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Sample records for 3d-perekhyidnikh ta blagorodnikh

  1. INRAD work at TA-55

    SciTech Connect

    Kleinschmidt, Phillip D; Lacy, Keith A; Hahn, Wendy K; Shonrock, Clinton O

    2011-01-18

    The INRAD Facility at TA-55 is described. Safety considerations in operating the facility are described in the Detailed Operating Procedure (DOP) format. Other considerations on the future operation of the facility are discussed.

  2. EUSO-TA prototype telescope

    NASA Astrophysics Data System (ADS)

    Bisconti, Francesca

    2016-07-01

    EUSO-TA is one of the prototypes developed for the JEM-EUSO project, a space-based large field-of-view telescope to observe the fluorescence light emitted by cosmic ray air showers in the atmosphere. EUSO-TA is a ground-based prototype located at the Telescope Array (TA) site in Utah, USA, where an Electron Light Source and a Central Laser Facility are installed. The purpose of the EUSO-TA project is to calibrate the prototype with the TA fluorescence detector in presence of well-known light sources and cosmic ray air showers. In 2015, the detector started the first measurements and tests using the mentioned light sources have been performed successfully. A first cosmic ray candidate has been observed, as well as stars of different magnitude and color index. Since Silicon Photo-Multipliers (SiPMs) are very promising for fluorescence telescopes of next generation, they are under consideration for the realization of a new prototype of EUSO Photo Detector Module (PDM). The response of this sensor type is under investigation through simulations and laboratory experimentation.

  3. The TA and TALE Experiments

    NASA Astrophysics Data System (ADS)

    Thomson, Gordon

    2006-10-01

    The TA/TALE experiment is under construction, and is being deployed in Millard County, Utah. It will consist of a suite of detectors covering four orders of magnitude in energy, from 1016.5 to 1020.5eV, and will observe cosmic ray showers with fluorescence detectors and arrays of scintillation counters. Events will be seen by multiple detectors and cross calibration of detectors' energy scales will be possible. TA/TALE will observe all three features of the spectrum of ultrahigh energy cosmic rays, observe the galactic/extragalactic transition, study the cosmology of cosmic ray sources, and perform anisotropy studies with unprecedented accuracy.

  4. TA-55 change control manual

    SciTech Connect

    Blum, T.W.; Selvage, R.D.; Courtney, K.H.

    1997-11-01

    This manual is the guide for initiating change at the Plutonium Facility, which handles the processing of plutonium as well as research on plutonium metallurgy. It describes the change and work control processes employed at TA-55 to ensure that all proposed changes are properly identified, reviewed, approved, implemented, tested, and documented so that operations are maintained within the approved safety envelope. All Laboratory groups, their contractors, and subcontractors doing work at TA-55 follow requirements set forth herein. This manual applies to all new and modified processes and experiments inside the TA-55 Plutonium Facility; general plant project (GPP) and line item funded construction projects at TA-55; temporary and permanent changes that directly or indirectly affect structures, systems, or components (SSCs) as described in the safety analysis, including Facility Control System (FCS) software; and major modifications to procedures. This manual does not apply to maintenance performed on process equipment or facility SSCs or the replacement of SSCs or equipment with documented approved equivalents.

  5. 78 FR 28627 - TA-W-80,340; TA-W-80,340A; TA-W-80,340B

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-15

    ... Employment and Training Administration TA-W-80,340; TA-W-80,340A; TA-W-80,340B] Bush Industries, Inc., Mason... (TA-W-80,340) and Bush Industries, Inc., Allen Street Facility, Jamestown, New York (TA-W- 80,340A... the subject firm's Erie, Pennsylvania facility. The amended notice applicable to TA-W-80,340 is...

  6. Subduction related fluids fractionate Nb/Ta

    NASA Astrophysics Data System (ADS)

    Salters, V. J.; Bizimis, M.; Sachi-Kocher, A.; Taylor, R.; Savov, I. P.; Stern, C. R.

    2009-12-01

    Key differences between the chemical composition of terrestrial materials and those of meteorites have led to the suggestion that a `hidden’ high Nb/Ta reservoir exists in the Earth’s mantle. In order to test this hypothesis we must identify the processes that can create such a reservoir. It has been suggested that during subduction Nb is more refractory then Ta resulting in low Nb/Ta in the subducted slab, which then serves as a reservoir for the high Nb/Ta. Here we report high precision HFSE data on products of the subduction processes thought to fractionate Nb from Ta: boninites (hydrous melting), adakites (slab melting), oceanic island arc basalts and supra subduction zone peridotites. We developed a new method for the high precision determination of Nb, Ta, Zr, Hf concentrations based on a modified version of standard addition. All analyses were performed on a single collector ICPMS (ELEMENT 1), using Y and Yb as internal standards to correct for instrumental drift during the unspiked -spiked sample sequence. Concentrations are calculated using a York- type regression that accounts for all measured and propagated errors. Long-term reproducibility (multiple dissolutions and multiple spike solutions) for the standards BHVO-1, BIR-1 AGV-1 and BCR-1 are better than 0.8% (1s) for Nb/Ta and Zr/Hf ratios. The advantages of this method compared to previous methods are fast throughput, no column chemistry and low blanks. While the Zr/Hf ratios in subduction-related volcanics and ocean island basalts vary by less than a factor of two, the Nb/Ta ratio varies by a factor of four. Most of the Nb/Ta variation is observed in subduction related rocks. Samples with the highest Nb/Ta ratio (up to 19.5) are adakites from the Austral Volcanic Zone (Andes) which are thought to represent eclogitic melts from subducted oceanic crust which was most likely dehydrated. The lowest Nb/Ta (5) was found in boninites from Chichi-Jima, Bonin Island. Samples from Chichi-Jima and from the

  7. Charge transfer in AuTa alloys: double resonance at the Au and Ta L 2, 3-edge

    NASA Astrophysics Data System (ADS)

    Sammynaiken, R.; Kuhn, M.; Sham, T. K.

    1995-02-01

    Charge redistribution in AuTa alloys has been studied with both Au and Ta L 2, 3-edge XANES for AuTa, AuTa 2 and AuTa 3. Emphasis is placed on the relative intensity of the whiteline which probes the change in d-hole count at both Au and Ta sites. It is found that all Au L 2, 3-edge XANES exhibit an appreciable whiteline of which the intensity increases as Au becomes more dilute in Ta while the Ta L 2, 3-edge whiteline intensity increases also as Ta becomes more dilute. These results are compared with core-level photoemission measurements.

  8. Safety assessment for TA-48 radiochemical operations

    SciTech Connect

    1994-08-01

    The purpose of this report is to document an assessment performed to evaluate the safety of the radiochemical operations conducted at the Los Alamos National Laboratory operations area designated as TA-48. This Safety Assessment for the TA-48 radiochemical operations was prepared to fulfill the requirements of US Department of Energy (DOE) Order 5481.1B, ``Safety Analysis and Review System.`` The area designated as TA-48 is operated by the Chemical Science and Technology (CST) Division and is involved with radiochemical operations associated with nuclear weapons testing, evaluation of samples collected from a variety of environmental sources, and nuclear medicine activities. This report documents a systematic evaluation of the hazards associated with the radiochemical operations that are conducted at TA-48. The accident analyses are limited to evaluation of the expected consequences associated with a few bounding accident scenarios that are selected as part of the hazard analysis. Section 2 of this report presents an executive summary and conclusions, Section 3 presents pertinent information concerning the TA-48 site and surrounding area, Section 4 presents a description of the TA-48 radiochemical operations, and Section 5 presents a description of the individual facilities. Section 6 of the report presents an evaluation of the hazards that are associated with the TA-48 operations and Section 7 presents a detailed analysis of selected accident scenarios.

  9. Field investigations of soils at TA-19, TA-26, TA-73 and TA-0, SWMU aggregate 0-D and 016

    SciTech Connect

    McFadden, L.D.

    1995-03-01

    Field based investigations of the general soil-geomorphic characteristics were carried out at TA-19, -26, -73, -0, Aggregate 0-D and -016 in order to provide information for utilization in ongoing and anticipated LANL ERP (Environmental Restoration Project) activities at these sites. These investigations show that soils exhibiting diverse morphologic character, varying ages, and relations to landforms characterize these sites. A review of recent and ongoing soils studies also shows that soil textural, chemical, and mineralogical characteristics may profoundly influence the migration and/or retardation of a variety of potential contaminants initially placed in direct contact with soils, or that encounter soils during subsurface percolation or discharge. Soil-geomorphic relations also provide important insights into recent site erosion, deposition or other surficial processes that must, be considered as part of environmental assessment of a given site and remediation; and, the planned geomorphic mapping activities at each site, as well as other associated activities (e.g, geophysical survey, site sampling) are accordingly appropriate and necessary with respect to identification of significant soil relations at each site. Specific and general recommendations in consideration of important findings regarding the possible impacts of soil development of the nature of contaminant behavior at various sites are provided to help guide sampling and analysis activities during ERP investigations outlined in the RFI Work Plan for Operational Unit-1071.

  10. Amorphous layer formation at the TaC/Cu interface in the Si/TaC/Cu metallization system

    NASA Astrophysics Data System (ADS)

    Laurila, Tomi; Zeng, Kejun; Kivilahti, Jorma K.; Molarius, Jyrki; Suni, Ilkka

    2002-02-01

    An amorphous Ta(O,C)x layer was found to form at the TaC/Cu interface in the Si/TaC/Cu metallization system. The formation of the layer was induced by oxygen trapped in the as-deposited films, since on the basis of thermodynamic evaluation of the ternary Ta-C-O system, the dissociation of the TaC layer and the formation of the Ta2O5 and graphite can be expected to occur during subsequent annealings in this case. However, as observed experimentally, the formation of the amorphous Ta(O,C)x preceded the formation of the stable tantalum oxide.

  11. Rutile is holding Nb and Ta in the mantle, negligible Nb and Ta in the core

    NASA Astrophysics Data System (ADS)

    McDonough, W. F.; Rudnick, R. L.

    2008-12-01

    Continental Crust has a significant depletion in Nb and Ta relative to La that has been attributed to convergent margin (arc) magmatism and greater retention of Nb and Ta in the mantle source. This depleted pattern is a consequence of the plotting order of elements, which has been established by the relative partitioning behavior of elements during MORB-OIB genesis. It is our hypothesis that rutile in subducting slabs or delaminated lower continental crust is the important phase causing Nb(Ta)-depletion in the continental crust, as well as lowering its Nb/Ta. Experimental studies reveal a range of Nb/Ta fractionation responses in residual rutile depending on temperature and phase relations(melting vs dehydration). Examples of rutile-bearing, refractory eclogites have been identified that serve as analog materials for residues of the continental crust. These rutiles have radiogenic Hf isotopes (Vervoort, unpubl. data), and thus are not recent precipitates from metasomatic melts, as has been recently suggested. What remains is to understand the total silicate Earth's mass balance. In this regard, it is worth noting that early Archean Barbarton komatiites possess chondritic La/Nb ratios, and Nb/Ta ~15, a value comparable to Allende CV3 chondrite. This observation is not consistent with the storage of Nb (or Ta) in the core and suggests that the silicate Earth controls the planetary budget of Nb and Ta. Constraints on the amount of Nb in the core must be evaluated by multi-element approaches, using ratios of refractory lithophile elements. Chondritic ratios for La/Nb and Nb/Ta are not defined simply as a single value with a restricted range and are not always constant, with examples of both negligible and distinct differences between groups of chondrites. The database for chondrites is still small for Nb and Ta.

  12. Thermally stable perpendicular magnetic anisotropy features of Ta/TaO{sub x}/Ta/CoFeB/MgO/W stacks via TaO{sub x} underlayer insertion

    SciTech Connect

    Yang, SeungMo; Lee, JaBin; An, GwangGuk; Kim, JaeHong; Chung, WooSeong; Hong, JinPyo

    2014-09-21

    We report that a TaO{sub x} underlayer enhances the stability of perpendicular magnetic anisotropy (PMA) in TaO{sub x}/Ta/CoFeB/MgO stacks during annealing; control of oxygen content in the TaO{sub x} layer is critical. X-ray photoelectron spectroscopy observations revealed clear suppression of Ta atom diffusion towards the CoFeB/MgO interface or MgO regions. The TaO{sub x} underlayer possibly served as a diffusion sponge, permitting some thermally activated Ta atoms to impregnate the TaO{sub x} underlayer via a diffusion path, such as grain boundaries. We propose a possible mechanism for enhanced PMA stability based on diffusion of thermally activated Ta atoms.

  13. Solid Collection Efforts: Ta Collimator Evaluation

    SciTech Connect

    Gostic, J M

    2011-11-21

    Ta collimator sets that were part of the gated x-ray detector diagnostic (GXD) at NIF were analyzed for debris distribution and damage in 2011. These disks (ranging in thickness from 250 to 750 {mu}m) were fielded approximately 10 cm from target chamber center (TCC) on various symcap, THD and re-emit shots. The nose cone holder and forward Ta collimator (facing target chamber center, TCC) from all shots show evidence of surface melt. Non-destructive analysis techniques such as optical microscopy, surface profilometry, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray fluorescence (XRF) were used to determine debris composition and degree of deformation associated with each Ta disk. Molten debris from the stainless steel nose cone contaminated the surface of the collimators along with other debris associated with the target assembly (Al, Si, Cu, Au and In). Surface elemental analysis of the forward collimator Ta disks indicates that Au hohlraum debris is less concentrated on these samples versus those fielded 50 cm from TCC in the wedge range filter (WRF) assembly. It is possible that the Au is distributed below or within the stainless steel melt layer covering the disk, as most of the foreign debris is captured in the melted coating. The other disks (fielded directly behind the forward collimator in a sandwiched configuration) have visible forms of deformation and warping. The degree of warping increases as the shock wave penetrates the assembly with the most damage sustained on the back collimator. In terms of developing a solid collection capability, the collimator analyses suggests that close proximity may cause more interference with capsule debris collection and more damage to the surface of the collector diagnostic. The analyses of the Ta collimators were presented to the Target and Laser Interaction Sphere (TaLIS) group; a representative presentation is attached to this document.

  14. First-principles studies of Ni-Ta intermetallic compounds

    SciTech Connect

    Zhou Yi; Wen Bin; Ma Yunqing; Melnik, Roderick; Liu Xingjun

    2012-03-15

    The structural properties, heats of formation, elastic properties, and electronic structures of Ni-Ta intermetallic compounds are investigated in detail based on density functional theory. Our results indicate that all Ni-Ta intermetallic compounds calculated here are mechanically stable except for P21/m-Ni{sub 3}Ta and hc-NiTa{sub 2}. Furthermore, we found that Pmmn-Ni{sub 3}Ta is the ground state stable phase of Ni{sub 3}Ta polymorphs. The polycrystalline elastic modulus has been deduced by using the Voigt-Reuss-Hill approximation. All Ni-Ta intermetallic compounds in our study, except for NiTa, are ductile materials by corresponding G/K values and poisson's ratio. The calculated heats of formation demonstrated that Ni{sub 2}Ta are thermodynamically unstable. Our results also indicated that all Ni-Ta intermetallic compounds analyzed here are conductors. The density of state demonstrated the structure stability increases with the Ta concentration. - Graphical abstract: Mechanical properties and formation heats of Ni-Ta intermetallic compounds are discussed in detail in this paper. Highlights: Black-Right-Pointing-Pointer Ni-Ta intermetallic compounds are investigated by first principle calculations. Black-Right-Pointing-Pointer P21/m-Ni{sub 3}Ta and hc-NiTa{sub 2} are mechanically unstable phases. Black-Right-Pointing-Pointer Pmmn-Ni{sub 3}Ta is ground stable phase of Ni{sub 3}Ta polymorphs. Black-Right-Pointing-Pointer All Ni-Ta intermetallic compounds are conducting materials.

  15. TaRAR1 and TaSGT1 associate with TaHsp90 to function in bread wheat (Triticum aestivum L.) seedling growth and stripe rust resistance.

    PubMed

    Wang, Guan-Feng; Fan, Renchun; Wang, Xianping; Wang, Daowen; Zhang, Xiangqi

    2015-04-01

    RAR1 and SGT1 are important co-chaperones of Hsp90. We previously showed that TaHsp90.1 is required for wheat seedling growth, and that TaHsp90.2 and TaHsp90.3 are essential for resistance (R) gene mediated resistance to stripe rust fungus. Here, we report the characterization of TaRAR1 and TaSGT1 genes in bread wheat. TaRAR1 and TaSGT1 each had three homoeologs, which were located on wheat groups 2 and 3 chromosomes, respectively. Strong inhibition of seedling growth was observed after silencing TaSGT1 but not TaRAR1. In contrast, decreasing the expression of TaRAR1 or TaSGT1 could all compromise R gene mediated resistance to stripe rust fungus infection. Protein-protein interactions were found among TaRAR1, TaSGT1 and TaHsp90. The N-terminus of TaHsp90, the CHORD-I and CHORD-II domains of TaRAR1 and the CS domain of TaSGT1 may be instrumental for the interactions among the three proteins. Based on this work and our previous study on TaHsp90, we speculate that the TaSGT1-TaHsp90.1 interaction is important for maintaining bread wheat seedling growth. The TaRAR1-TaSGT1-TaHsp90.2 and TaRAR1-TaSGT1-TaHsp90.3 interactions are involved in controlling the resistance to stripe rust disease. The new information obtained here should aid further functional investigations of TaRAR1-TaSGT1-TaHsp90 complexes in regulating bread wheat growth and disease resistance.

  16. TaRAR1 and TaSGT1 associate with TaHsp90 to function in bread wheat (Triticum aestivum L.) seedling growth and stripe rust resistance.

    PubMed

    Wang, Guan-Feng; Fan, Renchun; Wang, Xianping; Wang, Daowen; Zhang, Xiangqi

    2015-04-01

    RAR1 and SGT1 are important co-chaperones of Hsp90. We previously showed that TaHsp90.1 is required for wheat seedling growth, and that TaHsp90.2 and TaHsp90.3 are essential for resistance (R) gene mediated resistance to stripe rust fungus. Here, we report the characterization of TaRAR1 and TaSGT1 genes in bread wheat. TaRAR1 and TaSGT1 each had three homoeologs, which were located on wheat groups 2 and 3 chromosomes, respectively. Strong inhibition of seedling growth was observed after silencing TaSGT1 but not TaRAR1. In contrast, decreasing the expression of TaRAR1 or TaSGT1 could all compromise R gene mediated resistance to stripe rust fungus infection. Protein-protein interactions were found among TaRAR1, TaSGT1 and TaHsp90. The N-terminus of TaHsp90, the CHORD-I and CHORD-II domains of TaRAR1 and the CS domain of TaSGT1 may be instrumental for the interactions among the three proteins. Based on this work and our previous study on TaHsp90, we speculate that the TaSGT1-TaHsp90.1 interaction is important for maintaining bread wheat seedling growth. The TaRAR1-TaSGT1-TaHsp90.2 and TaRAR1-TaSGT1-TaHsp90.3 interactions are involved in controlling the resistance to stripe rust disease. The new information obtained here should aid further functional investigations of TaRAR1-TaSGT1-TaHsp90 complexes in regulating bread wheat growth and disease resistance. PMID:25697954

  17. Subtleties of structure and bonding in Ta-S-Se and Ta-Nb-S solid solutions

    NASA Astrophysics Data System (ADS)

    Nanjundaswamy, K. S.; Hughbanks, Timothy

    1992-06-01

    Substitution of selenium by sulfur and tantalum by niobium into the 1x[Ta 5Ta] chains characteristic of Ta 3S 2 and Ta 2S is attempted in an effort to understand the structural diversity of a metal-rich chalcogenides. Neither Ta 2S nor Ta 3S 2 incorporates a significant amount of selenium, while Ta 2Se-like structures are found to persist in Ta 2S 1-xSe x for 0.2≤x≤1.0, a and c progressively increasing with x. The Ta 2Se-like structure is stable to annealing at temperatures ≥1000°C for 0.5≤ x≤1.0, and compositions with x≤0.5 disproportionate to Ta 3S 2, Ta 6S, and Ta 1- xSe 2 on annealing. Both our work and research completed in Franzen's laboratories show that niobium substitution into the 1x[Ta 5Ta] chains does not occur to any large extent, instead layered Ta 2Se-like structures ( M4S 2 and M5S 2) are stabilized. At the composition Ta 2- xNb xS ( x=0.6) as-cast samples are virtually single phase, adopting a Ta 2Se-like structure. A single crystal structure determination for a crystal with composition Ta 1.4Nb 0.6S was carried out: space group P4/ nmm (No. 129), a=3.339(1), c=9.089(7) Å, V=101.33(9) Å 3, Z=2. While electronic structure calculations nicely rationalize the metal-metal bonding in any of these structures, the ability to predict which structures will be stabilized for which systems remains out of reach.

  18. Preliminary analysis of EUSO—TA data

    NASA Astrophysics Data System (ADS)

    Fenu, F.; Piotrowski, L. W.; Shin, H.; Jung, A.; Bacholle, S.; Bisconti, F.; Capel, F.; Eser, J.; Kawasaki, Y.; Kuznetsov, E.; Larsson, O.; Mackovjak, S.; Miyamoto, H.; Plebaniak, Z.; Prevot, G.; Putis, M.; Shinozaki, K.; Adams, J.; Bertaina, M.; Bobik, P.; Casolino, M.; Matthews, J. N.; Ricci, M.; Wiencke, L.; EUSO-TA Collaboration

    2016-05-01

    The EUSO-TA detector is a pathfinder for the JEM-EUSO project and is currently installed in Black Rock Mesa (Utah) on the site of the Telescope Array fluorescence detectors. Aim of this experiment is to validate the observation principle of JEM-EUSO on air showers measured from ground. The experiment gets data in coincidence with the TA triggers to increase the likelihood of cosmic ray detection. In this framework the collaboration is also testing the detector response with respect to several test events from lasers and LED flashers. Moreover, another aim of the project is the validation of the stability of the data acquisition chain in real sky condition and the optimization of the trigger scheme for the rejection of background. Data analysis is ongoing to identify cosmic ray events in coincidence with the TA detector. In this contribution we will show the response of the EUSO-TA detector to all the different typologies of events and we will show some preliminary results on the trigger optimization performed on such data.

  19. Engineering Mathematics Assessment Using "MapleTA"

    ERIC Educational Resources Information Center

    Jones, Ian S.

    2008-01-01

    The assessment of degree level engineering mathematics students using the computer-aided assessment package MapleTA is discussed. Experience of academic and practical issues for both online coursework and examination assessments is presented, hopefully benefiting other academics in this novel area of activity. (Contains 6 figures and 1 table.)

  20. Adhesion and reliability of copper interconnects with Ta and TaN barrier layers

    SciTech Connect

    Lane, Michael; Dauskardt, Reinhold H.; Krishna, Nety; Hashim, Imran

    2000-01-01

    With the advent of copper metallization in interconnect structures, new barrier layers are required to prevent copper diffusion into adjacent dielectrics and the underlying silicon. The barrier must also provide adequate adhesion to both the dielectric and copper. While Ta and TaN barrier layers have been incorporated for these purposes in copper metallization schemes, little quantitative data exist on their adhesive properties. In this study, the critical interface fracture energy and the subcritical debonding behavior of ion-metal-plasma sputtered Ta and TaN barrier layers in Cu interconnect structures were investigated. Specifically, the effects of interfacial chemistry, Cu layer thickness, and oxide type were examined. Behavior is rationalized in terms of relevant reactions at the barrier/dielectric interface and plasticity in adjacent metal layers. (c) 2000 Materials Research Society.

  1. Silicide formation process of Er films with Ta and TaN capping layers.

    PubMed

    Choi, Juyun; Choi, Seongheum; Kim, Jungwoo; Na, Sekwon; Lee, Hoo-Jeong; Lee, Seok-Hee; Kim, Hyoungsub

    2013-12-11

    The phase development and defect formation during the silicidation reaction of sputter-deposited Er films on Si with ∼20-nm-thick Ta and TaN capping layers were examined. TaN capping effectively prevented the oxygen incorporation from the annealing atmosphere, which resulted in complete conversion to the ErSi2-x phase. However, significant oxygen penetration through the Ta capping layer inhibited the ErSi2-x formation, and incurred the growth of several Er-Si-O phases, even consuming the ErSi2-x layer formed earlier. Both samples produced a number of small recessed defects at an early silicidation stage. However, large rectangular or square-shaped surface defects, which were either pitlike or pyramidal depending on the capping layer identity, were developed as the annealing temperature increased. The origin of different defect generation mechanisms was suggested based on the capping layer-dependent silicidation kinetics.

  2. Roles of TaON and Ta(3)N(5) in the visible-Fenton-like degradation of atrazine.

    PubMed

    Du, Yingxun; Zhao, Lu; Zhang, Yuanyuan

    2014-02-28

    In this study, the roles of TaON and Ta3N5 in the degradation of atrazine by the visible-Fenton-like system were examined in detail. The TaON and Ta3N5 samples prepared by the nitridation of Ta2O5 and characterized by XRD, DRS, BET and PL analyses. The results showed that the TaON sample had weaker absorption in the visible region but higher specific surface area than the Ta3N5 sample. The degradation rate of atrazine in visible-TaON-Fenton-like system was 2.64 times than that in visible-Ta3N5-Fenton-like system. Both Fe(2+) and H2O2 could be reduced by eCB (electrons in the conduction band) in TaON or Ta3N5, while atrazine could not be oxidized by hVB (holes in the valance band). OH is the active species for the degradation of atrazine in visible-TaON/Ta3N5-Fenton-like systems. Majority of OH originated from Fenton reaction. After Fe(3+) was reduced by eCB to Fe(2+), Fe(2+) reacted quickly with H2O2 to generate OH. In addition, by capturing eCB, a little of H2O2 was reduced to yield OH, which contributed a small fraction of atrazine degradation. Based on the experimental results, the roles of TaON and Ta3N5 in the visible-Fenton-like system were proposed. And the higher photocatalytic activity of TaON than Ta3N5 was suggested to be due to the higher separation efficiency of electrons and holes, which may be related to the larger specific surface area. PMID:24413052

  3. Graphene-Modified Interface Controls Transition from VCM to ECM Switching Modes in Ta/TaOx Based Memristive Devices.

    PubMed

    Lübben, Michael; Karakolis, Panagiotis; Ioannou-Sougleridis, Vassilios; Normand, Pascal; Dimitrakis, Panagiotis; Valov, Ilia

    2015-10-28

    By modification of the electrode-solid-electrolyte interface with graphene, transit from valence change memories (VCM) to electrochemical metallization memories (ECM) in the cell Ta(C)/Ta2 O5 /Pt is demonstrated, thus, bridging both mechanisms. The ECM operation is discussed in the light of Ta-cation mobility in TaOx . The crucial role of electrochemical processes and moisture in the resistive switching process is also highlighted.

  4. Atomically engineering Cu/Ta interfaces.

    SciTech Connect

    Webb, Edmund Blackburn, III; Zhou, Xiao Wang

    2007-09-01

    This report summarizes the major research and development accomplishments for the late start LDRD project (investment area: Enable Predictive Simulation) entitled 'Atomically Engineering Cu/Ta Interfaces'. Two ultimate goals of the project are: (a) use atomistic simulation to explore important atomistic assembly mechanisms during growth of Cu/Ta multilayers; and (b) develop a non-continuum model that has sufficient fidelity and computational efficiency for use as a design tool. Chapters 2 and 3 are essentially two papers that address respectively these two goals. In chapter 2, molecular dynamics simulations were used to study the growth of Cu films on (010) bcc Ta and Cu{sub x}Ta{sub 1-x} alloy films on (111) fcc Cu. The results indicated that fcc crystalline Cu films with a (111) texture are always formed when Cu is grown on Ta. The Cu films are always polycrystalline even when the Ta substrate is single crystalline. These polycrystalline films are composed of grains with only two different orientations, which are separated by either orientational grain boundaries or misfit dislocations. Periodic misfit dislocations and stacking fault bands are observed. The Cu film surface roughness was found to decrease with increasing adatom energy. Due to a Cu surface segregation effect, the Cu{sub x}Ta{sub 1-x} films deposited on Cu always have a higher Cu composition than that used in the vapor mixture. When Cu and Ta compositions in the films are comparable, amorphous structures may form. The fundamental origins for all these phenomena have been studied in terms of crystallography and interatomic interactions. In chapter 3, a simplified computational method, diffusional Monte Carlo (dMC) method, was developed to address long time kinetic processes of materials. Long time kinetic processes usually involve material transport by diffusion. The corresponding microstructural evolution of materials can be analyzed by kinetic Monte Carlo simulation methods, which essentially

  5. Direct Electrolytic Reduction of Solid Ta2O5 to Ta with SOM Process

    NASA Astrophysics Data System (ADS)

    Chen, Chaoyi; Yang, Xiaqiong; Li, Junqi; Lu, Xionggang; Yang, Shufeng

    2016-06-01

    A process that uses the solid-oxide-oxygen-ion conducting membrane has been investigated to produce tantalum directly from solid Ta2O5 in molten CaCl2 or a molten mixture of 55.5MgF2-44.5CaF2 (in wt pct). The sintered porous Ta2O5 pellet was employed as the cathode, while the liquid copper alloy, saturated with graphite powder and encased in a one-end-closed yttria-stabilized-zirconia (YSZ) tube, acted as the anode. The electrolysis potential in this method is higher than that of the Fray-Farthing-Chen Cambridge process because the YSZ membrane tube blocks the melts to electrolyze, and only Ta2O5 is will be electrolyzed. The microstructures of reduced pellets and a cyclic voltammogram of solid Ta2O5 in molten CaCl2 were analyzed. In addition, the influence of particle size and porosity of the cathode pellets on metal-oxide-electrolyte, three-phase interlines was also discussed. The results demonstrate that the sintering temperature of cathode pellets and electrolytic temperature play important roles in the electrochemical process. Furthermore, this process can be used to produce Ta metal efficiently without the expensive cost of pre-electrolysis and generation of harmful by-products.

  6. New insights into the initial stages of Ta oxide nanotube formation on polycrystalline Ta electrodes.

    PubMed

    El-Sayed, Hany A; Horwood, Corie A; Abhayawardhana, Anusha D; Birss, Viola I

    2013-02-21

    Ta oxide nanotubes (NTs) were formed by the anodization of Ta at 15 V in a solution of concentrated sulfuric acid containing 0.8-1.0 M hydrofluoric acid. To study the initial stages of NT formation, FESEM images of samples anodized for very short times were obtained. The results contradict the existing explanation of the current-time data collected during anodization, which has persisted in the literature for more than two decades. In addition to providing a first-time morphological study of Ta oxide NT formation at very early stages of anodization, we also propose a new interpretation of the i-t response, showing that pores are already present in the first few milliseconds of anodization and that NTs are formed well before present models predict. This behaviour may also extend to the anodization of other valve metals, such as Al, Ti, Zr, W, and Nb. PMID:23338813

  7. Comparative mutagenicity of nitrofluoranthenes in Salmonella typhimurium TA98, TA98NR, and TA98/1,8DNP6.

    PubMed

    Shane, B S; Squadrito, G L; Church, D F; Pryor, W A

    1991-01-01

    The nitration of fluoranthene, one of the most abundant polycyclic aromatic hydrocarbons (PAH) in diesel fuels, occurs in the laboratory under either electrophilic or free-radical conditions to give nitro-PAH. 3-Nitrofluoranthene (3-NF) is the major product under electrophilic ionic conditions while 2-nitrofluoranthene (2-NF) is the major product under free-radical nitration conditions. The free-radical nitration of fluoranthene also yields 1,2- and 1,3-dinitrofluoranthene (1,2-DNF and 1,3-DNF). Nitration on the 3-position of fluoranthene enhances the mutagenic potency more strongly than on the 2-position. Thus, 3-NF is a more potent mutagen than 2-NF and 1,3-DNF is more potent than 1,2-DNF, an isomer with one near coplanar nitro group and one nitro group substantially out of plane with the fluoranthene skeleton, when tested against Salmonella typhimurium TA98, TA98NR, and TA98/1,8-DNP6. In addition, the activation of these dinitro-PAH to mutagens does not depend on the "classical nitroreductase" and/or O-acetylase, suggesting that they are activated via different pathways. Despite the fact that 3-NF and 1-phenyl-4-nitronaphthalene (1-P-4NN), a non-planar analog of 3-NF, have virtually identical reduction potentials, their mutagenic potencies differ by three orders of magnitude. This finding suggests that when nitro-PAH of varying steric requirements are compared, the reduction potential may not predict mutagenic potency as well as had been previously suggested.

  8. Failure mechanism of Ta diffusion barrier between Cu and Si

    NASA Astrophysics Data System (ADS)

    Laurila, Tomi; Zeng, Kejun; Kivilahti, Jorma K.; Molarius, Jyrki; Suni, Ilkka

    2000-09-01

    The reaction mechanisms in the Si/Ta/Cu metallization system and their relation to the microstructure of thin films are discussed on the basis of experimental results and the assessment of the ternary Si-Ta-Cu phase diagram at 700 °C. With the help of sheet resistance measurements, Rutherford backscattering spectroscopy, x-ray diffraction, a scanning electron microscope, and a transmission electron microscope, the Ta barrier layer was observed to fail at temperatures above 650 °C due to the formation of TaSi2, the diffusion of Cu through the silicide layer, and the resulting formation of Cu3Si precipitates. However, in order for the TaSi2 phase to form first, the Ta diffusion barrier layer must be thick enough (e.g., 50-100 nm) to prevent Cu diffusion into the Si substrate up to the temperature of TaSi2 formation (˜650 °C). Independent of the Ta layer thickness, Cu3Si was present as large nodules, whereas the TaSi2 existed as a uniform layer. The resulting reaction structure was found to be in local equilibrium on the basis of the assessed Si-Ta-Cu phase diagram at 700 °C, and therefore no further reactions were expected. The role of oxygen was also found to be important in the reactions and it seems to have a strong effect on the thermal stability of the barrier layer.

  9. Paleoclimate from Tree Rings of Picea morrisonicola in Ta-Ta-Chia Area of Central Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, T.; Wright, W. E.; Wei, K.; Cook, E. R.

    2009-12-01

    Almost no dendrochronology has been reported internationally from Taiwan, despite the existence of many dendrochronologically appropriate tree species. In this study, we reconstruct the regional paleoclimate using a multi-century tree ring-width chronology developed from Picea morrisonicola ( the endemic Taiwan Spruce), a subtropical species growing in the Ta-Ta-Chia subalpine mountain areas of central Taiwan. Picea morrisonicola in Taiwan is the only member of the Picea genus whose distribution crosses the Tropic of Cancer. Statistical analysis of the climate signal demonstrates that both the temperature and precipitation have significant effects on tree growth.

  10. TA-2 Water Boiler Reactor Decommissioning Project

    SciTech Connect

    Durbin, M.E.; Montoya, G.M.

    1991-06-01

    This final report addresses the Phase 2 decommissioning of the Water Boiler Reactor, biological shield, other components within the biological shield, and piping pits in the floor of the reactor building. External structures and underground piping associated with the gaseous effluent (stack) line from Technical Area 2 (TA-2) Water Boiler Reactor were removed in 1985--1986 as Phase 1 of reactor decommissioning. The cost of Phase 2 was approximately $623K. The decommissioning operation produced 173 m{sup 3} of low-level solid radioactive waste and 35 m{sup 3} of mixed waste. 15 refs., 25 figs., 3 tabs.

  11. Development of W-Ta generator

    NASA Technical Reports Server (NTRS)

    1981-01-01

    This research program was used to further develop the existing W-Ta generator and to evaluate alternative adsorbents, preferably inorganic materials, as supports for the generator. During the first half year, combinations of non-complexing eluents and a variety of adsorbents, both inorganic and organic, were evaluated. Some of these adsorbents were synthetic, such as chelate resins that could be specific for tungsten. In the second half of the year, the stress was mainly on the use of complexing eluents because of the high affinity of hydrous oxides for tantalum, on the synthesis of chelate resins and on the use novel techniques (electrolytic) to solve the tantalum-adsorption problem.

  12. Hydrogen distribution in Nb/Ta superlattices.

    PubMed

    Wolff, Max; Pálsson, Gunnar K; Korelis, Panagiotis T; Dura, Joseph A; Majkrzak, Charles; Hjörvarsson, Björgvin

    2012-06-27

    The distribution of hydrogen in Nb/Ta superlattices has been investigated by combined neutron reflectivity and x-ray scattering. We provide evidence to support that strain modulations determined with x-ray diffraction can be interpreted as modulations in hydrogen content. We show that the hydrogen concentration is modulated and favors Nb, in agreement with previous studies. We measure the concentration directly using neutron reflectivity and demonstrate no detectable change in the distribution of hydrogen with temperature, in stark contrast to previous studies.

  13. Ramp wave stress-density measurements of Ta and W

    SciTech Connect

    Eggert, J.; Bastea, M.; Reisman, D. B.; Erskine, D.; Collins, G. W.; Rothman, S.; Davis, J.-P.; Knudson, M. D.; Hayes, D. B.; Gray, G. T. III

    2007-12-12

    Stress-density ({sigma}-{rho}) loading paths of both Ta and W under ramped compression were measured up to 300 GPa. For similar ramp loading conditions, {sigma}({rho}) for Ta lies close to the cold curve and significantly below the Hugoniot, while {sigma}({rho}) for W lies close to the Hugoniot and significantly above the cold curve. The elastic yield limit is reported for W and Ta with thicknesses 400-700 {mu}m.

  14. Partial splenic resection using the TA-stapler.

    PubMed

    Uranüs, S; Kronberger, L; Kraft-Kine, J

    1994-07-01

    Since 1987, we have used the TA-stapler for 15 partial resections of the spleen. The cases included 5 second- to third-degree traumatic ruptures, 4 splenic cysts, 3 injuries resulting from accidents during upper-abdominal surgery, 2 diagnostic resections, and 1 intralienal pancreatic cyst. The TA-55 stapler was used 14 times and the TA-90 once. No patient developed postoperative bleeding or required further surgery. Postoperative laboratory chemistry and scintigraphy findings were within the limits indicative of normal function in all cases. The TA-stapler expands the technical possibilities for organ-conserving splenic surgery.

  15. 75 FR 43556 - TA-W-73,381, MT Rail Link, Inc., Missoula, MT; TA-W-73,381A, Billings, MT; TA-W-73,381B, Laurel...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-26

    ... Employment and Training Administration TA-W-73,381, MT Rail Link, Inc., Missoula, MT; TA-W-73,381A, Billings, MT; TA-W-73,381B, Laurel, MT; TA-W-73,381C, Livingston, MT; TA-W-73,381D, Helena, MT; Amended... in the Federal Register on July 7, 2010 (75 FR 39049). At the request of the State Agency,...

  16. Lecture Discourse of a Foreign TA: A Preliminary Needs Assessment.

    ERIC Educational Resources Information Center

    Gillette, Susan

    1982-01-01

    A study of the communication skill needs of the foreign teaching associate (TA) in American universities focused on two questions: (1) What does a foreign TA do to communicate information in an American classroom in terms of comunication strategies and devices for cohesion and coherence of discourse? and (2) How does this compare with the way an…

  17. TA-59 North Parking Lot and Pajarito Road Corridor Analysis

    SciTech Connect

    Not Available

    1993-12-01

    The purpose of this report is to provide traffic engineering services for the TA-59 North Parking Lot/Pajarito Road corridor Analysis at Los Alamos National Laboratory. The following tasks were accomplished to assess the development of the north parking lot and Pajarito Road in the vicinity of TA-59: conducted turning-movement counts from 7 AM to 9 AM and from 4 PM to 6 PM at the Pajarito Road/TA-59 intersection; conducted a parking supply and demand survey for all the parking lots within TA-59 on half-hour intervals between 0600--1800 (6 AM to 6 PM); conducted mid-day directional speed study along Pajarito Road, just east or south of the TA-59/Pajarito Road intersection; conducted peak hour gap study on Pajarito Road in the vicinity of TA-59; reviewed the TA-59 Parking Lot North of Pajarito Road, FY-94 Weapons GPP Short List Candidate {number_sign}9 report and other documents pertaining to past transportation studies; reassigned current turning-movement volumes with a 100 space parking lot being built on the north side of Pajarito Road; prepared traffic projections for the Pajarito Road/TA-59 intersection according to the proposed development on the north side of Pajarito Road that would employee 246 people; and assigned pedestrian crossing volumes between the northern lot/future development site and areas south of Pajarito Road.

  18. Characterization and Modeling of Nonfilamentary Ta/TaOx/TiO2/Ti Analog Synaptic Device.

    PubMed

    Wang, Yu-Fen; Lin, Yen-Chuan; Wang, I-Ting; Lin, Tzu-Ping; Hou, Tuo-Hung

    2015-01-01

    A two-terminal analog synaptic device that precisely emulates biological synaptic features is expected to be a critical component for future hardware-based neuromorphic computing. Typical synaptic devices based on filamentary resistive switching face severe limitations on the implementation of concurrent inhibitory and excitatory synapses with low conductance and state fluctuation. For overcoming these limitations, we propose a Ta/TaOx/TiO2/Ti device with superior analog synaptic features. A physical simulation based on the homogeneous (nonfilamentary) barrier modulation induced by oxygen ion migration accurately reproduces various DC and AC evolutions of synaptic states, including the spike-timing-dependent plasticity and paired-pulse facilitation. Furthermore, a physics-based compact model for facilitating circuit-level design is proposed on the basis of the general definition of memristor devices. This comprehensive experimental and theoretical study of the promising electronic synapse can facilitate realizing large-scale neuromorphic systems. PMID:25955658

  19. Characterization and Modeling of Nonfilamentary Ta/TaOx/TiO2/Ti Analog Synaptic Device

    PubMed Central

    Wang, Yu-Fen; Lin, Yen-Chuan; Wang, I-Ting; Lin, Tzu-Ping; Hou, Tuo-Hung

    2015-01-01

    A two-terminal analog synaptic device that precisely emulates biological synaptic features is expected to be a critical component for future hardware-based neuromorphic computing. Typical synaptic devices based on filamentary resistive switching face severe limitations on the implementation of concurrent inhibitory and excitatory synapses with low conductance and state fluctuation. For overcoming these limitations, we propose a Ta/TaOx/TiO2/Ti device with superior analog synaptic features. A physical simulation based on the homogeneous (nonfilamentary) barrier modulation induced by oxygen ion migration accurately reproduces various DC and AC evolutions of synaptic states, including the spike-timing-dependent plasticity and paired-pulse facilitation. Furthermore, a physics-based compact model for facilitating circuit-level design is proposed on the basis of the general definition of memristor devices. This comprehensive experimental and theoretical study of the promising electronic synapse can facilitate realizing large-scale neuromorphic systems. PMID:25955658

  20. Characterization and Modeling of Nonfilamentary Ta/TaOx/TiO2/Ti Analog Synaptic Device

    NASA Astrophysics Data System (ADS)

    Wang, Yu-Fen; Lin, Yen-Chuan; Wang, I.-Ting; Lin, Tzu-Ping; Hou, Tuo-Hung

    2015-05-01

    A two-terminal analog synaptic device that precisely emulates biological synaptic features is expected to be a critical component for future hardware-based neuromorphic computing. Typical synaptic devices based on filamentary resistive switching face severe limitations on the implementation of concurrent inhibitory and excitatory synapses with low conductance and state fluctuation. For overcoming these limitations, we propose a Ta/TaOx/TiO2/Ti device with superior analog synaptic features. A physical simulation based on the homogeneous (nonfilamentary) barrier modulation induced by oxygen ion migration accurately reproduces various DC and AC evolutions of synaptic states, including the spike-timing-dependent plasticity and paired-pulse facilitation. Furthermore, a physics-based compact model for facilitating circuit-level design is proposed on the basis of the general definition of memristor devices. This comprehensive experimental and theoretical study of the promising electronic synapse can facilitate realizing large-scale neuromorphic systems.

  1. Characterization and Modeling of Nonfilamentary Ta/TaOx/TiO2/Ti Analog Synaptic Device.

    PubMed

    Wang, Yu-Fen; Lin, Yen-Chuan; Wang, I-Ting; Lin, Tzu-Ping; Hou, Tuo-Hung

    2015-01-01

    A two-terminal analog synaptic device that precisely emulates biological synaptic features is expected to be a critical component for future hardware-based neuromorphic computing. Typical synaptic devices based on filamentary resistive switching face severe limitations on the implementation of concurrent inhibitory and excitatory synapses with low conductance and state fluctuation. For overcoming these limitations, we propose a Ta/TaOx/TiO2/Ti device with superior analog synaptic features. A physical simulation based on the homogeneous (nonfilamentary) barrier modulation induced by oxygen ion migration accurately reproduces various DC and AC evolutions of synaptic states, including the spike-timing-dependent plasticity and paired-pulse facilitation. Furthermore, a physics-based compact model for facilitating circuit-level design is proposed on the basis of the general definition of memristor devices. This comprehensive experimental and theoretical study of the promising electronic synapse can facilitate realizing large-scale neuromorphic systems.

  2. Microstructural and weldability evaluation of 310TaN

    SciTech Connect

    Lundin, C.D.; Qiao, C.Y.P.; Swindeman, R.W.

    1996-08-01

    Excellent weldability and good microstructural stability of 310TaN, in terms of the formation and growth of secondary phases at elevated temperature, was revealed in this investigation. The interganular stress corrosion resistance of 310TaN is superior to modified 800H and 310HCbN evaluated previously due to the fact that TaC, TaN and Ta(C,N) particles are more stable compared to Nb-rich or Ti-rich carbides, nitrides and carbonitrides presented in the other advanced alloys. Using resistance spot welding technique for which extremely fast cooling is a characteristic, it was found that a very minor amount of gain boundary liquation takes place during welding thermal cycling. The limited grain boundary liquation is of the eutectic type i.e., a low tendency to weld HAZ hot cracking.

  3. 77 FR 64827 - Investigation Nos. 701-TA-402 and 731-TA-892 (Second Review); Honey From Argentina; Termination...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-23

    ... party responded to the sunset review notice of initiation by the applicable deadline (77 FR 58524... COMMISSION Investigation Nos. 701-TA-402 and 731-TA-892 (Second Review); Honey From Argentina; Termination of... countervailing duty order and antidumping duty order on imports of honey from Argentina would be likely to...

  4. O-GlcNAc-mediated interaction between VER2 and TaGRP2 elicits TaVRN1 mRNA accumulation during vernalization in winter wheat

    PubMed Central

    Xiao, Jun; Xu, Shujuan; Li, Chunhua; Xu, Yunyuan; Xing, Lijing; Niu, Yuda; Huan, Qing; Tang, Yimiao; Zhao, Changping; Wagner, Doris; Gao, Caixia; Chong, Kang

    2014-01-01

    Vernalization, sensing of prolonged cold, is important for seasonal flowering in eudicots and monocots. While vernalization silences a repressor (FLC, MADS-box transcription factor) in eudicots, it induces an activator (TaVRN1, an AP1 clade MADS-box transcription factor) in monocots. The mechanism for TaVRN1 induction during vernalization is not well understood. Here we reveal a novel mechanism for controlling TaVRN1 mRNA accumulation in response to prolonged cold sensing in wheat. The carbohydrate-binding protein VER2, a jacalin lectin, promotes TaVRN1 upregulation by physically interacting with the RNA-binding protein TaGRP2. TaGRP2 binds to TaVRN1 pre-mRNA and inhibits TaVRN1 mRNA accumulation. The physical interaction between VER2 and TaGRP2 is controlled by TaGRP2 O-GlcNAc modification, which gradually increases during vernalization. The interaction between VER2 and O-GlcNAc-TaGRP2 reduces TaGRP2 protein accumulation in the nucleus and/or promotes TaGRP2 dissociation from TaVRN1, leading to TaVRN1 mRNA accumulation. Our data reveal a new mechanism for sensing prolonged cold in temperate cereals. PMID:25091017

  5. Silver delafossite nitride, AgTaN{sub 2}?

    SciTech Connect

    Miura, Akira; Lowe, Michael; Leonard, Brian M.; Subban, Chinmayee V.; Masubuchi, Yuji; Kikkawa, Shinichi; Dronskowski, Richard; Hennig, Richard G.; Abruna, Hector D.; DiSalvo, Francis J.

    2011-01-15

    A new silver nitride, AgTaN{sub 2}, was synthesized from NaTaN{sub 2} by a cation-exchange reaction, using a AgNO{sub 3}-NH{sub 4}NO{sub 3} flux at 175 {sup o}C. Its crystal structure type is delafossite (R3-bar m) with hexagonal lattice parameters of a=3.141(3) A, c=18.81(2) A, in which silver is linearly coordinated to nitrogen. Energy dispersive X-ray analysis and combustion nitrogen/oxygen analysis gave a composition with atomic ratios of Ag:Ta:N:O as 1.0:1.2(1):2.1(1):0.77(4), which is somewhat Ta rich and indicates some oxide formation. The X-ray photoelectron spectroscopy analysis showed a Ta- and O-rich surface and transmission electron microscope observation exhibited aggregates of ca. 4-5 nm-sized particles on the surface, which are probably related to the composition deviation from a AgTaN{sub 2}. The lattice parameters of stoichiometric AgTaN{sub 2} calculated by density functional theory agree with the experimental ones, but the possibility of some oxygen incorporation and/or silver deficiency is not precluded. -- Graphical abstract: A delafossite silver nitride, AgTaN{sub 2}, was synthesized from NaTaN{sub 2} by a cation-exchange reaction using a AgNO{sub 3}-NH{sub 4}NO{sub 3} flux. It contains N-Ag-N linear bonding. Display Omitted

  6. Magnetism of Ta dichalcogenide monolayers tuned by strain and hydrogenation

    NASA Astrophysics Data System (ADS)

    Manchanda, Priyanka; Sharma, Vinit; Yu, Hongbin; Sellmyer, D. J.; Skomski, Ralph

    2015-07-01

    The effects of strain and hydrogenation on the electronic, magnetic, and optical properties of monolayers of Ta based dichalcogenides (TaX2; X = S, Se, and Te) are investigated using density-functional theory. We predict a complex scenario of strain-dependent magnetic phase transitions involving paramagnetic, ferromagnetic, and modulated antiferromagnetic states. Covering one of the two chalcogenide surfaces with hydrogen switches the antiferromagnetic/nonmagnetic TaX2 monolayers to a semiconductor, and the optical behavior strongly depends on strain and hydrogenation. Our research opens pathways towards the manipulation of magnetic as well as optical properties for future spintronics and optoelectronics applications.

  7. Magnetism of Ta dichalcogenide monolayers tuned by strain and hydrogenation

    SciTech Connect

    Manchanda, Priyanka; Sellmyer, D. J.; Skomski, Ralph; Sharma, Vinit; Yu, Hongbin

    2015-07-20

    The effects of strain and hydrogenation on the electronic, magnetic, and optical properties of monolayers of Ta based dichalcogenides (TaX{sub 2}; X = S, Se, and Te) are investigated using density-functional theory. We predict a complex scenario of strain-dependent magnetic phase transitions involving paramagnetic, ferromagnetic, and modulated antiferromagnetic states. Covering one of the two chalcogenide surfaces with hydrogen switches the antiferromagnetic/nonmagnetic TaX{sub 2} monolayers to a semiconductor, and the optical behavior strongly depends on strain and hydrogenation. Our research opens pathways towards the manipulation of magnetic as well as optical properties for future spintronics and optoelectronics applications.

  8. Thermodynamic properties of two metal-rich tantalum sulfides: Ta/sub 2/S and Ta/sub 6/S

    SciTech Connect

    Harbrecht, B.U.; Schmidt, S.R.; Franzen, H.F.

    1984-06-01

    The incongruent vaporization reactions of Ta/sub 2/S and Ta/sub 6/S have been investigated by mass-loss effusion in the temperature range 1576 to 1902 K. By extrapolation of P/sub s/(obs) to equilibrium the enthalpies of the reactions 3/2 Ta/sub 2/S(s) = 1/2 Ta/sub 6/S (S) + S(g) and Ta/sub 6/S = 6 Ta(s) + S(g) wee found to be ..delta..H/sub 29//sup 80//R = 53.9(0.3) X 10/sup 3/ K and ..delta..H/sub 298//sup 0//R = 58.1(0.4) X 10/sup 3/ K, respectively. Comparison between the above values, determined by a 2nd law treatment, and 3rd law values was used to derive fef (free energy function) values for Ta and S in the compounds. These postulated fef's, which apply only to the elements as present in the compounds measured, are compared to tabulated quantities for the pure solid elements to provide a criterion for 2nd and 3rd law evaluation.

  9. Electronic structure of the bcc transition metals: Thermoreflectance studies of bulk V, Nb, Ta, and αTaHx

    NASA Astrophysics Data System (ADS)

    Rosei, R.; Colavita, E.; Franciosi, A.; Weaver, J. H.; Peterson, D. T.

    1980-04-01

    Thermoreflectance studies of bulk samples of V, Nb, Ta, and α-phase TaHx are reported and the results interpreted in terms of recent band calculations. The first interband transition is identified as a transition involving the Σ band at EF. An M3 critical-point transition is attributed to states at N. Significant changes induced by interstitial hydrogen in solid solution α-TaHx are observed and interpreted as due to hybridization and lowering of the N1 eigenenergy.

  10. Targeted disruption of the gene encoding the classical nitroreductase enzyme in Salmonella typhimurium Ames test strains TA1535 and TA1538.

    PubMed

    Yamada, M; Espinosa-Aguirre, J J; Watanabe, M; Matsui, K; Sofuni, T; Nohmi, T

    1997-04-14

    The gene encoding the 'classical nitroreductase' (CNR) of Salmonella typhimurium was disrupted. In this manner, cnr null mutant derivatives of strains TA1535 and TA1538 were constructed, and named YG7131 and YG7127, respectively. In both strain backgrounds, cnr gene disruption reduced nitrofurazone-reductase activity. This reduction almost completely eliminated the nitroreductase activity of strain TA1538. In contrast, the nitroreductase activity of strain TA1535 was much higher than that in TA1538. In this background, cnr gene disruption resulted in a reduction in nitroreductase activity by a similar absolute amount as in TA1538, but representing only about one-quarter of the original activity of TA1535. The results suggest that S. typhimurium has originally at least two distinct nitroreductases, one of which is already deficient in strain TA1538; the CNR is present in both TA1535 and TA1538. Also, these two strains (including their derivatives, TA98 and TA100) are not isogenic with regard to nitroreductase activity. After the introduction of plasmid pKM101, the sensitivities of the strains YG7132 and YG7128, the cnr-null mutants of TA98 and TA100, respectively, against several nitro compounds were compared with those of the conventional cnr-deficient strains TA98NR and TA100NR and the wild-type strains TA98 and TA100. The mutagenicities of 2-nitrofluorene and 1-nitropyrene in YG7132 or TA98NR were ten-fold lower than those of the compounds in TA98. Similarly, the mutagenicity of 2-(2-furyl)-3-(5-nitro-2-furyl) acrylamide in strain YG7128 or TA100NR was substantially lower than that of the compound in TA100. However, the mutagenicity of 2-nitronaphthalene in YG7128 was between those observed with TA100 and TA100NR, suggesting that a nitroreductase in S. typhimurium other than CNR is involved in the metabolic activation of this compound. The cnr gene of S. typhimurium positively hybridized with DNA at 13 min on the E. coli chromosome where the nfsB and nfnB genes

  11. Interfacial dynamnics at sliding Ta/Al interfaces

    NASA Astrophysics Data System (ADS)

    Hammerberg, J. E.; Ravelo, R.; Holian, B. L.; Germann, T. C.; Olson, C. J.

    2002-03-01

    We present results of large-scale MD simulations of sliding Al(100)/Ta(100) interfaces at high shearing velocties. The Ta and Al interactions are modeled using EAM potentials. We discuss the structural evolution near the interface and compare our results with known 2-dimensional simulations which make use of Lennard-Jones potentials but in similar scaled-velocity regimes, namely, 0.01

  12. Oxygen enhancement ratio for d(800) + (Be + Ta) and d(800) + (Ta + Be) neutrons

    SciTech Connect

    Harrison, G.H.; Balcer-Kubiczek, E.K.

    1980-07-01

    Specialized experiments were performed to determine whether the neutron oxygen enhancement ratio (OER) changes significantly as the mean energy increases above 25 MeV. The experimental design called for OER measurements at two energies in the same experiment. The neutron production reaction d(80) + (Be + Ta) generated a beam with mean energy 38 MeV; upon rotation of the target, d(80) + (Ta + Be) neutrons were generated with mean energy 25 MeV. Suspensions of the bacterium Serratia marcesens were irradiated in oxic-hypoxic pairs, alternately with high- and lower-energy neutrons. Replicate experiments yielded OER values and 95% confidence limits of 2.25 (2.05, 2.50) at 25 MeV and 1.67 (1.57, 1.79) at 38 MeV. The x-ray OER was 3.3 (3.1, 3.5). The significant decrease in OER supports our results with Vicia faba showing OER values of 1.7, 1.4, and 2.6 for 25- and 38-MeV neutrons and for x rays, respectively. The yield of spallation products with mass number 6, 7, 9, 10, and 11 arising from neutrons interacting in tissue was analyzed. The tissue kerma from such product contribute kerma equal to 15 to 30% of the recoil proton kerma and thus may provide the physical basis for the observed OER reduction at high neutron energies.

  13. Pre-Test Analysis Predictions for the Shell Buckling Knockdown Factor Checkout Tests - TA01 and TA02

    NASA Technical Reports Server (NTRS)

    Thornburgh, Robert P.; Hilburger, Mark W.

    2011-01-01

    This report summarizes the pre-test analysis predictions for the SBKF-P2-CYL-TA01 and SBKF-P2-CYL-TA02 shell buckling tests conducted at the Marshall Space Flight Center (MSFC) in support of the Shell Buckling Knockdown Factor (SBKF) Project, NASA Engineering and Safety Center (NESC) Assessment. The test article (TA) is an 8-foot-diameter aluminum-lithium (Al-Li) orthogrid cylindrical shell with similar design features as that of the proposed Ares-I and Ares-V barrel structures. In support of the testing effort, detailed structural analyses were conducted and the results were used to monitor the behavior of the TA during the testing. A summary of predicted results for each of the five load sequences is presented herein.

  14. Effect of Ta concentration on the refractive index of TiO2:Ta studied by spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Nurfani, Eka; Kurniawan, Robi; Muhammady, Shibghatullah; Marlina, Resti; Sutjahja, Inge M.; Winata, Toto; Rusydi, Andrivo; Darma, Yudi

    2016-04-01

    We have investigated optical properties of Ta-doped TiO2 thin film on LaAlO3 (LAO) substrate using Spectroscopic Ellipsometry (SE) at room temperature. Amplitude ratio Ψ and phase difference L1 between p- and s- polarized light waves are obtained by multiple incident angles measurement (60°, 70°, and 80°) at energy range of 0.5 - 6.5 eV. In order to obtain optical properties for every Ta concentrations (0.01, 0.4, and 5 at. %), multilayer modelling was performed simultaneously by using Drude-Lorentz model. Refractive index and optical dispersion parameters were determined by Wemple-DiDomenico relation. In general, refractive index at zero photon energy n(0) increases by increasing Ta concentration. Furthermore, optical band gap shows a significant increasing due to presence of Ta dopant. In addition, other optical constants are discussed as well.

  15. Resistive switching of a TaO{sub x}/TaON double layer via ionic control of carrier tunneling

    SciTech Connect

    Jeon, Heeyoung; Park, Jingyu; Kim, Hyunjung; Jang, Woochool; Song, Hyoseok; Kang, Chunho; Seo, Hyungtak; Jeon, Hyeongtag

    2014-04-14

    Resistance random access memory (RRAM) is an attractive candidate for future non-volatile memory due to its superior features. As the oxide thickness is scaled down, the charge transport mechanism is also subject to the transition from hopping to tunneling dominant process, which is critically related to the interfacial electronic band structure. A TaO{sub x}/TaON double layer-based RRAM is fabricated and characterized in this work. Upon TaON insertion at the lower interface, the improved switching behavior is observed. The TaON at the bottom electrode interface blocks oxygen vacancy percolation due to strong N-O bonds and also modifies interfacial band alignment to lower the injected electron energy from bottom electrode due to higher tunneling barrier height than that of TaO{sub x}/Pt. This study suggested that a defect-minimized insertion layer like TaON with a proper interfacial band alignment is pivotal in RRAM for the effective ionic control of carrier tunneling resulting in non-linear I-V behavior with improved properties.

  16. Combined experimental and theoretical assessments of the lattice dynamics and optoelectronics of TaON and Ta3N5

    NASA Astrophysics Data System (ADS)

    Nurlaela, Ela; Harb, Moussab; del Gobbo, Silvano; Vashishta, Manish; Takanabe, Kazuhiro

    2015-09-01

    Presented herein is a detailed discussion of the properties of the lattice dynamic and optoelectronic properties of tantalum(V) oxynitride (TaON) and tantalum(V) nitride (Ta3N5), from experimental and theoretical standpoint. The active Raman and infra red (IR) frequencies of TaON and Ta3N5 were measured using confocal Raman and Fourier Transform Infrared spectroscopies (FTIR) and calculated using the linear response method within the density functional perturbation theory (DFPT). The detailed study leads to an exhaustive description of the spectra, including the symmetry of the vibrational modes. Electronic structures of these materials were computed using DFT within the range-separated hybrid HSE06 exchange-correlation formalism. Electronic and ionic contributions to the dielectric constant tensors of these materials were obtained from DFPT within the linear response method using the PBE functional. Furthermore, effective mass of photogenerated holes and electrons at the band edges of these compounds were computed from the electronic band structure obtained at the DFT/HSE06 level of theory. The results suggest that anisotropic nature in TaON and Ta3N5 is present in terms of dielectric constant and effective masses.

  17. Assessment of relative Ti, Ta, and Nb (TiTaN) enrichments in global ocean island basalts

    NASA Astrophysics Data System (ADS)

    Peters, B.; Day, J. M.

    2013-12-01

    The relative sensitivity of trace element concentrations to processes governing solid-melt and solid-fluid interactions has made them particularly useful for tracing the effects of partial melting, fractional crystallization, metasomatism and similar processes on the composition of a parental melt to a rock or mineral. Radiogenic and stable isotope compositions, in contrast, can provide information on the long-term history and provenance of magmas. Despite the distinct information derived from relative and absolute abundances of trace elements compared with isotopes, numerous studies of ocean island basalts (OIB) have attempted to use trace elements as diagnostic geochemical tracers to understand parental magma compositions. In particular, attempts have been made to correlate 'TiTaN' (Ti, Ta and Nb) anomalies to the He-Os isotopic compositions of OIB based on contributions from recycled eclogite, a theoretical high-TiTaN reservoir, and peridotite, a theoretical high-3He/4He reservoir (Jackson, et al., 2008 G-cubed). These authors have proposed that TiTaN anomalies can be used as independent indicators for recycled oceanic crust and lithospheric mantle in OIB sources, a distinction previously reserved for isotopic data. However, TiTaN anomalies appear uncorrelated to OIB mantle source composition for three reasons. First, a new geochemical compilation of global OIB shows a wide range of Ti (Ti/Ti* = 0.28 - 2.35), Ta (Ta/Ta* = 0.11 - 93.42) and Nb (Nb/Nb* = 0.13 - 17.79) anomalies that do not correlated with each other or noble gas systematics, indicating that: (i) TiTaN anomalies alone do not correspond to the primitive source traced by high-3He/4He or the solar neon component and (ii) Ti, Ta and Nb anomalies may each reflect distinct processes or origins, rather than tracing a single source or process together. Second, positive Ti anomalies can be generated by low-degree (1-10%), non-modal batch partial melting of garnet lherzolite at temperatures and pressures

  18. Initiation of student-TA interactions in tutorials

    NASA Astrophysics Data System (ADS)

    Scherr, Rachel E.; Russ, Rosemary S.; Bing, Thomas J.; Hodges, Raymond A.

    2006-12-01

    At the University of Maryland we videotaped several semesters of tutorials as part of a large research project. A particular research task required us to locate examples of students calling the teaching assistants (TAs) over for assistance with a physics question. To our surprise, examples of this kind of interaction were difficult to find. We undertook a systematic study of TA-student interactions in tutorial: In particular, how are the interactions initiated? Do the students call the TA over for help with a particular issue, does the TA stop by spontaneously, or does the worksheet require a discussion with the TA at that point? The initiation of the interaction is of particular interest because it provides evidence of the motivation for and purpose of the interaction. This paper presents the results of that systematic investigation. We discovered that the majority of student-TA interactions in tutorial are initiated by teaching assistants, confirmed our initial observation that relatively few interactions are initiated by students, and found, further, that even fewer interactions are worksheet initiated. Perhaps most importantly, we found that our sense of who initiates tutorial interactions—based on extensive but informal observations—is not necessarily accurate. We need systematic investigations to uncover the reality of our classroom experiences.

  19. Er3+ diffusion in LiTaO3 crystal

    NASA Astrophysics Data System (ADS)

    Zhang, De-Long; Zhang, Qun; Wong, Wing-Han; Pun, Edwin Yue-Bun

    2015-12-01

    Some Er3+-doped LiTaO3 plates were prepared by in-diffusion of Er-metal film locally coated onto congruent Z-cut substrate in air at a wide temperature range from 1000 to 1500 °C. After diffusion, Er3+-doping effect on LiTaO3 refractive index and Li2O out-diffusion arising from Er3+ in-diffusion were studied at first. Refractive indices at the doped and undoped surface parts were measured by prism coupling technique and the surface composition was estimated. The results show that Er3+ dopant has small contribution to the LiTaO3 index. Li2O out-diffusion is slight (Li2O content loss <0.3 mol%) for the temperature below 1300 °C while is moderate (Li2O content loss <0.6 mol%) for the temperature above 1400 °C. The Er3+ profile was studied by secondary ion mass spectrometry. The study shows that the diffused Er3+ ions follow either a complementary error function or a Gaussian profile. Characteristic parameters including diffusivity, diffusion constant, activation energy, solubility, solubility constant and heat of solution were obtained and compared with the LiNbO3 case. The comparison shows that the diffusivity and solubility in LiTaO3 are considerably smaller than in LiNbO3 because of the difference of Ta and Nb in atomic weight.

  20. First-principles calculation of phase equilibrium of V-Nb, V-Ta, and Nb-Ta alloys

    NASA Astrophysics Data System (ADS)

    Ravi, C.; Panigrahi, B. K.; Valsakumar, M. C.; van de Walle, Axel

    2012-02-01

    In this paper, we report the calculated phase diagrams of V-Nb, V-Ta, and Nb-Ta alloys computed by combining the total energies of 40-50 configurations for each system (obtained using density functional theory) with the cluster expansion and Monte Carlo techniques. For V-Nb alloys, the phase diagram computed with conventional cluster expansion shows a miscibility gap with consolute temperature Tc=1250 K. Including the constituent strain to the cluster expansion Hamiltonian does not alter the consolute temperature significantly, although it appears to influence the solubility of V- and Nb-rich alloys. The phonon contribution to the free energy lowers Tc to 950 K (about 25%). Our calculations thus predicts an appreciable miscibility gap for V-Nb alloys. For bcc V-Ta alloy, this calculation predicts a miscibility gap with Tc=1100 K. For this alloy, both the constituent strain and phonon contributions are found to be significant. The constituent strain increases the miscibility gap while the phonon entropy counteracts the effect of the constituent strain. In V-Ta alloys, an ordering transition occurs at 1583 K from bcc solid solution phase to the V2Ta Laves phase due to the dominant chemical interaction associated with the relatively large electronegativity difference. Since the current cluster expansion ignores the V2Ta phase, the associated chemical interaction appears to manifest in making the solid solution phase remain stable down to 1100 K. For the size-matched Nb-Ta alloys, our calculation predicts complete miscibility in agreement with experiment.

  1. Advancement of online systems in engineering by Expert TA

    NASA Astrophysics Data System (ADS)

    Morton, Jeremy

    This dissertation introduces a new online system called Expert TA. The system was developed based on the hypothesis that expressions are key elements in engineering problems and that the treatment of expressions is critical to the advancement of online systems. This dissertation identifies ergonomic problems with expression entry that Expert TA overcomes through the use of a problem-customize integrated expression editor, called a palate. Then the dissertation shows, using an expression analyzer that operates in the background of Expert TA, that specific mathematical mistakes within an entered expression can now be located. Emulating standard instructional practices, detailed feedback pertaining to specific mistakes and grading on the basis of specific mistakes is now possible.

  2. Low temperature CVD of TaB/sub 2/

    SciTech Connect

    Randich, E.

    1980-01-01

    Crystalline TaB/sub 2/ has been deposited using the CVD reaction of TaCl/sub 5/ and B/sub 2/H/sub 6/ in the temperature range of 773-1200/sup 0/K. Thermodynamic calculations have been made which compare the use of both B/sub 2/H/sub 6/ and BCl/sub 3/ as B source gases. The deposits obtained with B/sub 2/H/sub 6/ exhibited extremely small crystal size and contained amorphous B when the deposition temperature was below approx. 873/sup 0/K but were substoichiometric in B above this temperature. Carbon analysis indicated that C may substitute for B and thereby stabilize the diboride structure at high deposition temperatures. Microhardness of the coatings decreased with increasing B/Ta ratio and decreasing crystal size.

  3. Optical spectroscopy of the Weyl semimetal TaAs

    DOE PAGES

    Xu, B.; Dai, Y. M.; Zhao, L. X.; Wang, K.; Yang, R.; Zhang, W.; Liu, J. Y.; Xiao, H.; Chen, G. F.; Taylor, A. J.; et al

    2016-03-24

    Here, we present a systematic study of both the temperature and frequency dependence of the optical response in TaAs, a material that has recently been realized to host the Weyl semimetal state. Our study reveals that the optical conductivity of TaAs features a narrow Drude response alongside a conspicuous linear dependence on frequency. The weight of the Drude peak decreases upon cooling, following a T2 temperature dependence, in good agreement with theoretical predictions. Two linear components with distinct slopes dominate the low-temperature optical conductivity. A comparison between our experimental results and theoretical calculations suggests that the linear conductivity below ~230more » cm–1 arises purely from interband transitions near the Weyl points, providing rich information about the Weyl semimetal state in TaAs.« less

  4. EDITORIAL: TaCoNa-Photonics 2008 TaCoNa-Photonics 2008

    NASA Astrophysics Data System (ADS)

    Chigrin, Dmitry N.; Busch, Kurt; Lavrinenko, Andrei V.

    2009-11-01

    This special section on theoretical and computational nano-photonics features papers presented at the first International Workshop on Theoretical and Computational Nano-Photonics (TaCoNa-Photonics 2008) held in Bad Honnef, Germany, 3-5 December 2008. The workshop covered a broad range of topics related to current developments and achievements in this interdisciplinary area of research. Since the late 1960s, the word `photonics' has been understood as the science of generating, controlling, and detecting light. Nowadays, a routine fabrication of complex structures with micro- and nano-scale dimensions opens up many new and exciting possibilities in photonics. The science of generating, routing and detecting light in micro- and nano-structured matter, `nano-photonics', is becoming more important both in research and technology and offers many promising applications. The inherently sub-wavelength character of the structures that nano-photonics deals with challenges modern theoretical and computational physics and engineering with many nontrivial questions: Up to what length-scale can one use a macroscopic phenomenological description of matter? Where is the interface between the classical and quantum description of light in nano-scale structures? How can one combine different physical systems, different time- and length-scales in a single computational model? How can one engineer nano-structured materials in order to achieve the desired optical properties for particular applications? Any attempt at answering these kinds of questions is impossible without the joint efforts of physicists, engineers, applied mathematicians and programmers. This is the reason why the major goal of the TaCoNa-Photonics workshops is to provide a forum where theoreticians and specialists in numerical methods from all branches of physics, engineering sciences and mathematics can compare their results, report on novel results and breakthroughs, and discuss new challenges ahead. In order to

  5. Electrochemical formation and optimization of Ta-based nanomaterials

    NASA Astrophysics Data System (ADS)

    Horwood, Corie A.

    The primary focus of this research has been to develop simple and precise methods for the formation of novel Ta-based nanostructures, including Ta oxide nanotubes (NTs) and Ta-supported Au nanoparticle (NP) arrays. These nanomaterials are very useful for applications in sensing, electrocatalysis/catalysis, spectroscopy, and more. The Ta oxide NTs are formed by the electrochemical anodization of Ta, a process which can be modified to produce ordered nanoscale dimples that cover the Ta surface. These dimples can then be used as templates for the formation of ordered Au nanoparticle arrays. An in-depth study of the anodization variables showed that NT growth can be slowed down by decreasing the anodization time and HF concentration in the solution, allowing the controlled formation of short (50--1000 nm) NTs in under one minute. The charge passed during anodization was found to be directly proportional to the length of the NTs formed, making cross-sectional imaging unnecessary. A novel two-step anodization method, interspersed with a thermal annealing or negative polarization step, produced stable and well-ordered NTs free of a problematic thin surface oxide layer. These vertically oriented arrays of short NTs were found to have interesting optical properties, with visible structural colours that depend on NT length. The colour of the NT arrays was also found to depend on the medium inside the NTs (air, water, other solids), used for the first time to monitor NT filling, and to determine the refractive index and porosity of the Ta oxide nanotubular array, properties that are otherwise very difficult to obtain. Dimpled Ta was used to create ordered Au NP arrays using two thin film dewetting methods, thermal annealing and pulsed laser-induced dewetting. These methods yield Au NPs of predictable size, shape, spacing, and surface density, with these parameters varying predictably with the initial thickness of the Au thin film and the technique used for dewetting. The Au

  6. Evaluation of airflow patterns in 2706-T and 2706-TA

    SciTech Connect

    DEROSA, D.C.

    1999-08-26

    The purpose of this study was to evaluate the adequacy of the current placement of fixed head air samplers and continuous air monitors (CAMs) in the 2706-T and 2706-TA Complex. The airflow study consisted of 6 configurations of facility HVAC and HEPA filtration equipment to determine impacts on CAM location. The results of this study provide recommendations based on guidance in DOE G 411.1-8 and NUREG-1400 for placement of fixed head air samplers or CAMS within 2706-T and 2706-TA.

  7. Fabrication of highly ordered Ta2O5 and Ta3N5 nanorod arrays by nanoimprinting and through-mask anodization

    NASA Astrophysics Data System (ADS)

    Li, Yanbo; Nagato, Keisuke; Delaunay, Jean-Jacques; Kubota, Jun; Domen, Kazunari

    2014-01-01

    Using highly ordered porous anodic alumina membrane fabricated with the aid of nanoimprinting as a mask, Ta2O5 nanorod array with uniform diameter, length, and distribution is grown in situ on a Ta substrate by through-mask anodization. The Ta2O5 nanorod array is further transformed into Ta3N5 nanorod array without damaging the nanorod structure by nitridation. Solar-driven photoelectrochemical water splitting with a maximum solar energy conversion efficiency of 0.36% is demonstrated with the Ta3N5 nanorod array after modifying the surface with cobalt-phosphate as a co-catalyst. The Ta2O5 and Ta3N5 nanorod arrays have potential applications in catalysis, photonics, UV photodetection and solar energy conversion.

  8. Preparation, characterization, and catalytic performance of Ta-HMS mesoporous molecular sieve

    NASA Astrophysics Data System (ADS)

    Li, Xuefeng; Zhang, Like; Gao, Huanxin; Chen, Qingling

    2016-08-01

    Various Ta-HMS (hexagonal mesoporous silica) samples with different Ta content were hydrothermally prepared and characterized by XRD, N2-adsorption, ICP-AES, FTIR, and UV-Vis spectroscopy. The catalytic performance of the samples was also evaluated in the epoxidation of cyclohexene with cumene hydroperoxide as oxidant. The regularity of mesoporous structure decreases while more extraframe Ta ions are formed with increasing the Ta content. Ta-HMS with Ta/Si ratio of 0.015 shows the highest conversion and selectivity in the studied epoxidation reaction. The catalyst can be used for three times without significant activity loss.

  9. Comparative Raman study of Weyl semimetals TaAs, NbAs, TaP and NbP

    NASA Astrophysics Data System (ADS)

    Liu, H. W.; Richard, P.; Zhao, L. X.; Chen, G.-F.; Ding, H.

    2016-07-01

    We report a comparative polarized Raman study of Weyl semimetals TaAs, NbAs, TaP and NbP. The evolution of the phonon frequencies with the sample composition allows us to determine experimentally which atoms are mainly involved for each vibration mode. Our results confirm previous first-principles calculations indicating that the A1, B1(2), E(2) and E(3) modes involve mainly the As(P) atoms, the B1(1) mode is mainly related to Ta(Nb) atoms, and the E(1) mode involves both kinds of atoms. By comparing the energy of the different modes, we establish that the B1(1), B1(2), E(2) and E(3) become harder with increasing chemical pressure. This behaviour differs from our observation on the A1 mode, which decreases in energy, in contrast to its behaviour under external pressure.

  10. Comparative Raman study of Weyl semimetals TaAs, NbAs, TaP and NbP.

    PubMed

    Liu, H W; Richard, P; Zhao, L X; Chen, G-F; Ding, H

    2016-07-27

    We report a comparative polarized Raman study of Weyl semimetals TaAs, NbAs, TaP and NbP. The evolution of the phonon frequencies with the sample composition allows us to determine experimentally which atoms are mainly involved for each vibration mode. Our results confirm previous first-principles calculations indicating that the A1, B1(2), E(2) and E(3) modes involve mainly the As(P) atoms, the B1(1) mode is mainly related to Ta(Nb) atoms, and the E(1) mode involves both kinds of atoms. By comparing the energy of the different modes, we establish that the B1(1), B1(2), E(2) and E(3) become harder with increasing chemical pressure. This behaviour differs from our observation on the A1 mode, which decreases in energy, in contrast to its behaviour under external pressure. PMID:27248581

  11. Analysis of NiAlTa precipitates in beta-NiAl + 2 at. pct Ta alloy

    NASA Technical Reports Server (NTRS)

    Pathare, V.; Michal, G. M.; Vedula, K.; Nathal, M. V.

