communications and tracking in the range of 1 to 100 GHz. Such phased arrays are expected to use several hundred GaAs monolithic integrated circuits (MMICs) as transmitting and receiving elements. However, the interconnections of these elements by conventional coaxial cables and waveguides add weight, reduce flexibility, and increase electrical interference. Alternative interconnections based on optical fibers, optical processing, and holography are under evaluation as possible solutions. In this paper, the current status of these techniques is described. Since high-frequency optical components such as photodetectors, lasers, and modulators are key elements in these interconnections, their performance and limitations are discussed.

  13. Gas-Phase Thermolyses

    DEFF Research Database (Denmark)

    Carlsen, Lars; Egsgaard, Helge

    1982-01-01

    The unimolecular gas-phase thermolyses of the four methyl and ethyl monothioacetates (5)–(8) have been studied by the flash vacuum thermolysis–field ionization mass spectrometry technique in the temperature range 883–1 404 K. The types of reactions verified were keten formation, thiono–thiolo rea......The unimolecular gas-phase thermolyses of the four methyl and ethyl monothioacetates (5)–(8) have been studied by the flash vacuum thermolysis–field ionization mass spectrometry technique in the temperature range 883–1 404 K. The types of reactions verified were keten formation, thiono......–thiolo rearrangement, and, in the case of the ethyl esters, ethylene elimination. The possible mechanisms for keten formation are discussed, and it is concluded that the thiono-carboxylates eliminates the mercaptan via an enethiolized structure, whereas the decomposition of the thiolo-esters apparently proceeds via...

  14. Discommensurates and incommensurate phases

    International Nuclear Information System (INIS)

    In its first part, this research thesis reports the study of the commensurate-incommensurate (C-I) transition of single layers of rare gases adsorbed on graphite. The anharmonicity of the interaction between adatoms could explain experimental results corresponding to krypton. The author also studied the orientation instability of the single layer with respect to the chemical potential. Near the C-I transition, walls or discommensurates are oriented in substrate symmetry directions which are determined. The effect of substrate deformation on C-I transition is also studied. In the second part, the author studied the phase diagram at low temperature of the anisotropic Ising model with competing interactions for the approximation of the mean field. Finally, the author presents a phenomenological model of Cerium Antimony which reproduces a large part of its phase diagram

  15. Emergence and Phase Transitions

    Science.gov (United States)

    Sikkema, Arnold

    2006-05-01

    Phase transitions are well defined in physics through concepts such as spontaneous symmetry breaking, order parameter, entropy, and critical exponents. But emergence --- also exhibiting whole-part relations (such as top-down influence), unpredictability, and insensitivity to microscopic detail --- is a loosely-defined concept being used in many disciplines, particularly in psychology, biology, philosophy, as well as in physics[1,2]. I will review the concepts of emergence as used in the various fields and consider the extent to which the methods of phase transitions can clarify the usefulness of the concept of emergence both within the discipline of physics and beyond.1. Robert B. Laughlin, A Different Universe: Reinventing Physics from the Bottom Down (New York: Basic Books, 2005). 2. George F.R. Ellis, ``Physics and the Real World'', Physics Today, vol. 58, no. 7 (July 2005) pp. 49-54.

  16. Phase zone photon sieve

    Institute of Scientific and Technical Information of China (English)

    Jia Jia; Xie Chang-Qing

    2009-01-01

    A novel diffractive optical element, named phase zone photon sieve (PZPS), is presented. There are three kinds of phase plates in PZPSs: PZPS1, PZPS2, and PZPS3. Each of the PZPSs has its own structure and is made on quartz substrate by etching. The three PZPSs have stronger diffraction peak intensity than a photon sieve (PS) when the margin pinhole and zone line width are kept the same. The PZPS3 can produce a smaller central diffractive spot than the ordinary PS with the same number of zones on the Fresnel zone plate. We have given the design method for and the simulation of PZPS and PS. PZPS has potential applications in optical maskless lithography.

  17. Phase shifting interferometer

    Science.gov (United States)

    Sommargren, Gary E.

    1999-01-01

    An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. Whereas current interferometers illuminate the optic to be tested with an aberrated wavefront which also limits the accuracy of the measurement, this interferometer uses an essentially perfect spherical measurement wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.

  18. Phase zone photon sieve

    International Nuclear Information System (INIS)

    A novel diffractive optical element, named phase zone photon sieve (PZPS), is presented. There are three kinds of phase plates in PZPSs: PZPS1, PZPS2, and PZPS3. Each of the PZPSs has its own structure and is made on quartz substrate by etching. The three PZPSs have stronger diffraction peak intensity than a photon sieve (PS) when the margin pinhole and zone line width are kept the same. The PZPS3 can produce a smaller central diffractive spot than the ordinary PS with the same number of zones on the Fresnel zone plate. We have given the design method for and the simulation of PZPS and PS. PZPS has potential applications in optical maskless lithography. (classical areas of phenomenology)

  19. Phase Field Fracture Mechanics.

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Brett Anthony [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-11-01

    For this assignment, a newer technique of fracture mechanics using a phase field approach, will be examined and compared with experimental data for a bend test and a tension test. The software being used is Sierra Solid Mechanics, an implicit/explicit finite element code developed at Sandia National Labs in Albuquerque, New Mexico. The bend test experimental data was also obtained at Sandia Labs while the tension test data was found in a report online from Purdue University.

  20. Engineering Superconducting Phase Qubits

    OpenAIRE

    Blatter, G.; Geshkenbein, V. B.; Ioffe, L.

    1999-01-01

    The superconducting phase qubit combines Josephson junctions into superconducting loops and defines one of the promising solid state device implementations for quantum computing. While conventional designs are based on magnetically frustrated superconducting loops, here we discuss the advantages offered by $\\pi$-junctions in obtaining naturally degenerate two-level systems. Starting from a basic five-junction loop, we show how to construct degenerate two-level junctions and superconducting ph...

  1. Wavefunctions on phase space

    International Nuclear Information System (INIS)

    Theories of Torres-Vega and Fredrick (1993 J. Chem. Phys. 98 3103), Harriman (1994 J. Chem. Phys. 100 3651) and of Ban (1998 J. Math. Phys. 39 1744), in which phase space points (p, q) are used as configurational variables to formulate quantum mechanics are considered from the standpoint of a class of quantization schemes associating phase space functions with operators. The connection between these schemes and the theories given in Torres-Vega and Fredrick (1993 J. Chem. Phys. 98 3103), Harriman (1994 J. Chem. Phys. 100 3651), Dirac (1930 The Principles of Quantum Mechanics (Oxford: Oxford University Press)), Moeller, Joergensen and Torres-Vega (1997 J. Chem. Phys. 106 7228), Klauder and Skagerstam (1985 Coherent States: Applications in Physics and Mathematical Physics (Singapore: World Scientific)), Li, Wei and Lue (2004 Phys. Rev. A 70 022105), Ban (1998 J. Math. Phys. 39 1744) is made by means of augmented wavefunctions ψ(λ)σ(p, q; t), where λ = 0 corresponds to the ordering of Wigner and Weyl. For that case we use these functions to define a family of positive operator-valued measures for the phase angle of an harmonic oscillator

  2. Phases, phase equilibria, and phase rules in low-dimensional systems.

    Science.gov (United States)

