WorldWideScience

Sample records for outflow modeled o3

  1. Sphalerons of O(3) nonlinear sigma model on a circle

    International Nuclear Information System (INIS)

    Funakubo, Koichi; Otsuki, Shoichiro; Toyoda, Fumihiko.

    1989-09-01

    A series of saddle point solutions of O(3) nonlinear sigma model with symmetry breaking term in 1 + 1 dimensions are obtained by imposing boundary condition either periodic or partially antiperiodic (O(3) sphalerons on a circle). Under the periodic boundary condition, classical features of the O(3) sphalerons are similar to scalar sphalerons of φ 4 model on a circle by Manton and Samols. Under the partially antiperiodic boundary condition, the lowest of the O(3) sphalerons coincides in the limit of infinite spatial domain with the O(3) sphaleron by Mottola and Wipf. In particular, zero and negative modes of them are examined in detail. An estimate of transition rate over the lowest O(3) sphaleron at finite temperature is made, and some remarks on simulating the transition on a lattice are given. One to one correspondence between these O(3) sphalerons on a circle and a series of (possible) classical solutions of SU(2) gauge-Higgs model, to which the electroweak sphaleron S and new sphaleron S* belong, is discussed. (author)

  2. Modeling jet and outflow feedback during star cluster formation

    Energy Technology Data Exchange (ETDEWEB)

    Federrath, Christoph [Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, VIC 3800 (Australia); Schrön, Martin [Department of Computational Hydrosystems, Helmholtz Centre for Environmental Research-UFZ, Permoserstr. 15, D-04318 Leipzig (Germany); Banerjee, Robi [Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg (Germany); Klessen, Ralf S., E-mail: christoph.federrath@monash.edu [Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik, Albert-Ueberle-Strasse 2, D-69120 Heidelberg (Germany)

    2014-08-01

    Powerful jets and outflows are launched from the protostellar disks around newborn stars. These outflows carry enough mass and momentum to transform the structure of their parent molecular cloud and to potentially control star formation itself. Despite their importance, we have not been able to fully quantify the impact of jets and outflows during the formation of a star cluster. The main problem lies in limited computing power. We would have to resolve the magnetic jet-launching mechanism close to the protostar and at the same time follow the evolution of a parsec-size cloud for a million years. Current computer power and codes fall orders of magnitude short of achieving this. In order to overcome this problem, we implement a subgrid-scale (SGS) model for launching jets and outflows, which demonstrably converges and reproduces the mass, linear and angular momentum transfer, and the speed of real jets, with ∼1000 times lower resolution than would be required without the SGS model. We apply the new SGS model to turbulent, magnetized star cluster formation and show that jets and outflows (1) eject about one-fourth of their parent molecular clump in high-speed jets, quickly reaching distances of more than a parsec, (2) reduce the star formation rate by about a factor of two, and (3) lead to the formation of ∼1.5 times as many stars compared to the no-outflow case. Most importantly, we find that jets and outflows reduce the average star mass by a factor of ∼ three and may thus be essential for understanding the characteristic mass of the stellar initial mass function.

  3. Symmetries and discretizations of the O(3) nonlinear sigma model

    Energy Technology Data Exchange (ETDEWEB)

    Flore, Raphael [TPI, Universitaet Jena (Germany)

    2011-07-01

    Nonlinear sigma models possess many interesting properties like asymptotic freedom, confinement or dynamical mass generation, and hence serve as toy models for QCD and other theories. We derive a formulation of the N=2 supersymmetric extension of the O(3) nonlinear sigma model in terms of constrained field variables. Starting from this formulation, it is discussed how the model can be discretized in a way that maintains as many symmetries of the theory as possible. Finally, recent numerical results related to these discretizations are presented.

  4. Modeling the outflow of liquid with initial supercritical parameters using the relaxation model for condensation

    Directory of Open Access Journals (Sweden)

    Lezhnin Sergey

    2017-01-01

    Full Text Available The two-temperature model of the outflow from a vessel with initial supercritical parameters of medium has been realized. The model uses thermodynamic non-equilibrium relaxation approach to describe phase transitions. Based on a new asymptotic model for computing the relaxation time, the outflow of water with supercritical initial pressure and super- and subcritical temperatures has been calculated.

  5. Thermodynamic modeling of La2O3-SrO-Mn2O3-Cr2O3 for solid oxide fuel cell applications

    DEFF Research Database (Denmark)

    Povoden-Karadeniz, E.; Chen, Ming; Ivas, Toni

    2012-01-01

    The thermodynamic La–Sr–Mn–Cr–O oxide database is obtained as an extension of thermodynamic descriptions of oxide subsystems using the calculation of phase diagrams approach. Concepts of the thermodynamic modeling of solid oxide phases are discussed. Gibbs energy functions of SrCrO4, Sr2.67Cr2O8......, Sr2CrO4, and SrCr2O4 are presented, and thermodynamic model parameters of La–Sr–Mn–Chromite perovskite are given. Experimental solid solubilities and nonstoichiometries in La1xSrxCrO3d and LaMn1xCrxO3d are reproduced by the model. The presented oxide database can be used for applied computational...... thermodynamics of traditional lanthanum manganite cathode with Cr-impurities. It represents the fundament for extensions to higher orders, aiming on thermodynamic calculations in noble symmetric solid oxide fuel cells...

  6. The microscopic model of BiFeO3

    Science.gov (United States)

    Fishman, R. S.

    2018-05-01

    Many years and great effort have been spent constructing the microscopic model for the room temperature multiferroic BiFeO3. However, earlier models implicitly assumed that the cycloidal wavevector q was confined to one of the three-fold symmetric axes in the hexagonal plane normal to the electric polarization. Because recent measurements indicate that q can be rotated by a magnetic field, it is essential to properly treat the anisotropy that confines q at low fields. We propose that the anisotropy energy -K3S6sin6 θ cos 6 ϕ confines the wavevectors q to the three-fold axis ϕ = 0 and ± 2 π / 3 within the hexagonal plane with θ = π / 2 .

  7. Modeling the Quiet Time Outflow Solution in the Polar Cap

    Science.gov (United States)

    Glocer, Alex

    2011-01-01

    We use the Polar Wind Outflow Model (PWOM) to study the geomagnetically quiet conditions in the polar cap during solar maximum, The PWOM solves the gyrotropic transport equations for O(+), H(+), and He(+) along several magnetic field lines in the polar region in order to reconstruct the full 3D solution. We directly compare our simulation results to the data based empirical model of Kitamura et al. [2011] of electron density, which is based on 63 months of Akebono satellite observations. The modeled ion and electron temperatures are also compared with a statistical compilation of quiet time data obtained by the EISCAT Svalbard Radar (ESR) and Intercosmos Satellites (Kitamura et al. [2011]). The data and model agree reasonably well. This study shows that photoelectrons play an important role in explaining the differences between sunlit and dark results, ion composition, as well as ion and electron temperatures of the quiet time polar wind solution. Moreover, these results provide validation of the PWOM's ability to model the quiet time ((background" solution.

  8. Lagrangian Photochemical Box-Model Calculations of Asian Pacific Rim Outflow During TRACE-P

    Science.gov (United States)

    Hamlin, A.; Crawford, J.; Olson, J.; Avery, M.; Sachse, G.; Barrick, J.; Blake, D.; Tan, D.; Sandholm, S.; Kondo, Y.; Singh, H.; Eisele, F.; Zondlo, M.; Flocke, F.; Talbot, R.

    2006-12-01

    NASA's TRACE-P (TRAnsport and Chemical Evolution over the Pacific) mission was conducted over the northwestern Pacific February-April, 2001. During two transit flights across the Pacific, extensive pollution was observed from an Asian outflow event that split into two branches over the central Pacific, one subsiding and moving southward over the central Pacific and the other continuing eastward in the upper troposphere. The subsiding branch was observed as a widespread stagnant pollution layer between 2 and 4 km over the central Pacific during transit flights from Kona, HI to Guam. In this region, high levels of O3 (70 ppbv), CO (217 ppbv), and NOx (114 pptv) were well in excess of typical values observed during TRACE-P along the Asian coast. Evidence suggests that the subsiding branch experienced extensive photochemical processing compared to the branch that remained at altitude. To examine the processes controlling the chemical evolution of ozone and its precursors in this outflow event, data collected during the TRACE-P mission have been combined with lagrangian photochemical box model calculations. One of the largest sources of uncertainty in these calculations was associated with predicted water vapor levels along the transport trajectories calculated using the HYSPLIT model. Water vapor levels predicted by HYSPLIT trajectory calculations in the subsiding layer ranged from 3390 to 4880 ppm, while the median level observed in the pollution layer was only 637 ppm. Simulations of ozone production and associated radical chemistry differed dramatically when using water vapor levels based on trajectory calculations versus observed water vapor levels. Levels of PAN and HO2NO2, NOx reservoir species, are also influenced by uncertainties in temperature along the trajectories. These results highlight the importance of accurately representing the humidification and warming of subsiding air masses in 3-D chemical- transport models.

  9. Coastal circulations driven by river outflow in a variable-density 1.5-layer model

    Digital Repository Service at National Institute of Oceanography (India)

    McCreary, J.P.; Zhang, S.; Shetye, S.R.

    A variable-density, 1.5-layer model is used to investigate the dynamics of the fresher-water plumes generated by river outflow. Solutions are found in a north-south channel, and the transport M sub(tau) and salinity S sub(tau) of the outflow...

  10. Data-Model and Inter-Model Comparisons of the GEM Outflow Events Using the Space Weather Modeling Framework

    Science.gov (United States)

    Welling, D. T.; Eccles, J. V.; Barakat, A. R.; Kistler, L. M.; Haaland, S.; Schunk, R. W.; Chappell, C. R.

    2015-12-01

    Two storm periods were selected by the Geospace Environment Modeling Ionospheric Outflow focus group for community collaborative study because of its high magnetospheric activity and extensive data coverage: the September 27 - October 4, 2002 corotating interaction region event and the October 22 - 29 coronal mass ejection event. During both events, the FAST, Polar, Cluster, and other missions made key observations, creating prime periods for data-model comparison. The GEM community has come together to simulate this period using many different methods in order to evaluate models, compare results, and expand our knowledge of ionospheric outflow and its effects on global dynamics. This paper presents Space Weather Modeling Framework (SWMF) simulations of these important periods compared against observations from the Polar TIDE, Cluster CODIF and EFW instruments. Emphasis will be given to the second event. Density and velocity of oxygen and hydrogen throughout the lobes, plasma sheet, and inner magnetosphere will be the focus of these comparisons. For these simulations, the SWMF couples the multifluid version of BATS-R-US MHD to a variety of ionospheric outflow models of varying complexity. The simplest is outflow arising from constant MHD inner boundary conditions. Two first-principles-based models are also leveraged: the Polar Wind Outflow Model (PWOM), a fluid treatment of outflow dynamics, and the Generalized Polar Wind (GPW) model, which combines fluid and particle-in-cell approaches. Each model is capable of capturing a different set of energization mechanisms, yielding different outflow results. The data-model comparisons will illustrate how well each approach captures reality and which energization mechanisms are most important. Inter-model comparisons will illustrate how the different outflow specifications affect the magnetosphere. Specifically, it is found that the GPW provides increased heavy ion outflow over a broader spatial range than the alternative

  11. Global O3-CO correlations in a chemistry and transport model during July-August: evaluation with TES satellite observations and sensitivity to input meteorological data and emissions

    Science.gov (United States)

    Choi, Hyun-Deok; Liu, Hongyu; Crawford, James H.; Considine, David B.; Allen, Dale J.; Duncan, Bryan N.; Horowitz, Larry W.; Rodriguez, Jose M.; Strahan, Susan E.; Zhang, Lin; Liu, Xiong; Damon, Megan R.; Steenrod, Stephen D.

    2017-07-01

    We examine the capability of the Global Modeling Initiative (GMI) chemistry and transport model to reproduce global mid-tropospheric (618 hPa) ozone-carbon monoxide (O3-CO) correlations determined by the measurements from the Tropospheric Emission Spectrometer (TES) aboard NASA's Aura satellite during boreal summer (July-August). The model is driven by three meteorological data sets (finite-volume General Circulation Model (fvGCM) with sea surface temperature for 1995, Goddard Earth Observing System Data Assimilation System Version 4 (GEOS-4 DAS) for 2005, and Modern-Era Retrospective Analysis for Research and Applications (MERRA) for 2005), allowing us to examine the sensitivity of model O3-CO correlations to input meteorological data. Model simulations of radionuclide tracers (222Rn, 210Pb, and 7Be) are used to illustrate the differences in transport-related processes among the meteorological data sets. Simulated O3 values are evaluated with climatological profiles from ozonesonde measurements and satellite tropospheric O3 columns. Despite the fact that the three simulations show significantly different global and regional distributions of O3 and CO concentrations, they show similar patterns of O3-CO correlations on a global scale. All model simulations sampled along the TES orbit track capture the observed positive O3-CO correlations in the Northern Hemisphere midlatitude continental outflow and the Southern Hemisphere subtropics. While all simulations show strong negative correlations over the Tibetan Plateau, northern Africa, the subtropical eastern North Pacific, and the Caribbean, TES O3 and CO concentrations at 618 hPa only show weak negative correlations over much narrower areas (i.e., the Tibetan Plateau and northern Africa). Discrepancies in regional O3-CO correlation patterns in the three simulations may be attributed to differences in convective transport, stratospheric influence, and subsidence, among other processes. To understand how various

  12. Model Research On Synthesis Of Al2O3-C Layers By MOCVD

    Directory of Open Access Journals (Sweden)

    Sawka A.

    2015-06-01

    Full Text Available These are model studies whose aim is to obtain information that would allow development of new technology for synthesizing monolayers of Al2O3-C with adjusted microstructure on cemented carbides. The Al2O3-C layer will constitute an intermediate layer on which the outer layer of Al2O3 without carbon is synthesized. The purpose of the intermediate layer is to block the cobalt diffusion to the synthesized outer layer of Al2O3 and to stop the diffusion of air oxygen to the substrate during the synthesis of the outer layer. This layer should be thin, continuous, dense and uniform in thickness.

  13. DO3SE model applicability and O3 flux performance compared to AOT40 for an O3-sensitive tropical tree species (Psidium guajava L. 'Paluma').

    Science.gov (United States)

    Assis, Pedro I L S; Alonso, Rocío; Meirelles, Sérgio T; Moraes, Regina M

    2015-07-01

    Phytotoxic ozone (O3) levels have been recorded in the Metropolitan Region of São Paulo (MRSP). Flux-based critical levels for O3 through stomata have been adopted for some northern hemisphere species, showing better accuracy than with accumulated ozone exposure above a threshold of 40 ppb (AOT40). In Brazil, critical levels for vegetation protection against O3 adverse effects do not exist. The study aimed to investigate the applicability of O3 deposition model (Deposition of Ozone for Stomatal Exchange (DO3SE)) to an O3-sensitive tropical tree species (Psidium guajava L. 'Paluma') under the MRSP environmental conditions, which are very unstable, and to assess the performance of O3 flux and AOT40 in relation to O3-induced leaf injuries. Stomatal conductance (g s) parameterization for 'Paluma' was carried out and used to calculate different rate thresholds (from 0 to 5 nmol O3 m(-2) projected leaf area (PLA) s(-1)) for the phytotoxic ozone dose (POD). The model performance was assessed through the relationship between the measured and modeled g sto. Leaf injuries were analyzed and associated with POD and AOT40. The model performance was satisfactory and significant (R (2) = 0.56; P < 0.0001; root-mean-square error (RMSE) = 116). As already expected, high AOT40 values did not result in high POD values. Although high POD values do not always account for more injuries, POD0 showed better performance than did AOT40 and other different rate thresholds for POD. Further investigation is necessary to improve our model and also to check if there is a critical level of ozone in which leaf injuries arise. The conclusion is that the DO3SE model for 'Paluma' is applicable in the MRSP as well as in temperate regions and may contribute to future directives.

  14. Centrifuge modeling of one-step outflow tests for unsaturated parameter estimations

    Directory of Open Access Journals (Sweden)

    H. Nakajima

    2006-01-01

    Full Text Available Centrifuge modeling of one-step outflow tests were carried out using a 2-m radius geotechnical centrifuge, and the cumulative outflow and transient pore water pressure were measured during the tests at multiple gravity levels. Based on the scaling laws of centrifuge modeling, the measurements generally showed reasonable agreement with prototype data calculated from forward simulations with input parameters determined from standard laboratory tests. The parameter optimizations were examined for three different combinations of input data sets using the test measurements. Within the gravity level examined in this study up to 40g, the optimized unsaturated parameters compared well when accurate pore water pressure measurements were included along with cumulative outflow as input data. With its capability to implement variety of instrumentations under well controlled initial and boundary conditions and to shorten testing time, the centrifuge modeling technique is attractive as an alternative experimental method that provides more freedom to set inverse problem conditions for the parameter estimation.

  15. Centrifuge modeling of one-step outflow tests for unsaturated parameter estimations

    Science.gov (United States)

    Nakajima, H.; Stadler, A. T.

    2006-10-01

    Centrifuge modeling of one-step outflow tests were carried out using a 2-m radius geotechnical centrifuge, and the cumulative outflow and transient pore water pressure were measured during the tests at multiple gravity levels. Based on the scaling laws of centrifuge modeling, the measurements generally showed reasonable agreement with prototype data calculated from forward simulations with input parameters determined from standard laboratory tests. The parameter optimizations were examined for three different combinations of input data sets using the test measurements. Within the gravity level examined in this study up to 40g, the optimized unsaturated parameters compared well when accurate pore water pressure measurements were included along with cumulative outflow as input data. With its capability to implement variety of instrumentations under well controlled initial and boundary conditions and to shorten testing time, the centrifuge modeling technique is attractive as an alternative experimental method that provides more freedom to set inverse problem conditions for the parameter estimation.

  16. A General Reliability Model for Ni-BaTiO3-Based Multilayer Ceramic Capacitors

    Science.gov (United States)

    Liu, Donhang

    2014-01-01

    The evaluation of multilayer ceramic capacitors (MLCCs) with Ni electrode and BaTiO3 dielectric material for potential space project applications requires an in-depth understanding of their reliability. A general reliability model for Ni-BaTiO3 MLCC is developed and discussed. The model consists of three parts: a statistical distribution; an acceleration function that describes how a capacitor's reliability life responds to the external stresses, and an empirical function that defines contribution of the structural and constructional characteristics of a multilayer capacitor device, such as the number of dielectric layers N, dielectric thickness d, average grain size, and capacitor chip size A. Application examples are also discussed based on the proposed reliability model for Ni-BaTiO3 MLCCs.

  17. Kinetic modeling of auroral ion outflows observed by the VISIONS sounding rocket

    Science.gov (United States)

    Albarran, R. M.; Zettergren, M. D.

    2017-12-01

    The VISIONS (VISualizing Ion Outflow via Neutral atom imaging during a Substorm) sounding rocket was launched on Feb. 7, 2013 at 8:21 UTC from Poker Flat, Alaska, into an auroral substorm with the objective of identifying the drivers and dynamics of the ion outflow below 1000km. Energetic ion data from the VISIONS polar cap boundary crossing show evidence of an ion "pressure cooker" effect whereby ions energized via transverse heating in the topside ionosphere travel upward and are impeded by a parallel potential structure at higher altitudes. VISIONS was also instrumented with an energetic neutral atom (ENA) detector which measured neutral particles ( 50-100 eV energy) presumably produced by charge-exchange with the energized outflowing ions. Hence, inferences about ion outflow may be made via remotely-sensing measurements of ENAs. This investigation focuses on modeling energetic outflowing ion distributions observed by VISIONS using a kinetic model. This kinetic model traces large numbers of individual particles, using a guiding-center approximation, in order to allow calculation of ion distribution functions and moments. For the present study we include mirror and parallel electric field forces, and a source of ion cyclotron resonance (ICR) wave heating, thought to be central to the transverse energization of ions. The model is initiated with a steady-state ion density altitude profile and Maxwellian velocity distribution characterizing the initial phase-space conditions for multiple particle trajectories. This project serves to advance our understanding of the drivers and particle dynamics in the auroral ionosphere and to improve data analysis methods for future sounding rocket and satellite missions.

  18. Cellular automaton model in the fundamental diagram approach reproducing the synchronized outflow of wide moving jams

    International Nuclear Information System (INIS)

    Tian, Jun-fang; Yuan, Zhen-zhou; Jia, Bin; Fan, Hong-qiang; Wang, Tao

    2012-01-01

    Velocity effect and critical velocity are incorporated into the average space gap cellular automaton model [J.F. Tian, et al., Phys. A 391 (2012) 3129], which was able to reproduce many spatiotemporal dynamics reported by the three-phase theory except the synchronized outflow of wide moving jams. The physics of traffic breakdown has been explained. Various congested patterns induced by the on-ramp are reproduced. It is shown that the occurrence of synchronized outflow, free outflow of wide moving jams is closely related with drivers time delay in acceleration at the downstream jam front and the critical velocity, respectively. -- Highlights: ► Velocity effect is added into average space gap cellular automaton model. ► The physics of traffic breakdown has been explained. ► The probabilistic nature of traffic breakdown is simulated. ► Various congested patterns induced by the on-ramp are reproduced. ► The occurrence of synchronized outflow of jams depends on drivers time delay.

  19. Champagne flutes and brandy snifters: modelling protostellar outflow-cloud chemical interfaces

    Science.gov (United States)

    Rollins, R. P.; Rawlings, J. M. C.; Williams, D. A.; Redman, M. P.

    2014-10-01

    A rich variety of molecular species has now been observed towards hot cores in star-forming regions and in the interstellar medium. An increasing body of evidence from millimetre interferometers suggests that many of these form at the interfaces between protostellar outflows and their natal molecular clouds. However, current models have remained unable to explain the origin of the observational bias towards wide-angled `brandy snifter' shaped outflows over narrower `champagne flute' shapes in carbon monoxide imaging. Furthermore, these wide-angled systems exhibit unusually high abundances of the molecular ion HCO+. We present results from a chemodynamic model of such regions where a rich chemistry arises naturally as a result of turbulent mixing between cold, dense molecular gas and the hot, ionized outflow material. The injecta drives a rich and rapid ion-neutral chemistry in qualitative and quantitative agreement with the observations. The observational bias towards wide-angled outflows is explained naturally by the geometry-dependent ion injection rate causing rapid dissociation of CO in the younger systems.

  20. Experimental Investigation and Thermodynamic Modeling of the B2O3-FeO-Fe2O3-Nd2O3 System for Recycling of NdFeB Magnet Scrap

    Science.gov (United States)

    Jakobsson, Lars Klemet; Tranell, Gabriella; Jung, In-Ho

    2017-02-01

    NdFeB magnet scrap is an alternative source of neodymium that could have a significantly lower impact on the environment than current mining and extraction processes. Neodymium can be readily oxidized in the presence of oxygen, which makes it easy to recover neodymium in oxide form. Thermochemical data and phase diagrams for neodymium oxide containing systems is, however, very limited. Thermodynamic modeling of the B2O3-FeO-Fe2O3-Nd2O3 system was hence performed to obtain accurate phase diagrams and thermochemical properties of the system. Key phase diagram experiments were also carried out for the FeO-Nd2O3 system in saturation with iron to improve the accuracy of the present modeling. The modified quasichemical model was used to describe the Gibbs energy of the liquid oxide phase. The Gibbs energy functions of the liquid phase and the solids were optimized to reproduce all available and reliable phase diagram data, and thermochemical properties of the system. Finally the optimized database was applied to calculate conditions for selective oxidation of neodymium from NdFeB magnet waste.

  1. A Model of Silicate Grain Nucleation and Growth in Circumstellar Outflows

    Science.gov (United States)

    Paquette, John A.; Ferguson, Frank T.; Nuth, Joseph A., III

    2011-01-01

    Based on its abundance, high bond energy, and recent measurements of its vapor pressure SiO is a natural candidate for dust nucleation in circumstellar outflows around asymptotic giant branch stars. In this paper, we describe a model of the nucleation and growth of silicate dust in such outflows. The sensitivity of the model to varying choices of poorly constrained chemical parameters is explored, and the merits of using scaled rather than classical nucleation theory are briefly considered, An elaboration of the model that includes magnesium and iron as growth species is then presented and discussed. The composition of the bulk of the grains derived from the model is consistent with olivines and pyroxenes, but somewhat metal-rich grains and very small, nearly pure SiO grains are also produced,

  2. Model for collimated outflows in molecular clouds and the case of HH 7-11

    Energy Technology Data Exchange (ETDEWEB)

    Silvestro, G; Ferrari, A; Rosner, R; Trussoni, E; Tsinganos, K

    1987-01-15

    Modelling is carried out for collimated outflows of high-velocity gas in molecular clouds, which is often observed to be associated with linear chains of optical emission knots. A wind-flow model is proposed to account for the phenomenon, based on the structural similarities between the outflows and jets from active galactic nuclei and quasars. The chain of Herbig-Haro objects HH7-11 is used to illustrate the proposal. The model is based on flows in a channel of variable cross-sectional area due to Kelvin-Helmholtz instabilities between the flow and the ambient medium. Solutions of the Mach number equation for such a channel are presented, which possess multiple critical points and shocks identified with observed optical knots. (U.K.).

  3. Quantification of flexoelectricity in PbTiO3/SrTiO3 superlattice polar vortices using machine learning and phase-field modeling.

    Science.gov (United States)

    Li, Q; Nelson, C T; Hsu, S-L; Damodaran, A R; Li, L-L; Yadav, A K; McCarter, M; Martin, L W; Ramesh, R; Kalinin, S V

    2017-11-13

    Flexoelectricity refers to electric polarization generated by heterogeneous mechanical strains, namely strain gradients, in materials of arbitrary crystal symmetries. Despite more than 50 years of work on this effect, an accurate identification of its coupling strength remains an experimental challenge for most materials, which impedes its wide recognition. Here, we show the presence of flexoelectricity in the recently discovered polar vortices in PbTiO 3 /SrTiO 3 superlattices based on a combination of machine-learning analysis of the atomic-scale electron microscopy imaging data and phenomenological phase-field modeling. By scrutinizing the influence of flexocoupling on the global vortex structure, we match theory and experiment using computer vision methodologies to determine the flexoelectric coefficients for PbTiO 3 and SrTiO 3 . Our findings highlight the inherent, nontrivial role of flexoelectricity in the generation of emergent complex polarization morphologies and demonstrate a viable approach to delineating this effect, conducive to the deeper exploration of both topics.