    1987-01-01

    Results are reported from experiments performed to identify the precipitates, and their orientation in the matrix, in a beta-NiAl alloy containing 2 at. pct. Ta after undergoing creep test at 1300 K. Test specimens formed by extruding hot powders were compressed at 1300 K for about 50 hr at a strain rate averaging 6/1 million per sec. The specimens were then thinned and examined under an electron microscope and by X-ray diffractometry. An intermetallic NiAlTa compound with a hexagonal Cl4 structure appeared as second phase precipitates in the samples, exhibiting plate-like shapes and a habit plane close to (012). The prism planes of the hexagonal NiAlTa precipitates paralleled the closest packed planes in the cubic beta-NiAl matrix.

  12. Wheat hypersensitive-induced reaction genes TaHIR1 and TaHIR3 are involved in response to stripe rust fungus infection and abiotic stresses.

    PubMed

    Duan, Yinghui; Guo, Jun; Shi, Xuexia; Guan, Xiangnan; Liu, Furong; Bai, Pengfei; Huang, Lili; Kang, Zhensheng

    2013-02-01

    KEY MESSAGE : TaHIR1 and TaHIR3 play positive roles in resistance to the stripe rust fungus via inducing HR and regulating defense-related genes, but are negatively regulated by various abiotic stimuli. Plant hypersensitive-induced reaction (HIR) genes are known to be associated with the hypersensitive response and disease defense. In wheat, two HIR genes, TaHIR1 and TaHIR3, have been identified and found to be up-regulated after infection with the stripe rust fungus. Here, we further determined their roles in defense against abiotic stresses and the stripe rust pathogen, Puccinia striiformis f. sp. tritici. TaHIR1 and TaHIR3 proteins were localized in the plasma membrane of tobacco cells. The expression of TaHIR1 and TaHIR3 was reduced by the environmental stimuli, including low temperature, drought, and high salinity stresses. In addition, the expression of TaHIR1 and TaHIR3 was down-regulated by exogenously applied ethrel and abscisic acid, whereas expression was not affected by treatments with salicylic acid and methyl jasmonate. Furthermore, barley stripe mosaic virus-induced gene silencing of TaHIR1 and TaHIR3 reduced resistance in wheat cultivar Suwon11 against an avirulent stripe rust pathotype CYR23 and area of necrotic cells neighboring the infection sites, and altered the expression levels of defense-related genes. These results suggest that TaHIR1 and TaHIR3 function positively in the incompatible interaction of wheat-stripe rust fungus, but exhibit negative transcriptional response to abiotic stresses.

  13. Preparation and visible light induced photocatalytic activity of C-NaTaO3 and C-NaTaO3-Cl-TiO2 composite.

    PubMed

    Wu, Xiaoyong; Yin, Shu; Dong, Qiang; Sato, Tsugio

    2013-12-21

    A nice visible light responsive C-doped NaTaO3 (C-NaTaO3) particle has been successfully prepared by a facile solvothermal method using water-ethylene glycol mixed solutions as solvent. The results presented that the carbon could be easily incorporated in NaTaO3 from ethylene glycol during a solvothermal reaction, finally leading to excellent visible light absorption. The as-synthesized C-NaTaO3 showed excellent visible light induced photocatalytic activity superior to those of pure NaTaO3 and commercial P25. In addition, in order to further improve the visible light driven photocatalytic performance of C-NaTaO3, a new C-doped NaTaO3-Cl-doped TiO2 (C-NaTaO3-Cl-TiO2) core-shell type of composite was also fabricated. After coupling C-NaTaO3 with Cl-TiO2, the visible light induced NOx gas destruction ability of C-NaTaO3-Cl-TiO2 composite was significantly enhanced as compared to those of sole C-NaTaO3 and Cl-TiO2, probably due to the hindrance of the recombination rate of photogenerated electron-hole pairs. The C-NaTaO3 particle and C-NaTaO3-Cl-TiO2 composite prepared in this work would probably provide a new way to prepare high performance of visible light induced perovskite-type NaTaO3 based photocatalysts.

  14. Electronic structure of Au-Ta alloys:. An X-ray spectroscopy study

    NASA Astrophysics Data System (ADS)

    Kuhn, M.; Sammynaiken, R.; Sham, T. K.

    1998-07-01

    Au-Ta alloys with the compositions of AuTa, AuTa 2 and AuTa 3, prepared by quenching from the melt, has been studied with X-ray diffraction, photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES) measurements. It was found that while AuTa 3 is a single-phase solid solution, AuTa 2 and AuTa have mixed phases and that the Au and Ta 4f levels of the alloys shift to higher binding energy, relative to the pure metal; this is accompanied by a narrowing of the Au 5d component of the alloy d-band, which moves away from the Fermi level. This observation is interpreted in terms of a charge compensation model in which Au loses d charge but is overcompensated by s-p charge gain, resulting in a small net charge flow from Ta to Au. The observed Ta 4f binding energy shift is as predicted by electronegativity and indicates charge depletion at the Ta site. The notion of d charge depletion at both Au and Ta sites upon alloying is confirmed independently by XANES measurements which showed that the L 2,3 edge whiteline intensity for both Au and Ta increases as they become more dilute in the host, indicating an increase in d hole count. The experimental results compare favorably with a recent linear-augmented Slater-type-orbital (LASTO) calculations. The implications of these results are discussed.

  15. The Foreign TA: A Guide to Teaching Effectiveness.

    ERIC Educational Resources Information Center

    Gburek, Janice L., Ed.; Dunnett, Stephen C., Ed.

    Articles on teaching effectiveness for foreign teaching assistants (TAs) are presented. Topics include: adapting to the U.S. academic environment, understanding the role of the TA and gaining confidence, anticipating undergraduates' expectations, improving communication skills, and teaching laboratory classes and recitation classes. Titles and…

  16. Internal oxidation of laminated ternary Ru-Ta-Zr coatings

    NASA Astrophysics Data System (ADS)

    Chen, Yung-I.; Lu, Tso-Shen

    2015-10-01

    Researchers have observed the internal oxidation phenomenon in binary alloy coatings when developing refractory alloy coatings for protective purposes by conducting annealing at high temperatures and in oxygen-containing atmospheres. The coatings were assembled using cyclical gradient concentration deposition during cosputtering by employing a substrate holder rotating at a slow speed. The internally oxidized zone demonstrated a laminated structure, comprising alternating oxygen-rich and oxygen-deficient layers stacked in a general orientation. In the current study, Ru-Ta-Zr coatings were prepared with various stacking sequences during cosputtering. The Ru-Ta-Zr coatings were annealed at 600 °C in an atmosphere continuously purged with 1% O2-99% Ar mixed gas for 30 min. A transmission electron microscope was used to examine the periods of the laminated layers and crystallinity of the annealed coatings. Depth profiles produced using an Auger electron spectroscope and X-ray photoelectron spectroscope were used to certify the periodic variation of the related constituents and chemical states of the elements, respectively. The results indicate that the internally oxidized ternary coatings are stacked of Ru-, Ta2O5-, and ZrO2-dominant sublayers and that the stacking sequences of the sublayers affect the crystalline structure of the coatings. Zr is oxidized preferentially in the Ru-Ta-Zr coatings, increasing the surface hardness of the oxidized coatings.

  17. T.A. Barron: Glowing Like a Crystal.

    ERIC Educational Resources Information Center

    School Library Media Activities Monthly, 1995

    1995-01-01

    Presents an interview with T.A. Barron, an author of a trilogy of novels about a 12-year-old girl. Topics include character development, adult/child relationships, themes, writing processes, the influence of children on the writing, adult science fiction and young-adult classification of the books, and research and rewrites. (AEF)

  18. Ta Keo Temple Reconstruction Based on Terrestrial Laser Scanning Technology

    NASA Astrophysics Data System (ADS)

    Xi, X.; Wang, C.; Wan, Y. P.; Khuon, K. N.

    2015-08-01

    Ta Keo temple is one of the very famous temple complex of Angkor Wat in northwestern Cambodia. It has been suffering massive collapse and other serious damages in recent years. Nowadays, Terrestrial Laser Scanning(TLS) technology is considered as a wellestablished resource for heritage documentation and protection (Lerma et al, 2008; Reshetyuk, 2009). This paper used TLS to reconstruct Ta Keo Temple. Firstly, we acquired 71 scanning stations of points cloud data with high density and high accuracy, and over one thousand images with high spatial resolution about the temple. Secondly, the raw points cloud data were denoised, reduced and managed efficiently, and registrated using an adjusted ICP algorithm. Thirdly, a triangulation method was used to model most objects. At last, we mapped the texture data into the digital model and a 3-D model of Ta Keo with high accuracy was achieved. The authors focus on large object reconstruction by TLS technology, and pay much attention to the scanning design, multi-station data and the whole project's data registration, and texture mapping and so on. The research result will be useful for Ta Keo restoration, reconstruction and protection. Also, it is a good reference source for large complex buildings reconstruction when using terrestrial laser scanning technology.

  19. Compositional depth profiling of TaCN thin films

    SciTech Connect

    Adelmann, Christoph; Conard, Thierry; Franquet, Alexis; Brijs, Bert; Munnik, Frans; Burgess, Simon; Witters, Thomas; Meersschaut, Johan; Kittl, Jorge A.; Vandervorst, Wilfried; Van Elshocht, Sven

    2012-07-15

    The composition profiling of thin TaCN films was studied. For the composition profile determination using x-ray photoemission spectrometry (XPS) in combination with Ar sputtering, preferential sputtering effects of N with respect to Ta and C were found to lead to inaccurate elemental concentrations. Sputter yield calculations for the given experimental conditions allowed for the correction of a part of the error, leading to fair accuracy by reference-free measurements. Further improvement of the accuracy was demonstrated by the calibration of the XPS compositions against elastic recoil detection analysis (ERDA) results. For Auger electron spectrometry (AES) in combination with Ar sputtering, accurate results required the calibration against ERDA. Both XPS and AES allowed for a reliable and accurate determination of the compositional profiles of TaCN-based thin films after calibration. Time-of-flight secondary-ion mass spectrometry was also used to assess the composition of the TaCN films. However, the analysis was hampered by large matrix effects due to small unintentional oxygen contents in the films. Energy-dispersive x-ray spectrometry is also discussed, and it is shown that an accurate reference-free measurement of the average film concentration can be achieved.

  20. TA-stapler resection of congenital splenic cyst. Case report.

    PubMed

    Uranüs, S; Kronberger, L; Neumayer, K; Beham, A

    1990-03-01

    Splenic cysts are uncommon. Primary (true, epithelial) and secondary (false, non-epithelial) forms may be distinguished, the latter being more usual. Organ-preserving resection of a primary mesothelial splenic cyst, using a TA-stapler, is described and alternative techniques of splenic preservation are discussed.

  1. Microstructural Investigations On Ni-Ta-Al Ternary Alloys

    SciTech Connect

    Negache, M.; Souami, N.

    2010-01-05

    The Ni-Al-Ta ternary alloys in the Ni-rich part present complex microstructures. They are composed of multiple phases that are formed according to the nominal composition of the alloy, primary Ni(gamma), Ni{sub 3}Al(gamma'), Ni{sub 6}AlTa(tau{sub 3}), Ni{sub 3}Ta(delta) or in equilibrium: two solid phases (gamma'-tau{sub 3}), (tau{sub 3}-delta), (tau{sub 3}-gamma), (gamma-delta) or three solid phases (gamma'-tau{sub 3}-delta). The nature and the volume fraction of these phases give these alloys very interesting properties at high temperature, and this makes them attractive for specific applications. We have developed a series of ternary alloys in electric arc furnace, determining their solidification sequences using Differential Thermal Analysis (DTA), characterized by SEM-EDS, X-ray diffraction and by a microhardness tests. The follow-up results made it possible to make a correlation between the nature of the formed phases and their solidifying way into the Ni{sub 75}Al{sub x}Ta{sub y} (x+y = 25at.%) system, which are varied and complex. In addition to the solid solution Ni (gamma), the formed intermetallics compounds (gamma', tau{sub 3} and delta) has been identified and correlated with a complex balance between phases.We noticed that the hardness increases with the tantalum which has a hardening effect and though the compound Ni{sub 3}Ta(delta) is the hardest. The below results provide a better understanding of the complex microstructure of these alloys.

  2. Coexistence of Weyl physics and planar defects in the semimetals TaP and TaAs

    NASA Astrophysics Data System (ADS)

    Besara, T.; Rhodes, D. A.; Chen, K.-W.; Das, S.; Zhang, Q. R.; Sun, J.; Zeng, B.; Xin, Y.; Balicas, L.; Baumbach, R. E.; Manousakis, E.; Singh, D. J.; Siegrist, T.

    2016-06-01

    We report a structural study of the Weyl semimetals TaAs and TaP, utilizing diffraction and imaging techniques, where we show that they contain a high density of defects, leading to nonstoichiometric single crystals of both semimetals. Despite the observed defects and nonstoichiometry on samples grown using techniques already reported in the literature, de Haas-van Alphen measurements on TaP reveal quantum oscillations and a high carrier mobility, an indication that the crystals are of quality comparable to those reported elsewhere. Electronic structure calculations on TaAs reveal that the position of the Weyl points relative to the Fermi level shift with the introduction of vacancies and stacking faults. In the case of vacancies the Fermi surface becomes considerably altered, while the effect of stacking faults on the electronic structure is to allow the Weyl pockets to remain close to the Fermi surface. The observation of quantum oscillations in a nonstoichiometric crystal and the persistence of Weyl fermion pockets near the Fermi surface in a crystal with stacking faults point to the robustness of these quantum phenomena in these materials.

  3. Homoatomic clustering in T4Ga5 (T = Ta, Nb, Ta/Mo): a story of reluctant intermetallics crystallizing in a new binary structure type.

    PubMed

    Fredrickson, Rie T; Kilduff, Brandon J; Fredrickson, Daniel C

    2015-02-01

    In the formation of binary compounds, heteroatomic interactions are generally expected to play the leading role in providing stability. In this Article, we present a series of gallides, T(4)Ga(5) (T = Ta, Nb, and Ta/Mo), which appear to defy this expectation. Their complex crystal structures represent a new binary structure type (to the best of our knowledge),, which can be visualized in terms of a host lattice of T@T(8) body centered cubic (bcc) clusters linked through face-capping Ga(2) dumbbells to form a primitive cubic framework. The cubic spaces that result are alternately filled by distorted T pentagonal dodecahedra (sharing atoms with the host lattice) and dimers of bcc fragments, leading to a √2 × √2 × 2 supercell of the host framework structure. Ga tetrahedra and icosahedral units fill the remaining void spaces. Underlying these structural features is a strong tendency for homoatomic clustering of Ta and Ga, which is evident in all of the coordination polyhedra. Electronic structure calculations using density functional theory (DFT) and DFT-calibrated Hückel models reveal possible origins for this elemental segregation and the factors stabilizing the structure as a whole. A deep pseudogap is present at the Fermi energy of Ta(4)Ga(5) (as well as at that of Nb(4)Ga(5)), corresponding to the near-optimization of Ta-Ta and Ta-Ga interactions. This pseudogap emerges as a result of the ability of extensive Ta-Ta bonding to provide local 18-electron configurations to the Ta atoms, despite the electron concentration being only 8.75 electrons per Ta atom. Support for these Ta-Ta interactions is provided by Ga bridging atoms, whose valence orbitals' low number of angular nodes confers preferential stabilization to Ta-Ta bonding functions over antibonding ones. The observed spatial separation of the structure into Ta and Ga domains occurs as a consequence of the Ga atoms being pushed toward the periphery of the Ta clusters to play this supporting role. PMID

  4. Establishment of codominant markers for rice blast resistance gene Pi-ta

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A single nucleotide length polymorphism (SNLP) was identified at the intron region of the Pi-ta gene to develop a codominant Pi-ta gene marker suitable for genotyping with an ABI automated machine. The DNA primer specific to the resistance Pi-ta allele was labeled with the blue dye as a forward pr...

  5. Establishment of codominant marker for rice blast resistance gene pi-ta

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A single nucleotide length polymorphism (SNLP) was identified at the intron region of the Pi-ta gene to develop a codominant Pi-ta gene marker suitable for genotyping with an ABI automated machine. The DNA primer specific to the resistance Pi-ta allele was labeled with the blue dye as a forward pr...

  6. Characterization of leucocin B-Ta11a: a bacteriocin from Leuconostoc carnosum Ta11a isolated from meat.

    PubMed

    Felix, J V; Papathanasopoulos, M A; Smith, A A; von Holy, A; Hastings, J W

    1994-10-01

    Leuconostoc (Lc.) carnosum Ta11a, isolated from vacuum-packaged processed meats, produced a bacteriocin designated leucocin B-Ta11a. The crude bacteriocin was heat stable and sensitive to proteolytic enzymes, but not to catalase, lysozyme, or chloroform. It was active against Listeria monocytogenes and several lactic acid bacteria. Leucocin B-Ta11a was optimally produced at 25 degrees C in MRS broth at an initial pH of 6.0 or 6.5. An 8.9-MDa plasmid in Leuconostoc carnosum Ta11a hybridized to a 36-mer oligonucleotide probe (JF-1) that was homologous to leucocin A-UAL187. A 4.9-kb Sau3A fragment from a partial digest of the 8.9-MDa plasmid was cloned into pUC118. The 8.1-kb recombinant plasmid (pJF8.1) was used for sequencing and revealed the presence of two open reading frames (ORFs). ORF1 codes for a protein of 61 amino acids comprising a 37-amino-acid bacteriocin that was determined to be the leucocin B-Ta11a structural gene by virtue of its homology to leucocin A-UAL 187 (Hastings et al. 1991. J. Bacteriol 173:7491-7500). The 24-amino-acid N-terminal extension, however, differs from that of leucocin A-UAL187 by seven residues. The predicted protein of the ORF2 has 113 amino acids and is identical with the amino acid sequence of the cognate ORF of the leucocin A-UAL 187 operon.

  7. Characterization of leucocin B-Ta11a: a bacteriocin from Leuconostoc carnosum Ta11a isolated from meat.

    PubMed

    Felix, J V; Papathanasopoulos, M A; Smith, A A; von Holy, A; Hastings, J W

    1994-10-01

    Leuconostoc (Lc.) carnosum Ta11a, isolated from vacuum-packaged processed meats, produced a bacteriocin designated leucocin B-Ta11a. The crude bacteriocin was heat stable and sensitive to proteolytic enzymes, but not to catalase, lysozyme, or chloroform. It was active against Listeria monocytogenes and several lactic acid bacteria. Leucocin B-Ta11a was optimally produced at 25 degrees C in MRS broth at an initial pH of 6.0 or 6.5. An 8.9-MDa plasmid in Leuconostoc carnosum Ta11a hybridized to a 36-mer oligonucleotide probe (JF-1) that was homologous to leucocin A-UAL187. A 4.9-kb Sau3A fragment from a partial digest of the 8.9-MDa plasmid was cloned into pUC118. The 8.1-kb recombinant plasmid (pJF8.1) was used for sequencing and revealed the presence of two open reading frames (ORFs). ORF1 codes for a protein of 61 amino acids comprising a 37-amino-acid bacteriocin that was determined to be the leucocin B-Ta11a structural gene by virtue of its homology to leucocin A-UAL 187 (Hastings et al. 1991. J. Bacteriol 173:7491-7500). The 24-amino-acid N-terminal extension, however, differs from that of leucocin A-UAL187 by seven residues. The predicted protein of the ORF2 has 113 amino acids and is identical with the amino acid sequence of the cognate ORF of the leucocin A-UAL 187 operon. PMID:7765496

  8. Wheat Brassinosteroid-Insensitive1 (TaBRI1) Interacts with Members of TaSERK Gene Family and Cause Early Flowering and Seed Yield Enhancement in Arabidopsis

    PubMed Central

    Singh, Akanksha; Breja, Priyanka; Khurana, Jitendra P.; Khurana, Paramjit

    2016-01-01

    Brassinosteroids (BRs) hormones are important for plant growth, development and immune responses. They are sensed by the transmembrane receptor kinase Brassinosteroid-Insensitive 1 (BRI1) when they bind to its extracellular Leu-rich repeat (LRR) domain. We cloned and characterized the TaBRI1 from T. aestivum and raised overexpression transgenics in Arabidopsis to decipher its functional role. TaBRI1 protein consists of a putative signal peptide followed by 25 leucine rich repeats (LRR), a transmembrane domain and a C-terminal kinase domain. The analysis determined the interaction of TaBRI1 with five members of the wheat Somatic Embryogenesis Receptor Kinase (TaSERKs) gene family (TaSERK1, TaSERK2, TaSERK3, TaSERK4 and TaSERK5), at the plasma membrane. Furthermore, overexpression of TaBRI1 in Arabidopsis leads to the early flowering, increased silique size and seed yield. Root growth analysis of TaBRI1 overexpressing transgenic plants showed hypersensitivity to epi-brassinolide (epi-BL) hormone in a dose-dependent manner. Interestingly, transgenic Arabidopsis plants show thermotolerance phenotype at the seedling stages as revealed by chlorophyll content, photosystem II activity and membrane stability. The transcriptome profiling on the basis of microarray analysis indicates up-regulation of several genes related to brassinosteroid signaling pathway, abiotic stress response, defense response and transcription factors. These studies predict the possible role of TaBRI1 gene in plant growth and development imparting tolerance to thermal stress. PMID:27322749

  9. Wheat Brassinosteroid-Insensitive1 (TaBRI1) Interacts with Members of TaSERK Gene Family and Cause Early Flowering and Seed Yield Enhancement in Arabidopsis.

    PubMed

    Singh, Akanksha; Breja, Priyanka; Khurana, Jitendra P; Khurana, Paramjit

    2016-01-01

    Brassinosteroids (BRs) hormones are important for plant growth, development and immune responses. They are sensed by the transmembrane receptor kinase Brassinosteroid-Insensitive 1 (BRI1) when they bind to its extracellular Leu-rich repeat (LRR) domain. We cloned and characterized the TaBRI1 from T. aestivum and raised overexpression transgenics in Arabidopsis to decipher its functional role. TaBRI1 protein consists of a putative signal peptide followed by 25 leucine rich repeats (LRR), a transmembrane domain and a C-terminal kinase domain. The analysis determined the interaction of TaBRI1 with five members of the wheat Somatic Embryogenesis Receptor Kinase (TaSERKs) gene family (TaSERK1, TaSERK2, TaSERK3, TaSERK4 and TaSERK5), at the plasma membrane. Furthermore, overexpression of TaBRI1 in Arabidopsis leads to the early flowering, increased silique size and seed yield. Root growth analysis of TaBRI1 overexpressing transgenic plants showed hypersensitivity to epi-brassinolide (epi-BL) hormone in a dose-dependent manner. Interestingly, transgenic Arabidopsis plants show thermotolerance phenotype at the seedling stages as revealed by chlorophyll content, photosystem II activity and membrane stability. The transcriptome profiling on the basis of microarray analysis indicates up-regulation of several genes related to brassinosteroid signaling pathway, abiotic stress response, defense response and transcription factors. These studies predict the possible role of TaBRI1 gene in plant growth and development imparting tolerance to thermal stress. PMID:27322749

  10. Combined experimental and theoretical assessments of the lattice dynamics and optoelectronics of TaON and Ta{sub 3}N{sub 5}

    SciTech Connect

    Nurlaela, Ela; Harb, Moussab; Gobbo, Silvano del; Vashishta, Manish; Takanabe, Kazuhiro

    2015-09-15

    Presented herein is a detailed discussion of the properties of the lattice dynamic and optoelectronic properties of tantalum(V) oxynitride (TaON) and tantalum(V) nitride (Ta{sub 3}N{sub 5}), from experimental and theoretical standpoint. The active Raman and infra red (IR) frequencies of TaON and Ta{sub 3}N{sub 5} were measured using confocal Raman and Fourier Transform Infrared spectroscopies (FTIR) and calculated using the linear response method within the density functional perturbation theory (DFPT). The detailed study leads to an exhaustive description of the spectra, including the symmetry of the vibrational modes. Electronic structures of these materials were computed using DFT within the range-separated hybrid HSE06 exchange–correlation formalism. Electronic and ionic contributions to the dielectric constant tensors of these materials were obtained from DFPT within the linear response method using the PBE functional. Furthermore, effective mass of photogenerated holes and electrons at the band edges of these compounds were computed from the electronic band structure obtained at the DFT/HSE06 level of theory. The results suggest that anisotropic nature in TaON and Ta{sub 3}N{sub 5} is present in terms of dielectric constant and effective masses. - Graphical abstract: Detailed investigation has been conducted from combined experimental and theoretical approaches on Raman and IR spectroscopies, electronic structures, dielectric constants and effective masses of TaON and Ta{sub 3}N{sub 5}. - Highlights: • Crystal structures of TaON and Ta{sub 3}N{sub 5} are discussed based on XRD and DFT calculation. • Raman and IR spectra of TaON and Ta{sub 3}N{sub 5} materials are measured and computed by DFPT method. • Optoelectronic properties of TaON and Ta{sub 3}N{sub 5} are discussed. • Dielectric constant and effective masses of TaON and Ta{sub 3}N{sub 5} are calculated.

  11. Anomalous electronic structure and magnetoresistance in TaAs2

    PubMed Central

    Luo, Yongkang; McDonald, R. D.; Rosa, P. F. S.; Scott, B.; Wakeham, N.; Ghimire, N. J.; Bauer, E. D.; Thompson, J. D.; Ronning, F.

    2016-01-01

    The change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. Density functional calculations find that TaAs2 is a new topological semimetal [ℤ2 invariant (0;111)] without Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions. PMID:27271852

  12. Anomalous electronic structure and magnetoresistance in TaAs2.

    PubMed

    Luo, Yongkang; McDonald, R D; Rosa, P F S; Scott, B; Wakeham, N; Ghimire, N J; Bauer, E D; Thompson, J D; Ronning, F

    2016-01-01

    The change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. Density functional calculations find that TaAs2 is a new topological semimetal [ℤ2 invariant (0;111)] without Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions. PMID:27271852

  13. Anomalous electronic structure and magnetoresistance in TaAs2

    DOE PAGES

    Luo, Yongkang; McDonald, R. D.; Rosa, P. F. S.; Scott, B.; Wakeham, N.; Ghimire, N. J.; Bauer, E. D.; Thompson, J. D.; Ronning, F.

    2016-01-01

    We report that the change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. In conclusion, density functional calculations find that TaAs2 is a new topological semimetal [Z2 invariant (0;111)] withoutmore » Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions.« less

  14. TA-DA: A Tool for Astrophysical Data Analysis

    NASA Astrophysics Data System (ADS)

    Da Rio, Nicola; Robberto, Massimo

    2012-12-01

    We present the Tool for Astrophysical Data Analysis (TA-DA), a new software aimed to greatly simplify and improve the analysis of stellar photometric data in comparison with theoretical models, and allow the derivation of stellar parameters from multi-band photometry. Its flexibility allows one to address a number of such problems: from the interpolation of stellar models, or sets of stellar physical parameters in general, to the computation of synthetic photometry in arbitrary filters or units; from the analysis of observed color-magnitude diagrams to a Bayesian derivation of stellar parameters (and extinction) based on multi-band data. TA-DA is available as a pre-compiled Interactive Data Language widget-based application; its graphical user interface makes it considerably user-friendly. In this paper, we describe the software and its functionalities.

  15. TA-DA: A TOOL FOR ASTROPHYSICAL DATA ANALYSIS

    SciTech Connect

    Da Rio, Nicola; Robberto, Massimo

    2012-12-01

    We present the Tool for Astrophysical Data Analysis (TA-DA), a new software aimed to greatly simplify and improve the analysis of stellar photometric data in comparison with theoretical models, and allow the derivation of stellar parameters from multi-band photometry. Its flexibility allows one to address a number of such problems: from the interpolation of stellar models, or sets of stellar physical parameters in general, to the computation of synthetic photometry in arbitrary filters or units; from the analysis of observed color-magnitude diagrams to a Bayesian derivation of stellar parameters (and extinction) based on multi-band data. TA-DA is available as a pre-compiled Interactive Data Language widget-based application; its graphical user interface makes it considerably user-friendly. In this paper, we describe the software and its functionalities.

  16. Dislocation nucleation in bcc Ta single crystals studied by nanoindentation

    SciTech Connect

    Biener, M M; Biener, J; Hodge, A M; Hamza, A V

    2007-08-08

    The study of dislocation nucleation in closed-packed metals by nanoindentation has recently attracted much interest. Here, we address the peculiarities of the incipient plasticity in body centered cubic (bcc) metals using low index Ta single-crystals as a model system. The combination of nanoindentation with high-resolution atomic force microscopy provides us with experimental atomic-scale information on the process of dislocation nucleation and multiplication. Our results reveal a unique deformation behavior of bcc Ta at the onset of plasticity which is distinctly different from that of closed-packed metals. Most noticeable, we observe only one rather than a sequence of discontinuities in the load-displacement curves. This and other differences are discussed in context of the characteristic plastic deformation behavior of bcc metals.

  17. Rotational structures and the wobbling mode in {sup 167}Ta

    SciTech Connect

    Hartley, D. J.; Ludington, A.; Pifer, R.; Seyfried, E. P.; Vanhoy, J. R.; Janssens, R. V. F.; Carpenter, M. P.; Lauritsen, T.; McCutchan, E. A.; Zhu, S.; Riedinger, L. L.; Darby, I. G.; Riley, M. A.; Wang, X.; Aguilar, A.; Chiara, C. J.; Chowdhury, P.; Lakshmi, S.; Shirwadkar, U.; Tandel, S. K.

    2011-06-15

    Excited states in the neutron-deficient nucleus {sup 167}Ta were studied through the {sup 120}Sn({sup 51}V,4n) reaction. Twelve rotational bands have been observed and the relative excitation energy of each sequence is now known owing to the multiple interband connections. Several quasineutron alignments were observed that aided in the quasiparticle assignments of these bands. The resulting interpretation is in line with observations in neighboring nuclei. Trends in the wobbling phonon energy seen in {sup 161,163,165,167}Lu and {sup 167}Ta are also discussed and particle-rotor model calculations (assuming constant moments of inertia) are found to be inconsistent with the experimental data.

  18. Optimal filling fraction of Ta2O5 inverse opals

    NASA Astrophysics Data System (ADS)

    Tubio, C. R.; Guitian, F.; Gil, A.

    2013-12-01

    Tantalum pentoxide (Ta2O5) inverse opals were prepared by combining the self-assembly process and sol-gel chemistry-based opal infiltration. The inverse opal was made by the infiltration of a tantalum(V) ethoxide solution in the interstices of the polystyrene colloidal crystal template, and then removing the original opal template by calcination. The infiltration process as well as the optimal precursor concentration has been investigated in order to obtain Ta2O5 inverse opals with the optimal filling fraction. The effects of processing, template sphere size, morphology, structural properties, filling fraction and composition of the inverse opal are provided by scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy analysis (EDS) and powder X-ray diffraction (XRD). The results correlate the concentration of the precursor with the filling fraction of the template.

  19. Issues for reuse of gloveboxes at LANL TA-55

    SciTech Connect

    Cadwallader, L.C.; Pinson, P.A.; Miller, C.F.

    1998-08-01

    This report is a summary of issues that face plutonium glovebox designers and users at the Los Alamos National Laboratory (LANL) Technical Area 55 (TA-55). Characterizing the issues is a step in the task of enhancing the next generation glovebox design to minimize waste streams while providing the other design functions. This report gives an initial assessment of eight important design and operation issues that can benefit from waste minimization.

  20. TaN resistor process development and integration.

    SciTech Connect

    Romero, Kathleen; Martinez, Marino John; Clevenger, Jascinda; Austin, Franklin H., IV; Sullivan, Charles Thomas; Wolfley, Steven L.; Patrizi, Gary A.; Vigil, Pablita S.; Grine, Alejandro J.

    2010-05-01

    This paper describes the development and implementation of an integrated resistor process based on reactively sputtered tantalum nitride. Image reversal lithography was shown to be a superior method for liftoff patterning of these films. The results of a response surface DOE for the sputter deposition of the films are discussed. Several approaches to stabilization baking were examined and the advantages of the hot plate method are shown. In support of a new capability to produce special-purpose HBT-based Small-Scale Integrated Circuits (SSICs), we developed our existing TaN resistor process, designed for research prototyping, into one with greater maturity and robustness. Included in this work was the migration of our TaN deposition process from a research-oriented tool to a tool more suitable for production. Also included was implementation and optimization of a liftoff process for the sputtered TaN to avoid the complicating effects of subtractive etching over potentially sensitive surfaces. Finally, the method and conditions for stabilization baking of the resistors was experimentally determined to complete the full implementation of the resistor module. Much of the work to be described involves the migration between sputter deposition tools - from a Kurt J. Lesker CMS-18 to a Denton Discovery 550. Though they use nominally the same deposition technique (reactive sputtering of Ta with N{sup +} in a RF-excited Ar plasma), they differ substantially in their design and produce clearly different results in terms of resistivity, conformity of the film and the difference between as-deposited and stabilized films. We will describe the design of and results from the design of experiments (DOE)-based method of process optimization on the new tool and compare this to what had been used on the old tool.

  1. Role of the MHC2TA gene in autoimmune diseases

    PubMed Central

    Martínez, Alfonso; Sánchez‐Lopez, Marta; Varadé, Jezabel; Mas, Ana; Martín, M Carmen; de las Heras, Virginia; Arroyo, Rafael; Mendoza, Juan Luis; Díaz‐Rubio, Manuel; Fernández‐Gutiérrez, Benjamín; de la Concha, Emilio G; Urcelay, Elena

    2007-01-01

    Objectives Expression of major histocompatibility complex (MHC) class II genes is almost exclusively regulated by the class II transactivator. A promoter polymorphism (−168A/G, rs3087456) in the MHC2TA gene was associated with increased susceptibility to rheumatoid arthritis, multiple sclerosis and myocardial infarction in a northern European population. However, no evidence of association of this MHC2TA variant with the two autoimmune diseases could be subsequently detected in independent cohorts. Aim To test the aforementioned single nucleotide polymorphism and another G→C change (nt1614 from coding sequence, rs4774) to analyse the haplotype pattern in this MHC2TA gene. Methods A case–control study was performed with 350 patients with rheumatoid arthritis, 396 patients with multiple sclerosis, 663 patients with inflammatory bowel disease (IBD) and 519 healthy controls from Madrid. Genotyping was ascertained by using TaqMan assays‐on‐demand on a 7900HT analyser, following the manufacturer's suggestions (Applied Biosystems, Foster City, California, USA). Haplotypes were inferred with the expectation–maximisation algorithm implemented by the Arlequin software. Results No independent association with these autoimmune diseases was found for either polymorphism in the Spanish cohorts tested. However, when haplotypes were compared between patients with rheumatoid arthritis and controls, a significant difference in their overall frequency distribution was observed, evidencing a protective haplotype (−168A/1614C, p = 0.006; odds ratio (OR) 0.7) and a risk haplotype (−168G/1614C, p = 0.019; OR 1.6). Patients with multiple sclerosis mirrored these results, but no effect on IBD was identified. Conclusions The MHC2TA gene influences predisposition to rheumatoid arthritis and multiple sclerosis, but not to IBD. The −168G allele is not an aetiological variant in itself, but a genetic marker of susceptibility/protection haplotypes. PMID:17012290

  2. The Crystallization Clinic-A TA Orientation Exercise

    NASA Astrophysics Data System (ADS)

    Kandel, Marjorie

    1999-01-01

    Our orientation exercise for TAs in the organic laboratories is a Crystallization Clinic, and the main feature is a contest. Each TA has a different unknown solid to recrystallize. The products are judged by the students in the organic lab courses. Beauty of the crystals is the single criterion. The contest serves to refresh the TAs' technique and to give them empathy with the beginning students.

  3. Technical Area V (TA-V) transformation project close-out report.

    SciTech Connect

    Not Available

    2010-07-01

    Sandia National Laboratories (SNL) Technical Area V (TA-V) has provided unique nuclear experimental environments for decades. The technologies tested in TA-V facilities have furthered the United States Nuclear Weapons program and has contributed to the national energy and homeland security mission. The importance of TA-V working efficiently to produce an attractive and effective platform for experiments should not be underestimated. Throughout its brief history, TA-V has evolved to address multiple and diverse sets of requirements. These requirements evolved over many years; however, the requirements had not been managed nor communicated comprehensively or effectively. A series of programmatic findings over several years of external audits was evidence of this downfall. Today, these same requirements flow down through a new TA-V management system that produces consistently applied and reproducible approaches to work practices. In 2008, the TA-V department managers assessed the state of TA-V services and work activities to understand how to improve customer interfaces, stakeholders perceptions, and workforce efficiencies. The TA-V management team initiated the TA-V Transformation Project after they deemed the pre-June 2008 operational model to be ineffective in managing work and in providing integrated, continuous improvement to TA-V processes. This report summarizes the TA-V Transformation Project goals, activities, and accomplishments.

  4. Seismic assessment of Technical Area V (TA-V).

    SciTech Connect

    Medrano, Carlos S.

    2014-03-01

    The Technical Area V (TA-V) Seismic Assessment Report was commissioned as part of Sandia National Laboratories (SNL) Self Assessment Requirement per DOE O 414.1, Quality Assurance, for seismic impact on existing facilities at Technical Area-V (TA-V). SNL TA-V facilities are located on an existing Uniform Building Code (UBC) Seismic Zone IIB Site within the physical boundary of the Kirtland Air Force Base (KAFB). The document delineates a summary of the existing facilities with their safety-significant structure, system and components, identifies DOE Guidance, conceptual framework, past assessments and the present Geological and Seismic conditions. Building upon the past information and the evolution of the new seismic design criteria, the document discusses the potential impact of the new standards and provides recommendations based upon the current International Building Code (IBC) per DOE O 420.1B, Facility Safety and DOE G 420.1-2, Guide for the Mitigation of Natural Phenomena Hazards for DOE Nuclear Facilities and Non-Nuclear Facilities.

  5. Level structures in odd-odd deformed nucleus 184Ta

    NASA Astrophysics Data System (ADS)

    Gowrishankar, R.; Sood, P. C.

    2016-02-01

    A detailed low-energy level scheme of the odd-odd n-rich nucleus 184 73Ta111 is constructed using the well tested Two-Quasiparticle Rotor Model (TQRM) for calculating the bandhead energies of physically admissible 2qp configurations with the inclusion of residual n-p interaction contribution. The presently available data on this level scheme from 184Hf decay are shown to be in agreement with these calculations. Our analysis concludes that 184Hf ( Q_{β}=1340(30) keV) decay admits of 7 additional (to the 3 presently reported) β-branches to 184Ta with J = 0 or 1 and 8 more physically admissible weak ( 1fu β-branches populating J^{π}=2- levels in 184Ta. Further, a close examination of our level scheme clearly indicates the existence of a low-lying ( Ex = 260(40) keV) high-spin ( J^{π}=10-) long-lived isomer in this nucleus.

  6. Branched Ta nanocolumns grown by glancing angle deposition

    SciTech Connect

    Zhou, C.M.; Gall, D.

    2006-05-15

    Periodic arrays of Ta nanocolumns, 200 nm wide and 600 nm tall, were grown by glancing angle sputter deposition onto self-assembled close-packed arrays of 260-nm-diameter silica spheres. Each sphere leads to the development of a single Ta column. As growth progresses, roughening of the column top surfaces causes branching of some columns into subcolumns. The measured fraction of branched columns f{sub b} decreases with increasing growth temperature, from 30% at 200 deg. C to 4% at 700 deg. C. This is attributed to the increased adatom mobility at elevated temperatures, leading to a larger average separation of growth mounds and, in turn, lower nucleation probabilities for subcolumns. Branching into 3 and 4 subcolumns exhibits probabilities proportional to f{sub b}{sup 2} and f{sub b}{sup 3}, respectively. A fit of the data with a simple nucleation model provides an effective activation energy for Ta surface diffusion of 2.0 eV.

  7. Epitaxial NaCl structure {delta}-TaN{sub x}(001): Electronic transport properties, elastic modulus, and hardness versus N/Ta ratio

    SciTech Connect

    Shin, C.-S.; Gall, D.; Kim, Y.-W.; Desjardins, P.; Petrov, I.; Greene, J. E.; Oden, M.; Hultman, L.

    2001-09-15

    While metastable B1-NaCl-structure {delta}-TaN{sub x} is presently used in a variety of hard coating, wear-resistant, and diffusion barrier applications, it is a complex material exhibiting a wide single-phase field, x{approx_equal}0.94--1.37, and little is known about its fundamental properties. Here, we report physical properties of epitaxial {delta}-TaN{sub x} layers grown as a function of x on MgO(001) by ultrahigh vacuum reactive magnetron sputter deposition. The room-temperature resistivity ({rho}=225 {mu}{Omega} cm), hardness (H=30.9 GPa), and elastic modulus (E=455 GPa) of {delta}-TaN{sub x}(001) are independent of x over the range 0.94--1.22. However, changes in the electronic structure associated with increasing x>1.22 lead to an increase in {rho} with a decrease in H and E. All {delta}-TaN{sub x}(001) layers exhibit negative temperature coefficients of resistivity between 20 and 400 K due to weak carrier localization. {delta}-TaN{sub x} is superconducting with the highest critical temperature, 8.45 K, obtained for layers with the lowest N/Ta ratio, x=0.94. Based upon the above results, combined with the fact that the relaxed lattice constant a{sub 0} shows only a very weak dependence on x, we propose that the wide phase field in {delta}-TaN{sub x} is due primarily to antisite substitutions of Ta on N (and N on Ta) sites, rather than to cation and anion vacancies. To first order, antisite substitutions in TaN{sub x} are isoelectronic and hence have little effect on charge carrier density. At sufficiently high N/Ta ratios, however, simple electron-counting arguments are no longer valid since large deviations from stoichiometry alter the character of the band structure itself.

  8. 77 FR 47671 - TA-W-81,520, T-Mobile USA, Inc., Call Center, Allentown, PA; TA-W-81,520G, T-Mobile USA, Inc...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-09

    ... Employment and Training Administration TA-W-81,520, T-Mobile USA, Inc., Call Center, Allentown, PA; TA- W-81..., Inc., Call Center, Allentown, Pennsylvania (TA-W-81,520), Fort Lauderdale, Florida (TA-W-81,520A... include workers of the Bellevue, Washington location of T-Mobile USA, Inc., Call Center. The intent of...

  9. Boron site preference in ternary Ta and Nb boron silicides

    SciTech Connect

    Khan, Atta U.; Nunes, Carlos A.; Coelho, Gilberto C.; Suzuki, Paulo A.; Grytsiv, Andriy; Bourree, Francoise; Rogl, Peter F.

    2012-06-15

    X-ray single crystal (XSC) and neutron powder diffraction data (NPD) were used to elucidate boron site preference for five ternary phases. Ta{sub 3}Si{sub 1-x}B{sub x} (x=0.112(4)) crystallizes with the Ti{sub 3}P-type (space group P4{sub 2}/n) with B-atoms sharing the 8g site with Si atoms. Ta{sub 5}Si{sub 3-x} (x=0.03(1); Cr{sub 5}B{sub 3}- type) crystallizes with space group I4/mcm, exhibiting a small amount of vacancies on the 4a site. Both, Ta{sub 5}(Si{sub 1-x}B{sub x}){sub 3}, x=0.568(3), and Nb{sub 5}(Si{sub 1-x}B{sub x}){sub 3}, x=0.59(2), are part of solid solutions of M{sub 5}Si{sub 3} with Cr{sub 5}B{sub 3}-type into the ternary M-Si-B systems (M=Nb or Ta) with B replacing Si on the 8h site. The D8{sub 8}-phase in the Nb-Si-B system crystallizes with the Ti{sub 5}Ga{sub 4}-type revealing the formula Nb{sub 5}Si{sub 3}B{sub 1-x} (x=0.292(3)) with B partially filling the voids in the 2b site of the Mn{sub 5}Si{sub 3} parent type. - Graphical abstract: The crystal structures of a series of compounds have been solved from X-ray single crystal diffractometry revealing details on the boron incorporation. Highlights: Black-Right-Pointing-Pointer Structure of a series of compounds have been solved by X-ray single crystal diffractometry. Black-Right-Pointing-Pointer Ta{sub 3}(Si{sub 1-x}B{sub x}) (x=0.112) crystallizes with the Ti{sub 3}P-type, B and Si atoms randomly share the 8g site. Black-Right-Pointing-Pointer Structure of Nb{sub 5}Si{sub 3}B{sub 1-x} (x=0.292; Ti{sub 5}Ga{sub 4}-type) was solved from NPD.

  10. The rules of the resistive switching operation parameters based on Ta/Ta2O5 RRAM device

    NASA Astrophysics Data System (ADS)

    Li, Haitao; Richter, Curt; Kirillov, Oleg; Yuan, Hui; Zhu, Hao; Ioannou, Dimitris; Li, Qiliang; Dept. ECE, George Mason University Team; Semiconductor and Dimensional Metrology Division, NIST Team

    2013-03-01

    The resistive switching (RS) of the TaOx based RRAM has been widely studied due to its excellent endurance and thermal stability. The RS mechanism is generally understood as the formation and dissolution of nanometer-size conductive filament (CF) formed in set and reset process, respectively. However the exact process of dielectric break down remains unknown. In this work we studied the RS of the Ta/Ta2O5 based RRAM devices from the dependences of operation parameters Vset, ICC, Vreset, and Ireset on device resistance. From statistical analysis of variation in the threshold parameters, we found that the set process is mainly determined by the voltage stress on the device, instead of current. The first forming process is different from the following set process. The forming voltage exponentially depends on the pristine resistance. The forming process gives a smallest low resistance (RLRS) for each device. As a result change in compliance current (ICC) has no obvious effects on this low resistance state. Supported by Virginia Microelectronics Consortium Research Funding

  11. Nitridation of organo-silicate glass: A self-limiting process for PVD Ta 1+ xN/Ta barrier formation

    NASA Astrophysics Data System (ADS)

    Wilks, J. A.; Kelber, J. A.

    2009-09-01

    Interfacial reactions of sputter-deposited Ta with a low dielectric constant Si-O-C-H material (SiCOH), and with surface-nitrided SiCOH (N-SiCOH) were investigated using X-ray photoelectron spectroscopy (XPS). The studies were carried out in a system containing a processing chamber attached to an XPS analysis chamber so that sample transport between deposition and analysis environments occurred under ultrahigh vacuum (UHV) conditions. Ta sputter deposition on unmodified SiCOH yielded an interfacial phase ˜3 nm thick composed of Ta oxide/carbide (Ta-O-C), which is known to interact only weakly with Cu. Bombardment of the vicinal SiCOH surface by 500 eV Ar + in the presence of NH 3 resulted in carbon depletion and the self-limiting nitridation of the surface, with N attachment primarily at Si sites. Subsequent Ta sputter deposition yielded reduced Ta oxide and carbide formation, and formation of a Ta-rich nitride layer of 10 Å average thickness. Subsequent deposition resulted in metallic Ta formation.

  12. 75 FR 43564 - TA-W-71,483, Continental Airlines, Inc., Reservations Division, Houston, TX; TA-W-71,483A...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-26

    ... Register on May 20, 2010 (75 FR 28301). Workers of Continental Airlines, Inc., Reservations Division are... Employment and Training Administration TA-W-71,483, Continental Airlines, Inc., Reservations Division, Houston, TX; TA-W-71,483A, Continental Airlines, Inc., Reservations Division, Tampa, FL;...

  13. Structure of metal-oxide Ti-Ta-(Ti,Ta)xOy coatings during spark alloying and induction-thermal oxidation

    NASA Astrophysics Data System (ADS)

    Koshuro, V.; Fomin, A.; Fomina, M.; Rodionov, I.; Brzhozovskii, B.; Martynov, V.; Zakharevich, A.; Aman, A.; Oseev, A.; Majcherek, S.; Hirsch, S.

    2016-08-01

    The study focuses on combined spark alloying of titanium and titanium alloy surface and porous matrix structure oxidation. The metal-oxide coatings morphology is the result of melt drop transfer, heat treatment, and oxidation. The study establishes the influence of technological regimes of alloying and oxidation on morphological heterogeneity of metal- oxide system Ti-Ta-(Ti,Ta)xOy.

  14. Processing and characterization of zeta-Ta4C 3-x: A high toughness tantalum carbide

    NASA Astrophysics Data System (ADS)

    Sygnatowicz, Michael M.

    Tantalum carbides are commonly processed by hot-pressing, canned hot-isostatic-pressing, or spark-plasma sintering because of their high melting temperatures and low diffusivities. This study reports processing of dense ζ-Ta4C 3-x by reaction sintering of a Ta and TaC powder mixture (C/Ta atomic ratio = 0.66). ζ-Ta4C3-x is of interest due to its rhombohedral (trigonal) crystal structure that may be characterized as a polytype with both face-centered-cubic (fcc) and hexagonal-close-packed (hcp) Ta stacking sequences interrupted by stacking faults and missing carbon layers. This structure leads to easy cleaving on the basal planes and high fracture toughness. A key step in processing is the hydrogenation of the Ta powder to produce beta-TaH x, a hard and brittle phase that enables efficient comminution during milling and production of small, equiaxed Ta particles that can be packed to high green density with the TaC powder. Studies of phase evolution by quantitative X-ray diffraction during sintering revealed several intermediate reactions: (a) decomposition of beta-TaHx to Ta, (b) diffusion of C from gamma-TaC to Ta leading to the formation of α-Ta2Cy' with the kinetics described by the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation with an exponent, n = 0.5, and an activation energy of 221 kJ/mole, (c) equilibration of α-Ta2Cy' and gamma-TaC 0.78 phases, and (d) formation of ζ-Ta4C2.56 from the equilibrated α-Ta2C and gamma-TaC0.78 phases with the kinetics characterized by a higher JMAK exponent ( n ≈ 3) and higher activation energy (1089 kJ/mole). The microstructure showed evidence of nucleation and growth of the ζ-Ta4C 2.56 phase in both the α-Ta2C and gamma-TaC0.78 parent phases with distinct difference in the morphology due to the different number of variants of the habit plane. A hot-pressed and hot-isostatic-pressed (HIPed) material (C/Ta atomic ratio = 0.66), having formed 95 w% ζ-phase, attained a fracture toughness of 15.6 +/- 0.5 MPa√m and a

  15. TaER Expression Is Associated with Transpiration Efficiency Traits and Yield in Bread Wheat.

    PubMed

    Zheng, Jiacheng; Yang, Zhiyuan; Madgwick, Pippa J; Carmo-Silva, Elizabete; Parry, Martin A J; Hu, Yin-Gang

    2015-01-01

    ERECTA encodes a receptor-like kinase and is proposed as a candidate for determining transpiration efficiency of plants. Two genes homologous to ERECTA in Arabidopsis were identified on chromosomes 6 (TaER2) and 7 (TaER1) of bread wheat (Triticum aestivum L.), with copies of each gene on the A, B and D genomes of wheat. Similar expression patterns were observed for TaER1 and TaER2 with relatively higher expression of TaER1 in flag leaves of wheat at heading (Z55) and grain-filling (Z73) stages. Significant variations were found in the expression levels of both TaER1 and TaER2 in the flag leaves at both growth stages among 48 diverse bread wheat varieties. Based on the expression of TaER1 and TaER2, the 48 wheat varieties could be classified into three groups having high (5 varieties), medium (27 varieties) and low (16 varieties) levels of TaER expression. Significant differences were also observed between the three groups varying for TaER expression for several transpiration efficiency (TE)- related traits, including stomatal density (SD), transpiration rate, photosynthetic rate (A), instant water use efficiency (WUEi) and carbon isotope discrimination (CID), and yield traits of biomass production plant-1 (BYPP) and grain yield plant-1 (GYPP). Correlation analysis revealed that the expression of TaER1 and TaER2 at the two growth stages was significantly and negatively associated with SD (P<0.01), transpiration rate (P<0.05) and CID (P<0.01), while significantly and positively correlated with flag leaf area (FLA, P<0.01), A (P<0.05), WUEi (P<0.05), BYPP (P<0.01) and GYPP (P<0.01), with stronger correlations for TaER1 than TaER2 and at grain-filling stage than at heading stage. These combined results suggested that TaER involved in development of transpiration efficiency -related traits and yield in bread wheat, implying a function for TaER in regulating leaf development of bread wheat and contributing to expression of these traits. Moreover, the results indicate

  16. Magnetic field strength influence on the reactive magnetron sputter deposition of Ta2O5

    NASA Astrophysics Data System (ADS)

    Hollerweger, R.; Holec, D.; Paulitsch, J.; Rachbauer, R.; Polcik, P.; Mayrhofer, P. H.

    2013-08-01

    Reactive magnetron sputtering enables the deposition of various thin films to be used for protective as well as optical and electronic applications. However, progressing target erosion during sputtering results in increased magnetic field strengths at the target surface. Consequently, the glow discharge, the target poisoning, and hence the morphology, crystal structure and stoichiometry of the prepared thin films are influenced. Therefore, these effects were investigated by varying the cathode current Im between 0.50 and 1.00 A, the magnetic field strength B between 45 and 90 mT, and the O2/(Ar + O2) flow rate ratio Γ between 0% and 100%. With increasing oxygen flow ratio a substoichiometric TaOx oxide forms at the metallic Ta target surface which further transfers to a non-conductive tantalum pentoxide Ta2O5, impeding a stable dc glow discharge. These two transition zones (from Ta to TaOx and from TaOx to Ta2O5) shift to higher oxygen flow rates for increasing target currents. In contrast, increasing the magnetic field strength (e.g., due to sputter erosion) mainly shifts the TaOx to Ta2O5 transition to lower oxygen flow rates while marginally influencing the Ta to TaOx transition. To allow for a stable dc glow discharge (and to suppress the formation of non-conductive Ta2O5 at the target) even at Γ = 100% either a high target current (Im ⩾ 1 A) or a low magnetic field strength (B ⩽ 60 mT) is necessary. These conditions are required to prepare stoichiometric and fully crystalline Ta2O5 films.

  17. Immunotherapy of malignant disease with tumor antigen (TA)-specific monoclonal antibodies: does its therapeutic efficacy require cooperation with TA-specific CTL?

    PubMed Central

    Campoli, Michael; Ferris, Robert; Ferrone, Soldano; Wang, Xinhui

    2009-01-01

    A few tumor antigen (TA)-specific monoclonal antibodies (mAb) have been approved by FDA for the treatment of several major malignant diseases and are commercially available. Once in the clinic, mAb have an average success rate of ~30% and are well tolerated. These results have changed the face of cancer therapy, bringing us closer to more specific and more effective biologic therapy of cancer. The challenge facing tumor immunologists at present is represented by the identification of the mechanism(s) underlying patients’ differential clinical response to mAb-based immunotherapy. This information is expected to lead to the development of criteria to select patients to be treated with mAb-based immunotherapy. In the past in vitro and in vivo evidence has shown that TA-specific mAb can mediate their therapeutic effect by inducing tumor cell apoptosis, inhibiting the targeted antigen function, blocking tumor cell signaling and/or mediating complement-or cell-dependent lysis of tumor cells. More recent evidence suggests that TA-specific mAb can induce TA-specific cytotoxic T cell responses by enhancing TA uptake by dendritic cells (DC) and cross-priming of T cells. In this manuscript, we briefly summarize the TA-specific mAb that have received FDA approval. Next we review the potential mechanisms underlying the therapeutic efficacy of TA-specific mAb with emphasis on the induction of TA-specific cellular immune responses and their potential to contribute to the clinical efficacy of TA-specific mAb-based immunotherapy. Lastly, we discuss the potential negative impact of immune escape mechanisms on the clinical efficacy of TA-specific mAb-based immunotherapy. PMID:20028761

  18. The system Ta-V-Si: Crystal structure and phase equilibria

    SciTech Connect

    Khan, A.U.; Broz, P.; Bursik, J.; Grytsiv, A.; Chen, X.-Q.; Giester, G.; Rogl, P.

    2012-03-15

    Phase relations have been evaluated for the Ta-V-Si system at 1500 and 1200 Degree-Sign C. Three ternary phases were found: {tau}{sub 1}-(Ta,V){sub 5}Si{sub 3} (Mn{sub 5}Si{sub 3}-type), {tau}{sub 2}-Ta(Ta,V,Si){sub 2} (MgZn{sub 2}-type) and {tau}{sub 3}-Ta(Ta,V,Si){sub 2} (MgCu{sub 2}-type). The crystal structure of {tau}{sub 2}-Ta(Ta,V,Si){sub 2} was solved by X-ray single crystal diffraction (space group P6{sub 3}/mmc). Atom order in the crystal structures of {tau}{sub 1}-(Ta,V){sub 5}Si{sub 3} (Mn{sub 5}Si{sub 3} type) and {tau}{sub 3}-Ta(Ta,V,Si){sub 2} was derived from X-ray powder diffraction data. A large homogeneity range was found for {tau}{sub 1}-(Ta{sub x}V{sub 1-x}){sub 5}Si{sub 3} revealing random exchange of Ta and V at a constant Si content. At 1500 Degree-Sign C, the end points of the {tau}{sub 1}-phase solution (0.082{<=}x{<=}0.624) are in equilibrium with the solutions (Ta{sub 1-x}V{sub x}){sub 5}Si{sub 3} (Cr{sub 5}B{sub 3} type, 0{<=}x{<=}0.128) and (Ta{sub x}V{sub 1-x}){sub 5}Si{sub 3} (W{sub 5}Si{sub 3} type, 0{<=}x{<=}0.048). - Graphical abstract: Phase relations have been evaluated for the Ta-V-Si system at 1500 and 1200 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Phase relations have been evaluated for the Ta-V-Si system at 1500 and 1200 Degree-Sign C. Black-Right-Pointing-Pointer Three ternary phases were found at 1500 Degree-Sign C. Black-Right-Pointing-Pointer At 1500 Degree-Sign C, {tau}{sub 1}-phase has large homogeneity region (0.064{<=}x{<=}0.624).

  19. Identification of a New Locus, Ptr(t), Required for Rice Blast Resistance Gene Pi-ta-Mediated Resistance

    SciTech Connect

    Jia, Yulin; Martin, Rodger Carl

    2008-01-01

    Resistance to the blast pathogen Magnaporthe oryzae is proposed to be initiated by physical binding of a putative cytoplasmic receptor encoded by a NBS type resistance gene Pi-ta to the processed elicitor encoded by the corresponding avirulence gene AVR-Pita. Here we report the identification of a new locus Ptr(t) that is required for Pi-ta-mediated signal recognition. A Pi-ta expressing susceptible mutant was identified using a genetic screen. Putative mutations at Ptr(t) does not alter recognition specificity to another resistance gene Pi-ks in the Pi-ta homozygote indicate that Ptr(t) is more likely specific to Pi-ta-mediated signal recognition. Genetic crosses of Pi-ta Ptr(t) and Pi-ta ptr(t) homozygotes suggest that Ptr(t) segregate at single dominant nuclear gene. A ratio of 1 resistant: 1 susceptible of a BC1 using Pi-ta Ptr(t) with pi-ta ptr(t) homozygotes indicates that Pi-ta and Ptr(t) are linked and co-segregated. Genotyping of mutants of pi-ta ptr(t) and Pi-ta Ptr(t) homozygotes using ten simple sequence repeat markers spanning 9 megabase of Pi-ta determines that Pi-ta and Ptr(t) are of indica origin. Identification of Ptr(t) is a significant advancement in studying Pi-ta-mediated signal recognition and transduction.

  20. Nucleation of fcc Ta when heating thin films

    SciTech Connect

    Janish, Matthew T.; Mook, William M.; Carter, C. Barry

    2014-10-25

    Thin tantalum films have been studied during in-situ heating in a transmission electron microscope. Diffraction patterns from the as-deposited films were typical of amorphous materials. Crystalline grains were observed to form when the specimen was annealed in-situ at 450°C. Particular attention was addressed to the formation and growth of grains with the face-centered cubic (fcc) crystal structure. As a result, these observations are discussed in relation to prior work on the formation of fcc Ta by deformation and during thin film deposition.

  1. Adventures in transformations: TG, TA, oh my! (Poster abstract)

    NASA Astrophysics Data System (ADS)

    Ciocca, M.

    2015-12-01

    (Abstract only) AAVSO made available, through the great volunteer work of Gordon Myers and George Silvis, two very useful tools, Transform Generator and Transform Applier (TG and TA) for transforming instrumental magnitudes to the standard system. I will juxtapose the steps necessary to obtain transformation parameters "the old fashion way" and how can the same result be achieved with these two tools. I will present transformation parameters for the Eastern Kentucky University (EKU) telescope and obtained with the standard field M67. These parameters were applied to photometric results for AE Uma, a short-period, high-amplitude delta Scuti star (Period ~ 0.086 d).

  2. TA-DA: A Tool for Astrophysical Data Analysis

    NASA Astrophysics Data System (ADS)

    Da Rio, Nicola; Robberto, Massimo

    2012-10-01

    TA-DA is a pre-compiled IDL widget-based application which greatly simplifies and improves the analysis of stellar photometric data in comparison with theoretical models and allows the derivation of stellar parameters from multi-band photometry. It is flexible and can address a number of problems, from the interpolation of stellar models or sets of stellar physical parameters in general to the computation of synthetic photometry in arbitrary filters or units. It also analyzes observed color-magnitude diagrams and allows a Bayesian derivation of stellar parameters (and extinction) based on multi-band data.

  3. TaC Studios New Construction Test House

    SciTech Connect

    Butler, T.; Curtis, O.; Kim, E.; Roberts, S.; Stephenson, R.

    2013-03-01

    As part of the NAHB Research Center Industry Partnership, Southface partnered with TaC Studios, an Atlanta based architecture firm specializing in residential and light commercial design, on the construction of a new test home in Atlanta, GA, in the mixed humid climate zone. This home will serve as a model home for the builder partner and addresses Building America energy savings targets through the planning and implementation of a design package will serve as a basis of design for the builder partner’s future homes. As a BA test house, this home will be evaluated to detail whole house energy use, end use loads, and HVAC and hot water efficiency.

  4. TaC Studios New Construction Test House

    SciTech Connect

    Butler, T.; Curtis, O.; Kim, E.; Roberts, S.; Stephenson, R.

    2013-03-01

    As part of the NAHB Research Center Industry Partnership, Southface partnered with TaC Studios, an Atlanta based architecture firm specializing in residential and light commercial design, on the construction of a new test home in Atlanta, GA in the mixed humid climate zone. This home will serve as a model home for the builder partner and addresses Building America energy savings targets through the planning and implementation of a design package will serve as a basis of design for the builder partner's future homes. As a BA test house, this home will be evaluated to detail whole house energy use, end use loads, and HVAC and hot water efficiency.

  5. Supporting data for senary refractory high-entropy alloy CrxMoNbTaVW

    PubMed Central

    Zhang, B.; Gao, M.C.; Zhang, Y.; Guo, S.M.

    2015-01-01

    This data article is related to the research paper entitled “senary refractory high-entropy alloy CrxMoNbTaVW [1]”. In this data article, the pseudo-binary Cr-MoNbTaVW phase diagram is presented to show the impact of Cr content to the senary Cr-MoNbTaVW alloy system; the sub-lattice site fractions are presented to show the disordered property of the Cr-MoNbTaVW BCC structures; the equilibrium and Scheil solidification results with the actual sample elemental compositions are presented to show the thermodynamic information of the melted/solidified CrxMoNbTaVW samples; and the raw EDS scan data of the arc-melted CrxMoNbTaVW samples are also provided. PMID:26693172

  6. Carrier dynamics of a visible-light-responsive Ta3N5 photoanode for water oxidation.

    PubMed

    Ziani, Ahmed; Nurlaela, Ela; Dhawale, Dattatray S; Silva, Diego Alves; Alarousu, Erkki; Mohammed, Omar F; Takanabe, Kazuhiro

    2015-01-28

    The physicochemical properties of a tantalum nitride (Ta3N5) photoanode were investigated in detail to understand the fundamental aspects associated with the photoelectrochemical (PEC) water oxidation. The Ta3N5 thin films were synthesized using DC magnetron sputtering followed by annealing in air and nitridation under ammonia (NH3). A polycrystalline structure with a dense morphology of the monoclinic Ta3N5 films was obtained. A relatively low absorption coefficient (10(4) to 10(5) cm(-1)) in the visible light range was measured for Ta3N5, consistent with the nature of the indirect band-gap. Ultra-fast spectroscopic measurements revealed that the Ta3N5 with different thicknesses films possess low transport properties and fast carrier recombination (<10 ps). These critical kinetic properties of Ta3N5 as a photoanode may necessitate high overpotentials to achieve appreciable photocurrents for water oxidation (onset ∼0.6 V vs. RHE).

  7. TaC as a diffusion barrier between Si and Cu

    NASA Astrophysics Data System (ADS)

    Laurila, Tomi; Zeng, Kejun; Kivilahti, Jorma K.; Molarius, Jyrki; Suni, Iikka

    2002-04-01

    The reaction mechanisms and related microstructures in the Si/TaC/Cu metallization system have been studied experimentally and theoretically by utilizing ternary Si-Ta-C and Ta-C-Cu phase diagrams as well as activity diagrams calculated at 800 °C. With the help of sheet resistance measurements, Rutherford backscattering spectrometry, x-ray diffraction, scanning electron microscopy, and transmission electron microscopy, the metallization structure with the 70 nm thick TaC barrier layer was observed to fail completely at temperatures above 725 °C because of the formation of large Cu3Si protrusions. However, the formation of amorphous Ta layer containing significant amounts of carbon and oxygen was already observed at the TaC/Cu interface at 600 °C. This layer also constituted an additional barrier layer for Cu diffusion, which occurred only after the crystallization of the amorphous layer. The formation of Ta2O5 was observed at 725 °C with x-ray diffraction, indicating that the oxygen rich amorphous layer had started to crystallize. The formation of SiC and TaSi2 occurred almost simultaneously at 800 °C. The observed reaction structure was consistent with the thermodynamics of the ternary system. The metallization structures with 7 nm and 35 nm TaC barrier layers failed above 550 °C and 650 °C, respectively, similarly because of the formation of Cu3Si. The high formation temperature of TaSi2 and SiC implies high stability of Si/TaC interface, thus making TaC layer a potential candidate to be used as a diffusion barrier for Cu metallization.

  8. Magnetotransport measurements of current induced effective fields in Ta/CoFeB/MgO

    SciTech Connect

    Zhang, Chaoliang; Yamanouchi, Michihiko Ikeda, Shoji; Sato, Hideo; Fukami, Shunsuke; Matsukura, Fumihiro; Ohno, Hideo

    2013-12-23

    We evaluate current-induced effective magnetic fields in perpendicularly magnetized Ta/CoFeB/MgO structures from the external magnetic field angle dependence of the Hall resistance. We confirm the presence of two components of effective fields. The dependence of their magnitudes on Ta thickness implies that both components are related to the spin current in Ta layer generated by the spin Hall effect.

  9. Comparison between Pt/TiO2/Pt and Pt/TaO X /TaO Y /Pt based bipolar resistive switching devices

    NASA Astrophysics Data System (ADS)

    Ho, Patrick W. C.; Odai Hatem, Firas; Almurib, Haider Abbas F.; Nandha Kumar, T.

    2016-06-01

    Nonvolatile memories have emerged in recent years and have become a leading candidate towards replacing dynamic and static random-access memory devices. In this article, the performances of TiO2 and TaO2 nonvolatile memristive devices were compared and the factors that make TaO2 memristive devices better than TiO2 memristive devices were studied. TaO2 memristive devices have shown better endurance performances (108 times more switching cycles) and faster switching speed (5 times) than TiO2 memristive devices. Electroforming of TaO2 memristive devices requires ∼4.5 times less energy than TiO2 memristive devices of a similar size. The retention period of TaO2 memristive devices is expected to exceed 10 years with sufficient experimental evidence. In addition to comparing device performances, this article also explains the differences in physical device structure, switching mechanism, and resistance switching performances of TiO2 and TaO2 memristive devices. This article summarizes the reasons that give TaO2 memristive devices the advantage over TiO2 memristive devices, in terms of electroformation, switching speed, and endurance.

  10. Geology of the Western Part of Los Alamos National Laboratory (TA-3 to TA-16), Rio Grande Rift, New Mexico

    SciTech Connect

    C.J.Lewis; A.Lavine; S.L.Reneau; J.N.Gardner; R.Channell; C.W.Criswell

    2002-12-01

    We present data that elucidate the stratigraphy, geomorphology, and structure in the western part of Los Alamos National Laboratory between Technical Areas 3 and 16 (TA-3 and TA-16). Data include those gathered by geologic mapping of surficial, post-Bandelier Tuff strata, conventional and high-precision geologic mapping and geochemical analysis of cooling units within the Bandelier Tuff, logging of boreholes and a gas pipeline trench, and structural analysis using profiles, cross sections, structure contour maps, and stereographic projections. This work contributes to an improved understanding of the paleoseismic and geomorphic history of the area, which will aid in future seismic hazard evaluations and other investigations. The study area lies at the base of the main, 120-m (400-ft) high escarpment formed by the Pajarito fault, an active fault of the Rio Grande rift that bounds Los Alamos National Laboratory on the west. Subsidiary fracturing, faulting, and folding associated with the Pajarito fault zone extends at least 1,500 m (5,000 ft) to the east of the main Pajarito fault escarpment. Stratigraphic units in the study area include upper units of the Tshirege Member of the early Pleistocene Bandelier Tuff, early Pleistocene alluvial fan deposits that predate incision of canyons on this part of the Pajarito Plateau, and younger Pleistocene and Holocene alluvium and colluvium that postdate drainage incision. We discriminate four sets of structures in the area between TA-3 and TA-16: (a) north-striking faults and folds that mark the main zone of deformation, including a graben in the central part of the study area; (b) north-northwest-striking fractures and rare faults that bound the eastern side of the principal zone of deformation and may be the surface expression of deep-seated faulting; (c) rare northeast-striking structures near the northern limit of the area associated with the southern end of the Rendija Canyon fault; and (d) several small east

  11. Morphological instability of Ag films caused by phase transition in the underlying Ta barrier layer

    SciTech Connect

    Mardani, Shabnam Vallin, Örjan; Wätjen, Jörn Timo; Norström, Hans; Olsson, Jörgen; Zhang, Shi-Li

    2014-08-18

    Wide-bandgap (WBG) semiconductor technologies are maturing and may provide increased device performance in many fields of applications, such as high-temperature electronics. However, there are still issues regarding the stability and reliability of WBG devices. Of particular importance is the high-temperature stability of interconnects for electronic systems based on WBG-semiconductors. For metallization without proper encapsulation, morphological degradation can occur at elevated temperatures. Sandwiching Ag films between Ta and/or TaN layers in this study is found to be electrically and morphologically stabilize the Ag metallization up to 800 °C, compared to 600 °C for uncapped films. However, the barrier layer plays a key role and TaN is found to be superior to Ta, resulting in the best achieved stability, whereas the difference between Ta and TaN caps is negligible. The β-to-α phase transition in the underlying Ta barrier layer is identified as the major cause responsible for the morphological instability observed above 600 °C. It is shown that this phase transition can be avoided using a stacked Ta/TaN barrier.

  12. Reduced-temperature processing and consolidation of ultra-refractory Ta4HfC5

    SciTech Connect

    Gaballa, Osama; Cook, B. A.; Russell, A. M.

    2013-04-26

    TaC, HfC, and WC powders were subjected to high-energy milling and hot pressing to produce Ta4HfC5, a composite of Ta(4)HfC5 + 30 vol.% WC, and a composite of Ta4HfC5 + 50 vol.% WC. Sub-micron powders were examined after four different milling intervals prior to hot pressing. XRD was used to verify proper phase formation. SEM, relative density, and hardness measurements were used to examine the resulting phases. Hot pressed compacts of Ta4HfC5 showed densification as high as 98.6% along with Vickers hardness values of 21.4 GPa. Similarly, Ta4HfC5 + 30 vol.% WC exhibited 99% densification with a Vickers hardness of 22.5 GPa. These levels of densification were achieved at 1500 degrees C, which is lower than any previously reported sintering temperature for Ta4HfC5. Microhardness values measured in this study were higher than those previously reported for Ta4HfC5. The WC additions to Ta4HfC5 were found to improve densification and increase microhardness. (C) 2013 Elsevier Ltd. All rights reserved.

  13. Ultra-High Strength and Ductile Lamellar-Structured Powder Metallurgy Binary Ti-Ta Alloys

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Xu, Shenghang; Wang, Xin; Li, Kaiyang; Liu, Bin; Wu, Hong; Tang, Huiping

    2016-03-01

    Ultra-high strength and ductile powder metallurgy (PM) binary Ti-20at.%Ta alloy has been fabricated via sintering from elemental Ti and Ta powders and subsequent hot swaging and annealing. The microstructural evolution and mechanical properties in each stage were evaluated. Results show that inhomogeneous microstructures with Ti-rich and Ta-rich areas formed in the as-sintered Ti-Ta alloys due to limited diffusion of Ta. In addition, Kirkendall porosity was observed as a result of the insufficient diffusion of Ta. Annealing at 1000°C for up to 24 h failed to eliminate the pores. Hot swaging eliminated the residual sintering porosity and created a lamellar microstructure, consisting of aligned Ta-enriched and Ti-enriched phases. The hot-swaged and annealed PM Ti-20Ta alloy achieved an ultimate tensile strength of 1600 MPa and tensile elongation of more than 25%, due to its unique lamellar microstructure including the high toughness of Ta-enriched phases, the formation of α phase in the β matrix and the refined lamellae.

  14. (Ag,Cu)-Ta-O ternaries as high-temperature solid-lubricant coatings.

    PubMed

    Gao, Hongyu; Otero-de-la-Roza, Alberto; Gu, Jingjing; Stone, D'Arcy; Aouadi, Samir M; Johnson, Erin R; Martini, Ashlie

    2015-07-22

    Ternary oxides have gained increasing attention due to their potential use as solid lubricants at elevated temperatures. In this work, the tribological properties of three ternary oxides-AgTaO3, CuTaO3, and CuTa2O6-were studied using a combination of density-functional theory (DFT), molecular dynamics (MD) simulations with newly developed empirical potential parameters, and experimental measurements (AgTaO3 and CuTa2O6 only). Our results show that the MD-predicted friction force follows the trend AgTaO3 < CuTaO3 < CuTa2O6, which is consistent with the experimentally measured coefficients of friction. The wear performance from both MD and experiment exhibits the opposite trend, with CuTa2O6 providing the best resistance to wear. The sliding mechanisms are investigated using experimental characterization of the film composition after sliding, quantification of Ag or Cu cluster formation at the interface during the evolution of the film in MD, and DFT energy barriers for atom migration on the material surface. All our observations are consistent with the hypothesis that the formation of metal (or metal oxide) clusters on the surface are responsible for the friction and wear behavior of these materials. PMID:26106877

  15. Interface structure and sliding friction at a Ta/Al interface

    NASA Astrophysics Data System (ADS)

    Ravelo, R.; Germann, T. C.; Hammerberg, J. E.; Holian, B. L.; Kress, J. D.

    2003-03-01

    We have carried out large-scale molecular dynamics simulations of sliding Ta/Al interfaces. The atomic interactions are modeled employing Embedded Atom Method (EAM) potentials. These potentials predict strong bonding between Ta and Al atoms consistent with first principles simulations and with experimentally known heats of formation of Ta-Al alloys. The Al(100)/Ta(100) interface is characterized by near epitaxial growth of Al onto the Ta for the first 3 layers followed by a deformed transition region that leads to fcc stacking after about 5 layers. Ab-initio Molecular Dynamics simulations also show near epitaxial growth of Al on Ta(100). The Al(111)/Ta(110) interface, by contrast, exhibits no structural transformation of the Al layers which maintain their six-fold symmetry. The velocity dependence of the frictional force as a function of velocity has been determined for both Al(100)/Ta(100) and Al(111)/Ta(110) sliding using large-scale MD simulations. The frictional force shows a characteristic maximum at velocities of order 0.1 c, where c is the transverse sound speed in Al, followed by a power-law decrease.

  16. Electrochemical oxide nanotube formation on the Ti-35Ta-xHf alloys for dental materials.

    PubMed

    Moon, Byung-Hak; Jeong, Yong-Hoon; Choe, Han-Cheol

    2011-08-01

    In this study, we investigated the electrochemical oxide nanotube formation on the Ti-35Ta-xHf alloys for dental materials. The Ti-35Ta-xHf alloys contained from 3 wt.% to 15 wt.% Hf were manufactured by arc melting furnace. The nanotube oxide layers were formed on Ti-35Ta-xHf alloy by anodic oxidation method in 1 M H3PO4 electrolytes containing 0.5 wt.% NaF and 0.8 wt.% NaF at room temperature. The surface characteristics of Ti-35Ta-xHf alloy and nanotube morphology were determined by FE-SEM, STEM, and XRD. The nano-porous surface of Ti-35Ta-xHf alloys showed in 0.5 wt% NaF solution and nanotubular surface showed in 0.8 wt% NaF solution, respectively. The highly ordered nanotube layer without regular knots was formed on the Ti-35Ta-15Hf alloy in the 0.5 wt% NaF solution compared to on Ti-35Ta-3Hf and Ti-35Ta-7Hf alloys in 0.8 wt% NaF solution. Also, the nanotube length of Ti-35Ta-xHf alloys increased as Hf content increased.