    Frolov, T; Mishin, Y

    2015-07-28

    We present a unified approach to thermodynamic description of one, two, and three dimensional phases and phase transformations among them. The approach is based on a rigorous definition of a phase applicable to thermodynamic systems of any dimensionality. Within this approach, the same thermodynamic formalism can be applied for the description of phase transformations in bulk systems, interfaces, and line defects separating interface phases. For both lines and interfaces, we rigorously derive an adsorption equation, the phase coexistence equations, and other thermodynamic relations expressed in terms of generalized line and interface excess quantities. As a generalization of the Gibbs phase rule for bulk phases, we derive phase rules for lines and interfaces and predict the maximum number of phases than may coexist in systems of the respective dimensionality. PMID:26233156

  3. Josephson π states in superfluid 3He B-phase/A-phase/B-phase junctions

    International Nuclear Information System (INIS)

    The l-circumflex accent- texture in the A phase of superfluid 3He B-phase/A-phase/B-phase hybrid junction was a key to form the π state with higher critical current observed in Berkeley. Here we investigate the effect of n-circumflex accent- texture in the B phase on current-phase relations for the BAB junction with a fixed l-circumflex accent- texture. We show that the n-circumflex accent- texture greatly changes the current-phase relation just like l-circumflex accent- texture does. The change is due to the n-circumflex accent-texture-induced modification of the spin structure in the A phase of the BAB junction via the AB boundary condition. As a result, current-phase relations in BAB junctions are determined by the d-circumflex accent- vector in the A phase depending on both n-circumflex accent- and l-circumflex accent- textures

  4. Selective dissolution in AlFeNb alloys

    Energy Technology Data Exchange (ETDEWEB)

    Drensler, Stefanie; Mardare, Cezarina Cela; Hassel, Achim Walter [Institute for Chemical Technology of Inorganic Materials, Johannes Kepler University, Linz (Austria); Milenkovic, Srdjan [IMDEA Materials, Parque Cientifico de la Universidad Carlos III de Madrid, Avda. del mar Mediterraneo 22, 28918 Leganes (Spain)

    2012-05-15

    Three different AlFeNb alloys of various compositions were prepared by arc melting. X-ray diffraction (XRD) investigation of the melted samples proved the presence of two phases identified as a bcc {alpha}(Fe,Al) solid solution and a hexagonal C14 (Fe,Al){sub 2}Nb Laves phase. Subsequent electrochemical treatment allowed for a selective dealloying of the {alpha}(Fe,Al) or respective FeAl phase and resulted in releasing differently microstructured surfaces. These structures ranged from regular lamellar structures towards branched, fibrous structures. Scanning electron microscope (SEM) characterisation along with a local energy dispersive X-ray spectroscopic (EDX) analysis of the samples and atomic absorption spectrometry (AAS) analysis of the electrolyte revealed a preferential Fe dissolution and the passive nature of the Nb. The results demonstrate that the phases present in the alloys strongly depend on the production and heat treatment history of the sample. SEM micrograph of (A) Fe-15Al-10Nb and (B) Fe-26Al-4Nb after anodisation in 0.4 M borate buffer. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Spectral phase conjugation with cross-phase modulation compensation

    OpenAIRE

    Tsang, Mankei; Psaltis, Demetri

    2004-01-01

    Spectral phase conjugation with short pump pulses in a third-order nonlinear material is analyzed in depth. It is shown that if signal amplification is considered, the conversion efficiency can be significantly higher than previously considered, while the spectral phase conjugation operation remains accurate. A novel method of compensating for cross-phase modulation, the main parasitic effect, is also proposed. The validity of our theory and the performance of the spectral phase conjugation s...

  6. Phases and phase transitions in disordered quantum systems

    OpenAIRE

    Vojta, Thomas

    2013-01-01

    These lecture notes give a pedagogical introduction to phase transitions in disordered quantum systems and to the exotic Griffiths phases induced in their vicinity. We first review some fundamental concepts in the physics of phase transitions. We then derive criteria governing under what conditions spatial disorder or randomness can change the properties of a phase transition. After introducing the strong-disorder renormalization group method, we discuss in detail some of the exotic phenomena...

  7. Athena: Assessment Phase Activities

    Science.gov (United States)

    Lumb, David; Ayre, Mark

    2015-09-01

    The Athena mission concept has been proposed by the community in response to science themes of the Hot and Energetic Universe. Unlike other, competitive, mission selection exercises this "Large" class observatory mission has essentially been pre-selected. Nevertheless it has to be demonstrated that Athena meets the programmatic constraints of 1Bn euro cost cap, and a readiness level appropriate for formal mission adoption by the end 2019. This should be confirmed through a Phase A study conducted with two parallel industry activities. We describe the technical and programmatic content of these and latest progress in space and ground segment definition.

  8. Phase change memory

    CERN Document Server

    Qureshi, Moinuddin K

    2011-01-01

    As conventional memory technologies such as DRAM and Flash run into scaling challenges, architects and system designers are forced to look at alternative technologies for building future computer systems. This synthesis lecture begins by listing the requirements for a next generation memory technology and briefly surveys the landscape of novel non-volatile memories. Among these, Phase Change Memory (PCM) is emerging as a leading contender, and the authors discuss the material, device, and circuit advances underlying this exciting technology. The lecture then describes architectural solutions t

  9. Incommensurate phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Currat, R. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1996-11-01

    We review the characteristic aspects of modulated crystals from the point of view of inelastic neutron scattering. We discuss the phenomenological Landau theory of the normal-to-incommensurate displacive instability and its predictions concerning the fluctuation spectrum of the modulated phase. General results on the form of the normal-mode eigenvectors and on the inelastic scattering channels through which they couple to the probe are established using the superspace approach. We illustrate these results on a simple discrete model symmetry and we review available inelastic neutron scattering data on several displacively modulated compounds. (author) 21 figs., 73 refs.

  10. Frequency discriminator/phase detector

    Science.gov (United States)

    Crow, R. B.

    1974-01-01

    Circuit provides dual function of frequency discriminator/phase detector which reduces frequency acquisition time without adding to circuit complexity. Both frequency discriminators, in evaluated frequency discriminator/phase detector circuits, are effective two decades above and below center frequency.

  11. Microcellular foams via phase separation

    International Nuclear Information System (INIS)

    A study of wide variety of processes for making plastic foams shows that phase separation processes for polymers from solutions offers the most viable methods for obtaining rigid plastic foams which met the physical requirements for fusion target designs. Four general phase separation methods have been shown to give polymer foams with densities less than 0.1 g/cm3 and cell sizes of 30μm or less. These methods involve the utilization of non-solvent, chemical or thermal cooling processes to achieve a controlled phase separation wherein either two distinct phases are obtained where the polymer phase is a continuous phase or two bicontinuous phases are obtained where both the polymer and solvent are interpenetrating, continuous, labyrinthine phases. Subsequent removal of the solvent gives the final foam structure

  12. Entanglement and quantum phase transitions

    OpenAIRE

    Gu, Shi-Jian; Tian, Guang-Shan; Lin, Hai-Qing

    2005-01-01

    We examine several well known quantum spin models and categorize behavior of pairwise entanglement at quantum phase transitions. A unified picture on the connection between the entanglement and quantum phase transition is given.

  13. Phase Transitions in Neutron Stars

    OpenAIRE

    Heiselberg, Henning; Hnorth-Jensen, Morten

    1998-01-01

    Phase transitions in neutron stars due to formation of quark matter, kaon condensates, etc. are discussed with particular attention to the order of these transitions. Observational consequences of phase transitions in pulsar angular velocities are examined.