  4. Urban air quality modeling with full O 3-NO x-VOC chemistry: Implications for O 3 and PM air quality in a street canyon

    Science.gov (United States)

    Kim, Minjoong J.; Park, Rokjin J.; Kim, Jae-Jin

    2012-02-01

    We examine transport and chemical transformation of reactive pollutants on an urban street using a computation fluid dynamics (CFD) model coupled with full photochemistry of reactive pollutants. An extensive comparison between simulated results and observations is conducted to evaluate the model, focusing on a field campaign occurred in Dongfeng Middle Street in Guangzhou, China. Observed CO and NO concentrations vary diurnally following traffic volumes. The model captures this observed diurnal variation and magnitudes of CO concentrations successfully. However, simulated NO concentration is three times higher than observation. This high bias is significantly reduced in the sensitivity simulation with lower NO x emissions. We find that oxidation products of O 3 photochemistry such as NO 2 and O 3 vary differently from primary pollutants, indicating important effects of photochemical reactions on their fates. The model appears to reproduce observed O 3 and NO 2 variability with time and altitude. Our analysis shows that high NO x concentrations in the urban street canyon may efficiently produce aerosol nitrate in the presence of NH 3. Simulated inorganic NO 3- aerosol concentration reaches up to 0.3 μg m -3 in July but increases an order of magnitude higher at lower temperature that favors partitioning of gas-phase HNO 3 to aerosol-phase, implying a serious concern for urban air quality in winter.

  5. Numerical Modelling of the Czochralski Growth of β-Ga2O3

    Directory of Open Access Journals (Sweden)

    Wolfram Miller

    2017-01-01

    Full Text Available Our numerical modelling of the Czochralski growth of single crystalline β-Ga 2 O 3 crystals (monoclinic symmetry starts at the 2D heat transport analysis within the crystal growth furnace, proceeds with the 3D heat transport and fluid flow analysis in the crystal-melt-crucible arrangement and targets the 3D thermal stress analysis within the β-Ga 2 O 3 crystal. In order to perform the stress analysis, we measured the thermal expansion coefficients and the elastic stiffness coefficients in two samples of a β-Ga 2 O 3 crystal grown at IKZ. Additionally, we analyse published data of β-Ga 2 O 3 material properties and use data from literature for comparative calculations. The computations were performed by the software packages CrysMAS, CGsim, Ansys-cfx and comsol Multiphysics. By the hand of two different thermal expansion data sets and two different crystal orientations, we analyse the elastic stresses in terms of the von-Mises stress.

  6. A SEMI-ANALYTICAL LINE TRANSFER MODEL TO INTERPRET THE SPECTRA OF GALAXY OUTFLOWS

    International Nuclear Information System (INIS)

    Scarlata, C.; Panagia, N.

    2015-01-01

    We present a semi-analytical line transfer model, (SALT), to study the absorption and re-emission line profiles from expanding galactic envelopes. The envelopes are described as a superposition of shells with density and velocity varying with the distance from the center. We adopt the Sobolev approximation to describe the interaction between the photons escaping from each shell and the remainder of the envelope. We include the effect of multiple scatterings within each shell, properly accounting for the atomic structure of the scattering ions. We also account for the effect of a finite circular aperture on actual observations. For equal geometries and density distributions, our models reproduce the main features of the profiles generated with more complicated transfer codes. Also, our SALT line profiles nicely reproduce the typical asymmetric resonant absorption line profiles observed in starforming/starburst galaxies whereas these absorption profiles cannot be reproduced with thin shells moving at a fixed outflow velocity. We show that scattered resonant emission fills in the resonant absorption profiles, with a strength that is different for each transition. Observationally, the effect of resonant filling depends on both the outflow geometry and the size of the outflow relative to the spectroscopic aperture. Neglecting these effects will lead to incorrect values of gas covering fraction and column density. When a fluorescent channel is available, the resonant profiles alone cannot be used to infer the presence of scattered re-emission. Conversely, the presence of emission lines of fluorescent transitions reveals that emission filling cannot be neglected

  7. Shell model for BaTiO3-Bi(Zn1/2Ti1/2)O3 perovskite solid solutions

    Science.gov (United States)

    Vielma, J.; Jackson, D.; Roundy, D.; Schneider, G.

    2010-03-01

    Even though the composition of BaTiO3-Bi(Zn1/2Ti1/2)O3 perovskite solid solutions is similar to other ferroelectric compounds, the dielectric response is unusual. Results of permittivity measurements as a function of temperature show a diffuse phase transition indicative of a weakly coupled relaxor behavior.footnotetextC. C. Huang and D. P. Cann, J. Appl. Phys. 104, 024117 (2008) To investigate the weakly coupled relaxor behavior in these materials at intermediate length scales we are developing a newly calibrated shell model based on first-principles supercell calculations of both the solid solution and its compositional endpoints. Initial results for its phase diagram will presented.

  8. Discrete Bogomolny equations for the nonlinear O(3) σ model in 2+1 dimensions

    International Nuclear Information System (INIS)

    Leese, R.

    1989-01-01

    Discrete analogues of the topological charge and of the Bogomolny equations are constructed for the nonlinear O(3) σ model in 2+1 dimensions, subject to the restriction that the energy density be radially symmetric. These are then incorporated into a discretized version of the evolution equations. Using the discrete Bogomolny relations to construct the initial data for numerical simulations removes the ''lattice wobble'' sometimes observed at low kinetic energies. This feature is very important for the delicate question of instanton stability

  9. Unsuppressed fermion-number violation at high temperature: An O(3) model

    International Nuclear Information System (INIS)

    Mottola, E.; Wipf, A.

    1989-01-01

    The O(3) nonlinear σ model in 1+1 dimensions, modified by an explicit symmetry-breaking term, is presented as a model for baryon- and lepton-number violation in the standard electroweak theory. Although arguments based on the Atiyah-Singer index theorem and instanton physics apply to the model, we show by explicit calculations that the rate of chiral fermion-number violation due to the axial anomaly is entirely unsuppressed at sufficiently high temperatures. Our results apply to unbroken gauge theories as well and may require reevaluation of the role of instantons in high-temperature QCD

  10. Band alignment in organic devices: Photoemission studies of model oligomers on In2O3

    International Nuclear Information System (INIS)

    Blyth, R. I. R.; Duschek, R.; Koller, G.; Netzer, F. P.; Ramsey, M. G.

    2001-01-01

    The interfaces of In 2 O 3 , a model for indium - tin - oxide (ITO), with benzene, thiophene, and benzaldehyde, models for technologically important organic molecules, are studied using angle resolved ultraviolet photoemission and work function measurements. Band alignment diagrams for hypothetical Al/organic/ITO devices have been drawn, using values determined from this work and previously published studies of these molecules on Al(111). The similarity between the bonding of benzene and thiophene on Al(111) and In 2 O 3 , i.e., largely electrostatic, leads to near identical alignment at both metal and oxide interfaces. This indicates that clean Al and ITO will make a very poor electron/hole injecting pair. We suggest that the apparent efficiency of Al as an electron injecting contact in real devices is due to the presence of oxygen at the Al/organic interface. For benzaldehyde the interaction with In 2 O 3 is largely electrostatic, in contrast to the covalent bonds formed on Al(111). This leads to very different alignment at the Al and oxide interfaces, showing the importance of the particular organic - inorganic interaction in determining band alignment. [copyright] 2001 American Institute of Physics

  11. Inflow, Outflow, Yields, and Stellar Population Mixing in Chemical Evolution Models

    International Nuclear Information System (INIS)

    Andrews, Brett H.; Weinberg, David H.; Schönrich, Ralph; Johnson, Jennifer A.

    2017-01-01

    Chemical evolution models are powerful tools for interpreting stellar abundance surveys and understanding galaxy evolution. However, their predictions depend heavily on the treatment of inflow, outflow, star formation efficiency (SFE), the stellar initial mass function, the SN Ia delay time distribution, stellar yields, and stellar population mixing. Using flexCE, a flexible one-zone chemical evolution code, we investigate the effects of and trade-offs between parameters. Two critical parameters are SFE and the outflow mass-loading parameter, which shift the knee in [O/Fe]–[Fe/H] and the equilibrium abundances that the simulations asymptotically approach, respectively. One-zone models with simple star formation histories follow narrow tracks in [O/Fe]–[Fe/H] unlike the observed bimodality (separate high- α and low- α sequences) in this plane. A mix of one-zone models with inflow timescale and outflow mass-loading parameter variations, motivated by the inside-out galaxy formation scenario with radial mixing, reproduces the two sequences better than a one-zone model with two infall epochs. We present [X/Fe]–[Fe/H] tracks for 20 elements assuming three different supernova yield models and find some significant discrepancies with solar neighborhood observations, especially for elements with strongly metallicity-dependent yields. We apply principal component abundance analysis to the simulations and existing data to reveal the main correlations among abundances and quantify their contributions to variation in abundance space. For the stellar population mixing scenario, the abundances of α -elements and elements with metallicity-dependent yields dominate the first and second principal components, respectively, and collectively explain 99% of the variance in the model. flexCE is a python package available at https://github.com/bretthandrews/flexCE.

  12. Inflow, Outflow, Yields, and Stellar Population Mixing in Chemical Evolution Models

    Energy Technology Data Exchange (ETDEWEB)

    Andrews, Brett H. [PITT PACC, Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Weinberg, David H.; Schönrich, Ralph; Johnson, Jennifer A., E-mail: andrewsb@pitt.edu [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)

    2017-02-01

    Chemical evolution models are powerful tools for interpreting stellar abundance surveys and understanding galaxy evolution. However, their predictions depend heavily on the treatment of inflow, outflow, star formation efficiency (SFE), the stellar initial mass function, the SN Ia delay time distribution, stellar yields, and stellar population mixing. Using flexCE, a flexible one-zone chemical evolution code, we investigate the effects of and trade-offs between parameters. Two critical parameters are SFE and the outflow mass-loading parameter, which shift the knee in [O/Fe]–[Fe/H] and the equilibrium abundances that the simulations asymptotically approach, respectively. One-zone models with simple star formation histories follow narrow tracks in [O/Fe]–[Fe/H] unlike the observed bimodality (separate high- α and low- α sequences) in this plane. A mix of one-zone models with inflow timescale and outflow mass-loading parameter variations, motivated by the inside-out galaxy formation scenario with radial mixing, reproduces the two sequences better than a one-zone model with two infall epochs. We present [X/Fe]–[Fe/H] tracks for 20 elements assuming three different supernova yield models and find some significant discrepancies with solar neighborhood observations, especially for elements with strongly metallicity-dependent yields. We apply principal component abundance analysis to the simulations and existing data to reveal the main correlations among abundances and quantify their contributions to variation in abundance space. For the stellar population mixing scenario, the abundances of α -elements and elements with metallicity-dependent yields dominate the first and second principal components, respectively, and collectively explain 99% of the variance in the model. flexCE is a python package available at https://github.com/bretthandrews/flexCE.

  13. Global O3–CO correlations in a chemistry and transport model during July–August: evaluation with TES satellite observations and sensitivity to input meteorological data and emissions

    Directory of Open Access Journals (Sweden)

    H.-D. Choi

    2017-07-01

    Full Text Available We examine the capability of the Global Modeling Initiative (GMI chemistry and transport model to reproduce global mid-tropospheric (618 hPa ozone–carbon monoxide (O3–CO correlations determined by the measurements from the Tropospheric Emission Spectrometer (TES aboard NASA's Aura satellite during boreal summer (July–August. The model is driven by three meteorological data sets (finite-volume General Circulation Model (fvGCM with sea surface temperature for 1995, Goddard Earth Observing System Data Assimilation System Version 4 (GEOS-4 DAS for 2005, and Modern-Era Retrospective Analysis for Research and Applications (MERRA for 2005, allowing us to examine the sensitivity of model O3–CO correlations to input meteorological data. Model simulations of radionuclide tracers (222Rn, 210Pb, and 7Be are used to illustrate the differences in transport-related processes among the meteorological data sets. Simulated O3 values are evaluated with climatological profiles from ozonesonde measurements and satellite tropospheric O3 columns. Despite the fact that the three simulations show significantly different global and regional distributions of O3 and CO concentrations, they show similar patterns of O3–CO correlations on a global scale. All model simulations sampled along the TES orbit track capture the observed positive O3–CO correlations in the Northern Hemisphere midlatitude continental outflow and the Southern Hemisphere subtropics. While all simulations show strong negative correlations over the Tibetan Plateau, northern Africa, the subtropical eastern North Pacific, and the Caribbean, TES O3 and CO concentrations at 618 hPa only show weak negative correlations over much narrower areas (i.e., the Tibetan Plateau and northern Africa. Discrepancies in regional O3–CO correlation patterns in the three simulations may be attributed to differences in convective transport, stratospheric influence, and subsidence, among other processes. To

  14. Hemoglobin as a nitrite anhydrase: modeling methemoglobin-mediated N2O3 formation.

    Science.gov (United States)

    Hopmann, Kathrin H; Cardey, Bruno; Gladwin, Mark T; Kim-Shapiro, Daniel B; Ghosh, Abhik

    2011-05-27

    Nitrite has recently been recognized as a storage form of NO in blood and as playing a key role in hypoxic vasodilation. The nitrite ion is readily reduced to NO by hemoglobin in red blood cells, which, as it happens, also presents a conundrum. Given NO's enormous affinity for ferrous heme, a key question concerns how it escapes capture by hemoglobin as it diffuses out of the red cells and to the endothelium, where vasodilation takes place. Dinitrogen trioxide (N(2)O(3)) has been proposed as a vehicle that transports NO to the endothelium, where it dissociates to NO and NO(2). Although N(2)O(3) formation might be readily explained by the reaction Hb-Fe(3+)+NO(2)(-)+NO⇌Hb-Fe(2+)+N(2)O(3), the exact manner in which methemoglobin (Hb-Fe(3+)), nitrite and NO interact with one another is unclear. Both an "Hb-Fe(3+)-NO(2)(-)+NO" pathway and an "Hb-Fe(3+)-NO+NO(2)(-) " pathway have been proposed. Neither pathway has been established experimentally. Nor has there been any attempt until now to theoretically model N(2)O(3) formation, the so-called nitrite anhydrase reaction. Both pathways have been examined here in a detailed density functional theory (DFT, B3LYP/TZP) study and both have been found to be feasible based on energetics criteria. Modeling the "Hb-Fe(3+)-NO(2)(-)+NO" pathway proved complex. Not only are multiple linkage-isomeric (N- and O-coordinated) structures conceivable for methemoglobin-nitrite, multiple isomeric forms are also possible for N(2)O(3) (the lowest-energy state has an N-N-bonded nitronitrosyl structure, O(2)N-NO). We considered multiple spin states of methemoglobin-nitrite as well as ferromagnetic and antiferromagnetic coupling of the Fe(3+) and NO spins. Together, the isomerism and spin variables result in a diabolically complex combinatorial space of reaction pathways. Fortunately, transition states could be successfully calculated for the vast majority of these reaction channels, both M(S)=0 and M(S)=1. For a six-coordinate Fe(3+)-O

  15. Forecasting Inflow and Outflow of Money Currency in East Java Using a Hybrid Exponential Smoothing and Calendar Variation Model

    Science.gov (United States)

    Susanti, Ana; Suhartono; Jati Setyadi, Hario; Taruk, Medi; Haviluddin; Pamilih Widagdo, Putut

    2018-03-01

    Money currency availability in Bank Indonesia can be examined by inflow and outflow of money currency. The objective of this research is to forecast the inflow and outflow of money currency in each Representative Office (RO) of BI in East Java by using a hybrid exponential smoothing based on state space approach and calendar variation model. Hybrid model is expected to generate more accurate forecast. There are two studies that will be discussed in this research. The first studies about hybrid model using simulation data that contain pattern of trends, seasonal and calendar variation. The second studies about the application of a hybrid model for forecasting the inflow and outflow of money currency in each RO of BI in East Java. The first of results indicate that exponential smoothing model can not capture the pattern calendar variation. It results RMSE values 10 times standard deviation of error. The second of results indicate that hybrid model can capture the pattern of trends, seasonal and calendar variation. It results RMSE values approaching the standard deviation of error. In the applied study, the hybrid model give more accurate forecast for five variables : the inflow of money currency in Surabaya, Malang, Jember and outflow of money currency in Surabaya and Kediri. Otherwise, the time series regression model yields better for three variables : outflow of money currency in Malang, Jember and inflow of money currency in Kediri.

  16. Renormalization of the nonlinear O(3) model with θ-term

    Energy Technology Data Exchange (ETDEWEB)

    Flore, Raphael, E-mail: raphael.flore@uni-jena.de [Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, D-07743 Jena (Germany)

    2013-05-11

    The renormalization of the topological term in the two-dimensional nonlinear O(3) model is studied by means of the Functional Renormalization Group. By considering the topological charge as a limit of a more general operator, it is shown that a finite multiplicative renormalization occurs in the extreme infrared. In order to compute the effects of the zero modes, a specific representation of the Clifford algebra is developed which allows to reformulate the bosonic problem in terms of Dirac operators and to employ the index theorem.

  17. Kinetic Framework for the Magnetosphere-Ionosphere-Plasmasphere-Polar Wind System: Modeling Ion Outflow

    Science.gov (United States)

    Schunk, R. W.; Barakat, A. R.; Eccles, V.; Karimabadi, H.; Omelchenko, Y.; Khazanov, G. V.; Glocer, A.; Kistler, L. M.

    2014-12-01

    A Kinetic Framework for the Magnetosphere-Ionosphere-Plasmasphere-Polar Wind System is being developed in order to provide a rigorous approach to modeling the interaction of hot and cold particle interactions. The framework will include ion and electron kinetic species in the ionosphere, plasmasphere and polar wind, and kinetic ion, super-thermal electron and fluid electron species in the magnetosphere. The framework is ideally suited to modeling ion outflow from the ionosphere and plasmasphere, where a wide range for fluid and kinetic processes are important. These include escaping ion interactions with (1) photoelectrons, (2) cusp/auroral waves, double layers, and field-aligned currents, (3) double layers in the polar cap due to the interaction of cold ionospheric and hot magnetospheric electrons, (4) counter-streaming ions, and (5) electromagnetic wave turbulence. The kinetic ion interactions are particularly strong during geomagnetic storms and substorms. The presentation will provide a brief description of the models involved and discuss the effect that kinetic processes have on the ion outflow.

  18. Assimilation of surface NO2 and O3 observations into the SILAM chemistry transport model

    Science.gov (United States)

    Vira, J.; Sofiev, M.

    2015-02-01

    This paper describes the assimilation of trace gas observations into the chemistry transport model SILAM (System for Integrated modeLling of Atmospheric coMposition) using the 3D-Var method. Assimilation results for the year 2012 are presented for the prominent photochemical pollutants ozone (O3) and nitrogen dioxide (NO2). Both species are covered by the AirBase observation database, which provides the observational data set used in this study. Attention was paid to the background and observation error covariance matrices, which were obtained primarily by the iterative application of a posteriori diagnostics. The diagnostics were computed separately for 2 months representing summer and winter conditions, and further disaggregated by time of day. This enabled the derivation of background and observation error covariance definitions, which included both seasonal and diurnal variation. The consistency of the obtained covariance matrices was verified using χ2 diagnostics. The analysis scores were computed for a control set of observation stations withheld from assimilation. Compared to a free-running model simulation, the correlation coefficient for daily maximum values was improved from 0.8 to 0.9 for O3 and from 0.53 to 0.63 for NO2.

  19. Winding transitions at finite energy and temperature: An O(3) model

    International Nuclear Information System (INIS)

    Habib, S.; Mottola, E.; Tinyakov, P.

    1996-01-01

    Winding number transitions in the two-dimensional softly broken O(3) nonlinear σ model are studied at finite energy and temperature. New periodic instanton solutions which dominate the semiclassical transition amplitudes are found analytically at low energies, and numerically for all energies up to the sphaleron scale. The Euclidean period β of these finite energy instantons increases with energy, contrary to the behavior found in the Abelian Higgs model or simple one-dimensional systems. This results in a sharp crossover from instanton-dominated tunneling to sphaleron-dominated thermal activation at a certain critical temperature. Since this behavior is traceable to the soft breaking of conformal invariance by the mass term in the σ model, semiclassical winding number transition amplitudes in the electroweak theory in 3+1 dimensions should exhibit a similar sharp crossover. We argue that this is indeed the case in the standard model for M H W . copyright 1996 The American Physical Society

  20. Observation-based modelling and analysis of O3 Production in the Seoul Metropolitan Area during KORUS-AQ

    Science.gov (United States)

    Schroeder, J.; Crawford, J. H.; Fried, A.; Weinheimer, A. J.; Blake, D. R.; Blake, N. J.; Wisthaler, A.; Lee, G.; Ahn, J. Y.

    2017-12-01

    The Seoul Metropolitan Area (SMA) has a population of 24 million and frequently experiences unhealthy levels of ozone (O3). In this work, data from the Korea-United States Air Quality Study (KORUS-AQ, May 2 - June 11, 2016) were used to constrain a 0-D photochemical box model, allowing for calculation of key photochemical parameters related to O3 chemistry in the SMA. During KORUS-AQ, the NASA DC-8 flew 20 research flights over the Korean Peninsula. Routine overflights of the SMA in the morning, midday, and afternoon allowed for evaluation of diurnal photochemical tendencies in both the urban core of Seoul and surrounding areas. During KORUS-AQ, the SMA experienced 39 days where the max 8-hour O3 exceeded the Korean AQS value of 60 ppbv. Box model calculations constrained with high-frequency data from the DC-8 show that rates of net O3 production (P(O3)) in urban Seoul were similar to outlying metropolitan areas across all times of day, with the highest median values occurring around midday in both cases ( 15 ppbv/hr). Although mixing ratios of key ozone precursors such as NOx and reactive VOCs were substantially higher in urban Seoul than outlying areas, net P(O3) was sustained across the region due to non-linearities in O3 chemistry. Box model calculations show that urban Seoul was strongly radical-limited, while outlying areas were either slightly NOx-limited or near the `transition' area. This suggests that P(O3) can be mitigated in urban Seoul by reducing VOC emissions, but regional air quality would benefit from reductions in both NOx and VOCs. Box model simulations of the response of P(O3) to omitting select VOCs suggest that reactive aromatics - particularly toluene, which had a median mixing ratio of 2 ppbv across SMA - contributed most to radical abundances ( 60%) and P(O3), and reductions in aromatic emissions would be most effective towards reducing P(O3). Biogenics and light alkenes account for 25% and 10% of radical abundances in the SMA, respectively

  1. Numerical simulations of the O(3) and CP1 models using the Langevin equations and the Metropolis algorithm

    International Nuclear Information System (INIS)

    Abdalla, E.; Carneiro, C.E.I.

    1988-12-01

    The O(3) model, the pure CP 1 model and the CP 1 model minimally coupled to fermions are numerically simulated. The equivalence between the O(3) and the bound state of the pure CP 1 model is investigated. It is shown that: the relations g O(3 ) = 2 g CP 1 and E O(3 )= 2E CP 1 + 2, for the coupling constants and energies hold beyond the classical level; the mass gap as a function of the coupling is the same for both models. The mass gap for the CP 1 minimally coupled to fermions is also calculated. The calculations are performed using different techniques. The proposal by Namiki and colaborators to enforce constraints on Langevin equations and Parisi's technique to calculate correlation functions via Langevin equations is tested. The results are compared with those obtained using the multi-hit Metropolis algorithm. (author) [pt

  2. Investigation of process variables and intensification effects of ultrasound applied in oxidative desulfurization of model diesel over MoO3/Al2O3 catalyst.

    Science.gov (United States)

    Akbari, Azam; Omidkhah, Mohammadreza; Darian, Jafar Towfighi

    2014-03-01

    A new heterogeneous sonocatalytic system consisting of a MoO3/Al2O3 catalyst and H2O2 combined with ultrasonication was studied to improve and accelerate the oxidation of model sulfur compounds of diesel, resulting in a significant enhancement in the process efficiency. The influence of ultrasound on properties, activity and stability of the catalyst was studied in detail by means of GC-FID, PSD, SEM and BET techniques. Above 98% conversion of DBT in model diesel containing 1000 μg/g sulfur was obtained by new ultrasound-assisted desulfurization at H2O2/sulfur molar ratio of 3, temperature of 318 K and catalyst dosage of 30 g/L after 30 min reaction, contrary to the 55% conversion obtained during the silent process. This improvement was considerably affected by operation parameters and catalyst properties. The effects of main process variables were investigated using response surface methodology in silent process compared to ultrasonication. Ultrasound provided a good dispersion of catalyst and oxidant by breakage of hydrogen bonding and deagglomeration of them in the oil phase. Deposition of impurities on the catalyst surface caused a quick deactivation in silent experiments resulting only 5% of DBT oxidation after 6 cycles of silent reaction by recycled catalyst. Above 95% of DBT was oxidized after 6 ultrasound-assisted cycles showing a great improvement in stability by cleaning the surface during ultrasonication. A considerable particle size reduction was also observed after 3 h sonication that could provide more dispersion of catalyst in model fuel.

  3. Revisiting the O(3) non-linear sigma model and its Pohlmeyer reduction

    Energy Technology Data Exchange (ETDEWEB)

    Pastras, Georgios [NCSR ' ' Demokritos' ' , Institute of Nuclear and Particle Physics, Attiki (Greece)

    2018-01-15

    It is well known that sigma models in symmetric spaces accept equivalent descriptions in terms of integrable systems, such as the sine-Gordon equation, through Pohlmeyer reduction. In this paper, we study the mapping between known solutions of the Euclidean O(3) non-linear sigma model, such as instantons, merons and elliptic solutions that interpolate between the latter, and solutions of the Pohlmeyer reduced theory, namely the sinh-Gordon equation. It turns out that instantons do not have a counterpart, merons correspond to the ground state, while the class of elliptic solutions is characterized by a two to one correspondence between solutions in the two descriptions. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. NOx and O3 above a tropical rainforest: an analysis with a global and box model

    Directory of Open Access Journals (Sweden)

    C. E. Reeves

    2010-11-01

    Full Text Available A cross-platform field campaign, OP3, was conducted in the state of Sabah in Malaysian Borneo between April and July of 2008. Among the suite of observations recorded, the campaign included measurements of NOx and O3 – crucial outputs of any model chemistry mechanism. We describe the measurements of these species made from both the ground site and aircraft. We then use the output from two resolutions of the chemistry transport model p-TOMCAT to illustrate the ability of a global model chemical mechanism to capture the chemistry at the rainforest site. The basic model performance is good for NOx and poor for ozone. A box model containing the same chemical mechanism is used to explore the results of the global model in more depth and make comparisons between the two. Without some parameterization of the nighttime boundary layer – free troposphere mixing (i.e. the use of a dilution parameter, the box model does not reproduce the observations, pointing to the importance of adequately representing physical processes for comparisons with surface measurements. We conclude with a discussion of box model budget calculations of chemical reaction fluxes, deposition and mixing, and compare these results to output from p-TOMCAT. These show the same chemical mechanism behaves similarly in both models, but that emissions and advection play particularly strong roles in influencing the comparison to surface measurements.