  17. Overexpression of a Triticum aestivum Calreticulin gene (TaCRT1) Improves Salinity Tolerance in Tobacco

    PubMed Central

    Song, Min; Wang, Yun; Xu, Wenqi; Wu, Lintao; Wang, Hancheng; Ma, Zhengqiang

    2015-01-01

    Calreticulin (CRT) is a highly conserved and abundant multifunctional protein that is encoded by a small gene family and is often associated with abiotic/biotic stress responses in plants. However, the roles played by this protein in salt stress responses in wheat (Triticum aestivum) remain obscure. In this study, three TaCRT genes were identified in wheat and named TaCRT1, TaCRT2 and TaCRT3-1 based on their sequence characteristics and their high homology to other known CRT genes. Quantitative real-time PCR expression data revealed that these three genes exhibit different expression patterns in different tissues and are strongly induced under salt stress in wheat. The calcium-binding properties of the purified recombinant TaCRT1 protein were determined using a PIPES/Arsenazo III analysis. TaCRT1 gene overexpression in Nicotiana tabacum decreased salt stress damage in transgenic tobacco plants. Physiological measurements indicated that transgenic tobacco plants showed higher activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) than non-transgenic tobacco under normal growth conditions. Interestingly, overexpression of the entire TaCRT1 gene or of partial TaCRT1 segments resulted in significantly higher tolerance to salt stress in transgenic plants compared with their WT counterparts, thus revealing the essential role of the C-domain of TaCRT1 in countering salt stress in plants. PMID:26469859

  18. Synthesis of Solar-Light-Responsive ZnO/TaON Nanocomposite and Their Photocatalytic Activity.

    PubMed

    Kim, Tae-Ho; Jo, Yong-Hyun; Lee, Soo-Wohn; Cho, Sung-Hun; Kim, Seung-Ho

    2015-09-01

    The effects of the preparation conditions of ZnO-modified TaON on the photocatalytic activity for degradation of rhodamine B dye (Rh. B) under simulated solar light were investigated. The ZnO/TaON nanocomposite were prepared by loading particulate Ta2O5 with ZnO using different ZnO contents, followed by thermal nitridation at 1123 K for 5 h under NH3 flow (20 ml min(-1)). The as-prepared samples were characterized by XRD, UV-Vis-DRS, and SEM-EDX. The results revealed that the band gap energy absorption edge of as prepared nanocomposite samples was shifted to a longer wavelength as compared to ZnO and Ta2O5, and the 60 wt% ZnO/TaON nanocomposite exhibited the highest percentage (99.2%) of degradation of Rh. B and the highest reaction rate constant (0.0137 min(-1)) in 4 h which could be attributed to the enhanced absorption of the ZnO/TaON nanocomposite photocatalyst. Hence, these results suggest that the ZnO/TaON nanocomposite exhibits enhanced photocatalytic activity for the degradation of rhodamine B under simulated solar light irradiation in comparison to the commercial ZnO, Ta2O5, and TaON.

  19. HREM of electron-beam-induced damage in L-Ta 2O 5

    NASA Astrophysics Data System (ADS)

    Wagner, T. R.

    1991-04-01

    Samples of L-Ta 2O 5 exposed to a high current density electron beam were observed by high resolution electron microscopy (HREM) to reduce to suboxide and metallic Ta phases. Data are presented for crystals aligned along [001], [020], [200], and [130], in which surface areas are seen to reduce to Ta 2O, TaO 2, bcc Ta, or a β-Ta phase via an amorphous intermediate phase. The driving force appears to involve desorption of oxygen stimulated by electronic transitions (DIET), and the possible involvement of the "infinitely adaptive nature" of the initial L-Ta 2O 5 structure in the damage process is discussed. Comparison of results obtained from an ultrahigh vacuum HREM to those from a conventional HREM suggests that contamination effects in lower vacuum systems influences the reliability of the results, especially in complex systems like Ta&1bO. Finally, the results follow a symmetry selection rule, which explains why L-Ta 2O 5 does not reduce to the monoxide phase as observed in similar experiments with TiO 2, V 2O 5, and Nb 2O 5.

  20. Spectroscopy of TaN in Support of Fundamental Physics

    NASA Astrophysics Data System (ADS)

    Mawhorter, Richard; Sharfi, David; Kim, Yongrak; Kokkin, Damian; Bouchard, Jacob; Steimle, Timothy

    2016-05-01

    Tantalum nitride, TaN, has been recently identified as a leading candidate for extending the study of T, P-odd effects in the nuclear realm to include proton, neutron, and quark electric dipole moments (EDM) and beyond. This is primarily due to enhancements in the interaction of electrons with the nuclear magnetic quadrupole moment (MQM) and the resulting parity-violating effects. Study of the dispersed laser induced fluorescence resulting from the excitation of the 17570.80 (Ω = 0+) , 18427.38 (Ω = 0+) , 19216.80 (Ω = 1), and 19396.78 (Ω = 1) bands above the X1Σ+ (v = 0) ground state of TaN near 569 nm, 543 nm, 520 nm, and 515 nm has enabled a determination of the branching ratios and transition dipole moments of all 4 states. Radiative lifetimes of 454(32) ns, 479(12) ns, 333(4) ns, and 480(17) ns respectively were measured from an analysis of the fluorescence decay curves, and potential optical pumping approaches for both populating and detecting the parity-violation sensitive 3Δ1 state are proposed. Further experiments using CW laser excitation have enabled the observation of the hyperfine structure of several bands in the gateway 18427.38 (Ω = 0+) to X1Σ+ (v = 0) transition, and analysis of these complex spectra is underway. DK, JB, and TS acknowledge support from NSF CHE-1265885, as do RM, DS, and YK from Pomona College.

  1. Synthesis and characterization of Ti-Ta-Nb-Mn foams.

    PubMed

    Aguilar, C; Guerra, C; Lascano, S; Guzman, D; Rojas, P A; Thirumurugan, M; Bejar, L; Medina, A

    2016-01-01

    The unprecedented increase in human life expectancy have produced profound changes in the prevailing patterns of disease, like the observed increased in degenerative disc diseases, which cause degradation of the bones. Ti-Nb-Ta alloys are promising materials to replace the damaged bone due to their excellent mechanical and corrosion resistance properties. In general metallic foams are widely used for medical application due to their lower elastic moduli compare to bulk materials. In this work we studied the synthesis of 34Nb-29Ta-xMn (x: 2, 4 and 6 wt.% Mn) alloy foams (50% v/v) using ammonium hydrogen carbonate as a space holder. Alloys were produced through mechanical alloying in a planetary mill for 50h. Green compacts were obtained by applying 430 MPa pressure. To remove the space holder from the matrix the green compacts were heated to 180 °C for 1.5h and after sintered at 1300 °C for 3h. Foams were characterized by x-ray diffraction, scanning, transmission electron microscopy and optical microscopy. The elastic modulus of the foam was measured as ~30 GPa, and the values are almost equal to the values predicted using various theoretical models. PMID:26478329

  2. Synthesis and characterization of Ti-Ta-Nb-Mn foams.

    PubMed

    Aguilar, C; Guerra, C; Lascano, S; Guzman, D; Rojas, P A; Thirumurugan, M; Bejar, L; Medina, A

    2016-01-01

    The unprecedented increase in human life expectancy have produced profound changes in the prevailing patterns of disease, like the observed increased in degenerative disc diseases, which cause degradation of the bones. Ti-Nb-Ta alloys are promising materials to replace the damaged bone due to their excellent mechanical and corrosion resistance properties. In general metallic foams are widely used for medical application due to their lower elastic moduli compare to bulk materials. In this work we studied the synthesis of 34Nb-29Ta-xMn (x: 2, 4 and 6 wt.% Mn) alloy foams (50% v/v) using ammonium hydrogen carbonate as a space holder. Alloys were produced through mechanical alloying in a planetary mill for 50h. Green compacts were obtained by applying 430 MPa pressure. To remove the space holder from the matrix the green compacts were heated to 180 °C for 1.5h and after sintered at 1300 °C for 3h. Foams were characterized by x-ray diffraction, scanning, transmission electron microscopy and optical microscopy. The elastic modulus of the foam was measured as ~30 GPa, and the values are almost equal to the values predicted using various theoretical models.

  3. Corrosion behaviour of welds and Ta in liquid lead

    NASA Astrophysics Data System (ADS)

    Heinzel, A.; Müller, G.; Weisenburger, A.

    2016-02-01

    Four specimens, P91 welded by friction stir welding with and without post heat treatment, P91 electromagnetic pulse welded (EMP) and 14Cr ODS (explosive welding) were exposed at 550 °C for up to 2131 h to Pb containing 10-6 wt% oxygen. After the exposure none of the samples showed dissolution attack, all were protected by an oxide layer at the surface. Nearly no effect on the oxidation due to welding was found in both friction stir welded specimens. Severe deformation and partial melting during explosive welding result in a slower oxide layer growth within the welding zone. The EMP sample was tested as delivered without post-heat treatment. No Pb penetrated into the tiny gap between the welded parts. After the test, the gap is filled up with oxides. Additionally, Ta, discussed as a pump impeller material, was exposed to Pb and PbBi at different temperatures (400-900 °C) and oxygen concentrations in liquid metal (saturated, 10-6 wt%, 10-8 wt% and reduced (<<10-8 wt%). Only the Ta specimens exposed to Pb with highly reduced oxygen content showed nearly no attack. All the others exhibited oxide scale formation that becomes severe above 400 °C test temperature.

  4. Vibrational spectroscopy of Ga+ ion implanted ta-C films

    NASA Astrophysics Data System (ADS)

    Berova, M.; Sandulov, M.; Tsvetkova, T.; Bischoff, L.; Boettger, R.; Abrashev, M.

    2016-02-01

    In the present work, low energy Ga+ ion beam implantation was used for the structural and optical properties modification of tetrahedral amorphous carbon (ta-C) thin films, using gallium (Ga+) as the ion species. Thin film samples (d∼40nm) of ta-C, deposited by filtered cathodic vacuum arc (FCVA), have been implanted with Ga+ at ion energy E = 20 keV and ion doses D=3.1014÷3.1015 cm-2. The Ga+ ion beam induced structural modification of the implanted material results in a considerable change of its optical properties, displayed in a significant shift of the optical absorption edge to lower photon energies as obtained from optical transmission measurements. This shift is accompanied by a considerable increase of the absorption coefficient (photo-darkening effect) in the measured photon energy range (0.5÷3.0 eV). These effects could be attributed both to additional defect introduction and increased graphitisation, as well as to accompanying formation of bonds between the implanted ions and the host atoms of the target, as confirmed by infra-red (IR) and Raman measurements. The optical contrast thus obtained (between implanted and unimplanted film material) could be made use of for information archiving, in the area of high-density optical data storage, while using focused Ga+ ion beams.

  5. Electronic structure of the bcc transition metals: Thermoreflectance studies of bulk V, Nb, Ta, and. cap alpha. TaH/sub x/

    SciTech Connect

    Rosei, R.; Colavita, E.; Franciosi, A.; Weaver, J.H.; Peterson, D.T.

    1980-04-15

    Thermoreflectance studies of bulk samples of V, Nb, Ta, and ..cap alpha..-phase TaH/sub x/ are reported and the results interpreted in terms of recent band calculations. The first interband transition is identified as a transition involving the ..sigma.. band at E/sub F/. An M/sub 3/ critical-point transition is attributed to states at N. Significant changes induced by interstitial hydrogen in solid solution ..cap alpha..-TaH/sub x/ are observed and interpreted as due to hybridization and lowering of the N/sup prime//sub 1/ eigenenergy.

  6. Reconnaissance of the Hydrogeology of Ta'u, American Samoa

    USGS Publications Warehouse

    Izuka, Scot K.

    2005-01-01

    Analysis of existing data and information collected on a reconnaissance field visit supports a conceptual model of ground-water occurrence in Ta'u, American Samoa, in which a thin freshwater lens exists in a predominantly high-permeability aquifer that receives high rates of recharge. Because the freshwater lens is thin throughout most of the island, the productivity of wells, especially those near the coast where the lens is the thinnest, is likely to be limited by saltwater intrusion. The landfill in northwestern Ta'u is closer to the north coast of the island than to any of the existing or proposed well sites. Although this may indicate that ground water beneath the landfill would flow away from the existing and proposed well sites, this interpretation may change depending on the hydraulic properties of a fault and rift zone in the area. Of four plausible scenarios tested with a numerical ground-water flow model, only one scenario indicated that ground water from beneath the landfill would flow toward the existing and proposed well sites; the analysis does not, however, assess which of the four scenarios is most plausible. The analysis also does not consider the change in flow paths that will result from ground-water withdrawals, dispersion of contaminants during transport by ground water, other plausible hydrogeologic scenarios, transport of contaminants by surface-water flow, or that sources of contamination other than the landfill may exist. Accuracy of the hydrologic interpretations in this study is limited by the relatively sparse data available for Ta'u. Understanding water resources on Ta'u can be advanced by monitoring rainfall, stream-flow, evaporation, ground-water withdrawals, and water quality, and with accurate surveys of measuring point elevations for all wells and careful testing of well-performance. Assessing the potential for contaminants in the landfill to reach existing and proposed well sites can be improved with additional information on the

  7. Interaction of Ta-O and perpendicular magnetic anisotropy of Ta/Pd (0-2.4 nm)/Co2FeAl0.5Si0.5/MgO/Ta structured films

    NASA Astrophysics Data System (ADS)

    You, C. Y.; Fu, H. R.; Zhang, X.; Tian, N.; Wang, P. W.

    2015-03-01

    Perpendicular magnetic anisotropy (PMA) was realized by inserting Pd layer into the stack of Ta/Pd (0-2.4 nm)/Co2FeAl0.5Si0.5/MgO/Ta. The realization of PMA is accompanied by the (Co, Fe)-O reduction at Co2FeAl0.5Si0.5/MgO interface under annealing. Without inserting Pd layer, the annealed Ta/Co2FeAl0.5Si0.5/MgO/Ta film presents an in-plane magnetization. Through X-ray photoelectron spectrometry analyzes, it was found that the oxygen was enriched at the interface of Ta/Co2FeAl0.5Si0.5. This work clarifies that the inserted Pd layer effectively blocks the diffusion of interfacial oxygen to Ta layer, achieving the beneficial redox reaction at Co2FeAl0.5Si0.5/MgO interface to realize PMA.

  8. Interfacial electronic structure-modulated magnetic anisotropy in Ta/CoFeB/MgO/Ta multilayers

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Wang, Kai You; Wu, Zheng Long; Jiang, Shao Long; Yang, Guang; Liu, Yang; Teng, Jiao; Yu, Guang Hua

    2014-09-01

    We have observed several unexpected phenomena when a trace amount of Fe atoms is deposited onto the CoFeB/MgO interface in Ta/CoFeB/MgO/Ta multilayers. With the nominal thickness of the introduced Fe atoms (tFe) varying from 0 to 0.1 Å, the effective magnetic anisotropy energy (Keff) of annealed multilayers is remarkably enhanced from 1.28 × 106 erg/cm3 to 2.14 × 106 erg/cm3. As tFe further increasing, the Keff decreases and even becomes negative when tFe > 1 Å, indicating the change from perpendicular magnetic anisotropy to in-plane magnetic anisotropy. The analysis by X-ray photoelectron spectrometer reveals that the Fe atoms at annealed CoFeB/MgO interface show different electronic structures as tFe increasing, which combine with O atoms to form FeOx (x < 1), Fe2O3, and Fe3O4, respectively, leading to modulation of Fe 3d-O 2p orbital hybridization and thus the Keff. On the other hand, we find that the introduction of Fe atoms also helps to reduce the multilayers' magnetic damping.

  9. Interfacial electronic structure-modulated magnetic anisotropy in Ta/CoFeB/MgO/Ta multilayers

    SciTech Connect

    Chen, Xi; Jiang, Shao Long; Yang, Guang; Liu, Yang; Teng, Jiao; Yu, Guang Hua; Wang, Kai You; Wu, Zheng Long

    2014-09-01

    We have observed several unexpected phenomena when a trace amount of Fe atoms is deposited onto the CoFeB/MgO interface in Ta/CoFeB/MgO/Ta multilayers. With the nominal thickness of the introduced Fe atoms (t{sub Fe}) varying from 0 to 0.1 Å, the effective magnetic anisotropy energy (K{sub eff}) of annealed multilayers is remarkably enhanced from 1.28 × 10{sup 6 }erg/cm{sup 3} to 2.14 × 10{sup 6 }erg/cm{sup 3}. As t{sub Fe} further increasing, the K{sub eff} decreases and even becomes negative when t{sub Fe} > 1 Å, indicating the change from perpendicular magnetic anisotropy to in-plane magnetic anisotropy. The analysis by X-ray photoelectron spectrometer reveals that the Fe atoms at annealed CoFeB/MgO interface show different electronic structures as t{sub Fe} increasing, which combine with O atoms to form FeO{sub x} (x < 1), Fe{sub 2}O{sub 3}, and Fe{sub 3}O{sub 4}, respectively, leading to modulation of Fe 3d-O 2p orbital hybridization and thus the K{sub eff}. On the other hand, we find that the introduction of Fe atoms also helps to reduce the multilayers' magnetic damping.

  10. Low-Level, Measured Response of Los Alamos National Laboratories TA 16 - Building 411 and TA 8 - Building 23 to Direct Flash Attachment of Lightning

    SciTech Connect

    Dinallo, Michael A.; Holmes, Parris; Merewether, Kimball O.; Morris, Marvin E.

    1999-02-01

    On September 24, 25, 28, and 29, 1998 and on October 19 and 23, 1998, transfer impedance measurements were made on Los Alamos National Laboratories TA 16 - Building 411 and TA 8-- Building 23 to characterize their interior open-circuit voltage response to a direct lightning flash attachment to the structures. The theory, history, measurement methods and equipment, and specific measured results are detailed. The measured results demonstrate that if the remaining metallic penetrations are bonded, then the rebar of the two structures is sufficiently well connected to form a Faraday cage that reduces the maximum open-circuit voltage inside the structure to a sufficiently low level that the required standoff distance to prevent arcing to explosive assemblies is 6.8 inches for TA 16 - Building 411 and is 11.5 inches for TA 8 - Building 23.

  11. Titanium-Substituted Polyoxotantalate Clusters Exhibiting Wide pH Stabilities: [Ti2 Ta8 O28 ](8-) and [Ti12 Ta6 O44 ](10.).

    PubMed

    Son, Jung-Ho; Casey, William H

    2016-09-26

    Two new substituted polyoxotantalate clusters, [Ti2 Ta8 O28 ](8-) and [Ti12 Ta6 O44 ](10-) , considerably expand the pH range where tantalates persist in aqueous solution. The structures of [Ti2 Ta8 O28 ](8-) and [Ti12 Ta6 O44 ](10-) are reported as tetramethylammonium salts after synthesis at hydrothermal conditions in aqueous solution. These Ti-substituted polyoxotantalate clusters have analogues among recently discovered niobates, but are slightly larger and more persistent in solution. Most importantly, they exhibit a much wider range of pH stability than the familiar hexatantalate cluster, which is the only other tantalate known to be stable at highly basic pH conditions. These molecules are kinetically stable to near-neutral pH, making them excellent synthons for further development into materials and catalysts, and an significant advance in adapting tantalates for use in aqueous solutions. PMID:27458815

  12. Nb/Ta - Zr/Hf Fractionations during Subduction: Implications for the'Missing' Nb.

    NASA Astrophysics Data System (ADS)

    Zateslo, T.; Bizimis, M.; Salters, V. J.; Stern, C.; Taylor, R. N.

    2008-12-01

    Key differences between the chemical composition of terrestrial materials and those of meteorites have led to the suggestion that a 'hidden' high Nb/Ta reservoir exists in the Earth's mantle. In order to test this hypothesis we must identify the processes that can create such a reservoir. Here we report the first high precision HFSE data on products of the subduction processes thought to fractionate Nb from Ta: boninites (hydrous melting), adakites (slab melting), OIBs (Koolau, Walvis: plume with recycled oceanic crust), as well as kimberlites and lamproites. We developed a new method for the high precision determination of Nb, Ta, Zr, Hf concentrations based on a modified version of standard addition. All analyses were performed on a single collector ICPMS (ELEMENT 1), using Y and Yb as internal standards to correct for instrumental drift during the unspiked -spiked sample sequence. Concentrations are calculated using a York- type regression that accounts for all measured and propagated errors. Long-term reproducibility (multiple dissolutions and multiple spike solutions) for the standards BHVO-1, BIR-1 AGV-1 and BCR-1 are better than 0.8% (1s) for Nb/Ta and Zr/Hf ratios. The advantages of this method compared to previous methods are fast throughput, no column chemistry and low blanks. The Koolau and Walvis Ridge lavas have subchondritic Nb/Ta for a given Zr/Hf, overlapping other OIB suites and show no evidence for a recycled, high Nb/Ta reservoir in their source. OIB, considered as a group, have relatively constant Nb/Ta (15-16) but more variable Zr/Hf (35-50). In contrast, boninites (Chichi Jima) have significantly subchondritic Nb/Ta (4-12) at near constant Zr/Hf (35), while adakites (South Andes) extend to near chondritic Nb/Ta (13-19) at more variable Zr/Hf (30-40). The adakites showing the least evidence for crustal contamination have the highest Nb/Ta. The arc lavas cross the OIB trend at near right angle on a Nb/Ta vs. Zr/Hf plot having larger Nb/Ta

  13. Structural and electronic investigations of PbTa4O11 and BiTa7O19 constructed from α-U3O8 types of layers

    NASA Astrophysics Data System (ADS)

    Boltersdorf, Jonathan; Maggard, Paul A.

    2015-09-01

    The PbTa4O11 and BiTa7O19 phases were prepared by ion-exchange and solid-state methods, respectively, and their structures were characterized by neutron time-of-flight diffraction and Rietveld refinement methods (PbTa4O11, R 3 (No. 146), a=6.23700(2) Å, c=36.8613(1) Å; BiTa7O19, P 6 bar c 2 (No. 188), a=6.2197(2) Å, c=20.02981(9) Å). Their structures are comprised of layers of TaO6 octahedra surrounded by three 7-coordinate Pb(II) cations or two 8-coordinate Bi(III) cations. These layers alternate down the c-axis with α-U3O8 types of single and double TaO7 pentagonal bipyramid layers. In contrast to earlier studies, both phases are found to crystallize in noncentrosymmetric structures. Symmetry-lowering structural distortions within PbTa4O11, i.e. R 3 bar c →R3, are found to be a result of the displacement of the Ta atoms within the TaO7 and TaO6 polyhedra, towards the apical and facial oxygen atoms, respectively. In BiTa7O19, relatively lower reaction temperatures leads to an ordering of the Bi/Ta cations within a lower-symmetry structure, i.e., P63/mcm→ P 6 bar c 2 . In the absence of Bi/Ta site disorder, the Ta-O-Ta bond angles decrease and the Ta-O bond distances increase within the TaO7 double layers. Scanning electron microscopy images reveal two particle morphologies for PbTa4O11, hexagonal rods and finer irregularly-shaped particles, while BiTa7O19 forms as aggregates of irregularly-shaped particles. Electronic-structure calculations confirm the highest-energy valence band states are comprised of O 2p-orbitals and the respective Pb 6s-orbital and Bi 6s-orbital contributions. The lowest-energy conduction band states are composed of Ta 5d-orbital contributions that are delocalized over the TaO6 octahedra and layers of TaO7 pentagonal bipyramids. The symmetry-lowering distortions in the PbTa4O11 structure, and the resulting effects on its electronic structure, lead to its relatively higher photocatalytic activity compared to similar structures without

  14. Electron Cloud at Low Emittance in CesrTA

    SciTech Connect

    Palmer, Mark; Alexander, James; Billing, Michael; Calvey, Joseph; Conolly, Christopher; Crittenden, James; Dobbins, John; Dugan, Gerald; Eggert, Nicholas; Fontes, Ernest; Forster, Michael; Gallagher, Richard; Gray, Steven; Greenwald, Shlomo; Hartill, Donald; Hopkins, Walter; Kreinick, David; Kreis, Benjamin; Leong, Zhidong; Li, Yulin; Liu, Xianghong; /more authors..

    2012-07-06

    The Cornell Electron Storage Ring (CESR) has been reconfigured as a test accelerator (CesrTA) for a program of electron cloud (EC) research at ultra low emittance. The instrumentation in the ring has been upgraded with local diagnostics for measurement of cloud density and with improved beam diagnostics for the characterization of both the low emittance performance and the beam dynamics of high intensity bunch trains interacting with the cloud. A range of EC mitigation methods have been deployed and tested and their effectiveness is discussed. Measurements of the electron cloud's effect on the beam under a range of conditions are discussed along with the simulations being used to quantitatively understand these results.

  15. Suboxide/subnitride formation on Ta masks during magnetic material etching by reactive plasmas

    SciTech Connect

    Li, Hu; Muraki, Yu; Karahashi, Kazuhiro; Hamaguchi, Satoshi

    2015-07-15

    Etching characteristics of tantalum (Ta) masks used in magnetoresistive random-access memory etching processes by carbon monoxide and ammonium (CO/NH{sub 3}) or methanol (CH{sub 3}OH) plasmas have been examined by mass-selected ion beam experiments with in-situ surface analyses. It has been suggested in earlier studies that etching of magnetic materials, i.e., Fe, Ni, Co, and their alloys, by such plasmas is mostly due to physical sputtering and etch selectivity of the process arises from etch resistance (i.e., low-sputtering yield) of the hard mask materials such as Ta. In this study, it is shown that, during Ta etching by energetic CO{sup +} or N{sup +} ions, suboxides or subnitrides are formed on the Ta surface, which reduces the apparent sputtering yield of Ta. It is also shown that the sputtering yield of Ta by energetic CO{sup +} or N{sup +} ions has a strong dependence on the angle of ion incidence, which suggests a correlation between the sputtering yield and the oxidation states of Ta in the suboxide or subnitride; the higher the oxidation state of Ta, the lower is the sputtering yield. These data account for the observed etch selectivity by CO/NH{sub 3} and CH{sub 3}OH plasmas.

  16. Surgeons’ assessment of internal anal sphincter nerve supply during TaTME - inbetween expectations and reality

    PubMed Central

    Kneist, Werner; Hanke, Laura; Kauff, Daniel W.; Lang, Hauke

    2016-01-01

    Abstract Background: Intraoperative identification of nerve fibers heading from the inferior rectal plexus (IRP) to the internal anal sphincter (IAS) is challenging. The transanal total mesorectal excision (TaTME) is said to better preserve pelvic autonomic nerves. The aim of this study was to investigate the nerve identification rates during TaTME by transanal visual and electrophysiological assessment. Material and methods: A total of 52 patients underwent TaTME for malignant conditions. The IRP with its posterior branches to the IAS and the pelvic splanchnic nerves (PSN) were visually assessed in 20 patients (v-TaTME). Electrophysiological nerve identification was performed in 32 patients using electric stimulation under processed electromyography of IAS (e-TaTME). Results: The indication profile for TaTME was comparable between the v-TaTME and the e-TaTME group. The identification of IRP was more meaningful under electrophysiological assessment than under visual assessment for the left pelvic side (81% vs. 45%, p = 0.008) as well as the right pelvic side (78% vs. 45%, p = 0.016). The identification rates for PSN did not significantly differ between both groups, respectively (81% vs. 75%, p = 0.420 and 84% vs. 70%, p = 0.187). Conclusions: The transanal approach facilitated visual identification of IAS nerve supply. In combination with electrophysiological nerve assessment the identification rate almost doubled. For further insights functional data are needed. PMID:27333465

  17. Using the TA to Prepare Graduate Students for Research and Employment

    NASA Astrophysics Data System (ADS)

    Heller, Kenneth

    One of the most underused components of the physics graduate program is the time spent being a teaching assistant (TA). Often the TA duties consist of grading and trying to help undergraduates survive a physics course. How those duties are accomplished is left to each TA. The most common TA preparation, if it exists, has a narrow focus on the class being taught. Preparation consists of describing, or perhaps practicing, specific teaching skills and gaining familiarity with the equipment used in the laboratory portion of the class. Instead TAs can be integrated into the entire course in which they function so that they learn the course as a system. This means treating a course in the same way one approaches a research project with the TAs as members of the research team headed by a faculty advisor. TA preparation is broadened and support includes the management, teamwork, and communication skills necessary. This makes the TAs more efficient and effective teachers while explicitly connecting the TA experience to the ``soft'' skills they need in their own research careers whether in industry, national laboratories, or academia. This talk describes such a program, functioning for over 20 years at the University of Minnesota, that takes no more time than the usual TA but results in graduate students that are more satisfied with their TA experience, are better prepared to function in research groups, and provide a better classroom experience for their undergraduate students.

  18. Along the Ta Diffusion Path Through a Boron and Oxygen Containing Tri-layer Structure

    NASA Astrophysics Data System (ADS)

    Ying, Ji-Feng; Ji, Rong; Wang, Chen Chen; Ter Lim, Sze; Xie, Huiqing; Gerard, Ernult F.

    2014-08-01

    Diffusion and migration of elements are commonly observed in the fabrication of multilayer thin-film devices, including those of STT-RAM. The CoFeB/MgO/CoFeB tri-layer thin-film stack has been widely used in the design of STT-RAM devices as the functional magnetic-tunnel-junction (MTJ) structure. Such issues faced in the fabrication of these devices have been extensively researched from the stand point of engineering the materials property and structure to achieve the best MTJ performance. In this work, we conducted a detailed examination of the chemical-state change of the Ta and B in a CoFeB/MgO/CoFeB/Ta film stack by using x-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry. We showed that the chemical-state change of Ta and B is a result of the Ta diffusion phenomena through the CoFeB/MgO/CoFeB tri-layer structure. In particular, we report the evidences of the formation of TaB x O y compound at some considerable depth away from the Ta layer. Also of value to XPS spectroscopy, the Ta binding energy for such TaB x O y compound is reported for the first time.

  19. "Forest Grove School District v. T.A." Supreme Court Case: Implications for School Psychology Practice

    ERIC Educational Resources Information Center

    Dixon, Shauna G.; Eusebio, Eleazar C.; Turton, William J.; Wright, Peter W. D.; Hale, James B.

    2011-01-01

    The 2009 "Forest Grove School District v. T.A." United States Supreme Court case could have significant implications for school psychology practice. The Court ruled that the parents of a student with a disability were entitled to private school tuition reimbursement even though T.A. had not been identified with a disability or previously provided…

  20. Physical and chemical characterization of combinatorial metal gate electrode Ta-C-N library film

    SciTech Connect

    Chang, K.-S.; Green, M. L.; Levin, I.; Hattrick-Simpers, J. R.; Jaye, C.; Fischer, D. A.; Takeuchi, I.; De Gendt, S.

    2010-05-10

    This paper reports comprehensive structural and chemical analyses for the combinatorial Ta-C-N/HfO{sub 2} system, crucial data for understanding the electrical properties of Ta-C-N/HfO{sub 2}. Combinatorial Ta-C-N 'library' (composition spread) films were deposited by magnetron sputtering. Electron probe wavelength dispersive spectroscopy and x-ray fluorescence-yield near-edge spectroscopy were used to quantitatively determine the composition across these films. Scanning x-ray microdiffractometry determined that a solid solution of Ta(C,N){sub x} forms and extends to compositions (0.3<=Ta<=0.5 and 0.57<=Ta<=0.67) that were previously unknown. The thermal stability of the Ta-C-N/HfO{sub 2} library was studied using high resolution transmission electron microscopy, which shows Ta-C-N/HfO{sub 2}/SiO{sub 2}/Si exhibiting good thermal stability up to 950 deg. C.

  1. Wheat Transcription Factor TaAREB3 Participates in Drought and Freezing Tolerances in Arabidopsis

    PubMed Central

    Wang, Jingyi; Li, Qian; Mao, Xinguo; Li, Ang; Jing, Ruilian

    2016-01-01

    AREB (ABA response element binding) proteins in plants play direct regulatory roles in response to multiple stresses, but their functions in wheat (Triticum aestivum L.) are not clear. In the present study, TaAREB3, a new member of the AREB transcription factor family, was isolated from wheat. Sequence analysis showed that the TaAREB3 protein is composed of three parts, a conserved N-terminal, a variable M region, and a conserved C-terminal with a bZIP domain. It belongs to the group A subfamily of bZIP transcription factors. TaAREB3 was constitutively expressed in stems, leaves, florets, anthers, pistils, seeds, and most highly, in roots. TaAREB3 gene expression was induced with abscisic acid (ABA) and low temperature stress, and its protein was localized in the nucleus when transiently expressed in tobacco epidermal cells and stably expressed in transgenic Arabidopsis. TaAREB3 protein has transcriptional activation activity, and can bind to the ABRE cis-element in vitro. Overexpression of TaAREB3 in Arabidopsis not only enhanced ABA sensitivity, but also strengthened drought and freezing tolerances. TaAREB3 also activated RD29A, RD29B, COR15A, and COR47 by binding to their promoter regions in transgenic Arabidopsis. These results demonstrated that TaAREB3 plays an important role in drought and freezing tolerances in Arabidopsis. PMID:26884722

  2. Statistical inference of selection and divergence of rice blast resistance gene Pi-ta

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The resistance gene Pi-ta has been effectively used to control rice blast disease worldwide. A few recent studies have described the possible evolution of Pi-ta in cultivated and weedy rice. However, evolutionary statistics used for the studies are too limited to precisely understand selection and d...

  3. Evaluation of the CoCrTaPt alloy for longitudinal magnetic recording

    NASA Astrophysics Data System (ADS)

    Cheng, Yuanda; Sedighi, Mojtaba; Lam, Irene; Gardner, Richard A.; Yang, ZhiJun; Scheinfein, Michael R.

    1994-05-01

    A quaternary alloy of CoCrTaPt with a composition of 80-10-4-6 (in at. %) was evaluated for its magnetic and recording properties. Samples of C/CoCrTaPt/Cr recording media were prepared by dc magnetron sputtering on circumferentially textured Al/NiP substrates. The effects on static magnetic properties and recording performance were studied for different substrate preheating times, Cr underlayer thicknesses, and Co-alloy layer thicknesses. It was found that both the coercivity Hc and remanent magnetization Mr increased with substrate preheating time. Hc also increased with Cr underlayer thickness, as expected. The Mrδ value depended linearly on the Co-alloy layer thickness. In addition, we found that the coercivity increased dramatically as the magnetic layer thickness decreased from ˜800 to ˜200 Å. For a sample with a 235-Å CoCrTaPt magnetic layer and ˜1000-Å Cr underlayer, the coercivity was found to be ≳2700 Oe. Parametric evaluation showed that CoCrTaPt samples have performance similar to samples of CoCrTa and, because of the Pt addition, the CoCrTaPt alloy offers significantly higher attainable coercivities than the CoCrTa alloy. Therefore, the CoCrTaPt alloy proves to be a good candidate for use in high density recording media which require coercivity of higher than 2000 Oe.

  4. Single crystal studies of binary compounds Ta/Ga - A system with experimental and crystallographic peculiarities

    NASA Astrophysics Data System (ADS)

    Koffi, Agbelenko; Ade, Martin; Hillebrecht, Harald

    2016-06-01

    We report on single crystal growth and characterisation of binary intermetallics TaxGay. Single crystals were obtained from mixtures of the elements which were handled under various conditions. Several new compounds were identified. The highest Ga-content is found for the new binary phases Ta6Ga31 and Ta8Ga41. Both compounds evolve as intergrown crystals. Ta8Ga41 belongs to the V8Ga41 type (R 3 bar , Z=3, a=14.311 Å, c=15.344 Å), Ta6Ga31 to the triclinic Mo6Ga31-type (P 1 bar , Z=2, a=9.697 Å, b=9.698 Å, c=14.879 Å, α=87.18°, β=80.83°, γ=85.18°). TaGa3 bases on the tetragonal TiAl3-type (I4/mmm, Z=2, a=3.769 Å, c=8.718 Å) but shows stacking faults leading to an increased Ta content Ta1+xGa3-x. This interpretation is supported by the structure model of an orthorhombic superstructure with an idealized composition Ta2Ga5 (Cmcm, Z=4, a=3.769, b=31.37, c=3.770 Å). Ta2-xGa5+x (x≈0.38) is a representative of the Mn2Hg5-type (P4/mbm, Z=2, a=9.3213(13), c=2.7572(6) Å). Ta4Ga5 represents a new compound with a novel crystal structure (P4/mbm, Z=16, a=11.793(2), c=16.967(3) Å). The complex structure contains polyhedra with coordination numbers between 11 and 14. Ta3Ga2 (P42/mnm, Z=2, a=6.8382(4), c=3.4963(2) Å) belongs to the U3Si2 type. For the composition Ta5Ga3 three different structure types were confirmed but with some differences. The tetragonal W5Si3 type (I4/mcm, Z=4, a=10.2199(7), c=5.1121(4) Å) is a stoichiometric binary compound, the hexagonal Mn5Si3-type (P63/mcm, Z=2, a=7.7023(4), c=5.3062(3) Å) contains a small amount of oxygen (Ta5Ga3O0.4) and in the tetragonal Cr5B3-type (I4/mcm, Z=4, a=6.5986(9), c=11.931(2)Å) one of the Ga-sites shows a significant underoccupation of 40% ("Ta2.2Ga"). Compositions were confirmed by EDX measurements.

  5. Evaluation of the potential for surface faulting at TA-63. Final report

    SciTech Connect

    Kolbe, T.; Sawyer, J.; Springer, J.; Olig, S.; Hemphill-Haley, M.; Wong, I.; Reneau, S.

    1995-01-01

    This report describes an investigation of the potential for surface faulting at the proposed sites for the Radioactive Liquid Waste Treatment Facility (RL)WF) and the Hazardous Waste Treatment Facility at TA-63 and TA-52 (hereafter TA-63), Los Alamos National Laboratory (LANL). This study was performed by Woodward-Clyde Federal Services (WCFS) at the request of the LANL. The projections of both the Guaje Mountain and Rendija Canyon faults are mapped in the vicinity of TA-63. Based on results obtained in the ongoing Seismic Hazard Evaluation Program of the LANL, displacement may have occurred on both the Guaje Mountain and Rendija Canyon faults in the past 11,000 years (Holocene time). Thus, in accordance with US Department of Energy (DOE) Orders and Standards for seismic hazards evaluations and the US Environmental Protection Agency (EPA) Resource Conservation and Recovery Act (RCRA) Regulations for seismic standard requirements, a geologic study of the proposed TA-63 site was conducted.

  6. Density functional study of the high-pressure behavior of Ta3N5

    NASA Astrophysics Data System (ADS)

    Zhang, Ji-Dong

    2016-08-01

    In this paper, the effects of high pressure on the structural, elastic and electronic properties of new synthesized U3Te5-type and U3Se5-type Ta3N5 are investigated by plane-wave pseudopotential density functional theory. The cell volumes, lattice constants and elastic constants of U3Te5-type and U3Se5-type Ta3N5 under pressure ranging from 0 to 100 GPa are obtained. The Vickers hardness and Debye temperature of U3Te5-and U3Se5-type Ta3N5 are calculated for the first time. DOS and PDOS are calculated to study the electronic properties and covalent bonds between N and Ta atoms, which are considered to be the origin of the high hardness of these two types Ta3N5.

  7. Synthesis, crystal structure, and photocatalytical properties of Ba3Ta5O14N

    NASA Astrophysics Data System (ADS)

    Anke, B.; Bredow, T.; Soldat, J.; Wark, M.; Lerch, M.

    2016-01-01

    Light yellow Ba3TaV5O14N was successfully synthesized as phase-pure material crystallizing isostructurally to well-known mixed-valence Ba3TaV4TaIVO15. The electronic structure of Ba3Ta5O14N was studied theoretically with a hybrid Hartree-Fock-DFT method. The most stable structure was obtained when nitrogen atoms were placed at 4 h sites having fourfold coordination. By incorporating nitrogen, the band gap decreases from ∼3.8 eV commonly known for barium tantalum(V) oxides to 2.8 eV for the oxide nitride, giving rise to an absorption band well in the visible-light region. Ba3Ta5O14N was also tested for photocatalytic hydrogen formation.

  8. Superconducting proximity effect in inverted InAs/GaSb quantum well structures with Ta electrodes

    NASA Astrophysics Data System (ADS)

    Yu, Wenlong; Jiang, Yuxuan; Huan, Chao; Chen, Xunchi; Jiang, Zhigang; Hawkins, Samuel D.; Klem, John F.; Pan, Wei

    2014-11-01

    We present our recent electronic transport results in top-gated InAs/GaSb quantum well hybrid structures with superconducting Ta electrodes. We show that the transport across the InAs-Ta junction depends largely on the interfacial transparency, exhibiting distinct zero-bias behavior. For a relatively resistive interface, a broad conductance peak is observed at zero bias. When a transparent InAs-Ta interface is achieved, a zero-bias conductance dip appears with two coherent-peak-like features forming at bias voltages corresponding to the superconducting gap of Ta. The conductance spectra of the transparent InAs-Ta junction at different gate voltages can be fit well using the standard Blonder-Tinkham-Klapwijk theory.

  9. "Engineered dual NbTa barriers for higher Jc Nb3Sn superconductors"

    SciTech Connect

    Robert E. Barber; Karl T. Hartwig

    2012-07-07

    The tantalum (Ta) diffusion barrier in advanced Nb3Sn superconductors often develops a failure mode during wire drawing where the Nb and Ta layers deform non-uniformly leading to a rough interface with adjacent copper. The non-uniform deformation of these layers can lead to premature wire breakage and breaches in the barrier, and contamination of the copper stabilizer by tin (Sn). The objective of the proposed work was to demonstrate that a dual NbTa layer made from severely deformed Nb and Ta exhibits improved co-deformation behavior with pure Cu in advanced Nb3Sn superconductors. This phase I project demonstrated improved microstructural uniformity and superior mechanical property characteristics of equal channel angular extrusion (ECAE) processed and rolled Nb and Ta sheets. The results of this work point to a method for fabrication of higher field and lower cost superconducting magnets for high energy physics applications.

  10. Virus-Induced Gene Silencing Identifies an Important Role of the TaRSR1 Transcription Factor in Starch Synthesis in Bread Wheat.

    PubMed

    Liu, Guoyu; Wu, Yufang; Xu, Mengjun; Gao, Tian; Wang, Pengfei; Wang, Lina; Guo, Tiancai; Kang, Guozhang

    2016-01-01

    The function of a wheat starch regulator 1 (TaRSR1) in regulating the synthesis of grain storage starch was determined using the barley stripe mosaic virus-virus induced gene-silencing (BSMV-VIGS) method in field experiments. Chlorotic stripes appeared on the wheat spikes infected with barley stripe mosaic virus-virus induced gene-silencing- wheat starch regulator 1 (BSMV-VIGS-TaRSR1) at 15 days after anthesis, at which time the transcription levels of the TaRSR1 gene significantly decreased. Quantitative real-time PCR was also used to measure the transcription levels of 26 starch synthesis-related enzyme genes in the grains of BSMV-VIGS-TaRSR1-silenced wheat plants at 20, 27, and 31 days after anthesis. The results showed that the transcription levels of some starch synthesis-related enzyme genes were markedly induced at different sampling time points: TaSSI, TaSSIV, TaBEIII, TaISA1, TaISA3, TaPHOL, and TaDPE1 genes were induced at each of the three sampling time points and TaAGPS1-b, TaAGPL1, TaAGPL2, TaSSIIb, TaSSIIc, TaSSIIIb, TaBEI, TaBEIIa, TaBEIIb, TaISA2, TaPHOH, and TaDPE2 genes were induced at one sampling time point. Moreover, both the grain starch contents, one thousand kernel weights, grain length and width of BSMV-VIGS-TaRSR1-infected wheat plants significantly increased. These results suggest that TaRSR1 acts as a negative regulator and plays an important role in starch synthesis in wheat grains by temporally regulating the expression of specific starch synthesis-related enzyme genes. PMID:27669224

  11. Virus-Induced Gene Silencing Identifies an Important Role of the TaRSR1 Transcription Factor in Starch Synthesis in Bread Wheat

    PubMed Central

    Liu, Guoyu; Wu, Yufang; Xu, Mengjun; Gao, Tian; Wang, Pengfei; Wang, Lina; Guo, Tiancai; Kang, Guozhang

    2016-01-01

    The function of a wheat starch regulator 1 (TaRSR1) in regulating the synthesis of grain storage starch was determined using the barley stripe mosaic virus—virus induced gene-silencing (BSMV-VIGS) method in field experiments. Chlorotic stripes appeared on the wheat spikes infected with barley stripe mosaic virus-virus induced gene-silencing- wheat starch regulator 1 (BSMV-VIGS-TaRSR1) at 15 days after anthesis, at which time the transcription levels of the TaRSR1 gene significantly decreased. Quantitative real-time PCR was also used to measure the transcription levels of 26 starch synthesis-related enzyme genes in the grains of BSMV-VIGS-TaRSR1-silenced wheat plants at 20, 27, and 31 days after anthesis. The results showed that the transcription levels of some starch synthesis-related enzyme genes were markedly induced at different sampling time points: TaSSI, TaSSIV, TaBEIII, TaISA1, TaISA3, TaPHOL, and TaDPE1 genes were induced at each of the three sampling time points and TaAGPS1-b, TaAGPL1, TaAGPL2, TaSSIIb, TaSSIIc, TaSSIIIb, TaBEI, TaBEIIa, TaBEIIb, TaISA2, TaPHOH, and TaDPE2 genes were induced at one sampling time point. Moreover, both the grain starch contents, one thousand kernel weights, grain length and width of BSMV-VIGS-TaRSR1-infected wheat plants significantly increased. These results suggest that TaRSR1 acts as a negative regulator and plays an important role in starch synthesis in wheat grains by temporally regulating the expression of specific starch synthesis-related enzyme genes. PMID:27669224

  12. The Antibacterial Activity of Ta-doped ZnO Nanoparticles

    NASA Astrophysics Data System (ADS)

    Guo, Bing-Lei; Han, Ping; Guo, Li-Chuan; Cao, Yan-Qiang; Li, Ai-Dong; Kong, Ji-Zhou; Zhai, Hai-Fa; Wu, Di

    2015-08-01

    A novel photocatalyst of Ta-doped ZnO nanoparticles was prepared by a modified Pechini-type method. The antimicrobial study of Ta-doped ZnO nanoparticles on several bacteria of Gram-positive Bacillus subtilis ( B. subtilis) and Staphylococcus aureus ( S. aureus) and Gram-negative Escherichia coli ( E. coli) and Pseudomonas aeruginosa ( P. aeruginosa) were performed using a standard microbial method. The Ta-doping concentration effect on the minimum inhibitory concentration (MIC) of various bacteria under dark ambient has been evaluated. The photocatalytical inactivation of Ta-doped ZnO nanoparticles under visible light irradiation was examined. The MIC results indicate that the incorporation of Ta5+ ions into ZnO significantly improve the bacteriostasis effect of ZnO nanoparticles on E. coli, S. aureus, and B. subtilis in the absence of light. Compared to MIC results without light irradiation, Ta-doped ZnO and pure ZnO nanoparticles show much stronger bactericidal efficacy on P. aeruginosa, E. coli, and S. aureus under visible light illumination. The possible antimicrobial mechanisms in Ta-doped ZnO systems under visible light and dark conditions were also proposed. Ta-doped ZnO nanoparticles exhibit more effective bactericidal efficacy than pure ZnO in dark ambient, which can be attributed to the synergistic effect of enhanced surface bioactivity and increased electrostatic force due to the incorporation of Ta5+ ions into ZnO. Based on the antibacterial tests, 5 % Ta-doped ZnO is a more effective antimicrobial agent than pure ZnO.

  13. 17 CFR 249b.101 - Form TA-W, notice of withdrawal from registration as transfer agent.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...))) Editorial Note: For Federal Register citations affecting Form TA-W, see the List of CFR Sections Affected... 17 Commodity and Securities Exchanges 3 2010-04-01 2010-04-01 false Form TA-W, notice of... TA-W, notice of withdrawal from registration as transfer agent. This form shall be used...

  14. Evolutionary dynamics and structure of the rice blast resistance locus Pi-ta in wild, cultivated, and US weedy rice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Pi-ta gene in rice has been used to control rice blast pathogen, Magnaporthe oryza, in rice growing areas worldwide for decades. To understand the evolutionary process and natural selection of Pi-ta during rice domestication, we first examined sequences of the genomic region of Pi-ta in geograph...

  15. Overexpression of wheat gene TaMOR improves root system architecture and grain yield in Oryza sativa.

    PubMed

    Li, Bo; Liu, Dan; Li, Qiaoru; Mao, Xinguo; Li, Ang; Wang, Jingyi; Chang, Xiaoping; Jing, Ruilian

    2016-07-01

    Improved root architecture is an effective strategy to increase crop yield. We demonstrate that overexpression of transcription factor gene MORE ROOT (TaMOR) from wheat (Triticum aestivum L.) results in more roots and higher grain yield in rice (Oryza sativa). TaMOR, encoding a plant-specific transcription factor belonging to the ASYMMETRIC LEAVES2/LATERAL ORGAN BOUNDARIES (AS2/LOB) protein family, is highly conserved in wheat and its wild relatives. In this study, tissue expression patterns indicated that TaMOR mainly localizes to root initiation sites. The consistent gene expression pattern suggests that TaMOR is involved in root initiation. Exogenous auxin treatment induced TaMOR expression without de novo protein biosynthesis. Both in vivo and in vitro experiments demonstrated that TaMOR interacts with TaMOR-related protein TaMRRP, which contains a four-tandem-pentatricopeptide repeat motif. Overexpression of TaMOR led to more lateral roots in Arabidopsis thaliana, and TaMOR-overexpressing rice plants had more crown roots, a longer main panicle, a higher number of primary branches on the main panicle, a higher grain number per plant, and higher yield per plant than the plants of wild type. In general, TaMOR-D-overexpressing lines had larger root systems in Arabidopsis and rice, and produce a higher grain yield per plant. TaMOR therefore offers an opportunity to improve root architecture and increase yield in crop plants. PMID:27229732

  16. 78 FR 41954 - TA-W-82,634, Prudential Global Business Technology Solutions Central Security Services Dresher...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-12

    ... Employment and Training Administration TA-W-82,634, Prudential Global Business Technology Solutions Central Security Services Dresher, Pennsylvania; TA-W-82,634A, Prudential Global Business Technology Solutions Central Security Services Iselin, New Jersey; TA-W-82,634B, Prudential Global Business...

  17. 75 FR 66794 - Notice of Affirmative Determination Regarding Application for Reconsideration: TA-W-71,572...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-29

    ... Ferry, OH; TA-W-71,572A, Severstal Wheeling, Inc., a Subsidiary of Severstal North America, Inc., Yorkville, OH; TA-W-71,572B, Severstal Wheeling, Inc., a Subsidiary of Severstal North America, Inc., Mingo Junction, OH; TA-W- 71,572C, Severstal Wheeling, Inc., a Subsidiary of Severstal North America,...

  18. Theoretical study of water adsorption and dissociation on Ta3N5(100) surfaces.

    PubMed

    Wang, Jiajia; Luo, Wenjun; Feng, Jianyong; Zhang, Li; Li, Zhaosheng; Zou, Zhigang

    2013-10-14

    Water adsorption and dissociation on the perfect, oxygen containing and nitrogen vacancy containing Ta3N5(100) surfaces are systematically studied by density functional theory calculations. The results show that the perfect Ta3N5(100) surface is very active for water dissociation because of the dangling bonds formed on the perfect Ta3N5(100) surface. The presence of oxygen on the surface is able to stabilize the Ta3N5(100) surface but not to facilitate water dissociation, which may be ascribed to the saturation of surface dangling bonds by oxygen. The presence of a nitrogen vacancy on the surface is able to facilitate water dissociation, but Ta3N5(100) surfaces with nitrogen vacancies are not stable. We found that keeping the impurity oxygen as less as possible is one effective approach to enhance the water splitting ability of Ta3N5. We propose that doping with foreign elements is one potential method to obtain a clean Ta3N5(100) surface, since the oxygen concentration may be adjusted by competition between oxygen and foreign elements. PMID:23965737

  19. Study of Brāhmī Ghṛta and piracetam in amnesia

    PubMed Central

    Yadav, Kapil Deo; Reddy, K. R. C.; Kumar, Vikas

    2012-01-01

    Objective: To compare the effect of Brāhmī Ghṛta with piracetam (a reference standard chemical) in amnesia. Materials and Methods: Brāhmī Ghṛta contained Brāhmī (Bacopa monneri), Vacā (Acorus calamus), Kuṣṭha (Sassurea lappa), Śaṅkhapuṣpī (Convolvulos pluricalis), and Purāṇa Ghṛta, prepared as per snehapāka process. Antiamnesic activity of Brāhmī Ghṛta (400 and 800 mg/kg, p.o.) was evaluated in scopolamine (1 mg/kg, s.c.) induced amnesia in Charles Foster rats using elevated plus maze, passive avoidance, and active avoidance tests. Piracetam (500 mg/kg, p.o.) was used as standard drug. This effect was compared with standard chemical used in experimental study. Results: Brāhmī Ghṛta - (in both doses) and piracetam-treated rats significantly reversed the effect of scopolamine in modified elevated plus maze, passive avoidance, and active avoidance tests. But there were no significant differences observed in antiamnesic activity of Brāhmī Ghṛta and standard drug. Conclusion: Brāhmī Ghṛta and piracetam produced significant beneficial effect on scopolamine-induced amnesic effect, but no significant difference was observed in between them. PMID:23929987

  20. Nb-Ta mobility and fractionation during exhumation of UHP eclogite from southwestern Tianshan, China

    NASA Astrophysics Data System (ADS)

    Zhang, Lijuan; Zhang, Lifei; Lü, Zeng; Bader, Thomas; Chen, Zhenyu

    2016-05-01

    In order to study the behavior of high field strength elements (HFSE) during retrograde overprint of ultrahigh-pressure (UHP) eclogites, analysis of Nb and Ta concentrations was carried out on bulk rock, rutile (in both veins and host rocks) and titanite in the host eclogite. The studied samples were collected from the UHP metamorphic belt of southwestern Tianshan, China. Petrographic observation and phase equilibria modeling show that the host eclogites have experienced UHP metamorphism and the rutile-bearing veins are thought to be originated from an internal fluid source, probably by lawsonite dehydration during exhumation. The presence of vein rutile indicates HFSE could be mobilized from host eclogites to veins, which is probably facilitated by complexation with dissolved Na-Al silicates and fluorine-rich fluids. Changes in fluid composition (e.g., F-1, X(CO2)) may trigger the precipitation of rutile. Rutile/fluid partitioning may be the key to fractionating Nb and Ta, with preference for Ta in the fluid, resulting in Nb/Ta ratio of rutile in the veins lower than that in the host eclogite. Besides, the transformation of rutile into titanite also might be an effective mechanism for fractionating Nb from Ta, resulting in the intra-grain Nb-Ta zonations in vein rutile. The Nb-Ta mobility and fractionation can happen during exhumation of the UHP eclogite, which should be very important for understanding the behavior of HFSE in subduction zone metamorphism.

  1. Synthesis of Ti-Ta alloys with dual structure by incomplete diffusion between elemental powders.

    PubMed

    Liu, Yong; Li, Kaiyang; Wu, Hong; Song, Min; Wang, Wen; Li, Nianfeng; Tang, Huiping

    2015-11-01

    In this work, powder metallurgical (PM) Ti-Ta alloys were sintered using blended elemental powders. A dual structure, consisting of Ti-rich and Ta-rich zones, was formed due to the insufficient diffusion between Ti and Ta powders. The microstructure, mechanical properties and in vitro biological properties of the alloys were studied. Results indicated that the alloys have inhomogenous microstructures and compositions, but the grain structures were continuous from the Ti-rich zone to the Ta-rich zone. The Ta-rich zone exhibited a much finer grain size than the Ti-rich zone. The alloys had a high relative density in the range of 95-98%, with the porosity increasing with the content of Ta due to the increased difficulty in sintering and the formation of Kirkendall pores. The alloys had a good combination of low elastic modulus and high tensile strength. The strength of alloys was almost doubled compared to that of the ingot metallurgy alloys with the same compositions. The low elastic modulus was due to the residual pores and the alloying effect of Ta, while the high tensile strength resulted from the strengthening effects of solid solution, fine grain size and α phase. The alloys had a high biocompatibility due to the addition of Ta, and were suitable for the attachment of cells due to the surface porosity. It was also indicated that PM Ti-(20-30)Ta alloys are promising for biomedical applications after the evaluations of both the mechanical and the biological properties. PMID:26275506

  2. Anomalous anti-damping in sputtered β-Ta/Py bilayer system

    PubMed Central

    Behera, Nilamani; Chaudhary, Sujeet; Pandya, Dinesh K.

    2016-01-01

    Anomalous decrease in effective damping parameter αeff in sputtered Ni81Fe19 (Py) thin films in contact with a very thin β-Ta layer without necessitating the flow of DC-current is observed. This reduction in αeff, which is also referred to as anti-damping effect, is found to be critically dependent on the thickness of β-Ta layer; αeff being highest, i.e., 0.0093 ± 0.0003 for bare Ni81Fe19(18 nm)/SiO2/Si compared to the smallest value of 0.0077 ± 0.0001 for β-Ta(6 nm)/Py(18 nm)/SiO2/Si. This anomalous anti-damping effect is understood in terms of interfacial Rashba effect associated with the formation of a thin protective Ta2O5 barrier layer and also the spin pumping induced non-equilibrium diffusive spin-accumulation effect in β-Ta layer near the Ta/Py interface which induces additional spin orbit torque (SOT) on the moments in Py leading to reduction in . The fitting of (tTa) revealed an anomalous negative interfacial spin mixing conductance, and spin diffusion length,. The increase in αeff observed above tTa = 6 nm is attributed to the weakening of SOT at higher tTa. The study highlights the potential of employing β-Ta based nanostructures in developing low power spintronic devices having tunable as well as low value of α. PMID:26782952

  3. TaADF3, an Actin-Depolymerizing Factor, Negatively Modulates Wheat Resistance Against Puccinia striiformis.

    PubMed

    Tang, Chunlei; Deng, Lin; Chang, Dan; Chen, Shuntao; Wang, Xiaojie; Kang, Zhensheng

    2015-01-01

    The actin cytoskeleton has been implicated in plant defense against pathogenic fungi, oomycetes, and bacteria. Actin depolymerizing factors (ADFs) are stimulus responsive actin cytoskeleton modulators. However, there is limited evidence linking ADFs with plant defense against pathogens. In this study, we have isolated and functionally characterized a stress-responsive ADF gene (TaADF3) from wheat, which was detectable in all examined wheat tissues. TaADF3 is a three-copy gene located on chromosomes 5AL, 5BL, and 5DL. A particle bombardment assay in onion epidermal cells revealed the cytoplasmic and nuclear localization of TaADF3. The expression of TaADF3 was inducible by abscisic acid (ABA), as well as various abiotic stresses (drought and cold) and virulent Puccinia striiformis f. sp. tritici (Pst) but was down regulated in response to avirulent Pst. Virus-induced silencing of TaADF3 copies enhanced wheat resistance to avirulent Pst, with decreased reactive oxygen species (ROS) accumulation and hypersensitive response (HR). Upon treatment with virulent Pst, TaADF3-knockdown plants exhibited reduced susceptibility, which was accompanied by increased ROS production and HR. Interestingly, the silencing of TaADF3 resulted in hindered pathogen penetration and haustoria formation for both avirulent and virulent Pst. Moreover, the array and distribution of actin filaments was transformed in TaADF3-knockdown epidermal cells, which possibly facilitated attenuating the fungus penetration. Thus, our findings suggest that TaADF3 positively regulates wheat tolerance to abiotic stresses and negatively regulates wheat resistance to Pst in an ROS-dependent manner, possibly underlying the mechanism of impeding fungal penetration dependent on the actin architecture dynamics. PMID:26834758

  4. TaADF3, an Actin-Depolymerizing Factor, Negatively Modulates Wheat Resistance Against Puccinia striiformis

    PubMed Central

    Tang, Chunlei; Deng, Lin; Chang, Dan; Chen, Shuntao; Wang, Xiaojie; Kang, Zhensheng

    2016-01-01

    The actin cytoskeleton has been implicated in plant defense against pathogenic fungi, oomycetes, and bacteria. Actin depolymerizing factors (ADFs) are stimulus responsive actin cytoskeleton modulators. However, there is limited evidence linking ADFs with plant defense against pathogens. In this study, we have isolated and functionally characterized a stress-responsive ADF gene (TaADF3) from wheat, which was detectable in all examined wheat tissues. TaADF3 is a three-copy gene located on chromosomes 5AL, 5BL, and 5DL. A particle bombardment assay in onion epidermal cells revealed the cytoplasmic and nuclear localization of TaADF3. The expression of TaADF3 was inducible by abscisic acid (ABA), as well as various abiotic stresses (drought and cold) and virulent Puccinia striiformis f. sp. tritici (Pst) but was down regulated in response to avirulent Pst. Virus-induced silencing of TaADF3 copies enhanced wheat resistance to avirulent Pst, with decreased reactive oxygen species (ROS) accumulation and hypersensitive response (HR). Upon treatment with virulent Pst, TaADF3-knockdown plants exhibited reduced susceptibility, which was accompanied by increased ROS production and HR. Interestingly, the silencing of TaADF3 resulted in hindered pathogen penetration and haustoria formation for both avirulent and virulent Pst. Moreover, the array and distribution of actin filaments was transformed in TaADF3-knockdown epidermal cells, which possibly facilitated attenuating the fungus penetration. Thus, our findings suggest that TaADF3 positively regulates wheat tolerance to abiotic stresses and negatively regulates wheat resistance to Pst in an ROS-dependent manner, possibly underlying the mechanism of impeding fungal penetration dependent on the actin architecture dynamics. PMID:26834758

  5. Synthesis of Ti-Ta alloys with dual structure by incomplete diffusion between elemental powders.

    PubMed

    Liu, Yong; Li, Kaiyang; Wu, Hong; Song, Min; Wang, Wen; Li, Nianfeng; Tang, Huiping

    2015-11-01

    In this work, powder metallurgical (PM) Ti-Ta alloys were sintered using blended elemental powders. A dual structure, consisting of Ti-rich and Ta-rich zones, was formed due to the insufficient diffusion between Ti and Ta powders. The microstructure, mechanical properties and in vitro biological properties of the alloys were studied. Results indicated that the alloys have inhomogenous microstructures and compositions, but the grain structures were continuous from the Ti-rich zone to the Ta-rich zone. The Ta-rich zone exhibited a much finer grain size than the Ti-rich zone. The alloys had a high relative density in the range of 95-98%, with the porosity increasing with the content of Ta due to the increased difficulty in sintering and the formation of Kirkendall pores. The alloys had a good combination of low elastic modulus and high tensile strength. The strength of alloys was almost doubled compared to that of the ingot metallurgy alloys with the same compositions. The low elastic modulus was due to the residual pores and the alloying effect of Ta, while the high tensile strength resulted from the strengthening effects of solid solution, fine grain size and α phase. The alloys had a high biocompatibility due to the addition of Ta, and were suitable for the attachment of cells due to the surface porosity. It was also indicated that PM Ti-(20-30)Ta alloys are promising for biomedical applications after the evaluations of both the mechanical and the biological properties.

  6. SEMICONDUCTOR TECHNOLOGY: TaN wet etch for application in dual-metal-gate integration technology

    NASA Astrophysics Data System (ADS)

    Yongliang, Li; Qiuxia, Xu

    2009-12-01

    Wet-etch etchants and the TaN film method for dual-metal-gate integration are investigated. Both HF/HN O3/H2O and NH4OH/H2O2 solutions can etch TaN effectively, but poor selectivity to the gate dielectric for the HF/HNO3/H2O solution due to HF being included in HF/HNO3/H2O, and the fact that TaN is difficult to etch in the NH4OH/H2O2 solution at the first stage due to the thin TaOxNy layer on the TaN surface, mean that they are difficult to individually apply to dual-metal-gate integration. A two-step wet etching strategy using the HF/HNO3/H2O solution first and the NH4OH/H2O2 solution later can fully remove thin TaN film with a photo-resist mask and has high selectivity to the HfSiON dielectric film underneath. High-k dielectric film surfaces are smooth after wet etching of the TaN metal gate and MOSCAPs show well-behaved C-V and Jg-Vg characteristics, which all prove that the wet etching of TaN has little impact on electrical performance and can be applied to dual-metal-gate integration technology for removing the first TaN metal gate in the PMOS region.

  7. Chemical Concentrations in Field Mice from Open-Detonation Firing Sites TA-36 Minie and TA-39 Point 6 at Los Alamos National Laboratory

    SciTech Connect

    Fresquez, Philip R.

    2011-01-01

    Field mice (mostly Peromyscus spp.) were collected at two open-detonation (high explosive) firing sites - Minie at Technical Area (TA) 36 and Point 6 at TA-39 - at Los Alamos National Laboratory in August of 2010 and in February of 2011 for chemical analysis. Samples of whole body field mice from both sites were analyzed for target analyte list elements (mostly metals), dioxin/furans, polychlorinated biphenyl congeners, high explosives, and perchlorate. In addition, uranium isotopes were analyzed in a composite sample collected from TA-36 Minie. In general, all constituents, with the exception of lead at TA-39 Point 6, in whole body field mice samples collected from these two open-detonation firing sites were either not detected or they were detected below regional statistical reference levels (99% confidence level), biota dose screening levels, and/or soil ecological chemical screening levels. The amount of lead in field mice tissue collected from TA-39 Point 6 was higher than regional background, and some lead levels in the soil were higher than the ecological screening level for the field mouse; however, these levels are not expected to affect the viability of the populations over the site as a whole.

  8. The effect of Ta2O5 on the interaction between silicon and its contact metallization

    NASA Technical Reports Server (NTRS)

    Weizer, V. G.

    1982-01-01

    Evidence is presented showing that the presence of the commonly used antireflection coating material, Ta2O5, on the free surface of contact metallization can either suppress or enhance, depending on the system, the interaction that takes place at elevated temperatures between the metallization and the underlying silicon. The Ta2O5 layer is shown to suppress both the generation and the annihilation of vacancies at the metal free surface which are necessary to support metal-silicon interactions. It is also shown that the mechanical condition of the free metal surface has a significant effect on the passivating ability of the Ta2O5 layer.

  9. Application of LiTaO3 pyroelectric crystal for pulsed neutron detection

    NASA Astrophysics Data System (ADS)

    Liang, W. F.; Lu, Y.; Wu, J.; Gao, H.; Li, M.

    2016-08-01

    The feasibility of a LiTaO3 pyroelectric crystal for pulsed neutron detection has been studied. The detector consists of a slice of electroded Z-cut LiTaO3 pyroelectric crystal, and no additional neutron converter is required owing to the Li contained in the crystal. The slight temperature increase caused by neutron radiation will lead to the release of bound charges and will give rise to a pyroelectric signal. The response of it has been studied both theoretically and experimentally. Our preliminary experiment on the CFBR-II reactor suggests that the LiTaO3 pyroelectric detector is promising for high intensity neutron - pulse measurement.

  10. New Developments of the Therapeutic Alliance (TA): Good News for Psychodynamic Psychiatry.

    PubMed

    Auchincloss, Elizabeth L

    2016-03-01

    Clinicians have long known that successful psychotherapy, including successful psychodynamic psychotherapy, depends upon the interaction between therapist and patient. In other words, it is important to have a strong therapeutic alliance. This article presents the history of the concept of the therapeutic alliance (TA). It also explores three areas of research that have bearing on the TA. The importance of the TA and the extensive research work that pertains to it hold promise for psychodynamic psychiatry, both in terms of understanding, and in the treatment of mental suffering. PMID:26938802

  11. Oxide stoichiometry-controlled TaOx-based resistive switching behaviors

    NASA Astrophysics Data System (ADS)

    Baek, Gwang Ho; Lee, Ah Rahm; Kim, Tae Yoon; Im, Hyun Sik; Hong, Jin Pyo

    2016-10-01

    We examine the influence of variable oxygen concentration in TaOx active layers on the forming process and bipolar resistive switching (BRS) features of TaOx-based resistive switching cells. TaOx active layers prepared using various rf sputtering powers were systematically analyzed to identify the relation between initial compositions and BRS behavior. Proper control of oxygen vacancy concentration was clearly identified as a basic factor in ensuring typical BRS features without affecting the structural properties. We describe the possible origins of both conduction and switching based on the variation of oxygen concentrations initially provided by the growth conditions.

  12. Connection between the glass transition temperature Tg and the Arrhenius temperature TA in supercooled liquids

    NASA Astrophysics Data System (ADS)

    Novikov, V. N.

    2016-08-01

    At high temperatures the structural relaxation time in liquids has Arrhenius temperature dependence. At lowering temperature, temperature dependence changes to a super Arrhenius at some temperature TA. This temperature is an important point for the structural relaxation dynamics in supercooled liquids because it reflects the transition to collective relaxation. Here we derive a relation between TA, the glass transition temperature Tg and fragility. We show that the ratio Tg/TA increases with increasing fragility of a liquid. The derived relation is in agreement with the experimental data in a series of molecular, hydrogen bonding and two inorganic glass-formers.

  13. New Developments of the Therapeutic Alliance (TA): Good News for Psychodynamic Psychiatry.

    PubMed

    Auchincloss, Elizabeth L

    2016-03-01

    Clinicians have long known that successful psychotherapy, including successful psychodynamic psychotherapy, depends upon the interaction between therapist and patient. In other words, it is important to have a strong therapeutic alliance. This article presents the history of the concept of the therapeutic alliance (TA). It also explores three areas of research that have bearing on the TA. The importance of the TA and the extensive research work that pertains to it hold promise for psychodynamic psychiatry, both in terms of understanding, and in the treatment of mental suffering.

  14. Structural studies of the metal-rich region in the ternary Ta-Nb-S system

    SciTech Connect

    Yao, Xiaoqiang.

    1991-10-07

    Six new solid solution type compounds have been prepared using high temperature techniques and characterized by means of single crystal x-ray techniques during a study of the metal-rich region of the ternary Ta-Nb-S system. The structures of Nb{sub x}Ta{sub 11-x}S{sub 4} are reminiscent of niobium-rich sulfides, rather than of tantalum-rich sulfides. The coordinations of sulfur are capped trigonal prismatic while the metal coordinations are capped distorted cubic prismatic for Nb{sub x}Ta{sub 11-x}S{sub 4}, and capped distorted cubic prismatic and pentagonal prismatic for Nb{sub 12-x}Ta{sub x}S{sub 4}. The structures of Nb{sub x}Ta{sub 5-x}S{sub 2} contain homoatomic layers sequenced S-M3-M2-M1-M2-M3-S (M is mixed Nb, Ta) generating six-layer sheets, respectively. Weak S-S interactions at 3.26 and 3.19{Angstrom} between sheets contrast with the M-M binding within and between the sheets in these two novel layered compounds. The former are presumably responsible for the observed graphitic slippage of the samples. Nb{sub 21-x}Ta{sub x}S{sub 8} and Nb{sub x}Ta{sub 2-x}S are isostructural with Nb{sub 21}S{sub 8} and Ta{sub 2}S, respectively. Extended Hueckel band calculations were carried out for two layered compounds, Nb{sub x}Ta{sub 5-x}S{sub 2} (x {approx} 1.72) and Nb{sub x}ta{sub 2-x}S (x {approx} 0.95). Based upon band calculations metallic properties can be expected for these two layered compounds. The relative preference of the metal sites for the two metal elements (Ta, Nb) in two layered compounds is explained by the results of the band calculations. 17 figs., 31 tabs., 80 refs.

  15. Equation of state measurements in Ta2O5 aerogel

    NASA Astrophysics Data System (ADS)

    Miller, Joshua; Boehly, Tom; Meyerhofer, David; Eggert, Jon

    2007-06-01

    The examination of the equation of state of Ta2O5 aerogel using laser driven shock compression has been performed at OMEGA. The foams, with densities in the range of 0.1 to 0.25 g/cc, were loaded by shocks with pressures in the range of 50 to 300 Gpa. Hugoniot parameters inferred from mechanical measurements of the shock evolution and temperatures inferred from the shock front self-emission were resolved on the sub-nanosecond time scale during this study. Comparisons between these experimental results and the existing qEOS model show that the aerogel is much more compressible than qEOS predicts at pressures below 100 GPa. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460, the University of Rochester, and the New York State Energy Research and Development Authority. The support of DOE does not constitute an endorsement by DOE of the views expressed in this article.

  16. Trace metals in the Góta river estuary

    NASA Astrophysics Data System (ADS)

    Danielsson, Lars-Göran; Magnusson, Bertil; Westerlund, Stig; Zhang, Kerong

    1983-07-01

    The concentrations of the trace metals Cd, Cu, Fe, Ni, Pb and Zn in the Göta River estuary have been investigated. The following metal fractions have been determined: acid-leachable, dissolved, labile and particulate. The estuary represents a salt wedge type estuary and is situated in a densely populated region of Sweden. The metal concentrations found for the dissolved fraction is in the range of what can be considered as background levels for freshwater. It is difficult to evaluate any estuarine processes other than conservative mixing for Cd, Cu, Ni and Zn. The dissolved levels in the freshwater end member are Cd, 9-25 ngl -1; Cu, 1·1-1·4 μgl -1; Fe, 20-75 μg l -1: Ni, 0·7-0·9 μg l -1: Pb 0·09-0·2 μg l -1; and Zn, 6-7 μg l -1: The results from the acid-leachable fraction show that at high suspended load the particles sediment in the river mouth. The trace metal levels in this fraction are subject to large variations.

  17. Influence of shockwave obliquity on deformation twin formation in Ta

    SciTech Connect

    Gray, George T., III; Livescu, V; Cerreta, E K; Mason, T A; Maudlin, P J; Bingert, J F

    2009-02-18

    Energetic loading subjects a material to a 'Taylor wave' (triangular wave) loading profile that experiences an evolving balance of hydrostatic (spherical) and deviatoric stresses. While much has been learned over the past five decades concerning the propensity of deformation twinning in samples shockloaded using 'square-topped' profiles as a function of peak stress, achieved most commonly via flyer plate loading, less is known concerning twinning propensity during non-I-dimensional sweeping detonation wave loading. Systematic small-scale energetically-driven shock loading experiments were conducted on Ta samples shock loaded with PEFN that was edge detonated. Deformation twinning was quantified in post-mortem samples as a function of detonation geometry and radial position. In the edge detonated loading geometry examined in this paper, the average volume fraction of deformation twins was observed to drastically increase with increasing shock obliquity. The results of this study are discussed in light of the formation mechanisms of deformation twins, previous literature studies of twinning in shocked materials, and modeling of the effects of shock obliquity on the evolution of the stress tensor during shock loading.

  18. Seismic Vulnerability Assessment Rest House Building TA-16-41

    SciTech Connect

    Cuesta, Isabel; Salmon, Michael W.

    2003-10-01

    The purpose of this report is to present the results of the evaluation completed on the Rest House Facility (TA-16-4111) in support of hazard analysis for a Documented Safety Assessment (DSA). The Rest House facility has been evaluated to verify the structural response to seismic, wind, and snow loads in support of the DynEx DSA. The structural analyses consider the structure and the following systems and/or components inside the facility as requested by facility management: cranes, lighting protection system, and fire protection system. The facility has been assigned to Natural Phenomena Hazards (NPH) Performance Category (PC) –3. The facility structure was evaluated to PC-3 criteria because it serves to confine hazardous material, and in the event of an accident, the facility cannot fail or collapse. Seismicinduced failure of the cranes, lighting, and fire-protection systems according to DOE-STD-1021-93 (Ref. 1) “may result in adverse release consequences greater than safety-class Structures, Systems, and Components (SSC) Evaluation Guideline limits but much less than those associated with PC-4 SSC.” Therefore, these items will be evaluated to PC-3 criteria as well. This report presents the results of those analyses and suggests recommendations to improve the seismic capacity of the systems and components cited above.

  19. Biocompatibility of new Ti-Nb-Ta base alloys.

    PubMed

    Hussein, Abdelrahman H; Gepreel, Mohamed A-H; Gouda, Mohamed K; Hefnawy, Ahmad M; Kandil, Sherif H

    2016-04-01

    β-type titanium alloys are promising materials in the field of medical implants. The effect of β-phase stability on the mechanical properties, corrosion resistance and cytotoxicity of a newly designed β-type (Ti77Nb17Ta6) biocompatible alloys are studied. The β-phase stability was controlled by the addition of small quantities of Fe and O. X-ray diffraction and microstructural analysis showed that the addition of O and Fe stabilized the β-phase in the treated solution condition. The strength and hardness have increased with the increase in β-phase stability while ductility and Young's modulus have decreased. The potentio-dynamic polarization tests showed that the corrosion resistance of the new alloys is better than Ti-6Al-4V alloy by at least ten times. Neutral red uptake assay cytotoxicity test showed cell viability of at least 95%. The new alloys are promising candidates for biomedical applications due to their high mechanical properties, corrosion resistance, and reduced cytotoxicity.

  20. Interfacial Microstructure and Mechanical Strength of 93W/Ta Diffusion-Bonded Joints with Ni Interlayer

    NASA Astrophysics Data System (ADS)

    Luo, Guoqiang; Zhang, Jian; Li, Meijuan; Wei, Qinqin; Shen, Qiang; Zhang, Lianmeng

    2013-02-01

    93W alloy and Ta metal were successfully diffusion bonded using a Ni interlayer. Ni4W was found at the W-Ni interface, and Ni3Ta and Ni2Ta were formed at the Ni-Ta interface. The shear strength of the joints increases with increasing holding time, reaching a value of 202 MPa for a joint prepared using a 90-minute holding time at 1103 K (830 °C) and 20 MPa. The fracture of this joint occurred within the Ni/Ta interface.

  1. Charge modulation and structural transformation in TaTe2 studied by scanning tunneling microscopy/spectroscopy

    NASA Astrophysics Data System (ADS)

    Feng, Jiagui; Tan, Andrew; Wagner, Sean; Liu, Jinyu; Mao, Zhiqiang; Ke, Xianglin; Zhang, Pengpeng

    2016-07-01

    We show that the (3 × 1) stripe structure observed in TaTe2 at room temperature arises from the formation of Ta4+-Ta4+ dimer chains along with a separate chain of Ta3+. More importantly, we reveal an intriguing lattice distortion and charge modulation at low temperature, which suggests an interplay and competition between the triple-axis (3 × 3) charge density wave-like modulation and the single-axis (3 × 1) stripe configuration. This work highlights the importance of TaTe2 as an alternative platform with rich structural and electrical phases to explore charge-lattice coupling.