  14. Phases of QCD

    Energy Technology Data Exchange (ETDEWEB)

    Roessner, Simon

    2009-04-09

    Quantum Chromodynamics (QCD) is the theory of the strong interaction within the Standard Model of elementary particles. Today's research in this area dedicates substantial resources to numeric solutions of the QCD field equations and experimental programs exploring the phases of QCD. This thesis proceeds along a complementary line - that of modelling QCD, with the aim of identifying its dominant degrees of freedom. This is possible by minimally coupling effective potentials for the Polyakov loop to Nambu-Jona-Lasinio models using temporal background fields to model chiral symmetry breaking respecting colour confinement. The fermion sign problem resulting from the minimal coupling is addressed in this work establishing a novel, systematically ordered approach. The modifications to the approximative order parameter of colour confinement, the Polyakov loop, are in direct connection with the fermion sign problem. Furthermore an effective coupling of quark densities of different flavours is induced. This mechanism, most likely also present in QCD, produces finite contributions to flavour off diagonal susceptibilities. Susceptibilities are amongst the most promising physical quantities for the experimental exploration of the phase transition at high temperatures and densities. (orig.)

  15. Phases of QCD

    International Nuclear Information System (INIS)

    Quantum Chromodynamics (QCD) is the theory of the strong interaction within the Standard Model of elementary particles. Today's research in this area dedicates substantial resources to numeric solutions of the QCD field equations and experimental programs exploring the phases of QCD. This thesis proceeds along a complementary line - that of modelling QCD, with the aim of identifying its dominant degrees of freedom. This is possible by minimally coupling effective potentials for the Polyakov loop to Nambu-Jona-Lasinio models using temporal background fields to model chiral symmetry breaking respecting colour confinement. The fermion sign problem resulting from the minimal coupling is addressed in this work establishing a novel, systematically ordered approach. The modifications to the approximative order parameter of colour confinement, the Polyakov loop, are in direct connection with the fermion sign problem. Furthermore an effective coupling of quark densities of different flavours is induced. This mechanism, most likely also present in QCD, produces finite contributions to flavour off diagonal susceptibilities. Susceptibilities are amongst the most promising physical quantities for the experimental exploration of the phase transition at high temperatures and densities. (orig.)

  16. EGEE enters second phase

    CERN Multimedia

    2006-01-01

    This month has seen the launch of the second two-year phase of the Enabling Grids for E-sciencE project (EGEE-II), with a transition meeting for the partners held at CERN on 12-13 April. Co-funded by the European Commission and coordinated by CERN, the EGEE project is providing an international Grid computing infrastructure - now numbering some 200 sites and 20 000 CPUs in 39 countries - to support the scientific community worldwide. 'We are all very happy about the smooth start of the second phase of EGEE,' said Project Director Bob Jones. 'The project builds on the successes of its first two years and we are now focussing on the stability of the deployed infrastructure. Growing beyond our pilot application areas of HEP and biomedicine, we now see increasing use by researchers from other fields. Recently we've added finance and fusion to the list of disciplines we support, and we are always looking for new users.' More information on EGEE can be found at www.eu-egee.org.

  17. Supersymmetric phase-space operators

    International Nuclear Information System (INIS)

    A symmetric extension of the phase-space creation-annihilation operators and of the relevant formalism is considered. The symmetric phase-space partner potentials can be introduced and the concepts of supersymmetric quantum mechanics can be almost naturally extended to the phase-space case

  18. Phase Detector For Rectangular Waveforms

    Science.gov (United States)

    Dischert, Robert A.; Walter, James M.

    1993-01-01

    Phase detector for use with phase-locked-loops, servocontrol, and other electronic circuits designed to avoid disadvantages of other phase detectors. Used with both intermittent and continuous input signals. Circuit offers several advantages; reference signals continuous, burst of few pulses, or single pulse. Circuit "coasts" in absence of reference signal. Generates no steady-state output waveform at lock which makes filtering easier.

  19. Phase detector for three-phase power factor controller

    Science.gov (United States)

    Nola, F. J. (Inventor)

    1984-01-01

    A phase detector for the three phase power factor controller (PFC) is described. The phase detector for each phase includes an operational amplifier which senses the current phase angle for that phase by sensing the voltage across the phase thyristor. Common mode rejection is achieved by providing positive feedback between the input and output of the voltage sensing operational amplifier. this feedback preferably comprises a resistor connected between the output and input of the operational amplifier. The novelty of the invention resides in providing positive feedback such that switching of the operational amplifier is synchronized with switching of the voltage across the thyristor. The invention provides a solution to problems associated with high common mode voltage and enables use of lower cost components than would be required by other approaches.

  20. On the solid–liquid phase diagrams of binary mixtures of even saturated fatty alcohols: Systems exhibiting peritectic reaction

    Energy Technology Data Exchange (ETDEWEB)

    Carareto, Natália D.D. [EXTRAE, Department of Food Engineering, Food Engineering Faculty, University of Campinas, UNICAMP, CEP 13083-862 Campinas, SP (Brazil); Santos, Adenílson O. dos [Social Sciences, Health and Technology Center, University of Maranhão, UFMA, CEP 65900-410 Imperatriz, MA (Brazil); Rolemberg, Marlus P. [Institute of Science and Technology, University of Alfenas, UNIFAL, Rodovia José AurélioVilela, CEP 37715400 Poços de Caldas, MG (Brazil); Cardoso, Lisandro P. [Institute of Physics GlebWataghin, University of Campinas, UNICAMP, C.P. 6165, CEP 13083-970 Campinas, SP (Brazil); Costa, Mariana C. [School of Applied Science, University of Campinas, UNICAMP, CEP 13484-350 Limeira, SP (Brazil); Meirelles, Antonio J.A., E-mail: tomze@fea.unicamp.br [EXTRAE, Department of Food Engineering, Food Engineering Faculty, University of Campinas, UNICAMP, CEP 13083-862 Campinas, SP (Brazil)

    2014-08-10

    Highlights: • SLE of binary mixtures of saturated fatty alcohols was studied. • Experimental data were obtained using DSC and stepscan DSC. • Microscopy and X-ray diffraction used as complementary techniques. • Systems presented eutectic, peritectic and metatectic points. - Abstract: The solid–liquid phase diagrams of the following binary mixtures of even saturated fatty alcohols are reported in the literature for the first time: 1-octanol (C8OH) + 1-decanol (C10OH), 1-decanol + 1-dodecanol (C12OH), 1-dodecanol + 1-hexadecanol (C16OH) and 1-tetradecanol (C14OH) + 1-octadecanol (C18OH). The phase diagrams were obtained by differential scanning calorimetry (DSC) using a linear heating rate of 1 K min{sup −1} and further investigated by using a stepscan DSC method. X-ray diffraction (XRD) and polarized light microscopy were also used to complement the characterization of the phase diagrams which have shown a complex global behavior, presenting not only peritectic and eutectic reactions, but also the metatectic reaction and partial immiscibility on solid state.