  5. A two-dimensional atmospheric chemistry modeling investigation of Earth's Phanerozoic O3 and near-surface ultraviolet radiation history

    Science.gov (United States)

    Harfoot, Michael B. J.; Beerling, David J.; Lomax, Barry H.; Pyle, John A.

    2007-04-01

    We use the Cambridge two-dimensional (2-D) chemistry-radiation transport model to investigate the implications for column O3 and near-surface ultraviolet radiation (UV), of variations in atmospheric O2 content over the Phanerozoic (last 540 Myr). Model results confirm some earlier 1-D model investigations showing that global annual mean O3 column increases monotonically with atmospheric O2. Sensitivity studies indicate that changes in temperature and N2O exert a minor influence on O3 relative to O2. We reconstructed Earth's O3 history by interpolating the modeled relationship between O3 and O2 onto two Phanerozoic O2 histories. Our results indicate that the largest variation in Phanerozoic column O3 occurred between 400 and 200 Myr ago, corresponding to a rise in atmospheric O2 to ˜1.5 times the present atmospheric level (PAL) and subsequent fall to ˜0.5 PAL. The O3 response to this O2 decline shows latitudinal differences, thinning most at high latitudes (30-40 Dobson units (1 DU = 0.001 atm cm) at 66°N) and least at low latitudes (5-10 DU at 9°N) where a "self-healing" effect is evident. This O3 depletion coincides with significant increases in the near-surface biologically active UV radiation at high latitudes, +28% as weighted by the Thimijan spectral weighting function. O3 and UV changes were exacerbated when we incorporated a direct feedback of the terrestrial biosphere on atmospheric chemistry, through enhanced N2O production as the climate switched from an icehouse to a greenhouse mode. On the basis of a summary of field and laboratory experimental evidence, we suggest that these UV radiation increases may have exerted subtle rather than catastrophic effects on ecosystem processes.

  6. Long-term O3–precursor relationships in Hong Kong: field observation and model simulation

    Directory of Open Access Journals (Sweden)

    Y. Wang

    2017-09-01

    Full Text Available Over the past 10 years (2005–2014, ground-level O3 in Hong Kong has consistently increased in all seasons except winter, despite the yearly reduction of its precursors, i.e. nitrogen oxides (NOx =  NO + NO2, total volatile organic compounds (TVOCs, and carbon monoxide (CO. To explain the contradictory phenomena, an observation-based box model (OBM coupled with CB05 mechanism was applied in order to understand the influence of both locally produced O3 and regional transport. The simulation of locally produced O3 showed an increasing trend in spring, a decreasing trend in autumn, and no changes in summer and winter. The O3 increase in spring was caused by the net effect of more rapid decrease in NO titration and unchanged TVOC reactivity despite decreased TVOC mixing ratios, while the decreased local O3 formation in autumn was mainly due to the reduction of aromatic VOC mixing ratios and the TVOC reactivity and much slower decrease in NO titration. However, the decreased in situ O3 formation in autumn was overridden by the regional contribution, resulting in elevated O3 observations. Furthermore, the OBM-derived relative incremental reactivity indicated that the O3 formation was VOC-limited in all seasons, and that the long-term O3 formation was more sensitive to VOCs and less to NOx and CO in the past 10 years. In addition, the OBM results found that the contributions of aromatics to O3 formation decreased in all seasons of these years, particularly in autumn, probably due to the effective control of solvent-related sources. In contrast, the contributions of alkenes increased, suggesting a continuing need to reduce traffic emissions. The findings provide updated information on photochemical pollution and its impact in Hong Kong.

  7. Off-shell dynamics of the O(3) NLS model beyond Monte Carlo and perturbation theory

    International Nuclear Information System (INIS)

    Balog, J.; Niedermaier, M.

    1997-01-01

    The off-shell dynamics of the O(3) non-linear sigma model is probed in terms of spectral densities and two-point functions by means of the form factor approach. The exact form factors of the spin field, Noether current, EM tensor and the topological charge density are computed up to six particles. The corresponding n≤6 particle spectral densities are used to compute the two-point functions, and are argued to deviate at most a few per mille from the exact answer in the entire energy range below 10 3 in units of the mass gap. To cover yet higher energies we propose an extrapolation scheme to arbitrary particle numbers based on a novel scaling hypothesis for the spectral densities. It yields candidate results for the exact two-point functions at all energy scales and allows us to exactly determine the values of two, previously unknown, non-perturbative constants. (orig.)

  8. Vector autoregressive model approach for forecasting outflow cash in Central Java

    Science.gov (United States)

    hoyyi, Abdul; Tarno; Maruddani, Di Asih I.; Rahmawati, Rita

    2018-05-01

    Multivariate time series model is more applied in economic and business problems as well as in other fields. Applications in economic problems one of them is the forecasting of outflow cash. This problem can be viewed globally in the sense that there is no spatial effect between regions, so the model used is the Vector Autoregressive (VAR) model. The data used in this research is data on the money supply in Bank Indonesia Semarang, Solo, Purwokerto and Tegal. The model used in this research is VAR (1), VAR (2) and VAR (3) models. Ordinary Least Square (OLS) is used to estimate parameters. The best model selection criteria use the smallest Akaike Information Criterion (AIC). The result of data analysis shows that the AIC value of VAR (1) model is equal to 42.72292, VAR (2) equals 42.69119 and VAR (3) equals 42.87662. The difference in AIC values is not significant. Based on the smallest AIC value criteria, the best model is the VAR (2) model. This model has satisfied the white noise assumption.

  9. Effect of phase interaction on catalytic CO oxidation over the SnO_2/Al_2O_3 model catalyst

    International Nuclear Information System (INIS)

    Chai, Shujing; Bai, Xueqin; Li, Jing; Liu, Cheng; Ding, Tong; Tian, Ye; Liu, Chang; Xian, Hui; Mi, Wenbo; Li, Xingang

    2017-01-01

    Highlights: • Activity for CO oxidation is greatly enhanced by interaction between SnO_2 and Al_2O_3. • Interaction between SnO_2 and Al_2O_3 phases can generate oxygen vacancies. • Oxygen vacancies play an import role for catalytic CO oxidation. • Sn"4"+ cations are the effective sites for catalytic CO oxidation. • Langmuir-Hinshelwood model is preferred for catalytic CO oxidation. - Abstract: We investigated the catalytic CO oxidation over the SnO_2/Al_2O_3 model catalysts. Our results show that interaction between the Al_2O_3 and SnO_2 phases results in the significantly improved catalytic activity because of the formation of the oxygen vacancies. The oxygen storage capacity of the SnO_2/Al_2O_3 catalyst prepared by the physically mixed method is nearly two times higher than that of the SnO_2, which probably results from the change of electron concentration on the interface of the SnO_2 and Al_2O_3 phases. Introducing water vapor to the feeding gas would a little decrease the activity of the catalysts, but the reaction rate could completely recover after removal of water vapor. The kinetics results suggest that the surface Sn"4"+ cations are effective CO adsorptive sites, and the surface adsorbed oxygen plays an important role upon CO oxidation. The reaction pathways upon the SnO_2-based catalysts for CO oxidation follow the Langmuir-Hinshelwood model.

  10. MLP based models to predict PM10, O3 concentrations, in Sines industrial area

    Science.gov (United States)

    Durao, R.; Pereira, M. J.

    2012-04-01

    Sines is an important Portuguese industrial area located southwest cost of Portugal with important nearby protected natural areas. The main economical activities are related with this industrial area, the deep-water port, petrochemical and thermo-electric industry. Nevertheless, tourism is also an important economic activity especially in summer time with potential to grow. The aim of this study is to develop prediction models of pollutant concentration categories (e.g. low concentration and high concentration) in order to provide early warnings to the competent authorities who are responsible for the air quality management. The knowledge in advanced of pollutant high concentrations occurrence will allow the implementation of mitigation actions and the release of precautionary alerts to population. The regional air quality monitoring network consists in three monitoring stations where a set of pollutants' concentrations are registered on a continuous basis. From this set stands out the tropospheric ozone (O3) and particulate matter (PM10) due to the high concentrations occurring in the region and their adverse effects on human health. Moreover, the major industrial plants of the region monitor SO2, NO2 and particles emitted flows at the principal chimneys (point sources), also on a continuous basis,. Therefore Artificial neuronal networks (ANN) were the applied methodology to predict next day pollutant concentrations; due to the ANNs structure they have the ability to capture the non-linear relationships between predictor variables. Hence the first step of this study was to apply multivariate exploratory techniques to select the best predictor variables. The classification trees methodology (CART) was revealed to be the most appropriate in this case.. Results shown that pollutants atmospheric concentrations are mainly dependent on industrial emissions and a complex combination of meteorological factors and the time of the year. In the second step, the Multi

  11. The outflow of radionuclides from Novaya Zemlya bays. Modeling and monitoring strategies

    International Nuclear Information System (INIS)

    Harms, I.H.; Povinec, P.P.

    1999-01-01

    Hydrodynamic model results are used to evaluate possible monitoring strategies for a continuous survey of underwater dump sites. The Hamburg Shelf Ocean Model (HAMSOM) is applied to Abrosimov Bay and forced with realistic, transient wind fields and air temperatures. The three-dimensional circulation model is coupled to a dynamic-thermodynamic ice model that accounts for surface heat fluxes, fractional ice cover and ice thickness. Model results show significant variations in the bay circulation due to a pronounced seasonality in the wind forcing and the ice cover. The circulation is weakest in early summer when wind speeds are low and the ice still covers most parts of the bay. In autumn, circulation and flushing of the bay is most enhanced, due to increasing wind speeds and the absence of an ice cover. Dispersion scenarios were carried out assuming a leakage at dumped objects. During most of the year the obtained tracer concentrations in the bay are higher in the upper layers than close to the bottom, indicating an outflow at the surface and a compensatory inflow below. This general pattern is only reversed during spring and early summer, when the wind directions change. Since ice problems make it almost impossible to monitor surface waters or even the whole water column in a shallow bay, the only way to install a monitoring system, is at the bottom of the bay, as close as possible to dumped objects. Data transmission via satellite or radio could be realized from a small station located on the bay's edge

  12. The outflow of radionuclides from Novaya Zemlya bays--modeling and monitoring strategies.

    Science.gov (United States)

    Harms, I H; Povinec, P P

    1999-09-30

    Hydrodynamic model results are used to evaluate possible monitoring strategies for a continuous survey of underwater dump sites. The Hamburg Shelf Ocean Model (HAMSOM) is applied to Abrosimov Bay and forced with realistic, transient wind fields and air temperatures. The three-dimensional circulation model is coupled to a dynamic-thermodynamic ice model that accounts for surface heat fluxes, fractional ice cover and ice thickness. Model results show significant variations in the bay circulation due to a pronounced seasonality in the wind forcing and the ice cover. The circulation is weakest in early summer when wind speeds are low and the ice still covers most parts of the bay. In autumn, circulation and flushing of the bay is most enhanced, due to increasing wind speeds and the absence of an ice cover. Dispersion scenarios were carried out assuming a leakage at dumped objects. During most of the year the obtained tracer concentrations in the bay are higher in the upper layers than close to the bottom, indicating an outflow at the surface and a compensatory inflow below. This general pattern is only reversed during spring and early summer, when the wind directions change. Since ice problems make it almost impossible to monitor surface waters or even the whole water column in a shallow bay, the only way to install a monitoring system, is at the bottom of the bay, as close as possible to dumped objects. Data transmission via satellite or radio could be realized from a small station located on the bay's edge.

  13. Computation and empirical modeling of UV flux reaching Arabian Sea due to O3 hole

    International Nuclear Information System (INIS)

    Yousufzai, M. Ayub Khan

    2008-01-01

    Scientific organizations the world over, such as the European Space Agency, the North Atlantic Treaty Organization, the National Aeronautics and Space Administration, and the United Nations Organization, are deeply concerned about the imbalances, caused to a significant extent due to human interference in the natural make-up of the earth's ecosystem. In particular, ozone layer depletion (OLD) over the South Pole is already a serious hazard. The long-term effect of ozone layer depletion appears to be an increase in the ultraviolet radiation reaching the earth. In order to understand the effects of ozone layer depletion, investigations have been initiated by various research groups. However, to the best of our knowledge, there does not seem to be available any work treating the problem of computing and constructing an empirical model for the UV flux reaching the Arabian Sea surface due to the O3 hole. The communication presents the results of quantifying UV flux and modeling future estimation using time series analysis in a local context to understand the nature of the depletion. (author)

  14. Convection links biomass burning to increased tropical ozone: However, models will tend to overpredict O3

    Science.gov (United States)

    Chatfield, Robert B.; Delany, Anthony C.

    1990-10-01

    Biomass burning throughout the inhabited portions of the tropics generates precursors which lead to significant local atmospheric ozone pollution. Several simulations show how this smog could be only an easily observed, local manifestation of a much broader increase in tropospheric ozone. We illustrate basic processes with a one-dimensional time-dependent model that is closer to true meteorological motions than commonly used eddy diffusion models. Its application to a representative region of South America gives reasonable simulations of the local pollutants measured there. Three illustrative simulations indicate the importance of dilution, principally due to vertical transport, in increasing the efficiency of ozone production, possibly enough for high ozone to be apparent on a very large, intercontinental scale. In the first, cook-then-mix, simulation the nitrogen oxides and other burning-produced pollutants are confined to a persistently subsident fair weather boundary layer for several days, and the resultant ozone is found to have only a transient influence on the whole column of tropospheric ozone. In the second, mix-then-cook, simulation the effect of typical cumulonimbus convection, which vents an actively polluted boundary layer, is to make a persistent increase in the tropical ozone column. Such a broadly increased ozone column is observed over the the populated "continental" portion of the tropics. A third simulation averages all emission, transport, and deposition parameters, representing one column in a global tropospheric model that does not simulate individual weather events. This "oversmoothing" simulation produces 60% more ozone than observed or otherwise modeled. Qualitatively similar overprediction is suggested for all models which average significantly in time or space, as all need do. Clearly, simulating these O3 levels will depend sensitively on knowledge of the timing of emissions and transport.

  15. Modeling defects and plasticity in MgSiO3 post-perovskite: Part 1-generalized stacking faults.

    Science.gov (United States)

    Goryaeva, Alexandra M; Carrez, Philippe; Cordier, Patrick

    In this work, we examine the transferability of a pairwise potential model (derived for MgSiO 3 perovskite) to accurately compute the excess energies of the generalized stacking faults (GSF, also called γ -surfaces) in MgSiO 3 post-perovskite. All calculations have been performed at 120 GPa, a pressure relevant to the D″ layer. Taking into account an important aspect of crystal chemistry for complex materials, we consider in detail all possible locations of slip planes in the post-perovskite structure. The γ -surface calculations emphasize the easiness of glide of slip systems with the smallest shear vector [100] and of the [001](010) slip system. Our results are in agreement with previous ab initio calculations. This validates the use the chosen potential model for further full atomistic modeling of dislocations in MgSiO 3 post-perovskite.

  16. Modeling investigation of the nutrient and phytoplankton variability in the Chesapeake Bay outflow plume

    Science.gov (United States)

    Jiang, Long; Xia, Meng

    2018-03-01

    The Chesapeake Bay outflow plume (CBOP) is the mixing zone between Chesapeake Bay and less eutrophic continental shelf waters. Variations in phytoplankton distribution in the CBOP are critical to the fish nursery habitat quality and ecosystem health; thus, an existing hydrodynamic-biogeochemical model for the bay and the adjacent coastal ocean was applied to understand the nutrient and phytoplankton variability in the plume and the dominant environmental drivers. The simulated nutrient and chlorophyll a distribution agreed well with field data and real-time satellite imagery. Based on the model calculation, the net dissolved inorganic nitrogen (DIN) and phosphorus (DIP) flux at the bay mouth was seaward and landward during 2003-2012, respectively. The CBOP was mostly nitrogen-limited because of the relatively low estuarine DIN export. The highest simulated phytoplankton biomass generally occurred in spring in the near field of the plume. Streamflow variations could regulate the estuarine residence time, and thus modulate nutrient export and phytoplankton biomass in the plume area; in comparison, changing nutrient loading with fixed streamflow had a less extensive impact, especially in the offshore and far-field regions. Correlation analyses and numerical experiments revealed that southerly winds on the shelf were effective in promoting the offshore plume expansion and phytoplankton accumulation. Climate change including precipitation and wind pattern shifts is likely to complicate the driving mechanisms of phytoplankton variability in the plume region.

  17. Steam reforming of different biomass tar model compounds over Ni/Al_2O_3 catalysts

    International Nuclear Information System (INIS)

    Artetxe, Maite; Alvarez, Jon; Nahil, Mohamad A.; Olazar, Martin; Williams, Paul T.

    2017-01-01

    Highlights: • Order of reactivity: anisole > furfural > indene > phenol > toluene > methyl naphthalene. • Higher coke deposition for oxygenates (1.5–2.8%) than for aromatics (0.5–0.8%). • Amorphous coke is deposited for oxygenates and filamentous carbon for aromatics. • Ni content of 20 wt.% shows the higher conversion (90%) and H_2 potential (63%). - Abstract: This work focuses on the removal of the tar derived from biomass gasification by catalytic steam reforming on Ni/Al_2O_3 catalysts. Different tar model compounds (phenol, toluene, methyl naphthalene, indene, anisole and furfural) were individually steam reformed (after dissolving each one in methanol), as well as a mixture of all of them, at 700 °C under a steam/carbon (S/C) ratio of 3 and 60 min on stream. The highest conversions and H_2 potential were attained for anisole and furfural, while methyl naphthalene presented the lowest reactivity. Nevertheless, the higher reactivity of oxygenates compared to aromatic hydrocarbons promoted carbon deposition on the catalyst (in the 1.5–2.8 wt.% range). When the concentration of methanol is decreased in the feedstock and that of toluene or anisole is increased, the selectivity to CO is favoured in the gaseous products, thus increasing coke deposition on the catalyst and decreasing catalyst activity for the steam reforming reaction. Moreover, an increase in Ni loading in the catalyst from 5 to 20% enhances carbon conversion and H_2 formation in the steam reforming of a mixture of all the model compounds studied, but these values decrease for a Ni content of 40%. Coke formation also increased by increasing Ni loading, attaining its maximum value for 40% Ni (6.5 wt.%).

  18. On the outflow of dense water from the Weddell and Ross Seas in OCCAM model

    Directory of Open Access Journals (Sweden)

    R. Kerr

    2012-06-01

    Full Text Available We describe the seasonal and interannual variability of volume transports in the Weddell and Ross Seas using the 1/12° 20-yr simulation of the OCCAM global ocean general circulation model. The average simulated full-depth cumulative volume transports were 28.5 ± 2.9 Sv (1 Sv ≡ 106 m3 s−1 and 13.4 ± 5.2 Sv, across the main export regions of the Weddell and Ross Seas, respectively. The values of mean outflow of Antarctic Bottom Water (AABW (defined by neutral density γn ≥ 28.27 kg m−3 from the Weddell and Ross Seas of 10.6 ± 3.1 Sv and 0.5 ± 0.7 Sv, respectively, agree with the range reported in historical observational studies. The export of Weddell Sea dense water in OCCAM is primarily determined by the strength of the Weddell Gyre. Variability in AABW export is predominantly at periods of ~1 yr and 2–4 yr.

  19. A DETAILED SPATIOKINEMATIC MODEL OF THE CONICAL OUTFLOW OF THE MULTIPOLAR PLANETARY NEBULA NGC 7026

    International Nuclear Information System (INIS)

    Clark, D. M.; López, J. A.; Steffen, W.; Richer, M. G.

    2013-01-01

    We present extensive, long-slit, high-resolution coverage of the complex planetary nebula (PN) NGC 7026. We acquired 10 spectra using the Manchester Echelle Spectrometer at San Pedro Martir Observatory in Baja California, Mexico, and each shows exquisite detail, revealing the intricate structure of this object. Incorporating these spectra into the three-dimensional visualization and kinematic program SHAPE and using Hubble Space Telescope images of NGC 7026, we have produced a detailed structural and kinematic model of this PN. NGC 7026 exhibits remarkable symmetry consisting of three lobe pairs and four sets of knots, all symmetrical about the nucleus and displaying a conical outflow. Comparing the three-dimensional structure of this nebula to recent XMM-Newton X-ray observations, we investigate the extended X-ray emission in relation to the nebular structure. We find that the X-ray emission, while confined to the closed, northern lobes of this PN, shows an abrupt termination in the middle of the southeast lobe, which our long slit data show to be open. This is where the shocked fast wind seems to be escaping the interior of the nebula and the X-ray emission rapidly cools in this region.

  20. Modeling of extreme freshwater outflow from the north-eastern Japanese river basins to western Pacific Ocean

    Science.gov (United States)

    Troselj, Josko; Sayama, Takahiro; Varlamov, Sergey M.; Sasaki, Toshiharu; Racault, Marie-Fanny; Takara, Kaoru; Miyazawa, Yasumasa; Kuroki, Ryusuke; Yamagata, Toshio; Yamashiki, Yosuke

    2017-12-01

    This study demonstrates the importance of accurate extreme discharge input in hydrological and oceanographic combined modeling by introducing two extreme typhoon events. We investigated the effects of extreme freshwater outflow events from river mouths on sea surface salinity distribution (SSS) in the coastal zone of the north-eastern Japan. Previous studies have used observed discharge at the river mouth, as well as seasonally averaged inter-annual, annual, monthly or daily simulated data. Here, we reproduced the hourly peak discharge during two typhoon events for a targeted set of nine rivers and compared their impact on SSS in the coastal zone based on observed, climatological and simulated freshwater outflows in conjunction with verification of the results using satellite remote-sensing data. We created a set of hourly simulated freshwater outflow data from nine first-class Japanese river basins flowing to the western Pacific Ocean for the two targeted typhoon events (Chataan and Roke) and used it with the integrated hydrological (CDRMV3.1.1) and oceanographic (JCOPE-T) model, to compare the case using climatological mean monthly discharges as freshwater input from rivers with the case using our hydrological model simulated discharges. By using the CDRMV model optimized with the SCE-UA method, we successfully reproduced hindcasts for peak discharges of extreme typhoon events at the river mouths and could consider multiple river basin locations. Modeled SSS results were verified by comparison with Chlorophyll-a distribution, observed by satellite remote sensing. The projection of SSS in the coastal zone became more realistic than without including extreme freshwater outflow. These results suggest that our hydrological models with optimized model parameters calibrated to the Typhoon Roke and Chataan cases can be successfully used to predict runoff values from other extreme precipitation events with similar physical characteristics. Proper simulation of extreme

  1. Analysis of the main dosimetric peak of Al2O3:C compounds with a model of interacting traps

    International Nuclear Information System (INIS)

    Ortega, F.; Marcazzó, J.; Molina, P.; Santiago, M.; Lester, M.; Henniger, J.; Caselli, E.

    2013-01-01

    The glow curve of Al 2 O 3 :C compounds has been analyzed by employing a model consisting of two active traps, thermally disconnected traps and one recombination centre. The analysis takes into account interaction among traps and the thermal quenching of the thermoluminescent emission. - Highlights: • Glow curves of Al 2 O 3 :C for two doses have been analysed taking into account interactions among traps. • The system of differential equations describing the kinetics has been uncoupled. • The new system of equations takes into account equations without derivatives. • The algorithm used will not become stiff. • The kinetics parameters obtained do not depend on the dose

  2. A Reliability Model for Ni-BaTiO3-Based (BME) Ceramic Capacitors

    Science.gov (United States)

    Liu, Donhang

    2014-01-01

    two identified failure modes follow different acceleration functions. Catastrophic failures follow the traditional power-law relationship to the applied voltage. Slow degradation failures fit well to an exponential law relationship to the applied electrical field. Finally, the impact of capacitor structure on the reliability of BME capacitors is discussed with respect to the number of dielectric layers in an MLCC unit, the number of BaTiO3 grains per dielectric layer, and the chip size of the capacitor device.

  3. Voigt modelling of size–strain analysis: Application to α-Al2O3 ...

    Indian Academy of Sciences (India)

    Unknown

    urea mixture, annealed samples and commercial α-Al2O3 sample. It is likely from the ... used for line broadening studies, the Stokes deconvolu- tion (Stokes 1948) ... unbiased approach to obtain the 'true specimen broad- ened' profile ... Experimental ... the Warren–Averbach method, simplified integral breadth method and ...

  4. Theoretical model to the Raman spectrum of B2O3

    International Nuclear Information System (INIS)

    Barrio, R.A.