  2. Ground-based tests of JEM-EUSO components at the Telescope Array site, "EUSO-TA"

    NASA Astrophysics Data System (ADS)

    Adams, J. H.; Ahmad, S.; Albert, J.-N.; Allard, D.; Anchordoqui, L.; Andreev, V.; Anzalone, A.; Arai, Y.; Asano, K.; Ave Pernas, M.; Baragatti, P.; Barrillon, P.; Batsch, T.; Bayer, J.; Bechini, R.; Belenguer, T.; Bellotti, R.; Belov, K.; Berlind, A. A.; Bertaina, M.; Biermann, P. L.; Biktemerova, S.; Blaksley, C.; Blanc, N.; Błȩcki, J.; Blin-Bondil, S.; Blümer, J.; Bobik, P.; Bogomilov, M.; Bonamente, M.; Briggs, M. S.; Briz, S.; Bruno, A.; Cafagna, F.; Campana, D.; Capdevielle, J.-N.; Caruso, R.; Casolino, M.; Cassardo, C.; Castellinic, G.; Catalano, C.; Catalano, G.; Cellino, A.; Chikawa, M.; Christl, M. J.; Cline, D.; Connaughton, V.; Conti, L.; Cordero, G.; Crawford, H. J.; Cremonini, R.; Csorna, S.; Dagoret-Campagne, S.; de Castro, A. J.; De Donato, C.; de la Taille, C.; De Santis, C.; del Peral, L.; Dell'Oro, A.; De Simone, N.; Di Martino, M.; Distratis, G.; Dulucq, F.; Dupieux, M.; Ebersoldt, A.; Ebisuzaki, T.; Engel, R.; Falk, S.; Fang, K.; Fenu, F.; Fernández-Gómez, I.; Ferrarese, S.; Finco, D.; Flamini, M.; Fornaro, C.; Franceschi, A.; Fujimoto, J.; Fukushima, M.; Galeotti, P.; Garipov, G.; Geary, J.; Gelmini, G.; Giraudo, G.; Gonchar, M.; González Alvarado, C.; Gorodetzky, P.; Guarino, F.; Guzmán, A.; Hachisu, Y.; Harlov, B.; Haungs, A.; Hernández Carretero, J.; Higashide, K.; Ikeda, D.; Ikeda, H.; Inoue, N.; Inoue, S.; Insolia, A.; Isgrò, F.; Itow, Y.; Joven, E.; Judd, E. G.; Jung, A.; Kajino, F.; Kajino, T.; Kaneko, I.; Karadzhov, Y.; Karczmarczyk, J.; Karus, M.; Katahira, K.; Kawai, K.; Kawasaki, Y.; Keilhauer, B.; Khrenov, B. A.; Kim, J.-S.; Kim, S.-W.; Kim, S.-W.; Kleifges, M.; Klimov, P. A.; Kolev, D.; Kreykenbohm, I.; Kudela, K.; Kurihara, Y.; Kusenko, A.; Kuznetsov, E.; Lacombe, M.; Lachaud, C.; Lee, J.; Licandro, J.; Lim, H.; López, F.; Maccarone, M. C.; Mannheim, K.; Maravilla, D.; Marcelli, L.; Marini, A.; Martinez, O.; Masciantonio, G.; Mase, K.; Matev, R.; Medina-Tanco, G.; Mernik, T.; Miyamoto, H.; Miyazaki, Y.; Mizumoto, Y.; Modestino, G.; Monaco, A.; Monnier-Ragaigne, D.; Morales de los Ríos, J. A.; Moretto, C.; Morozenko, V. S.; Mot, B.; Murakami, T.; Murakami, M. Nagano; Nagata, M.; Nagataki, S.; Nakamura, T.; Napolitano, T.; Naumov, D.; Nava, R.; Neronov, A.; Nomoto, K.; Nonaka, T.; Ogawa, T.; Ogio, S.; Ohmori, H.; Olinto, A. V.; Orleański, P.; Osteria, G.; Panasyuk, M. I.; Parizot, E.; Park, I. H.; Park, H. W.; Pastircak, B.; Patzak, T.; Paul, T.; Pennypacker, C.; Perez Cano, S.; Peter, T.; Picozza, P.; Pierog, T.; Piotrowski, L. W.; Piraino, S.; Plebaniak, Z.; Pollini, A.; Prat, P.; Prévôt, G.; Prieto, H.; Putis, M.; Reardon, P.; Reyes, M.; Ricci, M.; Rodríguez, I.; Rodríguez Frías, M. D.; Ronga, F.; Roth, M.; Rothkaehl, H.; Roudil, G.; Rusinov, I.; Rybczyński, M.; Sabau, M. D.; Sáez-Cano, G.; Sagawa, H.; Saito, A.; Sakaki, N.; Sakata, M.; Salazar, H.; Sánchez, S.; Santangelo, A.; Santiago Crúz, L.; Sanz Palomino, M.; Saprykin, O.; Sarazin, F.; Sato, H.; Sato, M.; Schanz, T.; Schieler, H.; Scotti, V.; Segreto, A.; Selmane, S.; Semikoz, D.; Serra, M.; Sharakin, S.; Shibata, T.; Shimizu, H. M.; Shinozaki, K.; Shirahama, T.; Siemieniec-Oziȩbło, G.; Silva López, H. H.; Sledd, J.; Słomińska, K.; Sobey, A.; Sugiyama, T.; Supanitsky, D.; Suzuki, M.; Szabelska, B.; Szabelski, J.; Tajima, F.; Tajima, N.; Tajima, T.; Takahashi, Y.; Takami, H.; Takeda, M.; Takizawa, Y.; Tenzer, C.; Tibolla, O.; Tkachev, L.; Tokuno, H.; Tomida, T.; Tone, N.; Toscano, S.; Trillaud, F.; Tsenov, R.; Tsunesada, Y.; Tsuno, K.; Tymieniecka, T.; Uchihori, Y.; Unger, M.; Vaduvescu, O.; Valdés-Galicia, J. F.; Vallania, P.; Valore, L.; Vankova, G.; Vigorito, C.; Villaseñor, L.; von Ballmoos, P.; Wada, S.; Watanabe, J.; Watanabe, S.; Watts, J.; Weber, M.; Weiler, T. J.; Wibig, T.; Wiencke, L.; Wille, M.; Wilms, J.; Włodarczyk, Z.; Yamamoto, T.; Yamamoto, Y.; Yang, J.; Yano, H.; Yashin, I. V.; Yonetoku, D.; Yoshida, K.; Yoshida, S.; Young, R.; Zotov, M. Yu.; Zuccaro Marchi, A.

    2015-11-01

    We are conducting tests of optical and electronics components of JEMEUSO at the Telescope Array site in Utah with a ground-based "EUSO-TA" detector. The tests will include an engineering validation of the detector, cross-calibration of EUSO-TA with the TA fluorescence detector and observations of air shower events. Also, the proximity of the TA's Electron Light Source will allow for convenient use of this calibration device. In this paper, we report initial results obtained with the EUSO-TA telescope.

  3. Chemical diffusion: Another factor affecting the magnetoresistance ratio in Ta/CoFeB/MgO/CoFeB/Ta magnetic tunnel junction

    SciTech Connect

    Yang, Y.; Wang, W. X.; Yao, Y.; Liu, H. F.; Han, X. F.; Yu, R. C.; Naganuma, H.; Sakul, T. S.

    2012-07-02

    This letter investigates the microstructure and mean inner potential (MIP) profile of Ta/CoFeB/MgO/CoFeB/Ta magnetic tunnel junctions (MTJs) by high resolution transmission electron microscopy (HRTEM) and electron holography, respectively. The inconspicuous crystallization of MgO barrier is confirmed by HRTEM in the post-annealed sample at 250 Degree-Sign C. An obvious MIP difference is displayed in the Ta layers between the top and bottom of the MTJ, and elemental content difference of them is confirmed by energy dispersive spectroscopy. These results imply that the chemical diffusion can also give rise to a lower tunnel magnetoresistance ratio besides the inconspicuous crystallization of MgO barrier.

  4. New ternary tantalum borides containing boron dumbbells: Experimental and theoretical studies of Ta2OsB2 and TaRuB

    NASA Astrophysics Data System (ADS)

    Mbarki, Mohammed; Touzani, Rachid St.; Rehorn, Christian W. G.; Gladisch, Fabian C.; Fokwa, Boniface P. T.

    2016-10-01

    The new ternary transition metal-rich borides Ta2OsB2 and TaRuB have been successfully synthesized by arc-melting the elements in a water-cooled crucible under an argon atmosphere. The crystal structures of both compounds were solved by single-crystal X-ray diffraction and their metal compositions were confirmed by EDX analysis. It was found that Ta2OsB2 and TaRuB crystallize in the tetragonal Nb2OsB2 (space group P4/mnc, no. 128) and the orthorhombic NbRuB (space group Pmma, no. 51) structure types with lattice parameters a=5.878(2) Å, c=6.857(2) Å and a=10.806(2) Å, b=3.196(1) Å, c=6.312(2) Å, respectively. Furthermore, crystallographic, electronic and bonding characteristics have been studied by density functional theory (DFT). Electronic structure relaxation has confirmed the crystallographic parameters while COHP bonding analysis indicates that B2-dummbells are the strongest bonds in both compounds. Moreover, the formation of osmium dumbbells in Ta2OsB2 through a Peierls distortion along the c-axis, is found to be the origin of superstructure formation. Magnetic susceptibility measurements reveal that the two phases are Pauli paramagnets, thus confirming the theoretical DOS prediction of metallic character. Also hints of superconductivity are found in the two phases, however lack of single phase samples has prevented confirmation. Furthermore, the thermodynamic stability of the two modifications of AMB (A=Nb, Ta; M =Ru, Os) are studied using DFT, as new possible phases containing either B4- or B2-units are predicted, the former being the most thermodynamically stable modification.

  5. Reaction mechanisms of atomic layer deposition of TaN{sub x} from Ta(NMe{sub 2}){sub 5} precursor and H{sub 2}-based plasmas

    SciTech Connect

    Knoops, H. C. M.; Langereis, E.; Sanden, M. C. M. van de; Kessels, W. M. M.

    2012-01-15

    The reaction mechanisms of plasma-assisted atomic layer deposition (ALD) of TaN{sub x} using Ta(NMe{sub 2}){sub 5} were studied using quadrupole mass spectrometry (QMS). The fact that molecule dissociation and formation in the plasma have to be considered for such ALD processes was illustrated by the observation of 4% NH{sub 3} in a H{sub 2}-N{sub 2} (1:1) plasma. Using QMS measurements the reaction products during growth of conductive TaN{sub x} using a H{sub 2} plasma were determined. During the Ta(NMe{sub 2}){sub 5} exposure the reaction product HNMe{sub 2} was detected. The amount of adsorbed Ta(NMe{sub 2}){sub 5} and the amount of HNMe{sub 2} released were found to depend on the number of surface groups generated during the plasma step. At the beginning of the plasma exposure step the molecules HNMe{sub 2}, CH{sub 4}, HCN, and C{sub 2}H{sub 2} were measured. After an extended period of plasma exposure, the reaction products CH{sub 4} and C{sub 2}H{sub 2} were still present in the plasma. This change in the composition of the reaction products can be explained by an interplay of aspects including the plasma-surface interaction, the ALD surface reactions, and the reactions of products within the plasma. The species formed in the plasma (e.g., CH{sub x} radicals) can re-deposit on the surface and influence to a large extent the TaN{sub x} material composition and properties.

  6. Transgenic barley lines prove the involvement of TaCBF14 and TaCBF15 in the cold acclimation process and in frost tolerance.

    PubMed

    Soltész, Alexandra; Smedley, Mark; Vashegyi, Ildikó; Galiba, Gábor; Harwood, Wendy; Vágújfalvi, Attila

    2013-04-01

    The enhancement of winter hardiness is one of the most important tasks facing breeders of winter cereals. For this reason, the examination of those regulatory genes involved in the cold acclimation processes is of central importance. The aim of the present work was the functional analysis of two wheat CBF transcription factors, namely TaCBF14 and TaCBF15, shown by previous experiments to play a role in the development of frost tolerance. These genes were isolated from winter wheat and then transformed into spring barley, after which the effect of the transgenes on low temperature stress tolerance was examined. Two different types of frost tests were applied; plants were hardened at low temperature before freezing, or plants were subjected to frost without a hardening period. The analysis showed that TaCBF14 and TaCBF15 transgenes improve the frost tolerance to such an extent that the transgenic lines were able to survive freezing temperatures several degrees lower than that which proved lethal for the wild-type spring barley. After freezing, lower ion leakage was measured in transgenic leaves, showing that these plants were less damaged by the frost. Additionally, a higher Fv/Fm parameter was determined, indicating that photosystem II worked more efficiently in the transgenics. Gene expression studies showed that HvCOR14b, HvDHN5, and HvDHN8 genes were up-regulated by TaCBF14 and TaCBF15. Beyond that, transgenic lines exhibited moderate retarded development, slower growth, and minor late flowering compared with the wild type, with enhanced transcript level of the gibberellin catabolic HvGA2ox5 gene.

  7. Queer paradox/paradoxical queer: Anne Garréta's Pas un jour (2002).

    PubMed

    Cairns, Lucille

    2007-01-01

    This paper shows how Anne Garréta's Pas un jour (2002) is a decidedly queer text, in both the new and the old sense of that contested epithet. I examine three interrelated concerns central to Pas un jour. First, I analyze Garréta's mediation of desire in general: her own experiences of it; modalities thereof which subvert more 'normative' models of lesbianism; and her convergences with other gay, but male writers and theorists of desire such as Guy Hocquenghem, Gilles Deleuze and Michel Foucault. Second, I interrogate Garréta's dichotomy between desire and friendship, and adumbrate contrasts with Foucauldian theory. Finally, I scrutinize the meaning and value attributed to the particular body of desire with which Garréta is most commonly associated-homosexuality- and their links with those of a contemporary gay male writer, Dominique Fernandez. PMID:17804371

  8. The wheat aquaporin gene TaAQP7 confers tolerance to cold stress in transgenic tobacco.

    PubMed

    Huang, Chao; Zhou, Shiyi; Hu, Wei; Deng, Xiaomin; Wei, Shuya; Yang, Guangxiao; He, Guangyuan

    2014-01-01

    Aquaporin proteins (AQPs) have been shown to be involved in abiotic stress responses. However, the precise role of AQPs, especially in response to cold stress, is not understood in wheat (Triticum aestivum). In the present study, quantitative real time polymerase chain reaction (qRT-PCR) analysis revealed that TaAQP7 expression increased in leaves, but decreased in roots after cold treatment. Expression of TaAQP7 in tobacco plants resulted in increased root elongation and better growth compared with wild-type (WT) plants under cold stress. Moreover, after cold treatment, the transgenic tobacco lines exhibited higher chlorophyll contents, lower levels of malondialdehyde (MDA), and less ion leakage (IL) than WT plants. Thus, expression of TaAQP7 enhanced cold stress tolerance in transgenic tobacco. Taken together, our results suggest that TaAQP7 confers cold stress tolerance by relieving membrane damage in the transgenic plants.

  9. [Inspection of gas cylinders in storage at TA-54, Area L]. Volume 2, Final report

    SciTech Connect

    1994-06-23

    ERC sampled, analyzed, and rcontainerized when necessary gas cylinders containing various chemicals in storage at LANL TA-54 Area L. This report summarizes the operation. This is Volume 2 of five volumes.

  10. Evolution of planetary cores and the Earth-Moon system from Nb/Ta systematics.

    PubMed

    Münker, Carsten; Pfänder, Jörg A; Weyer, Stefan; Büchl, Anette; Kleine, Thorsten; Mezger, Klaus

    2003-07-01

    It has been assumed that Nb and Ta are not fractionated during differentiation processes on terrestrial planets and that both elements are lithophile. High-precision measurements of Nb/Ta and Zr/Hf reveal that Nb is moderately siderophile at high pressures. Nb/Ta values in the bulk silicate Earth (14.0 +/- 0.3) and the Moon (17.0 +/- 0.8) are below the chondritic ratio of 19.9 +/- 0.6, in contrast to Mars and asteroids. The lunar Nb/Ta constrains the mass fraction of impactor material in the Moon to less than 65%. Moreover, the Moon-forming impact can be linked in time with the final core-mantle equilibration on Earth 4.533 billion years ago.

  11. Characterization of Mechanical Properties of Cantilevered Nd2Fe14B/Ta Magnetic Microstructures

    NASA Astrophysics Data System (ADS)

    Jiang, Yonggang; Fujita, Takayuki; Uehara, Minoru; Zhang, Deyuan; Cai, Jun; Higuchi, Kohei; Maenaka, Kazusuke

    2011-11-01

    The mechanical properties of low-stress cantilevered Nd2Fe14B/Ta multilayered microstructures are characterized. The cantilevered microstructures are fabricated using silicon molding technique and XeF2 gas-phase silicon etching process. The magnetic microcantilevers show relatively high quality factors varying from 75 to 135. The Young's modulus of the Nd2Fe14B/Ta multilayered film is evaluated by fitting the resonance response of the microcantilevers, which is smaller than those of bulk Nd2Fe14B magnets due to the texture effect. The good mechanical properties of the microcantilevers indicate that Nd2Fe14B/Ta multilayered films can be used as a structural material for microsystem applications. In addition, the electromagnetic driving of the Nd2Fe14B/Ta magnetic microcantilever is also demonstrated.

  12. Pressure-Induced New Topological Weyl Semimetal Phase in TaAs

    NASA Astrophysics Data System (ADS)

    Zhou, Yonghui; Lu, Pengchao; Du, Yongping; Zhu, Xiangde; Zhang, Ganghua; Zhang, Ranran; Shao, Dexi; Chen, Xuliang; Wang, Xuefei; Tian, Mingliang; Sun, Jian; Wan, Xiangang; Yang, Zhaorong; Yang, Wenge; Zhang, Yuheng; Xing, Dingyu

    2016-09-01

    We report a new pressure-induced phase in TaAs with different Weyl fermions than the ambient structure with the aid of theoretical calculations, experimental transport and synchrotron structure investigations up to 53 GPa. We show that TaAs transforms from an ambient I 41m d phase (t -TaAs ) to a high-pressure hexagonal P -6 m 2 (h -TaAs ) phase at 14 GPa, along with changes of the electronic state from containing 24 Weyl nodes distributed at two energy levels to possessing 12 Weyl nodes at an isoenergy level, which substantially reduces the interference between the surface and bulk states. The new pressure-induced phase can be reserved upon releasing pressure to ambient condition, which allows one to study the exotic behavior of a single set of Weyl fermions, such as the interplay between surface states and other properties.

  13. Electrical and optical properties of Ta-Si-N thin films deposited by reactive magnetron sputtering

    SciTech Connect

    Oezer, D.; Sanjines, R.; Ramirez, G.; Rodil, S. E.

    2012-12-01

    The electrical and optical properties of Ta{sub x}Si{sub y}N{sub z} thin films deposited by reactive magnetron sputtering from individual Ta and Si targets were studied in order to investigate the effects of nitrogen and silicon contents on both properties and their correlation to the film microstructure. Three sets of fcc-Ta{sub x}Si{sub y}N{sub z} thin films were prepared: sub-stoichiometric Ta{sub x}Si{sub y}N{sub 0.44}, nearly stoichiometric Ta{sub x}Si{sub y}N{sub 0.5}, and over-stoichiometric Ta{sub x}Si{sub y}N{sub 0.56}. The optical properties were investigated by near-normal-incidence reflectivity and ellipsometric measurements in the optical energy range from 0.375 eV to 6.8 eV, while the d.c. electrical resistivity was measured in the van der Pauw configuration from 20 K to 300 K. The optical and electrical measurements were interpreted using the standard Drude-Lorentz model and the so-called grain boundary scattering model, respectively. The electronic properties were closely correlated with the compositional and structural modifications of the Ta{sub x}Si{sub y}N{sub z} films due to variations in the stoichiometry of the fcc-TaN{sub z} system and the addition of Si atoms. According to the nitrogen and silicon contents, fcc-Ta{sub x}Si{sub y}N{sub z} films can exhibit room temperature resistivity values ranging from 10{sup 2} {mu}{Omega} cm to about 6 Multiplication-Sign 10{sup 4} {mu}{Omega} cm. The interpretation of the experimental temperature-dependent resistivity data within the Grain Boundary Scattering model, combined with the results from optical investigations, showed that the mean electron transmission probability G and the free carriers concentration, N, are the main parameters that control the transport properties of these films. The results indicated that the correlation between electrical and optical measurements with the chemical composition and the nanostructure of the Ta{sub x}Si{sub y}N{sub z} thin films provides a pertinent and

  14. Visible Light Assisted Photocatalytic Hydrogen Generation by Ta2O5/Bi2O3, TaON/Bi2O3, and Ta3N5/Bi2O3 Composites

    DOE PAGES

    Adhikari, Shiba; Hood, Zachary D.; More, Karren Leslie; Ivanov, Ilia N.; Zhang, Lifeng; Gross, Michael; Lachgar, Abdou

    2015-06-15

    Composites comprised of two semiconducting materials with suitable band gaps and band positions have been reported to be effective at enhancing photocatalytic activity in the visible light region of the electromagnetic spectrum. Here, we report the synthesis, complete structural and physical characterizations, and photocatalytic performance of a series of semiconducting oxide composites. UV light active tantalum oxide (Ta2O5) and visible light active tantalum oxynitride (TaON) and tantalum nitride (Ta3N5) were synthesized, and their composites with Bi2O3 were prepared in situ using benzyl alcohol as solvent. The composite prepared using equimolar amounts of Bi2O3 and Ta2O5 leads to the formation ofmore » the ternary oxide, bismuth tantalate (BiTaO4) upon calcination at 1000 °C. The composites and single phase bismuth tantalate formed were characterized by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) surface area measurement, scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis diffuse reflectance spectroscopy, and photoluminescence. The photocatalytic activities of the catalysts were evaluated for generation of hydrogen using aqueous methanol solution under visible light irradiation (λ ≥ 420 nm). The results show that as-prepared composite photocatalysts extend the light absorption range and restrict photogenerated charge-carrier recombination, resulting in enhanced photocatalytic activity compared to individual phases. The mechanism for the enhanced photocatalytic activity for the heterostructured composites is elucidated based on observed activity, band positions calculations, and photoluminescence data.« less

  15. Structural and electronic properties of TaSi(n) (n=1-13) clusters: a relativistic density functional investigation.

    PubMed

    Guo, Ping; Ren, Zhao-Yu; Wang, Fan; Bian, Jiang; Han, Ju-Guang; Wang, Guang-Hou

    2004-12-22

    The TaSi(n) (n=1-13) clusters with doublet, quartet, and sextet spin configurations have been systematically investigated by a relativistic density functional theory with the generalized gradient approximation available in Amsterdam density functional program. The total bonding energies, equilibrium geometries, Mulliken populations as well as Hirshfeld charges of TaSi(n) (n=1-13) clusters are calculated and presented. The emphasis on the stabilities and electronic properties is discussed. The most stable structures of the small TaSi(n) (n=1-6) clusters and the evolutional rule of low-lying geometries of the larger TaSi(n) (n=7-13) clusters are obtained. Theoretical results indicate that the most stable structure of TaSi(n) (n=1-6) clusters keeps the similar framework as the most stable structure of Si(n+1) clusters except for TaSi(3) cluster. The Ta atom in the lowest-energy TaSi(n) (n=1-13) isomers occupies a gradual sinking site, and the site moves from convex, to flatness, and to concave with the number of Si atom varying from 1 to 13. When n=12, the Ta atom in TaSi(12) cluster completely falls into the center of the Si frame, and a cagelike TaSi(12) geometry is formed. Meanwhile, the net Mulliken and Hirsheld populations of the Ta atom in the TaSi(n) (n=1-13) clusters vary from positive to negative, manifesting that the charges in TaSi(n) (n>/=12) clusters transfer from Si atoms to Ta atom. Additionally, the contribution of Si-Si and Si-Ta interactions to the stability of TaSi(n) clusters is briefly discussed. Furthermore, the investigations on atomic averaged binding energies and fragmentation energies show that the TaSi(n) (n=2,3,5,7,10,11,12) clusters have enhanced stabilities. Compared with pure silicon clusters, a universal narrowing of highest occupied molecular orbital-lowest unoccupied molecular orbital gap in TaSi(n) clusters is found.

  16. Unique LaTaO[subscript 4] Polymorph for Multiple Energy Applications

    SciTech Connect

    Nyman, May; Rodriguez, Mark A.; Rohwer, Lauren E.S.; Martin, James E.; Waller, Mollie; Osterloh, Frank E.

    2009-11-04

    Rare-earth niobate and tantalate (RE-Nb/Ta) materials are of considerable interest in environmental and energy-related applications that include phosphors for solid-state lighting, photocatalysts for both contaminant degeneration and H{sub 2} generation, chemically robust hosts for nuclear materials and wastes, and ion conductors for lithium batteries or solid-oxide fuel cells. However, the chemically inert nature limits the synthetic routes available to obtain these materials, which in turn hampers the discovery and development of new RE-Nb/Ta phases. Of the simple orthotantalate, LaTaO{sub 4}, there were three polymorphs known prior. With this paper, we present the structural characterization (from high-resolution X-ray powder diffraction data collected at the APS 11-BM line) of a fourth polymorph. It is obtained only from dehydration of La{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2}, which is in turn synthesized hydrothermally. The structure of the new LaTaO{sub 4} polymorph is distinctive from the others in the arrangement of the alternating La-O polyhedra layers and TaO{sub 6} octahedra layers. Luminescence measurements (Eu-doped) and photocatalysis studies of the new LaTaO{sub 4} polymorph, and comparison to the performance of a previously described LaTaO{sub 4} polymorph reveals enhanced performance of the new polymorph in both applications. This study illustrates the relevance of form-function relationships in solid-state materials, as well as the important role of synthesis in the development of advanced functional materials.

  17. Development of X-Shape Filtered Arc Deposition Apparatus for Thick ta-C Film Coating

    NASA Astrophysics Data System (ADS)

    Hikokasa, Hiroki; Iwasaki, Yasuhiro; Takikawa, Hirofumi; Sakakibara, Tateki; Hasegawa, Hiroshi; Tsuji, Nobuhiro

    Novel X-shape filtered arc deposition (X-FAD) apparatus is specially designed and newly developed for thick hydrogen-free tetrahedral amorphous-carbon (ta-C) film coating on superhard alloy (or cemented carbide) substrate. The apparatus has a graphite cathode for deposition of hydrogen-free diamond-like carbon (DLC; ta-C and amorphous carbon: a-C) film and a chromium (Cr) cathode for deposition of Cr layer. The filter duct shapes a composed form of a T-shape filter (T-FAD) for DLC film and a crank-shape filter (Crank FAD) for Cr film. Both carbon plasma beam and Cr plasma beam finally pass through a common plasma duct and scanner part, and go forward to the substrate. It is known that the adhesion of ta-C film to the superhard alloy is not good and the employment of binding interlayer between ta-C film and superhard alloy is one of the solutions. In this paper, using X-FAD, thick ta-C film was prepared on the superhard alloy. Principal results were as follows. (1) Crank FAD remarkably worked to prepare droplet-free Cr film. (2) Cr single layer did not work as appropriate biding interlayer between superhard alloy and ta-C. (3) Multi interlayer composed of Cr, a-C, and functionally graded DLC (a-C to ta-C), worked as a good biding interlayer for ta-C film on superhard alloy with thickness of more than 1 μm.

  18. Oxygen related recombination defects in Ta{sub 3}N{sub 5} water splitting photoanode

    SciTech Connect

    Fu, Gao; Yu, Tao E-mail: yutao@nju.edu.cn; Zou, Zhigang; Yan, Shicheng E-mail: yutao@nju.edu.cn

    2015-10-26

    A key route to improving the performance of Ta{sub 3}N{sub 5} photoelectrochemical film devices in solar driving water splitting to hydrogen is to understand the nature of the serious recombination of photo-generated carriers. Here, by using the temperature-dependent photoluminescence (PL) spectrum, we confirmed that for the Ta{sub 3}N{sub 5} films prepared by nitriding Ta{sub 2}O{sub 5} precursor, one PL peak at 561 nm originates from deep-level defects recombination of the oxygen-enriched Ta{sub 3}N{sub 5} phases, and another one at 580 nm can be assigned to band recombination of Ta{sub 3}N{sub 5} itself. Both of the two bulk recombination processes may decrease the photoelectrochemical performance of Ta{sub 3}N{sub 5}. It was difficult to remove the oxygen-enriched impurities in Ta{sub 3}N{sub 5} films by increasing the nitriding temperatures due to their high thermodynamically stability. In addition, a broadening PL peak between 600 and 850 nm resulting from oxygen related surface defects was observed by the low-temperature PL measurement, which may induce the surface recombination of photo-generated carriers and can be removed by increasing the nitridation temperature. Our results provided direct experimental evidence to understand the effect of oxygen-related crystal defects in Ta{sub 3}N{sub 5} films on its photoelectric performance.

  19. Synthesis of mesoporous sulfur-doped Ta2O5 nanocomposites and their photocatalytic activities.

    PubMed

    Ismail, Adel A; Faisal, M; Harraz, Farid A; Al-Hajry, A; Al-Sehemi, A G

    2016-06-01

    Mesoporous sulfur (S)-doped Ta2O5 nanocomposites have been synthesized for the first time through the sol-gel reaction of tantalum chloride and thiourea in the presence of a F127 triblock copolymer as structure directing agent. The as-formed mesophase S-doped Ta2O5 hybrid gels were calcined at 700°C for 4h to obtain mesoporous S-Ta2O5 nanocomposites. The experimental results indicated that the surface area of the S-doped Ta2O5 was up to 50m(2)g(-1) and the pore diameter was controllable in the range of 3-7.7nm. The S-doped Ta2O5 nanocomposites behave as superior visible light-sensitive photocatalysts and the 1.5at.% S-doped Ta2O5 (S1.5) photocatalyst exhibited excellent photocatalytic activity of ∼92% for the photodegradation of methylene blue, identical to 80% TOC removal after three hours illumination under visible light. The photodegradation rate of S1.5 photocatalyst showed 3.4 times higher than the undoped Ta2O5 due to their narrow bandgap, large surface area, mesostructure and well crystalline state. The S1.5 photocatalyst could be recycled at least five times without an apparent decrease in its photocatalytic efficiency, indicating its high stability for practical applications. To the best of our knowledge, this is the first report that demonstrates one-step synthesis of mesoporous S-doped Ta2O5 nanocomposites as an efficient photocatalysts under visible light illumination. PMID:27017474

  20. A View from the Cocoon--Space Categorization in the Korean Verb [na-ka-ta].

    ERIC Educational Resources Information Center

    Kim, Alan Hyun-Oak

    1996-01-01

    Analysis of the Korean verb "na-ka-ta" ("to get out, exit") focuses on why an expression such as "kyengkicang-ey na-ka-ta" ("someone goes out/in to the sports arena") is acceptable only in the context that the person's entering the arena is for the purpose of a contest, while it becomes semantically anomalous if intended to express the situation…

  1. A Linear Accelerator for TA-FD calibration

    NASA Astrophysics Data System (ADS)

    Shibata, T.; Ikeda, D.; Ikeda, M.; Enomoto, A.; Ohsawa, S.; Kakiha, K.; Kakihara, K.; Sagawa, H.; Satoh, M.; Shidara, T.; Sugimura, T.; Fukushima, M.; Fukuda, S.; Furukawa, K.; Yoshida, M.

    The energy of the primary cosmic ray can be calculated from fluorescence photons detected by fluorescence telescope. However, since we can not know the true energy of primary cosmic ray, it is difficult to calibrate between number of photons and energy directly. In TA project, we will create pseudo- cosmic ray events by using accelerated electron beam which is injected in the air. The injected electron beam creates an air shower and fluorescence photons are emitted. We can calibate between electron beam energy which is known exactry and detected photons. We are developping a small linear accelerator (Linac) at High Energy Accelerator Research Organization (KEK) in Japan. The maximum energy is 40MeV, the typical current is 0.16nC, and the intensity per pulse is 6.4mJ. The accuracy of beam energy is less than 1%. The Linac consists of a -100kV pulse type electron gun, a 1.5m pre-buncher and buncher tube, a 2m S-band accelerator tube, a quadrupole magnet, a 90 degree bending magnet, and a S-Band(2856MHz) 50MW high power klystron as RF source. We chekced the performance of the electron beam, energy resolution, beam spread, beam current, and beam loss by PARMELA simulation, and checked the air shower by electron beam and number of the detected photons by detector simulation which are made by GEANT4. In this Spring, we will do the full beam test in KEK. The beam operation in Utah will be started from this Autumn. In this talk, we will report about the results of the beam test and calibration method by this Linac.

  2. Effect of deposition and annealing temperature on mechanical properties of TaN film

    NASA Astrophysics Data System (ADS)

    Liu, X.; Ma, G. J.; Sun, G.; Duan, Y. P.; Liu, S. H.

    2011-11-01

    Tantalum nitride films (TaN) were synthesized by microwave ECR-DC sputtering. The effects of deposition and annealing temperature on mechanical properties of TaN films were investigated. Cross-section pattern, microstructure and binding energy of the films were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. Mechanical properties were evaluated using nano-indentation and scratch tester. The results showed that the maximal hardness value of approximately 40 GPa was deposited in the TaN sample at 573 K. While the preparation temperature decreased, the hardness, modulus and adhesion of TaN film also decreased. Hardness and modulus also decreased with the increase in annealing temperature. Meanwhile the adhesion strength was also sensitive to the annealing temperature, with a maximum adhesion strength of 40 N measured in the TaN film annealed at 448 K. The results demonstrated that a desirable mechanical property of TaN films deposited by DC reactive magnetron sputtering can be obtained by controlling the deposition and annealing temperature.

  3. Characteristics of sputtered TaX absorbers for x-ray mask

    NASA Astrophysics Data System (ADS)

    Sheu, Jeng Tzong; Chu, A.; Ding, J. H.; Su, Shyang

    1999-06-01

    The materials of x-ray absorbers for x-ray mask have been changed from gold and tungsten-based alloys to tantalum (Ta) and Ta-based compounds in x-ray lithography. Different candidates of x-ray absorber, especially Ta-based compounds, were sputtered and evaluated in this study. By incorporating silicon or germanium into tantalum, amorphous TaSi-based and TaGe-based compounds were formed and qualified as the absorber materials. Because the reproducibility of as- deposited stress by tuning the sputtering parameters is not so well for these compounds right after sputtering, we utilized the step annealing by RTA to control the stress such that within +/- MPa is obtainable. Furthermore, with N2 plasma treatment in PECVD chamber the slope of stress with respect to annealing temperature is smaller and posses good stability after long-time exposure to the air. Finally, the etching properties of TaX compounds were compared with and without tri-layer structure of oxide/absorber/oxide. And, 0.35 micrometers patterns are etched successfully with vertical sidewall by Cl2 etchant.

  4. Glass formation and cluster evolution in the rapidly solidified monatomic metallic liquid Ta under high pressure

    NASA Astrophysics Data System (ADS)

    Jiang, Dejun; Wen, Dadong; Tian, Zean; Liu, Rangsu

    2016-12-01

    Molecular dynamics (MD) simulations have been performed to examine the glass formation and cluster evolution during the rapid solidification of monatomic metallic liquid Ta under high pressure. The atomic structures in the systems are characterized by the radical distribution function (RDF), Honeycutt-Anderson (H-A) bond-type index method and cluster-type index method (CTIM). It is observed that the defective icosahedra play the critical role in the formation of Ta monatomic metallic glasses (MGs) rather than (12 0 12 0) perfect icosahedra, which have been identified as the basic local atomic units in many multi-component MGs. With the increase of pressure P, the fraction of icosahedral type clusters decreases remarkably in Ta MGs, while the fraction of bcc type clusters rises evidently. The evolution of vitrification degree (DSRO or DMRO) of the rapidly cooled metal Ta system further reveals that a higher pressure P is disadvantageous to the formation of Ta monatomic MGs. The weaker glass forming ability (GFA) of liquid metal Ta obtained under higher pressure P can be contributed to the decrease of DSRO or DMRO which is induced by increasing high pressure P to some extent.

  5. Anisotropic thermal transport in Weyl semimetal TaAs: a first principles calculation.

    PubMed

    Ouyang, Tao; Xiao, Huaping; Tang, Chao; Hu, Ming; Zhong, Jianxin

    2016-06-22

    A fundamental understanding of the phonon transport property is crucial to predict the thermal management performance in micro/nano-electronic devices. By combining first principle calculations and Boltzmann phonon transport equation, we investigate thermal transport in TaAs-a typical Weyl semimetal. The lattice thermal conductivity of TaAs at room temperature was found to be 39.26 W mK(-1) and 24.78 W mK(-1) along the a(b) and c crystal axis, respectively, showing obvious anisotropy. Detailed analyses of the mode level phonon properties further revealed that the three acoustic phonon modes dominate the overall thermal transport and the major phonon scattering channels in this typical Weyl semimetal were TA1/TA2/LA + O ↔ O and A + A ↔ O. The representative phonon mean free path of TaAs was also calculated in this paper, which provide helpful guidance for the thermal management of TaAs-based electronic devices. PMID:27271203

  6. Thermally stimulated luminescence from vapor-transport-equilibrated LiTaO3 crystals

    NASA Astrophysics Data System (ADS)

    Chirila, M. M.; Garces, N. Y.; Halliburton, L. E.; Evans, D. R.; Route, R. K.; Fejer, M. M.

    2003-07-01

    Thermally stimulated luminescence (TSL), optical absorption, and electron paramagnetic resonance (EPR) have been used to characterize the emission of ultraviolet light from undoped LiTaO3. The crystals in this study were grown from a congruent melt and then subjected to a vapor-transport-equilibration (VTE) treatment. Two overlapping TSL peaks occur at 94 and 98 K, with each showing a 350 nm maximum in its spectral emission. These peaks are observed after a 77 K exposure of the crystals to x rays or lasers (266, 325, or 355 nm). Congruent crystals from the same boule (but not VTE treated) produced no measurable emission in similar experiments. During excitation of the VTE-treated crystals at 77 K, holes are localized on oxygen ions, either self-trapped or with a nearby stabilizer, and electrons are trapped at regular Ta5+ ions and at Fe3+ impurities (present at trace levels), where they form Ta4+ and Fe2+ ions. The hole centers and the Fe3+ ions have characteristic EPR spectra, and a broad optical absorption band peaking near 1600 nm is attributed to the Ta4+ electron center. Upon warming, the trapped hole centers formed during the initial excitation become unstable below 100 K and move to Ta4+ ions, thus causing radiative recombination in the TaO6 units.

  7. Ab initio study of TaON, an active photocatalyst under visible light irradiation.

    PubMed

    Reshak, A H

    2014-06-14

    Tantalum oxynitride has been studied as an active photocatalyst under visible light, using a full potential linearized augmented plane wave method within the framework of density functional theory. The electronic and optical properties of TaON are calculated using local density approximation (LDA), generalized gradient approximation (GGA), Engel-Vosko generalized gradient approximation (EVGGA) and the modified Becke-Johnson (mBJ) potential approximation to describe the exchange-correlation potential. The calculated band gap value obtained by the mBJ approximation approach (2.5 eV) is very close to the experimental result (2.5 eV). We found that hybridization among the Ta-d, O-p and N-p states results in the formation of a covalent bond between Ta-N and Ta-O. The calculated optical properties confirm that the TaON is an active photocatalyst under visible light irradiation. TaON has a high dielectric constant and the components show anisotropy in the energy range between 3.0 eV and 10.0 eV. A high refractive index of 2.47 at 632.8 nm is obtained which shows better agreement with the experimental value (2.5 at 632.8 nm) than previous results.

  8. Redetermination of tantalum penta­bromide, (TaBr5)2

    PubMed Central

    Habermehl, Katja; Pantenburg, Ingo; Meyer, Gerd

    2010-01-01

    Crystals of di-μ-bromido-bis­[tetra­bromidotantalum(V)], (TaBr5)2, were obtained by recrystallization at 773 K. A first crystal structure study of (TaBr5)2 was reported by Rolsten [J. Am. Chem. Soc. (1958) ▶, 80, 2952–2953], who analysed the powder diffraction pattern and came to the conclusion that it crystallizes isotypically with (NbBr5)2 in a primitive ortho­rhom­bic cell. These findings are not in agreement with our current results of a monoclinic C-centred structure. (TaBr5)2 is isotypic with α-(NbCl5)2. The crystal structure contains [TaBr6] octa­hedra sharing common edges forming [TaBr5]2 dimers. Two crystallographically independent dimers with symmetries m and 2/m and Ta⋯Ta distances of 4.1574 (11) and 4.1551 (15) Å, respectively, are present in the structure. PMID:21588474

  9. Nanotube nucleation phenomena on Ti-25Ta-xZr alloys for implants using ATO technique.

    PubMed

    Kim, Hyun-Ju; Jeong, Yong-Hoon; Brantley, William A; Choe, Han-Cheol

    2014-10-01

    The purpose of this study was to investigate nanotube nucleation phenomena on the Ti-25Ta-xZr alloys for implant materials, using an anodic titanium oxide (ATO) technique. Ti-25Ta-(0 wt.%-15 wt.%) Zr alloys were prepared using a vacuum arc-melting furnace. The Ti-25Ta-xZr alloys were then homogenized for 12 hr at 1000 degrees C, followed by water quenching. Formation of the nanotubular oxide surface structure was achieved initially on the Ti-25Ta-xZr alloys by anodization in a 1 M H3PO4 electrolyte containing 0.8 wt.% NaF at room temperature, using a potentiostat. After the first formation of the nanotubes was achieved, this initial nanotube layer was eliminated, and further anodization was carried out repeatedly. The microstructure, phase transformation, and morphology of nanotubular Ti-25Ta-xZr alloys and the process of nanotube growth using this ATO method were analyzed by X-ray diffraction, field-emission scanning electron microscopy, and energy dispersive X-ray spectroscopy. Microstructures of the Ti-25Ta-xZr alloys changed from α" phase to β phase. Nanotubes formed with the ATO technique had pit-like top holes, with thinner walls and lower contact angle, compared to the initially formed nanotubes.

  10. The characteristics and functions of a miniature inverted-repeat transposable element TaMITE81 in the 5' UTR of TaCHS7BL from Triticum aestivum.

    PubMed

    Xi, Xinyuan; Li, Na; Li, Shiming; Chen, Wenjie; Zhang, Bo; Liu, Baolong; Zhang, Huaigang

    2016-10-01

    Miniature inverted-repeat transposable elements (MITEs) are truncated derivatives of autonomous DNA transposons, and are dispersed abundantly in eukaryotic and prokaryotic genomes. In this article, a MITE, TaMITE81, was isolated from the 5' untranslated region (UTR) of TaCHS7BL, chalcone synthase (CHS) catalyzing the first committed step of anthocyanin biosynthesis, in the wheat cultivar 'Opata' with white grain. TaMITE81 was only 81 nucleotides, including a terminal inverted repeat with 39 nucleotides and was flanked by two nucleotides, "TA", target site duplications that were typical features of stowaway-like MITEs. Compared with the wheat cultivar 'Gy115' with purple grain, which is without the insertion, the expression of TaCHS7BL was lower in several organs of 'Opata'. The insertion of TaMITE81 into the 5' UTR of the GUS gene also reduced the transient expression of GUS on the coleoptiles of 'Opata', which means the insertion of TaMITE81 was the reason for the low expression of TaCHS7BL in 'Opata'. But the genotype of TaCHS7BL was not linked to phenotype of grain color in the RILs derived from a cross 'Gy115' and 'Opata'. The TaMITE81 density of the hexaploid variety of T. aestivum was more than 10 times that of diploid relatives, which implies that polyploidization caused the amplification of TaMITE81 homologous sequences. Further research should be conducted on decoding the relationship between TaCHS7BL and other traits relative to anthocyanin biosynthesis in wheat, and discovering the mechanism of TaMITE81 transposon action. PMID:27481288

  11. Small-polaron transport and thermoelectric properties of the misfit-layer composite (BiSe)109TaSe2 / TaSe2

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Hee; Song, Yoo Jang; Rhyee, Jong-Soo; Kim, Bong-Seo; Park, Su-Dong; Lee, Hyeung Jin; Shin, Jae-Wook

    2014-03-01

    We studied the thermoelectric properties of the composite of misfit-layered compounds (BiSe)109TaSe2 and TaSe2. The x-ray diffraction pattern on the cross-sectional plane of the sintered body shows a preferred orientation of the (00 l) direction for (BiSe)109TaSe2 / TaSe2 indicating anisotropic alignment during hot pressing. Because of the crystallographic alignment, the temperature-dependent electrical resistivity ρ (T) , Seebeck coefficient S (T) , and the thermal conductivity κ (T) exhibit in-plane and out-of-plane anisotropic transport behavior. The Seebeck coefficient is very low because of the coexistence of electron and hole mixing, as confirmed by the two-carrier model. The lattice thermal conductivity κLof the covalent bonding layer (in-plane) is lower than those of the layer with van der Waals bonding (out-of-plane) implying the existence of a charge density wave along the in-plane. We observed a sign anomaly of the positive Hall coefficient RH and negative Seebeck coefficient S. According to Holstein's small-polaron model, the sign anomaly may come from the odd number of small-polaron hopping sites.

  12. Raman-spectroscopic investigation of Ba{sub 2}InTaO{sub 6} and Sr{sub 2}InTaO{sub 6} perovskites

    SciTech Connect

    Dias, A. Khalam, L.A.; Sebastian, M.T.; Moreira, R.L.

    2007-07-15

    Raman spectroscopy was employed to investigate the structures and phonon modes of Ba{sub 2}InTaO{sub 6} and Sr{sub 2}InTaO{sub 6} ceramics. It was found that Ba-based samples belong to the tetragonal P4/mnc (no. 128 or D{sub 4h}{sup 6}) space group, while Sr-based materials belong to the monoclinic P2{sub 1}/n (no. 14 or C{sub 2h}{sup 5}) space group. Low-temperature measurements did not show any phase transition down to 77K. Lorentzian lines were used to fit the experimental data, which presented 14 phonon modes for Ba{sub 2}InTaO{sub 6} and 24 modes for Sr{sub 2}InTaO{sub 6}, in perfect agreement with the theoretical factor-group analyses for the proposed structures. This paper reports, for the first time, a tetragonal P4/mnc structure for an indium-containing perovskite material.

  13. Electrochemical behavior of nanocrystalline Ta/TaN multilayer on 316L stainless steel: Novel bipolar plates for proton exchange membrane fuel-cells

    NASA Astrophysics Data System (ADS)

    Alishahi, M.; Mahboubi, F.; Mousavi Khoie, S. M.; Aparicio, M.; Hübner, R.; Soldera, F.; Gago, R.

    2016-08-01

    Insufficient corrosion resistance and surface conductivity are two main issues that plague large-scale application of stainless steel (SS) bipolar plates in proton exchange membrane fuel cells (PEMFCs). This study explores the use of nanocrystalline Ta/TaN multilayer coatings to improve the electrical and electrochemical performance of polished 316L SS bipolar plates. The multilayer coatings have been deposited by (reactive) magnetron sputtering and characterized by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. The electrochemical behavior of bare and coated substrates has been evaluated in simulated PEMFC working environments by potentiodynamic and potentiostatic polarization tests at ambient temperature and 80 °C. The results show that the Ta/TaN multilayer coating increases the polarization resistance of 316L SS by about 30 and 104 times at ambient and elevated temperatures, respectively. The interfacial contact resistance (ICR) shows a low value of 12 mΩ × cm2 before the potentiostatic test. This ICR is significantly lower than for the bare substrate and remains mostly unchanged after potentiostatic polarization for 14 h. In addition, the high contact angle (92°) with water for coated substrates indicates a hydrophobic character, which can improve the water management within the cell in PEMFC stacks.

  14. TaMCA1, a regulator of cell death, is important for the interaction between wheat and Puccinia striiformis

    PubMed Central

    Hao, Yingbin; Wang, Xiaojie; Wang, Kang; Li, Huayi; Duan, Xiaoyuan; Tang, Chunlei; Kang, Zhensheng

    2016-01-01

    Metacaspase orthologs are conserved in fungi, protozoa and plants, however, their roles in plant disease resistance are largely unknown. In this study, we identified a Triticum aestivum metacaspase gene, TaMCA1, with three copies located on chromosomes 1A, 1B and 1D. The TaMCA1 protein contained typical structural features of type I metacaspases domains, including an N-terminal pro-domain. Transient expression analyses indicated that TaMCA1 was localized in cytosol and mitochondria. TaMCA1 exhibited no caspase-1 activity in vitro, but was able to inhibit cell death in tobacco and wheat leaves induced by the mouse Bax gene. In addition, the expression level of TaMCA1 was up-regulated following challenge with the Puccinia striiformis f. sp. tritici (Pst). Knockdown of TaMCA1 via virus-induced gene silencing (VIGS) enhanced plant disease resistance to Pst, and the accumulation of hydrogen peroxide (H2O2). Further study showed that TaMCA1 decreased yeast cell resistance similar to the function of yeast metacaspase, and there was no interaction between TaMCA1 and TaLSD1. Based on these combined results, we speculate that TaMCA1, a regulator of cell death, is important during the compatible interaction of wheat and Pst. PMID:27230563

  15. TaMCA1, a regulator of cell death, is important for the interaction between wheat and Puccinia striiformis.

    PubMed

    Hao, Yingbin; Wang, Xiaojie; Wang, Kang; Li, Huayi; Duan, Xiaoyuan; Tang, Chunlei; Kang, Zhensheng

    2016-01-01

    Metacaspase orthologs are conserved in fungi, protozoa and plants, however, their roles in plant disease resistance are largely unknown. In this study, we identified a Triticum aestivum metacaspase gene, TaMCA1, with three copies located on chromosomes 1A, 1B and 1D. The TaMCA1 protein contained typical structural features of type I metacaspases domains, including an N-terminal pro-domain. Transient expression analyses indicated that TaMCA1 was localized in cytosol and mitochondria. TaMCA1 exhibited no caspase-1 activity in vitro, but was able to inhibit cell death in tobacco and wheat leaves induced by the mouse Bax gene. In addition, the expression level of TaMCA1 was up-regulated following challenge with the Puccinia striiformis f. sp. tritici (Pst). Knockdown of TaMCA1 via virus-induced gene silencing (VIGS) enhanced plant disease resistance to Pst, and the accumulation of hydrogen peroxide (H2O2). Further study showed that TaMCA1 decreased yeast cell resistance similar to the function of yeast metacaspase, and there was no interaction between TaMCA1 and TaLSD1. Based on these combined results, we speculate that TaMCA1, a regulator of cell death, is important during the compatible interaction of wheat and Pst. PMID:27230563

  16. Conditional gene expression in the epidermis of transgenic mice using the tetracycline-regulated transactivators tTA and rTA linked to the keratin 5 promoter.

    PubMed

    Diamond, I; Owolabi, T; Marco, M; Lam, C; Glick, A

    2000-11-01

    To produce conditional expression of genes in the mouse epidermis we have generated transgenic mouse lines in which the tetracycline-regulated transcriptional transactivators, tTA and rTA, are linked to the bovine keratin 5 promoter. The transactivator lines were crossed with the tetOlacZ indicator line to test for transactivation in vivo. In the absence of doxycycline, the K5/tTA line induced beta-galactosidase enzyme activity in the epidermis at a level 500-fold higher than controls, and oral and topical doxycycline caused a dose- and time-dependent suppression of beta-galactosidase mRNA levels and enzyme activity. In the K5/rTA lines, doxycycline induced beta-galactosidase activity between 3- and 50-fold higher depending on the founder line, and this occurred within 24-48 h after dosing. Histochemical analysis of all lines localized beta-galactosidase expression to the basal layer of the epidermis and the outer root sheath of the hair follicle, as well as other keratin 5 positive tissues. In several K5/rTA lines, skin-specific transactivation was restricted to the hair follicle. Treatment of these double transgenic mice with 12-O-tetradecanoyl-phorbol-13-acetate caused rapid migration of beta-galactosidase marked cells from the hair follicle through the interfollicular epidermis, demonstrating the usefulness of this specific double transgenic for fate mapping cells in the epidermis. These results show that the tetracycline regulatory system produces effective conditional gene expression in the mouse epidermis, and suggest that it should be amenable to suppression and activation of foreign genes during development and specific pathologic conditions relevant to the epidermis.

  17. Electrical and Electrochemical Properties of Nitrogen-Containing Tetrahedral Amorphous Carbon (ta-C) Thin Films

    NASA Astrophysics Data System (ADS)

    Yang, Xingyi

    Tetrahedral amorphous carbon (ta-C) is a diamond-like carbon (DLC) material comprised of a mixture of sp2 (˜40%) and sp3-bonded (˜60%) carbon domains. The physicochemical structure and electrochemical properties depend strongly on the sp2/sp3 bonding ratio as well as the incorporation of impurities, such as hydrogen or nitrogen. The ability to grow ta-C films at lower temperatures (25-100 °C) on a wider variety of substrates is a potential advantage of these materials as compared with diamond films. In this project, the basic structural and electrochemical properties of nitrogen-incorporated ta-C thin films will be discussed. The major goal of this work was to determine if the ta-C:N films exhibit electrochemical properties more closely aligned with those of boron-doped diamond (sp 3 carbon) or glassy carbon (amorphous sp2 carbon). Much like diamond, ta-C:N thin-film electrodes are characterized by a low background voltammetric current, a wide working potential window, relatively rapid electron-transfer kinetics for aqueous redox systems, such as Fe(CN) 6-3/-4 and Ru(NH3)6+3/+2 , and weak adsorption of polar molecules from solution. For example, negligible adsorption of methylene blue was found on the ta-C:N films in contrast to glassy carbon; a surface on which this molecule strongly adsorbs. The film microstructure was studied with x-ray photoelectron microscopy (XPS), visible Raman spectroscopy and electron-energy loss spectroscopy (EELS); all of which revealed the sp2-bonded carbon content increased with increasing nitrogen. The electrical properties of ta-C:N films were studied by four-point probe resistance measurement and conductive-probe AFM (CP-AFM). The incorporation of nitrogen into ta-C films increased the electrical conductivity primarily by increasing the sp2-bonded carbon content. CP-AFM showed the distribution of the conductive sp2-carbon on the film surface was not uniform. These films have potential to be used in field emission area. The

  18. Mechanisms of Low-Temperature Nitridation Technology on a TaN Thin Film Resistor for Temperature Sensor Applications

    NASA Astrophysics Data System (ADS)

    Chen, Huey-Ru; Chen, Ying-Chung; Chang, Ting-Chang; Chang, Kuan-Chang; Tsai, Tsung-Ming; Chu, Tian-Jian; Shih, Chih-Cheng; Chuang, Nai-Chuan; Wang, Kao-Yuan

    2016-06-01

    In this letter, we propose a novel low-temperature nitridation technology on a tantalum nitride (TaN) thin film resistor (TFR) through supercritical carbon dioxide (SCCO2) treatment for temperature sensor applications. We also found that the sensitivity of temperature of the TaN TFR was improved about 10.2 %, which can be demonstrated from measurement of temperature coefficient of resistance (TCR). In order to understand the mechanism of SCCO2 nitridation on the TaN TFR, the carrier conduction mechanism of the device was analyzed through current fitting. The current conduction mechanism of the TaN TFR changes from hopping to a Schottky emission after the low-temperature SCCO2 nitridation treatment. A model of vacancy passivation in TaN grains with nitrogen and by SCCO2 nitridation treatment is eventually proposed to increase the isolation ability in TaN TFR, which causes the transfer of current conduction mechanisms.

  19. Mechanisms of Low-Temperature Nitridation Technology on a TaN Thin Film Resistor for Temperature Sensor Applications.

    PubMed

    Chen, Huey-Ru; Chen, Ying-Chung; Chang, Ting-Chang; Chang, Kuan-Chang; Tsai, Tsung-Ming; Chu, Tian-Jian; Shih, Chih-Cheng; Chuang, Nai-Chuan; Wang, Kao-Yuan

    2016-12-01

    In this letter, we propose a novel low-temperature nitridation technology on a tantalum nitride (TaN) thin film resistor (TFR) through supercritical carbon dioxide (SCCO2) treatment for temperature sensor applications. We also found that the sensitivity of temperature of the TaN TFR was improved about 10.2 %, which can be demonstrated from measurement of temperature coefficient of resistance (TCR). In order to understand the mechanism of SCCO2 nitridation on the TaN TFR, the carrier conduction mechanism of the device was analyzed through current fitting. The current conduction mechanism of the TaN TFR changes from hopping to a Schottky emission after the low-temperature SCCO2 nitridation treatment. A model of vacancy passivation in TaN grains with nitrogen and by SCCO2 nitridation treatment is eventually proposed to increase the isolation ability in TaN TFR, which causes the transfer of current conduction mechanisms.

  20. Mechanisms of Low-Temperature Nitridation Technology on a TaN Thin Film Resistor for Temperature Sensor Applications.

    PubMed

    Chen, Huey-Ru; Chen, Ying-Chung; Chang, Ting-Chang; Chang, Kuan-Chang; Tsai, Tsung-Ming; Chu, Tian-Jian; Shih, Chih-Cheng; Chuang, Nai-Chuan; Wang, Kao-Yuan

    2016-12-01

    In this letter, we propose a novel low-temperature nitridation technology on a tantalum nitride (TaN) thin film resistor (TFR) through supercritical carbon dioxide (SCCO2) treatment for temperature sensor applications. We also found that the sensitivity of temperature of the TaN TFR was improved about 10.2 %, which can be demonstrated from measurement of temperature coefficient of resistance (TCR). In order to understand the mechanism of SCCO2 nitridation on the TaN TFR, the carrier conduction mechanism of the device was analyzed through current fitting. The current conduction mechanism of the TaN TFR changes from hopping to a Schottky emission after the low-temperature SCCO2 nitridation treatment. A model of vacancy passivation in TaN grains with nitrogen and by SCCO2 nitridation treatment is eventually proposed to increase the isolation ability in TaN TFR, which causes the transfer of current conduction mechanisms. PMID:27251325

  1. Temperature dependent magnetic coupling between ferromagnetic FeTaC layers in multilayer thin films

    NASA Astrophysics Data System (ADS)

    Singh, Akhilesh Kumar; Hsu, Jen-Hwa; Perumal, Alagarsamy

    2016-11-01

    We report systematic investigations on temperature dependent magnetic coupling between ferromagnetic FeTaC layers and resulting magnetic properties of multilayer structured [FeTaC (~67 nm)/Ta(x nm)]2/FeTaC(~67 nm)] thin films, which are fabricated directly on thermally oxidized Si substrate. As-deposited amorphous films are post annealed at different annealing temperatures (TA=200, 300 and 400 °C). Structural analyzes reveal that the films annealed at TA≤200 °C exhibit amorphous nature, while the films annealed above 200 °C show nucleation of nanocrystals at TA=300 °C and well-defined α-Fe nanocrystals with size of about 9 nm in amorphous matrix for 400 °C annealed films. Room temperature and temperature dependent magnetic hysteresis (M-H) loops reveal that magnetization reversal behaviors and magnetic properties are strongly depending on spacer layer thickness (x), TA and temperature. A large reduction in coercivity (HC) was observed for the films annealed at 200 °C and correlated to relaxation of stress quenched in during the film deposition. On the other hand, the films annealed at 300 °C exhibit unusual variation of HC(T), i.e., a broad minimum in HC(T) vs T curve. This is caused by change in magnetic coupling between ferromagnetic layers having different microstructure. In addition, the broad minimum in the HC(T) curve shifts from 150 K for x=1 film to 80 K for x=4 film. High-temperature thermomagnetization data show a strong (significant) variation of Curie temperature (TC) with TA (x). The multilayer films annealed at 200 °C exhibit low value of TC with a minimum of 350 K for x=4 film. But, the films annealed at 400 °C show largest TC with a maximum of 869 K for x=1 film. The observed results are discussed on the basis of variations in magnetic couplings between FeTaC layers, which are majorly driven by temperature, spacer layer thickness, annealing temperature and nature of interfaces.

  2. TaSYP71, a Qc-SNARE, Contributes to Wheat Resistance against Puccinia striiformis f. sp. tritici.

    PubMed

    Liu, Minjie; Peng, Yan; Li, Huayi; Deng, Lin; Wang, Xiaojie; Kang, Zhensheng

    2016-01-01

    N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) are involved in plant resistance; however, the role of SYP71 in the regulation of plant-pathogen interactions is not well known. In this study, we characterized a plant-specific SNARE in wheat, TaSYP71, which contains a Qc-SNARE domain. Three homologs are localized on chromosome 1AL, 1BL, and 1DL. Using Agrobacterium-mediated transient expression, TaSYP71 was localized to the plasma membrane in Nicotiana benthamiana. Quantitative real-time PCR assays revealed that TaSYP71 homologs was induced by NaCl, H2O2 stress and infection by virulent and avirulent Puccinia striiformis f. sp. tritici (Pst) isolates. Heterologous expression of TaSYP71 in Schizosaccharomyces pombe elevated tolerance to H2O2. Meanwhile, H2O2 scavenging gene (TaCAT) was downregulated in TaSYP71 silenced plants treated by H2O2 compared to that in control, which indicated that TaSYP71 enhanced tolerance to H2O2 stress possibly by influencing the expression of TaCAT to remove the excessive H2O2 accumulation. When TaSYP71 homologs were all silenced in wheat by the virus-induced gene silencing system, wheat plants were more susceptible to Pst, with larger infection area and more haustoria number, but the necrotic area of wheat mesophyll cells were larger, one possible explanation that minor contribution of resistance to Pst was insufficient to hinder pathogen extension when TaSYP71 were silenced, and the necrotic area was enlarged accompanied with the pathogen growth. Of course, later cell death could not be excluded. In addition, the expression of pathogenesis-related genes were down-regulated in TaSYP71 silenced wheat plants. These results together suggest that TaSYP71 play a positive role in wheat defense against Pst. PMID:27148348

  3. TaSYP71, a Qc-SNARE, Contributes to Wheat Resistance against Puccinia striiformis f. sp. tritici

    PubMed Central

    Liu, Minjie; Peng, Yan; Li, Huayi; Deng, Lin; Wang, Xiaojie; Kang, Zhensheng

    2016-01-01

    N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) are involved in plant resistance; however, the role of SYP71 in the regulation of plant–pathogen interactions is not well known. In this study, we characterized a plant-specific SNARE in wheat, TaSYP71, which contains a Qc-SNARE domain. Three homologs are localized on chromosome 1AL, 1BL, and 1DL. Using Agrobacterium-mediated transient expression, TaSYP71 was localized to the plasma membrane in Nicotiana benthamiana. Quantitative real-time PCR assays revealed that TaSYP71 homologs was induced by NaCl, H2O2 stress and infection by virulent and avirulent Puccinia striiformis f. sp. tritici (Pst) isolates. Heterologous expression of TaSYP71 in Schizosaccharomyces pombe elevated tolerance to H2O2. Meanwhile, H2O2 scavenging gene (TaCAT) was downregulated in TaSYP71 silenced plants treated by H2O2 compared to that in control, which indicated that TaSYP71 enhanced tolerance to H2O2 stress possibly by influencing the expression of TaCAT to remove the excessive H2O2 accumulation. When TaSYP71 homologs were all silenced in wheat by the virus-induced gene silencing system, wheat plants were more susceptible to Pst, with larger infection area and more haustoria number, but the necrotic area of wheat mesophyll cells were larger, one possible explanation that minor contribution of resistance to Pst was insufficient to hinder pathogen extension when TaSYP71 were silenced, and the necrotic area was enlarged accompanied with the pathogen growth. Of course, later cell death could not be excluded. In addition, the expression of pathogenesis-related genes were down-regulated in TaSYP71 silenced wheat plants. These results together suggest that TaSYP71 play a positive role in wheat defense against Pst. PMID:27148348

  4. Functional analysis of TaABF1 during abscisic acid and gibberellin signalling in aleurone cells of cereal grains.

    PubMed

    Harris, Lauren J; Martinez, Sarah A; Keyser, Benjamin R; Dyer, William E; Johnson, Russell R

    2013-06-01

    The wheat transcription factor TaABF1 physically interacts with the protein kinase PKABA1 and mediates both abscisic acid (ABA)-induced and ABA-suppressed gene expression. In bombarded aleurone cells of imbibing grains, the effect of TaABF1 in down-regulating the gibberellin (GA)-induced Amy32b promoter was stronger in the presence of exogenous ABA. As these grains contained low levels of endogenous ABA, the effect of TaABF1 may also be mediated by ABA-induced activation even in the absence of exogenous ABA. Levels of TaABF1 protein decreased slightly during imbibition of afterripened grains. However, TaABF1 levels (especially in aleurone layers) were not substantially affected by exogenous ABA or GA, indicating that changes in TaABF1 protein level are not an important part of regulating its role in hormone signalling. We found that TaABF1 was phosphorylated in vivo in aleurone cells, suggesting a role for post-translational modification in regulating TaABF1 activity. Induction of Amy32b by overexpression of the transcription factor GAMyb could not be prevented by TaABF1, indicating that TaABF1 acts upstream of GAMyb transcription in the signalling pathway. Supporting this view, knockdown of TaABF1 by RNA interference resulted in increased expression from the GAMyb promoter. These results are consistent with a model in which TaABF1 is constitutively present in aleurone cells, while its ability to down-regulate GAMyb is regulated in response to ABA.

  5. Photocatalytic and photoelectrochemical performance of Ta3N5 microcolumn films fabricated using facile reactive sputtering

    NASA Astrophysics Data System (ADS)

    Lin, Der-Hwa; Chang, Kao-Shuo

    2016-08-01

    This paper presents the photocatalytic and photoelectrochemical (PEC) properties of Ta3N5 microcolumn films. The highlights include (1) overcoming the fundamental barrier of standard reactive sputtering for fabricating microcolumns; (2) preventing unnecessary complexity from complicating facile sputtering; (3) an alternative but effective approach for fabricating Ta3N5 without using caustic NH3 gases; (4) investigating morphology tuning for favorable photocatalysis and PEC reactions; and (5) elucidating the relationships of the structures, morphologies, and properties of Ta3N5 microcolumns. High-resolution transmission electron microscopy and selective-area electron diffraction verified the polycrystallinity of Ta3N5 microcolumns, of which the elemental compositions and stoichiometry were measured using electron-probe energy dispersive spectroscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy. The corresponding band gap was determined to be approximately 2.1 eV. The sample exhibited a superior photodegradation capability; the photodegradation rate constant k was determined to be approximately 1.4 times higher than that of P25 under UV irradiation. A photocatalytic and PEC cycling test indicated the photodegradation reusability and photostability of the Ta3N5 microcolumns. The incident photon-to-current efficiency performance reached 6%, suggesting that these microcolumns hold potential for application in PEC devices.

  6. Layer-Confined Excitonic Insulating Phase in Ultrathin Ta2NiSe5 Crystals.

    PubMed

    Kim, So Young; Kim, Youngwook; Kang, Chang-Jong; An, Eun-Su; Kim, Hyoung Kug; Eom, Man Jin; Lee, Minkyung; Park, Chibeom; Kim, Tae-Hwan; Choi, Hee Cheul; Min, Byung Il; Kim, Jun Sung

    2016-09-27

    Atomically thin nanosheets, as recently realized using van der Waals layered materials, offer a versatile platform for studying the stability and tunability of the correlated electron phases in the reduced dimension. Here, we investigate a thickness-dependent excitonic insulating (EI) phase on a layered ternary chalcogenide Ta2NiSe5. Using Raman spectroscopy, scanning tunneling spectroscopy, and in-plane transport measurements, we found no significant changes in crystalline and electronic structures as well as disorder strength in ultrathin Ta2NiSe5 crystals with a thickness down to five layers. The transition temperature, Tc, of ultrathin Ta2NiSe5 is reduced from its bulk value by ΔTc/Tc(bulk) ≈ -9%, which strongly contrasts the case of 1T-TiSe2, another excitonic insulator candidate, showing an increase of Tc by ΔTc/Tc(bulk) ≈ +30%. This difference is attributed to the dominance of interband Coulomb interaction over electron-phonon interaction and its zero-ordering wave vector due to the direct band gap structure of Ta2NiSe5. The out-of-plane correlating length of the EI phase is estimated to have monolayer thickness, suggesting that the EI phase in Ta2NiSe5 is highly layer-confined and in the strong coupling limit.

  7. Charge transport mechanisms and memory effects in amorphous TaNx thin films

    PubMed Central

    2013-01-01

    Amorphous semiconducting materials have unique electrical properties that may be beneficial in nanoelectronics, such as low leakage current, charge memory effects, and hysteresis functionality. However, electrical characteristics between different or neighboring regions in the same amorphous nanostructure may differ greatly. In this work, the bulk and surface local charge carrier transport properties of a-TaNx amorphous thin films deposited in two different substrates are investigated by conductive atomic force microscopy. The nitride films are grown either on Au (100) or Si [100] substrates by pulsed laser deposition at 157 nm in nitrogen environment. For the a-TaNx films deposited on Au, it is found that they display a negligible leakage current until a high bias voltage is reached. On the contrary, a much lower threshold voltage for the leakage current and a lower total resistance is observed for the a-TaNx film deposited on the Si substrate. Furthermore, I-V characteristics of the a-TaNx film deposited on Au show significant hysteresis effects for both polarities of bias voltage, while for the film deposited on Si hysteresis, effects appear only for positive bias voltage, suggesting that with the usage of the appropriate substrate, the a-TaNx nanodomains may have potential use as charge memory devices. PMID:24134740

  8. Crystal structure and molecular modeling study of N-carbamoylsarcosine amidase Ta0454 from Thermoplasma acidophilum

    SciTech Connect

    Luo, Hai-Bin; Zheng, Heping; Zimmerman, Matthew D.; Chruszcz, Maksymilian; Skarina, Tatiana; Egorova, Olga; Savchenko, Alexei; Edwards, Aled M.; Minor, Wladek

    2010-05-12

    A crystal structure of the putative N-carbamoylsarcosine amidase (CSHase) Ta0454 from Thermoplasma acidophilum was solved by single-wavelength anomalous diffraction and refined at a resolution of 2.35 {angstrom}. CSHases are involved in the degradation of creatinine. Ta0454 shares a similar fold and a highly conserved C-D-K catalytic triad (Cys123, Asp9, and Lys90) with the structures of three cysteine hydrolases (PDB codes 1NBA, 1IM5, and 2H0R). Molecular dynamics (MD) simulations of Ta0454/N-carbamoylsarcosine and Ta0454/pyrazinamide complexes were performed to determine the structural basis of the substrate binding pattern for each ligand. Based on the MD-simulated trajectories, the MM/PBSA method predicts binding free energies of -24.5 and -17.1 kcal/mol for the two systems, respectively. The predicted binding free energies suggest that Ta0454 is selective for N-carbamoylsarcosine over pyrazinamide, and zinc ions play an important role in the favorable substrate bound states.

  9. Ductility Characterization of U-6Nb and Ta-W Alloys

    SciTech Connect

    Sun, T; Cervantes, O

    2006-09-15

    We have previously evaluated the ductility behaviors of U-6Nb and pure Ta. One important observation was that both alloys have very stable necking ductility independent of test conditions. In contrast, uniform ductility varied significantly depending upon strain rates and temperatures. In general, higher strain rate and lower temperature reduce the uniform ductility. Using literature data, we have developed two dynamic ductility models to predict the ductility behaviors of pure-Ta and water-quenched U-6Nb respectively under extreme conditions. In this study we further evaluate the aging effect on U-6Nb and the W-addition effect on Ta. For U-6Nb, the objective is to determine whether or not the ductility degradation by low-temperature aging mostly measured in quasi-static condition can still be observed under dynamic loading (high strain rate) condition. For Ta-W alloys, the focus is to identify the key control parameter so that the optimal condition of high-strength/high-ductility of Ta-10W can be achieved for certain defense-related applications.

  10. Effects of annealing on antiwear and antibacteria behaviors of TaN-Cu nanocomposite thin films

    SciTech Connect

    Hsieh, J. H.; Cheng, M. K.; Chang, Y. K.; Li, C.; Chang, C. L.; Liu, P. C.

    2008-07-15

    TaN-Cu nanocomposite films were deposited by reactive cosputtering on Si and tool steel substrates. The films were then annealed using rapid thermal annealing (RTA) at 400 deg. C for 2, 4, and 8 min, respectively, to induce the nucleation and growth of Cu particles in TaN matrix and on film surface. Field emission scanning electron microscopy was applied to characterize Cu nanoparticles emerged on the surface of TaN-Cu thin films. The effects of annealing on the antiwear and antibacterial properties of these films were studied. The results reveal that annealing by RTA can cause Cu nanoparticles to form on the TaN surface. Consequently, the tribological behaviors, as well as the antibacterial behavior may vary depending on particle size, particle distribution, and total exposed Cu amount. For the samples with large Cu particles, the reduction of averaged friction and wear rate is obvious. Apparently, it is due to the smeared Cu particles adhered onto the wear tracks. This Cu layer may act as a solid lubricant. From the antibacterial testing results, it is found that both Cu particle size and total exposed Cu amount are critical in making short-term antibacterial effect. Overall, all the annealed TaN-Cu samples can reach >99% antibacterial efficiency in 24 h, with respect to uncoated Si substrate.

  11. The ubiquitin conjugating enzyme, TaU4 regulates wheat defence against the phytopathogen Zymoseptoria tritici

    PubMed Central

    Millyard, Linda; Lee, Jack; Zhang, Cunjin; Yates, Gary; Sadanandom, Ari

    2016-01-01

    Mycosphaerella graminicola (Zymoseptoria tritici commonly known as Septoria), the causal agent of Septoria Leaf Blotch (STB), is considered one of the major threats to European wheat production. Previous studies have shown the importance of ubiquitination in plant defence against a multitude of pathogens. However the ubiquitination machinery in wheat is under studied, particularly E2 enzymes that have the ability to control the ubiquitination and thereby the fate of many different target proteins. In this study we identify an E2 enzyme, Triticum aestivum Ubiquitin conjugating enzyme 4 (TaU4) that functions in wheat defence against Septoria. We demonstrate TaU4 to be a bona fide E2 enzyme through an E2 charging assay. TaU4 localises in both the cytoplasm and nucleus, therefore potentially interacting with E3 ligases and substrate proteins in multiple compartments. Virus Induced Gene Silencing of TaU4 in wheat leaves resulted in delayed development of disease symptoms, reduced Septoria growth and reproduction. We conclude that TaU4 is a novel negative regulator of defence against Septoria. PMID:27759089

  12. Precessional magnetization induced spin current from CoFeB into Ta

    SciTech Connect

    Jamali, Mahdi; Klemm, Angeline; Wang, Jian-Ping

    2013-12-16

    The spin dynamics at the interface between the CoFeB and Ta layer has been studied using spin pumping and spin wave characterizations. The spin pumping driven by the ferromagnetic resonance in the CoFeB layer injects a spin current into Ta layer which results in an electromotive force across the Ta layer due to the inverse spin Hall effect. Upon changing the polarity of the bias magnetic field, the polarity of the output voltage inverts and the output voltage increases linearly in respect to the microwave signal power which are consistent with the spin pumping characteristics. The effect of the in-plane magnetization angle on the output voltage has been studied. Furthermore, it is found that the frequency spectrum of the spin Hall voltage is modified by the annealing temperature and the full width at half maximum of the spin pumping increases by more than 40% with the increase of the annealing temperature from 200 °C to 300 °C. The spin Hall angle at the Ta-CoFeB interface is determined to be 0.014, and the damping constant of the CoFeB increases from 0.006 in pure CoFeB to 0.015 in Ta/CoFeB film.

  13. Structural, electronic and optical properties of hexagonal TaN compound

    NASA Astrophysics Data System (ADS)

    Chen, Zhongjun; Yan, Jungan; Kuang, Zhong; Chen, Taihong; Li, Dehua

    2016-01-01

    Structural and electronic properties of hexagonal Tantalum nitride (TaN) in CoSn and WC structures are studied using the first-principle calculations. Lattice constants and electronic band structures are in an excellent agreement with the available experimental and other theoretical values. TaN in both structures studied has a metallic nature and a strong hybridization of Ta 5d and N 2p are found from the spin density of states (DOS). Meanwhile, our LSDA+U calculations predicted a strong ferromagnetic state for CoSn-type structure and an obvious paramagnetic nature for WC-type structure. No phase transition are observed within cubic and hexagonal CoSn and WC structures under high pressures. Our results show WC-type TaN is the calculated ground-state structure among the three crystallographic structures studied under 120 GPa. Optical properties show that TaN in CoSn-type structure is a better dielectric material.

  14. Superconducting proximity effect in inverted InAs/GaSb quantum well structures with Ta electrodes

    NASA Astrophysics Data System (ADS)

    Yu, Wenlong; Jiang, Yuxuan; Huan, Chao; Chen, Xunchi; Hawkins, Samuel D.; Klem, John F.; Jiang, Zhigang; Pan, Wei

    2014-03-01

    We report on a systematic study of the proximity effect in top-gated InAs/GaSb quantum wells in contact with a superconducting Ta electrode. We find that the electronic transport across the InAs-Ta interface exhibits distinct zero-bias behavior, either a conductance (dI/dV) peak or dip, depending on the interfacial transparency. For a relatively resistive interface, we observe a dI/dV peak at zero bias, accompanied by two dI/dV dips at high bias voltages, consistent with previous works. When a transparent InAs-Ta interface is achieved, a zero-bias dV/dI dip appears with two coherent-peak-like features forming at bias voltages corresponding to the superconducting gap of Ta. The dI/dV spectra of the transparent InAs-Ta interface at different gate voltages can be fit well using the standard BTK model and the temperature dependence follows a BCS-like behavior. Our work demonstrates the possibility of achieving the highly transparent interfaces in InAs/GaSb hybrid structures, needed for studying the intriguing Andreev bound states in this two-dimensional topological system.