  1. Electrochemical properties of Ti49Zr26Ni25−xPdx (x = 0–6) quasicrystal electrodes produced by mechanical alloying

    International Nuclear Information System (INIS)

    Highlights: • Formation of icosahedral quasicrystal phase in Ti–Zr–Ni–Pd powders after MA and annealing. • The maximum discharge capacity achieved was 220 mA h/g. • The powder surface turned rough and exhibited various finer pores after hydrogen cycling. - Abstract: Elemental powders consisted of chemical composition of Ti49Zr26Ni25−xPdx (x = 0, 1, 3, 6) were mechanically alloyed and annealed subsequently, and the discharge performance of the electrodes was measured by a three-electrode cell at room temperature. The annealing after mechanical alloying caused a formation of the icosahedral quasicrystal phase with a Ti2Ni type crystal, C14 Laves and α-Ti/Zr phases. The quasilattice constant increased with increasing amount of Pd substituted for Ni up to 3 at.% due to difference in atomic radius between Pd and Ni. The maximum discharge capacity achieved was about 220 mA h/g from a (Ti49Zr26Ni22Pd3) electrode at the first discharge process

  2. Electrochemical properties of Ti{sub 49}Zr{sub 26}Ni{sub 25−x}Pd{sub x} (x = 0–6) quasicrystal electrodes produced by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Ariga, Youhei [Shibaura Institute of Technology, Department of Engineering Science and Mechanics, 3-7-5 Toyosu, Koto-ku, Tokyo 135-8548 (Japan); Takasaki, Akito, E-mail: takasaki@sic.shibaura-it.ac.jp [Shibaura Institute of Technology, Department of Engineering Science and Mechanics, 3-7-5 Toyosu, Koto-ku, Tokyo 135-8548 (Japan); Kimijima, Tsubasa [Shibaura Institute of Technology, Department of Engineering Science and Mechanics, 3-7-5 Toyosu, Koto-ku, Tokyo 135-8548 (Japan); Świerczek, Konrad [AGH University of Science and Technology, Faculty of Energy and Fuels, al. Mickiewicza, 30, 30-059 Kraków (Poland)

    2015-10-05

    Highlights: • Formation of icosahedral quasicrystal phase in Ti–Zr–Ni–Pd powders after MA and annealing. • The maximum discharge capacity achieved was 220 mA h/g. • The powder surface turned rough and exhibited various finer pores after hydrogen cycling. - Abstract: Elemental powders consisted of chemical composition of Ti{sub 49}Zr{sub 26}Ni{sub 25−x}Pd{sub x} (x = 0, 1, 3, 6) were mechanically alloyed and annealed subsequently, and the discharge performance of the electrodes was measured by a three-electrode cell at room temperature. The annealing after mechanical alloying caused a formation of the icosahedral quasicrystal phase with a Ti{sub 2}Ni type crystal, C14 Laves and α-Ti/Zr phases. The quasilattice constant increased with increasing amount of Pd substituted for Ni up to 3 at.% due to difference in atomic radius between Pd and Ni. The maximum discharge capacity achieved was about 220 mA h/g from a (Ti{sub 49}Zr{sub 26}Ni{sub 22}Pd{sub 3}) electrode at the first discharge process.

  3. Geometric phase at graphene edge

    OpenAIRE

    Choi, Sang-Jun; Park, Sunghun; Sim, H. -S.

    2014-01-01

    We study the scattering phase shift of Dirac fermions at graphene edge. We find that when a plane wave of a Dirac fermion is reflected at an edge of graphene, its reflection phase is shifted by the geometric phase resulting from the change of the pseudospin of the Dirac fermion in the reflection. The geometric phase is the Pancharatnam-Berry phase that equals the half of the solid angle on Bloch sphere determined by the propagation direction of the incident wave and also by the orientation an...

  4. Coloured phase singularities

    International Nuclear Information System (INIS)

    For illumination with white light, the spectra near a typical isolated phase singularity (nodal point of the component wavelengths) can be described by a universal function of position, up to linear distortion and a weak dependence on the spectrum of the source. The appearance of the singularity when viewed by a human observer is predicted by transforming the spectrum to trichromatic variables and chromaticity coordinates, and then rendering the colours, scaled to constant luminosity, on a computer monitor. The pattern far from the singularity is a white that depends on the source temperature, and the centre of the pattern is flanked by intensely coloured 'eyes', one orange and one blue, separated by red, and one of the eyes is surrounded by a bright white circle. Only a small range of possible colours appears near the singularity; in particular, there is no green. (author)

  5. Coherent imaging without phases

    CERN Document Server

    Moscoso, Miguel; Papanicolaou, George

    2015-01-01

    In this paper we consider narrow band, active array imaging of weak localized scatterers when only the intensities are recorded at an array with N transducers. We consider that the medium is homogeneous and, hence, wave propagation is fully coherent. This work is an extension of our previous paper, where we showed that using linear combinations of intensity-only measurements imaging of localized scatterers can be carried out efficiently using MUSIC or sparsity promoting optimization. Here we show the same strategy can be accomplished with only 3N-2 illuminations, therefore reducing enormously the data acquisition process. Furthermore, we show that in the paraxial regime one can form the images by using six illuminations only. In particular, this paraxial regime includes Fresnel and Fraunhofer diffraction. The key point of this work is that if one controls the illuminations, imaging with intensity-only can be easily reduced to a imaging with phases and, therefore, one can apply standard imaging techniques. Det...

  6. Solid-phase microextraction

    DEFF Research Database (Denmark)

    Nilsson, Torben

    The objective of this study has been to develop new analytical methods using the rapid, simple and solvent-free extraction technique solid-phase microextraction (SPME) for the quantitative analysis of organic pollutants at trace level in drinking water and environmental samples. The dynamics of...... SPME were examined for halogenated and non-halogenated volatile hydrocarbons, and a standard method for their quantitative analysis in aqueous samples was developed and validated in inter-laboratory studies on the basis of reference material and in comparison with the traditional methods. The...... influences of some possible interferences on the SPME process were examined, and new SPME probes were tested for the in situ monitoring of groundwater pollutants. Inter-laboratory studies were carried out also for the validation of SPME for the quantitative analysis of organochlorine, organonitrogen and...

  7. Phase vocoder and beyond

    Directory of Open Access Journals (Sweden)

    Marco Liuni

    2013-08-01

    Full Text Available For a broad range of sound transformations, quality is measured according to the common expectation about the result: if a male’s voice has to be changed in a female’s one, there exists a common reference for the perceptive evaluation of the result; the same holds if an instrumental sound has to be made longer, or shorter. Following the argument in Röbel, “Between Physics and Perception: Signal Models for High Level Audio Processing”, a fundamental requirement for these transformation algorithms is their need of signal models that are strongly linked to perceptually relevant physical properties of the sound source. This paper is a short survey about the phase vocoder technique, together with its extensions and improvements relying on appropriate sound models, which have led to high level audio processing algorithms.

  8. Options Study - Phase II

    Energy Technology Data Exchange (ETDEWEB)

    R. Wigeland; T. Taiwo; M. Todosow; W. Halsey; J. Gehin

    2010-09-01

    The Options Study has been conducted for the purpose of evaluating the potential of alternative integrated nuclear fuel cycle options to favorably address the issues associated with a continuing or expanding use of nuclear power in the United States. The study produced information that can be used to inform decisions identifying potential directions for research and development on such fuel cycle options. An integrated nuclear fuel cycle option is defined in this study as including all aspects of the entire nuclear fuel cycle, from obtaining natural resources for fuel to the ultimate disposal of used nuclear fuel (UNF) or radioactive wastes. Issues such as nuclear waste management, especially the increasing inventory of used nuclear fuel, the current uncertainty about used fuel disposal, and the risk of nuclear weapons proliferation have contributed to the reluctance to expand the use of nuclear power, even though it is recognized that nuclear power is a safe and reliable method of producing electricity. In this Options Study, current, evolutionary, and revolutionary nuclear energy options were all considered, including the use of uranium and thorium, and both once-through and recycle approaches. Available information has been collected and reviewed in order to evaluate the ability of an option to clearly address the challenges associated with the current implementation and potential expansion of commercial nuclear power in the United States. This Options Study is a comprehensive consideration and review of fuel cycle and technology options, including those for disposal, and is not constrained by any limitations that may be imposed by economics, technical maturity, past policy, or speculated future conditions. This Phase II report is intended to be used in conjunction with the Phase I report, and much information in that report is not repeated here, although some information has been updated to reflect recent developments. The focus in this Options Study was to