    1984-01-01

    In this paper we report a new theory that reproduces qualitatively well the Raman spectrum of v-B 2 O 3 . The basic idea is that one can find the thermodinamically averaged Green's function for a Bethe lattice, with a Born Hamiltonian, with dihedral angles totally random. In extension one constructs a Bethe lattice of rings and solve the equations of motion for Green's functions at the Boron sites, bridging oxygens and oxygens in the rings. (M.W.O.) [pt

  5. CLC in packed beds using syngas and CuO/Al2O3: Model description and experimental validation

    International Nuclear Information System (INIS)

    Hamers, H.P.; Gallucci, F.; Cobden, P.D.; Kimball, E.; Sint Annaland, M. van

    2014-01-01

    Highlights: • CLC with CuO/Al 2 O 3 and syngas and air has been demonstrated experimentally. • Model predicts accurately only if kinetics describe the complete solid reduction. • CuO/Al 2 O 3 is proven to catalyze the reversed water gas shift reaction. • H 2 O is more effective to suppress carbon deposition on CuO/Al 2 O 3 than CO 2 . • The OC reaction rate is not permanently affected by exposure to H 2 S. - Abstract: The objective of this work is to study the performance of the oxygen carrier in a packed bed with periodic switching between oxidizing and reducing conditions. In this paper the performance of CuO/Al 2 O 3 as the oxygen carrier in a packed bed reactor with syngas as the fuel are investigated, while also studying the (possible) carbon deposition and the effect of sulphur impurities on the stability of the carrier. Both experiments and simulations are used in this work. Cyclic experiments (oxidation with air and reduction with syngas) have been carried out in a lab scale packed bed reactor with 13 wt% CuO/Al 2 O 3 . The experimental results were well described by a 1D reactor model, provided that critical attention was given to the reaction rate for the complete reduction reaction, including a dramatic decrease in reaction rate at high solid conversions. Feeding syngas (p H2 = p CO = 0.1 bar) resulted in 1.1% carbon deposition of the feed. Steam was proven to be more effective in reducing carbon deposition than CO 2 . Moreover, it has been found that CuO/Al 2 O 3 catalyzed the water gas shift reaction and the reaction rate was not permanently affected by exposure to H 2 S, two key factors for CLC operation. The results of this work imply that CuO/Al 2 O 3 is an effective oxygen carrier as the first packed bed reactor in a TSCLC process and that the developed model is able to describe the performance at larger scales accurately

  6. The field fluctuational model of thermally stimulated processes in ferroelectric LiNbO3

    International Nuclear Information System (INIS)

    Tale, I.; Tale, V.; Rosa, J.

    1983-01-01

    The thermally stimulated processes in the x-irradiated LiNbO 3 crystals were studied by the fractional glow technique. The trap ionization with unusually high values of the mean activation energy and the effective frequency factor as well as decreasing the activation energy of the traps when the temperature increased from 150-180 K were observed. It is suggested that all these effects are due to the ion-fluctuation process (the electric field generated by thermal reorientation of dipoles). (author)

  7. Microstructural characterization of Y2O3 ODS-Fe-Cr model alloys

    International Nuclear Information System (INIS)

    Castro, V. de; Leguey, T.; Munoz, A.; Monge, M.A.; Pareja, R.; Marquis, E.A.; Lozano-Perez, S.; Jenkins, M.L.

    2009-01-01

    Two Fe-12 wt% Cr alloys, one containing 0.4 wt% Y 2 O 3 and the other Y 2 O 3 -free, have been produced by mechanical alloying followed by hot isostatic pressing. These oxide dispersion strengthened and reference alloys were characterized both in the as-HIPed state and after tempering by transmission electron microscopy and atom-probe tomography. The as-HIPed alloys exhibited the characteristic microstructure of lath martensite and contained a high density of dislocations. Small voids with sizes 3 C and M 23 C 6 carbides (M = Cr, Fe) probably as a result of C ingress during milling. After tempering at 1023 K for 4 h the microstructures had partially recovered. In the recovered regions, martensite laths were replaced by equiaxed grains in which M 23 C 6 carbides decorated the grain boundaries. In the ODS alloy nanoparticles containing Y were commonly observed within grains, although they were also present at grain boundaries and adjacent to large carbides.

  8. Estimation of the magnetic entropy change by means of Landau theory and phenomenological model in La0.6Ca0.2 Sr0.2MnO3/Sb2O3 ceramic composites

    Science.gov (United States)

    Nasri, M.; Dhahri, E.; Hlil, E. K.

    2018-06-01

    In this paper, magnetocaloric properties of La0.6Ca0.2Sr0.2MnO3/Sb2O3 oxides have been investigated. The composite samples were prepared using the conventional solid-state reaction method. The second-order phase transition can be testified with the positive slope in Arrott plots. An excellent agreement has been found between the -ΔSM values estimated by Landau theory and those obtained using the classical Maxwell relation. The field dependence of the magnetic entropy change analysis shows a power law dependence,|ΔSM|≈Hn , with n(TC) = 0.65. Moreover, the scaling analysis of magnetic entropy change exhibits that ΔSM(T) curves collapse into a single universal curve, indicating that the observed paramagnetic to ferromagnetic phase transition is an authentic second-order phase transition. The maximum value of magnetic entropy change of composites is found to decrease slightly with the further increasing of Sb2O3 concentration. A phenomenological model was used to predict magnetocaloric properties of La0.6Ca0.2Sr0.2MnO3/Sb2O3 composites. The theoretical calculations are compared with the available experimental data.

  9. Use of Combined Observational- and Model-Derived Photochemical Indicators to Assess the O3-NOx-VOC System Sensitivity in Urban Areas

    Directory of Open Access Journals (Sweden)

    Edson R. Carrillo-Torres

    2017-01-01

    Full Text Available Tropospheric levels of O3 have historically exceeded the official annual Mexican standards within the Monterrey Metropolitan Area (MMA in NE Mexico. High-frequency and high-precision measurements of tropospheric O3, NOy, NO2, NO, CO, SO2, PM10 and PM2.5 were made at the Obispado monitoring site near the downtown MMA from September 2012 to August 2013. The seasonal cycles of O3 and NOy are driven by changes in meteorology and to a lesser extent by variations in primary emissions. The NOy levels were positively correlated with O3 precursors and inversely correlated with O3 and wind speed. Recorded data were used to assess the O3-Volatile Organic Compounds (VOC-NOx system’s sensitivity through an observational-based approach. The photochemical indicator O3/NOy was derived from measured data during the enhanced O3 production period (12:00–18:00 Central Daylight Time (CDT, GMT-0500. The O3/NOy ratios calculated for this time period showed that the O3 production within the MMA is VOC sensitive. A box model simulation of production rates of HNO3 (PHNO3 and total peroxides (Pperox carried out for O3 episodes in fall and spring confirmed the VOC sensitivity within the MMA environment. No significant differences were observed in O3/NOy from weekdays to weekends or for PHNO3/Pperox ratios, confirming the limiting role of VOCs in O3 production within the MMA. The ratified photochemical regime observed may allow the environmental authorities to revise and verify the current policies for air quality control within the MMA.

  10. Relativistic Outflows from ADAFs

    Science.gov (United States)

    Becker, Peter; Subramanian, Prasad; Kazanas, Demosthenes

    2001-04-01

    Advection-dominated accretion flows (ADAFs) have a positive Bernoulli parameter, and are therefore gravitationally bound. The Newtonian ADAF model has been generalized recently to obtain the ADIOS model that includes outflows of energy and angular momentum, thereby allowing accretion to proceed self-consistently. However, the utilization of a Newtonian gravitational potential limits the ability of this model to describe the inner region of the disk, where any relativistic outflows are likely to originate. In this paper we modify the ADIOS scenario to incorporate a seudo - Newtonian potential, which approximates the effects of general relativity. The analysis yields a unique, self - similar solution for the structure of the coupled disk/wind system. Interesting features of the new solution include the relativistic character of the outflow in the vicinity of the radius of marginal stability, which represents the inner edge of the quasi-Keplerian disk in our model. Our self - similar model may therefore help to explain the origin of relativistic jets in active galaxies. At large distances the radial dependence of the accretion rate approachs the unique form dot M ∝ r^1/2, with an associated density variation given by ρ ∝ r-1. This density variation agrees with that implied by the dependence of the X-ray hard time lags on the Fourier frequency for a number of accreting galactic black hole candidates. While intriguing, the results of our self-similar model need to be confirmed in the future by incorporating a detailed physical description of the energization mechanism that drives the outflow, which is likely to be powered by the shear of the underlying accretion disk.

  11. SDSS-IV MaNGA: modelling the metallicity gradients of gas and stars - radially dependent metal outflow versus IMF

    Science.gov (United States)

    Lian, Jianhui; Thomas, Daniel; Maraston, Claudia; Goddard, Daniel; Parikh, Taniya; Fernández-Trincado, J. G.; Roman-Lopes, Alexandre; Rong, Yu; Tang, Baitian; Yan, Renbin

    2018-05-01

    In our previous work, we found that only two scenarios are capable of reproducing the observed integrated mass-metallicity relations for the gas and stellar components of local star-forming galaxies simultaneously. One scenario invokes a time-dependent metal outflow loading factor with stronger outflows at early times. The other scenario uses a time-dependent initial mass function (IMF) slope with a steeper IMF at early times. In this work, we extend our study to investigate the radial profile of gas and stellar metallicity in local star-forming galaxies using spatially resolved spectroscopic data from the SDSS-IV MaNGA survey. We find that most galaxies show negative gradients in both gas and stellar metallicity with steeper gradients in stellar metallicity. The stellar metallicity gradients tend to be mass dependent with steeper gradients in more massive galaxies while no clear mass dependence is found for the gas metallicity gradient. Then we compare the observations with the predictions from a chemical evolution model of the radial profiles of gas and stellar metallicities. We confirm that the two scenarios proposed in our previous work are also required to explain the metallicity gradients. Based on these two scenarios, we successfully reproduce the radial profiles of gas metallicity, stellar metallicity, stellar mass surface density, and star formation rate surface density simultaneously. The origin of the negative gradient in stellar metallicity turns out to be driven by either radially dependent metal outflow or IMF slope. In contrast, the radial dependence of the gas metallicity is less constrained because of the degeneracy in model parameters.

  12. Failed Radiatively Accelerated Dusty Outflow Model of the Broad Line Region in Active Galactic Nuclei. I. Analytical Solution

    Energy Technology Data Exchange (ETDEWEB)

    Czerny, B.; Panda, S.; Wildy, C.; Sniegowska, M. [Center for Theoretical Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Li, Yan-Rong; Wang, J.-M. [Key Laboratory for Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing 100049 (China); Hryniewicz, K.; Sredzinska, J. [Copernicus Astronomical Center, Polish Academy of Sciences, Bartycka 18, 00-716 Warsaw (Poland); Karas, V., E-mail: bcz@cft.edu.pl [Astronomical Institute, Academy of Sciences, Bocni II 1401, CZ-141 00 Prague (Czech Republic)

    2017-09-10

    The physical origin of the broad line region in active galactic nuclei is still unclear despite many years of observational studies. The reason is that the region is unresolved, and the reverberation mapping results imply a complex velocity field. We adopt a theory-motivated approach to identify the principal mechanism responsible for this complex phenomenon. We consider the possibility that the role of dust is essential. We assume that the local radiation pressure acting on the dust in the accretion disk atmosphere launches the outflow of material, but higher above the disk the irradiation from the central parts causes dust evaporation and a subsequent fallback. This failed radiatively accelerated dusty outflow is expected to represent the material forming low ionization lines. In this paper we formulate simple analytical equations to describe the cloud motion, including the evaporation phase. The model is fully described just by the basic parameters of black hole mass, accretion rate, black hole spin, and viewing angle. We study how the spectral line generic profiles correspond to this dynamic. We show that the virial factor calculated from our model strongly depends on the black hole mass in the case of enhanced dust opacity, and thus it then correlates with the line width. This could explain why the virial factor measured in galaxies with pseudobulges differs from that obtained from objects with classical bulges, although the trend predicted by the current version of the model is opposite to the observed trend.

  13. Deconfined quantum criticality of the O(3) nonlinear σ model in two spatial dimensions: A renormalization-group study

    International Nuclear Information System (INIS)

    Kim, Ki-Seok

    2005-01-01

    We investigate the quantum phase transition of the O(3) nonlinear σ model without Berry phase in two spatial dimensions. Utilizing the CP 1 representation of the nonlinear σ model, we obtain an effective action in terms of bosonic spinons interacting via compact U(1) gauge fields. Based on the effective field theory, we find that the bosonic spinons are deconfined to emerge at the quantum critical point of the nonlinear σ model. It is emphasized that the deconfinement of spinons is realized in the absence of Berry phase. This is in contrast to the previous study of Senthil et al. [Science 303, 1490 (2004)], where the Berry phase plays a crucial role, resulting in the deconfinement of spinons. It is the reason why the deconfinement is obtained even in the absence of the Berry phase effect that the quantum critical point is described by the XY ('neutral') fixed point, not the IXY ('charged') fixed point. The IXY fixed point is shown to be unstable against instanton excitations and the instanton excitations are proliferated. At the IXY fixed point it is the Berry phase effect that suppresses the instanton excitations, causing the deconfinement of spinons. On the other hand, the XY fixed point is found to be stable against instanton excitations because an effective internal charge is zero at the neutral XY fixed point. As a result the deconfinement of spinons occurs at the quantum critical point of the O(3) nonlinear σ model in two dimensions

  14. Magnetic anisotropy in the Kitaev model systems Na2IrO3 and RuCl3

    Science.gov (United States)

    Chaloupka, Jiří; Khaliullin, Giniyat

    2016-08-01

    We study the ordered moment direction in the extended Kitaev-Heisenberg model relevant to honeycomb lattice magnets with strong spin-orbit coupling. We utilize numerical diagonalization and analyze the exact cluster ground states using a particular set of spin-coherent states, obtaining thereby quantum corrections to the magnetic anisotropy beyond conventional perturbative methods. It is found that the quantum fluctuations strongly modify the moment direction obtained at a classical level and are thus crucial for a precise quantification of the interactions. The results show that the moment direction is a sensitive probe of the model parameters in real materials. Focusing on the experimentally relevant zigzag phases of the model, we analyze the currently available neutron-diffraction and resonant x-ray-diffraction data on Na2IrO3 and RuCl3 and discuss the parameter regimes plausible in these Kitaev-Heisenberg model systems.

  15. Massive Outflows Associated with ATLASGAL Clumps

    Science.gov (United States)

    Yang, A. Y.; Thompson, M. A.; Urquhart, J. S.; Tian, W. W.

    2018-03-01

    We have undertaken the largest survey for outflows within the Galactic plane using simultaneously observed {}13{CO} and {{{C}}}18{{O}} data. Out of a total of 919 ATLASGAL clumps, 325 have data suitable to identify outflows, and 225 (69% ± 3%) show high-velocity outflows. The clumps with detected outflows show significantly higher clump masses ({M}clump}), bolometric luminosities ({L}bol}), luminosity-to-mass ratios ({L}bol}/{M}clump}), and peak H2 column densities ({N}{{{H}}2}) compared to those without outflows. Outflow activity has been detected within the youngest quiescent clump (i.e., 70 μ {{m}} weak) in this sample, and we find that the outflow detection rate increases with {M}clump}, {L}bol}, {L}bol}/{M}clump}, and {N}{{{H}}2}, approaching 90% in some cases (UC H II regions = 93% ± 3%; masers = 86% ± 4%; HC H II regions = 100%). This high detection rate suggests that outflows are ubiquitous phenomena of massive star formation (MSF). The mean outflow mass entrainment rate implies a mean accretion rate of ∼ {10}-4 {M}ȯ {yr}}-1, in full agreement with the accretion rate predicted by theoretical models of MSF. Outflow properties are tightly correlated with {M}clump}, {L}bol}, and {L}bol}/{M}clump} and show the strongest relation with the bolometric clump luminosity. This suggests that outflows might be driven by the most massive and luminous source within the clump. The correlations are similar for both low-mass and high-mass outflows over 7 orders of magnitude, indicating that they may share a similar outflow mechanism. Outflow energy is comparable to the turbulent energy within the clump; however, we find no evidence that outflows increase the level of clump turbulence as the clumps evolve. This implies that the origin of turbulence within clumps is fixed before the onset of star formation.

  16. O3 and NOx Exchange

    NARCIS (Netherlands)

    Loubet, B.; Castell, J.F.; Laville, P.; Personne, E.; Tuzet, A.; Ammann, C.; Emberson, L.; Ganzeveld, L.; Kowalski, A.S.; Merbold, L.; Stella, P.; Tuovinen, J.P.

    2015-01-01

    This discussion was based on the background document “Review on modelling atmosphere-biosphere exchange of Ozone and Nitrogen oxides”, which reviews the processes contributing to biosphere-atmosphere exchange of O3 and NOx, including stomatal and non-stomatal exchange of O3 and NO, NO2.

  17. A changing climate: impacts on human exposures to O3 using an integrated modeling methodology

    Science.gov (United States)

    Predicting the impacts of changing climate on human exposure to air pollution requires future scenarios that account for changes in ambient pollutant concentrations, population sizes and distributions, and housing stocks. An integrated methodology to model changes in human exposu...

  18. GSTAR-SUR Modeling With Calendar Variations And Intervention To Forecast Outflow Of Currencies In Java Indonesia

    Science.gov (United States)

    Akbar, M. S.; Setiawan; Suhartono; Ruchjana, B. N.; Riyadi, M. A. A.

    2018-03-01

    Ordinary Least Squares (OLS) is general method to estimates Generalized Space Time Autoregressive (GSTAR) parameters. But in some cases, the residuals of GSTAR are correlated between location. If OLS is applied to this case, then the estimators are inefficient. Generalized Least Squares (GLS) is a method used in Seemingly Unrelated Regression (SUR) model. This method estimated parameters of some models with residuals between equations are correlated. Simulation study shows that GSTAR with GLS method for estimating parameters (GSTAR-SUR) is more efficient than GSTAR-OLS method. The purpose of this research is to apply GSTAR-SUR with calendar variation and intervention as exogenous variable (GSTARX-SUR) for forecast outflow of currency in Java, Indonesia. As a result, GSTARX-SUR provides better performance than GSTARX-OLS.

  19. A kinetic model of the hydrogen assisted selective catalytic reduction of NO with ammonia over Ag/Al2O3

    DEFF Research Database (Denmark)

    Tamm, Stefanie; Olsson, Louise; Fogel, Sebastian

    2013-01-01

    A global kinetic model which describes H2-assisted NH3-SCR over an Ag/Al2O3 monolith catalyst has been developed. The intention is that the model can be applied for dosing NH3 and H2 to an Ag/Al2O3 catalyst in a real automotive application as well as contribute to an increased understanding of th...

  20. Using plant biomonitors and flux modelling to develop O3 dose-response relationships in Catalonia

    International Nuclear Information System (INIS)

    Filella, Iolanda; Pen-tilde uelas, Josep; Ribas, Angela

    2005-01-01

    We used tobacco Bel-W3 biomonitoring data and ozone flux modelling (WINDEP model) with the aim of developing the absorbed dose-response relationship, and comparing this approach with the most commonly used AOT40 (the sum of hourly ozone concentrations above a cut-off of 40 ppb during daylight hours, when global radiation exceeds 50 W m -2 ) in the estimation of exposure-damage curves. Leaf damage values were more related to OAD 15days,potential (potential ozone absorbed dose calculated over 15 consecutive days) than to AOT40 in all the studied stations. An OAD 15days,potential of 180 mg m -2 was found to be the threshold for damage to the most sensitive species in this region under well watered conditions. The results show the applicability of the flux approach for risk assessment at the local scale, the improvement of the ozone damage estimation when the potential absorbed dose is modelled and used instead of just the ozone exposure, and finally, the possibilities opened by the use of biomonitoring networks. - Modelling of biomonitors ozone absorbed dose improves damage estimation in comparison with exposure indices such as AOT40

  1. Numerical study of different conduction models for Al_2O_3-water nanofluid with variable properties inside a trapezoidal enclosure

    International Nuclear Information System (INIS)

    Arani, Ali Akbar Abbasian; Azemati, Ali Akbar; Rezaee, Mohammad; Hadavand, Behzad Shirkavand

    2017-01-01

    Natural convection in enclosures containing nanofluids is important in physical and environmental applications. Different models for conduction have been developed because of the importance of this phenomenon in natural convection in enclosures. In this study, effects of conduction models of Chon, Corcione, Khanafer, and Koo and Kleinstreuer on the natural convection inside a trapezoidal enclosure with hot and cold walls are evaluated numerically. The enclosure contains Al_2O_3-water nanofluid with variable properties. Effects of the conduction models on fluid flow, natural convection, variations in volume fraction, and diameter of nanoparticles in the models, as well as the variations in the Rayleigh number, are examined. Results show that at Rayleigh numbers of 105 and 106, the maximum and minimum values of the average Nusselt number are obtained using the models of Khanafer and Chon, respectively. In all models, the average Nusselt number presents upward and downward trends when the volume fraction of nanoparticles increases but decreases when the di- ameter of the nanoparticles increases. At Ra = 105 in all models, as the volume fraction of nanoparticles increases, the nanofluid provides a higher average Nusselt number compared with the base fluid. By contrast, at Ra = 106, at volume fractions larger than 0.01 and using the model of Chon, the average Nusselt number of the nanofluid is lower compared with that of the base fluid.

  2. MECHANISTIC KINETIC MODELS FOR STEAM REFORMING OF CONCENTRATED CRUDE ETHANOL ON NI/AL2O3 CATALYST

    Directory of Open Access Journals (Sweden)

    O. A. OLAFADEHAN

    2015-05-01

    Full Text Available Mechanistic kinetic models were postulated for the catalytic steam reforming of concentrated crude ethanol on a Ni-based commercial catalyst at atmosphere pressure in the temperature range of 673-863 K, and at different catalyst weight to the crude ethanol molar flow rate ratio (in the range 0.9645-9.6451 kg catalyst h/kg mole crude ethanol in a stainless steel packed bed tubular microreactor. The models were based on Langmuir-Hinshelwood-Hougen-Watson (LHHW and Eley-Rideal (ER mechanisms. The optimization routine of Nelder-Mead simplex algorithm was used to estimate the inherent kinetic parameters in the proposed models. The selection of the best kinetic model amongst the rival kinetic models was based on physicochemical, statistical and thermodynamic scrutinies. The rate determining step for the steam reforming of concentrated crude ethanol on Ni/Al2O3 catalyst was found to be surface reaction between chemisorbed CH3O and O when hydrogen and oxygen were adsorbed as monomolecular species on the catalyst surface. Excellent agreement was obtained between the experimental rate of reaction and conversion of crude ethanol, and the simulated results, with ADD% being ±0.46.

  3. Modelling Eu(III) speciation in a Eu(III)/PAHA/α-Al2O3 ternary system

    International Nuclear Information System (INIS)

    Janot, Noemie; Reiller, Pascal E.; Benedetti, Marc F.

    2013-01-01

    In this work, modelling of Eu(III) speciation in a ternary system, i.e., in presence of purified Aldrich humic acid (PAHA) and α-Al 2 O 3 , is presented. First, the mineral surface charge is measured by potentiometric titrations and then described using the CD-MUSIC model. This model is also used to describe Eu(III) binding to the α-Al 2 O 3 surface at different pH values, ionic strength and mineral concentrations. Time resolved luminescence spectroscopy (TRLS) is then used to study the binding of Eu(III) to PAHA at pH 4 with different humic acid concentrations. The spectra are used to calculate a spectroscopic 'titration curve', used to determine Eu(III)/PAHA binding parameters in the NICA-Donnan model. Following a previous study (Janot et al., Water Res. 46, 731-740), modelling of the ternary system is based upon the definition of two PAHA pools where one fraction remains in solution and the other is adsorbed onto the mineral surface, with each possessing different proton and metal binding parameters. The modification of protonation behaviour for both fractions is examined using spectrophotometric titrations of the non adsorbed PAHA fraction at different organic/mineral ratios. These data are then used to describe Eu(III) interactions in the ternary system: Eu(III) re-partitioning in the ternary system is calculated for different pH, ionic strength and PAHA concentrations, and results are compared to experimental observations. The model is in good agreement with experimental data, except at high PAHA fractionation rates. Results show that organic complexation dominates over a large pH range, with the predominant species existing as the surface-bound fraction. Above pH 8, Eu(III) seems to be mostly complexed to the mineral surface, which is in agreement with previous spectroscopic observations (Janot et al., Environ. Sci. Technol. 45, 3224-3230). (authors)

  4. WOx supported on γ-Al2O3 with different morphologies as model catalysts for alkanol dehydration

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Dachuan; Wang, Huamin; Kovarik, Libor; Gao, Feng; Wan, Chuan; Hu, Jian Z.; Wang, Yong

    2018-04-21

    The distinctive morphological and surface characteristics of platelet-like γ-Al2O3 were compared to a regular, commercial γ-Al2O3. γ-Al2O3 platelets display dominant (110) surface facets and higher densities of coordinative unsaturated penta-coordinate Al3+ (Al3+penta) sites than regular γ-Al2O3, as measured by solid-state magic-angle spinning nuclear magnetic resonance spectroscopy (MAS NMR). Such Al3+penta sites are also the preferred surface anchoring sites for tungsten oxide (WOx) species consistent with NMR analysis indicating that these sites are consumed upon WOx adsorption. The higher Al3+penta density on γ-Al2O3 platelets leads to greater WOx dispersion (or smaller WOx clusters), as demonstrated by scanning transmission electron microscopy and ultraviolet–visible spectroscopy, and WOx species at intermediate WOx surface concentration are the most active for the probe reaction of 2-butanol dehydration. WOx on γ-Al2O3 platelets approaches the highest turnover rates at higher surface densities than WOx on regular γ-Al2O3, yet with similar highest rate values for both series of catalysts. This indicates that different Al2O3 supports mainly affect the dispersion of supported WOx rather than the intrinsic reactivity of individual WOx clusters with similar size.