  15. CO oxidation on Ta-Modified SnO2 solid solution catalysts

    NASA Astrophysics Data System (ADS)

    Han, Xue; Xu, Xianglan; Liu, Wenming; Wang, Xiang; Zhang, Rongbin

    2013-06-01

    Co-precipitation method was adopted to prepare Sn-Ta mixed oxide catalysts with different Sn/Ta molar ratios and used for CO oxidation. The catalysts were investigated by N2-Brunauer-Emmett-Teller (N2-BET), X-ray diffraction patterns (XRD), H2-temperature programmed reduction (H2-TPR), Thermal Gravity Analysis - Differential Scanning Calorimetry (TGA-DSC) techniques. It is revealed that a small amount of Ta cations can be doped into SnO2 lattice to form solid solution by co-precipitation method, which resulted in samples having higher surface areas, improved thermal stability and more deficient oxygen species on the surface of SnO2. As a result, those Sn rich Sn-Ta solid solution catalysts with an Sn/Ta molar ratio higher than 4/2 showed significantly enhanced activity as well as good resistance to water deactivation. It is noted here that if tantala disperses onto SnO2 surface instead of doping into its lattice, it will then have negative effect on its activity.

  16. Low temperature synthesis of monolithic transparent Ta2O5 gels from hydrolysis of metal alkoxide

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1993-01-01

    Tantalum oxide gels in the form of transparent monoliths and powder were prepared from hydrolysis of tantalum pentaethoxide under controlled conditions using different mole ratios of Ta(OC2H5)5:C2H50H:H20:HCl. Alcohol acts as the mutual solvent and HCl as the deflocculating agent. For a fixed alkoxide:water:HCl ratio, time of gel formation increased with the alcohol to alkoxide mole ratio. Thermal evolution of the physical and structural changes in the gel was monitored by differential thermal analysis, thermogravimetric analysis, x-ray diffraction, and infrared spectroscopy. On heating to approximately 400 C, the amorphous gel crystallized into the low temperature orthorhombic phase Beta-Ta2O5, which transformed into the high temperature tetragonal phase Alpha-Ta2O5 when further heated to approximately 1450 C. The volume fraction of the crystalline phase increased with the firing temperature. The Alpha-Ta205 converted back into the low temperature phase, Beta-Ta2O5, on slow cooling through the transformation temperature of 1360 C indicating a slow but reversible transformation.

  17. Comparison of low-voltage field emission from TaC and tungsten fiber arrays

    SciTech Connect

    Cochran, J.K.; Lee, K.J.; Hill, D.N.

    1988-01-01

    Field emitter array (FEA) devices were constructed using thin-film fabrication techniques based on in situ eutectic composites containing either TaC or NbC fibers in a NiCr alloy matrix. The emission characteristics of the TaC devices were measured and compared to those of W--ZrO/sub 2/ FEA's. Both devices produced the linear Fowler--Nordheim plots common to all field emission devices; however, the array current density of the TaC FEA's was more than two orders of magnitude lower than that of the W--ZrO/sub 2/ FEA's. This was primarily due to the lower fiber density and lower field enhancement of the carbide fiber devices. If it were possible to produce cathode geometries comparable to those of the W--ZrO/sub 2/ FEA's, a theoretical analysis indicates that emission performance of the TaC devices would be superior because of the lower work function of TaC. However, post-emission observations indicated that the carbide fiber emitters failed more readily than the tungsten emitters under comparable operating conditions.

  18. Decay heat calculations for a 500 kW W-Ta spallation target

    NASA Astrophysics Data System (ADS)

    Yu, Quanzhi; Lu, Youlian; Hu, Zhiliang; Zhou, Bin; Yin, Wen; Liang, Tianjiao

    2015-05-01

    The China Spallation Neutron Source (CSNS) is a short-pulsed neutron scattering facility. The beam power is designed to be 100 kW in Phase I, with the capability of upgrading to 500 kW. Tantalum (Ta)-cladded tungsten (W) was chosen as the spallation target due to its high neutron yield. Ta claddings can solve the problem of the corrosiveness of W plates, although they produce high decay heat after intense irradiation. This paper presents the decay heat distributions and evolutions for the future upgraded 500 kW W-Ta spallation target. The calculations are performed using the MCNPX2.5 Monte Carlo code and the CINDER'90 activation code. The decay heat distributions show that for the W plates, decay heat is mainly produced via the spallation reaction process, whereas for the Ta claddings, it is mainly produced via the neutron capture process. An effective method of reducing the decay heat in the W-Ta target is also presented and discussed.

  19. Ta2O5- and TiO2-based nanostructures made by atomic layer deposition.

    PubMed

    Kemell, Marianna; Härkönen, Emma; Pore, Viljami; Ritala, Mikko; Leskelä, Markku

    2010-01-22

    Nanotubular Ta(2)O(5)- and TiO(2)-based structures were prepared by atomic layer deposition of Ta(2)O(5) and TiO(2) thin films, conformally on pore walls of porous alumina membranes. Both self-supporting alumina membranes and Si-supported thin-film membranes were studied as templates. Long Ta(2)O(5) and TiO(2) nanotubes were prepared successfully with the self-supporting membranes. The TiO(2) nanotubes showed photocatalytic activity in methylene blue degradation under UV illumination. The Ta(2)O(5) and TiO(2) nanotubes were further modified by depositing Pt nanoparticles inside them. The Si-supported thin-film membranes were used as templates for the preparation of robust Ta(2)O(5)-coated Ni nanorod arrays on a Si substrate using electrodeposition, chemical etching and atomic layer deposition. In addition to photocatalysis, the nanostructures prepared in this work may find applications as other catalysts and as solid-state or electrochemical capacitors.

  20. Mechanical Properties, Quantum Mechanical Calculations, and Crystallographic/Spectroscopic Characterization of GaNbO4, Ga(Ta,Nb)O4, and GaTaO4.

    PubMed

    Perfler, Lukas; Kahlenberg, Volker; Többens, Daniel; Schaur, Andreas; Tribus, Martina; Orlova, Maria; Kaindl, Reinhard

    2016-06-01

    Single crystals as well as polycrystalline samples of GaNbO4, Ga(Ta,Nb)O4, and GaTaO4 were grown from the melt and by solid-state reactions, respectively, at various temperatures between 1698 and 1983 K. The chemical composition of the crystals was confirmed by wavelength-dispersive electron microprobe analysis, and the crystal structures were determined by single-crystal X-ray diffraction. In addition, a high-P-T synthesis of GaNbO4 was performed at a pressure of 2 GPa and a temperature of 1273 K. Raman spectroscopy of all compounds as well as Rietveld refinement analysis of the powder X-ray diffraction pattern of GaNbO4 were carried out to complement the structural investigations. Density functional theory (DFT) calculations enabled the assignment of the Raman bands to specific vibrational modes within the structure of GaNbO4. To determine the hardness (H) and elastic moduli (E) of the compounds, nanoindentation experiments have been performed with a Berkovich diamond indenter tip. Analyses of the load-displacement curves resulted in a high hardness of H = 11.9 ± 0.6 GPa and a reduced elastic modulus of Er = 202 ± 9 GPa for GaTaO4. GaNbO4 showed a lower hardness of H = 9.6 ± 0.5 GPa and a reduced elastic modulus of Er = 168 ± 5 GPa. Spectroscopic ellipsometry of the polished GaTa0.5Nb0.5O4 ceramic sample was employed for the determination of the optical constants n and k. GaTa0.5Nb0.5O4 exhibits a high average refractive index of nD = 2.20, at λ = 589 nm. Furthermore, in situ high-temperature powder X-ray diffraction experiments enabled the study of the thermal expansion tensors of GaTaO4 and GaNbO4, as well as the ability to relate them with structural features.

  1. Mechanical Properties, Quantum Mechanical Calculations, and Crystallographic/Spectroscopic Characterization of GaNbO4, Ga(Ta,Nb)O4, and GaTaO4.

    PubMed

    Perfler, Lukas; Kahlenberg, Volker; Többens, Daniel; Schaur, Andreas; Tribus, Martina; Orlova, Maria; Kaindl, Reinhard

    2016-06-01

    Single crystals as well as polycrystalline samples of GaNbO4, Ga(Ta,Nb)O4, and GaTaO4 were grown from the melt and by solid-state reactions, respectively, at various temperatures between 1698 and 1983 K. The chemical composition of the crystals was confirmed by wavelength-dispersive electron microprobe analysis, and the crystal structures were determined by single-crystal X-ray diffraction. In addition, a high-P-T synthesis of GaNbO4 was performed at a pressure of 2 GPa and a temperature of 1273 K. Raman spectroscopy of all compounds as well as Rietveld refinement analysis of the powder X-ray diffraction pattern of GaNbO4 were carried out to complement the structural investigations. Density functional theory (DFT) calculations enabled the assignment of the Raman bands to specific vibrational modes within the structure of GaNbO4. To determine the hardness (H) and elastic moduli (E) of the compounds, nanoindentation experiments have been performed with a Berkovich diamond indenter tip. Analyses of the load-displacement curves resulted in a high hardness of H = 11.9 ± 0.6 GPa and a reduced elastic modulus of Er = 202 ± 9 GPa for GaTaO4. GaNbO4 showed a lower hardness of H = 9.6 ± 0.5 GPa and a reduced elastic modulus of Er = 168 ± 5 GPa. Spectroscopic ellipsometry of the polished GaTa0.5Nb0.5O4 ceramic sample was employed for the determination of the optical constants n and k. GaTa0.5Nb0.5O4 exhibits a high average refractive index of nD = 2.20, at λ = 589 nm. Furthermore, in situ high-temperature powder X-ray diffraction experiments enabled the study of the thermal expansion tensors of GaTaO4 and GaNbO4, as well as the ability to relate them with structural features. PMID:27175821

  2. Effects of Ta Addition Through Co-Sputtering on the Electrical Characteristics of Indium Tin Oxide Thin Film Transistors.

    PubMed

    Park, Si-Nae; Son, Dae-Ho; Sung, Shi-Joon; Kang, Jin-Kyu; Kim, Dae-Hwan

    2015-01-01

    We have investigated the effects of adding (Ta) ions to InSnO thin films by co-sputtering on the performance of InSnO thin film transistors (TFTs). TaInSnO TFTs exhibited significantly lower off currents and higher on/off current ratios. Ta ions, owing to their strong affinity to oxygen suppress the formation of free electron carriers in thin films; and hence, play an important role in enhancing the electrical characteristics of the TFTs. The optimized TaInSnO TFTs showed high on/off ratios and low subthreshold swings. PMID:26328366

  3. Density functional study of TaSi n ( n = 1-3, 12) clusters adsorbed to graphene surface

    NASA Astrophysics Data System (ADS)

    Guo, Ping; Zheng, Lin; Zheng, Ji Ming; Zhang, Ruizhi; Yang, Luna; Ren, Zhaoyu

    2011-11-01

    A plane-wave density functional theory (DFT) calculations have been performed to investigate structural and electronic properties of TaSin (n = 1-3, 12) clusters supported by graphene surface. The resulting adsorption structures are described and discussed in terms of stability, bonding, and electron transfer between the cluster and the graphene. The TaSin clusters on graphene surface favor their free-standing ground-state structures. Especially in the cases of the linear TaSi2 and the planar TaSi3, the graphene surface may catalyze the transition of the TaSin clusters from an isomer of lower dimensionality into the ground-state structure. The adsorption site and configuration of TaSin on graphene surface are dominated by the interaction between Ta atom and graphene. Ta atom prefers to adsorb on the hollow site of graphene, and Si atoms tend to locate on the bridge site. Further, the electron transfer is found to proceed from the cluster to the surface for n = 1 and 2, while its direction reverses as n > 2. For the case of TaSi, chemisorption is shown to prevail over physisorption as the dominant mode of surface-adsorbate interaction by charge density analysis.

  4. Haplotypes of the TaGS5-A1 Gene Are Associated with Thousand-Kernel Weight in Chinese Bread Wheat

    PubMed Central

    Wang, Shasha; Yan, Xuefang; Wang, Yongyan; Liu, Hongmei; Cui, Dangqun; Chen, Feng

    2016-01-01

    In previous work, we cloned TaGS5 gene and found the association of TaGS5-A1 alleles with agronomic traits. In this study, the promoter sequence of the TaGS5-A1 gene was isolated from bread wheat. Sequencing results revealed that a G insertion was found in position -1925 bp of the TaGS5-A1 gene (Reference to ATG), which occurred in the Sp1 domain of the promoter sequence. Combined with previous single nucleotide polymorphism (SNP) in the TaGS5-A1 exon sequence, four genotypes were formed at the TaGS5-A1 locus and were designated as TaGS5-A1a-a, TaGS5-A1a-b, TaGS5-A1b-a, and TaGS5-A1b-b, respectively. Analysis of the association of TaGS5-A1 alleles with agronomic traits indicated that cultivars with the TaGS5-A1a-b allele possessed significantly higher thousand-kernel weight (TKW) and lower plant height than cultivars with the TaGS5-A1a-a allele, and cultivars with the TaGS5-A1b-b allele showed higher TKW than cultivars with the TaGS5-A1b-a allele. The differences of these traits between the TaGS5-A1a-a and TaGS5-A1a-b alleles were larger than those of the TaGS5-A1b-a and TaGS5-A1b-b alleles, suggesting that the -1925G insertion plays the more important role in TaGS5-A1a genotypes than in TaGS5-A1b genotypes. qRT-PCR indicated that TaGS5-A1b-b possessed the significantly highest expression level among four TaGS5-A1 haplotypes in mature seeds and further showed a significantly higher expression level than TaGS5-A1b-a at five different developmental stages of the seeds, suggesting that high expression of TaGS5-A1 was positively associated with high TKW in bread wheat. This study could provide a relatively superior genotype in view of TKW in wheat breeding programs and could also provide important information for dissection of the regulatory mechanism of the yield-related traits. PMID:27375643

  5. The effect of Ta interface on the crystallization of amorphous phase change material thin films

    SciTech Connect

    Ghezzi, G. E.; Noé, P. Marra, M.; Sabbione, C.; Fillot, F.; Bernier, N.; Ferrand, J.; Maîtrejean, S.; Hippert, F.

    2014-06-02

    The crystallization of amorphous GeTe and Ge{sub 2}Sb{sub 2}Te{sub 5} phase change material films, with thickness between 10 and 100 nm, sandwiched between either Ta or SiO{sub 2} layers, was investigated by optical reflectivity. Ta cladding layers were found to increase the crystallization temperature, even for films as thick as 100 nm. X-Ray diffraction investigations of crystallized GeTe films showed a very weak texture in Ta cladded films, in contrast with the strong texture observed for SiO{sub 2} cladding layers. This study shows that crystallization mechanism of phase change materials can be highly impacted by interface effects, even for relatively thick films.

  6. Underground search for the decay of {sup 180}Ta{sup m}

    SciTech Connect

    Hult, Mikael; Gasparro, Joeel; Marissens, Gerd; Lindahl, Patric; Waetjen, Uwe; Johnston, Peter N.; Wagemans, Cyriel; Koehler, Matthias

    2006-11-15

    Tantalum-180m is a very rare primordial isotope and is not in its nuclear ground state. The radioactivity of {sup 180}Ta{sup m} has not yet been observed. Previous attempts to measure the half-life of {sup 180}Ta{sup m} have been performed using various detectors located above ground. In this work a 606 g Ta disk of natural isotopic composition was measured for 170 d in the 225 m deep underground laboratory HADES. The new lower bound for the half-life is 1.7x10{sup 16} y for electron capture decay and 1.2x10{sup 16} y for {beta}{sup -} decay. This gives a total lower bound for the half-life of 7.1x10{sup 15} y, which is a factor of 6 higher than the previous lower bound.

  7. Crystal growth, VTE treatment, and characterizations of Nd-doped LiTaO3

    NASA Astrophysics Data System (ADS)

    Wu, C. C.; Hsu, W. T.; Chen, Z. B.; Choubey, R. K.; Lan, C. W.

    2011-03-01

    Congruent 0.2 and 0.5 mol% Nd-doped LiTaO3 single crystals were grown by the conventional Czochralski technique. Near-stoichiometric lithium-tantalate wafers were also produced from these crystals by the vapor-transport equilibration (VTE) process. The crystals were characterized by the measurements of composition (by inductively coupled plasma atomic emission spectroscopy (ICP-AES)), UV absorption edge, Curie temperature, and thermal diffusivity. From the ICP-AES study, we found that Li/Ta ratio increased by the VTE treatment, while Nd/Ta ratio was found to decrease with crystal length. Blue-shift in the absorption edge was observed in the VTE treated crystals as compared with the congruent ones. The Curie temperature decreased with increasing Nd concentration, while thermal diffusivity was found to increase after the VTE treatment.

  8. Large magnetoresistance in compensated semimetals TaAs2 and NbAs2

    NASA Astrophysics Data System (ADS)

    Yuan, Zhujun; Lu, Hong; Liu, Yongjie; Wang, Junfeng; Jia, Shuang

    2016-05-01

    We report large magnetoresistance (MR) at low temperatures in single-crystalline nonmagnetic compounds TaAs2 and NbAs2. Both compounds exhibit parabolic-field-dependent MR larger than 5 ×103 in a magnetic field of 9 Tesla at 2 K. The MR starts to deviate from parabolic dependence above 10 T and intends to be saturated in 45 T for TaAs2 at 4.2 K. The Hall resistance measurements and band structure calculations reveal their compensated semimetal characteristics. Their large MR at low temperatures is ascribed to an effect for compensation of electrons and holes with large mobilities. After discussing the MR for different samples of TaAs2 and other semimetals, we found that the magnitudes of MR are strongly dependent on the samples' quality for different compounds.

  9. Genome sequence of the clover-nodulating Rhizobium leguminosarum bv. trifolii strain TA1

    PubMed Central

    Reeve, Wayne; Tian, Rui; De Meyer, Sofie; Melino, Vanessa; Terpolilli, Jason; Ardley, Julie; Tiwari, Ravi; Howieson, John; Yates, Ronald; O’Hara, Graham; Ninawi, Mohamed; Teshima, Hazuki; Bruce, David; Detter, Chris; Tapia, Roxanne; Han, Cliff; Wei, Chia-Lin; Huntemann, Marcel; Han, James; Chen, I-Min; Mavromatis, Konstantinos; Markowitz, Victor; Ivanova, Natalia; Ovchinnikova, Galina; Pagani, Ioanna; Pati, Amrita; Goodwin, Lynne; Pitluck, Sam; Woyke, Tanja; Kyrpides, Nikos

    2013-01-01

    Rhizobium leguminosarum bv. trifolii strain TA1 is an aerobic, motile, Gram-negative, non-spore-forming rod that is an effective nitrogen fixing microsymbiont on the perennial clovers originating from Europe and the Mediterranean basin. TA1 however is ineffective with many annual and perennial clovers originating from Africa and America. Here we describe the features of R. leguminosarum bv. trifolii strain TA1, together with genome sequence information and annotation. The 8,618,824 bp high-quality-draft genome is arranged in a 6 scaffold of 32 contigs, contains 8,493 protein-coding genes and 83 RNA-only encoding genes, and is one of 20 rhizobial genomes sequenced as part of the DOE Joint Genome Institute 2010 Community Sequencing Program. PMID:24976881

  10. Possibility of high-energy THz generation in LiTaO3

    NASA Astrophysics Data System (ADS)

    Tokodi, L.; Buzády, A.; Hebling, J.; Pálfalvi, L.

    2016-09-01

    Due to the absence of the detrimental three-photon absorption, LiTaO3 is a promising crystal for terahertz generation when pumping with an 800-nm pump wavelength. The nonlinear optical, photorefractive and dielectric (except the bandwidth) properties at the optical and the terahertz wavelength are very similar to those of LiNbO3. The absorption coefficient and refractive index spectra of 1 mol% Mg-doped stoichiometric LiTaO3 measured by terahertz time domain spectroscopy are presented. Optimization calculations have been performed, and results for a hybrid-type high-energy terahertz source using LiTaO3 are presented. About 90 % diffraction efficiency is predicted with a practically feasible contact grating.

  11. Microscopic quantum interference in excitonic condensation of Ta2NiSe5

    NASA Astrophysics Data System (ADS)

    Sugimoto, Koudai; Kaneko, Tatsuya; Ohta, Yukinori

    2016-01-01

    The microscopic quantum interference associated with excitonic condensation in Ta2NiSe5 is studied in a BCS-type mean-field approximation. We show that in ultrasonic attenuation the coherence peak appears just below the transition temperature Tc, whereas in NMR spin-lattice relaxation the rate rapidly decreases below Tc; these observations can offer a crucial experimental test for the validity of the excitonic condensation scenario in Ta2NiSe5 . We also show that excitonic condensation manifests itself in a jump of the heat capacity at Tc as well as in a softening of the elastic shear constant, in accordance with the second-order phase transition observed in Ta2NiSe5 .

  12. Tetrahedral Amorphous Carbon (ta-C) Ultra Thin Films for Slider Overcoat Application

    NASA Astrophysics Data System (ADS)

    Shi, X.; Hu, Y. H.; Hu, L.

    Tetrahedral Amorphous Carbon (ta-C) thin film by using Filtered Cathodic Vacuum Arc (FCVA) technique has proven to be wear-resistive and corrosion resistant for a wide range of electrical, optical, and mechanical applications. Many investigations have shown that the ta-C film prepared by the FCVA technique can provide a superior ultra thin overcoat for the sliders and media compared to ECR-CVD and IBD coating technology. The ta-C film excels in terms of the film density, hardness, surface roughness and corrosion resistance. Nanofilm Technology International (NTI) has successfully developed and commercialized the FCVA coating system (FS series) for the slider overcoat application, which provides a good quality film with a high hardness (~50 GPa), low stress (2~3 GPa), low macro-particle density (~1/cm2 for particles > 0.3 μm), good uniformity (< 4%$ in 8 inch coating area) and high production repeatability (< 5%).

  13. Blistering and cracking of LiTaO3 single crystal under helium ion implantation

    NASA Astrophysics Data System (ADS)

    Ma, Changdong; Lu, Fei; Ma, Yujie

    2015-03-01

    Blistering and cracking in LiTaO3 surface are investigated after 200-keV helium ion implantation and subsequent post-implantation annealing. Rutherford backscattering/channeling is used to examine the lattice damage caused by ion implantation. Blistering is observed through optical microscopy in a dynamic heating process. Atomic force microscopy and scanning electron microscopy measurements are used to detect the LiTaO3 surface morphology. Experimental results show that blistering and flaking are dependent on implantation fluence, beam current, and also annealing temperature. We speculate that the surface cracking of He+-implanted LiTaO3 results from the implantation-induced stress and compression.

  14. 3D Ta/TaO x /TiO2/Ti synaptic array and linearity tuning of weight update for hardware neural network applications

    NASA Astrophysics Data System (ADS)

    Wang, I.-Ting; Chang, Chih-Cheng; Chiu, Li-Wen; Chou, Teyuh; Hou, Tuo-Hung

    2016-09-01

    The implementation of highly anticipated hardware neural networks (HNNs) hinges largely on the successful development of a low-power, high-density, and reliable analog electronic synaptic array. In this study, we demonstrate a two-layer Ta/TaO x /TiO2/Ti cross-point synaptic array that emulates the high-density three-dimensional network architecture of human brains. Excellent uniformity and reproducibility among intralayer and interlayer cells were realized. Moreover, at least 50 analog synaptic weight states could be precisely controlled with minimal drifting during a cycling endurance test of 5000 training pulses at an operating voltage of 3 V. We also propose a new state-independent bipolar-pulse-training scheme to improve the linearity of weight updates. The improved linearity considerably enhances the fault tolerance of HNNs, thus improving the training accuracy.

  15. Mechanical Failure of Thin Ta and Cu/Ta Layers on Polyimide Substrates: A Synchrotron-Based Technique for In Situ Characterization

    SciTech Connect

    Frank, Stephan; Olliges, Sven; Spolenak, Ralph; Handge, Ulrich A.

    2009-06-18

    In situ synchrotron radiation diffraction and confocal light microscopy is used to study fragmentation and buckling of thin brittle Ta layers with thicknesses of 50 nm, 100 nm and 200 nm on polyimide substrates. Synchrotron-based stress measurements confirm that cracking leads to relaxation of tensile stress. Simultaneously, compressive stress arises in transverse direction, which finally leads to buckling. This behavior can be explained quantitatively by a two-dimensional shear lag model. It is well established that the properties of the coating-substrate interface determine the processes of coating fragmentation and delamination. A possible approach for influencing and controlling these processes is given by the incorporation of a ductile interlayer. It can be observed that the presence of Cu interlayers with thicknesses of 5 nm, 20 nm and 50 nm reduces the fracture strength of brittle Ta coatings on polyimide substrates, whereas the resistance to buckling is increased significantly.

  16. [The mutagenic action of radioactive contaminants of feed and food products on strains TA98 and TA100 of Salmonella typhimurium].

    PubMed

    Matseliukh, B P; Lavrinchuk, V Ia; Bambura, O I; Kopiĭko, O P

    1996-01-01

    Radionuclide-polluted slices of beef (2775 Bq/kg), pork (274.8 Bq/kg), potato (159.0-444.0 Bq/kg), carrot, garden beet, kidney bean and sorrel (44.5-460.0 Bq/kg) have been studied for their mutagenic effect on the tester strains TA98 and TA100 of Salmonella typhimurium and this index as a rule correlates with the level of the slices pollution. On the other hand the slices of cabbage and samples of rye and wheat (46.0-460.0 Bq/kg) as well as fish (2314.0 Bq/kg) had no mutagenic effect on these strains. The samples of milk (230.0-581.5 Bq/1) also did not evoke the increase of mutagenesis level while high concentrations of these preparations (20 mg/ml, and above) manifested toxic effect on the mentioned strains.

  17. 3D Ta/TaO x /TiO2/Ti synaptic array and linearity tuning of weight update for hardware neural network applications.

    PubMed

    Wang, I-Ting; Chang, Chih-Cheng; Chiu, Li-Wen; Chou, Teyuh; Hou, Tuo-Hung

    2016-09-01

    The implementation of highly anticipated hardware neural networks (HNNs) hinges largely on the successful development of a low-power, high-density, and reliable analog electronic synaptic array. In this study, we demonstrate a two-layer Ta/TaO x /TiO2/Ti cross-point synaptic array that emulates the high-density three-dimensional network architecture of human brains. Excellent uniformity and reproducibility among intralayer and interlayer cells were realized. Moreover, at least 50 analog synaptic weight states could be precisely controlled with minimal drifting during a cycling endurance test of 5000 training pulses at an operating voltage of 3 V. We also propose a new state-independent bipolar-pulse-training scheme to improve the linearity of weight updates. The improved linearity considerably enhances the fault tolerance of HNNs, thus improving the training accuracy. PMID:27483492

  18. Impact of total ionizing dose irradiation on Pt/SrBi{sub 2}Ta{sub 2}O{sub 9}/HfTaO/Si memory capacitors

    SciTech Connect

    Yan, S. A.; Tang, M. H. E-mail: lizheng@xtu.edu.cn; Xiao, Y. G.; Zhang, W. L.; Zhao, W.; Guo, H. X.; Xiong, Y.; Li, Z. E-mail: lizheng@xtu.edu.cn; Ding, H.; Chen, J. W.; Zhou, Y. C.

    2015-01-05

    In this work, metal-ferroelectric-insulator-semiconductor (MFIS) structure capacitors with SrBi{sub 2}Ta{sub 2}O{sub 9} (300 nm) as ferroelectric thin film and HfTaO (6 nm, 8 nm, 10 nm, and 12 nm) as insulating buffer layer were proposed and investigated. The prepared capacitors were fabricated and characterized before radiation and then subjected to {sup 60}Co gamma irradiation in steps of two dose levels. Significant irradiation-induced degradation of the electrical characteristics was observed. The radiation experimental results indicated that stability and reliability of as-fabricated MFIS capacitors for nonvolatile memory applications could become uncontrollable under strong irradiation dose and/or long irradiation time.

  19. Mechanical Failure of Thin Ta and Cu/Ta Layers on Polyimide Substrates: A Synchrotron-Based Technique for In Situ Characterization

    NASA Astrophysics Data System (ADS)

    Frank, Stephan; Handge, Ulrich A.; Olliges, Sven; Spolenak, Ralph

    2009-06-01

    In situ synchrotron radiation diffraction and confocal light microscopy is used to study fragmentation and buckling of thin brittle Ta layers with thicknesses of 50 nm, 100 nm and 200 nm on polyimide substrates. Synchrotron-based stress measurements confirm that cracking leads to relaxation of tensile stress. Simultaneously, compressive stress arises in transverse direction, which finally leads to buckling. This behavior can be explained quantitatively by a two-dimensional shear lag model. It is well established that the properties of the coating-substrate interface determine the processes of coating fragmentation and delamination. A possible approach for influencing and controlling these processes is given by the incorporation of a ductile interlayer. It can be observed that the presence of Cu interlayers with thicknesses of 5 nm, 20 nm and 50 nm reduces the fracture strength of brittle Ta coatings on polyimide substrates, whereas the resistance to buckling is increased significantly.

  20. [Bioantimutagenic effect of the culture fluid of Streptococcus faecalis on mutagenesis induced by 2-nitrofluorene in Salmonella typhimurium TA 1538 and TA 98].

    PubMed

    Vorob'eva, L I; Cherdyntseva, T A; Abilev, S K

    1996-01-01

    Streptococcus faecalis growing in rich organic media or synthetic medium containing 0.1% trypton and 0.05% yeast extract was shown to form substances with a bioantimutagenic activity against the mutagenicity of 2-nitrofluorene and 4-nitroquinoline-1-oxide, which induce frameshift and base-pair substitution mutations, respectively. The maximum accumulation of antimutagens in the medium was observed within 16-24 h of growth. The modified Ames test showed that the culture liquid of Str. faecalis possessed a higher antimutagenic activity for Salmonella typhimurium strain TA 1538 than for strain TA 98 with an enhanced SOS response. Fractionation of the culture liquid revealed that the bioantimutagenic activity is localized in the fraction of peptides with molecular masses of less than 12 kDa. PMID:8721607

  1. Peculiarities of structure formation of layered metal-oxide system Ti-Ta-(Ti,Ta)xOy during electro-spark alloying and thermally stimulated modification

    NASA Astrophysics Data System (ADS)

    Fomina, Marina A.; Koshuro, Vladimir A.; Fomin, Aleksandr A.; Rodionov, Igor V.; Skaptsov, Aleksandr A.; Zakharevich, Andrey M.; Aman, Alexander; Oseev, Aleksandr; Hirsch, Soeren; Majcherek, Soeren

    2016-04-01

    The study focuses on high-performance combined electro-spark alloying of titanium and titanium alloy (VT1-0, VT16) surface and porous matrix structure oxidation. The metal-oxide coatings morphology is the result of melt drop transfer, heat treatment, and oxidation. The study establishes the influence of technological regimes of alloying and oxidation on morphological heterogeneity of biocompatible layered metal-oxide system Ti-Ta-(Ti,Ta)xOy. It was found that during electro-spark alloying the concentration of tantalum on the titanium surface ranges from 0.1 to 3.2 at.%. Morphology of the deposited splats is represented by uniformly grown crystals of titanium and tantalum oxides, which increase from nano- to submicron size.

  2. Growth of single crystalline TaON on yttria-stabilized zirconia (YSZ)

    SciTech Connect

    Tao, Junguang Chai, J.W.; Wong, L.M.; Zhang, Z.; Pan, J.S.; Wang, S.J.

    2013-08-15

    Owing to its high stability in aqueous solution and high quantum efficiency, tantalum based oxyntride (TaON) has attracted increasing attentions for application as visible light photocatalyst. However, despite the recent progress in photocatalytic studies, its bulk charge transport mechanisms are yet to be discovered because of the lack of single crystal sample. In this paper, high quality single crystalline TaON(100) thin film was prepared on cubic YSZ(100) surface by reactive RF magnetron sputtering to avail the understandings of charge transport mechanism so as to improve the device efficiency. The stoichiometry, crystal phase and structure were examined in situ by x-ray photoelectron spectroscopy (XPS) and ex situ by x-ray diffraction (XRD) and transmission electron microscopy (TEM). The TaON film crystallizes in monoclinic β-phase with its [010]/[001] directions aligned to those of the substrate. The small band gap of 2.5 eV as well as the high structure perfection suggests better performance for visible light water splitting. The method can be used to prepare other surface orientations to elucidate fundamental surface structure dependent photoactivities. - Graphical abstract: Structure of single crystalline β-TaON and its diffraction pole figure. Highlights: • High quality single crystal TaON(100) thin film were grown on YSZ(100) surface. • β-phase monoclinic TaON film is formed. • Its [010]/[001] directions are aligned to those of the substrate. • The small band gap and structure perfection suggest visible light photo-activity.

  3. The Relationship Between Anaphor Features and Antecedent Retrieval: Comparing Mandarin Ziji and Ta-Ziji

    PubMed Central

    Dillon, Brian; Chow, Wing-Yee; Xiang, Ming

    2016-01-01

    In the present study we report two self-paced reading experiments that investigate antecedent retrieval processes in sentence comprehension by contrasting the real-time processing behavior of two different reflexive anaphors in Mandarin Chinese. Previous work has suggested that comprehenders initially evaluate the fit between the morphologically simple long-distance reflexive “ziji” and the closest available subject position, only subsequently considering more structurally distant antecedents (Gao et al., 2005; Liu, 2009; Li and Zhou, 2010; Dillon et al., 2014; cf. Chen et al., 2012). In this paper, we investigate whether this locality bias effect obtains for other reflexive anaphors in Mandarin Chinese, or if it is associated specifically with the morphologically simple reflexive ziji. We do this by comparing the processing of ziji to the processing of the morphologically complex reflexive ta-ziji (lit. s/he-self). In Experiment 1, we investigate the processing of ziji, and replicate the finding of a strong locality bias effect for ziji in self-paced reading measures. In Experiment 2, we investigate the processing of the morphologically complex reflexive ta-ziji in the same structural configurations as Experiment 1. A comparison of our experiments reveals that ta-ziji shows a significantly weaker locality bias effect than ziji does. We propose that this results from the difference in the number of morphological and semantic features on the anaphor ta-ziji relative to ziji. Specifically, we propose that the additional retrieval cues associated with ta-ziji reduce interference from irrelevant representations in memory, allowing it to more reliably access an antecedent regardless its linear or structural distance. This reduced interference in turn leads to a diminished locality bias effect for the morphologically complex anaphor ta-ziji. PMID:26779079

  4. Intersectional Gene Expression in Zebrafish Using the Split KalTA4 System.

    PubMed

    Almeida, Rafael Gois; Lyons, David Anthony

    2015-12-01

    In this study, we describe the adaptation of the split Gal4 system for zebrafish. The Gal4-UAS system is widely used for expression of genes-of-interest by crossing driver lines expressing the transcription factor Gal4 (under the control of the promoter of interest) with reporter lines where upstream activating sequence (UAS) repeats (recognized by Gal4) drive expression of the genes-of-interest. In the Split Gal4 system, hemi-drivers separately encode the DNA-binding domain (DBD) and the activation domain (AD) of Gal4. When encoded under two different promoters, only those cells in the intersection of the promoters' expression pattern and in which both promoters are active reconstitute a functional Gal4 and activate expression from a UAS-driven transgene. We split the zebrafish-optimized version of Gal4, KalTA4, and generated a hemi-driver encoding the KalTA4 DBD and a hemi-driver encoding KalTA4's AD. We show that split KalTA4 domains can assemble in vivo and transactivate a UAS reporter transgene and that each hemi-driver alone cannot transactivate the reporter. Also, transactivation can happen in several cell types, with similar efficiency to intact KalTA4. Finally, in transient mosaic expression assays, we show that when hemi-drivers are preceded by two distinct promoters, they restrict the expression of an UAS-driven reporter from a broader pattern (sox10) to its constituent smaller neuronal pattern. The Split KalTA4 system should be useful for expression of genes-of-interest in an intersectional manner, allowing for more refined manipulations of cell populations in zebrafish.

  5. Intersectional Gene Expression in Zebrafish Using the Split KalTA4 System

    PubMed Central

    2015-01-01

    Abstract In this study, we describe the adaptation of the split Gal4 system for zebrafish. The Gal4-UAS system is widely used for expression of genes-of-interest by crossing driver lines expressing the transcription factor Gal4 (under the control of the promoter of interest) with reporter lines where upstream activating sequence (UAS) repeats (recognized by Gal4) drive expression of the genes-of-interest. In the Split Gal4 system, hemi-drivers separately encode the DNA-binding domain (DBD) and the activation domain (AD) of Gal4. When encoded under two different promoters, only those cells in the intersection of the promoters' expression pattern and in which both promoters are active reconstitute a functional Gal4 and activate expression from a UAS-driven transgene. We split the zebrafish-optimized version of Gal4, KalTA4, and generated a hemi-driver encoding the KalTA4 DBD and a hemi-driver encoding KalTA4's AD. We show that split KalTA4 domains can assemble in vivo and transactivate a UAS reporter transgene and that each hemi-driver alone cannot transactivate the reporter. Also, transactivation can happen in several cell types, with similar efficiency to intact KalTA4. Finally, in transient mosaic expression assays, we show that when hemi-drivers are preceded by two distinct promoters, they restrict the expression of an UAS-driven reporter from a broader pattern (sox10) to its constituent smaller neuronal pattern. The Split KalTA4 system should be useful for expression of genes-of-interest in an intersectional manner, allowing for more refined manipulations of cell populations in zebrafish. PMID:26485616

  6. Second order incommensurate phase transition in 25L-Ta{sub 2}O{sub 5}

    SciTech Connect

    Audier, M.; Chenevier, B.; Roussel, H.; Lintanf Salauen, A.

    2010-09-15

    A new structural state 25L-Ta{sub 2}O{sub 5}, obtained from sintering and annealing treatments of a Ta{sub 2}O{sub 5} powder, is identified both by electron diffraction and high resolution imaging on a transmission electron microscope (TEM). According to general rules for the different L-Ta{sub 2}O{sub 5} structures proposed by Grey et al. (J. Solid State Chem. 178 (2005) 3308), a structural model is derived from their crystallographic data on 19L-Ta{sub 2}O{sub 5}. This model yields simulated images in agreement with high resolution TEM observations of the structure oriented along its [001] zone axis, but only for a very thin crystal thickness of less than 1.2 nm. Such a limitation is shown to be due to a modulation of the structure along its [001] axis. Actually, from an analysis of a diffuse scattering and of its evolution into satellites reflections as a function of the cooling rate, a second order incommensurate phase transition can be assumed to occur in this compound. The property of single phase samples observed by TEM is also verified by X-ray powder diffraction. In a discussion about studies performed by different authors on incommensurate structures in the system Ta{sub 2}O{sub 5}-WO{sub 3}, it is noticed that TEM results, similar to ours, indicate that phase transitions could be expected in these structures. - Graphical Abstract: Electron diffraction patterns of [100] zone axis, showing a structural change of the 25L-Ta{sub 2}O{sub 5} phase through a variation of the cooling rate from 1000 {sup o}C.

  7. Nb-Ta fractionation in hydrothermal magnetite: implications for the "missing Nb" paradox

    NASA Astrophysics Data System (ADS)

    Shuo, Y.; Changqian, M.

    2015-12-01

    The subchondritic Nb/Ta ratios in continental crust and depleted mantle require complementary reservoirs to balance the deficit Nb observed in most terrestrial silicate reservoirs. In this work, we provide textural and in-situ trace elemental data of magnetite from Baishiya iron deposit, East Kunlun Orogenic Belt, Northern Tibet Plateau to constrain the Nb-Ta fractionation in hydrothermal magnetite, a potential mineral to explain the missing Nb paradox. Four stages of mineralization and alteration have been identified based on field work and petrography study: iron skarnization, hydrothermal alteration, metasomatic carbonatation and quartz-sulfide mineralization. Back scattering images reveal that magnetite in iron skarnization stage develops obvious oscillatory zonation patterns, whereas those formed in the hydrothermal alteration and metasomatic carbonatation stages display metasomatic texture, and those in sulfide mineralization stage develops euhedral zoned texture. Corresponding to the textural signatures, systematic variation of trace elements is also observed in their trace element concentration which is related to the efficient factors during fluid-rock interaction. Therefore, some factors on Nb-Ta fractionation could be excluded through their variation with the Nb/Ta ratios. Above it all, a negative exclusively correlation of Nb/Ta (0.55-27) and the content of V and Ni, are considered to be key elements due to their siderophile and chalcophile affinity respectively. It confirms that increased oxygen and sulfur fugacity are primary factors that controlled Nb/Ta fractionation in hydrothermal magnetite. Similarly, the band iron formations with huge amounts of magnetites in subduction process presumably carried off mass Nb from the mantle due to the dehydration of the oceanic crust and fluid-rock interaction subsequently. We contend that the BIFs in deep mantle may be a potential complementary reservoir that has been overlooked before.

  8. Voltage divider effect for the improvement of variability and endurance of TaOx memristor

    NASA Astrophysics Data System (ADS)

    Kim, Kyung Min; Yang, J. Joshua; Strachan, John Paul; Grafals, Emmanuelle Merced; Ge, Ning; Melendez, Noraica Davila; Li, Zhiyong; Williams, R. Stanley

    2016-02-01

    The impact of a series resistor (RS) on the variability and endurance performance of memristor was studied in the TaOx memristive system. A dynamic voltage divider between the RS and memristor during both the set and the reset switching cycles can suppress the inherent irregularity of the voltage dropped on the memristor, resulting in a greatly reduced switching variability. By selecting the proper resistance value of RS for the set and reset cycles respectively, we observed a dramatically improved endurance of the TaOx memristor. Such a voltage divider effect can thus be critical for the memristor applications that require low variability, high endurance and fast speed.

  9. Crystal structures and phase transitions in Ba{sub 2}HoTaO{sub 6}

    SciTech Connect

    Kennedy, Brendan J. Saines, Paul J.; Kubota, Yoshiki; Minakata, Chiharu; Hano, Hiroko; Kato, Kenichi; Takata, Masaki

    2007-11-06

    The structure of the cation-ordered double perovskite Ba{sub 2}HoTaO{sub 6} was examined using synchrotron X-ray powder diffraction at fine temperature intervals over the range of 90-300 K. Ba{sub 2}HoTaO{sub 6} has a cubic structure in space group Fm3-barm at room temperature. A proper ferroelastic phase transition to I4/m tetragonal symmetry occurs near approximately 260 K. Analysis of the spontaneous tetragonal strain versus temperature indicated that the phase transition is second order in nature.

  10. Ferroelectric inversion layers formed by heat treatment of proton-exchanged LiTaO3

    NASA Astrophysics Data System (ADS)

    Nakamura, Kiyoshi; Shimizu, Hiroshi

    1990-04-01

    We report that a ferroelectric inversion layer can be formed in LiTaO3 by proton exchange in benzoic acid melts followed by heat treatment at temperatures just below the Curie point. It is demonstrated that the inversion layer appears at the -c surface for LiTaO3, whereas it appears at the +c surface for LiNbO3. The dependence of the inversion layer thickness on the conditions of proton exchange and heat treatment is also reported.

  11. High-pressure crystal structures of TaAs from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Lu, Mingchun; Guo, Yanan; Zhang, Miao; Liu, Hanyu; Tse, John S.

    2016-08-01

    In this work, we systematically studied the phase transition of TaAs under high pressures and reported three high-pressure structures P-6m2 (hexagonal, stable at 13-32 GPa), P21/c (monoclinic, stable at 32-103 GPa) and Pm-3m (cubic, stable above 103 GPa), by using particle swarm optimization in combination with first principles electronic structure methodology. All predicted structures are dynamically stable, since there is no imaginary mode to be found in the whole Brillouin zone. At high pressures, the TaAs was found to become superconductor with the superconducting critical temperature of ~1 K at about 100 GPa.

  12. Interaction of 11B with 209Bi and 181Ta targets at intermediate energies

    NASA Astrophysics Data System (ADS)

    Karapetyan, G. S.; Deppman, A.; Guimarães, V.; Balabekyan, A.; Demekhina, N. A.

    2016-08-01

    Production cross sections for nuclei fragments from the interaction of 11B ions with 209Bi and 181Ta targets, in the intermediate energy regime, have been obtained with the induced-activity method and offline γ spectroscopy. The mass-yield distributions were obtained and the fission process was investigated by using the multimodal fission approach in the case of the 209Bi target and a pure symmetric distribution for the 181Ta target. The fissilities were deduced for both targets and further compared to the data for proton-induced reactions. The relative values of the linear momentum imparted to the targets were derived from the cross section data.

  13. Exceptionally long-ranged lattice relaxation in oxygen-deficient Ta2O5

    NASA Astrophysics Data System (ADS)

    Yang, Yong; Sugino, Osamu; Kawazoe, Yoshiyuki

    2014-10-01

    The lattice relaxation in oxygen-deficient Ta2O5 is investigated using first-principles calculations. The presence of a charge-neutral oxygen vacancy can result in a long-ranged lattice relaxation which extends beyond 18 Å from the vacancy site. The lattice relaxation has significant effects on the vacancy formation energy as well as the electronic structures. The long-ranged behavior of the lattice relaxation is explained in terms of the Hellmann-Feynman forces and the potential energy surface related to the variation of Ta-O bond lengths.

  14. Survey of Technologies to Support Reuse of Gloveboxes at LANL TA-55

    SciTech Connect

    L. C. Cadwallader; P. A. Pinson

    1998-11-01

    This report is a summary of ideas and technologies available to support reuse of plutonium gloveboxes at the Los Alamos National Laboratory (LANL) Technical Area 55 (TA-55). This work is the second of two deliverables in the task to enhance glovebox design for longevity and reusability at TA-55. The report presents several design change suggestions to be evaulated for their feasibility by LANL glovebox designers. The report also describes some techniques to be evaluated by LANL for their usefulness in reducing glovebox waste.

  15. Voltage divider effect for the improvement of variability and endurance of TaOx memristor

    PubMed Central

    Kim, Kyung Min; Yang, J. Joshua; Strachan, John Paul; Grafals, Emmanuelle Merced; Ge, Ning; Melendez, Noraica Davila; Li, Zhiyong; Williams, R. Stanley

    2016-01-01

    The impact of a series resistor (RS) on the variability and endurance performance of memristor was studied in the TaOx memristive system. A dynamic voltage divider between the RS and memristor during both the set and the reset switching cycles can suppress the inherent irregularity of the voltage dropped on the memristor, resulting in a greatly reduced switching variability. By selecting the proper resistance value of RS for the set and reset cycles respectively, we observed a dramatically improved endurance of the TaOx memristor. Such a voltage divider effect can thus be critical for the memristor applications that require low variability, high endurance and fast speed. PMID:26830763

  16. Efficient Room-Temperature Activation of Methane by TaN(+) under C-N Coupling.

    PubMed

    Zhou, Shaodong; Li, Jilai; Schlangen, Maria; Schwarz, Helmut

    2016-09-12

    The thermal reaction of diatomic tantalum nitride cation [TaN](+) with methane has been explored using FT-ICR mass spectrometry complemented by high-level quantum chemical calculation; based on this combined experimental/computational approach, mechanistic aspects of this novel, highly efficient C-N coupling process have been uncovered. In distinct contrast to [TaN](+) , its lighter congeners [VN](+) and [NbN](+) are inert towards methane under ambient conditions, and the origins of the remarkably variable efficiencies of the three metal nitrides are uncovered by CCSD(T) calculations. PMID:27510819

  17. Crystalline and electronic structure of single-layer TaS2

    NASA Astrophysics Data System (ADS)

    Sanders, Charlotte E.; Dendzik, Maciej; Ngankeu, Arlette S.; Eich, Andreas; Bruix, Albert; Bianchi, Marco; Miwa, Jill A.; Hammer, Bjørk; Khajetoorians, Alexander A.; Hofmann, Philip

    2016-08-01

    Single-layer TaS2 is epitaxially grown on Au(111) substrates. The resulting two-dimensional crystals adopt the 1 H polymorph. The electronic structure is determined by angle-resolved photoemission spectroscopy and found to be in excellent agreement with density functional theory calculations. The single-layer TaS2 is found to be strongly n doped, with a carrier concentration of 0.3 (1 ) extra electrons per unit cell. No superconducting or charge density wave state is observed by scanning tunneling microscopy at temperatures down to 4.7 K.

  18. Photoelectron Spectroscopy Study of [Ta2B6]-: a Hexagonal Bipyramdial Cluster

    NASA Astrophysics Data System (ADS)

    Jian, Tian; Li, Weili; Romanescu, Constantin; Wang, Lai-Sheng

    2014-06-01

    It has been a long-sought goal in cluster science to discover stable atomic clusters as building blocks for cluster-assembled nanomaterials, as exemplified by the fullerenes and their subsequent bulk syntheses.[1,2] Clusters have also been considered as models to understand bulk properties, providing a bridge between molecular and solid-state chemistry.[3] Herein we report a joint photoelectron spectroscopy and theoretical study on the [Ta2B6]- and [Ta2B6] clusters.[4] The photoelectron spectrum of [Ta2B6]- displays a simple spectral pattern and a large HOMO-LUMO gap, suggesting its high symmetry. Theoretical calculations show that both the neutral and anion are D6h pyramidal. The chemical bonding analyses for [Ta2B6] revealed the nature of the B6 and Ta interactions and uncovered strong covalent bonding between B6 and Ta. The D6h-[TaB6Ta] gaseous cluster is reminiscent of the structural pattern in the ReB6X6Re core in the [(Cp*Re)2B6H4Cl2] and the TiB6Ti motif in the newly synthesized Ti7Rh4Ir2B8 solid-state compound.[5,6] The current work provides an intrinsic link between a gaseous cluster and motifs for solid materials. Continued investigations of the transition-metal boron clusters may lead to the discovery of new structural motifs involving pure boron clusters for the design of novel boride materials. Reference [1] H.W. Kroto, J. R. Heath, S. C. OBrien, R. F. Curl, R. E. Smalley, Nature 1985, 318, 162 - 163. [2] W. Krtschmer, L. D. Lamb, K. Fostiropoulos, D. R. Huffman, Nature 1990, 347, 354 - 358. [3] T. P. Fehlner, J.-F. Halet, J.-Y. Saillard, Molecular Clusters: A Bridge to Solid-State Chemitry, Cambridge University Press, UK, 2007. [4] W. L. Li, L. Xie, T. Jian, C. Romanescu, X. Huang, L.-S. Wang, Angew. Chem. Int. Ed. 2014, 126, 1312 - 1316. [5] B. Le Guennic, H. Jiao, S. Kahlal, J.-Y. Saillard, J.-F. Halet, S. Ghosh, M. Shang, A. M. Beatty, A. L. Rheingold, T. P. Fehlner, J. Am. Chem. Soc. 2004, 126, 3203 - 3217. [6] B. P. T. Fokwa, M. Hermus, Angew

  19. Stratigraphic framework of the upper Fort Union Formation, TA Hills, Western Powder River basin, Wyoming

    USGS Publications Warehouse

    Weaver, Jean N.; Flores, Romeo M.

    1985-01-01

    The purpose of this study is to interpret a relationship between the stratigraphy and the environment of deposition of the upper part of the Fort Union Formation in the TA Hills in the western part of the Powder River Basin, Johnson County, Wyoming.  This framework was used to map and correlate coal beds with those mapped by Hose (1955) and Mapel (1959) in the southern and northern parts of the study area, respectively.  More specifically, the established stratigraphic and environmental relationships of the coal beds and associated rocks contribute to a depositional model for the upper part of the Fort Union Formation in the TA Hills.

  20. Preparation and investigation of the quaternary alloy CuTaInSe{sub 3}

    SciTech Connect

    Grima-Gallardo, P. Munoz, M.; Duran, S.; Delgado, G.E.; Quintero, M.; Ruiz, J.

    2007-12-04

    Polycrystalline samples of the quaternary alloy CuTaInSe{sub 3} were prepared by the usual melt and anneal technique. The analysis of the diffraction pattern indicates a single phase which indexes as a tetragonal chalcopyrite-like structure with lattice parameters a = 5.7837 {+-} 0.0002 A; c = 11.6208 {+-} 0.0007 A and V = 389 {+-} 1 A{sup 3}. Differential thermal analysis shows that the melting transition of CuTaInSe{sub 3} is incongruent with large liquid + solids regions.

  1. Nd:Ta{sub 2}O{sub 5} rib waveguide lasers

    SciTech Connect

    Unal, Bayram; Tai, C.-Y.; Shepherd, David P.; Wilkinson, James S.; Perney, Nicolas M.B.; Netti, M. Caterina; Parker, Gregory J.

    2005-01-10

    Ta{sub 2}O{sub 5} waveguides offer great potential for high-density active photonic crystal circuits and their combination with rare-earth dopants for active devices is of interest for increasing their potential functionality. To this end, neodymium-doped Ta{sub 2}O{sub 5} rib waveguide lasers have been fabricated on an oxidized silicon wafer by rf sputtering and argon ion-beam milling and laser action in this material has been demonstrated. Lasing was observed at wavelenghts between 1060 and 1080 nm and an absorbed pump power threshold of 87 mW was obtained.

  2. Characterization of multi-principal-element (TiZrNbHfTa)N and (TiZrNbHfTa)C coatings for biomedical applications.

    PubMed

    Braic, V; Balaceanu, M; Braic, M; Vladescu, A; Panseri, S; Russo, A

    2012-06-01

    Multi-principal-element (TiZrNbHfTa)N and (TiZrNbHfTa)C coatings were deposited on Ti6Al4V alloy by co-sputtering of Ti, Zr, Nb, Hf and Ta metallic targets in reactive atmosphere. The coatings were analyzed for elemental and phase compositions, crystalline structure, morphology, residual stress, hardness, friction performance, wear-corrosion resistance and cell viability. For all the films, only simple fcc solid solutions with (111) preferred orientations were found, with crystallite sizes in the range 7.2-13.5 nm. The coatings were subjected to compressive stress, with values ranging from 0.8 to 1.6 GPa. The carbide coating with the highest carbon content (carbon/metal ≈1.3) exhibited the highest hardness of about 31 GPa, the best friction behavior (μ = 0.12) and the highest wear resistance (wear rate K=0.2×10(-6)mm(3)N(-1)m(-1)), when testing in simulated body fluids (SBFs). Cell viability tests proved that the osteoblast cells were adherent to the coated substrates, and a very high percentage of live cells were observed on sample surfaces, after 72 h incubation time.

  3. Coevolutionary Dynamics of Rice Blast Resistance Gene Pi-ta and Magnaporthe oryzae Avirulence Gene AVR-Pita 1.

    PubMed

    Jia, Yulin; Zhou, Erxun; Lee, Seonghee; Bianco, Tracy

    2016-07-01

    The Pi-ta gene in rice is effective in preventing infections by Magnaporthe oryzae strains that contain the corresponding avirulence gene, AVR-Pita1. Diverse haplotypes of AVR-Pita1 have been identified from isolates of M. oryzae from rice production areas in the United States and worldwide. DNA sequencing and mapping studies have revealed that AVR-Pita1 is highly unstable, while expression analysis and quantitative resistance loci mapping of the Pi-ta locus revealed complex evolutionary mechanisms of Pi-ta-mediated resistance. Among these studies, several Pi-ta transcripts were identified, most of which are probably derived from alternative splicing and exon skipping, which could produce functional resistance proteins that support a new concept of coevolution of Pi-ta and AVR-Pita1. User-friendly DNA markers for Pi-ta have been developed to support marker-assisted selection, and development of new rice varieties with the Pi-ta markers. Genome-wide association studies revealed a link between Pi-ta-mediated resistance and yield components suggesting that rice has evolved a complicated defense mechanism against the blast fungus. In this review, we detail the current understanding of Pi-ta allelic variation, its linkage with rice productivity, AVR-Pita allelic variation, and the coevolution of Pi-ta and AVR-Pita in Oryza species and M. oryzae populations, respectively. We also review the genetic and molecular basis of Pi-ta and AVR-Pita interaction, and its value in marker-assisted selection and engineering resistance. PMID:27070427

  4. Coevolutionary Dynamics of Rice Blast Resistance Gene Pi-ta and Magnaporthe oryzae Avirulence Gene AVR-Pita 1.

    PubMed

    Jia, Yulin; Zhou, Erxun; Lee, Seonghee; Bianco, Tracy

    2016-07-01

    The Pi-ta gene in rice is effective in preventing infections by Magnaporthe oryzae strains that contain the corresponding avirulence gene, AVR-Pita1. Diverse haplotypes of AVR-Pita1 have been identified from isolates of M. oryzae from rice production areas in the United States and worldwide. DNA sequencing and mapping studies have revealed that AVR-Pita1 is highly unstable, while expression analysis and quantitative resistance loci mapping of the Pi-ta locus revealed complex evolutionary mechanisms of Pi-ta-mediated resistance. Among these studies, several Pi-ta transcripts were identified, most of which are probably derived from alternative splicing and exon skipping, which could produce functional resistance proteins that support a new concept of coevolution of Pi-ta and AVR-Pita1. User-friendly DNA markers for Pi-ta have been developed to support marker-assisted selection, and development of new rice varieties with the Pi-ta markers. Genome-wide association studies revealed a link between Pi-ta-mediated resistance and yield components suggesting that rice has evolved a complicated defense mechanism against the blast fungus. In this review, we detail the current understanding of Pi-ta allelic variation, its linkage with rice productivity, AVR-Pita allelic variation, and the coevolution of Pi-ta and AVR-Pita in Oryza species and M. oryzae populations, respectively. We also review the genetic and molecular basis of Pi-ta and AVR-Pita interaction, and its value in marker-assisted selection and engineering resistance.

  5. Oxidation of TaSi2-Containing ZrB2-SiC Ultra-High Temperature Materials

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Smith, Jim; Levine, Stanley R.; Lorincz, Jonathan; Reigel, Marissa

    2010-01-01

    Hot pressed coupons of composition ZrB2-20 v% SiC-5 v% TaSi2 and ZrB2-20 v% SiC-20 v% TaSi2 were oxidized in stagnant air at temperatures of 1627 and 1927C for one, five and ten 10-minute cycles. The oxidation reactions were characterized by weight change kinetics, x-ray diffraction, and SEM/EDS. Detailed WDS/microprobe quantitative analyses of the oxidation products were conducted for the ZrB2-20 v% SiC-20 v% TaSi2 sample oxidized for five 10-minute cycles at 1927C. Oxidation kinetics and product formation were compared to ZrB2-20 v% SiC with no TaSi2 additions. It was found that the 20 v% TaSi2 composition exhibited improved oxidation resistance relative to the material with no TaSi2 additions at 1627C. However, for exposures at 1927C less oxidation resistance and extensive liquid phase formation were observed compared to the material with no TaSi2 additions. Attempts to limit the liquid phase formation by reducing the TaSi2 content to 5 v% were unsuccessful. In addition, the enhanced oxidation resistance at 1627C due to 20 v% TaSi2 additions was not achieved at the 5 v% addition level. The observed oxidation product evolution is discussed in terms of thermodynamics and phase equilibria for the TaSi2-containing ZrB2-SiC material system. TaSi2-additions to ZrB2-SiC at any level are not recommended for ultra-high temperature (>1900C) applications due to excessive liquid phase formation.

  6. Efficient Visible-Light-Driven Z-Scheme Overall Water Splitting Using a MgTa2O(6-x)N(y)/TaON Heterostructure Photocatalyst for H2 Evolution.

    PubMed

    Chen, Shanshan; Qi, Yu; Hisatomi, Takashi; Ding, Qian; Asai, Tomohiro; Li, Zheng; Ma, Su Su Khine; Zhang, Fuxiang; Domen, Kazunari; Li, Can

    2015-07-13

    An (oxy)nitride-based heterostructure for powdered Z-scheme overall water splitting is presented. Compared with the single MgTa2O(6-x)N(y) or TaON photocatalyst, a MgTa2O(6-x)N(y)/TaON heterostructure fabricated by a simple one-pot nitridation route was demonstrated to effectively suppress the recombination of carriers by efficient spatial charge separation and decreased defect density. By employing Pt-loaded MgTa2O(6-x)N(y)/TaON as a H2-evolving photocatalyst, a Z-scheme overall water splitting system with an apparent quantum efficiency (AQE) of 6.8% at 420 nm was constructed (PtO(x)-WO3 and IO3(-)/I(-) pairs were used as an O2-evolving photocatalyst and a redox mediator, respectively), the activity of which is circa 7 or 360 times of that using Pt-TaON or Pt-MgTa2O(6-x)N)y) as a H2-evolving photocatalyst, respectively. To the best of our knowledge, this is the highest AQE among the powdered Z-scheme overall water splitting systems ever reported. PMID:26037473

  7. Efficient Visible-Light-Driven Z-Scheme Overall Water Splitting Using a MgTa2O(6-x)N(y)/TaON Heterostructure Photocatalyst for H2 Evolution.

    PubMed

    Chen, Shanshan; Qi, Yu; Hisatomi, Takashi; Ding, Qian; Asai, Tomohiro; Li, Zheng; Ma, Su Su Khine; Zhang, Fuxiang; Domen, Kazunari; Li, Can

    2015-07-13

    An (oxy)nitride-based heterostructure for powdered Z-scheme overall water splitting is presented. Compared with the single MgTa2O(6-x)N(y) or TaON photocatalyst, a MgTa2O(6-x)N(y)/TaON heterostructure fabricated by a simple one-pot nitridation route was demonstrated to effectively suppress the recombination of carriers by efficient spatial charge separation and decreased defect density. By employing Pt-loaded MgTa2O(6-x)N(y)/TaON as a H2-evolving photocatalyst, a Z-scheme overall water splitting system with an apparent quantum efficiency (AQE) of 6.8% at 420 nm was constructed (PtO(x)-WO3 and IO3(-)/I(-) pairs were used as an O2-evolving photocatalyst and a redox mediator, respectively), the activity of which is circa 7 or 360 times of that using Pt-TaON or Pt-MgTa2O(6-x)N)y) as a H2-evolving photocatalyst, respectively. To the best of our knowledge, this is the highest AQE among the powdered Z-scheme overall water splitting systems ever reported.

  8. Structural and dielectric properties of Sr3(MgTa2)O9 and Sr3(ZnTa2)O9

    NASA Astrophysics Data System (ADS)

    Hoque, Md. M.; Dutta, Alo; Kumar, S.; Sinha, T. P.

    2015-07-01

    Herein, we report the crystal structures and morphological properties of Sr3(MgTa2)O9 (SMT) and Sr3(ZnTa2)O9 (SZT) synthesized by solid state ceramic method along with the results of alternating current impedance spectroscopic (ACIS) study in a frequency range from 50 Hz to 1 MHz at selective temperatures between 393 and 573 K. The crystal structures of SMT and SZT have been determined by Rietveld refinement of powder X-ray diffraction pattern using an initial structural model developed on the basis of literature survey. The results indicate that both the samples possess hexagonal structure of trigonal P 3 bar m 1 space group. The lattice parameters of SMT are a=b=5.65162 Å, c=6.94440 Å, α=β=90° and γ=120° and those of SZT are a=b=5.65832 Å, c=6.95911 Å and α=β=90° and γ=120°. SMT and SZT are isostructural and they exhibit 2:1 B site ordering with the staking sequence of {-Ta-Ta-Mg (Zn)-} (Mg for SMT and Zn for SZT) layer repeat on (111) plane of the pseudocells. The characteristic vibrational bands due to Ta-O, Mg-O and Zn-O bonds have been observed in the FTIR spectra of the samples. The FESEM micrographs of the samples show that the grains size ranges between 0.40 and 3.65 μm and 0.9 to 4.2 μm for SMT and SZT, respectively. To account for the polydispersive nature of the dielectric relaxation mechanism along with the effects of dc conductivity and localized space charges the variation of real (ε‧) and imaginary (ε″) parts of dielectric constant with frequency has been analytically interpreted in the framework of modified Cole-Cole model. SMT and SZT having the activation energies of 0.35 eV and 0.33 eV, respectively (obtained from the Arrhenius plot of dc conductivity), are semiconducting in nature. The electrical current conduction in the samples occurs by polaron hopping process. Further, we have shown that chemical property of A site cations has significant role in determining the dielectric properties of A3B‧B″2O9 type perovskites

  9. Nano suboxide layer generated in Ta{sub 2}O{sub 5} by Ar{sup +} ion irradiation

    SciTech Connect

    Song, W. D. E-mail: ying-ji-feng@dsi.a-star.edu.sg; Ying, J. F. E-mail: ying-ji-feng@dsi.a-star.edu.sg; He, W.; Zhuo, V. Y.-Q.; Ji, R.; Xie, H. Q.; Ng, S. K.; Ng, Serene L. G.; Jiang, Y.

    2015-01-19

    Ta{sub 2}O{sub 5}/TaO{sub x} heterostructure has become a leading oxide layer in memory cells and/or a bidirectional selector for resistive random access memory (RRAM). Although atomic layer deposition (ALD) was found to be uniquely suitable for depositing uniform and conformal films on complex topographies, it is hard to use ALD to grow suboxide TaO{sub x} layer. In this study, tantalum oxide films with a composition of Ta{sub 2}O{sub 5} were grown by ALD. Using Ar{sup +} ion irradiation, the suboxide was formed in the top layer of Ta{sub 2}O{sub 5} films by observing the Ta core level shift toward lower binding energy with angle-resolved X-ray photoelectron spectroscopy. By controlling the energy and irradiation time of an Ar{sup +} ion beam, Ta{sub 2}O{sub 5}/TaO{sub x} heterostructure can be reliably produced on ALD films, which provides a way to fabricate the critical switching layers of RRAM.

  10. The wheat calcium-dependent protein kinase TaCPK7-D positively regulates host resistance to sharp eyespot disease.

    PubMed

    Wei, Xuening; Shen, Fangdi; Hong, Yantao; Rong, Wei; Du, Lipu; Liu, Xin; Xu, Huijun; Ma, Lingjian; Zhang, Zengyan

    2016-10-01

    Sharp eyespot, caused mainly by the necrotrophic fungus Rhizoctonia cerealis, limits wheat production worldwide. Here, TaCPK7-D, encoding a subgroup III member of the calcium-dependent protein kinase (CPK) family, was identified from the sharp eyespot-resistant wheat line CI12633 through comparative transcriptomic analysis. Subsequently, the defence role of TaCPK7-D against R. cerealis infection was studied by the generation and characterization of TaCPK7-D-silenced and TaCPK7-D-overexpressing wheat plants. Rhizoctonia cerealis inoculation induced a higher transcriptional level of TaCPK7-D in the resistant wheat line CI12633 than in the susceptible cultivar Wenmai 6. The expression of TaCPK7-D was significantly induced after exogenous application of 1-aminocyclopropane-1-carboxylic acid (an ethylene biosynthesis precursor). The green fluorescent protein signal distribution assays indicated that TaCPK7-D localizes to the plasma membrane in both onion epidermal cells and wheat protoplasts. Following R. cerealis inoculation, TaCPK7-D-silenced wheat CI12633 plants displayed more severe sharp eyespot symptoms than control CI12633 plants. Four defence-associated genes (β-1,3-glucanase, chitinase 1, defensin and TaPIE1) and an ethylene biosynthesis key gene, ACO2, were significantly suppressed in the TaCPK7-D-silenced wheat plants compared with control plants. Conversely, TaCPK7-D-overexpressing wheat lines showed increased resistance to sharp eyespot compared with untransformed recipient wheat Yangmai 16. Furthermore, the transcriptional levels of these four defence-related genes and ACO2 gene were significantly elevated in TaCPK7-D-overexpressing plants compared with untransformed recipient wheat plants. These results suggest that TaCPK7-D positively regulates the wheat resistance response to R. cerealis infection through the modulation of the expression of these defence-associated genes, and that TaCPK7-D is a candidate to improve sharp eyespot resistance in wheat.

  11. Superconductivity in Ta3Pd3Te14 with quasi-one-dimensional PdTe2 chains.

    PubMed

    Jiao, Wen-He; He, Lan-Po; Liu, Yi; Xu, Xiao-Feng; Li, Yu-Ke; Zhang, Chu-Hang; Zhou, Nan; Xu, Zhu-An; Li, Shi-Yan; Cao, Guang-Han

    2016-02-15

    We report bulk superconductivity at 1.0 K in a low-dimensional ternary telluride Ta3Pd3Te14 containing edge-sharing PdTe2 chains along crystallographic b axis, similar to the recently discovered superconductor Ta4Pd3Te16. The electronic heat capacity data show an obvious anomaly at the transition temperature, which indicates bulk superconductivity. The specific-heat jump is ΔC/(γ(n)T(c)) ≈ 1.35, suggesting a weak coupling scenario. By measuring the low-temperature thermal conductivity, we conclude that Ta3Pd3Te14 is very likely a dirty s-wave superconductor. The emergence of superconductivity in Ta3Pd3Te14 with a lower T(c), compared to that of Ta4Pd3Te16, may be attributed to the lower density of states.

  12. Enhanced performance of dye-sensitized solar cells based on P25/Ta2O5 composite films

    NASA Astrophysics Data System (ADS)

    Jiang, Qingsong; Gao, Jian; Yi, Lin; Hu, Guang; Zhang, Jun

    2016-04-01

    In this paper, novel titanium dioxide/tantalum pentoxide (P25/Ta2O5) composite films have been successfully fabricated and applied to dye-sensitized solar cells (DSSCs). Ta2O5 nanoparticles are synthesized by a simple low-temperature solvothermal method. The influence of Ta2O5 nanoparticles on photovoltaic performance of DSSCs is systematically investigated. As a result, the DSSC based on 10 wt% Ta2O5 incorporated P25 film exhibits excellent photovoltaic performance with a power conversion efficiency (PCE) as high as 5.85 %. Compared to a reference DSSC based on the pure P25 film (4.93 %), the PCE of DSSCs has been remarkably enhanced by 19 %. Such enhancement can be mainly attributed to the higher electron collection efficiency in P25/Ta2O5 composite films, which result from the suppression of the electron recombination at the photoanode/electrolyte interface.

  13. Superconductivity in Ta3Pd3Te14 with quasi-one-dimensional PdTe2 chains

    PubMed Central

    Jiao, Wen-He; He, Lan-Po; Liu, Yi; Xu, Xiao-Feng; Li, Yu-Ke; Zhang, Chu-Hang; Zhou, Nan; Xu, Zhu-An; Li, Shi-Yan; Cao, Guang-Han

    2016-01-01

    We report bulk superconductivity at 1.0 K in a low-dimensional ternary telluride Ta3Pd3Te14 containing edge-sharing PdTe2 chains along crystallographic b axis, similar to the recently discovered superconductor Ta4Pd3Te16. The electronic heat capacity data show an obvious anomaly at the transition temperature, which indicates bulk superconductivity. The specific-heat jump is ΔC/(γnTc) ≈ 1.35, suggesting a weak coupling scenario. By measuring the low-temperature thermal conductivity, we conclude that Ta3Pd3Te14 is very likely a dirty s-wave superconductor. The emergence of superconductivity in Ta3Pd3Te14 with a lower Tc, compared to that of Ta4Pd3Te16, may be attributed to the lower density of states. PMID:26876362

  14. Gate-tunable phase transitions in thin flakes of 1T-TaS2

    NASA Astrophysics Data System (ADS)

    Yu, Yijun; Yang, Fangyuan; Lu, Xiu Fang; Yan, Ya Jun; Cho, Yong-Heum; Ma, Liguo; Niu, Xiaohai; Kim, Sejoong; Son, Young-Woo; Feng, Donglai; Li, Shiyan; Cheong, Sang-Wook; Chen, Xian Hui; Zhang, Yuanbo

    2015-03-01

    The ability to tune material properties using gating by electric fields is at the heart of modern electronic technology. It is also a driving force behind recent advances in two-dimensional systems, such as the observation of gate electric-field-induced superconductivity and metal-insulator transitions. Here, we describe an ionic field-effect transistor (termed an iFET), in which gate-controlled Li ion intercalation modulates the material properties of layered crystals of 1T-TaS2. The strong charge doping induced by the tunable ion intercalation alters the energetics of various charge-ordered states in 1T-TaS2 and produces a series of phase transitions in thin-flake samples with reduced dimensionality. We find that the charge-density wave states in 1T-TaS2 collapse in the two-dimensional limit at critical thicknesses. Meanwhile, at low temperatures, the ionic gating induces multiple phase transitions from Mott-insulator to metal in 1T-TaS2 thin flakes, with five orders of magnitude modulation in resistance, and superconductivity emerges in a textured charge-density wave state induced by ionic gating. Our method of gate-controlled intercalation opens up possibilities in searching for novel states of matter in the extreme charge-carrier-concentration limit.

  15. Gate-tunable phase transitions in thin flakes of 1T-TaS2.

    PubMed

    Yu, Yijun; Yang, Fangyuan; Lu, Xiu Fang; Yan, Ya Jun; Cho, Yong-Heum; Ma, Liguo; Niu, Xiaohai; Kim, Sejoong; Son, Young-Woo; Feng, Donglai; Li, Shiyan; Cheong, Sang-Wook; Chen, Xian Hui; Zhang, Yuanbo

    2015-03-01

    The ability to tune material properties using gating by electric fields is at the heart of modern electronic technology. It is also a driving force behind recent advances in two-dimensional systems, such as the observation of gate electric-field-induced superconductivity and metal-insulator transitions. Here, we describe an ionic field-effect transistor (termed an iFET), in which gate-controlled Li ion intercalation modulates the material properties of layered crystals of 1T-TaS2. The strong charge doping induced by the tunable ion intercalation alters the energetics of various charge-ordered states in 1T-TaS2 and produces a series of phase transitions in thin-flake samples with reduced dimensionality. We find that the charge-density wave states in 1T-TaS2 collapse in the two-dimensional limit at critical thicknesses. Meanwhile, at low temperatures, the ionic gating induces multiple phase transitions from Mott-insulator to metal in 1T-TaS2 thin flakes, with five orders of magnitude modulation in resistance, and superconductivity emerges in a textured charge-density wave state induced by ionic gating. Our method of gate-controlled intercalation opens up possibilities in searching for novel states of matter in the extreme charge-carrier-concentration limit.

  16. TA-55 Final Safety Analysis Report Comparison Document and DOE Safety Evaluation Report Requirements

    SciTech Connect

    Alan Bond

    2001-04-01

    This document provides an overview of changes to the currently approved TA-55 Final Safety Analysis Report (FSAR) that are included in the upgraded FSAR. The DOE Safety Evaluation Report (SER) requirements that are incorporated into the upgraded FSAR are briefly discussed to provide the starting point in the FSAR with respect to the SER requirements.

  17. Characterization by Small RNA Sequencing of Taro Bacilliform CH Virus (TaBCHV), a Novel Badnavirus.

    PubMed

    Kazmi, Syeda Amber; Yang, Zuokun; Hong, Ni; Wang, Guoping; Wang, Yanfen

    2015-01-01

    RNA silencing is an antiviral immunity that regulates gene expression through the production of small RNAs (sRNAs). In this study, deep sequencing of small RNAs was used to identify viruses infecting two taro plants. Blast searching identified five and nine contigs assembled from small RNAs of samples T1 and T2 matched onto the genome sequences of badnaviruses in the family Caulimoviridae. Complete genome sequences of two isolates of the badnavirus determined by sequence specific amplification comprised of 7,641 nucleotides and shared overall nucleotide similarities of 44.1%‒55.8% with other badnaviruses. Six open reading frames (ORFs) were identified on the plus strand, showed amino acid similarities ranging from 59.8% (ORF3) to 10.2% (ORF6) to the corresponding proteins encoded by other badnaviruses. Phylogenetic analysis also supports that the virus is a new member in the genus Badnavirus. The virus is tentatively named as Taro bacilliform CH virus (TaBCHV), and it is the second badnavirus infecting taro plants, following Taro bacilliform virus (TaBV). In addition, analyzes of viral derived small RNAs (vsRNAs) from TaBCHV showed that almost equivalent number of vsRNAs were generated from both strands and the most abundant vsRNAs were 21 nt, with uracil bias at 5' terminal. Furthermore, TaBCHV vsRNAs were asymmetrically distributed on its entire circular genome at both orientations with the hotspots mainly generated in the ORF5 region.

  18. Physiologic Stresses Reveal a Salmonella Persister State and TA Family Toxins Modulate Tolerance to These Stresses

    PubMed Central

    Silva-Herzog, Eugenia; McDonald, Erin M.; Crooks, Amy L.; Detweiler, Corrella S.

    2015-01-01

    Bacterial persister cells are considered a basis for chronic infections and relapse caused by bacterial pathogens. Persisters are phenotypic variants characterized by low metabolic activity and slow or no replication. This low metabolic state increases pathogen tolerance to antibiotics and host immune defenses that target actively growing cells. In this study we demonstrate that within a population of Salmonella enterica serotype Typhimurium, a small percentage of bacteria are reversibly tolerant to specific stressors that mimic the macrophage host environment. Numerous studies show that Toxin-Antitoxin (TA) systems contribute to persister states, based on toxin inhibition of bacterial metabolism or growth. To identify toxins that may promote a persister state in response to host-associated stressors, we analyzed the six TA loci specific to S. enterica serotypes that cause systemic infection in mammals, including five RelBE family members and one VapBC member. Deletion of TA loci increased or decreased tolerance depending on the stress conditions. Similarly, exogenous expression of toxins had mixed effects on bacterial survival in response to stress. In macrophages, S. Typhimurium induced expression of three of the toxins examined. These observations indicate that distinct toxin family members have protective capabilities for specific stressors but also suggest that TA loci have both positive and negative effects on tolerance. PMID:26633172

  19. Characterization of Toxin-Antitoxin (TA) Systems in Pseudomonas aeruginosa Clinical Isolates in Iran

    PubMed Central

    Savari, Mohammad; Rostami, Soodabeh; Ekrami, Alireza; Bahador, Abbas

    2016-01-01

    Background: Pseudomonas aeruginosa is among the most problematic hospital and community-acquired pathogens. Toxin-antitoxin (TA) systems are maintenance regulatory systems in bacteria and have recently been considered new targets for antimicrobial therapy. The prevalence and transcription of these systems in clinical isolates are still unknown. Objectives: The aim of this study was to characterize three types of TA systems (parDE, relBE, and higBA) among P. aeruginosa clinical isolates. Materials and Methods: We typed our clinical isolates by ERIC-PCR (enterobacterial repetitive intergenic consensus sequence-based polymerase chain reaction) and BOX-PCR. We then investigated 174 P. aeruginosa clinical isolates from three hospitals in Ahvaz, Iran, for the presence of TA system genes, and determined whether these systems were encoded on chromosomes or plasmids by amplification of the flanking regions. Results: Our results showed that in the 174 P. aeruginosa isolates, relBE and higBA were universal, but parDE was less prevalent. Both of the flanking regions of the parDE genes in all positive isolates were amplified. The flanking regions of nearly all relBE genes were amplified. Amplification was observed for the downstream sequence of every higBA locus, as well as for the region upstream of higBA, except in 14 strains. Conclusions: Based on the presence of TA systems in the majority of P. aeruginosa isolates, these could be used as a novel target for antimicrobial therapy. PMID:27099681

  20. Growth and physical properties of epitaxial metastable cubic TaN(001)

    SciTech Connect

    Shin, C.-S.; Gall, D.; Desjardins, P.; Vailionis, A.; Kim, H.; Petrov, I.; Greene, J. E.; Oden, M.