  9. VFT PHASE VOLTAGE MEASUREMENT IN THREE-PHASE ENCLOSED GIS

    Institute of Scientific and Technical Information of China (English)

    邹建华; 岳子丁; 李洋

    2002-01-01

    The measuring of VFT phase voltage in three-phase enclosed GIS is more complex and difficult than in single-phase ones. There are 3 capacitive sensors in the measuring system, the outputs of which are with a linear relation to the three phase voltages. This linear relation is presented with a factorial matrix. Because each capacitive sensor is coupled with the electric field of three phases (A, B, and C), the electric coupling coefficients are introduced. In order to determine the matrix of electric coupling coefficients, the numerical calculation method can be used. From the discussion on two types of three-phase enclosed GIS bus, i.e. standard arrangement and biased arrangement, the dominant electric coupling coefficients are named, which can be simply and approximately calculated by an analytic expression. Finally, as an example, the waveforms of VFT phase voltage generated on a three-phase enclosed GIS bus model are displayed. When a capacitive sensor is located at the 'shortest point' of phase A (or B, or C), the VFT phase voltage VA (or VB, or VC) can almost be measured by that capacitive sensor alone.

  10. Phase Coarsening in Thin Films

    Science.gov (United States)

    Wang, K. G.; Glicksman, M. E.

    2015-08-01

    Phase coarsening (Ostwald ripening) phenomena are ubiquitous in materials growth processes such as thin film formation. The classical theory explaining late-stage phase coarsening phenomena was developed by Lifshitz and Slyozov, and by Wagner in the 1960s. Their theory is valid only for a vanishing volume fraction of the second phase in three dimensions. However, phase coarsening in two-dimensional systems is qualitatively different from that in three dimensions. In this paper, the many-body concept of screening length is reviewed, from which we derive the growth law for a `screened' phase island, and develop diffusion screening theory for phase coarsening in thin films. The coarsening rate constant, maximum size of phase islands in films, and their size distribution function will be derived from diffusion screening theory. A critical comparison will be provided of prior coarsening concepts and improvements derived from screening approaches.

  11. Engineering Holographic Superconductor Phase Diagrams

    CERN Document Server

    Chen, Jiunn-Wei; Maity, Debaprasad; Zhang, Yun-Long

    2016-01-01

    We study how to engineer holographic models with features of a high temperature superconductor phase diagram. We introduce a field in the bulk which provides a tunable "doping" parameter in the boundary theory. By designing how this field changes the effective masses of other order parameter fields, desired phase diagrams can be engineered. We give examples of generating phase diagrams with phase boundaries similar to a superconducting dome and an anti-ferromagnetic phase by including two order parameter fields. We also explore whether the pseudo gap phase can be described without adding another order parameter field and discuss the potential scaling symmetry associated with a quantum critical point hidden under the superconducting dome in this phase diagram.

  12. Para-equilibrium phase diagrams

    International Nuclear Information System (INIS)

    Highlights: • A rapidly cooled system may attain a state of para-equilibrium. • In this state rapidly diffusing elements reach equilibrium but others are immobile. • Application of the Phase Rule to para-equilibrium phase diagrams is discussed. • A general algorithm to calculate para-equilibrium phase diagrams is described. - Abstract: If an initially homogeneous system at high temperature is rapidly cooled, a temporary para-equilibrium state may result in which rapidly diffusing elements have reached equilibrium but more slowly diffusing elements have remained essentially immobile. The best known example occurs when homogeneous austenite is quenched. A para-equilibrium phase assemblage may be calculated thermodynamically by Gibbs free energy minimization under the constraint that the ratios of the slowly diffusing elements are the same in all phases. Several examples of calculated para-equilibrium phase diagram sections are presented and the application of the Phase Rule is discussed. Although the rules governing the geometry of these diagrams may appear at first to be somewhat different from those for full equilibrium phase diagrams, it is shown that in fact they obey exactly the same rules with the following provision. Since the molar ratios of non-diffusing elements are the same in all phases at para-equilibrium, these ratios act, as far as the geometry of the diagram is concerned, like “potential” variables (such as T, pressure or chemical potentials) rather than like “normal” composition variables which need not be the same in all phases. A general algorithm to calculate para-equilibrium phase diagrams is presented. In the limit, if a para-equilibrium calculation is performed under the constraint that no elements diffuse, then the resultant phase diagram shows the single phase with the minimum Gibbs free energy at any point on the diagram; such calculations are of interest in physical vapor deposition when deposition is so rapid that phase

  13. Nonlinear Phase Control and Anomalous Phase Matching in Plasmonic Metasurfaces

    CERN Document Server

    Almeida, Euclides; Prior, Yehiam

    2015-01-01

    Metasurfaces, and in particular those containing plasmonic-based metallic elements, constitute a particularly attractive set of materials. By means of modern nanolithographic fabrication techniques, flat, ultrathin optical elements may be constructed. However, in spite of their strong optical nonlinearities, plasmonic metasurfaces have so far been investigated mostly in the linear regime. Here we introduce full nonlinear phase control over plasmonic elements in metasurfaces. We show that for nonlinear interactions in a phase-gradient nonlinear metasurface a new anomalous nonlinear phase matching condition prevails, which is the nonlinear analog of the generalized Snell law demonstrated for linear metasurfaces. This phase matching condition is very different from the other known phase matching schemes. The subwavelength phase control of optical nonlinearities provides a foundation for the design of flat nonlinear optical elements based on metasurfaces. Our demonstrated flat nonlinear elements (i.e. lenses) act...

  14. Joint estimation of phase and phase diffusion for quantum metrology

    CERN Document Server

    Vidrighin, Mihai D; Genoni, Marco G; Jin, Xian-Min; Kolthammer, W Steven; Kim, M S; Datta, Animesh; Barbieri, Marco; Walmsley, Ian A

    2014-01-01

    Phase estimation, at the heart of many quantum metrology and communication schemes, can be strongly affected by noise, whose amplitude may not be known, or might be subject to drift. Here, we investigate the joint estimation of a phase shift and the amplitude of phase diffusion, at the quantum limit. For several relevant instances, this multiparameter estimation problem can be effectively reshaped as a two-dimensional Hilbert space model, encompassing the description of an interferometer phase probed with relevant quantum states -- split single-photons, coherent states or N00N states. For these cases, we obtain a trade-off bound on the statistical variances for the joint estimation of phase and phase diffusion, as well as optimum measurement schemes. We use this bound to quantify the effectiveness of an actual experimental setup for joint parameter estimation for polarimetry. We conclude by discussing the form of the trade-off relations for more general states and measurements.

  15. Jeg anerkender den musikalske tradition - men jeg prøver ikke at lave musik

    DEFF Research Database (Denmark)

    Holmboe, Rasmus

    2013-01-01

    Interview med Jacob Kirkegaard i anledning af hans udgivelse: ”Conversion”. Det blev en samtale om reallyde, der bliver til instrumentallyde, om afvisningen af det subjektive udtryk, og om hvordan musikken i sidste ende ikke er komponistens men lytterens anliggende....