  5. O3 Nanoparticles

    KAUST Repository

    Wang, Juan; Li, Yangyang; Deng, Lin; Wei, Nini; Weng, Yakui; Dong, Shuai; Qi, Dianpeng; Qiu, Jun; Chen, Xiaodong; Wu, Tao

    2016-01-01

    Ti2O3 nanoparticles with high performance of photothermal conversion are demonstrated for the first time. Benefiting from the nanosize and narrow-bandgap features, the Ti2O3 nanoparticles possess strong light absorption and nearly 100% internal

  6. A comparison study between observations and simulation results of Barghouthi model for O+ and H+ outflows in the polar wind

    Directory of Open Access Journals (Sweden)

    I. A. Barghouthi

    2011-11-01

    Full Text Available To advance our understanding of the effect of wave-particle interactions on ion outflows in the polar wind region and the resulting ion heating and escape from low altitudes to higher altitudes, we carried out a comparison between polar wind simulations obtained using Barghouthi model with corresponding observations obtained from different satellites. The Barghouthi model describes O+ and H+ outflows in the polar wind region in the range 1.7 RE to 13.7 RE, including the effects of gravity, polarization electrostatic field, diverging geomagnetic field lines, and wave-particle interactions. Wave-particle interactions were included into the model by using a particle diffusion equation, which depends on diffusion coefficients determined from estimates of the typical electric field spectral density at relevant altitudes and frequencies. We provide a formula for the velocity diffusion coefficient that depends on altitude and velocity, in which the velocity part depends on the perpendicular wavelength of the electromagnetic turbulence λ⊥. Because of the shortage of information about λ⊥, it was included into the model as a parameter. We produce different simulations (i.e. ion velocity distributions, ions density, ion drift velocity, ion parallel and perpendicular temperatures for O+ and H+ ions, and for different λ⊥. We discuss the simulations in terms of wave-particle interactions, perpendicular adiabatic cooling, parallel adiabatic cooling, mirror force, and ion potential energy. The main findings of the simulations are as follows: (1 O+ ions are highly energized at all altitudes in the simulation tube due to wave-particle interactions that heat the ions in the perpendicular direction, and part of this gained energy transfer to the parallel direction by mirror force, resulting in accelerating O+ ions along geomagnetic field lines from lower altitudes to higher altitudes. (2 The effect of wave-particle interactions is negligible for H

  7. CONTROLLING INFLUENCE OF MAGNETIC FIELD ON SOLAR WIND OUTFLOW: AN INVESTIGATION USING CURRENT SHEET SOURCE SURFACE MODEL

    Energy Technology Data Exchange (ETDEWEB)

    Poduval, B., E-mail: bpoduval@spacescience.org [Space Science Institute, Boulder, CO 80303 (United States)

    2016-08-10

    This Letter presents the results of an investigation into the controlling influence of large-scale magnetic field of the Sun in determining the solar wind outflow using two magnetostatic coronal models: current sheet source surface (CSSS) and potential field source surface. For this, we made use of the Wang and Sheeley inverse correlation between magnetic flux expansion rate (FTE) and observed solar wind speed (SWS) at 1 au. During the period of study, extended over solar cycle 23 and beginning of solar cycle 24, we found that the coefficients of the fitted quadratic equation representing the FTE–SWS inverse relation exhibited significant temporal variation, implying the changing pattern of the influence of FTE on SWS over time. A particularly noteworthy feature is an anomaly in the behavior of the fitted coefficients during the extended minimum, 2008–2010 (CRs 2073–2092), which is considered due to the particularly complex nature of the solar magnetic field during this period. However, this variation was significant only for the CSSS model, though not a systematic dependence on the phase of the solar cycle. Further, we noticed that the CSSS model demonstrated better solar wind prediction during the period of study, which we attribute to the treatment of volume and sheet currents throughout the corona and the more accurate tracing of footpoint locations resulting from the geometry of the model.

  8. Hemodialysis Reliable Outflow (HeRO) device in end-stage dialysis access: a decision analysis model.

    Science.gov (United States)

    Dageforde, Leigh Anne; Bream, Peter R; Moore, Derek E

    2012-09-01

    The Hemodialysis Reliable Outflow (HeRO) dialysis access device is a permanent tunneled dialysis graft connected to a central venous catheter and is used in patients with end-stage dialysis access (ESDA) issues secondary to central venous stenosis. The safety and effectiveness of the HeRO device has previously been proven, but no study thus far has compared the cost of its use with tunneled dialysis catheters (TDCs) and thigh grafts in patients with ESDA. A decision analytic model was developed to simulate outcomes for patients with ESDA undergoing placement of a HeRO dialysis access device, TDC, or thigh graft. Outcomes of interest were infection, thrombosis, and ischemic events. Baseline values, ranges, and costs were determined from a systematic review of the literature. Total costs were based on 1 year of post-procedure outcomes. Sensitivity analyses were conducted to test model strength. The HeRO dialysis access device is the least costly dialysis access with an average 1-year cost of $6521. The 1-year cost for a TDC was $8477. A thigh graft accounted for $9567 in a 1-year time period. The HeRO dialysis access device is the least costly method of ESDA. The primary determinants of cost in this model are infection in TDCs and leg ischemia necessitating amputation in thigh grafts. Further study is necessary to incorporate patient preference and quality of life into the model. Copyright © 2012 Elsevier Inc. All rights reserved.

  9. O3 Nanoparticles

    KAUST Repository

    Wang, Juan

    2016-11-16

    Ti2O3 nanoparticles with high performance of photothermal conversion are demonstrated for the first time. Benefiting from the nanosize and narrow-bandgap features, the Ti2O3 nanoparticles possess strong light absorption and nearly 100% internal solar–thermal conversion efficiency. Furthermore, Ti2O3 nanoparticle-based thin film shows potential use in seawater desalination and purification.

  10. Enhanced Conductivity at the Interface of Li2O ratio B2O3 Nanocomposites: Atomistic Models

    International Nuclear Information System (INIS)

    Islam, Mazharul M.; Bredow, Thomas; Indris, Sylvio; Heitjans, Paul

    2007-01-01

    A theoretical investigation at density-functional level of Li ion conduction at the interfaces in Li 2 O ratio B 2 O 3 nanocomposites is presented. The structural disorder at the Li 2 O(111) ratio B 2 O 3 (001) interface leads to reduced defect formation energies for Li vacancies and Frenkel defects compared to Li 2 O surfaces. The average activation energy for Li + diffusion in the interface region is in the range of the values for Li 2 O. It is therefore concluded that the enhanced Li conductivity of Li 2 O ratio B 2 O 3 nanocomposites is mainly due to the increased defect concentration

  11. Mathematical and physical model of gravity-fed infusion outflow: application to soft-bag-packed solutions.

    Science.gov (United States)

    Simon, N; Décaudin, B; Lannoy, D; Barthélémy, C; Lemdani, M; Odou, P

    2011-12-01

    Gravity-fed infusion (GFI) systems are acknowledged as being unable to keep their flow-rate constant. This may affect drug plasma levels such as aminoglycosides. Numerous factors have previously been cited, but their relative importance has never been quantified so far. The objective of this work is to identify the main factors that influence GFI in vitro outflow and to propose a mathematical model of flow-rate evolution as a function of time. In this model, pressure loss and infusion device creep have been considered as the main variation factors. Concomitantly, two experiments were undertaken. Firstly, the flow-rate evolution of an in vitro infusion of 250 mL of dextrose 5% was assessed. Secondly, the creep occurring on an infusion device was measured through a stress relaxation experiment. The experimental infusion flow-rate decreased by as much as 28.5% over 1 h. Simulated and experimental data are well correlated (r = 0.987; P model should help to explain the differences observed in drug plasma levels with gravity-fed devices.

  12. Surface modeling and chemical solution deposition of SrO(SrTiO3)n Ruddlesden-Popper phases

    International Nuclear Information System (INIS)

    Zschornak, M.; Gemming, S.; Gutmann, E.; Weissbach, T.; Stoecker, H.; Leisegang, T.; Riedl, T.; Traenkner, M.; Gemming, T.; Meyer, D.C.

    2010-01-01

    Strontium titanate (STO) is a preferred substrate material for functional oxide growth, whose surface properties can be adjusted through the presence of Ruddlesden-Popper (RP) phases. Here, density functional theory (DFT) is used to model the (1 0 0) and (0 0 1) surfaces of SrO(SrTiO 3 ) n RP phases. Relaxed surface structures, electronic properties and stability relations have been determined. In contrast to pure STO, the near-surface SrO-OSr stacking fault can be employed to control surface roughness by adjusting SrO and TiO 2 surface rumpling, to stabilize SrO termination in an SrO-rich surrounding or to increase the band gap in the case of TiO 2 termination. RP thin films have been epitaxially grown on (0 0 1) STO substrates by chemical solution deposition. In agreement with DFT results, the fraction of particular RP phases n = 1-3 changes with varying heating rate and molar ratio Sr:Ti. This is discussed in terms of bulk formation energy.

  13. Acetylene and carbon monoxide oxidation over a Pt/Rh/CeO2/γ-Al2O3 automotive exhaust gas catalyst: kinetic modelling of transient experiments

    NARCIS (Netherlands)

    Harmsen, J.M.A.; Hoebink, J.H.B.J.; Schouten, J.C.

    2001-01-01

    The transient kinetics of acetylene (C2H2) conversion by oxygen over a commercial Pt/Rh/CeO2/¿-Al2O3 three-way catalyst have been modelled. Experiments to validate the model were carried out in a fixed-bed reactor with two separate inlets, enabling alternate feeding of acetylene and oxygen.

  14. Outflow dynamics in modeling oligopoly markets: the case of the mobile telecommunications market in Poland

    Science.gov (United States)

    Sznajd-Weron, Katarzyna; Weron, Rafał; Włoszczowska, Maja

    2008-11-01

    In this paper we introduce two models of opinion dynamics in oligopoly markets and apply them to a situation where a new entrant challenges two incumbents of the same size. The models differ in the way in which the two forces influencing consumer choice—(local) social interactions and (global) advertising—interact. We study the general behavior of the models using the mean field approach and Monte Carlo simulations and calibrate the models using data from the Polish telecommunications market. For one of the models criticality is observed—below a certain critical level of advertising the market approaches a lock-in situation, where one market leader dominates the market and all other brands disappear. Interestingly, for both models the best fits to real data are obtained for conformity level p \\in (0.3,0.4) . This agrees very well with the conformity level found by Solomon Asch in his famous social experiment.

  15. An Outflow Boundary Condition Model for Noninvasive Prediction of Fractional Flow Reserve in Diseased Coronary Arteries.

    Science.gov (United States)

    Fayssal, Iyad A; Moukalled, Fadl; Alam, Samir; Isma'eel, Hussain

    2018-04-01

    This paper reports on a new boundary condition formulation to model the total coronary myocardial flow and resistance characteristics of the myocardial vascular bed for any specific patient when considered for noninvasive diagnosis of ischemia. The developed boundary condition model gives an implicit representation of the downstream truncated coronary bed. Further, it is based on incorporating patient-specific physiological parameters that can be noninvasively extracted to account for blood flow demand to the myocardium at rest and hyperemic conditions. The model is coupled to a steady three-dimensional (3D) collocated pressure-based finite volume flow solver and used to characterize the "functional significance" of a patient diseased coronary artery segment without the need for predicting the hemodynamics of the entire arterial system. Predictions generated with this boundary condition provide a deep understanding of the inherent challenges behind noninvasive image-based diagnostic techniques when applied to human diseased coronary arteries. The overall numerical method and formulated boundary condition model are validated via two computational-based procedures and benchmarked with available measured data. The newly developed boundary condition is used via a designed computational methodology to (a) confirm the need for incorporating patient-specific physiological parameters when modeling the downstream coronary resistance, (b) explain the discrepancies presented in the literature between measured and computed fractional flow reserve (FFRCT), and (c) discuss the current limitations and future challenges in shifting to noninvasive assessment of ischemia.

  16. Assessment of a conceptual hydrological model and artificial neural networks for daily outflows forecasting

    NARCIS (Netherlands)

    Rezaeianzadeh, M.; Stein, A.; Tabari, H.; Abghari, H.; Jalalkamali, N.; Hosseinipour, E.Z.; Singh, V.P.

    2013-01-01

    Artificial neural networks (ANNs) are used by hydrologists and engineers to forecast flows at the outlet of a watershed. They are employed in particular where hydrological data are limited. Despite these developments, practitioners still prefer conventional hydrological models. This study applied

  17. Strong decays of sc-bar mesons in the covariant oscillator quark model with the U tilde (4)DS x O(3, 1)L-classification scheme

    International Nuclear Information System (INIS)

    Maeda, Tomohito; Yamada, Kenji; Oda, Masuho; Ishida, Shin

    2010-01-01

    We investigate the strong decays with one pseudoscalar emission of charmed strange mesons in the covariant oscillator quark model. The wave functions of composite sc-bar mesons are constructed as the irreducible representations of the U tilde (4) DS xO(3,1) L . Through the observed mass and results of decay study we discuss a novel assignment of observed charmed strange mesons from the viewpoint of the U tilde (4) DS x O(3,1) L -classification scheme. It is shown that D s0 * (2317) and D s1 (2460) are consistently explained as ground state chiralons, appeared in the U tilde (4) DS xO(3,1) L scheme. Furthermore, it is also found that recently-observed D s1 * (2710) could be described as first excited state chiralon. (author)

  18. Modeling the buoyancy-driven Black Sea Water outflow into the North Aegean Sea

    Directory of Open Access Journals (Sweden)

    Nikolaos Kokkos

    2016-04-01

    Full Text Available A three-dimensional numerical model was applied to simulate the Black Sea Water (BSW outflux and spreading over the North Aegean Sea, and its impact on circulation and stratification–mixing dynamics. Model results were validated against satellite-derived sea surface temperature and in-situ temperature and salinity profiles. Further, the model results were post-processed in terms of the potential energy anomaly, ϕ, analyzing the factors contributing to its change. It occurs that BSW contributes significantly on the Thracian Sea water column stratification, but its signal reduces in the rest of the North Aegean Sea. The BSW buoyancy flux contributed to the change of ϕ in the Thracian Sea by 1.23 × 10−3 W m−3 in the winter and 7.9 × 10−4 W m−3 in the summer, significantly higher than the corresponding solar heat flux contribution (1.41 × 10−5 W m−3 and 7.4 × 10−5 W m−3, respectively. Quantification of the ϕ-advective term crossing the north-western BSW branch (to the north of Lemnos Island, depicted a strong non-linear relation to the relative vorticity of Samothraki Anticyclone. Similar analysis for the south-western branch illustrated a relationship between the ϕ-advective term sign and the relative vorticity in the Sporades system. The ϕ-mixing term increases its significance under strong winds (>15 m s−1, tending to destroy surface meso-scale eddies.

  19. Acute Ozone (O3) Exposure Accelerates Diet-Induced Pulmonary Injury and Metabolic Alterations in a Rat Model of Type II Diabetes

    Science.gov (United States)

    Abstract for Society of Toxicology, March 22-25, 2015, San Diego, CAAcute Ozone (O3) Exposure Accelerates Diet-Induced Pulmonary Injury and Metabolic Alterations in a Rat Model of Type II DiabetesS.J. Snow1,3, D. Miller2, V. Bass2, M. Schladweiler3, A. Ledbetter3, J. Richards3, C...

  20. CLC in packed beds using syngas and CuO/Al2O3: model description and experimental validation

    NARCIS (Netherlands)

    Hamers, H.P.; Gallucci, F.; Cobden, P.D.; Kimball, E.; Sint Annaland, M. van

    2014-01-01

    The objective of this work is to study the performance of the oxygen carrier in a packed bed with periodic switching between oxidizing and reducing conditions. In this paper the performance of CuO/Al2O3 as the oxygen carrier in a packed bed reactor with syngas as the fuel are investigated, while

  1. The removal of COD and NH3-N from atrazine production wastewater treatment using UV/O3: experimental investigation and kinetic modeling.

    Science.gov (United States)

    Jing, Liang; Chen, Bing; Wen, Diya; Zheng, Jisi; Zhang, Baiyu

    2018-01-01

    In this study, a UV/O 3 hybrid advanced oxidation system was used to remove chemical oxygen demand (COD), ammonia nitrogen (NH 3 -N), and atrazine (ATZ) from ATZ production wastewater. The removal of COD and NH 3 -N, under different UV and O 3 conditions, was found to follow pseudo-first-order kinetics with rate constants ranging from 0.0001-0.0048 and 0.0015-0.0056 min -1 , respectively. The removal efficiency of ATZ was over 95% after 180 min treatment, regardless the level of UV power. A kinetic model was further proposed to simulate the removal processes and to quantify the individual roles and contributions of photolysis, direct O 3 oxidation, and hydroxyl radical (OH·) induced oxidation. The experimental and kinetic modeling results agreed reasonably well with deviations of 12.2 and 13.1% for the removal of COD and NH 3 -N, respectively. Photolysis contributed appreciably to the degradation of ATZ, while OH· played a dominant role for the removal of both COD and NH 3 -N, especially in alkaline environments. This study provides insights into the treatment of ATZ containing wastewater using UV/O 3 and broadens the knowledge of kinetics of ozone-based advanced oxidation processes.

  2. O3 stars

    International Nuclear Information System (INIS)

    Walborn, N.R.

    1982-01-01

    A brief review of the 10 known objects in this earliest spectral class is presented. Two new members are included: HD 64568 in NGC 2467 (Puppis OB2), which provides the first example of an O3 V((f*)) spectrum; and Sk -67 0 22 in the Large Magellanic Cloud, which is intermediate between types O3 If* and WN6-A. In addition, the spectrum of HDE 269810 in the LMC is reclassified as the first of type O3 III (f*). The absolute visual magnitudes of these stars are rediscussed

  3. The Neutronic Effect of Zr-rod and Sm2O3-disk in the Model of Kartini Reactor Fuel Element

    International Nuclear Information System (INIS)

    Edi-Trijono-Budisantoso; Bambang-Sumarsono; Tri-Wulan-Tjiptono

    2000-01-01

    The model of Kartini fuel element has been constructed using a variationof materials in it fuels. For basic model, the construction of fuel assemblyis a rod type fuel element with SS-304 cladding and UZrH (8.5 % wt U in 20 %enrichment) as a fuel meat and graphite reflector at the both ends of fuelmeat. By using is basic construction, the material then varied in 4 models asthe following: 1) The model with the Zr-rod in 5.76 mm diameter, is insertedat the axis of fuel meat; 2) The model with Sm 2 O 3 -disk in 1.28 mmthickness, is inserted at the both ends of fuel meat; 3) The compound ofmodel 1 and model 2; 4) The basic construction of cell without Zr-rod andSm 2 O 3 -disk. The neutronic-behavior of each model then calculated usingWIMSD4 and the result then represented as a graphics form of the correlationof parameters as the following: 1) The correlation between model and itneutron multiplication factor; 2) The comparison of neutron flux distributionfor each model. By the graphic can be concluded, that Zr-rod in the fuelelement can reduce power peaking factor to 82 % with the effect of neutronmultiplication factor reduced to 98 %, while the insertion of Sm 2 O 3 -disk atthe both ends of fuel meat can make neutron multiplication factor reduce to97 % but unfortunately the neutron peaking factor increase to 101 %. Theinsertion of Zr-rod in the axis of fuel meat, increase the safety margin offuel utilization, while the insertion of Sm 2 O 3 -disk at the both ends offuel meat can make it as the burn-able poison that maintain the neutronmultiplication factor stable for a long time utilization. (author)

  4. Theoretical Modeling for the X-ray Spectroscopy of Iron-bearing MgSiO3 under High Pressure

    Science.gov (United States)

    Wang, X.; Tsuchiya, T.

    2012-12-01

    The behaviors of iron (Fe) in MgSiO3 perovskite, including valence state, spin state, and chemical environments, at high pressures are of fundamental importance for more detailed understanding the properties of the Earth's lower mantle. The pressure induced spin transition of Fe-bearing MgO and MgSiO3 are detected often by using high-resolution K-edge X-ray emission spectroscopy (XES) [1,2,3] and confirmed by theoretical simulations. [4,5] Since the Fe K-edge XES is associated to the 3p orbital, which is far from the valence orbitals (3d and 4s), it provides no information about its coordination environments. However, the Fe L-edge XES and X-ray absorption spectroscopy (XAS) can directly present the distribution and intensity of Fe-3d character. To identify both the spin states and the coordination environments of iron-bearing MgSiO3, we systematically investigate the L-edge XAS, XES and X-ray photoelectron (XPS) spectroscopy of Fe2+- and Fe3+-bearing MgSiO3 under high pressure by using the first-principles density functional method combined with the slater-transition method. Our results show that Fe2+ and Fe3+ can be distinguished easily by taking the XPS spectra. The spin transition of Fe2+ and Fe3+ can also be clearly certified by XAS and XES. Interestingly, the broadness of L-edge XES of Fe changes depending on the iron position, meaning that its coordination environment might also be distinguishable by using high-resolution XES measurements. Research supported by the Ehime University G-COE program and KAKENHI. [1] James Badro, Guillaume Fiquet, FranÇois Guyot, Jean-Pascal Rueff, Viktor V. Struzhkin, György VankÓ, and Giulio Monaco. Science 300, 789 (2003), [2] James Badro, Jean-Pascal Rueff, György VankÓ, Giulio Monaco, Guillaume Fiquet, and FranÇois Guyot, Science 305, 383 (2004), [3] Jung-Fu Lin, Viktor V. Struzhkin, Steven D. Jacobsen, Michael Y. Hu, Paul Chow, Jennifer Kung, Haozhe Liu, Ho-kwang Mao, and Gussell J. Hemley, Nature 436, 377 (2005). [4

  5. Development of a molecular dynamic based cohesive zone model for prediction of an equivalent material behavior for Al/Al2O3 composite

    Energy Technology Data Exchange (ETDEWEB)

    Sazgar, A. [Center of Excellence in Design, Robotics and Automation, Department of Mechanical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Movahhedy, M.R., E-mail: movahhed@sharif.edu [Center of Excellence in Design, Robotics and Automation, Department of Mechanical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Mahnama, M. [School of Mechanical Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Sohrabpour, S. [Center of Excellence in Design, Robotics and Automation, Department of Mechanical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of)

    2017-01-02

    The interfacial behavior of composites is often simulated using a cohesive zone model (CZM). In this approach, a traction-separation (T-S) relation between the matrix and reinforcement particles, which is often obtained from experimental results, is employed. However, since the determination of this relation from experimental results is difficult, the molecular dynamics (MD) simulation may be used as a virtual environment to obtain this relation. In this study, MD simulations under the normal and shear loadings are used to obtain the interface behavior of Al/Al2O3 composite material and to derive the T-S relation. For better agreement with Al/Al2O3 interfacial behavior, the exponential form of the T-S relation suggested by Needleman [1] is modified to account for thermal effects. The MD results are employed to develop a parameterized cohesive zone model which is implemented in a finite element model of the matrix-particle interactions. Stress-strain curves obtained from simulations under different loading conditions and volume fractions show a close correlation with experimental results. Finally, by studying the effects of strain rate and volume fraction of particles in Al(6061-T6)/Al2O3 composite, an equivalent homogeneous model is introduced which can predict the overall behavior of the composite.

  6. Joint refinement model for the spin resolved one-electron reduced density matrix of YTiO3 using magnetic structure factors and magnetic Compton profiles data.

    Science.gov (United States)

    Gueddida, Saber; Yan, Zeyin; Kibalin, Iurii; Voufack, Ariste Bolivard; Claiser, Nicolas; Souhassou, Mohamed; Lecomte, Claude; Gillon, Béatrice; Gillet, Jean-Michel

    2018-04-28

    In this paper, we propose a simple cluster model with limited basis sets to reproduce the unpaired electron distributions in a YTiO 3 ferromagnetic crystal. The spin-resolved one-electron-reduced density matrix is reconstructed simultaneously from theoretical magnetic structure factors and directional magnetic Compton profiles using our joint refinement algorithm. This algorithm is guided by the rescaling of basis functions and the adjustment of the spin population matrix. The resulting spin electron density in both position and momentum spaces from the joint refinement model is in agreement with theoretical and experimental results. Benefits brought from magnetic Compton profiles to the entire spin density matrix are illustrated. We studied the magnetic properties of the YTiO 3 crystal along the Ti-O 1 -Ti bonding. We found that the basis functions are mostly rescaled by means of magnetic Compton profiles, while the molecular occupation numbers are mainly modified by the magnetic structure factors.

  7. Hydrostatic pressing effect on some properties of Al2O3 and Sc2O3 base ceramics

    International Nuclear Information System (INIS)

    Artemova, K.K.; Rudenko, L.A.; Maslova, G.Ya.; Levkovich, N.A.; Orlova, L.A.

    1981-01-01

    Found is the effect of hydrostatic pressing pressure on some physico-mechanical properties of the ceramic on the Al 2 O 3 and Se 2 O 3 base. Mathematical models, describing dependences of the strength of materials made of Al 2 O 3 and Sc 2 O 3 on sintering conditions and on hydrostatic pressing pressure, are plotted. Production regimes on the Al 2 O 3 and Sc 2 O 3 base ceramics with improved properties are optimized [ru

  8. Model of ultrafast demagnetization driven by spin-orbit coupling in a photoexcited antiferromagnetic insulator Cr2O3

    Science.gov (United States)

    Guo, Feng; Zhang, Na; Jin, Wei; Chang, Jun

    2017-06-01

    We theoretically study the dynamic time evolution following laser pulse pumping in an antiferromagnetic insulator Cr2O3. From the photoexcited high-spin quartet states to the long-lived low-spin doublet states, the ultrafast demagnetization processes are investigated by solving the dissipative Schrödinger equation. We find that the demagnetization times are of the order of hundreds of femtoseconds, in good agreement with recent experiments. The switching times could be strongly reduced by properly tuning the energy gaps between the multiplet energy levels of Cr3+. Furthermore, the relaxation times also depend on the hybridization of atomic orbitals in the first photoexcited state. Our results suggest that the selective manipulation of the electronic structure by engineering stress-strain or chemical substitution allows effective control of the magnetic state switching in photoexcited insulating transition-metal oxides.

  9. Studies of Quasar Outflows

    Science.gov (United States)

    Arav, Nahum

    2002-01-01

    The main aim of this research program is to determine the ionization equilibrium and abundances in quasar outflows. Especially in the broad absorption line QSO PG 0946+301. We find that the outflow's metalicity is consistent with being solar, while the abundance ratio of phosphorus to other metals is at least ten times solar. These findings are based on diagnostics that are not sensitive to saturation and partial covering effects in the BALs (Broad Adsorption Lines), which considerably weakened previous claims for enhanced metalicity. Ample evidence for these effects is seen in the spectrum.