    1999-12-13

    We report the growth of epitaxial metastable B1 NaCl structure TaN(001) layers. The films were grown on MgO(001) at 600 degree sign C by ultrahigh vacuum reactive magnetron sputter deposition in mixed Ar/N{sub 2} discharges maintained at 20 mTorr (2.67 Pa). X-ray diffraction and transmission electron microscopy results establish the epitaxial relationship as cube-on-cube, (001){sub TaN}(parallel sign)(001){sub MgO} with [100]{sub TaN}(parallel sign)[100]{sub MgO}, while Rutherford backscattering spectroscopy shows that the layers are overstoichiometric with N/Ta=1.22{+-}0.02. The room-temperature resistivity is 225 {mu}{omega} cm with a small negative temperature dependence between 20 and 400 K. The hardness and elastic modulus, as determined by nanoindentation measurements, are 30.8{+-}0.9 and 457{+-}16 GPa, respectively. (c) 1999 American Institute of Physics.

  1. "Chalepa Ta Kala," "Fine Things Are Difficult": Socrates' Insights into the Psychology of Teaching and Learning

    ERIC Educational Resources Information Center

    Mintz, Avi I.

    2010-01-01

    The proverb "chalepa ta kala" ("fine things are difficult") is invoked in three dialogues in the Platonic corpus: "Hippias Major," "Cratylus" and "Republic." In this paper, I argue that the context in which the proverb arises reveals Socrates' considerable pedagogical dexterity as he uses the proverb to rebuke his interlocutor in one dialogue but…

  2. Isomer residual ratio of odd-odd isotope {sup 180}Ta in supernova nucleosynthsis

    SciTech Connect

    Hayakawa, Takehito; Kajino, Toshitaka; Chiba, Satoshi; Mathews, Grant

    2010-06-01

    The nucleosynthesis of {sup 180}Ta has remained an unsolved problem and as its origin many nucleosynthesis mechanisms have been proposed. This isotope has the unique feature that the naturally occurring abundance of {sup 180}Ta is actually a meta-stable isomer (half-life of >=10{sup 15} yr), while the ground state is a 1{sup +} unstable state which beta-decays with a half-life of only 8.15 hr. We have made a new time-dependent calculation of {sup 180}Ta meta-stable isomer residual ratio after supernova neutrino-induced reactions. This residual isomer ratio is crucial for understanding the production and survival of this naturally occurring rare isotope. We have constructed a new model under temperature evolution after type II supernova explosion. We include the explicit linking between the isomer and all known excited states and found that the residual ratio is insensitive to astrophysical parameters such as neutrino energy spectrum, explosion energy, decay time constant. We find that the explicit time evolution of the synthesis of {sup 180}Ta avoids the overproduction relative to {sup 138}La for a neutrino process neutrino temperature of 4 MeV.

  3. Mentoring and the Faculty-TA Relationship: Faculty Perceptions and Practices

    ERIC Educational Resources Information Center

    Calkins, Susanna; Kelley, Matthew R.

    2005-01-01

    The current investigation was designed to examine faculty perceptions and practices of mentoring in the faculty-TA (teaching assistant) relationship. A survey of faculty members at a large Midwestern research institution revealed that most faculty members considered themselves to be, or wished to be, mentors to their teaching assistants. The…

  4. Long-term multicentre trial with TA-RO CAP, a new spermicidal product.

    PubMed

    Giarola, A; Perniola, L; Gazzani, G; Magni, E

    1979-11-01

    326 healthy couples were selected to enter the trial of a new intravaginal contraceptive called the TA-RO CAP. The trial lasted three years. Clinical and laboratory examinations were performed periodically to determine the long-term effectiveness, tolerability and acceptance. Statistical evaluation of results was performed by life-table analysis.

  5. Characterization by Small RNA Sequencing of Taro Bacilliform CH Virus (TaBCHV), a Novel Badnavirus

    PubMed Central

    Kazmi, Syeda Amber; Yang, Zuokun; Hong, Ni; Wang, Guoping; Wang, Yanfen

    2015-01-01

    RNA silencing is an antiviral immunity that regulates gene expression through the production of small RNAs (sRNAs). In this study, deep sequencing of small RNAs was used to identify viruses infecting two taro plants. Blast searching identified five and nine contigs assembled from small RNAs of samples T1 and T2 matched onto the genome sequences of badnaviruses in the family Caulimoviridae. Complete genome sequences of two isolates of the badnavirus determined by sequence specific amplification comprised of 7,641 nucleotides and shared overall nucleotide similarities of 44.1%‒55.8% with other badnaviruses. Six open reading frames (ORFs) were identified on the plus strand, showed amino acid similarities ranging from 59.8% (ORF3) to 10.2% (ORF6) to the corresponding proteins encoded by other badnaviruses. Phylogenetic analysis also supports that the virus is a new member in the genus Badnavirus. The virus is tentatively named as Taro bacilliform CH virus (TaBCHV), and it is the second badnavirus infecting taro plants, following Taro bacilliform virus (TaBV). In addition, analyzes of viral derived small RNAs (vsRNAs) from TaBCHV showed that almost equivalent number of vsRNAs were generated from both strands and the most abundant vsRNAs were 21 nt, with uracil bias at 5' terminal. Furthermore, TaBCHV vsRNAs were asymmetrically distributed on its entire circular genome at both orientations with the hotspots mainly generated in the ORF5 region. PMID:26207896

  6. TA-Doc Linker Role. Draft. Documentation and Technical Assistance in Urban Schools.

    ERIC Educational Resources Information Center

    Holmes, Manford L.

    One of the aims of the Documentation and Technical Assistance (DTA) Project is to apply educational information that has been utilized for problem solving in one organization to other settings with their own unique characteristics. Within the staff of the DTA project, the position of Technical Assistance-Documentation Linker (TA-Doc Linker) was…

  7. Natural variation of rice blast resistant gene Pi-ta in Oryza species

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Pi-ta gene in rice is a putative NBS type cytoplasmic receptor conferring resistance to races of Magnaporthe oryzae in a gene-for-gene manner. A Functional Nucleotide Polymorphism (FNP) change resulting in an amino acid substitution of Alanine to Serine at position 918 (nucleotide G to T at posi...

  8. Ferromagnetism in chemically reduced LiNbO3 and LiTaO3 crystals

    NASA Astrophysics Data System (ADS)

    Yan, Tao; Ye, Ning; Xu, Liuwei; Sang, Yuanhua; Chen, Yanxue; Song, Wei; Long, Xifa; Wang, Jiyang; Liu, Hong

    2016-05-01

    The ferromagnetism of bulk LiNbO3 and LiTaO3 at room temperature was investigated for the first time in the present work. The stoichiometric LiNbO3 is non-magnetic, while congruent LiNbO3 and LiTaO3 show very weak ferromagnetism. After chemical reduction in a mixture of zinc and lithium carbonate powders under flowing nitrogen, the ferromagnetic behavior of each sample became clear, with an increased value of magnetization. The saturation magnetization, the magnetic remanence and the coercive field of reduced congruent LiNbO3 are 7.0  ×  10‑3 emu g‑1, 0.65  ×  10‑3 emu g‑1 and 0.050 kOe, respectively. The ferromagnetism of chemically reduced LiNbO3 and LiTaO3 can be explained by considering the intrinsic Li vacancies, the appearance of Nb4+ (or Ta4+) on the surface with non-zero net spin and the oxygen vacancies at the surface.

  9. Oxygen vacancies in amorphous-Ta2O5 from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Lee, Jihang; Kioupakis, Emmanouil; Lu, Wei

    Oxygen vacancies are thought to play a crucial role in the electrical and optical properties of tantalum pentoxide (Ta2O5) devices. Even though numerous experimental studies on oxygen vacancies in Ta2O5 exist, experimentally detected defects are ambiguously identified due to the absence of an accurate and conclusive theoretical analysis. We investigate oxygen vacancies in amorphous Ta2O5 with first-principles calculations based on hybrid density functional theory. The calculated thermodynamic and optical transition levels of stable oxygen vacancies are in good agreement with measured values from a variety of experimental methods, providing conclusive clues for the identification of the defect states observed in experiments. We determine the concentration of oxygen vacancies and their dominant oxidation state as a function of growth conditions. We analyze the characteristics of extra electrons introduced by donor-like oxygen vacancies, which include the formation of polarons. Our results provide insight into the fundamental properties of oxygen vacancies in Ta2O5, which is essential to controlling the properties of films and optimize the performance of devices. This research was supported by the AFOSR through MURI grant FA9550-12-1-0038 and the National Science Foundation CAREER award through Grant No. DMR-1254314. Computational resources were provided by the DOE NERSC facility.

  10. Opto-electronic properties of Ta3N5: a joint experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Morbec, Juliana; Rocca, Dario; Pinaud, Blaise; Jaramillo, Thomas; Galli, Giulia

    2014-03-01

    Tantalum nitride (Ta3N5) is considered a promising material for use in photoelectrochemical cells, due to its suitable band gap for visible light absorption and favorable band-edge positions for water splitting. However, Ta3N5 films have been recently shown to exhibit low photocurrent (i.e. less than 50% of the theoretical limit). We report a joint experimental and ab initio theoretical study of the opto-electronic properties of Ta3N5, aimed at understanding possible reasons for the limited photocurrent. Our experimental optical spectra of films with different thicknesses show two absorption edges at 2.1 and 2.5 eV. To provide an interpretation of these features, we performed ab initio calculations, at several levels of theory, of the electronic band structure and optical absorption spectra of Ta3N5. We employed density functional theory with semi-local (PBE/LDA) and hybrid (PBE0/HSE06) functionals and many body perturbation theory at the G0W0 level, and we obtained optical spectra by solving the Bethe-Salpeter equation within density matrix perturbation theory. Work supported by DOE/BES DE-FG02-06ER46262 and NSF-CHE-1305124. Computing resources are partially provided by NERSC.

  11. Dielectric Properties of Layered ZnTa2O6/Poly(tetrafluoroethylene) Composites

    NASA Astrophysics Data System (ADS)

    Jeon, Chang Jun; Kim, Eung Soo

    2012-11-01

    The effects of ZnTa2O6 content and layered structure on the dielectric properties of ZnTa2O6/poly(tetrafluoroethylene) (PTFE) composites were investigated at microwave frequency. With increasing ZnTa2O6 content, the dielectric constant (K) and dielectric loss (tan δ) of the composites increased due to the K values of the individual components and the microstructure. For the composites with layered structures, tan δ was dependent on the internal strain of the composites. Several types of theoretical models were employed to predict the effective K of the composites and the predicted values were compared with experimental data. The temperature coefficient of resonant frequency (TCF) was also discussed as it characterises the thermal stability of the composites. Typically, K of 4.24, tan δ of 1.36 ×10-3 and, TCF of 4.75 ppm/°C were obtained for the single layered PTFE composites with 0.2 volume fraction (Vf) of ZnTa2O6.

  12. High-pressure shock behavior of WC and Ta2O5 powders.

    SciTech Connect

    Knudson, Marcus D.; Reinhart, William Dodd; Vogler, Tracy John; Root, Seth

    2011-10-01

    Planar shock experiments were conducted on granular tungsten carbide (WC) and tantalum oxide (Ta{sub 2}O{sub 5}) using the Z machine and a 2-stage gas gun. Additional shock experiments were also conducted on a nearly fully dense form of Ta{sub 2}O{sub 5}. The experiments on WC yield some of the highest pressure results for granular materials obtained to date. Because of the high distention of Ta{sub 2}O{sub 5}, the pressures obtained were significantly lower, but the very high temperatures generated led to large contributions of thermal energy to the material response. These experiments demonstrate that the Z machine can be used to obtain accurate shock data on granular materials. The data on Ta{sub 2}O{sub 5} were utilized in making improvements to the P-{lambda} model for high pressures; the model is found to capture the results not only of the Z and gas gun experiments but also those from laser experiments on low density aerogels. The results are also used to illustrate an approach for generating an equation of state using only the limited data coming from nanoindentation. Although the EOS generated in this manner is rather simplistic, for this material it gives reasonably good results.

  13. Nanoscale cation motion in TaOx, HfOx and TiOx memristive systems

    NASA Astrophysics Data System (ADS)

    Wedig, Anja; Luebben, Michael; Cho, Deok-Yong; Moors, Marco; Skaja, Katharina; Rana, Vikas; Hasegawa, Tsuyoshi; Adepalli, Kiran K.; Yildiz, Bilge; Waser, Rainer; Valov, Ilia

    2016-01-01

    A detailed understanding of the resistive switching mechanisms that operate in redox-based resistive random-access memories (ReRAM) is key to controlling these memristive devices and formulating appropriate design rules. Based on distinct fundamental switching mechanisms, two types of ReRAM have emerged: electrochemical metallization memories, in which the mobile species is thought to be metal cations, and valence change memories, in which the mobile species is thought to be oxygen anions (or positively charged oxygen vacancies). Here we show, using scanning tunnelling microscopy and supported by potentiodynamic current-voltage measurements, that in three typical valence change memory materials (TaOx, HfOx and TiOx) the host metal cations are mobile in films of 2 nm thickness. The cations can form metallic filaments and participate in the resistive switching process, illustrating that there is a bridge between the electrochemical metallization mechanism and the valence change mechanism. Reset/Set operations are, we suggest, driven by oxidation (passivation) and reduction reactions. For the Ta/Ta2O5 system, a rutile-type TaO2 film is believed to mediate switching, and we show that devices can be switched from a valence change mode to an electrochemical metallization mode by introducing an intermediate layer of amorphous carbon.

  14. Nonlinear effects in collision cascades and high energy shock waves during ta-C:H growth

    SciTech Connect

    Piazza, F.; Resto, O.; Morell, G.

    2007-07-01

    The surface topography of hydrogenated tetrahedral amorphous carbon (ta-C:H) is critical for various applications such as microelectromechanical devices, magnetic and optical storage devices, and medical implants. The surface topography of ta-C:H films deposited by distributed electron cyclotron resonance plasma from C{sub 2}H{sub 2} gas precursor was investigated. The effects of pressure, together with ion flux and energy, are studied by atomic force microscopy in relation to the structural evolution of the films. The results are compared with the predictions of the Edward-Wilkinson model [Proc. R. Soc. London, Ser. A 44, 1039 (1966)] recently proposed to account for ta-C:H growth and with previous interpretations based on hypersonic shock waves. The random hillocks observed on the smooth surfaces of ta-C:H films deposited at high pressure are thought to result from the interference of high energy shock waves triggered by C{sub 4}H{sub x}{sup +} ions that produce overlapping collision cascades and induce nonlinear effects.

  15. Structure and high photocatalytic activity of (N, Ta)-doped TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Le, N. T. H.; Thanh, T. D.; Pham, V.-T.; Phan, T. L.; Lam, V. D.; Manh, D. H.; Anh, T. X.; Le, T. K. C.; Thammajak, N.; Hong, L. V.; Yu, S. C.

    2016-10-01

    A hydrothermal method was used to prepare three nano-crystalline samples of TiO2 (S1), N-doped TiO2 (S2), and (N, Ta)-codoped TiO2 (S3) with average crystallite sizes (D) of 13-25 nm. X-ray diffraction studies confirmed a single phase of the samples with a tetragonal/anatase structure. A slight increase in the lattice parameters was observed when N and/or Ta dopants were doped into the TiO2 host lattice. Detailed analyses of extended X-ray absorption spectra indicated that N- and/or Ta-doping into TiO2 nanoparticles influenced the co-ordination number and radial distance (R) of Ti ions in the anatase structure. Concerning their absorption spectra, (N, Ta)-doping narrowed the band gap (Eg) of TiO2 from 3.03 eV for S1 through 2.94 eV for S2 to 2.85 eV for S3. Such results revealed the applicability of these nanoparticles in the photocatalytic field working in the ultraviolet (UV)-visible region. Among these, photocatalytic activity of S3 was the strongest. By using S3 as a catalyst powder, the degradation efficiency of methylene blue solution was about 99% and 93% after irradiation of UV-visible light for 75 min and visible-light for 180 min, respectively.

  16. Strain-induced structural phase transition of a Ni lattice through dissolving Ta solute atoms

    NASA Astrophysics Data System (ADS)

    Zhang, Q.; Lai, W. S.; Liu, B. X.

    2001-06-01

    The structural phase transition of a single-crystal Ni lattice upon dissolving Ta solute atoms is investigated by means of molecular-dynamics simulations with a realistic n-body Ni-Ta potential. It is found that when the solute concentration is within 9-19 at. % of Ta, the accumulated strain results in a martensitic phase transition, i.e., face-centered-cubic (fcc) Ni transforms into a face-centered-orthorhombic-(fco) like structure through shearing, and that when the solute concentration is over 21 at. % of Ta, the Ni lattice collapses and turns into an amorphous state. Comparatively, for the case of an initial hcp Ni lattice, the same martensitic and amorphization transitions also take place. The former hcp-fco transition, however, is mainly through atomic rearrangement as well as readjustment of lattice parameters, and the resultant state is almost perfect single crystal with no shearing bands. Besides, the above structural transitions are frequently in association with a dramatic softening in shear elastic moduli.

  17. Production ratio of meta-stable isomer in {sup 180}Ta by neutrino-induced reactions

    SciTech Connect

    Hayakawa, Takehito; Kajino, Toshitaka; Chiba, Satoshi; Mathews, Grant

    2010-05-12

    The nucleosynthesis of {sup 180}Ta has remained an unsolved problem and as its origin many nucleosynthesis mechanisms have been proposed. This isotope has the unique feature that the naturally occurring abundance of {sup 180}Ta is actually a meta-stable isomer (half-life of >=10{sup 15} yr), while the ground state is a 1{sup +} unstable state which beta-decays with a half-life of only 8.15 hr. We have made a new time-dependent calculation of {sup 180}Ta meta-stable isomer residual ratio after supernova neutrino-induced reactions. This isomer residual ratio is crucial for understanding the production and survival of this naturally occurring rare isotope. We have constructed a new model under temperature evolution after type II supernova explosion. We include the explicit linking between the isomer and all known excited states and found that the residual ratio is insensitive to astrophysical parameters such as neutrino energy spectrum, explosion energy, decay time constant. We find that the explicit time evolution of the synthesis of {sup 180}Ta avoids the overproduction relative to {sup 138}La for a neutrino process neutrino temperature of 4 MeV.

  18. Characterization by Small RNA Sequencing of Taro Bacilliform CH Virus (TaBCHV), a Novel Badnavirus.

    PubMed

    Kazmi, Syeda Amber; Yang, Zuokun; Hong, Ni; Wang, Guoping; Wang, Yanfen

    2015-01-01

    RNA silencing is an antiviral immunity that regulates gene expression through the production of small RNAs (sRNAs). In this study, deep sequencing of small RNAs was used to identify viruses infecting two taro plants. Blast searching identified five and nine contigs assembled from small RNAs of samples T1 and T2 matched onto the genome sequences of badnaviruses in the family Caulimoviridae. Complete genome sequences of two isolates of the badnavirus determined by sequence specific amplification comprised of 7,641 nucleotides and shared overall nucleotide similarities of 44.1%‒55.8% with other badnaviruses. Six open reading frames (ORFs) were identified on the plus strand, showed amino acid similarities ranging from 59.8% (ORF3) to 10.2% (ORF6) to the corresponding proteins encoded by other badnaviruses. Phylogenetic analysis also supports that the virus is a new member in the genus Badnavirus. The virus is tentatively named as Taro bacilliform CH virus (TaBCHV), and it is the second badnavirus infecting taro plants, following Taro bacilliform virus (TaBV). In addition, analyzes of viral derived small RNAs (vsRNAs) from TaBCHV showed that almost equivalent number of vsRNAs were generated from both strands and the most abundant vsRNAs were 21 nt, with uracil bias at 5' terminal. Furthermore, TaBCHV vsRNAs were asymmetrically distributed on its entire circular genome at both orientations with the hotspots mainly generated in the ORF5 region. PMID:26207896

  19. Estrogen receptor 1 gene (TA)n polymorphism is associated with lone atrial fibrillation in men

    PubMed Central

    Golubić, Karlo; Šmalcelj, Anton; Sertić, Jadranka; Juričić, Ljiljana

    2014-01-01

    Aim To determine the association between the number of thymine-adenine (TA)n dinucleotide repeats in the promoter region of the gene coding for the estrogen receptor alpha (ESR1) and the prevalence of lone atrial fibrillation (AF) in men. Methods We conducted a case-control study involving 89 men with lone AF and 166 healthy male controls. The ESR1 genotype was established by polymerase chain reaction and capillary electrophoresis. To assess the association of ESR1 genotype with AF, logistic regression models were built with AF as outcome. Results Men with lone AF had significantly greater number of (TA)n repeats of single alleles than controls (mean ± standard deviation, 19.2 ± 4.2 vs 18 ± 4.3, P = 0.010). After adjustment for other factors, a unit-increase in (TA)n repeat number was associated with a significantly greater likelihood of AF (odds ratio 1.069; 95% confidence interval 1.024-1.116, P = 0.002). Conclusions Our results indicate that a greater number of (TA)n repeats in the promoter region of ESR1 is associated with a significantly increased likelihood of lone atrial fibrillation in men. PMID:24577825

  20. "Forest Grove School District v. T.A.": The Supreme Court and Unilateral Private Placements

    ERIC Educational Resources Information Center

    Yell, Mitchell L.; Katsiyannis, Antonis; Collins, Terri S.

    2010-01-01

    On June 22, 2009, the U.S. Supreme Court issued its decision in the case "Forest Grove School District v. T.A." (hereafter "Forest Grove"). In "Forest Grove," the High Court answered the question of whether the parents of students with disabilities are entitled to reimbursement for the costs associated with placing their child in a private school…

  1. Removal of contaminated air scrubbers at TA-35-7, Los Alamos National Laboratory

    SciTech Connect

    Harper, J.R.; Garde, R.

    1981-11-01

    Five large excess contaminated air scrubbers located in Building 7 at TA-35 were removed and disposed of in 1979 to 1980. The scrubbers were contaminated with strontium-yttrium and cesium. This report details the removal procedures, the health physics program, the waste management program, and the costs of the operation.

  2. A New One-dimensional Quantum Material - Ta2Pd3Se8 Atomic Chain

    NASA Astrophysics Data System (ADS)

    Liu, Xue; Liu, Jinyu; Hu, Jin; Yue, Chunlei; Mao, Zhiqiang; Wei, Jiang; Antipina, Liubov; Sorokin, Pavel; Sanchez, Ana

    Since the discovery of carbon nanotube, there has been a persistent effort to search for other one dimensional (1D) quantum systems. However, only a few examples have been found. We report a new 1D example - semiconducting Ta2Pd3Se8. We demonstrate that the Ta2Pd3Se8 nanowire as thin as 1.3nm can be easily obtained by applying simple mechanical exfoliation from its bulk counterpart. High resolution TEM shows an intrinsic 1D chain-like crystalline morphology on these nano wires, indicating weak bonding between these atomic chains. Theoretical calculation shows a direct bandgap structure, which evolves from 0.53eV in the bulk to 1.04eV in single atomic chain. The field effect transistor based on Ta2Pd3Se8 nanowire achieved a promising performance with 104On/Off ratio and 80 cm2V-1s-1 mobility. Low temperature transport study reflects two different mechanisms, variable range hopping and thermal activation, which dominate the transport properties at different temperature regimes. Ta2Pd3Se8 nanowire provides an intrinsic 1D material system for the study low dimensional condensed matter physics.

  3. Anelastic properties of (TaSe 4) 2I at low frequencies

    NASA Astrophysics Data System (ADS)

    Salva, H.; Ghilarducci, A.; Monceau, P.; Levy, F.; D'Anna, G.; Benoit, W.

    1995-05-01

    We have performed torsion measurements in (TaSe 4) 2I in the temperature range 110-290 K and 5.10 -3-10 Hz measuring frequency. We have always found a dip in modulus at the Peierls transition and that deformation of measurement gives additional response in modulus and internal friction spectra. These results are compared with existing models.

  4. Computer-Aided Assessment Questions in Engineering Mathematics Using "MapleTA"[R

    ERIC Educational Resources Information Center

    Jones, I. S.

    2008-01-01

    The use of "MapleTA"[R] in the assessment of engineering mathematics at Liverpool John Moores University (JMU) is discussed with particular reference to the design of questions. Key aspects in the formulation and coding of questions are considered. Problems associated with the submission of symbolic answers, the use of randomly generated numbers…

  5. Directional Solidification and Mechanical Properties of NiAl-NiAlTa Alloys

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    Directional solidification of eutectic alloys is a promising technique for producing in-situ composite materials exhibiting a balance of properties. Consequently, the microstructure, creep strength and fracture toughness of directionally solidified NiAl-NiAlTa alloys were investigated. Directional solidification was performed by containerless processing techniques to minimize alloy contamination. The eutectic composition was found to be NiAl-15.5 at% Ta and well-aligned microstructures were produced at this composition. A near-eutectic alloy of NiAl-14.5Ta was also investigated. Directional solidification of the near-eutectic composition resulted in microstructures consisting of NiAl dendrites surrounded by aligned eutectic regions. The off-eutectic alloy exhibited promising compressive creep strengths compared to other NiAl-based intermetallics, while preliminary testing indicated that the eutectic alloy was competitive with Ni-base single crystal superalloys. The room temperature toughness of these two-phase alloys was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa.

  6. Electric Properties of NaTaO3 Obtained by Hydrothermal Method

    NASA Astrophysics Data System (ADS)

    Malaescu, Dan; Grozescu, Ioan; Sfirloaga, Paula; Vlazan, Paulina; Marin, Catalin N.

    2015-12-01

    Two samples of NaTaO3 perovskite materials were prepared by the standard hydrothermal method at the same reaction temperature (600 °C) but with different sintering times: 6 hours for sample S1 and 12 hours for sample S2. Using X-ray diffraction (XRD), it shows that samples S1 and S2 are mixtures of Na-Ta oxides (Ta2O5 and the prevailing phase NaTaO3). The scanning electron microscopy analysis (SEM), shows that the grains are connected each other in agglomerated clusters of size about few hundred nanometers. The frequency (f) dependencies of complex impedance, Z(f) = Z'(f) - i Z''(f) of the samples, over the frequency range 20 Hz - 2 MHz, at room temperature are presented. The real component Z' of the complex impedance decreases with increasing frequency and the imaginary component Z'' has two maximum corresponding to two relaxation processes. The results obtained from the complex impedance spectroscopy, Z''(Z') showed the appearance of two semicircles, corresponding to grain and grain boundary mechanism. Experimental results have been fitted with two parallel RC equivalent circuits connected in series and the parameters R and C have been evaluated.

  7. MRI compatible Nb-Ta-Zr alloys used for vascular stents: optimization for mechanical properties.

    PubMed

    Li, Hui-Zhe; Xu, Jian

    2014-04-01

    With the increased usage of magnetic resonance imaging (MRI) as a diagnostic tool in clinic, the currently-used metals for vascular stents, such as 316L stainless steel (SS), Co-Cr alloys and Ni-Ti alloys, are challenged by their unsatisfactory MRI compatibility, due to their constituents containing ferromagnetic elements. To provide more MRI compatible vascular stents, the Nb-xTa-2Zr (30≤x≤70) series alloys were selected in the current work. Several key properties of these alloys were optimized in terms of stent requirements, including magnetic susceptibility, elastic modulus and tensile properties. In the as-cast state, a single-phase solid solution with bcc structure was formed in the alloys. The volume magnetic susceptibility (χv) and Young's modulus (E) of the alloys scaled linearly with the Ta content. Increasing the Ta content gave rise to the decreased χv and the increased E, together with the elevated yield strength but less-changed elongation. From multiple requirements for the stents, the Nb-60Ta-2Zr alloy exhibits an optimal properties, including the χv of about 3% of the 316L SS, the E of 142GPa superior to pure niobium, high mass density of 12.03g/cm(3) favored to the X-ray visibility, yield strength of ~330MPa comparable to the 316L SS and a elongation of ~24%. These remarkable advantages make it quite promising as a new candidate of stent metals.

  8. Induction of Abasic Sites by the Drinking-Water Mutagen MX in Salmonella TA100

    EPA Science Inventory

    Mutagen X (MX) is a chlorinated furanone that accounts for more of the mutagenic activity of drinking water than any other disinfection by-product. It is one of the most potent base-substitution mutagens in the Salmonella (Ames) mutagenicity assay, producing primarily GC to TA mu...

  9. Oxidation Resitant HfC-TaC Rocket Thruster for High Performance Propellants

    NASA Technical Reports Server (NTRS)

    Patterson, Mark

    1999-01-01

    The purpose of this reasearch effort was to develop high temperature, oxidation resistant thrusters which would lessen the thruster cooling requirements, resulting in increased performance and longer life for onboard propulsion systems for spacecraft. This research effort focussed on developing ceramic matrix composites (CMCs) for this application, and specifically investigated the use of HfC stabilized with TaC. This material composition can potentially operate in a stoichiometric oxygen to hydrogen ratio at a temperature of 5000 deg F (2760 deg C) in a radiatively cooled mode. Various compositions of Hafnium Carbide (HfC) and Tantalum Carbide (TaC) were deposited by chemical vapor deposition (CVD) and tested, in an attempt to identify the composition which offered the best oxidation resistance. Although it was identified that small amounts of TaC appeared to offer improved oxidation resistance over HfC alone, an optimal composition was not identified. A 251bf thruster was fabricated from a novel CMC sandwich construction with a HfC-TaC matrix, and survived two test firings, each of 5 seconds before a failure in the injector caused the run to be aborted. It was not possible to control the relative stoichiometry of the HfC and TaC composition throughout the reactor due to the large difference in the thermodynamics of the HfC and TaC formation from their respective chlorides. This also resulted in an inability to infiltrate TaC into the preform under the experimental conditions investigated. Other material compositions were fabricated and tested and two material systems; HfC-SiC functionally graded to C(sub f)/C and Re functionally graded to C(sub f)/C were selected for further testing. These functionally graded composites have use in a number of propulsion applications presently of interest to NASA and the defense industry. Their ability to withstand extremely hostile thermal environments and the light-weight and high-strength exhibited from the C(sub f

  10. Association of Interferon Gamma +874T/A Polymorphism and Leukemia Risk: A Meta-Analysis.

    PubMed

    Wu, Zhitong; Sun, Yifan; Zhu, Shengbo; Tang, Shifu; Liu, Chunming; Qin, Wenzhou

    2016-03-01

    Interferon gamma (IFN-γ) has antitumor and antiproliferative effects, and previous studies indicated IFN-γ +874T/A (rs2430561) polymorphism were related to the risk of many types of cancer. However, the association between IFN-γ +874T/A polymorphism and leukemia risk remained controversial.We performed a comprehensive meta-analysis based on the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement (PRISMA). Electronic database of Embase, Pubmed, and the Cochrane Library were searched for eligible articles published up to December 13, 2015. The association between genetic polymorphisms and leukemia risk was measured by odds ratios (ORs) and its corresponding 95% confidence intervals (CIs).A total of 8 studies amounting to 420 patients and 767 control subjects were retrieved for this study. Although associations between IFN-γ +874T/A polymorphism and overall leukemia risks were lacking, decreased chronic lymphocytic leukemia (CLL) risk was detected in the allelic model (T vs A, OR=0.660, 95%CI = 0.483-0.902, P = 0.009, I = 0.0% and P = 0.863 for heterogeneity), the codominant model (TT vs AA, OR = 0.472, 95%CI = 0.247-0.902, P = 0.023, I = 0.0% and P = 0.994 for heterogeneity), and dominant model (TT + TA vs AA, OR = 0.457, 95%CI = 0.285-0.734, P = 0.001, I = 40.3% and P = 0.195 for heterogeneity) by using fixed-effect model separately. On the contrary, results indicated T carries have an increased chronic myelogenous leukemia (CML) risk in dominant model (TT + TA vs AA, OR = 1.783, 95%CI = 1.236-2.573, P = 0.002, I = 19.0% and P = 0.295 for heterogeneity).This study suggests IFN-γ +874T/A polymorphism are related to CML and CLL risk. In addition, our work also points out IFN-γ +874T/A polymorphism may play dual contrasting role in leukemia risk. PMID:27015189

  11. Association of Interferon Gamma +874T/A Polymorphism and Leukemia Risk: A Meta-Analysis.

    PubMed

    Wu, Zhitong; Sun, Yifan; Zhu, Shengbo; Tang, Shifu; Liu, Chunming; Qin, Wenzhou

    2016-03-01

    Interferon gamma (IFN-γ) has antitumor and antiproliferative effects, and previous studies indicated IFN-γ +874T/A (rs2430561) polymorphism were related to the risk of many types of cancer. However, the association between IFN-γ +874T/A polymorphism and leukemia risk remained controversial.We performed a comprehensive meta-analysis based on the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement (PRISMA). Electronic database of Embase, Pubmed, and the Cochrane Library were searched for eligible articles published up to December 13, 2015. The association between genetic polymorphisms and leukemia risk was measured by odds ratios (ORs) and its corresponding 95% confidence intervals (CIs).A total of 8 studies amounting to 420 patients and 767 control subjects were retrieved for this study. Although associations between IFN-γ +874T/A polymorphism and overall leukemia risks were lacking, decreased chronic lymphocytic leukemia (CLL) risk was detected in the allelic model (T vs A, OR=0.660, 95%CI = 0.483-0.902, P = 0.009, I = 0.0% and P = 0.863 for heterogeneity), the codominant model (TT vs AA, OR = 0.472, 95%CI = 0.247-0.902, P = 0.023, I = 0.0% and P = 0.994 for heterogeneity), and dominant model (TT + TA vs AA, OR = 0.457, 95%CI = 0.285-0.734, P = 0.001, I = 40.3% and P = 0.195 for heterogeneity) by using fixed-effect model separately. On the contrary, results indicated T carries have an increased chronic myelogenous leukemia (CML) risk in dominant model (TT + TA vs AA, OR = 1.783, 95%CI = 1.236-2.573, P = 0.002, I = 19.0% and P = 0.295 for heterogeneity).This study suggests IFN-γ +874T/A polymorphism are related to CML and CLL risk. In addition, our work also points out IFN-γ +874T/A polymorphism may play dual contrasting role in leukemia risk.

  12. The Kenticha rare-element pegmatite, Ethiopia: internal differentiation, U-Pb age and Ta mineralization

    NASA Astrophysics Data System (ADS)

    Küster, Dirk; Romer, Rolf L.; Tolessa, Dandena; Zerihun, Desta; Bheemalingeswara, K.; Melcher, Frank; Oberthür, Thomas

    2009-10-01

    The Kenticha rare-element pegmatite, a globally important tantalite source in the Neoproterozoic Adola Belt of southern Ethiopia, is a highly fractionated, huge (2,000 m long and up to 100 m thick), subhorizontal, sheet-like body, discordantly emplaced in ultramafic host rock. It corresponds to the spodumene subtype of the rare-element pegmatite class and belongs to the lithium-cesium-tantalum petrogenetic family. The Kenticha pegmatite is asymmetrically zoned from bottom to top into granitic lower zone, spodumene-free intermediate zone, and spodumene-bearing upper zone. A monomineralic quartz unit is discontinuously developed within the upper zone. Whole-rock data indicate an internal geochemical differentiation of the pegmatite sheet proceeding from the lower zone (K/Rb ~36, K/Cs ~440, Al/Ga ~2,060, Nb/Ta ~2.6) to the upper zone (K/Rb ~19, K/Cs ~96, Al/Ga ~1,600, Nb/Ta ~0.7). The latter one is strongly enriched in Li2O (up to 3.21%), Rb (up to 4,570 ppm), Cs (up to 730 ppm), Ga (up to 71 ppm), and Ta (up to 554 ppm). Similar trends of increasing fractionation from lower zone to upper zone were obtained in muscovite (K/Rb 23-14, K/Cs 580-290, K/Tl 6,790-3,730, Fe/Mn 19-10, Nb/Ta 6.5-3.8) and columbite-tantalite (Mn/Mn + Fe 0.4-1, Ta/Ta + Nb 0.1-0.9). The bottom-to-top differentiation of the Kenticha pegmatite and the Ta mineralization in its upper part are principally attributed to upward in situ fractionation of a residual leucogranitic to pegmatitic melt, largely under closed system conditions. High MgO contents (up to 5.05%) in parts of the upper zone are the result of postmagmatic hydrothermal alteration and contamination by hanging wall serpentinite. U-Pb dating of Mn-tantalite from two zones of the Kenticha pegmatite gave ages of 530.2 ± 1.3 and 530.0 ± 2.3 Ma. Mn-tantalite from the Bupo pegmatite, situated 9 km north of Kenticha, gave an age of 529.2 ± 4.1 Ma, indicating coeval emplacement of the two pegmatites. The emplacement of the pegmatites is

  13. Overexpression of a wheat phospholipase D gene, TaPLDα, enhances tolerance to drought and osmotic stress in Arabidopsis thaliana.

    PubMed

    Wang, Junbin; Ding, Bo; Guo, Yaolin; Li, Ming; Chen, Shuaijun; Huang, Guozhong; Xie, Xiaodong

    2014-07-01

    Phospholipase D (PLD) is crucial for plant responses to stress and signal transduction, however, the regulatory mechanism of PLD in abiotic stress is not completely understood; especially, in crops. In this study, we isolated a gene, TaPLDα, from common wheat (Triticum aestivum L.). Analysis of the amino acid sequence of TaPLDα revealed a highly conserved C2 domain and two characteristic HKD motifs, which is similar to other known PLD family genes. Further characterization revealed that TaPLDα expressed differentially in various organs, such as roots, stems, leaves and spikelets of wheat. After treatment with abscisic acid (ABA), methyl jasmonate, dehydration, polyethylene glycol and NaCl, the expression of TaPLDα was up-regulated in shoots. Subsequently, we generated TaPLDα-overexpressing transgenic Arabidopsis lines under the control of the dexamethasone-inducible 35S promoter. The overexpression of TaPLDα in Arabidopsis resulted in significantly enhanced tolerance to drought, as shown by reduced chlorosis and leaf water loss, higher relative water content and lower relative electrolyte leakage than the wild type. Moreover, the TaPLDα-overexpressing plants exhibited longer roots in response to mannitol treatment. In addition, the seeds of TaPLDα-overexpressing plants showed hypersensitivity to ABA and osmotic stress. Under dehydration, the expression of several stress-related genes, RD29A, RD29B, KIN1 and RAB18, was up-regulated to a higher level in TaPLDα-overexpressing plants than in wild type. Taken together, our results indicated that TaPLDα can enhance tolerance to drought and osmotic stress in Arabidopsis and represents a potential candidate gene to enhance stress tolerance in crops.

  14. Expression of TaWRKY44, a wheat WRKY gene, in transgenic tobacco confers multiple abiotic stress tolerances.

    PubMed

    Wang, Xiatian; Zeng, Jian; Li, Ying; Rong, Xiaoli; Sun, Jiutong; Sun, Tao; Li, Miao; Wang, Lianzhe; Feng, Ying; Chai, Ruihong; Chen, Mingjie; Chang, Junli; Li, Kexiu; Yang, Guangxiao; He, Guangyuan

    2015-01-01

    The WRKY transcription factors have been reported to be involved in various plant physiological and biochemical processes. In this study, we successfully assembled 10 unigenes from expressed sequence tags (ESTs) of wheat and designated them as TaWRKY44-TaWRKY53, respectively. Among these genes, a subgroup I gene, TaWRKY44, was found to be upregulated by treatments with PEG6000, NaCl, 4°C, abscisic acid (ABA), H2O2 and gibberellin (GA). The TaWRKY44-GFP fusion protein was localized to the nucleus of onion epidermal cells, and TaWRKY44 was able to bind to the core DNA sequences of TTGACC and TTAACC in yeast. The N-terminal of TaWRKY44 showed transcriptional activation activity. Expression of TaWRKY44 in tobacco plants conferred drought and salt tolerance and transgenic tobacco exhibited a higher survival rate, relative water content (RWC), soluble sugar, proline and superoxide dismutase (SOD) content, as well as higher activities of catalase (CAT) and peroxidase (POD), but less ion leakage (IL), lower contents of malondialdehyde (MDA), and H2O2. In addition, expression of TaWRKY44 also increased the seed germination rate in the transgenic lines under osmotic stress conditions while exhibiting a lower H2O2 content and higher SOD, CAT, and POD activities. Expression of TaWRKY44 upregulated the expression of some reactive oxygen species (ROS)-related genes and stress-responsive genes in tobacco under osmotic stresses. These data demonstrate that TaWRKY44 may act as a positive regulator in drought/salt/osmotic stress responses by either efficient ROS elimination through direct or indirect activation of the cellular antioxidant systems or activation of stress-associated gene expression. PMID:26322057

  15. Bone response to a novel Ti-Ta-Nb-Zr alloy.

    PubMed

    Stenlund, Patrik; Omar, Omar; Brohede, Ulrika; Norgren, Susanne; Norlindh, Birgitta; Johansson, Anna; Lausmaa, Jukka; Thomsen, Peter; Palmquist, Anders

    2015-07-01

    Commercially pure titanium (cp-Ti) is regarded as the state-of-the-art material for bone-anchored dental devices, whereas the mechanically stronger alloy (Ti-6Al-4V), made of titanium, aluminum (Al) and vanadium (V), is regarded as the material of choice for high-load applications. There is a call for the development of new alloys, not only to eliminate the potential toxic effect of Al and V but also to meet the challenges imposed on dental and maxillofacial reconstructive devices, for example. The present work evaluates a novel, dual-stage, acid-etched, Ti-Ta-Nb-Zr alloy implant, consisting of elements that create low toxicity, with the potential to promote osseointegration in vivo. The alloy implants (denoted Ti-Ta-Nb-Zr) were evaluated after 7 days and 28 days in a rat tibia model, with reference to commercially pure titanium grade 4 (denoted Ti). Analyses were performed with respect to removal torque, histomorphometry and gene expression. The Ti-Ta-Nb-Zr showed a significant increase in implant stability over time in contrast to the Ti. Further, the histological and gene expression analyses suggested faster healing around the Ti-Ta-Nb-Zr, as judged by the enhanced remodeling, and mineralization, of the early-formed woven bone and the multiple positive correlations between genes denoting inflammation, bone formation and remodeling. Based on the present experiments, it is concluded that the Ti-Ta-Nb-Zr alloy becomes osseointegrated to at least a similar degree to that of pure titanium implants. This alloy is therefore emerging as a novel implant material for clinical evaluation. PMID:25848727

  16. Landslides and other mass movements near TA-33, northern White Rock Canyon, New Mexico. Final report

    SciTech Connect

    Dethier, D.P.

    1993-09-01

    Massive slump complexes and at least two rock avalanches flank the eastern rim of the Pajarito Plateau along northern White Rock Canyon, north of TA-33. Landslides failed along mechanically weak rocks in the Santa Fe Group, within the Puye Formation, or in Pliocene alluvial and lacustrine units. The landslides are mainly of early or middle Pleistocene age. The toe area of at least,one slump complex has been active in the late Pleistocene, damming White Rock Canyon near the mouth of Water Canyon. Lacustrine sediment that filled this lake, or series of lakes, to an elevation of at least 1710 m is preserved at a number of upstream sites, including a deposit near the Buckman townsite that exposes 30 m of lacustrine sediment. Charcoal collected at several sites has been submitted for {sup 14}C dating. Landslides, however, probably do not represent a significant short-term threat to the material disposal areas at TA-33. Bedrock that lies beneath the TA-33 mesa is relatively stable, the mesa shows no signs of incipient failure, and past periods of slide activity were responses to rapid downcutting of the Rio Grande and climate change, probably over periods of several decades, at least. Rockfall and headward erosion of gullies do not represent significant decadal hazards on canyon rims near TA-33. Gully migration near MDA-K is a potential threat, but the gullies were not examined in detail. A system of north-trending faults, at least one of which displays Pleistocene activity, bisects the TA-33 mesa. If these faults are capable of producing significant seismic shaking, generalizations about landslide and rockfall hazards must be reevaluated.

  17. Bone response to a novel Ti-Ta-Nb-Zr alloy.

    PubMed

    Stenlund, Patrik; Omar, Omar; Brohede, Ulrika; Norgren, Susanne; Norlindh, Birgitta; Johansson, Anna; Lausmaa, Jukka; Thomsen, Peter; Palmquist, Anders

    2015-07-01

    Commercially pure titanium (cp-Ti) is regarded as the state-of-the-art material for bone-anchored dental devices, whereas the mechanically stronger alloy (Ti-6Al-4V), made of titanium, aluminum (Al) and vanadium (V), is regarded as the material of choice for high-load applications. There is a call for the development of new alloys, not only to eliminate the potential toxic effect of Al and V but also to meet the challenges imposed on dental and maxillofacial reconstructive devices, for example. The present work evaluates a novel, dual-stage, acid-etched, Ti-Ta-Nb-Zr alloy implant, consisting of elements that create low toxicity, with the potential to promote osseointegration in vivo. The alloy implants (denoted Ti-Ta-Nb-Zr) were evaluated after 7 days and 28 days in a rat tibia model, with reference to commercially pure titanium grade 4 (denoted Ti). Analyses were performed with respect to removal torque, histomorphometry and gene expression. The Ti-Ta-Nb-Zr showed a significant increase in implant stability over time in contrast to the Ti. Further, the histological and gene expression analyses suggested faster healing around the Ti-Ta-Nb-Zr, as judged by the enhanced remodeling, and mineralization, of the early-formed woven bone and the multiple positive correlations between genes denoting inflammation, bone formation and remodeling. Based on the present experiments, it is concluded that the Ti-Ta-Nb-Zr alloy becomes osseointegrated to at least a similar degree to that of pure titanium implants. This alloy is therefore emerging as a novel implant material for clinical evaluation.

  18. Sodium-Dependent Glutamate Uptake by an Alkaliphilic, Thermophilic Bacillus Strain, TA2.A1

    PubMed Central

    Peddie, Catherine J.; Cook, Gregory M.; Morgan, Hugh W.

    1999-01-01

    A strain of Bacillus designated TA2.A1, isolated from a thermal spring in Te Aroha, New Zealand, grew optimally at pH 9.2 and 70°C. Bacillus strain TA2.A1 utilized glutamate as a sole carbon and energy source for growth, and sodium chloride (>5 mM) was an obligate requirement for growth. Growth on glutamate was inhibited by monensin and amiloride, both inhibitors that collapse the sodium gradient (ΔpNa) across the cell membrane. N,N-Dicyclohexylcarbodiimide inhibited the growth of Bacillus strain TA2.A1, suggesting that an F1F0-ATPase (H type) was being used to generate cellular ATP needed for anabolic reactions. Vanadate, an inhibitor of V-type ATPases, did not affect the growth of Bacillus strain TA2.A1. Glutamate transport by Bacillus strain TA2.A1 could be driven by an artificial membrane potential (ΔΨ), but only when sodium was present. In the absence of sodium, the rate of ΔΨ-driven glutamate uptake was fourfold lower. No glutamate transport was observed in the presence of ΔpNa alone (i.e., no ΔΨ). Glutamate uptake was specifically inhibited by monensin, and the Km for sodium was 5.6 mM. The Hill plot had a slope of approximately 1, suggesting that sodium binding was noncooperative and that the glutamate transporter had a single binding site for sodium. Glutamate transport was not affected by the protonophore carbonyl cyanide m-chlorophenylhydrazone, suggesting that the transmembrane pH gradient was not required for glutamate transport. The rate of glutamate transport increased with increasing glutamate concentration; the Km for glutamate was 2.90 μM, and the Vmax was 0.7 nmol · min−1 mg of protein. Glutamate transport was specifically inhibited by glutamate analogues. PMID:10322019

  19. Thin absorber EUV photomask based on mixed Ni and TaN material

    NASA Astrophysics Data System (ADS)

    Hay, Derrick; Bagge, Patrick; Khaw, Ian; Sun, Lei; Wood, Obert; Chen, Yulu; Kim, Ryoung-han; Qi, Zhengqing John; Shi, Zhimin

    2016-05-01

    Lithographic patterning at the 7 and 5 nm nodes will likely require EUV (λ=13.5 nm) lithography for many of the critical levels. All optical elements in an EUV scanner are reflective which requires the EUV photomask to be illuminated at an angle to its normal. Current scanners have an incidence of 6 degree, but future designs will be <6 degrees for high-NA systems. Non-telecentricity has been shown to cause H-V bias due to shadowing, pattern shift through focus, and image contrast lost due to apodization by the reflective mask coating. A thinner EUV absorber can dramatically reduce these issues. Ni offers better EUV absorption than Ta-based materials, which hold promise as a thinner absorber candidate. Unfortunately, the challenge of etching Ni has prevented its adoption into manufacturing. We propose a new absorber material that infuses Ni nanoparticles into the TaN host medium, allowing for the use of established Ta etching chemistry. A thinner is absorber is created due to the enhanced absorption properties of the Ni-Ta nano-composite material. Finite integral method and effective medium theory-based transfer matrix method have been independently developed to analyze the performance of the nano-composite absorption layer. We show that inserting 15% volume fraction Ni nanoparticles into 40-nm of TaN absorber material can reduce the reflection below 2% over the EUV range. Numerical simulations confirm that the reduced reflectivity is due to the increased absorption of Ni, while scattering only contributes to approximately 0.2% of the reduction in reflectivity.

  20. Cloning, functional characterization and heterologous expression of TaLsi1, a wheat silicon transporter gene.

    PubMed

    Montpetit, Jonatan; Vivancos, Julien; Mitani-Ueno, Namiki; Yamaji, Naoki; Rémus-Borel, Wilfried; Belzile, François; Ma, Jian Feng; Bélanger, Richard R

    2012-05-01

    Silicon (Si) is known to be beneficial to plants, namely in alleviating biotic and abiotic stresses. The magnitude of such positive effects is associated with a plant's natural ability to absorb Si. Many grasses can accumulate as much as 10% on a dry weight basis while most dicots, including Arabidopsis, will accumulate less than 0.1%. In this report, we describe the cloning and functional characterization of TaLsi1, a wheat Si transporter gene. In addition, we developed a heterologous system for the study of Si uptake in plants by introducing TaLsi1 and OsLsi1, its ortholog in rice, into Arabidopsis, a species with a very low innate Si uptake capacity. When expressed constitutively under the control of the CaMV 35S promoter, both TaLsi1 and OsLsi1 were expressed in cells of roots and shoots. Such constitutive expression of TaLsi1 or OsLsi1 resulted in a fourfold to fivefold increase in Si accumulation in transformed plants compared to WT. However, this Si absorption caused deleterious symptoms. When the wheat transporter was expressed under the control of a root-specific promoter (a boron transporter gene (AtNIP5;1) promoter), a similar increase in Si absorption was noted but the plants did not exhibit symptoms and grew normally. These results demonstrate that TaLsi1 is indeed a functional Si transporter as its expression in Arabidopsis leads to increased Si uptake, but that this expression must be confined to root cells for healthy plant development. The availability of this heterologous expression system will facilitate further studies into the mechanisms and benefits of Si uptake. PMID:22351076

  1. The Use of TaBoRR as a Heavy Oil Upgrader

    SciTech Connect

    Lee Brecher; Charles Mones

    2009-02-05

    Preliminary testing has shown that Western Research Institute's (WRI) Tank Bottom Recovery and Remediation (TaBoRR{reg_sign}) technology shows promise for heavy oil upgrading. Approximately 70 to 75 wt% of a Canadian Cold Lake bitumen feed was converted to a partially upgraded overhead product that could be transported directly by pipeline or blended with the parent bitumen to produce transportable crude. TaBoRR{reg_sign} was originally developed to remediate tank bottom wastes by producing a distillate product and solid waste. TaBoRR{reg_sign}'s processing steps include breaking a water-oil emulsion, recovering a light hydrocarbon fraction by distillation in a stripper unit, and pyrolyzing the residua reducing it to additional overhead and a benign coke for disposal. Cold Lake bitumen was tested in WRI's bench-scale equipment to evaluate the potential use of TaBoRR{reg_sign} technology for heavy oil upgrading to produce a stable, partially (or fully) upgraded product that will allow diluent-reduced or diluent-free transportation of bitumen or ultra-heavy crudes to market. Runs were conducted at temperatures of low, intermediate and high severity in the stripper to produce stripper overhead and bottoms. The bottoms from each of these runs were processed further in a 6-inch screw pyrolyzer to produce pyrolyzer overhead for blending with the corresponding stripper overheads. Proceeding in this fashion yielded three partially upgraded crudes. The products from TaBoRR{reg_sign} processing, the parent bitumen, and bitumen blends were subjected to stability and compatibility testing at the National Centre for Upgrading Technology (NCUT). Chemical analyses of the overhead product blends have met pipeline specifications for viscosity and density; however the bromine number does not, which might indicate the need for mild hydrotreating. Storage stability tests showed the blends to be stable. The blends were also soluble and compatible with most other Alberta crudes.

  2. Performance of the BG1Luc ER TA method in a qHTS format.

    PubMed

    Ceger, Patricia; Allen, David; Huang, Ruili; Xia, Menghang; Casey, Warren

    2015-01-01

    In 2012, the BG1Luc4E2 estrogen receptor (ER) transactivation (TA) method (BG1Luc ER TA) was accepted by U.S. regulatory agencies and the Organisation for Economic Co-operation and Development to detect substances with ER agonist activity. The method is now part of the Tier 1 testing battery in the Environmental Protection Agency's Endocrine Disruptor Screening Program. The BG1Luc ER TA method uses the BG1 ovarian cell line that endogenously expresses full-length ER (α and β) and is stably transfected with a plasmid containing four estrogen responsive elements upstream of a luciferase reporter gene. To allow increased throughput and testing efficiency, the BG1Luc ER TA ("BG1 manual") method was adapted for quantitative high-throughput screening (BG1 qHTS) in the U.S. Tox21 testing program. The BG1 qHTS test method was used to test approximately 10,000 chemicals three times each, and concentration-response data (n=15) were analyzed to evaluate test method performance. The balanced accuracy of the BG1 qHTS test method (97% [32/33]) was determined by comparing results to ER TA performance standards for the BG1 manual method. Concordance between the BG1 manual and qHTS methods was 92% (57/62) when calculated for a larger set of non-reference chemicals tested in both methods. These data demonstrate that the performance of the BG1 qHTS is similar to the currently accepted BG1 manual method, thereby establishing the utility of the BG1 qHTS method for identifying ER active environmental chemicals. PMID:26117232

  3. Transparent ALD-grown Ta2O5 protective layer for highly stable ZnO photoelectrode in solar water splitting.

    PubMed

    Li, Chengcheng; Wang, Tuo; Luo, Zhibin; Zhang, Dong; Gong, Jinlong

    2015-04-30

    This communication describes a highly stable ZnO/Ta2O5 photoanode with Ta2O5 deposited by atomic layer deposition. The ultrathin Ta2O5 protective layer prevents corrosion of ZnO and reduces surface carrier recombination, leading to a nearly two-fold increase of photo-conversion efficiency. The transparency of Ta2O5 to sunlight is identified as the main reason for the excellent stability of the photoelectrode for 5 hours.

  4. The wheat transcription factor TaGAMyb recruits histone acetyltransferase and activates the expression of a high-molecular-weight glutenin subunit gene.

    PubMed

    Guo, Weiwei; Yang, Hua; Liu, Yongqiang; Gao, Yujiao; Ni, Zhongfu; Peng, Huiru; Xin, Mingming; Hu, Zhaorong; Sun, Qixin; Yao, Yingyin

    2015-10-01

    Glutenin proteins in wheat (Triticum aestivum L.) flour confer unique viscoelastic properties to dough products and, therefore, the concentration and composition of the glutenin proteins determine its end-use value. However, the mechanisms governing the glutenin gene expression remain elusive. In this study, we report that wheat TaGAMyb activates the high-molecular-weight glutenin subunit genes (TaGLU) through recruiting the histone acetyltransferase GCN5. By sequencing the promoters of TaGLU-1 genes from 40 modern wheat cultivars, we identified eight types of TaGAMyb binding motifs and verified these by electrophoretic mobility shift assays. The number of TaGAMyb binding motifs in TaGLU-1 genes is correlated with the abundance of glutenin in different cultivars. Chromatin immunoprecipitation plus polymerase chain reaction (ChIP-PCR) analysis reveals that TaGCN5 directly targets the promoters of TaGLU-1 genes in wheat endosperm. We find that TaGAMyb physically interacts with the wheat histone acetyltransferase TaGCN5 and also interacts with Arabidopsis thaliana AtGCN5. TaGAMyb ectopically expressed in Arabidopsis binds to the TaGLU-1Dy promoter on a TaGLU-1Dy transgene and activates its expression. AtGCN5 also targets the TaGLU-1Dy transgene and is involved in the establishment of acetylation at H3K9 and H3K14. These results demonstrate that TaGAMyb plays a dual role in activating expression of glutenin gene by directly binding to the TaGLU promoter and by recruiting GCN5 to modulate histone acetylation during wheat endosperm development.

  5. Synergistic, additive, and antagonistic mutagenic responses to binary mixtures of benzo(a)pyrene and benzo(e)pyrene as detected by strains TA98 and TA100 in the Salmonella/microsome assay

    SciTech Connect

    Hass, B.S.; Brooks, E.E.; Schumann, K.E.; Dornfeld, S.S.

    1981-01-01

    Binary mixtures of benzo(a)pyrene (B(a)P) and benzo(e)pyrene (B(e)P) produce synergistic mutagenic (comutagenic) responses in Salmonella typhimurium strain TA98 (a frameshift detector). The optimum enhancement (25 X) was found at B(a)P concentration of 0.3 ..mu..g/plate and B(e)P concentration of 1.5 ..mu..g/plate. The response of strain TA100 (mostly a base-substitution detector) is opposite that of TA98, showing antagonism and additivity in similiar concentration ranges.

  6. TaTypA, a Ribosome-Binding GTPase Protein, Positively Regulates Wheat Resistance to the Stripe Rust Fungus.

    PubMed

    Liu, Peng; Myo, Thwin; Ma, Wei; Lan, Dingyun; Qi, Tuo; Guo, Jia; Song, Ping; Guo, Jun; Kang, Zhensheng

    2016-01-01

    Tyrosine phosphorylation protein A (TypA/BipA) belongs to the ribosome-binding GTPase superfamily. In many bacterial species, TypA acts as a global stress and virulence regulator and also mediates resistance to the antimicrobial peptide bactericidal permeability-increasing protein. However, the function of TypA in plants under biotic stresses is not known. In this study, we isolated and functionally characterized a stress-responsive TypA gene (TaTypA) from wheat, with three copies located on chromosomes 6A, 6B, and 6D, respectively. Transient expression assays indicated chloroplast localization of TaTypA. The transcript levels of TaTypA were up-regulated in response to treatment with methyl viologen, which induces reactive oxygen species (ROS) in chloroplasts through photoreaction, cold stress, and infection by an avirulent strain of the stripe rust pathogen. Knock down of the expression of TaTypA through virus-induced gene silencing decreased the resistance of wheat to stripe rust accompanied by weakened ROS accumulation and hypersensitive response, an increase in TaCAT and TaSOD expression, and an increase in pathogen hyphal growth and branching. Our findings suggest that TaTypA contributes to resistance in an ROS-dependent manner.

  7. Realization of a reversible switching in TaO{sub 2} polymorphs via Peierls distortion for resistance random access memory

    SciTech Connect

    Zhu, Linggang; Sun, Zhimei; Zhou, Jian; Guo, Zhonglu

    2015-03-02

    Transition-metal-oxide based resistance random access memory (RRAM) is a promising candidate for next-generation universal non-volatile memories. Searching and designing appropriate materials used in the memories becomes an urgent task. Here, a structure with the TaO{sub 2} formula was predicted using evolutionary algorithms in combination with first-principles calculations. This triclinic structure (T-TaO{sub 2}) is both energetically and dynamically more favorable than the commonly believed rutile structure (R-TaO{sub 2}). The metal-insulator transition (MIT) between metallic R-TaO{sub 2} and T-TaO{sub 2} (band gap: 1.0 eV) is via a Peierls distortion, which makes TaO{sub 2} a potential candidate for RRAM. The energy barrier for the reversible phase transition is 0.19 eV/atom and 0.23 eV/atom, respectively, suggesting low power consumption for the resistance switch. The present findings about the MIT as the resistance-switch mechanism in Ta-O system will stimulate experimental work to fabricate tantalum oxides based RRAM.

  8. Templated Non-Oxide Sol-Gel Preparation of Well-Ordered Macroporous (inverse opal) Ta3N5 Films

    PubMed Central

    2013-01-01

    Reactions of Ta(NMe2)5 and n-propylamine are shown to be an effective system for sol-gel processing of Ta3N5. Ordered macroporous films of Ta3N5 on silica substrates have been prepared by infiltration of such a sol into close-packed sacrificial templates of cross-linked 500 nm polystyrene spheres followed by pyrolysis under ammonia to remove the template and crystallize the Ta3N5. Templates with long-range order were produced by controlled humidity evaporation. Pyrolysis of a sol-infiltrated template at 600 °C removes the polystyrene but does not crystallize Ta3N5, and X-ray diffraction shows nanocrystalline TaN plus amorphous material. Heating at 700 °C crystallizes Ta3N5 while retaining a high degree of pore ordering, whereas at 800 °C porous films with a complete loss of order are obtained. PMID:23947333

  9. Templated non-oxide sol-gel preparation of well-ordered macroporous (inverse opal) Ta3N5 films.

    PubMed

    Mallinson, Christopher F; Gray, Benjamin M; Hector, Andrew L; McLachlan, Martyn A; Owen, John R

    2013-09-01

    Reactions of Ta(NMe2)5 and n-propylamine are shown to be an effective system for sol-gel processing of Ta3N5. Ordered macroporous films of Ta3N5 on silica substrates have been prepared by infiltration of such a sol into close-packed sacrificial templates of cross-linked 500 nm polystyrene spheres followed by pyrolysis under ammonia to remove the template and crystallize the Ta3N5. Templates with long-range order were produced by controlled humidity evaporation. Pyrolysis of a sol-infiltrated template at 600 °C removes the polystyrene but does not crystallize Ta3N5, and X-ray diffraction shows nanocrystalline TaN plus amorphous material. Heating at 700 °C crystallizes Ta3N5 while retaining a high degree of pore ordering, whereas at 800 °C porous films with a complete loss of order are obtained. PMID:23947333

  10. Color tone and interfacial microstructure of white oxide layer on commercially pure Ti and Ti-Nb-Ta-Zr alloys

    NASA Astrophysics Data System (ADS)

    Miura-Fujiwara, Eri; Mizushima, Keisuke; Watanabe, Yoshimi; Kasuga, Toshihiro; Niinomi, Mitsuo

    2014-11-01

    In this study, the relationships among oxidation condition, color tone, and the cross-sectional microstructure of the oxide layer on commercially pure (CP) Ti and Ti-36Nb-2Ta-3Zr-0.3O were investigated. “White metals” are ideal metallic materials having a white color with sufficient strength and ductility like a metal. Such materials have long been sought for in dentistry. We have found that the specific biomedical Ti alloys, such as CP Ti, Ti-36Nb-2Ta-3Zr-0.3O, and Ti-29Nb-13Ta-4.6Zr, form a bright yellowish-white oxide layer after a particular oxidation heat treatment. The brightness L* and yellowness +b* of the oxide layer on CP Ti and Ti-36Nb-2Ta-3Zr-0.3O increased with heating time and temperature. Microstructural observations indicated that the oxide layer on Ti-29Nb-13Ta-4.6Zr and Ti-36Nb-2Ta-3Zr-0.3O was dense and firm, whereas a piecrust-like layer was formed on CP Ti. The results obtained in this study suggest that oxide layer coating on Ti-36Nb-2Ta-3Zr-0.3O is an excellent technique for dental applications.

  11. TaTypA, a Ribosome-Binding GTPase Protein, Positively Regulates Wheat Resistance to the Stripe Rust Fungus.

    PubMed

    Liu, Peng; Myo, Thwin; Ma, Wei; Lan, Dingyun; Qi, Tuo; Guo, Jia; Song, Ping; Guo, Jun; Kang, Zhensheng

    2016-01-01

    Tyrosine phosphorylation protein A (TypA/BipA) belongs to the ribosome-binding GTPase superfamily. In many bacterial species, TypA acts as a global stress and virulence regulator and also mediates resistance to the antimicrobial peptide bactericidal permeability-increasing protein. However, the function of TypA in plants under biotic stresses is not known. In this study, we isolated and functionally characterized a stress-responsive TypA gene (TaTypA) from wheat, with three copies located on chromosomes 6A, 6B, and 6D, respectively. Transient expression assays indicated chloroplast localization of TaTypA. The transcript levels of TaTypA were up-regulated in response to treatment with methyl viologen, which induces reactive oxygen species (ROS) in chloroplasts through photoreaction, cold stress, and infection by an avirulent strain of the stripe rust pathogen. Knock down of the expression of TaTypA through virus-induced gene silencing decreased the resistance of wheat to stripe rust accompanied by weakened ROS accumulation and hypersensitive response, an increase in TaCAT and TaSOD expression, and an increase in pathogen hyphal growth and branching. Our findings suggest that TaTypA contributes to resistance in an ROS-dependent manner. PMID:27446108

  12. TaTypA, a Ribosome-Binding GTPase Protein, Positively Regulates Wheat Resistance to the Stripe Rust Fungus

    PubMed Central

    Liu, Peng; Myo, Thwin; Ma, Wei; Lan, Dingyun; Qi, Tuo; Guo, Jia; Song, Ping; Guo, Jun; Kang, Zhensheng

    2016-01-01

    Tyrosine phosphorylation protein A (TypA/BipA) belongs to the ribosome-binding GTPase superfamily. In many bacterial species, TypA acts as a global stress and virulence regulator and also mediates resistance to the antimicrobial peptide bactericidal permeability-increasing protein. However, the function of TypA in plants under biotic stresses is not known. In this study, we isolated and functionally characterized a stress-responsive TypA gene (TaTypA) from wheat, with three copies located on chromosomes 6A, 6B, and 6D, respectively. Transient expression assays indicated chloroplast localization of TaTypA. The transcript levels of TaTypA were up-regulated in response to treatment with methyl viologen, which induces reactive oxygen species (ROS) in chloroplasts through photoreaction, cold stress, and infection by an avirulent strain of the stripe rust pathogen. Knock down of the expression of TaTypA through virus-induced gene silencing decreased the resistance of wheat to stripe rust accompanied by weakened ROS accumulation and hypersensitive response, an increase in TaCAT and TaSOD expression, and an increase in pathogen hyphal growth and branching. Our findings suggest that TaTypA contributes to resistance in an ROS-dependent manner. PMID:27446108

  13. Atomic vapour deposition (AVD) of SrBi 2Ta 2O 9 using an all alkoxide precursor

    NASA Astrophysics Data System (ADS)

    Chalker, Paul R.; Potter, Richard J.; Roberts, John L.; Jones, Anthony C.; Smith, Lesley M.; Schumacher, Marcus

    2004-12-01

    A "single-source" Sr-Ta heterometal alkoxide precursor, Sr[Ta(OEt) 5(dmae)] 2 (dmae=OCH 2CH 2NMe 2), has been used for atomic vapour deposition (AVD) of SrBi 2Ta 2O 9 (SBT). This single-source precursor is designed to alleviate the mismatch between conventional Sr and Ta sources. Strontium tantalate thin films were deposited on silicon using the Sr[Ta(OEt) 5(dmae)] 2, and the optimum temperatures for deposition of strontium tantalate with a Sr:Ta ratio of 0.5 was found to be ˜510 °C. Deposition of Bi-oxide films using Bi(mmp) 3 (mmp=OCMe 2CH 2OMe) indicates similar decomposition behaviour to the Sr-Ta alkoxide precursor, demonstrating its suitability as a complementary source of Bi for SBT. The co-incorporation of Bi and Sr within the SBT films is promoted through the deposition of bismuth oxide/strontium tantalate super lattices. After post-growth annealing the super lattices are converted to strontium bismuth tantalate thin films.

  14. Memory window engineering of Ta2O5-x oxide-based resistive switches via incorporation of various insulating frames

    NASA Astrophysics Data System (ADS)

    Lee, Ah Rahm; Baek, Gwang Ho; Kim, Tae Yoon; Ko, Won Bae; Yang, Seung Mo; Kim, Jongmin; Im, Hyun Sik; Hong, Jin Pyo

    2016-07-01

    Three-dimensional (3D) stackable memory frames, including nano-scaled crossbar arrays, are one of the most reliable building blocks to meet the demand of high-density non-volatile memory electronics. However, their utilization has the disadvantage of introducing issues related to sneak paths, which can negatively impact device performance. We address the enhancement of complementary resistive switching (CRS) features via the incorporation of insulating frames as a generic approach to extend their use; here, a Pt/Ta2O5-x/Ta/Ta2O5-x/Pt frame is chosen as the basic CRS cell. The incorporation of Ta/Ta2O5-x/Ta or Pt/amorphous TaN/Pt insulting frames into the basic CRS cell ensures the appreciably advanced memory features of CRS cells including higher on/off ratios, improved read margins, and increased selectivity without reliability degradation. Experimental observations identified that a suitable insulating frame is crucial for adjusting the abrupt reset events of the switching element, thereby facilitating the enhanced electrical characteristics of CRS cells that are suitable for practical applications.

  15. ABI-like transcription factor gene TaABL1 from wheat improves multiple abiotic stress tolerances in transgenic plants.

    PubMed

    Xu, Dong-Bei; Gao, Shi-Qing; Ma, You-Zhi; Xu, Zhao-Shi; Zhao, Chang-Ping; Tang, Yi-Miao; Li, Xue-Yin; Li, Lian-Cheng; Chen, Yao-Feng; Chen, Ming

    2014-12-01

    The phytohormone abscisic acid (ABA) plays crucial roles in adaptive responses of plants to abiotic stresses. ABA-responsive element binding proteins (AREBs) are basic leucine zipper transcription factors that regulate the expression of downstream genes containing ABA-responsive elements (ABREs) in promoter regions. A novel ABI-like (ABA-insensitive) transcription factor gene, named TaABL1, containing a conserved basic leucine zipper (bZIP) domain was cloned from wheat. Southern blotting showed that three copies were present in the wheat genome. Phylogenetic analyses indicated that TaABL1 belonged to the AREB subfamily of the bZIP transcription factor family and was most closely related to ZmABI5 in maize and OsAREB2 in rice. Expression of TaABL1 was highly induced in wheat roots, stems, and leaves by ABA, drought, high salt, and low temperature stresses. TaABL1 was localized inside the nuclei of transformed wheat mesophyll protoplast. Overexpression of TaABL1 enhanced responses of transgenic plants to ABA and hastened stomatal closure under stress, thereby improving tolerance to multiple abiotic stresses. Furthermore, overexpression of TaABL1 upregulated or downregulated the expression of some stress-related genes controlling stomatal closure in transgenic plants under ABA and drought stress conditions, suggesting that TaABL1 might be a valuable genetic resource for transgenic molecular breeding.

  16. TaCIPK29, a CBL-interacting protein kinase gene from wheat, confers salt stress tolerance in transgenic tobacco.

    PubMed

    Deng, Xiaomin; Hu, Wei; Wei, Shuya; Zhou, Shiyi; Zhang, Fan; Han, Jiapeng; Chen, Lihong; Li, Yin; Feng, Jialu; Fang, Bin; Luo, Qingchen; Li, Shasha; Liu, Yunyi; Yang, Guangxiao; He, Guangyuan

    2013-01-01

    Calcineurin B-like protein-interacting protein kinases (CIPKs) have been found to be responsive to abiotic stress. However, their precise functions and the related molecular mechanisms in abiotic stress tolerance are not completely understood, especially in wheat. In the present study, TaCIPK29 was identified as a new member of CIPK gene family in wheat. TaCIPK29 transcript increased after NaCl, cold, methyl viologen (MV), abscisic acid (ABA) and ethylene treatments. Over-expression of TaCIPK29 in tobacco resulted in increased salt tolerance, which was demonstrated by higher germination rates, longer root lengths and better growth status of transgenic tobacco plants compared to controls when both were treated with salt stress. Physiological measurements indicated that transgenic tobacco seedlings retained high K(+)/Na(+) ratios and Ca(2+) content by up-regulating some transporter genes expression and also possessed lower H2O2 levels and reduced membrane injury by increasing the expression and activities of catalase (CAT) and peroxidase (POD) under salt stress. Moreover, transgenic lines conferred tolerance to oxidative stress by increasing the activity and expression of CAT. Finally, TaCIPK29 was located throughout cells and it preferentially interacted with TaCBL2, TaCBL3, NtCBL2, NtCBL3 and NtCAT1. Taken together, our results showed that TaCIPK29 functions as a positive factor under salt stress and is involved in regulating cations and reactive oxygen species (ROS) homeostasis.

  17. Effect of V and Ta on the precipitation behavior of 12%Cr reduced activation ferrite/martensite steel

    SciTech Connect

    Xiao, Xiang; Liu, Guoquan; Hu, Benfu; Wang, Jinsan; Ullah, Asad

    2013-08-15

    12%Cr reduced activation ferrite/martensite steels are promising candidate materials for good corrosion and irradiation resistance used for supercritical water-cooled reactor cladding and in-core components. V and Ta are considered to have improved the creep strength of high Cr steels by precipitating as MX phase. In this paper, a series of trial products microalloyed with V and V–Ta are produced, and the microstructure is characterized after quenching at 1050 °C and tempering at 780 °C by using TEM method to investigate the effect of these elements on the precipitation behavior of 12%Cr reduced activation ferrite/martensite steel. The results from both the experimental observations and thermodynamic and kinetic calculations reveal that V and V–Ta can promote the stable MX precipitation instead of M{sub 2}X, thus increasing the volume fraction of M{sub 23}C{sub 6}. Two-phase separation behavior of the (Ta, V)(C, N) carbonitride into a Ta(V)C(N) phase and a V(Ta)N(C) phase in 12Cr3WVTa steel is observed and further discussed. - Highlights: • Microalloyed with V and V-Ta can promote the precipitation of MX instead of M{sub 2}X. • The presence of delta-ferrite in microstructure affects the morphology of MX. • Two-phase separation of MX carbonitride was observed in 12Cr3WVTa steel.

  18. Laser Spectroscopy and AB Initio Calculations on the TaF Molecule

    NASA Astrophysics Data System (ADS)

    Ng, Kiu Fung; Zou, Wenli; Liu, Wenjian; Cheung, Allan S. C.

    2016-06-01

    Electronic transition spectrum of the tantalum monoflouride (TaF) molecule in the spectral region between 448 and 520 nm has been studied using the technique of laser-ablation/reaction free jet expansion and laser induced fluorescence spectroscopy. TaF molecule was produced by reacting laser-ablated tantalum atoms with sulfur hexafluoride gas seeded in argon. Sixteen vibrational bands with resolved rotational structure have been recorded and analyzed, which were organized into six electronic transition systems and the ground state has been identified to be the X3Σ-(0+) state with bond length, ro, and equilibrium vibrational frequency, ωe, determined to be 1.8209 Å and 700.1 wn respectively. In addition, four vibrational bands belong to another transition system involving lower state with Ω = 2 component has also been analyzed. All observed transitions are with ΔΩ = 0. Least-squares fit of the measured line positions yielded molecular constants for the electronic states involved. The Λ-S and Ω states of TaF were calculated at the state-averaged complete active space self-consistent field (SA-CASSCF) and the subsequent internally contracted multi-reference configuration interaction with singles and doubles and Davidson's cluster correction (MRCISD+Q) levels of theory with the active space of 4 electrons in 6 orbitals, that is, the molecular orbitals corresponding to Ta 5d6s are active. The spin-orbit coupling (SOC) is calculated by the state-interaction approach at the SA-CASSCF level via the relativistic effective core potentials (RECPs) spin-orbit operator, where the diagonal elements of the spin-orbit matrix are replaced by the above MRCISD+Q energies. The spectroscopic properties of the ground and many low-lying electronic states of the TaF molecule will be reported. With respect to the observed electronic states in this work, the calculated results are in good agreement with our experimental determinations. This work represents the first experimental

  19. Strength enhancement of Nicalon-reinforced lithium aluminosilicate containing a Ta(2)O(5) second phase

    NASA Astrophysics Data System (ADS)

    Villalobos, Guillermo R.