  16. Phase appearance or disappearance in two-phase flows

    OpenAIRE

    Cordier, Floraine; Degond, Pierre; Kumbaro, Anela

    2011-01-01

    This paper is devoted to the treatment of specific numerical problems which appear when phase appearance or disappearance occurs in models of two-phase flows. Such models have crucial importance in many industrial areas such as nuclear power plant safety studies. In this paper, two outstanding problems are identified: first, the loss of hyperbolicity of the system when a phase appears or disappears and second, the lack of positivity of standard shock capturing schemes such as the Roe scheme. ...

  17. Simulation of Mission Phases

    Science.gov (United States)

    Carlstrom, Nicholas Mercury

    2016-01-01

    This position with the Simulation and Graphics Branch (ER7) at Johnson Space Center (JSC) provided an introduction to vehicle hardware, mission planning, and simulation design. ER7 supports engineering analysis and flight crew training by providing high-fidelity, real-time graphical simulations in the Systems Engineering Simulator (SES) lab. The primary project assigned by NASA mentor and SES lab manager, Meghan Daley, was to develop a graphical simulation of the rendezvous, proximity operations, and docking (RPOD) phases of flight. The simulation is to include a generic crew/cargo transportation vehicle and a target object in low-Earth orbit (LEO). Various capsule, winged, and lifting body vehicles as well as historical RPOD methods were evaluated during the project analysis phase. JSC core mission to support the International Space Station (ISS), Commercial Crew Program (CCP), and Human Space Flight (HSF) influenced the project specifications. The simulation is characterized as a 30 meter +V Bar and/or -R Bar approach to the target object's docking station. The ISS was selected as the target object and the international Low Impact Docking System (iLIDS) was selected as the docking mechanism. The location of the target object's docking station corresponds with the RPOD methods identified. The simulation design focuses on Guidance, Navigation, and Control (GNC) system architecture models with station keeping and telemetry data processing capabilities. The optical and inertial sensors, reaction control system thrusters, and the docking mechanism selected were based on CCP vehicle manufacturer's current and proposed technologies. A significant amount of independent study and tutorial completion was required for this project. Multiple primary source materials were accessed using the NASA Technical Report Server (NTRS) and reference textbooks were borrowed from the JSC Main Library and International Space Station Library. The Trick Simulation Environment and User

  18. Structural phase transitions in HfV2Hsub(x) and Zrsub(0.99)Hf0.01V2Hsub(x) observed in time differential perturbed angular correlation studies

    International Nuclear Information System (INIS)

    The temperature dependence of electric field gradients was measured in the intermetallic compounds HfV2 and Zrsub(0.99)Hfsub(0.01)V2, their hydrides HfV2Hsub(x) (x=0.4, 1., 4.) and Zrsub(0.99)Hfsub(0.01)V2Hsub(x) (x=0.4, 1.3), and the deuterides HfV2Dsub(0.4) and Zrsub(0.99)Hfsub(0.01)V2Dsub(0.4). The measurement is based on the hyperfine interaction at the probe nucleus 181Ta. These parameters allowed to follow the configurational changes with respect to the hafnium sites in a sensitive and quantitative manner. In Zrsub(0.99)Hfsub(0.01)V2 the distortion of the cubic Laves phase was observed for the temperature range below 110(3) K. This finding is in accordance with neutron diffraction data. Furthermore a strong deviation from axial symmetry was measured. Thus a reduction of symmetry is indicated which exceeds the purely rhomboedric distortion so far resolved. For HfV2 it is also inferred that symmetry is reduced to be not higher than orthorhombic. At room temperature the same perturbation of cubic symmetry was induced locally by neutron irradiation and demonstrated to be of high thermal stability. These results support the idea that the phase transition is due to a band Jahn-Teller effect. The values of the electric field gradients vary with a temperature dependence characteristic for order parameters. The related critical exponent classes the phase transition akin to 3-dimensional Ising models. In Zrsub(0.99)Hfsub(0.01)V2Hsub(0.4)/Dsub(0.4) hydrogen free domains were observed at low temperatures. Such fractions were not resolved for the other hydrides. The latter exhibit a transition from a low symmetric to a cubic structure at distinctly higher temperatures (above ca. 230 K). (orig./GSCH)

  19. Modern windships. Phase 1

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-11-01

    Knud E. Hansen A/S (KEH) has, partly funded by the Energy Research Programme, (EFP-95) investigated in the possibilities of using windships for transportation of cargo on long routes, i.e. across the Atlantic or Pacific Ocean. The task was to peruse experiences from projects made during the past 30 years and then, based on new materials and design principle to make proposals to modern wind driven ships to transportation of cargo - especially bulk carriers. KEH has thus prepared a suggestion for a 50,000 DWT wind driven bulk carrier on these terms. The bulk carrier in question is a modern rig inspired by the classical lugger and junk sail with a total sail area of abt. 10,000 m{sup 2}. The hull of the ship has been developed in order to limit wave resistance and drifting. Project Windship has, in contrast to earlier tests and projects, designed a bulk carrier based on a complete evaluation of ecology, safety, economy and reasonable transportation speed. The research project shows that international sea transportation, with wind as the primary source of energy, does not seem to run up against any obstacles as regards safety. The economical analyses show that windship transportation, with today`s oil prices, will be about 10% higher compared to the diesel driven transportation. In the light of the positive results of the research project the steering committee recommends that phase II of project `Modern Windships` is carried out. (EG)

  20. Modern windships. Phase 1

    International Nuclear Information System (INIS)

    Knud E. Hansen A/S (KEH) has, partly funded by the Energy Research Programme, (EFP-95) investigated in the possibilities of using windships for transportation of cargo on long routes, i.e. across the Atlantic or Pacific Ocean. The task was to peruse experiences from projects made during the past 30 years and then, based on new materials and design principle to make proposals to modern wind driven ships to transportation of cargo - especially bulk carriers. KEH has thus prepared a suggestion for a 50,000 DWT wind driven bulk carrier on these terms. The bulk carrier in question is a modern rig inspired by the classical lugger and junk sail with a total sail area of abt. 10,000 m2. The hull of the ship has been developed in order to limit wave resistance and drifting. Project Windship has, in contrast to earlier tests and projects, designed a bulk carrier based on a complete evaluation of ecology, safety, economy and reasonable transportation speed. The research project shows that international sea transportation, with wind as the primary source of energy, does not seem to run up against any obstacles as regards safety. The economical analyses show that windship transportation, with today's oil prices, will be about 10% higher compared to the diesel driven transportation. In the light of the positive results of the research project the steering committee recommends that phase II of project 'Modern Windships' is carried out. (EG)

  1. Kinetics of phase transformations

    International Nuclear Information System (INIS)

    This volume contains papers presented at the Materials Research Society symposium on Kinetics of Phase Transformations held in Boston, Massachusetts from November 26-29, 1990. The symposium provided a forum for research results in an exceptionally broad and interdisciplinary field. Presentations covered nearly every major class of transformations including solid-solid, liquid-solid, transport phenomena and kinetics modeling. Papers involving amorphous Si, a dominant topic at the symposium, are collected in the first section followed by sections on four major areas of transformation kinetics. The symposium opened with joint sessions on ion and electron beam induced transformations in conjunction with the Surface Chemistry and Beam-Solid Interactions: symposium. Subsequent sessions focused on the areas of ordering and nonlinear diffusion kinetics, solid state reactions and amorphization, kinetics and defects of amorphous silicon, and kinetics of melting and solidification. Seven internationally recognized invited speakers reviewed many of the important problems and recent results in these areas, including defects in amorphous Si, crystal to glass transformations, ordering kinetics, solid-state amorphization, computer modeling, and liquid/solid transformations

  2. Phase-Oriented Gear Systems

    Science.gov (United States)

    Vranish, John M.