  10. Development and evaluation of GRAL-C dispersion model, a hybrid Eulerian-Lagrangian approach capturing NO-NO 2-O 3 chemistry

    Science.gov (United States)

    Oettl, Dietmar; Uhrner, Ulrich

    2011-02-01

    Based on two recent publications using Lagrangian dispersion models to simulate NO-NO 2-O 3 chemistry for industrial plumes, a similar modified approach was implemented using GRAL-C ( Graz Lagrangian Model with Chemistry) and tested on two urban applications. In the hybrid dispersion model GRAL-C, the transport and turbulent diffusion of primary species such as NO and NO 2 are treated in a Lagrangian framework while those of O 3 are treated in an Eulerian framework. GRAL-C was employed on a one year street canyon simulation in Berlin and on a four-day simulation during a winter season in Graz, the second biggest city in Austria. In contrast to Middleton D.R., Jones A.R., Redington A.L., Thomson D.J., Sokhi R.S., Luhana L., Fisher B.E.A. (2008. Lagrangian modelling of plume chemistry for secondary pollutants in large industrial plumes. Atmospheric Environment 42, 415-427) and Alessandrini S., Ferrero E. (2008. A Lagrangian model with chemical reactions: application in real atmosphere. Proceedings of the 12th Int. Conf. on Harmonization within atmospheric dispersion modelling for regulatory purposes. Croatian Meteorological Journal, 43, ISSN: 1330-0083, 235-239) the treatment of ozone was modified in order to facilitate urban scale simulations encompassing dense road networks. For the street canyon application, modelled daily mean NO x/NO 2 concentrations deviated by +0.4%/-15% from observations, while the correlations for NO x and NO 2 were 0.67 and 0.76 respectively. NO 2 concentrations were underestimated in summer, but were captured well for other seasons. In Graz a fair agreement for NO x and NO 2 was obtained between observed and modelled values for NO x and NO 2. Simulated diurnal cycles of NO 2 and O 3 matched observations reasonably well, although O 3 was underestimated during the day. A possible explanation here might lie in the non-consideration of volatile organic compounds (VOCs) chemistry.

  11. Defect chemistry modelling of oxygen-stoichiometry, vacancy concentrations, and conductivity of (La1-xSrx)(y)MnO3 +/-delta

    DEFF Research Database (Denmark)

    Poulsen, F.W.

    2000-01-01

    model, based on delocalised electrons, electron holes and all B-ions being trivalent is given in Appendix A. The sequential mathematical method allows us to calculate the high temperature oxygen partial pressure dependent properties of (La1-xSrx)(y)MnO3+/-delta in a unified manner irrespective...... are calculated by the small polaron model containing only ionic species - the B-ion may be Mn-B' (Mn2+), Mn-B(x) (Mn3+), and Mn-B(Mn4+). The A/B-ratio = y greatly influences the oxygen stoichiometry, oxygen ion vacancy- and cation vacancy concentrations and the total conductivity. Calculations are given...

  12. Porous (Ba,SrTiO3 ceramics for tailoring dielectric and tunability properties: Modelling and experiment

    Directory of Open Access Journals (Sweden)

    Roxana E. Stanculescu

    2017-12-01

    Full Text Available 3D Finite Element Method simulations were employed in order to describe tunability properties in anisotropic porous paraelectric structures. The simulations predicted that properties of a ceramic can be tailored by using various levels of porosity. Porous Ba0.6Sr0.4TiO3 (BST ceramics have been studied in order to investigate the influence of porosity on their functional properties. The BST ceramics with various porosity levels have been obtained by solid-state reaction. Lamellar graphite in different concentration of 10, 20 and 35 vol.% was added as sacrificial pore forming agent. The structural, microstructural, dielectric and tunability properties were investigated. By comparison with dense BST ceramic, porous samples present a fracture mode transformation from intragranular to an intergranular fracture and a decrease of grain size. Lower dielectric constants, low dielectric losses, but higher values of tunability than in the dense material were obtained in the porous BST structures as a result of local field inhomogeneity generated by the presence of air pores-ceramic interfaces.

  13. Modeling local structure using crystal field and spin Hamiltonian parameters: the tetragonal FeK3+-OI2- defect center in KTaO3 crystal

    International Nuclear Information System (INIS)

    Gnutek, P; Rudowicz, C; Yang, Z Y

    2009-01-01

    The local structure and the spin Hamiltonian (SH) parameters, including the zero-field-splitting (ZFS) parameters D and (a+2F/3), and the Zeeman g factors g || and g perpendicular , are theoretically investigated for the Fe K 3+ -O I 2- center in KTaO 3 crystal. The microscopic SH (MSH) parameters are modeled within the framework of the crystal field (CF) theory employing the CF analysis (CFA) package, which also incorporates the MSH modules. Our approach takes into account the spin-orbit interaction as well as the spin-spin and spin-other-orbit interactions omitted in previous studies. The superposition model (SPM) calculations are carried out to provide input CF parameters for the CFA/MSH package. The combined SPM-CFA/MSH approach is used to consider various structural models for the Fe K 3+ -O I 2- defect center in KTaO 3 . This modeling reveals that the off-center displacement of the Fe 3+ ions, Δ 1 (Fe 3+ ), combined with an inward relaxation of the nearest oxygen ligands, Δ 2 (O 2- ), and the existence of the interstitial oxygen O I 2- give rise to a strong tetragonal crystal field. This finding may explain the large ZFS experimentally observed for the Fe K 3+ -O I 2- center in KTaO 3 . Matching the theoretical MSH predictions with the available structural data as well as electron magnetic resonance (EMR) and optical spectroscopy data enables predicting reasonable ranges of values of Δ 1 (Fe 3+ ) and Δ 2 (O 2- ) as well as the possible location of O I 2- ligands around Fe 3+ ions in KTaO 3 . The defect structure model obtained using the SPM-CFA/MSH approach reproduces very well the ranges of the experimental SH parameters D, g || and g perpendicular and importantly yields not only the correct magnitude of D but also the sign, unlike previous studies. More reliable predictions may be achieved when experimental data on (a+2F/3) and/or crystal field energy levels become available. Comparison of our results with those arising from alternative models existing

  14. Evidence for Ultra-Fast Outflows in Radio-Quiet AGNs. 2; Detailed Photoionization Modeling of Fe K-Shell Absorption Lines

    Science.gov (United States)

    Tombesi, Francesco; Clapp, M.; Reeves, J. N.; Palumbo, G. G. C.; Braito, V.; Dadina, M.

    2011-01-01

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet AGNs. In the previous paper of this series we defined UFOs as those absorbers with an outflow velocity higher than 10,000km/s and assessed the statistical significance of the associated blue shifted FeK absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. In the present paper we report a detailed curve of growth analysis and directly model the FeK absorbers with the Xstar photo-ionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35%. The outflow velocity distribution spans from \\sim10,000km/s (\\sim0.03c) up to \\siml00,000kmis (\\sim0.3c), with a peak and mean value of\\sim42,000km/s (\\sim0.14c). The ionization parameter is very high and in the range log\\xi 3-6 erg s/cm, with a mean value of log\\xi 4.2 erg s/cm. The associated column densities are also large, in the range N_H\\siml0(exp 22)-10(exp 24)/sq cm, with a mean value of N_H\\siml0(exp23)/sq cm. We discuss and estimate how selection effects, such as those related to the limited instrumental sensitivity at energies above 7keV, may hamper the detection of even higher velocities and higher ionization absorbers. We argue that, overall, these results point to the presence of extremely ionized and possibly almost Compton thick outflowing material in the innermost regions of AGNs. This also suggests that UFOs may potentially play a significant role in the expected cosmological feedback from AGNs and their study can provide important clues on the connection between accretion disks, winds and jets.

  15. EVIDENCE FOR ULTRA-FAST OUTFLOWS IN RADIO-QUIET ACTIVE GALACTIC NUCLEI. II. DETAILED PHOTOIONIZATION MODELING OF Fe K-SHELL ABSORPTION LINES

    International Nuclear Information System (INIS)

    Tombesi, F.; Cappi, M.; Dadina, M.; Reeves, J. N.; Palumbo, G. G. C.; Braito, V.

    2011-01-01

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet active galactic nuclei (AGNs). These have been detected essentially through blueshifted Fe XXV/XXVI K-shell transitions. In the previous paper of this series we defined UFOs as those highly ionized absorbers with an outflow velocity higher than 10,000 km s –1 and assessed the statistical significance of the associated blueshifted absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. The present paper is an extension of that work. First, we report a detailed curve of growth analysis of the main Fe XXV/XXVI transitions in photoionized plasmas. Then, we estimate an average spectral energy distribution for the sample sources and directly model the Fe K absorbers in the XMM-Newton spectra with the detailed Xstar photoionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35% and that the majority of the Fe K absorbers are indeed associated with UFOs. The outflow velocity distribution spans from ∼10,000 km s –1 (∼0.03c) up to ∼100,000 km s –1 (∼0.3c), with a peak and mean value of ∼42,000 km s –1 (∼0.14c). The ionization parameter is very high and in the range log ξ ∼ 3-6 erg s –1 cm, with a mean value of log ξ ∼ 4.2 erg s –1 cm. The associated column densities are also large, in the range N H ∼ 10 22 -10 24 cm –2 , with a mean value of N H ∼ 10 23 cm –2 . We discuss and estimate how selection effects, such as those related to the limited instrumental sensitivity at energies above 7 keV, may hamper the detection of even higher velocities and higher ionization absorbers. We argue that, overall, these results point to the presence of extremely ionized and possibly almost Compton-thick outflowing material in the innermost regions of AGNs. This also suggests that UFOs may potentially play a significant role in the expected

  16. Diffusivity, solubility and thermodynamic modelling of diffusion growth of Ga"3"+-doped LiTaO_3 thin film for integrated optics

    International Nuclear Information System (INIS)

    Zhang, De-Long; Zhang, Qun; Zhang, Pei; Kang, Jian; Wong, Wing-Han; Yu, Dao-Yin

    2016-01-01

    Graphical abstract: Diffusion growth of Ga"3"+-doped LiTaO_3(LT) thin film was studied thermodynamically. Some Ga"3"+-doped LT thin films were grown on LT surface by in-diffusion of homogeneously coated Ga_2O_3 film at the temperature range of (1273 to 1473) K. The Ga"3"+ profile in the grown thin film was analyzed by secondary ion mass spectrometry. Form the measured Ga"3"+ profiles, some thermodynamic parameters were obtained. These include diffusivity, diffusion constant, chemical activation energy, solubility, solubility constant and enthalpy of solution. These parameters are crucial to design and growth of a Ga"3"+-doped LT thin film with desired Ga"3"+ profile for integrated optics application. A thermodynamic model is suggested for the growth and verified experimentally. - Highlights: • Diffusion growth of Ga"3"+-doped LiTaO_3 thin film were studied thermodynamically. • Diffusion constant is 1.41 · 10"−"6 m"2/s and activation energy is 237.2 kJ/mol. • Solubility constant is 22.9 · 10"2"6 ions/m"3 and enthalpy of solution is 28.9 kJ/mol. • Ga"3"+ dopant has small effect on LiTaO_3 refractive index. • Ga"3"+ growth can be described by a Fick-type equation with a constant diffusivity. - Abstract: A thermodynamic study was performed on diffusion growth of Ga"3"+-doped LiTaO_3(LT) thin film for integrated optics. Some Ga"3"+-doped LT thin films were grown on LT surface by in-diffusion of homogeneously coated Ga_2O_3 film at the temperature range of (1273 to 1473) K. After growth, the refractive indices at Ga"3"+-doped and un-doped surface parts were measured by prism coupling technique and Li composition there was evaluated from the measured refractive indices. The results show that Ga"3"+ dopant has small effect on the LT index. Li_2O out-diffusion is not measurable. The Ga"3"+ profile in the grown thin film was analysed by secondary ion mass spectrometry. It is found that the grown Ga"3"+ ions follow a complementary error function profile. A

  17. GALAXY OUTFLOWS WITHOUT SUPERNOVAE

    Energy Technology Data Exchange (ETDEWEB)

    Sur, Sharanya [Indian Institute of Astrophysics, 2nd Block, Koramangala, Bangalore 560034 (India); Scannapieco, Evan [School of Earth and Space Exploration, Arizona State University, P.O. Box 876004, Tempe-85287 (United States); Ostriker, Eve C., E-mail: sharanya.sur@iiap.res.in, E-mail: sharanya.sur@asu.edu [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

    2016-02-10

    High surface density, rapidly star-forming galaxies are observed to have ≈50–100 km s{sup −1} line of sight velocity dispersions, which are much higher than expected from supernova driving alone, but may arise from large-scale gravitational instabilities. Using three-dimensional simulations of local regions of the interstellar medium, we explore the impact of high velocity dispersions that arise from these disk instabilities. Parametrizing disks by their surface densities and epicyclic frequencies, we conduct a series of simulations that probe a broad range of conditions. Turbulence is driven purely horizontally and on large scales, neglecting any energy input from supernovae. We find that such motions lead to strong global outflows in the highly compact disks that were common at high redshifts, but weak or negligible mass loss in the more diffuse disks that are prevalent today. Substantial outflows are generated if the one-dimensional horizontal velocity dispersion exceeds ≈35 km s{sup −1}, as occurs in the dense disks that have star-formation rate (SFR) densities above ≈0.1 M{sub ⊙} yr{sup −1} kpc{sup −2}. These outflows are triggered by a thermal runaway, arising from the inefficient cooling of hot material coupled with successive heating from turbulent driving. Thus, even in the absence of stellar feedback, a critical value of the SFR density for outflow generation can arise due to a turbulent heating instability. This suggests that in strongly self-gravitating disks, outflows may be enhanced by, but need not caused by, energy input from supernovae.

  18. Mathematical Modelling of Catalytic Fixed-Bed Reactor for Carbon Dioxide Reforming of Methane over Rh/Al2O3 Catalyst

    Directory of Open Access Journals (Sweden)

    New Pei Yee

    2008-04-01

    Full Text Available A one-dimensional mathematical model was developed to simulate the performance of catalytic fixed bedreactor for carbon dioxide reforming of methane over Rh/Al2O3 catalyst at atmospheric pressure. The reactionsinvolved in the system are carbon dioxide reforming of methane (CORM and reverse water gas shiftreaction (RWGS. The profiles of CH4 and CO2 conversions, CO and H2 yields, molar flow rate and molefraction of all species as well as reactor temperature along the axial bed of catalyst were simulated. In addition,the effects of different reactor temperature on the reactor performance were also studied. The modelscan also be applied to analyze the performances of lab-scale micro reactor as well as pilot-plant scale reactorwith certain modifications and model verification with experimental data. © 2008 BCREC UNDIP. All rights reserved.[Received: 20 August 2008; Accepted: 25 September 2008][How to Cite: N.A.S. Amin, I. Istadi, N.P. Yee. (2008. Mathematical Modelling of Catalytic Fixed-Bed Reactor for Carbon Dioxide Reforming of Methane over Rh/Al2O3 Catalyst. Bulletin of Chemical Reaction Engineering and Catalysis, 3 (1-3: 21-29. doi:10.9767/bcrec.3.1-3.19.21-29

  19. Active galactic nucleus outflows in galaxy discs

    Science.gov (United States)

    Hartwig, Tilman; Volonteri, Marta; Dashyan, Gohar

    2018-05-01

    Galactic outflows, driven by active galactic nuclei (AGNs), play a crucial role in galaxy formation and in the self-regulated growth of supermassive black holes (BHs). AGN feedback couples to and affects gas, rather than stars, and in many, if not most, gas-rich galaxies cold gas is rotationally supported and settles in a disc. We present a 2D analytical model for AGN-driven outflows in a gaseous disc and demonstrate the main improvements, compared to existing 1D solutions. We find significant differences for the outflow dynamics and wind efficiency. The outflow is energy-driven due to inefficient cooling up to a certain AGN luminosity (˜1043 erg s-1 in our fiducial model), above which the outflow remains momentum-driven in the disc up to galactic scales. We reproduce results of 3D simulations that gas is preferentially ejected perpendicular to the disc and find that the fraction of ejected interstellar medium is lower than in 1D models. The recovery time of gas in the disc, defined as the free-fall time from the radius to which the AGN pushes the ISM at most, is remarkably short, of the order 1 Myr. This indicates that AGN-driven winds cannot suppress BH growth for long. Without the inclusion of supernova feedback, we find a scaling of the BH mass with the halo velocity dispersion of MBH ∝ σ4.8.

  20. Enhancing photocatalysis in SrTiO3 by using Ag nanoparticles: A two-step excitation model for surface plasmon-enhanced photocatalysis

    International Nuclear Information System (INIS)

    Ma, Lei; Sun, Tao; Cai, Hua; Zhou, Zhi-Quan; Sun, Jian; Lu, Ming

    2015-01-01

    Surface plasmon (SP)-enhanced ultraviolet and visible photocatalytic activities of SrTiO 3 (STO) are observed after incorporating Ag nanoparticles (Ag-NPs) on STO surfaces. A two-step excitation model is proposed to explain the SP-enhanced photocatalysis. The point of the model is that an electron at the valence band of STO is first excited onto the Fermi level of Ag-NP by the SP field generated on the Ag-NP, and then injected into the conduction band of STO from the SP band, leaving a hole at the valence band of STO. A full redox catalytic reaction at the surface of STO is then available. For Ag-NP incorporated STO, up-converted and inter-band photoluminescence emissions of STO are observed, and nonlinear evolutions of photocatalytic activity with illumination light powers are found. Furthermore, near infrared photocatalysis is detected. These results support the proposed model

  1. Geometry of anisotropic CO outflows

    International Nuclear Information System (INIS)

    Liseau, R.; Sandell, G.; Helsinki Univ., Observatory, Finland)

    1986-01-01

    A simple geometrical model for the space motions of the bipolar high-velocity CO outflows in regions of recent, active star formation is proposed. It is assumed that the velocity field of the neutral gas component can be represented by large-scale uniform motions. From observations of the spatial distribution and from the characteristics of the line shape of the high-velocity molecular gas emission the geometry of the line-emitting regions can be inferred, i.e., the direction in space and the collimating angle of the flow. The model has been applied to regions where a check on presently obtained results is provided by independent optical determinations of the motions of Herbig-Haro objects associated with the CO flows. These two methods are in good agreement and, furthermore, the results obtained provide convincingly strong evidence for the physical association of CO outflows and Herbig-Haro objects. This also supports the common view that a young stellar central source is responsible for the active phenomena observed in its environmental neighborhood. It is noteworthy that within the framework of the model the determination of the flow geometry of the high-velocity gas from CO measurements is independent of the distance to the source and, furthermore, can be done at relatively low spatial resolution. 32 references

  2. DISCOVERY OF RELATIVISTIC OUTFLOW IN THE SEYFERT GALAXY Ark 564

    International Nuclear Information System (INIS)

    Gupta, A.; Mathur, S.; Krongold, Y.; Nicastro, F.

    2013-01-01

    We present Chandra High Energy Transmission Grating Spectra of the narrow-line Seyfert-1 galaxy Ark 564. The spectrum shows numerous absorption lines which are well modeled with low-velocity outflow components usually observed in Seyfert galaxies. There are, however, some residual absorption lines which are not accounted for by low-velocity outflows. Here, we present identifications of the strongest lines as Kα transitions of O VII (two lines) and O VI at outflow velocities of ∼0.1c. These lines are detected at 6.9σ, 6.2σ, and 4.7σ, respectively, and cannot be due to chance statistical fluctuations. Photoionization models with ultra-high velocity components improve the spectral fit significantly, providing further support for the presence of relativistic outflow in this source. Without knowing the location of the absorber, its mass and energy outflow rates cannot be well constrained; we find E-dot (outflow)/L bol lower limit of ≥0.006% assuming a bi-conical wind geometry. This is the first time that absorption lines with ultra-high velocities are unambiguously detected in the soft X-ray band. The presence of outflows with relativistic velocities in active galactic nuclei (AGNs) with Seyfert-type luminosities is hard to understand and provides valuable constraints to models of AGN outflows. Radiation pressure is unlikely to be the driving mechanism for such outflows and magnetohydrodynamic may be involved

  3. The impact of remittances outflows on the economy of Poland

    OpenAIRE

    LASTOVETSKA ROKSOLANA ORESTIVNA

    2015-01-01

    The impact of remittances outflows on the economy of Poland is analyzed in the article. Based on historical data the vector autoregression model (VAR) was built to examine the effects of the sharp rise in the volume of remittances outflows. The model results are presented for the next macroeconomic indicators: GDP, inflation, interest rate and exchange rate.

  4. A sensitivity study of parameters in the Nazaroff-Cass IAQ model with respect to indoor concentrations of O3, NO, NO2

    International Nuclear Information System (INIS)

    Drakou, G.; Zerefos, C.; Ziomas, I.

    2000-01-01

    The indoor O 3 , NO, NO 2 concentrations and their corresponding indoor/outdoor (I/O) concentration ratios are predicted in this paper for some representative buildings, using the Nazaroff-Cass indoor air quality models. This paper presents and systemises the relationship between indoor and air pollution concentrations and the buildings' design, use and operation. The building parameters which are determined to be main factors affecting the air pollutant concentrations are: the physical dimensions of the building and the materials of construction, the buildings' air exchange rate with outdoors and the indoor air pollutant sources. Changes of ultraviolet photon fluxes, of temperatures and of relative humidity indoors, have little effect on indoor O 3 , NO and NO 2 concentrations, for air exchange rates above 0.5 ach. Special attention must be given when a building has a very low air exchange rate, under which conditions the effect of a small change in any of the factors determining the indoor air quality of the building will be much more noticeable than in a building with high air exchange rate. (Author)

  5. Modeling C1-C4 Alkyl Nitrate Photochemistry and Their Impacts on O3 Production in Urban and Suburban Environments of Hong Kong

    Science.gov (United States)

    Lyu, X. P.; Guo, H.; Wang, N.; Simpson, I. J.; Cheng, H. R.; Zeng, L. W.; Saunders, S. M.; Lam, S. H. M.; Meinardi, S.; Blake, D. R.

    2017-10-01

    As intermediate products of photochemical reactions, alkyl nitrates (RONO2) regulate ozone (O3) formation. In this study, a photochemical box model incorporating master chemical mechanism well reproduced the observed RONO2 at an urban and a mountainous site, with index of agreement in the range of 0.66-0.73. The value 0.0003 was identified to be the most appropriate branching ratio for C1 RONO2, with the error less than 50%. Although levels of the parent hydrocarbons and nitric oxide (NO) were significantly higher at the urban site than the mountainous site, the production of C2-C3 RONO2 was comparable to or even lower than at the mountainous site, due to the lower concentrations of oxidative radicals in the urban environment. Based on the profiles of air pollutants at the mountainous site, the formation of C2-C4 RONO2 was limited by NOx (volatile organic compounds (VOCs)) when total volatile organic compounds (TVOCs)/NOx was higher (lower) than 10.0 ± 0.4 parts per billion by volume (ppbv)/ppbv. This dividing ratio decreased (p controlling O3 formation and the relative abundances of TVOCs and NOx.

  6. Simultaneous influence of gas mixture composition and process temperature on Fe2O3->FeO reduction kinetics: neural network modeling

    Directory of Open Access Journals (Sweden)

    K. Piotrowski

    2005-09-01

    Full Text Available The kinetics of Fe2O3->FeO reaction was investigated. The thermogravimetric (TGA data covered the reduction of hematite both by pure species (nitrogen diluted CO or H2 and by their mixture. The conventional analysis has indicated that initially the reduction of hematite is a complex, surface controlled process, however once a thin layer of lower oxidation state iron oxides (magnetite, wüstite is formed on the surface, it changes to diffusion control. Artificial Neural Network (ANN has proved to be a convenient tool for modeling of this complex, heterogeneous reaction runs within the both (kinetic and diffusion regions, correctly considering influence of temperature and gas composition effects and their complex interactions. ANN's model shows the capability to mimic some extreme (minimum of the reaction rate within the determined temperature window, while the Arrhenius dependency is of limited use.

  7. Effect of structural distortion on the electronic band structure of NaOsO3 studied within density functional theory and a three-orbital model

    Science.gov (United States)

    Mohapatra, Shubhajyoti; Bhandari, Churna; Satpathy, Sashi; Singh, Avinash

    2018-04-01

    Effects of the structural distortion associated with the OsO6 octahedral rotation and tilting on the electronic band structure and magnetic anisotropy energy for the 5 d3 compound NaOsO3 are investigated using the density functional theory (DFT) and within a three-orbital model. Comparison of the essential features of the DFT band structures with the three-orbital model for both the undistorted and distorted structures provides insight into the orbital and directional asymmetry in the electron hopping terms resulting from the structural distortion. The orbital mixing terms obtained in the transformed hopping Hamiltonian resulting from the octahedral rotations are shown to account for the fine features in the DFT band structure. Staggered magnetization and the magnetic character of states near the Fermi energy indicate weak coupling behavior.

  8. Modelling Cr depletion under a growing Cr2O3 layer on austenitic stainless steel: the influence of grain boundary diffusion

    DEFF Research Database (Denmark)

    Hansson, Anette Nørgaard; Hattel, Jesper Henri; Dahl, Kristian Vinter

    2009-01-01

    according to a parabolic rate law as a consequence of rate limiting diffusion of Cr cations through the oxide layer; the retraction of the oxide/alloy interface associated with the removal of Cr atoms from the substrate is included in the calculations. Numerically, the movement of the oxide/alloy interface......The oxidation behaviour of austenitic stainless steels in the temperature range 723–1173K is strongly influenced by the grain size of the oxidizing alloy. In this work the evolution of the concentration profiles of Cr, Ni and Fe in the substrate below a growing Cr2O3 layer is simulated...... with a Fisher-type numerical model, which takes both volume and grain boundary diffusion into consideration. The model is based on a two-dimensional control volume-based solution of Fick’s 2nd law for multicomponent diffusion and includes crossterm diffusion coefficients. The oxide layer is assumed to grow...

  9. The energetics of AGN radiation pressure-driven outflows

    Science.gov (United States)

    Ishibashi, W.; Fabian, A. C.; Maiolino, R.

    2018-05-01

    The increasing observational evidence of galactic outflows is considered as a sign of active galactic nucleus (AGN) feedback in action. However, the physical mechanism responsible for driving the observed outflows remains unclear, and whether it is due to momentum, energy, or radiation is still a matter of debate. The observed outflow energetics, in particular the large measured values of the momentum ratio (\\dot{p}/(L/c) ˜ 10) and energy ratio (\\dot{E}_k/L ˜ 0.05), seems to favour the energy-driving mechanism; and most observational works have focused their comparison with wind energy-driven models. Here, we show that AGN radiation pressure on dust can adequately reproduce the observed outflow energetics (mass outflow rate, momentum flux, and kinetic power), as well as the scalings with luminosity, provided that the effects of radiation trapping are properly taken into account. In particular, we predict a sublinear scaling for the mass outflow rate (\\dot{M} ∝ L^{1/2}) and a superlinear scaling for the kinetic power (\\dot{E}_k ∝ L^{3/2}), in agreement with the observational scaling relations reported in the most recent compilation of AGN outflow data. We conclude that AGN radiative feedback can account for the global outflow energetics, at least equally well as the wind energy-driving mechanism, and therefore both physical models should be considered in the interpretation of future AGN outflow observations.