    The purpose of this study was to follow up the preliminary results of a previous thesis which appeared to indicate that the addition of Tasb2Osb5 to the matrix of a Nicalon fiber reinforced lithium aluminosilicate glass ceramic composite increased the mechanical properties of the resulting composites. The strength increase was attributed to the presence of a TaC platelet phase in the matrix material. The TaC was thought to be a result of the reaction between the Tasb2Osb5 additions and soluble CO from the hot press atmosphere used in the densification of the composites. These preliminary results (the strength increase and TaC formation) were a side experiment to a larger work and consequently were not rigorously investigated. The present work showed that the CO did react with Tasb2Osb5 to form TaC, but only as a surface coating. The surface coating reached a terminal thickness of 5-10 mum after 1 h at 1400sp°C. There was no evidence of soluble CO reacting to form TaC in the matrix. What was previously thought to be TaC platelets appears to be a two phase eutectic structure of beta-spodumene and Tasb2Osb5. When the Tasb2Osb5 content was increased to 15%, Tasb2Osb5 crystals were formed in addition to the eutectic structure. The formation of the eutectic structure could be suppressed in samples containing less than 3.5% Tasb2Osb5 by cooling at 10sp°C/min. Cooling rates of 1sp°C/min promoted the two phase structure. The interfacial shear strength and flexural strength did not appreciably increase with Tasb2Osb5 additions. Increasing the hot pressing time did increase the interfacial shear strength, but resulted in lower flexural strengths and less graceful failure modes. There was great variation in the flexural strength of the composites which increased with increasing Tasb2Osb5 content. With the very limited sample size of the preliminary study the large variation may have suggested a trend which did not statistically exist.

  20. Partial nitrogen loss in SrTaO2N and LaTiO2N oxynitride perovskites

    NASA Astrophysics Data System (ADS)

    Chen, Daixi; Habu, Daiki; Masubuchi, Yuji; Torii, Shuki; Kamiyama, Takashi; Kikkawa, Shinichi

    2016-04-01

    SrTaO2N heated in a helium atmosphere began to release nitrogen of approximately 30 at% at 950 °C while maintaining the perovskite structure and its color changed from orange to dark green. Then it decomposed above 1200 °C to a black mixture of Sr1.4Ta0.6O2.73, Ta2N, and Sr5Ta4O15. The second decomposition was not clearly observed when SrTaO2N was heated in a nitrogen atmosphere below 1550 °C. After heating at 1500 °C for 3 h under a 0.2 MPa nitrogen atmosphere, the perovskite product became dark green and conductive. Structure refinement results suggested that the product was a mixture of tetragonal and cubic perovskites with a decreased ordering of N3-/O2-. The sintered body was changed to an n-type semiconductor after a partial loss of nitrogen to be reduced from the originally insulating SrTaO2N perovskite lattice. LaTiO2N was confirmed to have a similar cis-configuration of the TiO4N2 octahedron as that of TaO4N2 in SrTaO2N. It also released some of its nitrogen at 800 °C changing its color from brown to black and then decomposed to a mixture of LaTiO3, La2O3, and TiN at 1100 °C. These temperatures are lower than those in SrTaO2N.

  1. Constitutive overexpression of the TaNF-YB4 gene in transgenic wheat significantly improves grain yield

    PubMed Central

    Yadav, Dinesh; Shavrukov, Yuri; Bazanova, Natalia; Chirkova, Larissa; Borisjuk, Nikolai; Kovalchuk, Nataliya; Ismagul, Ainur; Parent, Boris; Langridge, Peter; Hrmova, Maria; Lopato, Sergiy

    2015-01-01

    Heterotrimeric nuclear factors Y (NF-Ys) are involved in regulation of various vital functions in all eukaryotic organisms. Although a number of NF-Y subunits have been characterized in model plants, only a few have been functionally evaluated in crops. In this work, a number of genes encoding NF-YB and NF-YC subunits were isolated from drought-tolerant wheat (Triticum aestivum L. cv. RAC875), and the impact of the overexpression of TaNF-YB4 in the Australian wheat cultivar Gladius was investigated. TaNF-YB4 was isolated as a result of two consecutive yeast two-hybrid (Y2H) screens, where ZmNF-YB2a was used as a starting bait. A new NF-YC subunit, designated TaNF-YC15, was isolated in the first Y2H screen and used as bait in a second screen, which identified two wheat NF-YB subunits, TaNF-YB2 and TaNF-YB4. Three-dimensional modelling of a TaNF-YB2/TaNF-YC15 dimer revealed structural determinants that may underlie interaction selectivity. The TaNF-YB4 gene was placed under the control of the strong constitutive polyubiquitin promoter from maize and introduced into wheat by biolistic bombardment. The growth and yield components of several independent transgenic lines with up-regulated levels of TaNF-YB4 were evaluated under well-watered conditions (T1–T3 generations) and under mild drought (T2 generation). Analysis of T2 plants was performed in large deep containers in conditions close to field trials. Under optimal watering conditions, transgenic wheat plants produced significantly more spikes but other yield components did not change. This resulted in a 20–30% increased grain yield compared with untransformed control plants. Under water-limited conditions transgenic lines maintained parity in yield performance. PMID:26220082

  2. The Wheat GT Factor TaGT2L1D Negatively Regulates Drought Tolerance and Plant Development

    PubMed Central

    Zheng, Xin; Liu, Haipei; Ji, Hongtao; Wang, Youning; Dong, Baodi; Qiao, Yunzhou; Liu, Mengyu; Li, Xia

    2016-01-01

    GT factors are trihelix transcription factors that specifically regulate plant development and stress responses. Recently, several GT factors have been characterized in different plant species; however, little is known about the role of GT factors in wheat. Here, we show that TaGT2L1A, TaGT2L1B, and TaGT2L1D are highly homologous in hexaploid wheat, and are localized to wheat chromosomes 2A, 2B, and 2D, respectively. These TaGT2L1 genes encode proteins containing two SANT domains and one central helix. All three homologs were ubiquitously expressed during wheat development and were responsive to osmotic stress. Functional analyses demonstrated that TaGT2L1D acts as a transcriptional repressor; it was able to suppress the expression of AtSDD1 in Arabidopsis by binding directly to the GT3 box in its promoter that negatively regulates drought tolerance. TaGT2L1D overexpression markedly increased the number of stomata and reduced drought tolerance in gtl1-3 plants. Notably, ectopic expression of TaGT2L1D also affected floral organ development and overall plant growth. These results demonstrate that TaGT2L1 is an ortholog of AtGTL1, and that it plays an evolutionarily conserved role in drought resistance by fine tuning stomatal density in wheat. Our data also highlight the role of TaGT2L1 in plant growth and development. PMID:27245096

  3. The Wheat GT Factor TaGT2L1D Negatively Regulates Drought Tolerance and Plant Development.

    PubMed

    Zheng, Xin; Liu, Haipei; Ji, Hongtao; Wang, Youning; Dong, Baodi; Qiao, Yunzhou; Liu, Mengyu; Li, Xia

    2016-01-01

    GT factors are trihelix transcription factors that specifically regulate plant development and stress responses. Recently, several GT factors have been characterized in different plant species; however, little is known about the role of GT factors in wheat. Here, we show that TaGT2L1A, TaGT2L1B, and TaGT2L1D are highly homologous in hexaploid wheat, and are localized to wheat chromosomes 2A, 2B, and 2D, respectively. These TaGT2L1 genes encode proteins containing two SANT domains and one central helix. All three homologs were ubiquitously expressed during wheat development and were responsive to osmotic stress. Functional analyses demonstrated that TaGT2L1D acts as a transcriptional repressor; it was able to suppress the expression of AtSDD1 in Arabidopsis by binding directly to the GT3 box in its promoter that negatively regulates drought tolerance. TaGT2L1D overexpression markedly increased the number of stomata and reduced drought tolerance in gtl1-3 plants. Notably, ectopic expression of TaGT2L1D also affected floral organ development and overall plant growth. These results demonstrate that TaGT2L1 is an ortholog of AtGTL1, and that it plays an evolutionarily conserved role in drought resistance by fine tuning stomatal density in wheat. Our data also highlight the role of TaGT2L1 in plant growth and development. PMID:27245096

  4. Electronic and optical properties of TaO{sub 1-x}N{sub 1+x}-based alloys

    SciTech Connect

    Al-Aqtash, Nabil; Apostol, Florin; Mei, Wai-Ning; Sabirianov, Renat F.

    2013-02-15

    TaON is considered as a potential candidate as a visible-light responsive photocatalyst. We report the results of ab initio studies of electronic structure of TaON-based alloys. Specifically, we show that the position of conduction and valence band can be modified by varying the oxygen and nitrogen concentrations in TaO{sub 1-x}N{sub 1+x}. We find that the band gap decreases monotonically with the increase of N/O ratio. The band gap energy is decreased in monoclinic TaON from near 2.3 eV to just over 1.7 eV (i.e., by 35%) when N/O ratio is increased from 3/5 to 5/3. Our calculations show that the band gap reduces in a series of experimentally fabricated alloys ZrTa{sub 3}O{sub 5}N{sub 3}{yields}TaON{yields}YTa{sub 7}O{sub 7}N{sub 8}. The band gap reduction is mostly associated with the change in the position of the valence band due to the hybridization of N 2p states, while the conduction band consisting mostly of Ta 5d-states is not sensitive to N content. The calculated optical absorption spectra show reduction in the optical band gap with increasing N/O ratio. - Graphical abstract: Band gap energy of TaO{sub 1-x}N{sub 1+x} as a function of N/O ratio. Highlights: Black-Right-Pointing-Pointer The electronic and optical properties of TaON-based alloys are studied using DFT. Black-Right-Pointing-Pointer The position of conduction and valence bands can be modified by varying N/O ratio. Black-Right-Pointing-Pointer The band gap decreases monotonically with the increase of N/O ratio in TaO{sub 1-x}N{sub 1+x}. Black-Right-Pointing-Pointer The band gap reduces in a series of fabricated alloys ZrTa{sub 3}O{sub 5}N{sub 3}{yields}TaON{yields}YTa{sub 7}O{sub 7}N{sub 8}. Black-Right-Pointing-Pointer The optical band gap decreases with the increase of N/O ratio.

  5. Changes in the grassland-forest boundary at Ta-Ta-Chia long term ecological research (LTER) site detected by stable isotope ratios of soil organic matter.

    PubMed

    Chiang, Po Neng; Wang, Ming Kuang; Chiu, Chi Yu; King, Hen Biau; Hwong, Jeen Lian

    2004-01-01

    The carbon isotope analysis [delta13C values] of organic samples can be a useful research in ecological studies because delta13C values are indicative of the plant source. This study investigated the changes in plant communities along the grassland-forest boundary in the alpine forest at Ta-Ta-Chia long term ecological research (LTER) site in central Taiwan using carbon isotope data. The aim of this study was focused on the forest fire affected the change of vegetation community. Four pedons from grassland dominated by Miscanthus transmorrisonensis (pedons 1 and 2), transition zone by Tsuga and Yushania nittakeyamensis (pedon 3), and forest zone by Tsuga and nittakeyamensis (pedon 4) were examined. Soil organic matter (SOM) delta13C values in the upper soil horizon were similar to delta13C values of the overlaying vegetation types. This indicates that the boundary between these plant communities remained the same in the past decades. The delta13C values of the grassland SOM ranged from -19.4 per thousand to -24.1 per thousand, showing decrease with soil depth. This suggests that C4 plants (transmorrisonensis) have replaced C3 plants of Tsuga and nittakeyamensis. The delta13C values of the Tsuga forest area (pedon 4) range from -27.0 per thousand to -23.5 per thousand and showed only slight change with soil depth, implying that C3 plants have remained the major species in the forest. PMID:14559272

  6. Metallic to hopping conduction transition in Ta{sub 2}O{sub 5−x}/TaO{sub y} resistive switching device

    SciTech Connect

    Zhang, Ye; Deng, Ning; Yu, Zhiping; Zhang, Jinyu; Wu, Huaqiang Qian, He

    2014-08-11

    In this Letter, a comprehensive analysis of how the metallic behavior transition to hopping was presented by studying the transport mechanisms of low resistance states (LRS) in Ta{sub 2}O{sub 5−x}/TaO{sub y} resistive switching devices at very low temperatures. Three types of conduction behaviors were reported through temperature-dependent measurements ranging from 5 K to 250 K. Memory cells at low LRS show metallic behavior due to the formation of metallic filament. The temperature dependence of resistance at medium LRS exhibits an interesting phenomenon that a positive temperature coefficient transfers into a negative one at temperature of 20 K. Detailed analysis reveals that this phenomenon is caused by the coexistence of extended and localized states, with metallic conduction at higher temperatures and variable-range hopping at lower temperatures. Carrier transport at high LRS is dominated by electrons hopping conduction with nearest-neighboring hopping conduction changing into variable-range hopping as temperature decreases.

  7. The role of annealing temperature on the structural and magnetic consequences of Ta/PrFeB/Ta thin films processed by rapid thermal annealing

    NASA Astrophysics Data System (ADS)

    Ghasemi, Ali

    2016-04-01

    Ta/PrFeB/Ta thin films were deposited on CORNING 7059 by sputtering technique followed by rapid thermal annealing (RTA). The thickness of PrFeB was kept constant at 50 nm. The role of annealing temperature from 450 to 700 °C in a step of 50 °C for constant heating time of 60 s on the structural and magnetic consequences of thin films was studied by means of X-ray diffraction, field emission scanning electron microscopy, atomic force microscopy and vibrating sample magnetometer. The (00l) texture was almost fully developed at temperature of 650 °C and with an increase in temperature up to 700 °C the (105) peaks was also appeared in the patterns. The grains size and surface roughness of PrFeB films were increased by an increase in temperature. It was found that with an increase in temperature up to 500 °C the coercivity was developed and enhanced to 0.75 MA/m by further increasing of temperature to 650 °C. The maximum remanent-magnetization ratio and coercivity were obtained at temperature of 650 °C. The magnetization reversal process is accompanied by the combination of domain wall motion (DWM) and Stoner-Wohlfarth (S-W) rotation. However, for PrFeB films annealed at 550-700 °C it is closer to the S-W model than DWM modes.

  8. Analyzing topological defects in disordered charge density waves in transition-metal dichalcogenides TaSe2 and TaS2 using scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Schaper, Danielle; McElroy, Kyle; Calleja, Eduardo; Dai, Jixia; Li, Lijun; Lu, Wenjian; Sun, Yuping; Zhu, Xiangde

    2014-03-01

    Charged ordered states are becoming a common feature in the phase diagrams of correlated materials. In many cased there are indications that doping controlled quantum critical points between the CO state and others are related to interesting properties including superconductivity. An interesting test case is the ordered 2D CDW found in the transition metal dichalcogenides. We performed an analytical study on the dichalcogenides tantalum disulfide (TaS2) and tantalum diselenide (TaSe2) to observe how CDWs present in the material can be melted as disorder is introduced into the system via copper doping. Data was taken using a scanning tunneling microscope (STM) below the transition to the CDW state, both with and without copper dopants added. The resulting topographs were then analyzed to investigate the relationship between the phase and the amplitude of the disordered CDW. We found that the copper doping caused disorder in the CDW state characterized by phase wanderings and 2 π phase winding ``point defects'' in the CDW not present in the undoped parent compound. The locations of these point defects and windings were, in turn, found to have the characteristics of topological defects. Implications for studies of other disordered CO states seen in STM will be discussed.

  9. Molecular characterization of TaSTOP1 homoeologues and their response to aluminium and proton (H+) toxicity in bread wheat (Triticum aestivum L.)

    PubMed Central

    2013-01-01

    Background Aluminium (Al) toxicity is considered to be one of the major constraints affecting crop productivity on acid soils. Being a trait governed by multiple genes, the identification and characterization of novel transcription factors (TFs) regulating the expression of entire response networks is a very promising approach. Therefore, the aim of the present study was to clone, localize, and characterize the TaSTOP1 gene, which belongs to the zinc finger family (Cys2His2 type) transcription factor, at molecular level in bread wheat. Results TaSTOP1 loci were cloned and localized on the long arm of homoeologous group 3 chromosomes [3AL (TaSTOP1-A), 3BL (TaSTOP1-B) and 3DL (TaSTOP1-D)] in bread wheat. TaSTOP1 showed four potential zinc finger domains and the homoeologue TaSTOP1-A exhibited transactivation activity in yeast. Expression profiling of TaSTOP1 transcripts identified the predominance of homoeologue TaSTOP1-A followed by TaSTOP1-D over TaSTOP1-B in root and only predominance of TaSTOP1-A in shoot tissues of two diverse bread wheat genotypes. Al and proton (H+) stress appeared to slightly modulate the transcript of TaSTOP1 homoeologues expression in both genotypes of bread wheat. Conclusions Physical localization of TaSTOP1 results indicated the presence of a single copy of TaSTOP1 on homoeologous group 3 chromosomes in bread wheat. The three homoeologues of TaSTOP1 have similar genomic structures, but showed biased transcript expression and different response to Al and proton (H+) toxicity. These results indicate that TaSTOP1 homoeologues may differentially contribute under Al or proton (H+) toxicity in bread wheat. Moreover, it seems that TaSTOP1-A transactivation potential is constitutive and may not depend on the presence/absence of Al at least in yeast. Finally, the localization of TaSTOP1 on long arm of homoeologous group 3 chromosomes and the previously reported major loci associated with Al resistance at chromosome 3BL, through QTL and genome wide

  10. High-pressure Raman spectroscopy of perovskite oxynitride SrTaO2N

    NASA Astrophysics Data System (ADS)

    Son, Y.-G.; Jeong, I.-K.

    2016-09-01

    Perovskite oxynitrides exhibit emergent physical properties driven by a substitution of nitrogen for oxygen. The nitrogen substitution distorts the octahedra and induces octahedral tilting which are responsible for a relaxor-like temperature-insensitive dielectric response. To study the local structural evolution of oxynitride SrTaO2N under pressure, we performed in-situ high-pressure Raman spectroscopy measurements with a diamond anvil cell up to a pressure of P = 19 GPa. We find that forbidden modes were active, indicating a lowering of local symmetry from non-polar I4/mcm due to the octahedral distortion. Under pressure, a mode associated with TaO4N2 exhibits a negative wavenumber shift and merges with a nearby mode at a pressure of P ≃ 4.2 GPa. This result indicates a suppression of octahedral tilting under pressure.

  11. Study of the 1/2 (541) rotational band in sup 169 Ta

    SciTech Connect

    Yuan Guanjun; Li Guangsheng; Wen Shuxion; Li Shenggang; Hua Pengfei; Zhou Ling; Wu Ping; Zhang Lankuan; Yu Zhikang; Yu Panshui; Weng Peikun; Yang Chunxiang ); Mo, J.N. )

    1989-10-01

    The level scheme of the 1/2(541) band in {sup 169}Ta has been established using the {sup 155}Gd({sup 19}F, 5n) {sup 169}Ta reaction with beams provided by the HI-13 tandem accelerator of the IAE. The crossing frequency, corresponding to alignment of a pair of {ital i}{sub 13/2} quasineutrons for the 1/2(541) band is deduced to be 0.305 MeV {h bar} which is about 40 keV delayed in comparison with the Yrast band of its even-even neighbors. Cranked Shell Model calculations based on configuration-dependent deformation parameters are compared with the experimental results. The deformation-driving effects are discussed.

  12. Integration of microwave termination based on TaN thin films on ferrite substrates

    NASA Astrophysics Data System (ADS)

    Zhang, Dainan; Ji, Liang; Kolodzey, James

    2015-10-01

    Integration of microwave discrete devices such as isolators and circulators is highly desired for radar and communication platforms and in particular as components used in transmit and receive (T/R) modules. In those applications, Tantalum nitride (TaN) films are widely used as a surface mounted termination to improve the reliability and performance. In the current work, TaN thin films were directly deposited on polycrystalline ferrite substrate (Ni0.3Zn0.7Fe2O4) to be integrated with isolators or circulators. The deposition conditions were first optimized to obtain suitable sheet resistance and near zero temperature coefficients of resistance (TCR). Next a 50 Ω microwave termination was designed and fabricated using standard photolithography techniques. Broadband measurements show that the terminator has a low voltage standing wave ratio (VSWR) of less than 1.20 in the frequency range of DC-20 GHz. The measured resistance was between 48 and 54 Ω.

  13. Electrically driven reversible insulator-metal phase transition in 1T-TaS2.

    PubMed

    Hollander, Matthew J; Liu, Yu; Lu, Wen-Jian; Li, Li-Jun; Sun, Yu-Ping; Robinson, Joshua A; Datta, Suman

    2015-03-11

    In this work, we demonstrate abrupt, reversible switching of resistance in 1T-TaS2 using dc and pulsed sources, corresponding to an insulator-metal transition between the insulating Mott and equilibrium metallic states. This transition occurs at a constant critical resistivity of 7 mohm-cm regardless of temperature or bias conditions and the transition time is significantly smaller than abrupt transitions by avalanche breakdown in other small gap Mott insulating materials. Furthermore, this critical resistivity corresponds to a carrier density of 4.5 × 10(19) cm(-3), which compares well with the critical carrier density for the commensurate to nearly commensurate charge density wave transition. These results suggest that the transition is facilitated by a carrier driven collapse of the Mott gap in 1T-TaS2, which results in fast (3 ns) switching.

  14. Analysis of forming characteristics of Ta EFP according to material model

    NASA Astrophysics Data System (ADS)

    Kim, H. J.; Yi, Y. S.; Park, L. J.

    2015-09-01

    This paper presents numerical analysis result of forming characteristics of Ta explosively formed penetrator (EFP) according to various material models and their values. Dynamic material properties of Ta were measured with static tensile testing machine and Hopkinson pressure bar tests. We used AUTODYN hydrodynamic code to simulate these phenomena. We used three material models, such as Von-Mises model, linear hardening model and Johnson-Cook model. We also compared the numerical results with the EFP forming test data. The numerical results show that material model and its parameter are so important to predict the shape of formed penetrator and Von-Mises model predicts the shape of the formed liner most well. We also analysed the influence of liner thickness on EFP formation using the verified numerical model.

  15. TaIrTe4: A ternary type-II Weyl semimetal

    NASA Astrophysics Data System (ADS)

    Koepernik, K.; Kasinathan, D.; Efremov, D. V.; Khim, Seunghyun; Borisenko, Sergey; Büchner, Bernd; van den Brink, Jeroen

    2016-05-01

    In metallic condensed matter systems two different types of Weyl fermions can in principle emerge, with either a vanishing (type-I) or with a finite (type-II) density of states at the Weyl node energy. So far only WTe2 and MoTe2 were predicted to be type-II Weyl semimetals. Here we identify TaIrTe4 as a third member of this family of topological semimetals. TaIrTe4 has the attractive feature that it hosts only four well-separated Weyl points, the minimum imposed by symmetry. Moreover, the resulting topological surface states—Fermi arcs connecting Weyl nodes of opposite chirality—extend to about 1/3 of the surface Brillouin zone. This large momentum-space separation is very favorable for detecting the Fermi arcs spectroscopically and in transport experiments.

  16. Negative magnetoresistance without well-defined chirality in the Weyl semimetal TaP

    PubMed Central

    Arnold, Frank; Shekhar, Chandra; Wu, Shu-Chun; Sun, Yan; dos Reis, Ricardo Donizeth; Kumar, Nitesh; Naumann, Marcel; Ajeesh, Mukkattu O.; Schmidt, Marcus; Grushin, Adolfo G.; Bardarson, Jens H.; Baenitz, Michael; Sokolov, Dmitry; Borrmann, Horst; Nicklas, Michael; Felser, Claudia; Hassinger, Elena; Yan, Binghai

    2016-01-01

    Weyl semimetals (WSMs) are topological quantum states wherein the electronic bands disperse linearly around pairs of nodes with fixed chirality, the Weyl points. In WSMs, nonorthogonal electric and magnetic fields induce an exotic phenomenon known as the chiral anomaly, resulting in an unconventional negative longitudinal magnetoresistance, the chiral-magnetic effect. However, it remains an open question to which extent this effect survives when chirality is not well-defined. Here, we establish the detailed Fermi-surface topology of the recently identified WSM TaP via combined angle-resolved quantum-oscillation spectra and band-structure calculations. The Fermi surface forms banana-shaped electron and hole pockets surrounding pairs of Weyl points. Although this means that chirality is ill-defined in TaP, we observe a large negative longitudinal magnetoresistance. We show that the magnetoresistance can be affected by a magnetic field-induced inhomogeneous current distribution inside the sample. PMID:27186980

  17. Negative magnetoresistance without well-defined chirality in the Weyl semimetal TaP.

    PubMed

    Arnold, Frank; Shekhar, Chandra; Wu, Shu-Chun; Sun, Yan; Dos Reis, Ricardo Donizeth; Kumar, Nitesh; Naumann, Marcel; Ajeesh, Mukkattu O; Schmidt, Marcus; Grushin, Adolfo G; Bardarson, Jens H; Baenitz, Michael; Sokolov, Dmitry; Borrmann, Horst; Nicklas, Michael; Felser, Claudia; Hassinger, Elena; Yan, Binghai

    2016-01-01

    Weyl semimetals (WSMs) are topological quantum states wherein the electronic bands disperse linearly around pairs of nodes with fixed chirality, the Weyl points. In WSMs, nonorthogonal electric and magnetic fields induce an exotic phenomenon known as the chiral anomaly, resulting in an unconventional negative longitudinal magnetoresistance, the chiral-magnetic effect. However, it remains an open question to which extent this effect survives when chirality is not well-defined. Here, we establish the detailed Fermi-surface topology of the recently identified WSM TaP via combined angle-resolved quantum-oscillation spectra and band-structure calculations. The Fermi surface forms banana-shaped electron and hole pockets surrounding pairs of Weyl points. Although this means that chirality is ill-defined in TaP, we observe a large negative longitudinal magnetoresistance. We show that the magnetoresistance can be affected by a magnetic field-induced inhomogeneous current distribution inside the sample. PMID:27186980

  18. Thin absorber extreme ultraviolet photomask based on Ni-TaN nanocomposite material.

    PubMed

    Hay, Darrick; Bagge, Patrick; Khaw, Ian; Sun, Lei; Wood, Obert; Chen, Yulu; Kim, Ryoung-Han; Qi, Zhengqing John; Shi, Zhimin

    2016-08-15

    We study the use of random nanocomposite material as a photomask absorber layer for the next generation of extreme ultraviolet (EUV) lithography. By introducing nickel nanoparticles (NPs) randomly into a TaN host, the nanocomposite absorber layer can greatly reduce the reflectivity as compared with the standard TaN layer of the same thickness. Finite integral simulations show that the reduction in the reflectivity is mainly due to the enhanced absorption by the Ni NPs. The fluctuation in reflectivity induced by scattering and random position of the NPs is found to be on the order of 0.1%. Based on these observations, we build an effective medium model for the nanocomposite absorber layer and use the transfer matrix method to identify optimal absorber designs that utilize cavity effects to reduce the required volume fraction of Ni NPs. We further perform a process simulation and show that our approach can greatly reduce the HV bias in the lithography process. PMID:27519090

  19. Anomalous electronic structure and magnetoresistance in TaAs2

    SciTech Connect

    Luo, Yongkang; McDonald, R. D.; Rosa, P. F. S.; Scott, B.; Wakeham, N.; Ghimire, N. J.; Bauer, E. D.; Thompson, J. D.; Ronning, F.

    2016-01-01

    We report that the change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. In conclusion, density functional calculations find that TaAs2 is a new topological semimetal [Z2 invariant (0;111)] without Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions.

  20. Modified fused silicide coatings for tantalum (Ta-10W) reentry heat shields

    NASA Technical Reports Server (NTRS)

    Packer, C. M.; Perkins, R. A.

    1973-01-01

    Results are presented of a program of research to develop a reliable, high performance, fused slurry silicide coating for the Ta-10W alloy. The effort was directed toward developing new and improved formulations for use at 2600 to 2800 F (1700 to 1811 K) in an atmospheric reentry thermal protection system with a 100-mission capability. Based on a thorough characterization of isothermal and cyclic oxidation behavior, bend transition temperatures, room- and elevated-temperature tensile properties, and creep behavior, a 2.5 Mn-33Ti-64.5Si coating (designated MTS) provides excellent protection for the Ta-10W alloy in simulated reentry environments. An extensive analysis of the oxidation behavior and characteristics of the MTS coating in terms of fundamental mechanisms also is presented.

  1. Confinement of electromigration induced void propagation in Cu interconnect by a buried Ta diffusion barrier layer

    NASA Astrophysics Data System (ADS)

    Yan, M. Y.; Tu, K. N.; Vairagar, A. V.; Mhaisalkar, S. G.; Krishnamoorthy, Ahila

    2005-12-01

    Direct observation, by means of in situ scanning electron microscopy, of void heterogeneous nucleation and migration controlled electromigration failure mechanism in Cu dual damascene interconnect structures has been recently reported [A. V. Vairagar, S. G. Mhaisalkar, A. Krishnamoorthy, K. N. Tu, A. M. Gusak, M. A. Meyer, and E. Zschech, Appl. Phys. Lett. 85, 2502 (2004)] In the present study, a dual damascene structure with an additional 25nm Ta diffusion barrier embedded into the upper Cu layer was fabricated. This thin layer of diffusion barrier blocked voids from propagating into the via, thus eliminating the previously reported failure mechanism. With this structure, a lifetime improvement of at least 40 times was achieved. Analysis on failed samples suggested that failures in samples with the embedded Ta barrier layer occurred at the bottom of the via, which were caused by void migration along the bottom of the Cu lines.

  2. Negative magnetoresistance without well-defined chirality in the Weyl semimetal TaP

    NASA Astrophysics Data System (ADS)

    Arnold, Frank; Shekhar, Chandra; Wu, Shu-Chun; Sun, Yan; Dos Reis, Ricardo Donizeth; Kumar, Nitesh; Naumann, Marcel; Ajeesh, Mukkattu O.; Schmidt, Marcus; Grushin, Adolfo G.; Bardarson, Jens H.; Baenitz, Michael; Sokolov, Dmitry; Borrmann, Horst; Nicklas, Michael; Felser, Claudia; Hassinger, Elena; Yan, Binghai

    2016-05-01

    Weyl semimetals (WSMs) are topological quantum states wherein the electronic bands disperse linearly around pairs of nodes with fixed chirality, the Weyl points. In WSMs, nonorthogonal electric and magnetic fields induce an exotic phenomenon known as the chiral anomaly, resulting in an unconventional negative longitudinal magnetoresistance, the chiral-magnetic effect. However, it remains an open question to which extent this effect survives when chirality is not well-defined. Here, we establish the detailed Fermi-surface topology of the recently identified WSM TaP via combined angle-resolved quantum-oscillation spectra and band-structure calculations. The Fermi surface forms banana-shaped electron and hole pockets surrounding pairs of Weyl points. Although this means that chirality is ill-defined in TaP, we observe a large negative longitudinal magnetoresistance. We show that the magnetoresistance can be affected by a magnetic field-induced inhomogeneous current distribution inside the sample.

  3. Development and characterization of high temperature stable Ta-W-Si-C amorphous metal gates

    SciTech Connect

    Grubbs, Melody E.; Clemens, Bruce M.; Zhang Xiao; Deal, Michael; Nishi, Yoshio

    2010-11-29

    Threshold voltage variability ({sigma}{sub Vth}) due to the polycrystalline nature of current metal gates has been identified as a problem in future generations of complementary metal oxide semiconductor (CMOS) devices. Amorphous metal Ta{sub 40}W{sub 40}Si{sub 10}C{sub 10} gates are introduced in this work as a remedy. It was found that Ta-W-Si-C films remain amorphous at temperatures as high as 1120 deg. C, have n-type work functions, and are stable on HfO{sub 2}. This alloy is a promising gate-first compatible material that has the potential to significantly reduce {sigma}{sub Vth}.

  4. Isothermal transient ionic current as a characterization technique for ion transport in Ta2O5

    NASA Astrophysics Data System (ADS)

    Mattsson, M. Strømme; Niklasson, G. A.

    1999-06-01

    The Isothermal Transient Ionic Current (ITIC) technique was applied to β-Ta2O5 samples made by chemical vapor deposition. The mobility, conductivity, and number of protons in the material could be extracted from the measurements. Li ions were intercalated electrochemically into the β-Ta2O5 and it was found that the ITIC method could separate the contribution from proton and Li ion conduction in such a way that the mobilities of both species could be extracted. Furthermore, the lattice-gas model [A. J. Berlinsky, W. G. Unruh, W. R. McKinnon, and R. R. Haering, Solid State Commun. 31, 135 (1979)] was employed to describe the Li interaction process. This model showed that the Li ions tended to distribute uniformly, rather then to attract each other and form clusters in the material.

  5. Voltage divider effect for the improvement of variability and endurance of TaO(x) memristor.

    PubMed

    Kim, Kyung Min; Yang, J Joshua; Strachan, John Paul; Grafals, Emmanuelle Merced; Ge, Ning; Melendez, Noraica Davila; Li, Zhiyong; Williams, R Stanley

    2016-02-02

    The impact of a series resistor (R(S)) on the variability and endurance performance of memristor was studied in the TaO(x) memristive system. A dynamic voltage divider between the R(S) and memristor during both the set and the reset switching cycles can suppress the inherent irregularity of the voltage dropped on the memristor, resulting in a greatly reduced switching variability. By selecting the proper resistance value of R(S) for the set and reset cycles respectively, we observed a dramatically improved endurance of the TaO(x) memristor. Such a voltage divider effect can thus be critical for the memristor applications that require low variability, high endurance and fast speed.

  6. Spectroscopy of high index contrast Yb:Ta2O5 waveguides for lasing applications

    NASA Astrophysics Data System (ADS)

    Aghajani, A.; Murugan, G. S.; Sessions, N. P.; Apostolopoulos, V.; Wilkinson, J. S.

    2015-06-01

    Ytterbium-doped waveguides are required for compact integrated lasers and Yb- doped Ta2O5 is a promising candidate material. The design, fabrication and spectroscopic characterisation of Yb:Ta2O5 rib waveguides are described. The peak absorption cross-section was measured to be 2.75×10-20 cm2 at 975 nm. The emission spectrum was found to have a fluorescence emission peak at a wavelength of 976 nm with a peak cross-section of 2.9×10-20 cm2 and a second broad fluorescence band spanning from 990 nm to 1090 nm. The excited- state life time was measured to be 260 μs.

  7. Voltage divider effect for the improvement of variability and endurance of TaO(x) memristor.

    PubMed

    Kim, Kyung Min; Yang, J Joshua; Strachan, John Paul; Grafals, Emmanuelle Merced; Ge, Ning; Melendez, Noraica Davila; Li, Zhiyong; Williams, R Stanley

    2016-01-01

    The impact of a series resistor (R(S)) on the variability and endurance performance of memristor was studied in the TaO(x) memristive system. A dynamic voltage divider between the R(S) and memristor during both the set and the reset switching cycles can suppress the inherent irregularity of the voltage dropped on the memristor, resulting in a greatly reduced switching variability. By selecting the proper resistance value of R(S) for the set and reset cycles respectively, we observed a dramatically improved endurance of the TaO(x) memristor. Such a voltage divider effect can thus be critical for the memristor applications that require low variability, high endurance and fast speed. PMID:26830763

  8. Multiband Te p Based Superconductivity of Ta4Pd3Te16

    DOE PAGES

    Singh, David J.

    2014-10-06

    We recently discovered that Ta4Pd3Te16 is a superconductor that has been suggested to be an unconventional superconductor near magnetism. Here, we report electronic structure calculations showing that despite the layered crystal structure the material is an anisotropic three-dimensional (3D) metal. The Fermi surface contains prominent one-dimensional (1D) and two-dimensional (2D) features, including nested 1D sheets, a 2D cylindrical section, and a 3D sheet. Moreover, the electronic states that make up the Fermi surface are mostly derived from Te p states with small Ta d and Pd d contributions. This places the compound far from magnetic instabilities. The results are discussedmore » in terms of multiband superconductivity.« less

  9. TaDb: A time-aware diffusion-based recommender algorithm

    NASA Astrophysics Data System (ADS)

    Li, Wen-Jun; Xu, Yuan-Yuan; Dong, Qiang; Zhou, Jun-Lin; Fu, Yan

    2015-02-01

    Traditional recommender algorithms usually employ the early and recent records indiscriminately, which overlooks the change of user interests over time. In this paper, we show that the interests of a user remain stable in a short-term interval and drift during a long-term period. Based on this observation, we propose a time-aware diffusion-based (TaDb) recommender algorithm, which assigns different temporal weights to the leading links existing before the target user's collection and the following links appearing after that in the diffusion process. Experiments on four real datasets, Netflix, MovieLens, FriendFeed and Delicious show that TaDb algorithm significantly improves the prediction accuracy compared with the algorithms not considering temporal effects.

  10. Corrosion behavior of weldments of Ti and Ti-5Ta for nuclear fuel reprocessing plants

    SciTech Connect

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

    1995-12-01

    Corrosion studies on specimens of nuclear-grade type 304L stainless steel, titanium, Ti-5Ta, and their respective weldments were carried out in a boiling nitric acid medium, as well as in boiling nitric acid containing hexavalent chromium and divalent silver ions. The weldments were prepared using a tungsten inert gas welding process. Titanium and its weldment showed excellent corrosion resistance in both media compared to 304L stainless steel. Specimens of Ti-5Ta alloy base showed excellent corrosion resistance, whereas its weldment showed higher corrosion rates in boiling nitric acid medium. Scanning electron microscopy and x-ray diffraction analyses were carried out on the tested specimens to examine the scale morphology and the phases present on the surface.

  11. Resistivity plateau and negative magnetoresistance in the topological semimetal TaSb2

    NASA Astrophysics Data System (ADS)

    Li, Yuke; Li, Lin; Wang, Jialu; Wang, Tingting; Xu, Xiaofeng; Xi, Chuanying; Cao, Chao; Dai, Jianhui

    2016-09-01

    We report the discovery of a topological semimetal, TaSb2, which crystallizes in a base-centered monoclinic, centrosymmetric structure. The compound undergoes a metal-insulator-like transition under magnetic field and exhibits a clear resistivity plateau below Tc=13 K. The ultrahigh carrier mobility and extreme large magnetoresistance for longitudinal resistivity are observed at low temperatures in addition to a quantum oscillation behavior with nontrivial Berry phases. Moreover, the negative magnetoresistance is observed when the applied field is parallel to the current direction up to 9 T. The Hall resistivity shows the nearly linear field dependence suggestive of electron-hole noncompensation behavior. These findings uncover a materials basis represented by TaSb2 as a platform of topological materials for future theoretical and experimental investigations.

  12. A study of the elasticity of Ta at high temperature and pressure

    SciTech Connect

    Abramson, E H; Brown, J M; Hansen, D W; Ruddle, C M; Slutsky, L J; Zaug, J M

    1998-08-26

    The thermodynamic and transport properties of crystals and fluids at high temperature and pressure play a central role in the Earth and planetary sciences as well as in a variety of technologies and constitute a principal probe into the internuclear potential energy function at high density. Observation of surface waves by coherent time-domain optical spectroscopy provides an experimental approach to the determination, in the diamond-anvil high-pressure cell, of the elastic constants and thermal diffusivity of metal crystals as well as the equation of state and thermal transport properties of fluids. The electrical resistivities of metals may also be approximately accessible via the Wiedemann Franz Law. Preliminary results on Ta to pressures of 5.2 GPa are reported here. [Ta, elasticity, sound velocity, thermal diffusivity, equation of state].

  13. Temperature-dependent wear mechanisms for magnetron-sputtered AlTiTaN hard coatings.

    PubMed

    Khetan, Vishal; Valle, Nathalie; Duday, David; Michotte, Claude; Mitterer, Christian; Delplancke-Ogletree, Marie-Paule; Choquet, Patrick

    2014-09-10

    AlTiTaN coatings have been demonstrated to have high thermal stability at temperatures up to 900 °C. It has been speculated that the high oxidation resistance promotes an improved wear resistance, specifically for dry machining applications. This work reports on the influence of temperature up to 900 °C on the wear mechanisms of AlTiTaN hard coatings. DC magnetron-sputtered coatings were obtained from an Al(46)Ti(42)Ta(12) target, keeping the substrate bias at -100 V and the substrate temperature at 265 °C. The coatings exhibited a single-phase face-centered cubic AlTiTaN structure. The dry sliding tests revealed predominant abrasion and tribo-oxidation as wear mechanisms, depending on the wear debris formed. At room temperature, abrasion leading to surface polishing was observed. At 700 and 800 °C, slow tribo-oxidation and an amorphous oxide formed reduced the wear rate of the coating compared to room temperature. Further, an increase in temperature to 900 °C increased the wear rate significantly due to fast tribo-oxidation accompanied by grooving. The friction coefficient was found to decrease with temperature increasing from 700 to 900 °C due to the formation of oxide scales, which reduce adhesion of asperity contacts. A relationship between the oxidation and wear mechanisms was established using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, surface profilometry, confocal microscopy, and dynamic secondary ion mass spectrometry.

  14. Point defects stabilise cubic Mo-N and Ta-N

    NASA Astrophysics Data System (ADS)

    Koutná, Nikola; Holec, David; Svoboda, Ondřej; Klimashin, Fedor F.; Mayrhofer, Paul H.

    2016-09-01

    We employ ab initio calculations to investigate energetics of point defects in metastable rocksalt cubic Ta-N and Mo-N. Our results reveal a strong tendency to off-stoichiometry, i.e. defected structures are surprisingly predicted to be more stable than perfect ones with 1:1 metal-to-nitrogen stoichiometry. Despite the similarity of Ta-N and Mo-N systems in exhibiting this unusual behaviour, we also point out their crucial differences. While Ta-N significantly favours metal vacancies, Mo-N exhibits similar energies of formation regardless of the vacancy type (V Mo, V N) as long as their concentration is below ≈ 15~\\text{at}. % . The overall lowest energies of formation were obtained for \\text{T}{{\\text{a}}0.78}\\text{N} and \\text{M}{{\\text{o}}0.91}\\text{N} , which are hence predicted to be the most stable compositions. To account for various experimental conditions during synthesis, we further evaluated the phase stability as a function of chemical potential of individual species. The proposed phase diagrams reveal four stable compositions, \\text{M}{{\\text{o}}0.84}\\text{N} , \\text{M}{{\\text{o}}0.91}\\text{N} , \\text{Mo}{{\\text{N}}0.69} and \\text{Mo}{{\\text{N}}0.44} , in the case of Mo-N and nine stable compositions in the case of Ta-N indicating the important role of metal under-stoichiometry, since \\text{T}{{\\text{a}}0.75}\\text{N} and \\text{T}{{\\text{a}}0.78}\\text{N} significantly dominate the diagram. This is particularly important for understanding and designing experiments using non-equilibrium deposition techniques. Finally, we discuss the role of defect ordering and estimate a cubic lattice parameter as a function of defect contents and put them in the context of existing literature theoretical and experimental data.

  15. Interplay of charge density wave and multiband superconductivity in 2H-PdxTaSe2.

    PubMed

    Bhoi, D; Khim, S; Nam, W; Lee, B S; Kim, Chanhee; Jeon, B-G; Min, B H; Park, S; Kim, Kee Hoon

    2016-04-05

    2H-TaSe2 has been one of unique transition metal dichalcogenides exhibiting several phase transitions due to a delicate balance among competing electronic ground states. An unusual metallic state at high-T is sequentially followed by an incommensurate charge density wave (ICDW) state at ≈122 K and a commensurate charge density wave (CCDW) state at ≈90 K, and superconductivity at TC ~ 0.14 K. Upon systematic intercalation of Pd ions into TaSe2, we find that CCDW order is destabilized more rapidly than ICDW to indicate a hidden quantum phase transition point at x ~ 0.09-0.10. Moreover, TC shows a dramatic enhancement up to 3.3 K at x = 0.08, ~24 times of TC in 2H-TaSe2, in proportional to the density of states N(EF). Investigations of upper critical fields Hc2 in single crystals reveal evidences of multiband superconductivity as temperature-dependent anisotropy factor γH = , quasi-linear increase of , and an upward, positive-curvature in near TC. Furthermore, analysis of temperature-dependent electronic specific heat corroborates the presence of multiple superconducting gaps. Based on above findings and electronic phase diagram vs x, we propose that the increase of N(EF) and effective electron-phonon coupling in the vicinity of CDW quantum phase transition should be a key to the large enhancement of TC in PdxTaSe2.

  16. Assessment of relative Ti, Ta, and Nb (TITAN) enrichments in ocean island basalts

    NASA Astrophysics Data System (ADS)

    Peters, Bradley J.; Day, James M. D.

    2014-11-01

    sensitivity of trace element concentrations to processes governing solid-melt interactions has made them valuable tools for tracing the effects of partial melting, fractional crystallization, metasomatism, and similar processes on the composition of a parental melt. Recent studies of ocean island basalts (OIB) have sought to correlate Ti, Ta, and Nb (TITAN) anomalies to isotopic tracers, such as 3He/4He and 187Os/188Os ratios, which may trace primordial deep mantle sources. A new compilation of global OIB trace element abundance data indicates that positive TITAN anomalies, though statistically pervasive features of OIB, may not be compositional features of their mantle sources. OIB show a range of Ti (Ti/Ti* = 0.28-2.35), Ta (Ta/Ta* = 0.11-93.4), and Nb (Nb/Nb* = 0.13-17.8) anomalies that show negligible correlations with 3He/4He ratios, indicating that TITAN anomalies are not derived from the less-degassed mantle source traced by high-3He/4He. Positive TITAN anomalies can be modeled using variable degrees (0.1-10%) of nonmodal batch partial melting of garnet-spinel lherzolite at temperatures and pressures considered typical for OIB petrogenesis, and subjecting this partial melt to fractional crystallization and assimilation of mid-ocean ridge basalt-like crust (AFC). Correlations of TITAN anomalies with modal abundances of olivine and clinopyroxene in porphyritic Canary Islands lavas provide empirical support for this process and indicate that high abundances of these phases in OIB may create misleading trace element anomalies on primitive mantle-normalized spider diagrams. Because partial melting and AFC are common to all mantle-derived magmas, caution should be used when attributing TITAN anomalies to direct sampling of recycled or deep mantle sources by hotspots.

  17. Studies on weldability of Ti?5Ta?1.8Nb alloy

    NASA Astrophysics Data System (ADS)

    Karthikeyan, T.; Dasgupta, Arup; Saroja, S.; Vijayalakshmi, M.; Raghunathan, V. S.

    2004-12-01

    The welding, qualification and characterization of welds of Ti-5Ta-1.8Nb alloy, which is being developed for high corrosion resistant performance, are reported. Based on the studies performed as per the ASME Section IX standards, welding procedure specification and procedure qualification record have been formulated. The heterogeneous microstructures of the weldment are rationalized, based on phase transformation in the alloy system and differences in the thermal cycles of various microscopic regions.

  18. Preliminary results for HIP bonding Ta to W targets for the materials test station

    SciTech Connect

    Dombrowski, David E; Maloy, Stuart A

    2009-01-01

    Tungsten targets for the Materials Test Station (MTS) were clad with thin tantalum cover plates and a tantalum frame using hot isostatic pressing (HIP). A preliminary HIP parameter study showed good bonding and intimate mechanical contact for Ta cover plate thicknesses of 0.25 mm (0.010 inch) and 0.38 mm (0.015 inch). HIP temperatures of full HIP runs were 1500 C (2732 F). HIP pressure was 203 MPa (30 ksi).

  19. Interplay of charge density wave and multiband superconductivity in 2H-PdxTaSe2

    PubMed Central

    Bhoi, D.; Khim, S.; Nam, W.; Lee, B. S.; Kim, Chanhee; Jeon, B.-G.; Min, B. H.; Park, S.; Kim, Kee Hoon

    2016-01-01

    2H-TaSe2 has been one of unique transition metal dichalcogenides exhibiting several phase transitions due to a delicate balance among competing electronic ground states. An unusual metallic state at high-T is sequentially followed by an incommensurate charge density wave (ICDW) state at ≈122 K and a commensurate charge density wave (CCDW) state at ≈90 K, and superconductivity at TC ~ 0.14 K. Upon systematic intercalation of Pd ions into TaSe2, we find that CCDW order is destabilized more rapidly than ICDW to indicate a hidden quantum phase transition point at x ~ 0.09–0.10. Moreover, TC shows a dramatic enhancement up to 3.3 K at x = 0.08, ~24 times of TC in 2H-TaSe2, in proportional to the density of states N(EF). Investigations of upper critical fields Hc2 in single crystals reveal evidences of multiband superconductivity as temperature-dependent anisotropy factor γH = , quasi-linear increase of , and an upward, positive-curvature in near TC. Furthermore, analysis of temperature-dependent electronic specific heat corroborates the presence of multiple superconducting gaps. Based on above findings and electronic phase diagram vs x, we propose that the increase of N(EF) and effective electron-phonon coupling in the vicinity of CDW quantum phase transition should be a key to the large enhancement of TC in PdxTaSe2. PMID:27045426

  20. Overexpression of the pathogen-inducible wheat TaWRKY45 gene confers disease resistance to multiple fungi in transgenic wheat plants

    PubMed Central

    Bahrini, Insaf; Ogawa, Taiichi; Kobayashi, Fuminori; Kawahigashi, Hiroyuki; Handa, Hirokazu

    2011-01-01

    Recently we cloned and characterized the gene for the wheat transcription factor TaWRKY45 and showed that TaWRKY45 was upregulated in response to benzothiadiazole (BTH) and Fusarium head blight (FHB) and that its overexpression conferred enhanced resistance against F. graminearum. To characterize the functional role of TaWRKY45 in the disease resistance of wheat, in the present study we conducted expression analyses of TaWRKY45 with inoculations of powdery mildew and leaf rust and evaluated TaWRKY45-overexpressing wheat plants for resistance to these diseases. TaWRKY45 was upregulated in response to infections with Blumeria graminis, a causal fungus for powdery mildew, and Puccinia triticina, a causal fungus for leaf rust. Constitutive overexpression of the TaWRKY45 transgene conferred enhanced resistance against these two fungi on transgenic wheat plants grown under greenhouse conditions. However, the expression of two resistance-related genes, Pm3 and Lr34, was not induced by the inoculation with powdery mildew in TaWRKY45-overexpressing wheat plants. These results suggest that TaWRKY45 is involved in the defense responses for multiple fungal diseases in wheat but that resistance involving TaWRKY45 differs from at least Pm3 and/or Lr34-related resistance. Our present and previous studies indicate that TaWRKY45 may be potentially utilized to improve a wide range of disease resistance in wheat. PMID:23136468

  1. Isothermal oxidation behavior and microstructure of plasma surface Ta coating on γ-TiAl

    SciTech Connect

    Song, Jian; Zhang, Ping-Ze Wei, Dong-Bo; Wei, Xiang-Fei; Wang, Ya

    2014-12-15

    The oxidation behavior of γ-TiAl with Ta surface coating fabricated by double glow plasma surface alloying technology was investigated by thermogravimetric method. Oxidation experiments were carried out at 750 °C and 850 °C in air for 100 h. The modification layer was comprised of deposition layer and diffusion layer, which metallurgically adhered to the substrate. Tantalum element decreased with the case depth. The oxidation morphology was studied by a scanning electron microscope and X-ray diffraction. The results highlighted that in the oxidizing process of the oxidation, the phase containing Ta-richer may restrain diffusing outward of the element Al in the matrix. Ti diffused outward, and formed the TiO{sub 2} scales, while the middle layer was rich in Al, and formed the continuous Al{sub 2}O{sub 3} scales after oxidation, which was effective to prevent further infiltration of oxygen atoms, and as a result the oxidation resistance increased immensely. - Highlights: • A Ta modified coating was prepared on γ-TiAl using DGP surface alloying technology. • The modification layer metallurgically adhered to the substrate. • The bonding force is about 60 N, satisfying the demands of practical use. • The oxidation resistance increased immensely at 750 °C and 850 °C.

  2. Perpendicular magnetic tunnel junction with thin CoFeB/Ta/Co/Pd/Co reference layer

    SciTech Connect

    Gan, Huadong Malmhall, Roger; Wang, Zihui; Yen, Bing K; Zhang, Jing; Wang, Xiaobin; Zhou, Yuchen; Hao, Xiaojie; Jung, Dongha; Satoh, Kimihiro; Huai, Yiming

    2014-11-10

    Integration of high density spin transfer torque magnetoresistance random access memory requires a thin stack (less than 15 nm) of perpendicular magnetic tunnel junction (p-MTJ). We propose an innovative approach to solve this challenging problem by reducing the thickness and/or moment of the reference layer. A thin reference layer structure of CoFeB/Ta/Co/Pd/Co has 60% magnetic moment of the conventional thick structure including [Co/Pd] multilayers. We demonstrate that the perpendicular magnetization of the CoFeB/Ta/Co/Pd/Co structure can be realized by anti-ferromagnetically coupling to a pinned layer with strong perpendicular anisotropy via Ruderman-Kittel-Kasuya-Yosida exchange interaction. The pMTJ with thin CoFeB/Ta/Co/Pd/Co reference layer has a comparable TMR ratio (near 80%) as that with thick reference layer after annealing at 280 °C. The pMTJ with thin reference layer has a total thickness less than 15 nm, thereby significantly increasing the etching margin required for integration of high density pMTJ array on wafers with form factor of 300 mm and beyond.

  3. Pressure-induced amorphization of La{sub 1/3}TaO{sub 3}

    SciTech Connect

    Noked, O.; Melchior, A.; Shuker, R.; Livneh, T.; Steininger, R.; Kennedy, B.J.; Sterer, E.

    2013-06-15

    La{sub 1/3}TaO{sub 3}, an A-site cation deficient perovskite, has been studied under pressure by synchrotron X-ray powder diffraction and Raman spectroscopy. It undergoes irreversible pressure induced amorphization at P=18.5 GPa. An almost linear unit cell volume decrease vs. pressure is observed from ambient pressure up to the phase transition. The Raman spectroscopy also shows amorphization at the same pressure, with positive shifts of all modes as a function of pressure. The pressure dependence of the E{sub g} and A{sub 1g} Raman modes arising from the octahedral oxygen network is discussed. - Graphical abstract: La{sub 1/3}Tao{sub 3} exhibits linear pressure–volume relation until irreversible pressure induced amorphization at 18.5 Gpa. - Highlights: • La{sub 1/3}TaO{sub 3} has been studied under pressure by synchrotron XRD and Raman spectroscopy. • La{sub 1/3}TaO{sub 3} undergoes irreversible pressure induced amorphization around 18.5 GPa. • The transition is manifested in both XRD and Raman measurements. • A linear P–V relation is observed from ambient pressure up to the phase transition.

  4. Giant strain control of magnetoelectric effect in Ta|Fe|MgO.

    PubMed

    Odkhuu, Dorj

    2016-01-01

    The exploration of electric field controlled magnetism has come under scrutiny for its intriguing magnetoelectric phenomenon as well as technological advances in spintronics. Herein, the tremendous effect of an epitaxial strain on voltage-controlled perpendicular magnetic anisotropy (VPMA) is demonstrated in a transition-metal|ferromagnet|MgO (TM|FM|MgO) heterostructure from first-principles electronic structure computation. By tuning the epitaxial strain in Ta|Fe|MgO as a model system of TM|FM|MgO, we find distinctly different behaviours of VPMA from V- to Λ-shape trends with a substantially large magnetoelectric coefficient, up to an order of 10(3) fJV(-1)m(-1). We further reveal that the VPMA modulation under strain is mainly governed by the inherently large spin-orbit coupling of Ta 5d-Fe 3d hybridized orbitals at the TM|FM interface, although the Fe 3d-O 2p hybridization at the FM|MgO interface is partly responsible in determining the PMA of Ta|Fe|MgO. These results suggest that the control of epitaxial strain enables the engineering of VPMA, and provides physical insights for the divergent behaviors of VPMA and magnetoelectric coefficients found in TM|FM|MgO experiments. PMID:27597448

  5. Superconductor-Metal-Insulator transition in two dimensional Ta thin Films

    NASA Astrophysics Data System (ADS)

    Park, Sun-Gyu; Kim, Eunseong

    2013-03-01

    Superconductor-insulator transition has been induced by tuning film thickness or magnetic field. Recent electrical transport measurements of MoGe, Bi, Ta thin films revealed an interesting intermediate metallic phase which intervened superconducting and insulating phases at certain range of magnetic field. Especially, Ta thin films show the characteristic IV behavior at each phase and the disorder tuned intermediate metallic phase [Y. Li, C. L. Vicente, and J. Yoon, Physical Review B 81, 020505 (2010)]. This unexpected metallic phase can be interpreted as a consequence of vortex motion or contribution of fermionic quasiparticles. In this presentation, we report the scaling behavior during the transitions in Ta thin film as well as the transport measurements in various phases. Critical exponents v and z are obtained in samples with wide ranges of disorder. These results reveal new universality class appears when disorder exceeds a critical value. Dynamical exponent z of Superconducting sample is found to be 1, which is consistent with theoretical prediction of unity. z in a metallic sample is suddenly increased to be approximately 2.5. This critical exponent is much larger than the value found in other system and theoretical prediction. We gratefully acknowledge the financial support by the National Research Foundation of Korea through the Creative Research Initiatives.

  6. Experimental discovery of a topological Weyl semimetal state in TaP.

    PubMed

    Xu, Su-Yang; Belopolski, Ilya; Sanchez, Daniel S; Zhang, Chenglong; Chang, Guoqing; Guo, Cheng; Bian, Guang; Yuan, Zhujun; Lu, Hong; Chang, Tay-Rong; Shibayev, Pavel P; Prokopovych, Mykhailo L; Alidoust, Nasser; Zheng, Hao; Lee, Chi-Cheng; Huang, Shin-Ming; Sankar, Raman; Chou, Fangcheng; Hsu, Chuang-Han; Jeng, Horng-Tay; Bansil, Arun; Neupert, Titus; Strocov, Vladimir N; Lin, Hsin; Jia, Shuang; Hasan, M Zahid

    2015-11-01

    Weyl semimetals are expected to open up new horizons in physics and materials science because they provide the first realization of Weyl fermions and exhibit protected Fermi arc surface states. However, they had been found to be extremely rare in nature. Recently, a family of compounds, consisting of tantalum arsenide, tantalum phosphide (TaP), niobium arsenide, and niobium phosphide, was predicted as a Weyl semimetal candidates. We experimentally realize a Weyl semimetal state in TaP. Using photoemission spectroscopy, we directly observe the Weyl fermion cones and nodes in the bulk, and the Fermi arcs on the surface. Moreover, we find that the surface states show an unexpectedly rich structure, including both topological Fermi arcs and several topologically trivial closed contours in the vicinity of the Weyl points, which provides a promising platform to study the interplay between topological and trivial surface states on a Weyl semimetal's surface. We directly demonstrate the bulk-boundary correspondence and establish the topologically nontrivial nature of the Weyl semimetal state in TaP, by resolving the net number of chiral edge modes on a closed path that encloses the Weyl node. This also provides, for the first time, an experimentally practical approach to demonstrating a bulk Weyl fermion from a surface state dispersion measured in photoemission.

  7. Experimental discovery of a topological Weyl semimetal state in TaP

    PubMed Central

    Xu, Su-Yang; Belopolski, Ilya; Sanchez, Daniel S.; Zhang, Chenglong; Chang, Guoqing; Guo, Cheng; Bian, Guang; Yuan, Zhujun; Lu, Hong; Chang, Tay-Rong; Shibayev, Pavel P.; Prokopovych, Mykhailo L.; Alidoust, Nasser; Zheng, Hao; Lee, Chi-Cheng; Huang, Shin-Ming; Sankar, Raman; Chou, Fangcheng; Hsu, Chuang-Han; Jeng, Horng-Tay; Bansil, Arun; Neupert, Titus; Strocov, Vladimir N.; Lin, Hsin; Jia, Shuang; Hasan, M. Zahid

    2015-01-01

    Weyl semimetals are expected to open up new horizons in physics and materials science because they provide the first realization of Weyl fermions and exhibit protected Fermi arc surface states. However, they had been found to be extremely rare in nature. Recently, a family of compounds, consisting of tantalum arsenide, tantalum phosphide (TaP), niobium arsenide, and niobium phosphide, was predicted as a Weyl semimetal candidates. We experimentally realize a Weyl semimetal state in TaP. Using photoemission spectroscopy, we directly observe the Weyl fermion cones and nodes in the bulk, and the Fermi arcs on the surface. Moreover, we find that the surface states show an unexpectedly rich structure, including both topological Fermi arcs and several topologically trivial closed contours in the vicinity of the Weyl points, which provides a promising platform to study the interplay between topological and trivial surface states on a Weyl semimetal’s surface. We directly demonstrate the bulk-boundary correspondence and establish the topologically nontrivial nature of the Weyl semimetal state in TaP, by resolving the net number of chiral edge modes on a closed path that encloses the Weyl node. This also provides, for the first time, an experimentally practical approach to demonstrating a bulk Weyl fermion from a surface state dispersion measured in photoemission. PMID:26702446

  8. Development of Ta-based STJ X-ray Detector Arrays for Synchrotron Science

    NASA Astrophysics Data System (ADS)

    Carpenter, M. H.; Friedrich, S.; Hall, J. A.; Harris, J.; Cantor, R.

    2014-08-01

    We are developing a cryogen-free Ta-based superconducting tunnel junction (STJ) detector for soft X-ray spectroscopy at synchrotrons. With an energy resolution 10 times higher than conventional solid-state X-ray detectors and count-rate capabilities above 5 kHz/pixel, STJ detectors offer potentially increased sensitivity for fluorescence-yield X-ray absorption spectroscopy (FY-XAS). We have developed 36-pixel arrays of 208 208 m Ta STJs with an energy resolution of 9 eV FWHM at the 525 eV oxygen K line. Compared to earlier Nb-based STJs, Ta-STJs offer improved energy resolution and absorption efficiency and extend the operating range to several keV. Here we describe the integration of the 36-pixel arrays into a cryogen-free, user-friendly X-ray spectrometer. A computer-controlled adiabatic demagnetization refrigerator coupled to a two-stage pulse tube refrigerator allows operation below 100 mK. The detector chip is located at the end of a 42 cm shielded snout for insertion into the analysis chamber. The system is currently being commissioned at the Advanced Light Source synchrotron.

  9. Conduction mechanism of a TaOx-based selector and its application in crossbar memory arrays

    NASA Astrophysics Data System (ADS)

    Wang, Ming; Zhou, Jiantao; Yang, Yuchao; Gaba, Siddharth; Liu, Ming; Lu, Wei D.

    2015-03-01

    The conduction mechanism of a Pd/TaOx/Ta/Pd selector device, which exhibits high non-linearity (~104) and excellent uniformity, has been systematically investigated by current-voltage-temperature characterization. The measurement and simulation results indicate two dominant processes of selector current at opposite biases: thermionic emission and tunnel emission. The current-voltage-temperature behaviors of the selector can be well explained using the Simmons' trapezoidal energy barrier model. The TaOx-based selective layer was further integrated with a HfO2-based resistive switching layer to form a selector-less resistive random access memory (RRAM) device structure. The integrated device showed a reliable resistive switching behavior with a high non-linearity (~5 × 103) in the low resistance state (LRS), which can effectively mitigate the sneak path current issue in RRAM crossbar arrays. Evaluations of a crossbar array based on these selector-less RRAM cells show less than 4% degradation in read margin for arrays up to 1 Mbit in size. These results highlight the different conduction mechanisms in selector device operation and will provide insight into continued design and optimization of RRAM arrays.

  10. Giant nonreciprocal emission of spin waves in Ta/Py bilayers.

    PubMed

    Kwon, Jae Hyun; Yoon, Jungbum; Deorani, Praveen; Lee, Jong Min; Sinha, Jaivardhan; Lee, Kyung-Jin; Hayashi, Masamitsu; Yang, Hyunsoo

    2016-07-01

    Spin waves are propagating disturbances in the magnetization of magnetic materials. One of their interesting properties is nonreciprocity, exhibiting that their amplitude depends on the magnetization direction. Nonreciprocity in spin waves is of great interest in both fundamental science and applications because it offers an extra knob to control the flow of waves for the technological fields of logics and switch applications. We show a high nonreciprocity in spin waves from Ta/Py bilayer systems with out-of-plane magnetic fields. The nonreciprocity depends on the thickness of Ta underlayer, which is found to induce an interfacial anisotropy. The origin of observed high nonreciprocity is twofold: different polarities of the in-plane magnetization due to different angles of canted out-of-plane anisotropy and the spin pumping effect at the Ta/Py interface. Our findings provide an opportunity to engineer highly efficient, nonreciprocal spin wave-based applications, such as nonreciprocal microwave devices, magnonic logic gates, and information transports. PMID:27419231

  11. Pressure-induced phase transitions of β-type pyrochlore CsTaWO6

    DOE PAGES

    Zhang, F. X.; Tracy, C. L.; Shamblin, J.; Palomares, R. I.; Lang, M.; Park, S.; Park, C.; Tkachev, S.; Ewing, R. C.

    2016-09-30

    The β-type pyrochlore CsTaWO6 was studied by synchrotron X-ray diffraction (XRD) and Raman scattering methods up to pressures of 43 GPa using a diamond anvil cell (DAC). With increasing pressure, the cubic pyrochlore in space group of Fd-3¯m with combining macron]m transforms to an orthorhombic structure (space group: Pnma) at 5.9 GPa and then to a monoclinic structure (space group: P21/c) at ~18 GPa. The structural evolution in CsTaWO6 is a continuous process and experimental results suggest that the initial cubic phase has a tetragonal distortion at ambient conditions. Both XRD and Raman measurements indicate that the pressure-induced phase transitionsmore » in CsTaWO6 are reversible. Lastly, these results may provide a structural explanation of previous experimental resistivity measurement results for the isostructural superconductor K(Cs)Os2O6 at high pressure conditions.« less

  12. THERMAL STABILITY AND MECHANICAL BEHAVIOR OF ULTRA-FINE BCC TA AND V COATINGS

    SciTech Connect

    Jankowski, A F; Go, J; Hayes, J P

    2006-11-03

    Ultra-refined microstructures of both tantalum (Ta) and vanadium (V) are produced using electron-beam evaporation and magnetron sputtering deposition. The thermal stability of the micron-to-submicron grain size foils is examined to quantify the kinetics and activation energy of diffusion, as well as identify the temperature transition in dominant mechanism from grain boundary to lattice diffusion. The activation energies for boundary diffusion in Ta and V determined from grain growth are 0.3 and 0.2 eV{center_dot}atom{sup -1}, respectively, versus lattice diffusion values of 4.3 and 3.2 eV{center_dot}atom{sup -1}, respectively. The mechanical behavior, as characterized by strength and hardness, is found to inversely scale with square-root grain size according to the Hall-Petch relationship. The strength of Ta and V increases two-fold from 400 MPa, as the grain size decreases from 2 to 0.75 {micro}m.

  13. π Berry phase and Zeeman splitting of Weyl semimetal TaP

    PubMed Central

    Hu, J.; Liu, J. Y.; Graf, D.; Radmanesh, S. M. A.; Adams, D. J.; Chuang, A.; Wang, Y.; Chiorescu, I.; Wei, J.; Spinu, L.; Mao, Z. Q.

    2016-01-01

    The recent breakthrough in the discovery of Weyl fermions in monopnictide semimetals provides opportunities to explore the exotic properties of relativistic fermions in condensed matter. The chiral anomaly-induced negative magnetoresistance and π Berry phase are two fundamental transport properties associated with the topological characteristics of Weyl semimetals. Since monopnictide semimetals are multiple-band systems, resolving clear Berry phase for each Fermi pocket remains a challenge. Here we report the determination of Berry phases of multiple Fermi pockets of Weyl semimetal TaP through high field quantum transport measurements. We show our TaP single crystal has the signatures of a Weyl state, including light effective quasiparticle masses, ultrahigh carrier mobility, as well as negative longitudinal magnetoresistance. Furthermore, we have generalized the Lifshitz-Kosevich formula for multiple-band Shubnikov-de Haas (SdH) oscillations and extracted the Berry phases of π for multiple Fermi pockets in TaP through the direct fits of the modified LK formula to the SdH oscillations. In high fields, we also probed signatures of Zeeman splitting, from which the Landé g-factor is extracted. PMID:26726050

  14. π Berry phase and Zeeman splitting of Weyl semimetal TaP.

    PubMed

    Hu, J; Liu, J Y; Graf, D; Radmanesh, S M A; Adams, D J; Chuang, A; Wang, Y; Chiorescu, I; Wei, J; Spinu, L; Mao, Z Q

    2016-01-01

    The recent breakthrough in the discovery of Weyl fermions in monopnictide semimetals provides opportunities to explore the exotic properties of relativistic fermions in condensed matter. The chiral anomaly-induced negative magnetoresistance and π Berry phase are two fundamental transport properties associated with the topological characteristics of Weyl semimetals. Since monopnictide semimetals are multiple-band systems, resolving clear Berry phase for each Fermi pocket remains a challenge. Here we report the determination of Berry phases of multiple Fermi pockets of Weyl semimetal TaP through high field quantum transport measurements. We show our TaP single crystal has the signatures of a Weyl state, including light effective quasiparticle masses, ultrahigh carrier mobility, as well as negative longitudinal magnetoresistance. Furthermore, we have generalized the Lifshitz-Kosevich formula for multiple-band Shubnikov-de Haas (SdH) oscillations and extracted the Berry phases of π for multiple Fermi pockets in TaP through the direct fits of the modified LK formula to the SdH oscillations. In high fields, we also probed signatures of Zeeman splitting, from which the Landé g-factor is extracted. PMID:26726050

  15. Current hysteresis by oxygen vacancy exchange between oxides in Pt/a-IGZO/TaOx/W

    NASA Astrophysics Data System (ADS)

    Kwon, Hyeon-Min; Kim, Myeong-Ho; Lee, Seung-Ryul; Kim, Young-Bae; Choi, Duck-Kyun

    2014-02-01

    ReRAM (resistance random access memory) has been receiving attention as the next-generation memory owing to advantages such as fast switching-speed, low power consumption, and simple structure. However, in order to improve the properties of the candidate materials that show resistive switching phenomenon, it is essential to understand the resistive switching mechanism. This study was conducted to investigate the switching mechanism of a ReRAM device with Pt/a-IGZO (amorphous In-Ga-Zn-O)/TaOx/Al2O3/W structure that exhibits useful properties such as forming free and self-rectifying properties in addition to the general memory properties of existing ReRAM devices. Based on a series of designed experiments and analysis, it was found that the current hysteresis in this device is based on the oxygen vacancy exchange between a-IGZO and TaOx. The movement of positively charged oxygen vacancy according to the relative polarity of applied voltage between the two oxides induces the resistance change of TaOx layer, which in turn results in the resistive switching.

  16. Large unsaturated positive and negative magnetoresistance in Weyl semimetal TaP

    NASA Astrophysics Data System (ADS)

    Du, JianHua; Wang, HangDong; Chen, Qin; Mao, QianHui; Khan, Rajwali; Xu, BinJie; Zhou, YuXing; Zhang, YanNan; Yang, JinHu; Chen, Bin; Feng, ChunMu; Fang, MingHu

    2016-05-01

    After successfully growing single-crystal TaP, we measured its longitudinal resistivity ( ρ xx ) and Hall resistivity ( ρ yx ) at magnetic fields up to 9 T in the temperature range of 2-300 K. At 8 T, the magnetoresistance (MR) reached 3.28 × 105% at 2 K, 176% at 300 K. Neither value appeared saturated. We confirmed that TaP is a hole-electron compensated semimetal with a low carrier concentration and high hole mobility of μ h=3.71 × 105 cm2/V s, and found that a magnetic-field-induced metal-insulator transition occurs at room temperature. Remarkably, because a magnetic field ( H) was applied in parallel to the electric field ( E), a negative MR due to a chiral anomaly was observed and reached -3000% at 9 T without any sign of saturation, either, which is in contrast to other Weyl semimetals (WSMs). The analysis of the Shubnikov-de Haas (SdH) oscillations superimposed on the MR revealed that a nontrivial Berry's phase with a strong offset of 0.3958, which is the characteristic feature of charge carriers enclosing a Weyl node. These results indicate that TaP is a promising candidate not only for revealing fundamental physics of the WSM state but also for some novel applications.

  17. Osteoblast cell behavior on the new beta-type Ti-25Ta-25Nb alloy.

    PubMed

    Cimpean, Anisoara; Mitran, Valentina; Ciofrangeanu, Cristina M; Galateanu, Bianca; Bertrand, Emmanuel; Gordin, Doina-Margareta; Iordachescu, Dana; Gloriant, Thierry

    2012-08-01

    Among metallic materials used as bone substitutes, β titanium alloys gain an increasing importance because of their low modulus, high corrosion resistance and good biocompatibility. In this work, an investigation of the in vitro cytocompatibility of a recently new developed β-type Ti-25Ta-25Nb alloy was carried out by evaluating the behavior of human osteoblasts. The metallic Ti-6Al-4V biomaterial, which is one of representative α+β type titanium alloys for biomedical applications, and Tissue Culture Polystyrene (TCPS), were also investigated as reference Ti-based material and control substrate, respectively. Both metallic surfaces were analyzed by X-ray diffraction, atomic force microscopy and X-ray photoelectron spectroscopy. The cellular response was quantified by assessments of viability, cell attachment and spreading, cell morphology, production and extracellular organization of fibronectin and cell proliferation. Polished surfaces from both materials having an equiaxed grain microstructure and nanometre scale surface roughness elicited an essentially identical osteoblast response in terms of all analyzed cellular parameters. Thus, on both surfaces the cells displayed high survival rates, good cell adhesion and spreading, a dense and randomly dispersed fibronectin matrix and increasing cell proliferation rates over the incubation time. Furhermore, the enhanced biological performance of Ti-25Ta-25Nb was highly supported by the results obtained in comparison with TCPS. These findings, together with previously shown superelastic behavior, low Young's modulus and high corrosion resistance, recommend Ti-25Ta-25Nb as good candidate for applications in bone implantology.

  18. First-principles investigation of vacancies in LiTaO3

    NASA Astrophysics Data System (ADS)

    He, Wenhao; Gao, Xing; Pang, Lilong; Wang, Dong; Gao, Ning; Wang, Zhiguang

    2016-08-01

    Formation energies of neutral and charged vacancies in lithium tantalate, as well as their electronic states have been investigated through first-principles calculations. It is found out that V\\text{O}2+ , V\\text{Li}1- and V\\text{Ta}5- are the most energy favorable vacancies on O, Li and Ta sites respectively. The formation energy of vacancy on the O site is lower in oxygen poor environments than that in oxygen rich environments, and the formation energy of vacancy on the cation site is lower in oxygen rich environments than that in oxygen poor environments. Among all types of neutral vacancies considered in this study, the energy of Li partial Schottky reaction, 2V\\text{Li}1-   +  V\\text{O}2+ , is the lowest at almost all considered chemical environments. Taking into account the distribution of vacancy induced energy levels, we suggest that either V\\text{O}0 or V\\text{O}1+ is responsible for the light absorption band around 460 nm observed in annealed LiTaO3 crystal.

  19. Large magnetoresistance induced by crystallographic defects in FexTaS2 single crystals

    NASA Astrophysics Data System (ADS)

    Chen, Chih-Wei; Morosan, Emilia; Morosan's Group Team

    The search for the materials that show large magnetoresistance and the mechanisms that induce it remains challenging in both experimental and theoretical aspects. The giant magnetoresistance in one class of materials, ferromagnetic conductors, is generally attributed to the misalignments of magnetic moments, which cause spin disorder scattering. Recently, very large magnetoresistance (>60 %) was discovered in the ferromagnetic Fe-intercalated transition metal dichalcogenide, Fe0.28TaS2 [Phys. Rev. B 91, 054426(2015)]. The mechanism that led to this large magnetoresistance was suggested to be due to the deviation of Fe concentration from commensurate values (1/4 or 1/3), which caused magnetic moments' misalignments. Here we report a study of FexTaS2 crystals with x close to the commensurate values. Our results qualitatively demonstrate that crystallographic defects significantly affect magnetoresistance in FexTaS2. This provides a way to search for large magnetoresistance in more intercalated transition metal dichalcogenides. This work is supported by the Department of Defense PECASE.

  20. Charge transport properties of bulk Ta3N5 from first principles

    NASA Astrophysics Data System (ADS)

    Morbec, Juliana M.; Galli, Giulia

    2016-01-01

    Tantalum nitride is considered a promising material for photoelectrochemical water splitting, however, its charge transport properties remain poorly understood. We investigated polaronic and band transport in Ta3N5 using first-principles calculations. We first studied the formation of small polarons using density-functional theory (DFT) including DFT +U and hybrid functionals. We found that electron small polarons may occur but hole polarons are not energetically favorable. The estimated polaronic mobility for electrons is at least three orders of magnitude smaller than that measured in Ta3N5 films, suggesting that the main transport mechanism for both electrons and holes is bandlike. Since band transport is strongly affected by the carrier effective masses, and Ta3N5 is known to have large electron and hole effective masses, we also investigated whether substitutional impurities or strain may help lower the effective masses. We found a significant reduction in both electron and hole effective masses (up to 17% for electrons and 39% for holes) under applied strain, which may lead to a substantial improvement (up to 30% for electrons and 15% for holes) in the carrier mobilities.

  1. Influence of Ta content in high purity niobium on cavity performance

    SciTech Connect

    P. Kneisel; G. Ciovati; G. R. Myneni; W. Singer; X. Singer; D. Proch; T. Carneiro

    2005-05-01

    In a previous paper [1] we have reported about initial tests of single cell 1500 MHz cavities made from high purity niobium with three different Ta contents of 160 ppm , {approx}600 ppm and {approx}1400 ppm. These cavities had been treated by buffered chemical polishing several times and 100 {micro}m, 200 {micro}m and 300 {micro}m of material had been removed from the surfaces. This contribution reports about subsequent tests following post purification heat treatments with Ti and ''in situ'' baking. As a result, all cavities exhibited increased quench fields due to the improved thermal conductivity after the heat treatment. After the ''in situ'' baking at 120 C for {approx} 40 hrs the always present Q-drop at high fields disappeared and further improvements in accelerating gradient could be realized. Gradients as high as E{sub acc} = 35 MV/m were achieved and there were no clear indications that the cavity performance was influenced by the Ta content in the material. A multi-cell cavity from the high Ta content material has been fabricated and initial results are reported.