    2007-01-01

    Phase-oriented gear systems are differential planetary transmissions in which each planet gear has two sets of unequal numbers of teeth indexed at prescribed relative angles (phases). The figure illustrates an application of the phase-oriented gearing concept to a relatively simple speed-reducing differential planetary transmission that includes a sun gear, an idler gear, three identical planet gears, a ground internal ring gear, and an output internal ring gear. Typically, the ground internal ring gear and output internal ring gear have different numbers of teeth, giving rise to a progressive and periodic phase shift between the corresponding pairs of teeth engaged by each successive planet gear. To accommodate this phase shift, it is necessary to introduce a compensating phase shift between the ground-gear-engaging and output-gearengaging sections of each planet gear. This is done by individually orienting each planet gear

  3. Asymptotic Phase for Stochastic Oscillators

    Science.gov (United States)

    Thomas, Peter J.; Lindner, Benjamin

    2014-12-01

    Oscillations and noise are ubiquitous in physical and biological systems. When oscillations arise from a deterministic limit cycle, entrainment and synchronization may be analyzed in terms of the asymptotic phase function. In the presence of noise, the asymptotic phase is no longer well defined. We introduce a new definition of asymptotic phase in terms of the slowest decaying modes of the Kolmogorov backward operator. Our stochastic asymptotic phase is well defined for noisy oscillators, even when the oscillations are noise dependent. It reduces to the classical asymptotic phase in the limit of vanishing noise. The phase can be obtained either by solving an eigenvalue problem, or by empirical observation of an oscillating density's approach to its steady state.

  4. Oscillatory phase shapes syllable perception.

    Science.gov (United States)

    Ten Oever, Sanne; Sack, Alexander T

    2015-12-29

    The role of oscillatory phase for perceptual and cognitive processes is being increasingly acknowledged. To date, little is known about the direct role of phase in categorical perception. Here we show in two separate experiments that the identification of ambiguous syllables that can either be perceived as /da/ or /ga/ is biased by the underlying oscillatory phase as measured with EEG and sensory entrainment to rhythmic stimuli. The measured phase difference in which perception is biased toward /da/ or /ga/ exactly matched the different temporal onset delays in natural audiovisual speech between mouth movements and speech sounds, which last 80 ms longer for /ga/ than for /da/. These results indicate the functional relationship between prestimulus phase and syllable identification, and signify that the origin of this phase relationship could lie in exposure and subsequent learning of unique audiovisual temporal onset differences. PMID:26668393

  5. On the quantum phase problem

    Energy Technology Data Exchange (ETDEWEB)

    Vargas-MartInez, J M; Moya-Cessa, H [INAOE, Coordinacion de Optica, Apartado Postal 51 y 216, 72000 Puebla (Mexico)

    2004-03-01

    Based on the phase operator introduced by Turski we present a formalism for phase that passes Barnett-Pegg's acid test giving the correct phase variance for a number state. We show that this formalism is in fact the radially integrated Q-function formalism that is used to obtain phase properties. It is also shown that depending on the commutation relation used for phase and number, the phase fluctuations for a coherent state obtained from the integrated Q-function tend to the 1/2{rho}{sup 2} limit while for the Pegg-Barnett formalism they tend to 1/(4{rho}{sup 2}+3/{pi}{sup 2}) just like the fluctuations from the integrated Wigner function, where {rho} is the amplitude of the coherent state00.

  6. Modulational instability of nematic phase

    Indian Academy of Sciences (India)

    T Mithun; K Porsezian

    2014-02-01

    We numerically observe the effect of homogeneous magnetic field on the modulationally stable case of polar phase in = 2 spinor Bose–Einstein condensates (BECs). Also we investigate the modulational instability of uniaxial and biaxial (BN) states of polar phase. Our observations show that the magnetic field triggers the modulational instability and demonstrate that irrespective of the magnetic field effect the uniaxial and biaxial nematic phases show modulational instability.

  7. Using projections for phase retrieval

    Science.gov (United States)

    Cahill, Jameson; Casazza, Peter G.; Peterson, Jesse; Woodland, Lindsey M.

    2013-09-01

    The mathematical study of phase retrieval was started in 2006 in a landmark paper of Balan, Casazza and Edidin. This quickly became a heavily studied topic with implications for many areas of research in both applied mathematics and engineering. Recently there have been developments in a new area of study pertaining to phase retrieval given by projections. We give an extensive overview of the papers regarding projection phase retrieval.

  8. Phase Retrieval Versus Phaseless Reconstruction

    OpenAIRE

    Botelho-Andrade, Sara; Casazza, Peter G.; Nguyen, Hanh; Tremain, Janet C.

    2015-01-01

    In 2006, Balan/Casazza/Edidin \\cite{BCE} introduced the frame theoretic study of phaseless reconstruction. Since then, this has turned into a very active area of research. Over the years, many people have replaced the term {\\it phaseless reconstruction} with {\\it phase retrieval}. Casazza then asked: {\\it Are these really the same?} In this paper, we will show that phase retrieval is equivalent to phaseless reconstruction. We then show, more generally, that phase retrieval by projections is e...

  9. Singularly perturbed phase response curves

    OpenAIRE

    Sacré, Pierre; Franci, Alessio

    2015-01-01

    In this paper we propose a novel geometric method, based on singular perturbations, to approximate isochrones of relaxation oscillators and predict the qualitative shape of their (finite) phase response curve. This approach complements the infinitesimal phase response curve approach to relaxation oscillators and overcomes its limitations near the singular limit. We illustrate the power of the methodology by deriving semi-analytic formula for the (finite) phase response curve of generic planar...

  10. Superconductors with Mesoscopic Phase Separation

    OpenAIRE

    Coleman, A.J.; Yukalova, E. P.; V. I. Yukalov

    1997-01-01

    A model of superconductivity is proposed taking into account repulsive particle interaction, mesoscopic phase separation and softening of crystalline lattice. These features are typical of many high-temperature superconductors. The main results obtained for the model are: (i) phase separation is possible only if repulsive forces play a significant role; (ii) the critical temperature as a function of the superconducting phase fraction can have non-monotonic behaviour; (iii) superconductivity i...

  11. Phase stepping in Lau interferometry

    OpenAIRE

    Ángel-Toro, Luciano; Tebaldi, Myrian; Henao, Rodrigo

    1999-01-01

    The implementation of phase shifting interferometry to analyze the Lau interferometric fringe patterns is proposed. The fundamentals of this application are theoretically discussed and the basis of the phase map interpretation is outlined. The three steps algorithm is used to depict the phase maps of lens-like test objects and an application for measuring focal lengths of lenses is reported. Experimental results are presented. q1999 Elsevier Science B.V. All rights reserved.