  10. ALMA OBSERVATIONS OF THE HH 46/47 MOLECULAR OUTFLOW

    International Nuclear Information System (INIS)

    Arce, Héctor G.; Mardones, Diego; Garay, Guido; Corder, Stuartt A.; Noriega-Crespo, Alberto; Raga, Alejandro C.

    2013-01-01

    The morphology, kinematics, and entrainment mechanism of the HH 46/47 molecular outflow were studied using new ALMA Cycle 0 observations. Results show that the blue and red lobes are strikingly different. We argue that these differences are partly due to contrasting ambient densities that result in different wind components having a distinct effect on the entrained gas in each lobe. A 29 point mosaic, covering the two lobes at an angular resolution of about 3'', detected outflow emission at much higher velocities than previous observations, resulting in significantly higher estimates of the outflow momentum and kinetic energy than previous studies of this source, using the CO(1-0) line. The morphology and the kinematics of the gas in the blue lobe are consistent with models of outflow entrainment by a wide-angle wind, and a simple model describes the observed structures in the position-velocity diagram and the velocity-integrated intensity maps. The red lobe exhibits a more complex structure, and there is evidence that this lobe is entrained by a wide-angle wind and a collimated episodic wind. Three major clumps along the outflow axis show velocity distribution consistent with prompt entrainment by different bow shocks formed by periodic mass ejection episodes which take place every few hundred years. Position-velocity cuts perpendicular to the outflow cavity show gradients where the velocity increases toward the outflow axis, inconsistent with outflow rotation. Additionally, we find evidence for the existence of a small outflow driven by a binary companion

  11. A coupled RL and transport model for mixed-field proton irradiation of Al2O3:C

    DEFF Research Database (Denmark)

    Greilich, Steffen; Edmund, Jens Morgenthaler; Jain, Mayank

    2008-01-01

    effects and inelastic hadronic scattering occur in proton therapy dosimetry. To investigate these aspects in relation to our system, we have combined simulation of particle transportation with a luminescence generation code based on track structure theory. The model was found to qualitatively reproduce...... the main features in experimental data from proton irradiations. (c) 2008 Elsevier Ltd. All rights reserved....

  12. Mathematical modeling of sustainability of porous Al2O3 growth during two-stage anodization process

    Science.gov (United States)

    Aryslanova, Elizaveta M.; Alfimov, Anton V.; Chivilikhin, Sergey A.

    2015-06-01

    Currently, due to the development of nanotechnology and metamaterials, it has become important to obtain regular nanoporous structures with different parameters, such as porous anodic alumina films that are used for synthesis of various nanocomposites. In this work we consider the motion of the interfaces between electrolyte and alumina layers, and between alumina and aluminum layers. We also took into account the dynamics of moving boundaries and the change of small perturbations of these boundaries. Each area under Laplace's equation is solved for the potential of the electric field. The growth of porous alumina is described with the theory of small perturbations. Small perturbations of the interface are considered, which lead to small changes in potential and current in the boundaries. As a result of the developed model we obtained the minimum distance between centers of aluminum oxide pores in the beginning of anodizing process and the wavelength of porous structure irregularities.

  13. Heuristic modelling of laser written mid-infrared LiNbO3 stressed-cladding waveguides.

    Science.gov (United States)

    Nguyen, Huu-Dat; Ródenas, Airán; Vázquez de Aldana, Javier R; Martínez, Javier; Chen, Feng; Aguiló, Magdalena; Pujol, Maria Cinta; Díaz, Francesc

    2016-04-04

    Mid-infrared lithium niobate cladding waveguides have great potential in low-loss on-chip non-linear optical instruments such as mid-infrared spectrometers and frequency converters, but their three-dimensional femtosecond-laser fabrication is currently not well understood due to the complex interplay between achievable depressed index values and the stress-optic refractive index changes arising as a function of both laser fabrication parameters, and cladding arrangement. Moreover, both the stress-field anisotropy and the asymmetric shape of low-index tracks yield highly birefringent waveguides not useful for most applications where controlling and manipulating the polarization state of a light beam is crucial. To achieve true high performance devices a fundamental understanding on how these waveguides behave and how they can be ultimately optimized is required. In this work we employ a heuristic modelling approach based on the use of standard optical characterization data along with standard computational numerical methods to obtain a satisfactory approximate solution to the problem of designing realistic laser-written circuit building-blocks, such as straight waveguides, bends and evanescent splitters. We infer basic waveguide design parameters such as the complex index of refraction of laser-written tracks at 3.68 µm mid-infrared wavelengths, as well as the cross-sectional stress-optic index maps, obtaining an overall waveguide simulation that closely matches the measured mid-infrared waveguide properties in terms of anisotropy, mode field distributions and propagation losses. We then explore experimentally feasible waveguide designs in the search of a single-mode low-loss behaviour for both ordinary and extraordinary polarizations. We evaluate the overall losses of s-bend components unveiling the expected radiation bend losses of this type of waveguides, and finally showcase a prototype design of a low-loss evanescent splitter. Developing a realistic waveguide

  14. An ab initio model of electron transport in hematite (a-Fe2O3) basal planes

    International Nuclear Information System (INIS)

    Rosso, Kevin M.; Smith, Dayle MA; Dupuis, Michel

    2003-01-01

    Transport of conduction electrons through basal planes of the hematite lattice was modeled as a valence alternation of iron cations using ab initio molecular orbital calculations and electron transfer theory. A cluster approach was successfully implemented to compute electron transfer rate-controlling quantities such as the reorganization energy and electronic coupling matrix element. Localization of a conduction electron at an iron lattice site is accompanied by large iron/oxygen bond length increases that give rise to a large inner-sphere component of the reorganization energy. The interaction between the reactant and product electronic states in the crossing?point configuration is substantial and leads to an adiabatic electron transfer system. Electron transfer is predicted to possess a small positive activation energy that turns out to be in excellent agreement with values deduced from conductivity measurements. Measured electron mobility can be explained in terms of nearest neighbor electron hops without significant contribution from iron atoms further away. Comparison of the predicted maximum polaron binding energy with the predicted half bandwidth indicates compliance with the small polaron condition. Therefore the localized electron treatment is appropriate to describe electron transport in this system

  15. Measurement of Outflow Facility Using iPerfusion.

    Directory of Open Access Journals (Sweden)

    Joseph M Sherwood

    Full Text Available Elevated intraocular pressure (IOP is the predominant risk factor for glaucoma, and reducing IOP is the only successful strategy to prevent further glaucomatous vision loss. IOP is determined by the balance between the rates of aqueous humour secretion and outflow, and a pathological reduction in the hydraulic conductance of outflow, known as outflow facility, is responsible for IOP elevation in glaucoma. Mouse models are often used to investigate the mechanisms controlling outflow facility, but the diminutive size of the mouse eye makes measurement of outflow technically challenging. In this study, we present a new approach to measure and analyse outflow facility using iPerfusion™, which incorporates an actuated pressure reservoir, thermal flow sensor, differential pressure measurement and an automated computerised interface. In enucleated eyes from C57BL/6J mice, the flow-pressure relationship is highly non-linear and is well represented by an empirical power law model that describes the pressure dependence of outflow facility. At zero pressure, the measured flow is indistinguishable from zero, confirming the absence of any significant pressure independent flow in enucleated eyes. Comparison with the commonly used 2-parameter linear outflow model reveals that inappropriate application of a linear fit to a non-linear flow-pressure relationship introduces considerable errors in the estimation of outflow facility and leads to the false impression of pressure-independent outflow. Data from a population of enucleated eyes from C57BL/6J mice show that outflow facility is best described by a lognormal distribution, with 6-fold variability between individuals, but with relatively tight correlation of facility between fellow eyes. iPerfusion represents a platform technology to accurately and robustly characterise the flow-pressure relationship in enucleated mouse eyes for the purpose of glaucoma research and with minor modifications, may be applied

  16. Hydrotreatment of solvolytically liquefied lignocellulosic biomass over NiMo/Al2O3 catalyst: Reaction mechanism, hydrodeoxygenation kinetics and mass transfer model based on FTIR

    International Nuclear Information System (INIS)

    Grilc, M.; Likozar, B.; Levec, J.

    2014-01-01

    Raw residual wood biomass, containing cellulose, hemicellulose and lignin, was liquefied at low temperature by ultrasound-assisted solvolysis and acidolysis by glycerol, diethylene glycol and p-toluenesulfonic acid. Liquefied biomass was consequently upgraded by hydrotreatment utilizing heterogeneous catalysis over NiMo/Al 2 O 3 bifunctional catalyst. Effects of temperature (200−350 °C), heating rate (2.5–10.0 K min −1 ), hydrogen/nitrogen pressure (2−8 MPa), mixing (250−1000 min −1 ), hydrogen donor solvent (tetralin) and catalyst contents on deoxygenation were established. Reactions of liquefaction products, such as levulinic acid, were quantified based on their functional groups by Fourier transform infrared spectroscopy, whereas catalyst was examined by scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction analysis (XRD). Chemical kinetics of hydrodeoxygenation (HDO), decarbonylation and decarboxylation were determined by originally developed lumped model, based on reaction mechanisms and pathways, while the external mass transfer resistance proved to be negligible under the applied hydrodynamic conditions. The presence of hydrocracking reactions was confirmed by a decrease in product viscosity, and the upgrade for energetic or fuel applications by measurements of calorific value. - Highlights: • Liquefaction of waste lignocellulosic biomass with glycerol at low temperature. • Hydrotreatment, hydrocracking and hydrodeoxygenation of liquefied waste biomass. • Deoxygenation using heterogeneous catalysis over NiMo/Al 2 O 3 bifunctional catalyst. • Proposal of reaction mechanism; chemical kinetics and mass transfer considerations. • Effect of temperature, heating rate, pressure, mixing, solvent and catalyst content

  17. Regional-scale modeling of near-ground ozone in the Central East China, source attributions and an assessment of outflow to East Asia The role of regional-scale transport during MTX2006

    Science.gov (United States)

    Li, J.; Wang, Z.; Akimoto, H.; Yamaji, K.; Takigawa, M.; Pochanart, P.; Liu, Y.; Kanaya, Y.

    2008-07-01

    A 3-D regional chemical transport model, the Nested Air Quality Prediction Model System (NAQPMS), with an on-line tracer tagging module was applied to study the source of the near-ground (pollutants. In particular, the model captured highly polluted and clean cases well. The simulated near-ground ozone over CEC is 60 85 ppbv (parts per billion by volume), higher than those (20 50 ppbv) in Japan and over the North Pacific. The simulated tagged tracer indicates that the regional-scale transport of chemically produced ozone over other areas in CEC contributes to the most fractions (49%) of the near-ground mean ozone at Mt. Tai in June, rather than the in-situ photochemistry (12%). Due to high anthropogenic and biomass burning emissions, the contributions of the ground ozone from the southern part of CEC plays the most important role (32.4 ppbv, 37.9% of total ozone) in the monthly mean ozone concentration at Mt. Tai, which even reached 59 ppbv (62%) on 6 7 June 2006. The monthly mean horizontal distribution of chemically produced ozone from various source regions indicates that the spatial distribution of O3 over CEC is controlled by the photochemical reactions. In addition, the regional-scale transport of pollutants also plays an important role in the spatial and temporal distribution of ozone over CEC. The chemically produced ozone from the southern part of the study region can be transported northeastwardly to the northern rim of CEC. The mean contribution is 5 10 ppbv, and it can reach 25 ppbv during high ozone events. This work also studied the outflow of CEC ozone and its precursors, as well as their influences and contributions to the ozone level over adjacent regions/countries. It shows that the contribution of CEC ozone to mean ozone mixing ratios over Korea Peninsula and Japan is 5 15 ppbv, of which about half was due to the direct transport of ozone from CEC and half was contributed by the ozone produced locally by the transported ozone precursors from CEC.

  18. Calcite Phase Conversion Prediction Model for CaO-Al2O3-SiO2 Slag: An Aqueous Carbonation Process at Ambient Pressure

    Science.gov (United States)

    Zhang, Huining; Dong, Jianhong; Li, Hui; Xiong, Huihui; Xu, Anjun

    2018-06-01

    To evaluate the effect of the mineralogical phase on carbonation efficiency for CaO-Al2O3-SiO2 slag, a calcite phase conversion prediction model is proposed. This model combines carbon dioxide solubility with carbonation reaction kinetic analysis to improve the prediction capability. The effect of temperature and carbonation time on the carbonation degree is studied in detail. Results show that the reaction rate constant ranges from 0.0135 h-1 to 0.0458 h-1 and that the mineralogical phase contribution sequence for the carbonation degree is C2S, CaO, C3A and CS. The model accurately predicts the effect of temperature and carbonation time on the simulated calcite conversion, and the results agree with the experimental data. The optimal carbonation temperature and reaction time are 333 K and 90 min, respectively. The maximum carbonation efficiency is about 184.3 g/kg slag, and the simulation result of the calcite phase content in carbonated slag is about 20%.

  19. Model of daytime emissions of electronically-vibrationally excited products of O3 and O2 photolysis: application to ozone retrieval

    Directory of Open Access Journals (Sweden)

    V. A. Yankovsky

    2006-11-01

    Full Text Available The traditional kinetics of electronically excited products of O3 and O2 photolysis is supplemented with the processes of the energy transfer between electronically-vibrationally excited levels O2(a1Δg, v and O2(b1Σ+g, v, excited atomic oxygen O(1D, and the O2 molecules in the ground electronic state O2(X3Σg−, v. In contrast to the previous models of kinetics of O2(a1Δg and O2 (b1Σ+g, our model takes into consideration the following basic facts: first, photolysis of O3 and O2 and the processes of energy exchange between the metastable products of photolysis involve generation of oxygen molecules on highly excited vibrational levels in all considered electronic states – b1Σ+g, a1Δg and X3Σg−; second, the absorption of solar radiation not only leads to populating the electronic states on vibrational levels with vibrational quantum number v equal to 0 – O2(b1Σ+g, v=0 (at 762 nm and O2(a1Δg, v=0 (at 1.27 µm, but also leads to populating the excited electronic–vibrational states O2(b1Σ+g, v=1 and O2(b1Σ+g, v=2 (at 689 nm and 629 nm. The proposed model allows one to calculate not only the vertical profiles of the O2(a1Δg, v=0 and O2(b1Σg, v=0 concentrations, but also the profiles of [O2(a1Δg, v≤5], [O2 (b1Σ+g , v=1, 2] and O2(X3Σg−, v=1–35. In the altitude range 60–125 km, consideration of the electronic-vibrational kinetics significantly changes the calculated concentrations of the metastable oxygen molecules and reduces the discrepancy between the altitude profiles of ozone concentrations retrieved from the 762-nm and 1.27-µm emissions measured simultaneously.

  20. Simulation of California's Major Reservoirs Outflow Using Data Mining Technique

    Science.gov (United States)

    Yang, T.; Gao, X.; Sorooshian, S.

    2014-12-01

    The reservoir's outflow is controlled by reservoir operators, which is different from the upstream inflow. The outflow is more important than the reservoir's inflow for the downstream water users. In order to simulate the complicated reservoir operation and extract the outflow decision making patterns for California's 12 major reservoirs, we build a data-driven, computer-based ("artificial intelligent") reservoir decision making tool, using decision regression and classification tree approach. This is a well-developed statistical and graphical modeling methodology in the field of data mining. A shuffled cross validation approach is also employed to extract the outflow decision making patterns and rules based on the selected decision variables (inflow amount, precipitation, timing, water type year etc.). To show the accuracy of the model, a verification study is carried out comparing the model-generated outflow decisions ("artificial intelligent" decisions) with that made by reservoir operators (human decisions). The simulation results show that the machine-generated outflow decisions are very similar to the real reservoir operators' decisions. This conclusion is based on statistical evaluations using the Nash-Sutcliffe test. The proposed model is able to detect the most influential variables and their weights when the reservoir operators make an outflow decision. While the proposed approach was firstly applied and tested on California's 12 major reservoirs, the method is universally adaptable to other reservoir systems.

  1. Total scattering and pair distribution function analysis in modelling disorder in PZN (PbZn1/3Nb2/3O3

    Directory of Open Access Journals (Sweden)

    Ross E. Whitfield

    2016-01-01

    Full Text Available The ability of the pair distribution function (PDF analysis of total scattering (TS from a powder to determine the local ordering in ferroelectric PZN (PbZn1/3Nb2/3O3 has been explored by comparison with a model established using single-crystal diffuse scattering (SCDS. While X-ray PDF analysis is discussed, the focus is on neutron diffraction results because of the greater extent of the data and the sensitivity of the neutron to oxygen atoms, the behaviour of which is important in PZN. The PDF was shown to be sensitive to many effects not apparent in the average crystal structure, including variations in the B-site—O separation distances and the fact that 〈110〉 Pb2+ displacements are most likely. A qualitative comparison between SCDS and the PDF shows that some features apparent in SCDS were not apparent in the PDF. These tended to pertain to short-range correlations in the structure, rather than to interatomic separations. For example, in SCDS the short-range alternation of the B-site cations was quite apparent in diffuse scattering at (½ ½ ½, whereas it was not apparent in the PDF.

  2. Total scattering and pair distribution function analysis in modelling disorder in PZN (PbZn1/3Nb2/3O3)

    Science.gov (United States)

    Whitfield, Ross E.; Goossens, Darren J.; Welberry, T. Richard

    2016-01-01

    The ability of the pair distribution function (PDF) analysis of total scattering (TS) from a powder to determine the local ordering in ferroelectric PZN (PbZn1/3Nb2/3O3) has been explored by comparison with a model established using single-crystal diffuse scattering (SCDS). While X-ray PDF analysis is discussed, the focus is on neutron diffraction results because of the greater extent of the data and the sensitivity of the neutron to oxygen atoms, the behaviour of which is important in PZN. The PDF was shown to be sensitive to many effects not apparent in the average crystal structure, including variations in the B-site—O separation distances and the fact that 〈110〉 Pb2+ displacements are most likely. A qualitative comparison between SCDS and the PDF shows that some features apparent in SCDS were not apparent in the PDF. These tended to pertain to short-range correlations in the structure, rather than to interatomic separations. For example, in SCDS the short-range alternation of the B-site cations was quite apparent in diffuse scattering at (½ ½ ½), whereas it was not apparent in the PDF. PMID:26870378

  3. The Resolved Outflow from 3C 48

    Science.gov (United States)

    Shih, Hsin-Yi; Stockton, Alan

    2014-10-01

    We investigate the properties of the high-velocity outflow driven by the young radio jet of 3C 48, a compact-steep-spectrum source. We use the Space Telescope Imaging Spectrograph on board the Hubble Space Telecope to obtain (1) low-resolution UV and optical spectra and (2) multi-slit medium-resolution spectra of the ionized outflow. With supporting data from ground-based spectrographs, we are able to accurately measure the ratios of diagnostic emission lines such as [O III] λ5007, [O III] λ3727, [N II] λ6548, Hα, Hβ, [Ne V] λ3425, and [Ne III] λ3869. We fit the observed emission-line ratios using a range of ionization models, powered by active galactic nucleus (AGN) radiation and shocks, produced by the MAPPINGS code. We have determined that AGN radiation is likely the dominant ionization source. The outflow's density is estimated to be in the range n = 103-104 cm-3, the mass is ~6 × 106 M ⊙, and the metallicity is likely equal to or higher than solar. Compared with the typical outflows associated with more evolved radio jets, this young outflow is denser, less massive, and more metal rich. Multi-slit observations allow us to construct a two-dimensional velocity map of the outflow that shows a wide range of velocities with distinct velocity components, suggesting a wide-angle clumpy outflow. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-11574. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Some of the

  4. Spatio-temporal variability of CO and O3 in Hyderabad (17°N, 78°E, central India, based on MOZAIC and TES observations and WRF-Chem and MOZART-4 models

    Directory of Open Access Journals (Sweden)

    Varun Sheel

    2016-05-01

    Full Text Available This article is based on the study of the seasonal and interannual variability of carbon monoxide (CO and ozone (O3 at different altitudes of the troposphere over Hyderabad, India, during 2006–2010 using Measurement of OZone and water vapour by Airbus In-Service Aircraft (MOZAIC and observation from Tropospheric Emission Spectrometer (TES aboard NASA's Aura satellite. The MOZAIC observations show maximum seasonal variability in both CO and O3 during winter and pre-monsoon season, with CO in the range (100–200±13 ppbv and O3 in the range (50–70±9 ppbv. The time-series of MOZAIC data shows a significant increase of 4.2±1.3 % in the surface CO and 6.7±1.3 % in the surface O3 during 2006–2010 in Hyderabad. From MOZAIC observations, we identify CO and O3 profiles that are anomalous with respect to the monthly mean and compare those with Weather Research Forecast model coupled with Chemistry (WRF-Chem and Model for OZone and Related Tracers, version 4 profiles for the same day. The anomalous profiles of WRF-Chem are simulated using three convection schemes. The goodness of comparison depends on the convection scheme and the altitude region of the troposphere.

  5. Crystal defects and related stress in Y2O3 thin films: Origin, modeling, and consequence on the stability of the C-type structure

    International Nuclear Information System (INIS)

    Lacroix, Bertrand; Paumier, Fabien; Gaboriaud, Rolly J.

    2011-01-01

    We study the impact that the crystal defects have on the C-type structure of rare earth sesquioxide thin films grown by ion-beam sputtering, through the example of Y 2 O 3 . By monitoring the energy of the argon beam used in the sputter deposition process (between 600 and 1200 eV), we show that it is possible to control the microstructure (defects concentration, stress state and phase) in the oxide layer. Two main types of defects, ascribed to the 'atomic peening effect', are evidenced by high-resolution transmission electron microscopy, Rutherford backscattering spectroscopy, and nuclear reaction analysis experiments: anti-Frenkel pairs, leading to a disorder on the oxygen-vacancy network, and oxygen-vacancy dislocations loops, to accommodate the strong nonstoichiometry. From a macroscopic measurement of the residual stresses in the as-deposited and the annealed layers, through x-ray diffraction and the sin 2 Ψ method, we have modeled the related stress state using an enhanced triaxial stress model. In the as-grown films, we evidence the coexistence of a biaxial and a hydrostatic stress, due to inclusions of atomic size defects. Quantitative information of the concentration and the nature of each type of defect (size effect) have also been determined, in good agreement with experiments. Interestingly, in the most energetic growth conditions corresponding to the highest degree of disorder on the oxygen-vacancy network and to the highest stress field in the film, we demonstrate that it is possible to stabilize an unexpected and metastable non equilibrium fluorite-like phase (X-type).

  6. Atomistic Modeling of Cation Diffusion in Transition Metal Perovskites La1-xSrxMnO3+/-δfor Solid Oxide Fuel Cell Cathodes Applications

    Science.gov (United States)

    Lee, Yueh-Lin; Duan, Yuhua; Morgan, Dane; Sorescu, Dan; Abernathy, Harry

    Cation diffusion in La1-xSrxMnO3+/-δ (LSM) and in related perovskite materials play an important role in controlling long term performance and stability of solid oxide fuel cell (SOFCs) cathodes. Due to sluggish rates of cation diffusion and complex coupling between defect chemistry and cation diffusion pathways, currently there is still lack of quantitative theoretical model predictions on cation diffusivity vs. T and P(O2) to describe experimental cation tracer diffusivities. In this work, based on ab initio modeling of LSM defect chemistry and migration barriers of the possible cation diffusion pathways, we assess the rates of A-site and B-site cation diffusion in a wide range of T and P(O2) at x =0.0 and 0.2 for SOFC applications. We demonstrate the active cation diffusion pathways in LSM involve cation defect clusters as cation transport carriers, where reduction in the cation migration barriers, which are governed by the steric effect associated with the metal-oxygen cage in the perovskite lattice, is much greater than the penalty of repulsive interaction in the A-site and B-site cation vacancy clusters, leading to higher cation diffusion rates as compared to those of single cation vacancy hopping mechanisms. The predicted Mn and La/Sr cation self-diffusion coefficients of LSM at at x =0.0 and 0.2 along with their 1/T and P(O2) dependences, are in good agreement with the experimental tracer diffusion coefficients.

  7. Asian dust outflow in the PBL and free atmosphere retrieved by NASA CALIPSO and an assimilated dust transport model

    OpenAIRE

    Y. Hara; K. Yumimoto; I. Uno; A. Shimizu; N. Sugimoto; Z. Liu; D. M. Winker

    2009-01-01

    International audience; Three-dimensional structures of Asian dust transport in the planetary boundary layer (PBL) and free atmosphere occurring successively during the end of May 2007 were clarified using results of space-borne backscatter lidar, Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), and results simulated using a data-assimilated version of a dust transport model (RC4) based on a ground-based NIES lidar network. Assimilated results mitigated overestimation of dust concen...

  8. Molecular outflows in protostellar evolution

    International Nuclear Information System (INIS)

    Fukui, Y.; Iwata, T.; Mizuno, A.; Ogawa, H.; Kawabata, K.; Sugitani, K.