  2. Photo-degradation of methylene blue using Ta-doped ZnO nanoparticle

    SciTech Connect

    Kong Jizhou; Li Aidong; Li Xiangyu; Zhai Haifa; Zhang Wenqi; Gong Youpin; Li Hui; Wu Di

    2010-06-15

    A photocatalyst of Ta-doped ZnO was prepared by a modified Pechini-type method. The structural, morphological properties and photocatalytic activity of 1 mol % Ta-doped ZnO samples annealed at different temperatures were characterized. The photo-oxidation of methylene blue under the visible-light irradiation followed the pseudo-first-order kinetics according to the Langmuir-Hinshelwood model. It is found that the photocatalysis of 1% Ta-doped ZnO annealed at 700 {sup o}C showed excellent performance of the photodegradation of methylene blue, which was attributed to a competitive trade-off among the crystallinity, surface hydroxyl groups, and specific surface area. The processing parameter such as the pH value also played an important role in tuning the photocatalytic activity. The maximum photodecomposed rate was achieved at pH=8, and an novel model about the absorption of methylene blue on the surface of the catalysts was proposed. - Graphical abstract: This model describes the adsorption between the amphoteric behavior of the metal oxide and the cationic dye methylene blue (MB) on the surface of the catalyst at the acidic and alkaline condition.

  3. Optimization of Urea-EnFET Based on Ta2O5 Layer with Post Annealing

    PubMed Central

    Lue, Cheng-En; Yu, Ting-Chun; Yang, Chia-Ming; Pijanowska, Dorota G.; Lai, Chao-Sung

    2011-01-01

    In this study, the urea-enzymatic field effect transistors (EnFETs) were investigated based on pH-ion sensitive field effect transistors (ISFETs) with tantalum pentoxide (Ta2O5) sensing membranes. In addition, a post N2 annealing was used to improve the sensing properties. At first, the pH sensitivity, hysteresis, drift, and light induced drift of the ISFETs were evaluated. After the covalent bonding process and urease immobilization, the urea sensitivity of the EnFETs were also investigated and compared with the conventional Si3N4 sensing layer. The ISFETs and EnFETs with annealed Ta2O5 sensing membranes showed the best responses, including the highest pH sensitivity (56.9 mV/pH, from pH 2 to pH 12) and also corresponded to the highest urea sensitivity (61 mV/pCurea, from 1 mM to 7.5 mM). Besides, the non-ideal factors of pH hysteresis, time drift, and light induced drift of the annealed samples were also lower than the controlled Ta2O5 and Si3N4 sensing membranes. PMID:22163862

  4. Characterization of NaTaO3 synthesized by ultrasonic method.

    PubMed

    Vázquez-Cuchillo, O; Manzo-Robledo, A; Zanella, R; Elizondo-Villareal, N; Cruz-López, A

    2013-01-01

    NaTaO(3) perovskite-like materials were synthesized using sodium acetate and tantalum ethoxide as precursors in an ultrasonic bath at room temperature. The pristine sample was thermally treated at 600 °C and characterized using XRD, N(2) physisorption, DRS, SEM and TEM techniques. The structural characterization by X-ray powder diffraction revealed that the crystallization of the NaTaO(3) phase prepared at 600 °C showed agglomerates sizes in the micrometric scale, as confirmed by scanning electron microscopy (SEM). On the other hand, well-defined NaTaO(3) particles in the nanometric scale were determined using TEM. It was found that, for the treated sample, the band gap and BET area was 3.8 eV and 9.5m(2) g(-1), respectively. The annealed perovskite, deposited onto ITO glass, presented an important variation in the open circuit potential transient during UV light irradiation in neutral solution, compared with its counterpart prepared by solid-state method. These intrinsic properties, given by the preparation route, might be appropriate for increase its photocatalytic activity.

  5. Direct Metal Deposition of Refractory High Entropy Alloy MoNbTaW

    NASA Astrophysics Data System (ADS)

    Dobbelstein, Henrik; Thiele, Magnus; Gurevich, Evgeny L.; George, Easo P.; Ostendorf, Andreas

    Alloying of refractory high entropy alloys (HEAs) such as MoNbTaW is usually done by vacuum arc melting (VAM) or powder metallurgy (PM) due to the high melting points of the elements. Machining to produce the final shape of parts is often needed after the PM process. Casting processes, which are often used for aerospace components (turbine blades, vanes), are not possible. Direct metal deposition (DMD) is an additive manufacturing technique used for the refurbishment of superalloy components, but generating these components from the bottom up is also of current research interest. MoNbTaW possesses high yield strength at high temperatures and could be an alternative to state-of-the-art materials. In this study, DMD of an equimolar mixture of elemental powders was performed with a pulsed Nd:YAG laser. Single wall structures were built, deposition strategies developed and the microstructure of MoNbTaW was analyzed by back scattered electrons (BSE) and energy dispersive X-ray (EDX) spectroscopy in a scanning electron microscope. DMD enables the generation of composition gradients by using dynamic powder mixing instead of pre-alloyed powders. However, the simultaneous handling of several elemental or pre-alloyed powders brings new challenges to the deposition process. The influence of thermal properties, melting point and vapor pressure on the deposition process and chemical composition will be discussed.

  6. Giant strain control of magnetoelectric effect in Ta|Fe|MgO

    NASA Astrophysics Data System (ADS)

    Odkhuu, Dorj

    2016-09-01

    The exploration of electric field controlled magnetism has come under scrutiny for its intriguing magnetoelectric phenomenon as well as technological advances in spintronics. Herein, the tremendous effect of an epitaxial strain on voltage-controlled perpendicular magnetic anisotropy (VPMA) is demonstrated in a transition-metal|ferromagnet|MgO (TM|FM|MgO) heterostructure from first-principles electronic structure computation. By tuning the epitaxial strain in Ta|Fe|MgO as a model system of TM|FM|MgO, we find distinctly different behaviours of VPMA from V- to Λ-shape trends with a substantially large magnetoelectric coefficient, up to an order of 103 fJV‑1m‑1. We further reveal that the VPMA modulation under strain is mainly governed by the inherently large spin-orbit coupling of Ta 5d–Fe 3d hybridized orbitals at the TM|FM interface, although the Fe 3d–O 2p hybridization at the FM|MgO interface is partly responsible in determining the PMA of Ta|Fe|MgO. These results suggest that the control of epitaxial strain enables the engineering of VPMA, and provides physical insights for the divergent behaviors of VPMA and magnetoelectric coefficients found in TM|FM|MgO experiments.

  7. Resistance to He2+ irradiation damage in metallic glass Ta38Ni62

    NASA Astrophysics Data System (ADS)

    Hou, Wenjing; Mei, Xianxiu; Zhang, Xiaonan; Wang, Yingmin; Qiang, Jianbing; Sun, Jianrong; Wang, Younian

    2016-10-01

    Metallic glass Ta38Ni62 strips, metallic W, and V87.5Cr4.17Ti4.17Nb4.17 alloy were irradiated using a 500 keV He2+ ion beam at different fluence to compare the metallic glass resistance to irradiation. Metallic glass Ta38Ni62 remained amorphous at different He2+ irradiation fluence. Transmission electron microscopy analysis revealed the presence of helium bubbles at the end of the range of helium ions in the metallic glass. No significant damage resulted in the metallic glass surface, and the root mean square roughness increased nonlinearly with the increase in fluence. At 1 × 1018 ions/cm2, metallic W appeared in larger sunken areas on the surface and V87.5Cr4.17Ti4.17Nb4.17 alloy experienced multi-layer flaking. The metallic glass Ta38Ni62 resistance to He2+ ion beam irradiation was better than that of metallic W, and that of the V87.5Cr4.17Ti4.17Nb4.17 alloy was the poorest.

  8. Characterization of NaTaO3 synthesized by ultrasonic method.

    PubMed

    Vázquez-Cuchillo, O; Manzo-Robledo, A; Zanella, R; Elizondo-Villareal, N; Cruz-López, A

    2013-01-01

    NaTaO(3) perovskite-like materials were synthesized using sodium acetate and tantalum ethoxide as precursors in an ultrasonic bath at room temperature. The pristine sample was thermally treated at 600 °C and characterized using XRD, N(2) physisorption, DRS, SEM and TEM techniques. The structural characterization by X-ray powder diffraction revealed that the crystallization of the NaTaO(3) phase prepared at 600 °C showed agglomerates sizes in the micrometric scale, as confirmed by scanning electron microscopy (SEM). On the other hand, well-defined NaTaO(3) particles in the nanometric scale were determined using TEM. It was found that, for the treated sample, the band gap and BET area was 3.8 eV and 9.5m(2) g(-1), respectively. The annealed perovskite, deposited onto ITO glass, presented an important variation in the open circuit potential transient during UV light irradiation in neutral solution, compared with its counterpart prepared by solid-state method. These intrinsic properties, given by the preparation route, might be appropriate for increase its photocatalytic activity. PMID:22981167

  9. Phenobarbital: does the positive result in TA1535 indicate genotoxic properties?

    PubMed

    Albertini, S; Gocke, E

    1992-01-01

    The liver carcinogen phenobarbital (PB) causes a weak but reproducible increase of the mutant frequency in the Ames test, strain TA1535, without S9. Since there is no obvious chemical basis for a "DNA reactivity" of this compound experiments were performed to obtain information about possible indirect mechanisms of enhancing the number of spontaneous mutant colonies. In the course of the study strong synergistic and comutagenic effects of PB when given in combination with Na-azide or 2-aminoanthracene (2AA) were observed. Not only TA1535 but the complete set of tester strains was responsive. However, PB did not enhance the effects of other mutagens such as 4-nitroquinoline N-oxide or 2-nitrofluorene. It is argued that in strain TA1535 the fixation and expression of spontaneously occurring DNA lesions is amenable to modulation by PB similar to that of Na-azide or 2AA induced lesions. Thus in the usual sense, PB is not genotoxic in the Ames test. Methapyrilene, another liver carcinogen with an assumed nongenotoxic mode of action, showed almost identical properties in these experiments. PMID:1541257

  10. Regulation study for the facility control system design at the Facility Operations Center at TA55

    SciTech Connect

    1994-03-16

    NMT-8 is proposing to upgrade the existing Facility Control System (FCS) located within the Facility Operations Center (FOC) at the TA-55 Plutonium Processing and Handling Facility (PPHF). The FCS modifications will upgrade the existing electronics to provide better reliability of system functions. Changes include replacement of the FCS computers and field multiplex units which are used for transmitting systems data. Data collected at the FCS include temperature, pressure, contact closures, etc., and are used for monitoring and/or control of key systems at TA-55. Monitoring is provided for the electrical power system status, PF-4 HVAC air balance status (Static Differential pressure), HVAC fan system status, site chill water return temperature, fire system information, and radioactive constant air monitors alarm information, site compressed air pressure and other key systems used at TA-55. Control output signals are provided for PF-4 HVAC systems, and selected alarms for criticality, fire, loss of pressure in confinement systems. A detailed description of the FCS modifications is provided in Section 2.

  11. Optimization of urea-EnFET based on Ta2O5 layer with post annealing.

    PubMed

    Lue, Cheng-En; Yu, Ting-Chun; Yang, Chia-Ming; Pijanowska, Dorota G; Lai, Chao-Sung

    2011-01-01

    In this study, the urea-enzymatic field effect transistors (EnFETs) were investigated based on pH-ion sensitive field effect transistors (ISFETs) with tantalum pentoxide (Ta(2)O(5)) sensing membranes. In addition, a post N(2) annealing was used to improve the sensing properties. At first, the pH sensitivity, hysteresis, drift, and light induced drift of the ISFETs were evaluated. After the covalent bonding process and urease immobilization, the urea sensitivity of the EnFETs were also investigated and compared with the conventional Si(3)N(4) sensing layer. The ISFETs and EnFETs with annealed Ta(2)O(5) sensing membranes showed the best responses, including the highest pH sensitivity (56.9 mV/pH, from pH 2 to pH 12) and also corresponded to the highest urea sensitivity (61 mV/pC(urea), from 1 mM to 7.5 mM). Besides, the non-ideal factors of pH hysteresis, time drift, and light induced drift of the annealed samples were also lower than the controlled Ta(2)O(5) and Si(3)N(4) sensing membranes. PMID:22163862

  12. Giant strain control of magnetoelectric effect in Ta|Fe|MgO

    PubMed Central

    Odkhuu, Dorj

    2016-01-01

    The exploration of electric field controlled magnetism has come under scrutiny for its intriguing magnetoelectric phenomenon as well as technological advances in spintronics. Herein, the tremendous effect of an epitaxial strain on voltage-controlled perpendicular magnetic anisotropy (VPMA) is demonstrated in a transition-metal|ferromagnet|MgO (TM|FM|MgO) heterostructure from first-principles electronic structure computation. By tuning the epitaxial strain in Ta|Fe|MgO as a model system of TM|FM|MgO, we find distinctly different behaviours of VPMA from V- to Λ-shape trends with a substantially large magnetoelectric coefficient, up to an order of 103 fJV−1m−1. We further reveal that the VPMA modulation under strain is mainly governed by the inherently large spin-orbit coupling of Ta 5d–Fe 3d hybridized orbitals at the TM|FM interface, although the Fe 3d–O 2p hybridization at the FM|MgO interface is partly responsible in determining the PMA of Ta|Fe|MgO. These results suggest that the control of epitaxial strain enables the engineering of VPMA, and provides physical insights for the divergent behaviors of VPMA and magnetoelectric coefficients found in TM|FM|MgO experiments. PMID:27597448

  13. Experimental discovery of a topological Weyl semimetal state in TaP.

    PubMed

    Xu, Su-Yang; Belopolski, Ilya; Sanchez, Daniel S; Zhang, Chenglong; Chang, Guoqing; Guo, Cheng; Bian, Guang; Yuan, Zhujun; Lu, Hong; Chang, Tay-Rong; Shibayev, Pavel P; Prokopovych, Mykhailo L; Alidoust, Nasser; Zheng, Hao; Lee, Chi-Cheng; Huang, Shin-Ming; Sankar, Raman; Chou, Fangcheng; Hsu, Chuang-Han; Jeng, Horng-Tay; Bansil, Arun; Neupert, Titus; Strocov, Vladimir N; Lin, Hsin; Jia, Shuang; Hasan, M Zahid

    2015-11-01

    Weyl semimetals are expected to open up new horizons in physics and materials science because they provide the first realization of Weyl fermions and exhibit protected Fermi arc surface states. However, they had been found to be extremely rare in nature. Recently, a family of compounds, consisting of tantalum arsenide, tantalum phosphide (TaP), niobium arsenide, and niobium phosphide, was predicted as a Weyl semimetal candidates. We experimentally realize a Weyl semimetal state in TaP. Using photoemission spectroscopy, we directly observe the Weyl fermion cones and nodes in the bulk, and the Fermi arcs on the surface. Moreover, we find that the surface states show an unexpectedly rich structure, including both topological Fermi arcs and several topologically trivial closed contours in the vicinity of the Weyl points, which provides a promising platform to study the interplay between topological and trivial surface states on a Weyl semimetal's surface. We directly demonstrate the bulk-boundary correspondence and establish the topologically nontrivial nature of the Weyl semimetal state in TaP, by resolving the net number of chiral edge modes on a closed path that encloses the Weyl node. This also provides, for the first time, an experimentally practical approach to demonstrating a bulk Weyl fermion from a surface state dispersion measured in photoemission. PMID:26702446

  14. Resistivity plateau and extremely large magnetoresistance in NbAs2 and TaAs2

    NASA Astrophysics Data System (ADS)

    Wang, Yi-Yan; Yu, Qiao-He; Guo, Peng-Jie; Liu, Kai; Xia, Tian-Long

    2016-07-01

    In topological insulators (TIs), metallic surface conductance saturates the insulating bulk resistance with decreasing temperature, resulting in resistivity plateau at low temperatures as a transport signature originating from metallic surface modes protected by time reversal symmetry (TRS). Such a characteristic has been found in several materials including Bi2Te2Se , SmB6 etc. Recently, similar behavior has been observed in metallic compound LaSb, accompanying an extremely large magnetoresistance (XMR). Shubnikov-de Hass (SdH) oscillation at low temperatures further confirms the metallic behavior of the plateau region under magnetic fields. LaSb [Tafti et al., Nat. Phys. 12, 272 (2015), 10.1038/nphys3581] has been proposed by the authors as a possible topological semimetal (TSM), while negative magnetoresistance is absent at this moment. Here, high quality single crystals of NbAs2/TaAs2 with inversion symmetry have been grown, and the resistivity under magnetic field is systematically investigated. Both of them exhibit metallic behavior under zero magnetic field, and a metal-to-insulator transition occurs when a nonzero magnetic field is applied, resulting in XMR (1.0 ×105% for NbAs2 and 7.3 ×105% for TaAs2 at 2.5 K and 14 T). With temperature decreased, a resistivity plateau emerges after the insulatorlike regime, and SdH oscillation has also been observed in NbAs2 and TaAs2.

  15. Giant nonreciprocal emission of spin waves in Ta/Py bilayers

    PubMed Central

    Kwon, Jae Hyun; Yoon, Jungbum; Deorani, Praveen; Lee, Jong Min; Sinha, Jaivardhan; Lee, Kyung-Jin; Hayashi, Masamitsu; Yang, Hyunsoo

    2016-01-01

    Spin waves are propagating disturbances in the magnetization of magnetic materials. One of their interesting properties is nonreciprocity, exhibiting that their amplitude depends on the magnetization direction. Nonreciprocity in spin waves is of great interest in both fundamental science and applications because it offers an extra knob to control the flow of waves for the technological fields of logics and switch applications. We show a high nonreciprocity in spin waves from Ta/Py bilayer systems with out-of-plane magnetic fields. The nonreciprocity depends on the thickness of Ta underlayer, which is found to induce an interfacial anisotropy. The origin of observed high nonreciprocity is twofold: different polarities of the in-plane magnetization due to different angles of canted out-of-plane anisotropy and the spin pumping effect at the Ta/Py interface. Our findings provide an opportunity to engineer highly efficient, nonreciprocal spin wave–based applications, such as nonreciprocal microwave devices, magnonic logic gates, and information transports. PMID:27419231

  16. Cross sections for fast-neutron interaction with Lu, Tb, and Ta isotopes

    SciTech Connect

    Dzysiuk, N.; Kadenko, I.; Yermolenko, R.; Koning, A. J.

    2010-01-15

    The cross sections for (n,x) reactions with Lu, Tb, and Ta isotopes were measured at (d,t) neutron energies around 14 MeV with the activation technique using metal foils of natural composition. Additionally, tantalum samples were irradiated with (d,d) neutrons and filtered neutron beams. To ensure an acceptable precision of the results all major sources of uncertainties were taken into account. Calculations of efficiency and correction factors were performed with the Monte Carlo technique. The cross section results obtained for the {sup 175}Lu(n,{alpha}){sup 172}Tm reaction at (d,t) neutron energies are reported for the first time. {sup 181}Ta(n,{gamma}){sup 182}Ta{sup m2} reaction cross sections were also measured for the first time at 1.9, 58.7, and 144.3 keV and at 2.85 MeV. The earlier evaluated cross section upper estimate for the nuclear reaction {sup 159}Tb(n,n{sup '}{alpha}){sup 155}Eu is reported in this article to be one order lower. Some other cross sections were obtained with higher precision. Theoretical calculations of excitation functions were performed with the TALYS-1.0 code and compared with the experimental cross section values.

  17. Topological Dirac surface states and superconducting pairing correlations in PbTaSe2

    NASA Astrophysics Data System (ADS)

    Chang, Tay-Rong; Chen, Peng-Jen; Bian, Guang; Huang, Shin-Ming; Zheng, Hao; Neupert, Titus; Sankar, Raman; Xu, Su-Yang; Belopolski, Ilya; Chang, Guoqing; Wang, BaoKai; Chou, Fangcheng; Bansil, Arun; Jeng, Horng-Tay; Lin, Hsin; Hasan, M. Zahid

    2016-06-01

    Superconductivity in topological band structures is a platform for realizing Majorana bound states and other exotic physical phenomena such as emergent supersymmetry. This potential nourishes the search for topological materials with intrinsic superconducting instabilities, in which Cooper pairing is introduced to electrons with helical spin texture such as the Dirac surface states of topological insulators, forming a time-reversal symmetric topological superconductor on the surface. We employ first-principles calculations and angle-resolved photoemission spectroscopy experiments to reveal that PbTaSe2, a noncentrosymmetric superconductor, possesses a nonzero Z2 topological invariant and fully spin-polarized Dirac surface states. Moreover, we analyze the phonon spectrum of PbTaSe2 to show how superconductivity emerges in this compound due to a stiffening of phonons by the Pb intercalation, which diminishes a competing charge-density-wave instability. By combining our findings on the topological band structure and the superconducting electron pairing, our work establishes PbTaSe2 as a stoichiometric superconductor with topological Dirac surface states. This type of intrinsic topological Dirac superconductors holds great promise for studying aspects of topological superconductors such as Majorana zero modes.

  18. AuTa 5S: A Cubic Rod Packing of Condensed (Au, Ta) 13Icosahedra Interwoven with a Three-Dimensional Framework of Corner-Connected STa 6Octahedra

    NASA Astrophysics Data System (ADS)

    Harbrecht, Bernd; Wagner, Volker; Pietzonka, Clemens

    1998-08-01

    AuTa 5S was prepared from a compressed mixture of tantalum disulfide, tantalum, and gold in a sealed tantalum capsule at 1650 K within 2 days. Above 1750 K the sulfide disproportionates in the solid state. The structure of AuTa 5S ( a=1250.82(3) pm, Foverline43 m, Z=16, Pearson symbol cF112) was determined from integrated X-ray powder diffraction intensities by direct methods and subsequently refined by fitting the profiles (13 structure variables, Rwp=0.036). Three of five crystallographically distinct metal atoms have distorted icosahedral coordinations. Sulfur is trigonal antiprismatically coordinated by tantalum. The structure is composed of two mutually interpenetrating zinc blende-like frameworks consisting of corner-connected STa 6octahedra and corner-connected Au 4Ta 4and Ta 4Ta 4stellae quadrangulae. The unique structure of AuTa 5S represents a link between two major intermetallic structure families, the η-carbide-type and the Mn 23Th 6-type structures.

  19. The Electrochemical Noise Study of TA10 Heat Exchanger Tubes in the Tri-effect Continuous Evaporation and Crystallization Device

    NASA Astrophysics Data System (ADS)

    Chen, Bing; Ruan, Ying-Hao; Jiang, Nan

    2016-05-01

    According to the tube process conditions of a TA10 heat exchanger, which is working in a chemical plant, the paper analyzes the possible factors of corrosion, identify the main influencing factors of the corrosion failure of heat exchanger were temperature, pH value, and the concentration of Aluminum Chloride Hexahydrate. Using the orthogonal test and electrochemical noise measurement technique to study the influence of three factors on TA10 alloy. The results show that the TA10 alloy has no obvious corrosion in the range of experimental study. The result of the range analysis determines the temperature and pH value are the main factors influencing the noise resistance Rn, the value of the noise resistance Rn increases with the rise of the temperature. When the temperature is 90□, the pH value is 2, the noise resistance Rn of the TA10 alloy specimen is largest.

  20. Temperature dependence of the electric field gradient at 181Ta in nanostructured HfO2 film

    NASA Astrophysics Data System (ADS)

    Cavalcante, F. H. C.; Carbonari, A. W.; Soares, J. C.

    2010-11-01

    The hyperfine field at metal lattice sites in a nanostructured HfO2 thin film was studied by the Perturbed Angular Correlation (PAC) technique using 181Ta as probe nuclei. The thin oxide film was deposited by pulsed laser ablation on a silicon substrate kept at 673 K. The resulting film thickness was about 25 nm. The 181Ta isotopes are formed in Hf sites of the sample as disintegration product of radioactive 181Hf, which were produced by neutron activation of the very thin film by the reaction 180Hf(n,γ)181Hf.. PAC measurements of the electric field gradient at the 181Ta probe sites .were performed with the thin film in the temperature range 295 - 1273 K in vacuum. Results showed that the film has a single crystalline structure and two different quadrupole frequencies could be observed corresponding to 181Ta at monoclinic structure and with oxygen vacancy in its neighborhood.

  1. MuTAnT: a family of Mutator-like transposable elements targeting TA microsatellites in Medicago truncatula.

    PubMed

    Stawujak, Krzysztof; Startek, Michał; Gambin, Anna; Grzebelus, Dariusz

    2015-08-01

    Transposable elements (TEs) are mobile DNA segments, abundant and dynamic in plant genomes. Because their mobility can be potentially deleterious to the host, a variety of mechanisms evolved limiting that negative impact, one of them being preference for a specific target insertion site. Here, we describe a family of Mutator-like DNA transposons in Medicago truncatula targeting TA microsatellites. We identified 218 copies of MuTAnTs and an element carrying a complete ORF encoding a mudrA-like transposase. Most insertion sites are flanked by a variable number of TA tandem repeats, indicating that MuTAnTs are specifically targeting TA microsatellites. Other TE families flanked by TA repeats (e.g. TAFT elements in maize) were described previously, however we identified the first putative autonomous element sharing that characteristics with a related group of short non-autonomous transposons.

  2. Mg-Zr Cosubstituted Ta3N5 Photoanode for Lower-Onset-Potential Solar-Driven Photoelectrochemical Water Splitting.

    PubMed

    Seo, Jeongsuk; Takata, Tsuyoshi; Nakabayashi, Mamiko; Hisatomi, Takashi; Shibata, Naoya; Minegishi, Tsutomu; Domen, Kazunari

    2015-10-14

    In p/n photoelectrochemical (PEC) cell systems, a low onset potential for the photoanode, as well as a high photocurrent, are critical for efficient water splitting. Here, we report a Mg-Zr cosubstituted Ta3N5 (Ta3N5:Mg+Zr) photoanode, designed to provide a more negative onset potential for PEC water splitting. The anodic photocurrent onset on Ta3N5:Mg+Zr was 0.55 V(RHE) under AM 1.5G-simulated sunlight, which represented a negative shift from the ca. 0.8 V(RHE) for pure Ta3N5. This negative shift in the onset potential of PEC water splitting was attributed to the change in the bandgap potential due to partial substitution by the foreign ions Mg(2+) and/or Zr(4+). PMID:26426439

  3. Role of spin mixing conductance in spin pumping: Enhancement of spin pumping efficiency in Ta/Cu/Py structures

    SciTech Connect

    Deorani, Praveen; Yang, Hyunsoo

    2013-12-02

    From spin pumping measurements in Ta/Py devices for different thicknesses of Ta, we determine the spin Hall angle to be 0.021–0.033 and spin diffusion length to be 8 nm in Ta. We have also studied the effect of changing the properties of non-magnet/ferromagnet interface by adding a Cu interlayer. The experimental results show that the effective spin mixing conductance increases in the presence of Cu interlayer for Ta/Cu/Py devices whereas it decreases in Pt/Cu/Py devices. Our findings allow the tunability of the spin pumping efficiency by adding a thin interlayer at the non-magnet/ferromagnet interface.

  4. Drought tolerance through over-expression of the expansin gene TaEXPB23 in transgenic tobacco.

    PubMed

    Li, Feng; Xing, Shichao; Guo, Qifang; Zhao, Meirong; Zhang, Jin; Gao, Qiang; Wang, Guiping; Wang, Wei

    2011-06-15

    Expansins are proteins that are the key regulators of wall extension during plant growth. To investigate the role of TaEXPB23, a wheat expansin gene, we analyzed TaEXPB23 mRNA expression levels in response to water stress in wheat and examined the drought resistance of transgenic tobaccos over-expressing TaEXPB23. We found that the expression of TaEXPB23 corresponded to wheat coleoptile growth and the response to water stress. The results also indicated that the transgenic tobacco lines lost water more slowly than the wild-type (WT) plants under drought stress; their cells could sustain a more integrated structure under water stress than that of WT. Other physiological and biochemical parameters under water stress, such as electrolyte leakage, malondialdehyde (MDA) level, photosynthetic rate, F(v)/F(m) and ΦPSII, also suggested that the transgenic tobaccos were more drought resistant than WT plants.

  5. STUDY ON SYNTHESIS AND EVOLUTION OF NANOCRYSTALLINE Mg4Ta2O9 BY AQUEOUS SOL-GEL PROCESS

    NASA Astrophysics Data System (ADS)

    Wu, H. T.; Yang, C. H.; Wu, W. B.; Yue, Y. L.

    2012-06-01

    Nanosized and highly reactive Mg4Ta2O9 were successfully synthesized by aqueous sol-gel method compared with conventional solid-state method. Ta-Mg-citric acid solution was first formed and then evaporated resulting in a dry gel for calcination in the temperature ranging from 600°C to 800°C for crystallization in oxygen atmosphere. The crystallization process from the gel to crystalline Mg4Ta2O9 was identified by thermal analysis and phase evolution of powders was studied using X-ray diffraction (XRD) technique during calcinations. Particle size and morphology were examined by transmission electron microscopy (TEM) and high resolution scanning electron microscopy (HR-SEM). The results revealed that sol-gel process showed great advantages over conventional solid-state method and Mg4Ta2O9 nanopowders with the size of 20-30 nm were obtained at 800°C.

  6. Three TaFAR genes function in the biosynthesis of primary alcohols and the response to abiotic stresses in Triticum aestivum.

    PubMed

    Wang, Meiling; Wang, Yong; Wu, Hongqi; Xu, Jing; Li, Tingting; Hegebarth, Daniela; Jetter, Reinhard; Chen, Letian; Wang, Zhonghua

    2016-01-01

    Cuticular waxes play crucial roles in protecting plants against biotic and abiotic stresses. They are complex mixtures of very-long-chain fatty acids and their derivatives, including C20-C32 fatty alcohols. Here, we report the identification of 32 FAR-like genes and the detailed characterization of TaFAR2, TaFAR3 and TaFAR4, wax biosynthetic genes encoding fatty acyl-coenzyme A reductase (FAR) in wheat leaf cuticle. Heterologous expression of the three TaFARs in wild-type yeast and mutated yeast showed that TaFAR2, TaFAR3 and TaFAR4 were predominantly responsible for the accumulation of C18:0, C28:0 and C24:0 primary alcohols, respectively. Transgenic expression of the three TaFARs in tomato fruit and Arabidopsis cer4 mutant led to increased production of C22:0-C30:0 primary alcohols. GFP-fusion protein injection assay showed that the three encoded TaFAR proteins were localized to the endoplasmic reticulum (ER), the site of wax biosynthesis. The transcriptional expression of the three TaFAR genes was induced by cold, salt, drought and ABA. Low air humidity led to increased expression of TaFAR genes and elevated wax accumulation in wheat leaves. Collectively, these data suggest that TaFAR2, TaFAR3 and TaFAR4 encode active alcohol-forming FARs involved in the synthesis of primary alcohol in wheat leaf and the response to environmental stresses. PMID:27112792

  7. Characterization of thermally oxidized Ta/GaAs Schottky barrier structures prepared by low energy RF sputtering with X-ray photoemission, TEM and optical transmittance measurements

    NASA Astrophysics Data System (ADS)

    Gladkov, P.; Varblianska, K.; Marinova, Ts.; Krastev, V.; Stoemenos, J.

    Schottky barrier Ta 2O 5/Ta/GaAs structures produced by RF magnetron sputtering of Ta onto "in situ" sputter etched GaAs substrates are the subject of the present investigation. The tantalum oxides formed directly during the process of thermal recovery of the structures contain predominantly Ta 2O 5 according to XPS data. The component distribution in these structures, formed under optimum recovery conditions with respect to the Schottky barrier parameters ( ΦB and η) has been studied by XPS and TEM. The applied conditions for thermal recovery and simultaneous oxidation are: isothermal annealing at temperatures 400-420°C for 100 min in an ambient of dry air and starting layers of 40 nm RF-sputtered Ta. The partial oxidation of the Ta layer during the heat treatment results in the formation of a thin layer of Ta 2O 5 on the top of the structure, followed by two layers: a mixture of Ta 2O 5 + Ta and a thin Schottky contact predominantly consisting of Ta. The total optical transmittance in the spectral range 0.7-1.1 μ of these three successive layers is ≥ 0.7. This result justifies the potential application of these structures in the creation of Schottky photodiodes in the visible and near-IR. It is established as well that at T ≥ 400°C GaAs and Ta start interacting resulting in the formation of intermetallic compounds of the type: Ta 5Ga, Ta 5Ga 3, and TaGa 3.

  8. Three TaFAR genes function in the biosynthesis of primary alcohols and the response to abiotic stresses in Triticum aestivum

    PubMed Central

    Wang, Meiling; Wang, Yong; Wu, Hongqi; Xu, Jing; Li, Tingting; Hegebarth, Daniela; Jetter, Reinhard; Chen, Letian; Wang, Zhonghua

    2016-01-01

    Cuticular waxes play crucial roles in protecting plants against biotic and abiotic stresses. They are complex mixtures of very-long-chain fatty acids and their derivatives, including C20–C32 fatty alcohols. Here, we report the identification of 32 FAR-like genes and the detailed characterization of TaFAR2, TaFAR3 and TaFAR4, wax biosynthetic genes encoding fatty acyl-coenzyme A reductase (FAR) in wheat leaf cuticle. Heterologous expression of the three TaFARs in wild-type yeast and mutated yeast showed that TaFAR2, TaFAR3 and TaFAR4 were predominantly responsible for the accumulation of C18:0, C28:0 and C24:0 primary alcohols, respectively. Transgenic expression of the three TaFARs in tomato fruit and Arabidopsis cer4 mutant led to increased production of C22:0–C30:0 primary alcohols. GFP-fusion protein injection assay showed that the three encoded TaFAR proteins were localized to the endoplasmic reticulum (ER), the site of wax biosynthesis. The transcriptional expression of the three TaFAR genes was induced by cold, salt, drought and ABA. Low air humidity led to increased expression of TaFAR genes and elevated wax accumulation in wheat leaves. Collectively, these data suggest that TaFAR2, TaFAR3 and TaFAR4 encode active alcohol-forming FARs involved in the synthesis of primary alcohol in wheat leaf and the response to environmental stresses. PMID:27112792

  9. Superconductivity in Y6Tr4Al43 (Tr = Nb, Mo, Ta) with Peanut-Shaped Cage Structure

    NASA Astrophysics Data System (ADS)

    Kase, Naoki; Satoh, Ryoh; Nakano, Tomohito; Takeda, Naoya

    2016-10-01

    Superconductivity is discovered in Y6Tr4Al43 (Tr = Nb, Mo, Ta) with a peanut-shaped cage structure at Tc = 0.86, 0.75, and 0.68 K, respectively. The superconducting state is revealed by performing electrical resistivity and specific heat measurements. The upper critical field is obtained to be 0.22 (Nb), 0.175 (Mo), and 0.15 T (Ta). A specific heat jump provides evidence of bulk superconductivity in these compounds.

  10. Overexpression of the Wheat Expansin Gene TaEXPA2 Improved Seed Production and Drought Tolerance in Transgenic Tobacco Plants

    PubMed Central

    Chen, Yanhui; Han, Yangyang; Zhang, Meng; Zhou, Shan; Kong, Xiangzhu; Wang, Wei

    2016-01-01

    Expansins are cell wall proteins that are grouped into two main families, α-expansins and β-expansins, and they are implicated in the control of cell extension via the disruption of hydrogen bonds between cellulose and matrix glucans. TaEXPA2 is an α-expansin gene identified in wheat. Based on putative cis-regulatory elements in the TaEXPA2 promoter sequence and the expression pattern induced when polyethylene glycol (PEG) is used to mimic water stress, we hypothesized that TaEXPA2 is involved in plant drought tolerance and plant development. Through transient expression of 35S::TaEXPA2-GFP in onion epidermal cells, TaEXPA2 was localized to the cell wall. Constitutive expression of TaEXPA2 in tobacco improved seed production by increasing capsule number, not seed size, without having any effect on plant growth patterns. The transgenic tobacco exhibited a significantly greater tolerance to water-deficiency stress than did wild-type (WT) plants. We found that under drought stress, the transgenic plants maintained a better water status. The accumulated content of osmotic adjustment substances, such as proline, in TaEXPA2 transgenic plants was greater than that in WT plants. Transgenic plants also displayed greater antioxidative competence as indicated by their lower malondialdehyde (MDA) content, relative electrical conductivity, and reactive oxygen species (ROS) accumulation than did WT plants. This result suggests that the transgenic plants suffer less damage from ROS under drought conditions. The activities of some antioxidant enzymes as well as expression levels of several genes encoding key antioxidant enzymes were higher in the transgenic plants than in the WT plants under drought stress. Collectively, our results suggest that ectopic expression of the wheat expansin gene TaEXPA2 improves seed production and drought tolerance in transgenic tobacco plants. PMID:27073898

  11. The wheat TaGBF1 gene is involved in the blue-light response and salt tolerance.

    PubMed

    Sun, Yang; Xu, Wei; Jia, Yuebin; Wang, Mengcheng; Xia, Guangmin

    2015-12-01

    Light and abiotic stress both strongly modulate plant growth and development. However, the effect of light-responsive factors on growth and abiotic stress responses in wheat (Triticum aestivum) is unknown. G-box binding factors (GBFs) are blue light-specific components, but their function in abiotic stress responses has not been studied. Here we identified a wheat GBF1 gene that mediated both the blue light- and abiotic stress-responsive signaling pathways. TaGBF1 was inducible by blue light, salt and exposure to abscisic acid (ABA). TaGBF1 interacted with a G-box light-responsive element in vitro and promoted a blue-light response in wheat and Aradidopsis thaliana. Both TaGBF1 over-expression in wheat and its heterologous expression in A. thaliana heighten sensitivity to salinity and ABA, but its knockdown in wheat conferred resistance to high salinity and ABA. The expression of AtABI5, a key component of the ABA signaling pathway in A. thaliana, and its homolog Wabi5 in wheat was increased by transgenic expression of TaGBF1. The hypersensitivity to salt and ABA caused by TaGBF1 was not observed in the abi5 mutant background, showing that ABI5 is the mediator in TaGBF1-induced abiotic stress responses. However, the hypersensitivity to salt conferred by TaGBF1 is not dependent on light. This suggests that TaGBF1 is a common component of blue light- and abiotic stress-responsive signaling pathways.

  12. Overexpression of the Wheat Expansin Gene TaEXPA2 Improved Seed Production and Drought Tolerance in Transgenic Tobacco Plants.

    PubMed

    Chen, Yanhui; Han, Yangyang; Zhang, Meng; Zhou, Shan; Kong, Xiangzhu; Wang, Wei

    2016-01-01

    Expansins are cell wall proteins that are grouped into two main families, α-expansins and β-expansins, and they are implicated in the control of cell extension via the disruption of hydrogen bonds between cellulose and matrix glucans. TaEXPA2 is an α-expansin gene identified in wheat. Based on putative cis-regulatory elements in the TaEXPA2 promoter sequence and the expression pattern induced when polyethylene glycol (PEG) is used to mimic water stress, we hypothesized that TaEXPA2 is involved in plant drought tolerance and plant development. Through transient expression of 35S::TaEXPA2-GFP in onion epidermal cells, TaEXPA2 was localized to the cell wall. Constitutive expression of TaEXPA2 in tobacco improved seed production by increasing capsule number, not seed size, without having any effect on plant growth patterns. The transgenic tobacco exhibited a significantly greater tolerance to water-deficiency stress than did wild-type (WT) plants. We found that under drought stress, the transgenic plants maintained a better water status. The accumulated content of osmotic adjustment substances, such as proline, in TaEXPA2 transgenic plants was greater than that in WT plants. Transgenic plants also displayed greater antioxidative competence as indicated by their lower malondialdehyde (MDA) content, relative electrical conductivity, and reactive oxygen species (ROS) accumulation than did WT plants. This result suggests that the transgenic plants suffer less damage from ROS under drought conditions. The activities of some antioxidant enzymes as well as expression levels of several genes encoding key antioxidant enzymes were higher in the transgenic plants than in the WT plants under drought stress. Collectively, our results suggest that ectopic expression of the wheat expansin gene TaEXPA2 improves seed production and drought tolerance in transgenic tobacco plants.

  13. Overexpression of the Wheat Expansin Gene TaEXPA2 Improved Seed Production and Drought Tolerance in Transgenic Tobacco Plants.

    PubMed

    Chen, Yanhui; Han, Yangyang; Zhang, Meng; Zhou, Shan; Kong, Xiangzhu; Wang, Wei

    2016-01-01

    Expansins are cell wall proteins that are grouped into two main families, α-expansins and β-expansins, and they are implicated in the control of cell extension via the disruption of hydrogen bonds between cellulose and matrix glucans. TaEXPA2 is an α-expansin gene identified in wheat. Based on putative cis-regulatory elements in the TaEXPA2 promoter sequence and the expression pattern induced when polyethylene glycol (PEG) is used to mimic water stress, we hypothesized that TaEXPA2 is involved in plant drought tolerance and plant development. Through transient expression of 35S::TaEXPA2-GFP in onion epidermal cells, TaEXPA2 was localized to the cell wall. Constitutive expression of TaEXPA2 in tobacco improved seed production by increasing capsule number, not seed size, without having any effect on plant growth patterns. The transgenic tobacco exhibited a significantly greater tolerance to water-deficiency stress than did wild-type (WT) plants. We found that under drought stress, the transgenic plants maintained a better water status. The accumulated content of osmotic adjustment substances, such as proline, in TaEXPA2 transgenic plants was greater than that in WT plants. Transgenic plants also displayed greater antioxidative competence as indicated by their lower malondialdehyde (MDA) content, relative electrical conductivity, and reactive oxygen species (ROS) accumulation than did WT plants. This result suggests that the transgenic plants suffer less damage from ROS under drought conditions. The activities of some antioxidant enzymes as well as expression levels of several genes encoding key antioxidant enzymes were higher in the transgenic plants than in the WT plants under drought stress. Collectively, our results suggest that ectopic expression of the wheat expansin gene TaEXPA2 improves seed production and drought tolerance in transgenic tobacco plants. PMID:27073898

  14. The wheat TaGBF1 gene is involved in the blue-light response and salt tolerance.

    PubMed

    Sun, Yang; Xu, Wei; Jia, Yuebin; Wang, Mengcheng; Xia, Guangmin

    2015-12-01

    Light and abiotic stress both strongly modulate plant growth and development. However, the effect of light-responsive factors on growth and abiotic stress responses in wheat (Triticum aestivum) is unknown. G-box binding factors (GBFs) are blue light-specific components, but their function in abiotic stress responses has not been studied. Here we identified a wheat GBF1 gene that mediated both the blue light- and abiotic stress-responsive signaling pathways. TaGBF1 was inducible by blue light, salt and exposure to abscisic acid (ABA). TaGBF1 interacted with a G-box light-responsive element in vitro and promoted a blue-light response in wheat and Aradidopsis thaliana. Both TaGBF1 over-expression in wheat and its heterologous expression in A. thaliana heighten sensitivity to salinity and ABA, but its knockdown in wheat conferred resistance to high salinity and ABA. The expression of AtABI5, a key component of the ABA signaling pathway in A. thaliana, and its homolog Wabi5 in wheat was increased by transgenic expression of TaGBF1. The hypersensitivity to salt and ABA caused by TaGBF1 was not observed in the abi5 mutant background, showing that ABI5 is the mediator in TaGBF1-induced abiotic stress responses. However, the hypersensitivity to salt conferred by TaGBF1 is not dependent on light. This suggests that TaGBF1 is a common component of blue light- and abiotic stress-responsive signaling pathways. PMID:26588879

  15. Chloride Metathesis and Dimethylamide Transfer in the Reaction of TaCl(NMe2)4 with ZnMe2 and MeMgCl: Spectroscopic Studies and X-ray Diffraction Structures of TaCl(Me)(NMe2)3 and ZnCl2(NHMe2)2

    SciTech Connect

    Wang, Xiaoping; Huang, Shih-Huang Huang; Richmond, Michael G.

    2010-01-01

    The reaction of TaCl(NMe2)4 with ZnMe2 in hydrocarbon solvent has been examined and found to give a mixture of TaCl(Me)(NMe2)3, TaMe(NMe2)4, and Ta(NMe2)5 by 1H NMR spectroscopy. Depending upon the work-up conditions employed, the compounds TaCl(Me)(NMe2)3 and ZnCl2(NHMe2)2 have been isolated and structurally characterized by X-ray crystallography. TaCl(NMe2)4 reacts with MeMgCl is a similar fashion and affords TaCl(Me)(NMe2)3 and Ta(NMe2)5 as the principal reaction products.

  16. Structure, magnetism, specific heat, and dielectric properties of Eu{sub 2}Ta{sub 2}O{sub 7}

    SciTech Connect

    Kolodiazhnyi, T. Sakurai, H.; Matsushita, Y.

    2014-11-17

    Polycrystalline Eu{sub 2}Ta{sub 2}O{sub 7} containing layered perovskite slabs was prepared and analyzed. Eu{sub 2}Ta{sub 2}O{sub 7} crystallizes in the orthorhombic centrosymmetric Cmcm space group (with unit cell: a = 3.95156(9), b = 27.0775(6), and c = 5.68279(13) Å) isomorphous with high-temperature Sr{sub 2}Ta{sub 2}O{sub 7}. Dielectric measurements reveal that, in contrast to Sr{sub 2}Ta{sub 2}O{sub 7} which is ferroelectric below 166 K, Eu{sub 2}Ta{sub 2}O{sub 7} remains paraelectric down to at least 0.45 K and shows no magneto-dielectric coupling. Magnetic data in the 2–400 K range indicate an antiferromagnetic phase transition with a sharp susceptibility peak at 2.71(5) K. Further analysis using specific heat measurements reveals that the second magnetic phase transition occurs at 1.10(5) K and dominates the spin entropy of the Eu{sup 2+} 4f{sup 7} ions. The possible origin of the two successive magnetic phase transitions in Eu{sub 2}Ta{sub 2}O{sub 7} requires further studies.

  17. The Novel Wheat Transcription Factor TaNAC47 Enhances Multiple Abiotic Stress Tolerances in Transgenic Plants

    PubMed Central

    Zhang, Lina; Zhang, Lichao; Xia, Chuan; Zhao, Guangyao; Jia, Jizeng; Kong, Xiuying

    2016-01-01

    NAC transcription factors play diverse roles in plant development and responses to abiotic stresses. However, the biological roles of NAC family members in wheat are not well understood. Here, we reported the isolation and functional characterization of a novel wheat TaNAC47 gene. TaNAC47 encoded protein, localizing in the nucleus, is able to bind to the ABRE cis-element and transactivate transcription in yeast, suggesting that it likely functions as a transcriptional activator. We also showed that TaNAC47 is differentially expressed in different tissues, and its expression was induced by the stress treatments of salt, cold, polyethylene glycol and exogenous abscisic acid. Furthermore, overexpression of TaNAC47 in Arabidopsis resulted in ABA hypersensitivity and enhancing tolerance of transgenic plants to drought, salt, and freezing stresses. Strikingly, overexpression of TaNAC47 was found to activate the expression of downstream genes and change several physiological indices that may enable transgenic plants to overcome unfavorable environments. Taken together, these results uncovered an important role of wheat TaNAC47 gene in response to ABA and abiotic stresses. PMID:26834757

  18. TaNAC2, a NAC-type wheat transcription factor conferring enhanced multiple abiotic stress tolerances in Arabidopsis

    PubMed Central

    Mao, Xinguo; Zhang, Hongying; Qian, Xueya; Li, Ang; Zhao, Guangyao; Jing, Ruilian

    2012-01-01

    Environmental stresses such as drought, salinity, and cold are major factors that significantly limit agricultural productivity. NAC transcription factors play essential roles in response to various abiotic stresses. However, the paucity of wheat NAC members functionally characterized to date does not match the importance of this plant as a world staple crop. Here, the function of TaNAC2 was characterized in Arabidopsis thaliana. A fragment of TaNAC2 was obtained from suppression subtractive cDNA libraries of wheat treated with polyethylene glycol, and its full-length cDNA was obtained by searching a full-length wheat cDNA library. Gene expression profiles indicated that TaNAC2 was involved in response to drought, salt, cold, and abscisic acid treatment. To test its function, transgenic Arabidopsis lines overexpressing TaNAC2–GFP controlled by the cauliflower mosaic virus 35S promoter were generated. Overexpression of TaNAC2 resulted in enhanced tolerances to drought, salt, and freezing stresses in Arabidopsis, which were simultaneously demonstrated by enhanced expression of abiotic stress-response genes and several physiological indices. Therefore, TaNAC2 has potential for utilization in transgenic breeding to improve abiotic stress tolerances in crops. PMID:22330896

  19. Measurement and Modeling of Short and Medium Range Order in Amorphous Ta2O5 Thin Films

    PubMed Central

    Shyam, Badri; Stone, Kevin H.; Bassiri, Riccardo; Fejer, Martin M.; Toney, Michael F.; Mehta, Apurva

    2016-01-01

    Amorphous films and coatings are rapidly growing in importance. Yet, there is a dearth of high-quality structural data on sub-micron films. Not understanding how these materials assemble at atomic scale limits fundamental insights needed to improve their performance. Here, we use grazing-incidence x-ray total scattering measurements to examine the atomic structure of the top 50–100 nm of Ta2O5 films; mirror coatings that show high promise to significantly improve the sensitivity of the next generation of gravitational-wave detectors. Our measurements show noticeable changes well into medium range, not only between crystalline and amorphous, but also between as-deposited, annealed and doped amorphous films. It is a further challenge to quickly translate the structural information into insights into mechanisms of packing and disorder. Here, we illustrate a modeling approach that allows translation of observed structural features to a physically intuitive packing of a primary structural unit based on a kinked Ta-O-Ta backbone. Our modeling illustrates how Ta-O-Ta units link to form longer 1D chains and even 2D ribbons, and how doping and annealing influences formation of 2D order. We also find that all the amorphousTa2O5 films studied in here are not just poorly crystalline but appear to lack true 3D order. PMID:27562542

  20. TaNAC2, a NAC-type wheat transcription factor conferring enhanced multiple abiotic stress tolerances in Arabidopsis.

    PubMed

    Mao, Xinguo; Zhang, Hongying; Qian, Xueya; Li, Ang; Zhao, Guangyao; Jing, Ruilian

    2012-05-01

    Environmental stresses such as drought, salinity, and cold are major factors that significantly limit agricultural productivity. NAC transcription factors play essential roles in response to various abiotic stresses. However, the paucity of wheat NAC members functionally characterized to date does not match the importance of this plant as a world staple crop. Here, the function of TaNAC2 was characterized in Arabidopsis thaliana. A fragment of TaNAC2 was obtained from suppression subtractive cDNA libraries of wheat treated with polyethylene glycol, and its full-length cDNA was obtained by searching a full-length wheat cDNA library. Gene expression profiles indicated that TaNAC2 was involved in response to drought, salt, cold, and abscisic acid treatment. To test its function, transgenic Arabidopsis lines overexpressing TaNAC2-GFP controlled by the cauliflower mosaic virus 35S promoter were generated. Overexpression of TaNAC2 resulted in enhanced tolerances to drought, salt, and freezing stresses in Arabidopsis, which were simultaneously demonstrated by enhanced expression of abiotic stress-response genes and several physiological indices. Therefore, TaNAC2 has potential for utilization in transgenic breeding to improve abiotic stress tolerances in crops.

  1. Measurement and Modeling of Short and Medium Range Order in Amorphous Ta2O5 Thin Films.

    PubMed

    Shyam, Badri; Stone, Kevin H; Bassiri, Riccardo; Fejer, Martin M; Toney, Michael F; Mehta, Apurva

    2016-01-01

    Amorphous films and coatings are rapidly growing in importance. Yet, there is a dearth of high-quality structural data on sub-micron films. Not understanding how these materials assemble at atomic scale limits fundamental insights needed to improve their performance. Here, we use grazing-incidence x-ray total scattering measurements to examine the atomic structure of the top 50-100 nm of Ta2O5 films; mirror coatings that show high promise to significantly improve the sensitivity of the next generation of gravitational-wave detectors. Our measurements show noticeable changes well into medium range, not only between crystalline and amorphous, but also between as-deposited, annealed and doped amorphous films. It is a further challenge to quickly translate the structural information into insights into mechanisms of packing and disorder. Here, we illustrate a modeling approach that allows translation of observed structural features to a physically intuitive packing of a primary structural unit based on a kinked Ta-O-Ta backbone. Our modeling illustrates how Ta-O-Ta units link to form longer 1D chains and even 2D ribbons, and how doping and annealing influences formation of 2D order. We also find that all the amorphousTa2O5 films studied in here are not just poorly crystalline but appear to lack true 3D order. PMID:27562542

  2. Synthesis, structure and photoluminescence properties of Ho3+ doped TTB-BaTa2O6 phosphors

    NASA Astrophysics Data System (ADS)

    İlhan, Mustafa

    2014-12-01

    Ho3+ doped TTB-BaTa2O6 phosphors were produced by the solid state reaction method. XRD analysis confirmed the formation of BaTa2O6 single phase which was accomplished by heat treatment at 1425 °C for 20 h. The crystal structure of TTB-BaTa2O6 allowed doping concentration of Ho3+ ions up to 10 mol%, maintaining a single phase composition. A second phase of HoTaO4 begins to appear at 15 mol%. The lattice structure and the crystallite sizes changed with the concentration of Ho3+. In SEM analysis, it was also shown that BaTa2O6 grain sizes changed with the concentration of Ho3+. EDS analysis revealed that the Ta/Ba ratio increased on the grains depending on Ho3+ concentration. Charge balance of the structure was formulated through the EDS results. In fluorometer analysis, a strong green emission (λem = 546.9 nm) was observed in the visible spectral region. The emission increased with the doping concentration of up to 2.5 mol%, and above this level decreased due to concentration quenching.

  3. The role of the F-box gene TaFBA1 from wheat (Triticum aestivum L.) in drought tolerance.

    PubMed

    Zhou, Shumei; Sun, Xiudong; Yin, Suhong; Kong, Xiangzhu; Zhou, Shan; Xu, Ying; Luo, Yin; Wang, Wei

    2014-11-01

    Drought is one of the most important factors limiting plant growth and development. We identified a gene in wheat (Triticum aestivum L.) under drought stress named TaFBA1. TaFBA1 encodes a putative 325-amino-acid F-box protein with a conserved N-terminal F-box domain and a C-terminal AMN1 domain. Real-time RT-PCR analysis revealed that TaFBA1 transcript accumulation was upregulated by high-salinity, water stress, and abscisic acid (ABA) treatment. To evaluate the functions of TaFBA1 in the regulation of drought stress responses, we produced transgenic tobacco lines overexpressing TaFBA1. Under water stress conditions, the transgenic tobacco plants had a higher germination rate, higher relative water content, net photosynthesis rate (Pn), less chlorophyll loss, and less growth inhibition than WT. These results demonstrate the high tolerance of the transgenic plants to drought stress compared to the WT. The enhanced oxidative stress tolerance of these plants, which may be involved in their drought tolerance, was indicated by their lower levels of reactive oxygen species (ROS) accumulation, MDA content, and cell membrane damage under drought stress compared to WT. The antioxidant enzyme activities were higher in the transgenic plants than in WT, which may be related to the upregulated expression of some antioxidant genes via overexpression of TaFBA1.

  4. Measurement and Modeling of Short and Medium Range Order in Amorphous Ta2O5 Thin Films

    NASA Astrophysics Data System (ADS)

    Shyam, Badri; Stone, Kevin H.; Bassiri, Riccardo; Fejer, Martin M.; Toney, Michael F.; Mehta, Apurva

    2016-08-01

    Amorphous films and coatings are rapidly growing in importance. Yet, there is a dearth of high-quality structural data on sub-micron films. Not understanding how these materials assemble at atomic scale limits fundamental insights needed to improve their performance. Here, we use grazing-incidence x-ray total scattering measurements to examine the atomic structure of the top 50–100 nm of Ta2O5 films; mirror coatings that show high promise to significantly improve the sensitivity of the next generation of gravitational-wave detectors. Our measurements show noticeable changes well into medium range, not only between crystalline and amorphous, but also between as-deposited, annealed and doped amorphous films. It is a further challenge to quickly translate the structural information into insights into mechanisms of packing and disorder. Here, we illustrate a modeling approach that allows translation of observed structural features to a physically intuitive packing of a primary structural unit based on a kinked Ta-O-Ta backbone. Our modeling illustrates how Ta-O-Ta units link to form longer 1D chains and even 2D ribbons, and how doping and annealing influences formation of 2D order. We also find that all the amorphousTa2O5 films studied in here are not just poorly crystalline but appear to lack true 3D order.

  5. Oxidation of ZrB2 SiC TaSi2 Materials at Ultra High Temperatures

    NASA Technical Reports Server (NTRS)

    Opila, E.; Smith, J.; Levine, S.; Lorincz, J.; Reigel, M.

    2008-01-01

    ZrB2 - 20v% SiC - 20v% TaSi2 was oxidized in stagnant air for ten minute cycles for times up to 100 minutes at 1627 C and 1927 C. The sample oxidized at 1627 C showed oxidation resistance better than that of the standard ZrB2 - 20v% SiC. The sample oxidized at 1927 C, however, showed evidence of liquid phase formation and complex oxidation products. The sample exposed at 1927 C was analyzed in detail by scanning electron microprobe and wavelength dispersive spectroscopy to understand the complex oxidation and melting reactions occurring during exposure. The as hot-pressed material shows the formation of a Zr(Ta)B2 phase in addition to the three phases in the nominal composition already noted. After oxidation, the TaSi2 in the matrix was completely reacted to form Ta(Zr)C. The layered oxidation products included SiO2, ZrO2, Ta2O5, and a complex oxide containing both Zr and Ta. Likely reactions are proposed based on thermodynamic phase stability and phase morphology.

  6. Measurement and modeling of short and medium range order in amorphous Ta2O5 thin films

    DOE PAGES

    Shyam, Badri; Stone, Kevin H.; Bassiri, Riccardo; Fejer, Martin M.; Toney, Michael F.; Mehta, Apurva

    2016-08-26

    Here, amorphous films and coatings are rapidly growing in importance. Yet, there is a dearth of high-quality structural data on sub-micron films. Not understanding how these materials assemble at atomic scale limits fundamental insights needed to improve their performance. Here, we use grazing-incidence x-ray total scattering measurements to examine the atomic structure of the top 50–100 nm of Ta2O5 films; mirror coatings that show high promise to significantly improve the sensitivity of the next generation of gravitational-wave detectors. Our measurements show noticeable changes well into medium range, not only between crystalline and amorphous, but also between as-deposited, annealed and dopedmore » amorphous films. It is a further challenge to quickly translate the structural information into insights into mechanisms of packing and disorder. Here, we illustrate a modeling approach that allows translation of observed structural features to a physically intuitive packing of a primary structural unit based on a kinked Ta-O-Ta backbone. Our modeling illustrates how Ta-O-Ta units link to form longer 1D chains and even 2D ribbons, and how doping and annealing influences formation of 2D order. We also find that all the amorphousTa2O5 films studied in here are not just poorly crystalline but appear to lack true 3D order.« less

  7. Preparation of g-C3N4/Ta2O5 Composites with Enhanced Visible-Light Photocatalytic Activity

    NASA Astrophysics Data System (ADS)

    Vo, Vien; Van Kim, Nguyen; Nga, Nguyen Thi Viet; Trung, Nguyen Tien; Giang, Le Truong; Van Hanh, Pham; Hoang, Luc Huy; Kim, Sung-Jin

    2016-05-01

    g-C3N4/Ta2O5 composites have been synthesized by a facile route in which mixtures of Ta2O5 and urea are heated at various temperatures of 450°C, 500°C, and 550°C. The obtained materials (denoted as CN/TaO- T, where T is the heating temperature) were characterized using x-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, diffuse-reflectance ultraviolet-visible (UV-Vis) spectroscopy, thermogravimetric analysis, and x-ray photoelectron spectroscopy. The results show that the as-prepared composites are in orthorhombic Ta2O5 phase coated by g-C3N4. The photocatalytic activity of the composites was evaluated by photodegradation of methylene blue under visible light. Among the three materials, CN/TaO-500 exhibited the highest photocatalytic activity. The improved photocatalytic activity of the g-C3N4/Ta2O5 composites is attributed to the presence of g-C3N4 in the materials.

  8. Synthesis and Optical Characterization of Red-Emitting BaTa2O6:Eu(3+) Phosphors.

    PubMed

    İlhan, Mustafa; Ekmekçi, Mete Kaan; Mergen, Ayhan; Yaman, Cemalettin

    2016-09-01

    Undoped and Eu(3+) doped BaTa2O6 phosphors were synthesized via solid state reaction method and characterized by using XRD, SEM-EDS and photoluminescence (PL) analyses. The XRD results revealed that the crystal structure of BaTa2O6 allowed up to 10 mol% levels of Eu(3+) ions due to the TTB characteristic network of adjacent octahedrals. SEM-EDS analyses confirmed the formation of BaTa2O6 structure and EuTaO4 secondary phase. BaTa2O6:Eu(3+) phosphors exhibited orange and red emissions at 592.2 nm and 615.7 nm in the visible region respectively. The Commission Internationale d'Eclairage (CIE) chromaticity coordinates of the BaTa2O6:Eu(3+) phosphors that excited at λ ex = 400 nm ranged from orangish-red to pinkish-red depending on increasing Eu(3+) concentration. PMID:27325113

  9. Crystal Structure, Transformation Strain, and Superelastic Property of Ti-Nb-Zr and Ti-Nb-Ta Alloys

    NASA Astrophysics Data System (ADS)

    Kim, Hee Young; Fu, Jie; Tobe, Hirobumi; Kim, Jae Il; Miyazaki, Shuichi

    2015-06-01

    The composition dependences of transformation strain and shape memory, and superelastic properties were extensively investigated in Ti-Nb-Zr and Ti-Nb-Ta alloys in order to establish the guidelines for alloy design of biomedical superelastic alloys. The effects of composition on the crystal structure of the parent (β) phase and the martensite (α″) phase were also investigated. Results showed that not only transformation temperature but also transformation strain is tunable by alloy design, i.e., adjusting contents of Nb, Zr, and Ta. The lattice constant of the β phase increased linearly with increasing Zr content, while it was insensitive to Nb and Ta contents. On the other hand, the lattice constants of the α″ phase are mainly affected by Nb and Ta contents. The increase of Zr content exhibited a weaker impact on the transformation strain compared with Nb and Ta. The addition of Zr as a substitute of Nb with keeping superelasticity at room temperature significantly increased the transformation strain. On the other hand, the addition of Ta decreased the transformation strain at the compositions showing superelasticity. This study confirmed that the crystallography of martensitic transformation can be the main principal to guide the alloy design of biomedical superelastic alloys.

  10. Conduction paths in Cu/amorphous-Ta{sub 2}O{sub 5}/Pt atomic switch: First-principles studies

    SciTech Connect

    Xiao, Bo Tada, Tomofumi; Watanabe, Satoshi; Gu, Tingkun

    2014-01-21

    We have examined the structure of Cu filaments in Cu/amorphous-Ta{sub 2}O{sub 5} (a-Ta{sub 2}O{sub 5})/Pt atomic switch from first principles. We have found that the Cu single atomic chains are unstable during the molecular dynamics (MD) simulation and thus cannot work as conduction paths. On the other hand, Cu nanowires with various diameters are stable and can form conductive paths. In this case, the Cu-Cu bonding mainly contributes to the conductive, delocalized defect state. These make a sharp contrast with the case of single Cu chains in crystalline Ta{sub 2}O{sub 5}, which can be conductive paths through the alternant Cu-Ta bonding structure. A series of MD simulations suggest that even Cu nanowires with a diameter of 0.24 nm can work as conduction paths. The calculations of the transport properties of Cu/a-Ta{sub 2}O{sub 5}/Pt heterostructures with Cu nanowires between two electrodes further confirm the conductive nature of the Cu nanowires in the a-Ta{sub 2}O{sub 5}.

  11. Thickness effect of ultra-thin Ta2O5 resistance switching layer in 28 nm-diameter memory cell

    PubMed Central

    Park, Tae Hyung; Song, Seul Ji; Kim, Hae Jin; Kim, Soo Gil; Chung, Suock; Kim, Beom Yong; Lee, Kee Jeung; Kim, Kyung Min; Choi, Byung Joon; Hwang, Cheol Seong

    2015-01-01

    Resistance switching (RS) devices with ultra-thin Ta2O5 switching layer (0.5–2.0 nm) with a cell diameter of 28 nm were fabricated. The performance of the devices was tested by voltage-driven current—voltage (I-V) sweep and closed-loop pulse switching (CLPS) tests. A Ta layer was placed beneath the Ta2O5 switching layer to act as an oxygen vacancy reservoir. The device with the smallest Ta2O5 thickness (0.5 nm) showed normal switching properties with gradual change in resistance in I-V sweep or CLPS and high reliability. By contrast, other devices with higher Ta2O5 thickness (1.0–2.0 nm) showed abrupt switching with several abnormal behaviours, degraded resistance distribution, especially in high resistance state, and much lower reliability performance. A single conical or hour-glass shaped double conical conducting filament shape was conceived to explain these behavioural differences that depended on the Ta2O5 switching layer thickness. Loss of oxygen via lateral diffusion to the encapsulating Si3N4/SiO2 layer was suggested as the main degradation mechanism for reliability, and a method to improve reliability was also proposed. PMID:26527044

  12. Functional Studies of Heading Date-Related Gene TaPRR73, a Paralog of Ppd1 in Common Wheat.

    PubMed

    Zhang, Wenping; Zhao, Guangyao; Gao, Lifeng; Kong, Xiuying; Guo, Zhiai; Wu, Bihua; Jia, Jizeng

    2016-01-01

    Photoperiod response-related genes play a crucial role in duration of the plant growth. In this study, we focused on TaPRR73, a paralog of "Green Revolution" gene Ppd1 (TaPRR37). We found that overexpression of the truncated TaPRR73 form lacking part of the N-terminal PR domain in transgenic rice promoted heading under long day conditions. Association analysis in common wheat verified that TaPRR73 was an important agronomic photoperiod response gene that significantly affected heading date and plant height; expression analysis proved that specific alleles of TaPRR73-A1 had highly expressed levels in earlier heading lines; the distribution of haplotypes indicated that one of these alleles had been selected in breeding programs. Our results demonstrated that TaPRR73 contributed to regulation of heading date in wheat and could be useful in wheat breeding and in broadening adaptation of the crop to new regions. PMID:27313595

  13. MRI-compatible Nb-60Ta-2Zr alloy for vascular stents: Electrochemical corrosion behavior in simulated plasma solution.

    PubMed

    Li, Hui-Zhe; Zhao, Xu; Xu, Jian

    2015-11-01

    Using revised simulated body fluid (r-SBF), the electrochemical corrosion behavior of an Nb-60Ta-2Zr alloy for MRI compatible vascular stents was characterized in vitro. As indicated by XPS analysis, the surface passive oxide film of approximately 1.3nm thickness was identified as a mixture of Nb2O5, Ta2O5 and ZrO2 after immersion in the r-SBF. The Nb-60Ta-2Zr alloy manifests a low corrosion rate and high polarization resistance similar to pure Nb and Ta, as shown by the potentiodynamic polarization curves and EIS. Unlike 316L stainless steel and the L605 Co-Cr alloy, no localized corrosion has been detected. Semiconducting property of passive film on the Nb-60Ta-2Zr alloy was identified as the n-type, with growth mechanism of high-field controlled growth. The excellent corrosion resistance in simulated human blood enviroment renders the Nb-60Ta-2Zr alloy promising as stent candidate material.

  14. Measurement and Modeling of Short and Medium Range Order in Amorphous Ta2O5 Thin Films

    NASA Astrophysics Data System (ADS)

    Shyam, Badri; Stone, Kevin H.; Bassiri, Riccardo; Fejer, Martin M.; Toney, Michael F.; Mehta, Apurva

    2016-08-01

    Amorphous films and coatings are rapidly growing in importance. Yet, there is a dearth of high-quality structural data on sub-micron films. Not understanding how these materials assemble at atomic scale limits fundamental insights needed to improve their performance. Here, we use grazing-incidence x-ray total scattering measurements to examine the atomic structure of the top 50-100 nm of Ta2O5 films; mirror coatings that show high promise to significantly improve the sensitivity of the next generation of gravitational-wave detectors. Our measurements show noticeable changes well into medium range, not only between crystalline and amorphous, but also between as-deposited, annealed and doped amorphous films. It is a further challenge to quickly translate the structural information into insights into mechanisms of packing and disorder. Here, we illustrate a modeling approach that allows translation of observed structural features to a physically intuitive packing of a primary structural unit based on a kinked Ta-O-Ta backbone. Our modeling illustrates how Ta-O-Ta units link to form longer 1D chains and even 2D ribbons, and how doping and annealing influences formation of 2D order. We also find that all the amorphousTa2O5 films studied in here are not just poorly crystalline but appear to lack true 3D order.

  15. Functional Studies of Heading Date-Related Gene TaPRR73, a Paralog of Ppd1 in Common Wheat

    PubMed Central

    Zhang, Wenping; Zhao, Guangyao; Gao, Lifeng; Kong, Xiuying; Guo, Zhiai; Wu, Bihua; Jia, Jizeng

    2016-01-01

    Photoperiod response-related genes play a crucial role in duration of the plant growth. In this study, we focused on TaPRR73, a paralog of “Green Revolution” gene Ppd1 (TaPRR37). We found that overexpression of the truncated TaPRR73 form lacking part of the N-terminal PR domain in transgenic rice promoted heading under long day conditions. Association analysis in common wheat verified that TaPRR73 was an important agronomic photoperiod response gene that significantly affected heading date and plant height; expression analysis proved that specific alleles of TaPRR73-A1 had highly expressed levels in earlier heading lines; the distribution of haplotypes indicated that one of these alleles had been selected in breeding programs. Our results demonstrated that TaPRR73 contributed to regulation of heading date in wheat and could be useful in wheat breeding and in broadening adaptation of the crop to new regions. PMID:27313595

  16. The Novel Wheat Transcription Factor TaNAC47 Enhances Multiple Abiotic Stress Tolerances in Transgenic Plants.

    PubMed

    Zhang, Lina; Zhang, Lichao; Xia, Chuan; Zhao, Guangyao; Jia, Jizeng; Kong, Xiuying

    2015-01-01

    NAC transcription factors play diverse roles in plant development and responses to abiotic stresses. However, the biological roles of NAC family members in wheat are not well understood. Here, we reported the isolation and functional characterization of a novel wheat TaNAC47 gene. TaNAC47 encoded protein, localizing in the nucleus, is able to bind to the ABRE cis-element and transactivate transcription in yeast, suggesting that it likely functions as a transcriptional activator. We also showed that TaNAC47 is differentially expressed in different tissues, and its expression was induced by the stress treatments of salt, cold, polyethylene glycol and exogenous abscisic acid. Furthermore, overexpression of TaNAC47 in Arabidopsis resulted in ABA hypersensitivity and enhancing tolerance of transgenic plants to drought, salt, and freezing stresses. Strikingly, overexpression of TaNAC47 was found to activate the expression of downstream genes and change several physiological indices that may enable transgenic plants to overcome unfavorable environments. Taken together, these results uncovered an important role of wheat TaNAC47 gene in response to ABA and abiotic stresses. PMID:26834757

  17. TaASR1, a transcription factor gene in wheat, confers drought stress tolerance in transgenic tobacco.

    PubMed

    Hu, Wei; Huang, Chao; Deng, Xiaomin; Zhou, Shiyi; Chen, Lihong; Li, Yin; Wang, Cheng; Ma, Zhanbing; Yuan, Qianqian; Wang, Yan; Cai, Rui; Liang, Xiaoyu; Yang, Guangxiao; He, Guangyuan

    2013-08-01

    Abscisic acid (ABA)-, stress-, and ripening-induced (ASR) proteins are reported to be involved in abiotic stresses. However, it is not known whether ASR genes confer drought stress tolerance by utilizing the antioxidant system. In this study, a wheat ASR gene, TaASR1, was cloned and characterized. TaASR1 transcripts increased after treatments with PEG6000, ABA and H(2)O(2). Overexpression of TaASR1 in tobacco resulted in increased drought/osmotic tolerance, which was demonstrated that transgenic lines had lesser malondialdehyde (MDA), ion leakage (IL) and reactive oxygen species (ROS), but higher relative water content (RWC) and superoxide dismutase (SOD) and catalase (CAT) activities than wild type (WT) under drought stress. Overexpression of TaASR1 in tobacco also enhanced the expression of ROS-related and stress-responsive genes under osmotic stress. In addition, transgenic lines exhibited improved tolerance to oxidative stress by retaining more effective antioxidant system. Finally, TaASR1 was localized in the cell nucleus and functioned as a transcriptional activator. Taken together, our results showed that TaASR1 functions as a positive factor under drought/osmotic stress, involved in the regulation of ROS homeostasis by activating antioxidant system and transcription of stress-associated genes. PMID:23356734

  18. Enhanced oxygen vacancy diffusion in Ta2O5 resistive memory devices due to infinitely adaptive crystal structure

    NASA Astrophysics Data System (ADS)

    Jiang, Hao; Stewart, Derek A.

    2016-04-01

    Metal oxide resistive memory devices based on Ta2O5 have demonstrated high switching speed, long endurance, and low set voltage. However, the physical origin of this improved performance is still unclear. Ta2O5 is an important archetype of a class of materials that possess an adaptive crystal structure that can respond easily to the presence of defects. Using first principles nudged elastic band calculations, we show that this adaptive crystal structure leads to low energy barriers for in-plane diffusion of oxygen vacancies in λ phase Ta2O5. Identified diffusion paths are associated with collective motion of neighboring atoms. The overall vacancy diffusion is anisotropic with higher diffusion barriers found for oxygen vacancy movement between Ta-O planes. Coupled with the fact that oxygen vacancy formation energy in Ta2O5 is relatively small, our calculated low diffusion barriers can help explain the low set voltage in Ta2O5 based resistive memory devices. Our work shows that other oxides with adaptive crystal structures could serve as potential candidates for resistive random access memory devices. We also discuss some general characteristics for ideal resistive RAM oxides that could be used in future computational material searches.

  19. Mesoporous Nb and Ta Oxides: Synthesis, Characterization and Applications in Heterogeneous Acid Catalysis

    NASA Astrophysics Data System (ADS)

    Rao, Yuxiang Tony

    In this work, a series of mesoporous Niobium and Tantalum oxides with different pore sizes (C6, C12, C18 , ranging from 12A to 30 A) were synthesized using the ligand-assisted templating approach and investigated for their activities in a wide range of catalytic applications including benzylation, alkylation and isomerization. The as-synthesized mesoporous materials were characterized by nitrogen adsorption, powder X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), and solid-state Nuclear magnetic resonance (NMR) techniques. In order to probe into the structural and coordination geometry of mesoporous Nb oxide and in efforts to make meaningful comparisons of mesoporous niobia prepared by the amine-templating method with the corresponding bulk sol-gel prepared Nb2O5 phase, 17O magic-angle-spinning solid-state NMR studies were conducted. The results showed a very high local order in the mesoporous sample. The oxygen atoms are coordinated only as ONb 2 in contrast with bulk phases in which the oxygen atoms are always present in a mixture of ONb2 and ONb3 coordination environments. To enhance their surface acidities and thus improve their performance as solid acid catalysts in the acid-catalyzed reactions mentioned above, pure mesoporous Nb and Ta oxides were further treated with 1M sulfuric acid or phosphoric acid. Their surface acidities before and after acid treatment were measured by Fourier transform infraRed (FT IR), amine titration and temperature programmed desorption of ammonia (NH3-TPD). Results obtained in this study showed that sulfated mesoporous Nb and Ta oxides materials possess relative high surface areas (up to 612 m 2/g) and amorphous wormhole structure. These mesoporous structures are thus quite stable to acid treatment. It was also found that Bronsted (1540 cm-1) and Lewis (1450 cm-1) acid sites coexist in a roughly 50:50 mixture

  20. Structural Geology of the Northwestern Portion of Los Alamos National Laboratory, Rio Grande Rift, New Mexico: Implications for Seismic Surface Rupture Potential from TA-3 to TA-55

    SciTech Connect

    Jamie N. Gardner: Alexis Lavine; Giday WoldeGabriel; Donathon Krier; David Vaniman; Florie Caporuscio; Claudia Lewis; Peggy Reneau; Emily Kluk; M. J. Snow

    1999-03-01

    Los Alamos National Laboratory lies at the western boundary of the Rio Grande rift, a major tectonic feature of the North American Continent. Three major faults locally constitute the modem rift boundary, and each of these is potentially seismogenic. In this study we have gathered structural geologic data for the northwestern portion of Los Alamos National Laboratory through high-precision geologic mapping, conventional geologic mapping, stratigraphic studies, drilling, petrologic studies, and stereographic aerial photograph analyses. Our study area encompasses TA-55 and TA-3, where potential for seismic surface rupture is of interest, and is bounded on the north and south by the townsite of Los Alamos and Twomile Canyon, respectively. The study area includes parts of two of the potentially active rift boundary faults--the Pajarito and Rendija Canyon faults-that form a large graben that we name the Diamond Drive graben. The graben embraces the western part of the townsite of Los Alamos, and its southern end is in the TA-3 area where it is defined by east-southeast-trending cross faults. The cross faults are small, but they accommodate interactions between the two major fault zones and gentle tilting of structural blocks to the north into the graben. North of Los Alamos townsite, the Rendija Canyon fault is a large normal fault with about 120 feet of down-to-the-west displacement over the last 1.22 million years. South from Los Alamos townsite, the Rendija Canyon fault splays to the southwest into a broad zone of deformation. The zone of deformation is about 2,000 feet wide where it crosses Los Alamos Canyon and cuts through the Los Alamos County Landfill. Farther southwest, the fault zone is about 3,000 feet wide at the southeastern corner of TA-3 in upper Mortandad Canyon and about 5,000 feet wide in Twomile Canyon. Net down-to-the-west displacement across the entire fault zone over the last 1.22 million years decreases to the south as the fault zone broadens as