  12. Phase barograms–phase diagrams of vapor pressure: Eutectoid phase formation in binary systems

    International Nuclear Information System (INIS)

    Highlights: ► Thermodynamic considerations of complex heterogeneous equilibria. ► Derivative of the three-dimensional Clausius–Clapeyron equation. ► Relationship between phase diagram and related phase barogram. ► Transformation of thermal effects of vapor pressure measurements. ► Eutectoid phase formation CsSeO2Br in the system CsBr/SeO2. - Abstract: Phase barograms are specific representations of conventional (x, T) phase diagrams considering the vapor pressure as additional thermodynamic parameter. Thus, the determination of the vapor pressure is complementary to conventional DTA or DSC measurements. A stringent relationship between the phase diagram and the corresponding phase barogram is derived by thermodynamic considerations of phase relations for complex heterogeneous equilibria. For that purpose, a derivative of the three-dimensional Clausius–Clapeyron equation is utilized. As a result, a validation of DTA/DSC measurements becomes feasible by the transformation of characteristic effects of vapor pressure measurements into thermal effects in conventional phase diagrams. The system CsBr/SeO2 is presented as a case study of systems with a eutectoid phase formation. CsSeO2Br is formed from the binaries at θf = 180(5) °C; the compound decomposes peritectically at θp = 470(10) °C.

  13. Carbon nanotube grafted with polyalcohol and its influence on the thermal conductivity of phase change material

    International Nuclear Information System (INIS)

    Highlights: • CNTs are grafted with polyhydric alcohols. • The grafted CNTs are well dispersed. • The graft ratio of CNTs-C8, CNTs-C14 and CNTs-C18 is 11%, 32% and 38%. • The thermal conductivities of CNTs/paraffin are increased through graft treatment. • The carbon number of polyalcohol has influence on thermal conductivity. - Abstract: Carbon nanotubes (CNTs) were grafted with polyhydric alcohols (octanol, tetradecyl alchohol and stearyl alcohol) after acidification. The composite phase change materials (PCMs) were prepared with grafted CNTs and paraffin. The grafted CNTs were characterized with Transmission Electron Micrograph (TEM), X-ray Diffractometer (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric analyzer (TG). Hot disk method was employed to measure the thermal conductivity of composite PCMs. The results showed that polyhydric alcohols were grafted onto CNTs. The graft ratio was 38% for the CNTs grafted with stearyl alcohol. The grafted CNTs were shorter than CNTs and the dispersibility of grafted CNTs was better than that of CNTs. The thermal conductivity of grafted CNTs/paraffin composite PCMs was higher than that of pristine CNTs/paraffin composite PCMs

  14. The Tb-Re-B system: Phase equilibria and crystal structures

    International Nuclear Information System (INIS)

    The phase diagram at 1270 K of the Tb-Re-B system is constructed by X-ray analysis. The existence of the earlier known compounds is confirmed: Tb3ReB7 (Er3CrB7 structure type), TbReB4 (YCrB4 structure type, refined lattice parameters a = 5.9776(4), b = 11.5640(9), c = 3.6058(3) A) and Tb2ReB6 (Y2ReB6 structure type, refined lattice parameters a = 9.206(4), b = 11.56094), c = 3.669(1) A). New ternary compounds are found and their crystal structure are determined: Tb8Re13-xB12 (DRON-3M powder diffractometer, R3m space group, Pr8Re13-xB12 structure type, a 10.6233(6), c = 14.318(1) A, Nhkl = 286, R =0.095) and TbεRe4B4 (a single crystal method, the tetragonal incommensurate structure, a 10.624(9), c = 38.29(9) A). (author)

  15. Phase structure of soliton molecules

    International Nuclear Information System (INIS)

    Temporal optical soliton molecules were recently demonstrated; they potentially allow further increase of data rates in optical telecommunication. Their binding mechanism relies on the internal phases, but these have not been experimentally accessible so far. Conventional frequency-resolved optical gating techniques are not suited for measurement of their phase profile: Their algorithms fail to converge due to zeros both in their temporal and their spectral profile. We show that the VAMPIRE (very advanced method of phase and intensity retrieval of E-fields) method performs reliably. With VAMPIRE the phase profile of soliton molecules has been measured, and further insight into the mechanism is obtained

  16. Phase structure of soliton molecules

    Science.gov (United States)

    Hause, A.; Hartwig, H.; Seifert, B.; Stolz, H.; Böhm, M.; Mitschke, F.

    2007-06-01

    Temporal optical soliton molecules were recently demonstrated; they potentially allow further increase of data rates in optical telecommunication. Their binding mechanism relies on the internal phases, but these have not been experimentally accessible so far. Conventional frequency-resolved optical gating techniques are not suited for measurement of their phase profile: Their algorithms fail to converge due to zeros both in their temporal and their spectral profile. We show that the VAMPIRE (very advanced method of phase and intensity retrieval of E -fields) method performs reliably. With VAMPIRE the phase profile of soliton molecules has been measured, and further insight into the mechanism is obtained.

  17. Qubit rotation and Berry phase

    International Nuclear Information System (INIS)

    A quantized fermion is represented by a scalar particle encircling a magnetic flux line. It has the spinor structure which can be constructed from quantum gates and qubits. We have studied here the role of Berry phase in removing dynamical phase during one qubit rotation of a quantized fermion. The entanglement of two qubits inserting spin-echo to one of them results the trapped Berry phase to measure entanglement. Some effort is given to study the effect of noise on the Berry phase of spinors and their entangled states. (author)

  18. Magnetic resonance of phase transitions

    CERN Document Server

    Owens, Frank J; Farach, Horacio A

    1979-01-01

    Magnetic Resonance of Phase Transitions shows how the effects of phase transitions are manifested in the magnetic resonance data. The book discusses the basic concepts of structural phase and magnetic resonance; various types of magnetic resonances and their underlying principles; and the radiofrequency methods of nuclear magnetic resonance. The text also describes quadrupole methods; the microwave technique of electron spin resonance; and the Mössbauer effect. Phase transitions in various systems such as fluids, liquid crystals, and crystals, including paramagnets and ferroelectrics, are also

  19. Condensed phase decomposition and gas phase combustion of hydrazinium nitroformate

    NARCIS (Netherlands)

    Dragomir, O.E.; Tummers, M.J.; Veen, E.H. van; Heijden, A.E.D.M. van der; Roekaerts, D.J.E.M.

    2009-01-01

    This paper presents the results of a series of experiments on the condensed phase decomposition and the gas phase combustion of hydrazinium nitroformate (HNF). The experiments include SEM analysis of quenched samples that showed evidence of the formation of a foam layer. FTIR spectrometry and mass s

  20. Invalid phase values removal method for absolute phase recovery.

    Science.gov (United States)

    Lu, Jin; Mo, Rong; Sun, Huibin; Chang, Zhiyong; Zhao, Xiaxia

    2016-01-10

    A novel approach is presented for more effectively removing invalid phase values in absolute phase recovery. The approach is based on a detailed study involving the types and cases of invalid phase values. Meanwhile, some commonalities of the existing removal algorithms also are thoroughly analyzed. It is well known that rough absolute phase and fringe order maps can very easily be obtained by temporal phase unwrapping techniques. After carefully analyzing the components and fringe order distribution of the rough fringe order map, the proposed method chiefly adopts an entirely new strategy to refine a pure fringe order map. The strategy consists of three parts: (1) the square of an image gradient, (2) subregion areas of the binary image, and (3) image decomposition and composition. In combination with the pure fringe order map and a removal criterion, the invalid phase values can be identified and filtered out from the rough absolute phase map. This new strategy not only gets rid of the limitations of traditional removal methods but also has a two-fold function. The paper also offers different metrics from the experiment to evaluate the quality of the final absolute phase. In contrast with other removal methods, experimental results have verified the feasibility, effectiveness, and superiority of the proposed method. PMID:26835776