    1989-01-01

    Molecular outflow is an energetic mass-ejection phenomenon associated with very early stage of stellar evolution. The large kinetic energy involved in the phenomenon indicates that outflow may play an essential role in the process of star formation, particularly by extracting angular momentum. Most of the previous searches have been strongly biased toward optical or near-infrared signposts of star formation. They are not able, therefore, to provide the complete database necessary for a statistical study of the evolutionary status of molecular outflow. To overcome this difficulty, it is of vital importance to make an unbiased search of single molecular clouds for molecular outflows; here we report the final result of such a survey of the Lynds 1641 dark cloud. We show that molecular outflows are characterized by a total luminosity significantly greater than that of T Tauri stars. This indicates that molecular outflow corresponds to the main accretion phase of protostellar evolution, in which the luminosity excess is due to the gravitational energy released by dynamical mass accretion onto the protostellar core. (author)

  9. Modeling transverse heating and outflow of ionospheric ions from the dayside cusp/cleft. 1 A parametric study

    Directory of Open Access Journals (Sweden)

    M. Bouhram

    2003-08-01

    Full Text Available The transport patterns of non-thermal H + and O + field-aligned flows from the dayside cusp/cleft, associated with transverse heating by means of wave-particle interactions and in combination with the poleward motion due to the magnetospheric convection are investigated. This has been accomplished by developing a steady-state, two-dimensional, trajectory-based code. The ion heating is modelled by means of a Monte Carlo technique, via the process of ion cyclotron resonance (ICR, with the electromagnetic left-hand circular polarized component of a broad-band, extremely low-frequency (BBELF turbulence. The altitude dependence of ICR heating from 1000 km to 3 Earth radii (RE is modelled by a power law spectrum, with an index a, and a parameter w0 that is proportional to the spectral density at a referenced gyrofrequency. Because of the finite latitudinal extent of the cusp/cleft, the incorporation of the horizontal convection drift leads to a maximum residence time tD of the ions when being energized. A large set of simulations has been computed so as to study the transport patterns of the H + and O + bulk parameters as a function of tD , a, and w0. Residence time effects are significant in O + density patterns while negligible for H +. When comparing the results with analytical one-dimensional theories (Chang et al., 1986; Crew et al., 1990, we find that mean ion energies and pitch angles at the poleward edge of the heating region are slightly influenced by tD and may be used as a probe of ICR parameters ( a, w0. Conversely, poleward of the heating region, upward velocity and mean energy dispersive patterns depend mainly on tD (e.g. the magnitude of the convection drift with latitudinal profiles varying versus tD . In short, the main conclusion of the paper is that any triplet (tD , a, w0 leads to a unique transport-pattern feature of ion flows associated with a cusp/cleft ionospheric source. In a companion paper, by using high-altitude (1.5–3 RE

  10. Modeling transverse heating and outflow of ionospheric ions from the dayside cusp/cleft. 1 A parametric study

    Directory of Open Access Journals (Sweden)

    M. Bouhram

    Full Text Available The transport patterns of non-thermal H + and O + field-aligned flows from the dayside cusp/cleft, associated with transverse heating by means of wave-particle interactions and in combination with the poleward motion due to the magnetospheric convection are investigated. This has been accomplished by developing a steady-state, two-dimensional, trajectory-based code. The ion heating is modelled by means of a Monte Carlo technique, via the process of ion cyclotron resonance (ICR, with the electromagnetic left-hand circular polarized component of a broad-band, extremely low-frequency (BBELF turbulence. The altitude dependence of ICR heating from 1000 km to 3 Earth radii (RE is modelled by a power law spectrum, with an index a, and a parameter w0 that is proportional to the spectral density at a referenced gyrofrequency. Because of the finite latitudinal extent of the cusp/cleft, the incorporation of the horizontal convection drift leads to a maximum residence time tD of the ions when being energized. A large set of simulations has been computed so as to study the transport patterns of the H + and O + bulk parameters as a function of tD , a, and w0. Residence time effects are significant in O + density patterns while negligible for H +. When comparing the results with analytical one-dimensional theories (Chang et al., 1986; Crew et al., 1990, we find that mean ion energies and pitch angles at the poleward edge of the heating region are slightly influenced by tD and may be used as a probe of ICR parameters ( a, w0. Conversely, poleward of the heating region, upward velocity and mean energy dispersive patterns depend mainly on tD (e.g. the magnitude of the convection drift with latitudinal profiles varying versus

  11. Density diagnostics of ionized outflows in active galacitc nuclei

    Science.gov (United States)

    Mao, J.; Kaastra, J.; Mehdipour, M.; Raassen, T.; Gu, L.

    2017-10-01

    Ionized outflows in Active Galactic Nuclei are thought to influence their nuclear and local galactic environment. However, the distance of outflows with respect to the central engine is poorly constrained, which limits our understanding of the kinetic power by the outflows. Therefore, the impact of AGN outflows on their host galaxies is uncertain. Given the density of the outflows, their distance can be immediately obtained by the definition of the ionization parameter. Here we carry out a theoretical study of density diagnostics of AGN outflows using absorption lines from metastable levels in Be-like to F-like ions. With the new self-consistent photoionization model (PION) in the SPEX code, we are able to calculate ground and metastable level populations. This enable us to determine under what physical conditions these levels are significantly populated. We then identify characteristic transitions from these metastable levels in the X-ray band. Firm detections of absorption lines from such metastable levels are challenging for current grating instruments. The next generation of spectrometers like X-IFU onboard Athena will certainly identify the presence/absence of these density- sensitive absorption lines, thus tightly constraining the location and the kinetic power of AGN outflows.

  12. Methane partial oxidation over a LaCr0.85Ru0.15O3 catalyst : Characterization, activity tests and kinetic modeling

    NARCIS (Netherlands)

    Melchiori, T.; Di Felice, L.; Mota, N.; Navarro, R.M.; Fierro, J.L.G.; Sint Annaland, van M.; Gallucci, F.

    2014-01-01

    A new LaCr0.85Ru0.15O3 perovskite-type catalyst for CH4 partial oxidation with a high activity and selectivity for syngas with good thermal stability and resistance against coking has been developed. In this paper, the catalyst preparation method, catalyst characterization, results of catalytic

  13. A New Look at Speeding Outflows

    Science.gov (United States)

    Kohler, Susanna

    2018-02-01

    of the same outflow a UFO in quasar PG 1211+143 in both X-rays and in ultraviolet.Danehkar and collaborators found absorption lines in both sets of data revealing an outflow moving at 17,000 km/s (for reference, thats 5.6% of the speed of light, and more than 1,500 times faster than Elon Musks roadster will be traveling at its maximum speed in the orbit it was launched onto yesterday by the Falcon Heavy). Having the information both from the X-ray and the ultraviolet data provides the opportunity to better asses the UFOs physical characteristics.The X-ray spectrum for PG 1211+143 was obtained by Chandra HETGS (top); the ultraviolet spectrum was obtained by HST-COS G130M (bottom). [Adapted from Danehkar et al. 2018]A Link Between Black Holes and Galaxies?The authors use models of the data to demonstrate the plausibility of a scenario in which a shock driven by the radio jet gives rise to the fast bulk outflows detected in the X-ray and ultraviolet spectra.They also estimate the impact that the outflows might have on the AGNs host galaxy, demonstrating that the energy injected into the galaxy could be somewhere between 0.02% and 0.6% of the AGNs total luminosity. At the higher end of this range, this could have an evolutionary impact on the host galaxy, suggesting a possible link between the black holes behavior and how its host galaxy evolves.In order to draw definitive conclusions, we will need higher-resolution observations that can determine the total size and extent of these outflows. For that, we may need to wait for 2023, when a proposed X-ray spectrometer that might fit the bill, Arcus, may be launched.CitationAshkbiz Danehkar et al 2018 ApJ 853 165. doi:10.3847/1538-4357/aaa427

  14. Spray pyrolysis synthesis of γ-Al_2O_3 supported metal and metal phosphide catalysts and their activity in the hydrodeoxygenation of a bio-oil model compound

    International Nuclear Information System (INIS)

    Ly, Hoang Vu; Im, Kyungmin; Go, Youngchae; Galiwango, Emmanuel; Kim, Seung-Soo; Kim, Jinsoo; Choi, Jae Hyung; Woo, Hee Chul

    2016-01-01

    Highlights: • Spherical γ-Al_2O_3 supported metal and metal phosphide catalysts were synthesized by spray pyrolysis method. • Hydrodeoxygenation (HDO) of 2-furyl methyl ketone (FMK) was conducted using metal/metal phosphide catalysts. • FMK was converted into 2-allyl furan and methyl cyclohexane. • The highest FMK conversion of 83% was achieved over 10 wt% Ni/γ-Al_2O_3 catalysts at reaction temperature of 400 °C. - Abstract: In this study, spherical γ-Al_2O_3 supported metal and metal phosphide (Ni, Co, Ni_2P and CoP) catalysts were successfully prepared by combining sol-gel and spray pyrolysis methods. First boehmite sol was prepared based on the Yoldas process and then the corresponding metal salts were added to the sol at the desired concentration, followed by spray pyrolysis of the mixed solution. As the well-mixed solution was transformed to spherical γ-Al_2O_3 supported metal and metal phosphide catalysts during spray pyrolysis process, the metal species were uniformly distributed in the mesoporous γ-Al_2O_3 supports. The product catalysts were investigated under different conditions for hydrodeoxygenation of bio-oil model compound, 2-furyl methyl ketone (FMK), which is the main component of the bio-oil product from pyrolysis of Saccharina japonica. Among the investigated catalysts, the 10 wt% Ni/γ-Al_2O_3 catalyst after calcination at 800 °C showed the highest FMK conversion of 83.02% at the reaction temperature of 400 °C. The gas and liquid products were analyzed by gas chromatography (GC) with TCD/FID detectors and GC–MS, respectively, to determine the product compositions.

  15. Character and dynamics of the Red Sea and Persian Gulf outflows

    Science.gov (United States)

    Bower, Amy S.; Hunt, Heather D.; Price, James F.

    2000-03-01

    Historical hydrographic data and a numerical plume model are used to investigate the initial transformation, dynamics, and spreading pathways of Red Sea and Persian Gulf outflow waters where they enter the Indian Ocean. The annual mean transport of these outflows is relatively small (outflows in that they flow over very shallow sills (depth Red Sea outflow exhibits strong seasonal variability in transport. The four main results of this study are as follows. First, on the basis of observed temperature-salinity (T-S) characteristics of the outflow source and product waters we estimate that the Red Sea and Persian Gulf outflows are diluted by factors of ˜2.5 and 4, respectively, as they descend from sill depth to their depth of neutral buoyancy. The high-dilution factor for the Persian Gulf outflow results from the combined effects of large initial density difference between the outflow source water and oceanic water and low outflow transport. Second, the combination of low latitude and low outflow transport (and associated low outflow thickness) results in Ekman numbers for both outflows that are O(1). This indicates that they should be thought of as frictional density currents modified by rotation rather than geostrophic density currents modified by friction. Third, different mixing histories along the two channels that direct Red Sea outflow water into the open ocean result in product waters with significantly different densities, which probably contributes to the multilayered structure of the Red Sea product waters. In both outflows, seasonal variations in source water and oceanic properties have some effect on the T-S of the product waters, but they have only a minor impact on equilibrium depth. Fourth, product waters from both outflows are advected away from the sill region in narrow boundary currents, at least during part of the year. At other times, the product water appears more in isolated patches.

  16. Nanoscale formation of new solid-state compounds by topochemical effects: The interfacial reactions ZnO with Al2O3 as a model system

    International Nuclear Information System (INIS)

    Pin, Sonia; Ghigna, Paolo; Spinolo, Giorgio; Quartarone, Eliana; Mustarelli, Piercarlo; D'Acapito, Francesco; Migliori, Andrea; Calestani, Gianluca

    2009-01-01

    The chemical reactivity of thin layers (ca. 10 nm thick) of ZnO deposited onto differently oriented Al 2 O 3 single crystals has been investigated by means of atomic force microscopy inspections and X-ray absorption spectroscopy at the Zn-K edge. The (0001) ZnO -parallel (112-bar0) sapphire interface yields the ZnAl 2 O 4 spinel and a quite stable film morphology. Instead, the (112-bar0) ZnO -parallel (11-bar02) sapphire and (0001) ZnO -parallel (0001) sapphire interfaces give origin to a new compound (or, possibly, even two new compounds), whose chemical nature is most likely that of a ZnO/Al 2 O 3 phase, with still unknown composition and crystal structure. In addition, in the last two cases, films collapse into prismatic twins of ca. 1 μm in dimension. These experimental findings demonstrate that in a solid-state reaction, the topotactical relationships between the reacting solids are of crucial importance not only in determining the kinetic and mechanisms of the process in its early stages, but even the chemical nature of the product. - Graphical abstract: EXAFS Fourier transforms and morphology of different reactive interfaces between ZnO and Al 2 O 3 .

  17. Knowledge Outflows from Foreign Subsidiaries

    DEFF Research Database (Denmark)

    Perri, Alessandra; Andersson, Ulf

    This paper analyzes the MNC subsidiaries’ trade-off between the need for knowledge creation and the need for knowledge protection, and relates it to the extent of knowledge outflows generated within the host location. Combining research in International Business with Social Theory, we find...... the value of the subsidiary’s knowledge stock is very high, the need for knowledge protection restrains reciprocity mechanisms in knowledge exchanges, thus reducing the extent of knowledge outflows to the host location. This study contributes to the literature on the firm-level antecedents of FDI...... that subsidiaries that extensively draw on external knowledge sources are also more likely to generate knowledge outflows to local firms. We argue that this may be explained by the subsidiaries’ willingness to build the trust that facilitates the establishment of reciprocal knowledge linkages. However, when...

  18. Molecular Outflows: Explosive versus Protostellar

    Energy Technology Data Exchange (ETDEWEB)

    Zapata, Luis A.; Rodríguez, Luis F.; Palau, Aina; Loinard, Laurent [Instituto de Radioastronomía y Astrofísica, UNAM, Apdo. Postal 3-72 (Xangari), 58089 Morelia, Michoacán, México (Mexico); Schmid-Burgk, Johannes [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121, Bonn (Germany)

    2017-02-10

    With the recent recognition of a second, distinctive class of molecular outflows, namely the explosive ones not directly connected to the accretion–ejection process in star formation, a juxtaposition of the morphological and kinematic properties of both classes is warranted. By applying the same method used in Zapata et al., and using {sup 12}CO( J = 2-1) archival data from the Submillimeter Array, we contrast two well-known explosive objects, Orion KL and DR21, to HH 211 and DG Tau B, two flows representative of classical low-mass protostellar outflows. At the moment, there are only two well-established cases of explosive outflows, but with the full availability of ALMA we expect that more examples will be found in the near future. The main results are the largely different spatial distributions of the explosive flows, consisting of numerous narrow straight filament-like ejections with different orientations and in almost an isotropic configuration, the redshifted with respect to the blueshifted components of the flows (maximally separated in protostellar, largely overlapping in explosive outflows), the very-well-defined Hubble flow-like increase of velocity with distance from the origin in the explosive filaments versus the mostly non-organized CO velocity field in protostellar objects, and huge inequalities in mass, momentum, and energy of the two classes, at least for the case of low-mass flows. Finally, all the molecular filaments in the explosive outflows point back to approximately a central position (i.e., the place where its “exciting source” was located), contrary to the bulk of the molecular material within the protostellar outflows.

  19. Theory of the 4d → 2p X-ray emission spectroscopy in Ce2O3, Pr2O3 and Dy2O3

    International Nuclear Information System (INIS)

    Tanaka, Satoshi; Ogasawara, Haruhiko; Okada, Kozo; Kotani, Akio.

    1995-01-01

    The 4d → 2p X-ray emission spectra (XES) of Ce 2 O 3 , Pr 2 O 3 and Dy 2 O 3 have been calculated with an impurity Anderson model with the full multiplet couplings, following the Kramers-Heisenberg formula in the second order optical process. Experimental results have been well reproduced with this model by using a constant value for the 4d core hole lifetime damping Γ(4d) in the case of Ce 2 O 3 and Pr 2 O 3 , while in the case of Dy 2 O 3 it is necessary to take into account the term dependence of Γ(4d), which is consistent with the previous theoretical analyses of 4d X-ray photoemission spectra. It was also shown that both the spin-orbit couplings of the 4d core level in the final state and the 4f level in the initial state are key factors to cause the branching ratio in the L γ line larger than that in the L β line. The phase matching of the wave functions between the intermediate and final states smears out the hybridization effect in the 4d → 2p XES in Ce 2 O 3 and Pr 2 O 3 . (author)

  20. Mechanisms of charge transfer and redistribution in LaAlO3/SrTiO3 revealed by high-energy optical conductivity.

    Science.gov (United States)

    Asmara, T C; Annadi, A; Santoso, I; Gogoi, P K; Kotlov, A; Omer, H M; Motapothula, M; Breese, M B H; Rübhausen, M; Venkatesan, T; Ariando; Rusydi, A

    2014-04-14

    In condensed matter physics the quasi two-dimensional electron gas at the interface of two different insulators, polar LaAlO3 on nonpolar SrTiO3 (LaAlO3/SrTiO3) is a spectacular and surprising observation. This phenomenon is LaAlO3 film thickness dependent and may be explained by the polarization catastrophe model, in which a charge transfer of 0.5e(-) from the LaAlO3 film into the LaAlO3/SrTiO3 interface is expected. Here we show that in conducting samples (≥ 4 unit cells of LaAlO3) there is indeed a ~0.5e(-) transfer from LaAlO3 into the LaAlO3/SrTiO3 interface by studying the optical conductivity in a broad energy range (0.5-35 eV). Surprisingly, in insulating samples (≤ 3 unit cells of LaAlO3) a redistribution of charges within the polar LaAlO3 sublayers (from AlO2 to LaO) as large as ~0.5e(-) is observed, with no charge transfer into the interface. Hence, our results reveal the different mechanisms for the polarization catastrophe compensation in insulating and conducting LaAlO3/SrTiO3 interfaces.

  1. Study of the solid-solid surface adsorption of Eu2O3 on various Al2O3 supports

    International Nuclear Information System (INIS)

    Liu Rongchuan; Yu Zhi; Zhou Yuan; Yoshitake Yamazaki

    1997-12-01

    Solid-solid surface interactions of Eu 2 O 3 on various oxide substrates are investigated with X-ray and Moessbauer experiments. The results indicate that the interaction of Eu 2 O 3 on the complex support differs from that having simple support. An incorporation model is used to explain how Eu 2 O 3 disperses onto the surface of γ-alumina or η-alumina

  2. Part I: A Comparative Thermal Aging Study on the Regenerability of Rh/Al2O3 and Rh/CexOy-ZrO2 as Model Catalysts for Automotive Three Way Catalysts

    Directory of Open Access Journals (Sweden)

    Qinghe Zheng

    2015-10-01

    Full Text Available The rhodium (Rh component in automotive three way catalysts (TWC experiences severe thermal deactivation during fuel shutoff, an engine mode (e.g., at downhill coasting used for enhancing fuel economy. In a subsequent switch to a slightly fuel rich condition, in situ catalyst regeneration is accomplished by reduction with H2 generated through steam reforming catalyzed by Rh0 sites. The present work reports the effects of the two processes on the activity and properties of 0.5% Rh/Al2O3 and 0.5% Rh/CexOy-ZrO2 (CZO as model catalysts for Rh-TWC. A very brief introduction of three way catalysts and system considerations is also given. During simulated fuel shutoff, catalyst deactivation is accelerated with increasing aging temperature from 800 °C to 1050 °C. Rh on a CZO support experiences less deactivation and faster regeneration than Rh on Al2O3. Catalyst characterization techniques including BET surface area, CO chemisorption, TPR, and XPS measurements were applied to examine the roles of metal-support interactions in each catalyst system. For Rh/Al2O3, strong metal-support interactions with the formation of stable rhodium aluminate (Rh(AlO2y complex dominates in fuel shutoff, leading to more difficult catalyst regeneration. For Rh/CZO, Rh sites were partially oxidized to Rh2O3 and were relatively easy to be reduced to active Rh0 during regeneration.

  3. Inferring Polar Ion Outflows from Topside Ionograms

    Science.gov (United States)

    Sojka, J. J.; Rice, D. D.; Eccles, V.; Schunk, R. W.; David, M.; Benson, R. F.; James, H. G.

    2017-12-01

    The high-latitude topside ionosphere is dominated by O+ ions from the F-region peak around 300 km to over 1000 km altitude. The O+ profile shape provides information on the thermal structure, field aligned plasma dynamics, and outflows into the magnetosphere. Topside electron density profiles (EDP) are either obtained from topside sounders or Incoherent Scatter Radars. There is a large archive of topside sounder ionograms and hand scaled EDPs from the Alouette and ISIS satellites between 1962 and 1990. Recent NASA data enhancement efforts have augmented these EDP archives by producing digital topside ionograms both from the 7-track analog telemetry tapes and from 35 mm topside film ionograms. Rice et al [2017] in their 35 mm ionogram recovery emphasized high latitude ionograms taken during disturbed conditions. The figure below contrasts ISIS-II EDPs extracted from 35 mm films before and during a major storm (Dst -200nT) on 9 April 1972 (left panel: quiet period before the storm; right panel: during the peak of the storm). Both satellite passes used for these EDPs were centered on the Resolute Bay location that in 1972 was close to the magnetic pole. They begin at auroral latitudes around 2100 MLT and end on the dayside around 0900MLT. We will present results of how ionospheric models replicate both the quiet and disturbed conditions shown in the figure. Three types of models will be contrasted: an empirical ionosphere (IRI), a physics based ionospheric model (TDIM), and a fluid-based polar-wind model (PW). During the storm pass, when it is expected that substantial heating is present, the ISIS-II topside EDPs provide severe constraints on the usage of these models. These constraints enable estimates of the outflow fluxes as well as the heating that has occurred. The comparisons with the empirical model establish how well the pre-storm topside is modeled and identifies the challenges as the storm magnitude increases. The physics-based TDIM does have storm drivers

  4. The Mass Outflow Rate of the Milky Way

    Science.gov (United States)

    Fox, Andrew

    2017-08-01

    The balance between gaseous inflow and outflow regulates star formation in spiral galaxies. This paradigm can be tested in the Milky Way, but whereas the star formation rate and inflow rate have both been measured, the outflow rate has not. We propose an archival COS program to determine the Galactic outflow rate in cool gas ( 10^4 K) by surveying UV absorption line high-velocity clouds (HVCs). This project will make use of the newly updated Hubble Spectroscopic Legacy Archive, which contains a uniformly reduced sample of 233 COS G130M spectra of background AGN. The outflow rate will be determined by (1) searching for redshifted HVCs; (2) modeling the clouds with photoionization simulations to determine their masses and physical properties; (3) combining the cloud masses with their velocities and distances. We will measure how the outflow is distributed spatially across the sky, calculate its mass loading factor, and compare the line profiles to synthetic spectra extracted from new hydrodynamic simulations. The distribution of HVC velocities will inform us what fraction of the outflowing clouds will escape the halo and what fraction will circulate back to the disk, to better understand how and where gas enters and exits the Milky Way.

  5. PROTOSTELLAR OUTFLOWS IN L1340

    Energy Technology Data Exchange (ETDEWEB)

    Walawender, Josh [W. M. Keck Observatory, 65-1120 Mamalahoa Hwy, Kamuela, HI 96743 (United States); Wolf-Chase, Grace [Astronomy Department, Adler Planetarium, 1300 South Lake Shore Drive, Chicago, IL 60605 (United States); Smutko, Michael [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); OLinger-Luscusk, JoAnn [California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125 (United States); Moriarty-Schieven, Gerald, E-mail: jmwalawender@keck.hawaii.edu [National Research Council—Herzberg Astronomy and Astrophysics, 5017 West Saanich Road, Victoria, BC, V9E 2E7 (Canada)

    2016-12-01

    We have searched the L1340 A, B, and C clouds for shocks from protostellar outflows using the H{sub 2} 2.122 μ m near-infrared line as a shock tracer. Substantial outflow activity has been found in each of the three regions of the cloud (L1340 A, L1340 B, and L1340 C). We find 42 distinct shock complexes (16 in L1340 A, 11 in L1340 B, and 15 in L1340 C). We were able to link 17 of those shock complexes into 12 distinct outflows and identify candidate source stars for each. We examine the properties ( A {sub V}, T {sub bol}, and L {sub bol}) of the source protostars and compare them to the properties of the general population of Class 0/I and flat spectral energy distribution protostars and find that there is an indication, albeit at low statistical significance, that the outflow-driving protostars are drawn from a population with lower A {sub V}, higher L {sub bol}, and lower T {sub bol} than the general population of protostars.

  6. Nanostructured Fe2O3/Al2O3 Adsorbent for removal of As (V from water

    Directory of Open Access Journals (Sweden)

    Faranak Akhlaghian

    2017-04-01

    Full Text Available The presence of arsenate in drinking water causes adverse health effects including skin lesions, diabetes, cancer, damage to the nervous system, and cardiovascular diseases. Therefore, the removal of As (V from water is necessary. In this work, nanostructured adsorbent Fe2O3/Al2O3 was synthesized via the sol-gel method and applied to remove arsenate from polluted waters. First, the Fe2O3 load of the adsorbent was optimized. The Fe2O3/Al2O3 adsorbent was characterized by means of XRF, XRD, ASAP, and SEM techniques. The effects of the operating conditions of the batch process of As (V adsorption such as pH, adsorbent dose, contact time, and initial concentration of As (V solution were studied, and optimized. The thermodynamic study of the process showed that arsenate adsorption was endothermic. The kinetic model corresponded to the pseudo-second-order model. The Langmuir adsorption isotherm was better fitted to the experimental data. The Fe2O3/Al2O3 adsorbent was immobilized on leca granules and applied for As (V adsorption. The results showed that the immobilization of Fe2O3/Al2O3 on leca particles improved the As (V removal efficiency.

  7. Voltage-controlled ferromagnetism and magnetoresistance in LaCoO3/SrTiO3 heterostructures

    International Nuclear Information System (INIS)

    Hu, Chengqing; Park, Keun Woo; Yu, Edward T.; Posadas, Agham; Demkov, Alexander A.; Jordan-Sweet, Jean L.

    2013-01-01

    A LaCoO 3 /SrTiO 3 heterostructure grown on Si (001) is shown to provide electrically switchable ferromagnetism, a large, electrically tunable magnetoresistance, and a vehicle for achieving and probing electrical control over ferromagnetic behavior at submicron dimensions. Fabrication of devices in a field-effect transistor geometry enables application of a gate bias voltage that modulates strain in the heterostructure via the converse piezoelectric effect in SrTiO 3 , leading to an artificial inverse magnetoelectric effect arising from the dependence of ferromagnetism in the LaCoO 3 layer on strain. Below the Curie temperature of the LaCoO 3 layer, this effect leads to modulation of resistance in LaCoO 3 as large as 100%, and magnetoresistance as high as 80%, both of which arise from carrier scattering at ferromagnetic-nonmagnetic interfaces in LaCoO 3 . Finite-element numerical modeling of electric field distributions is used to explain the dependence of carrier transport behavior on gate contact geometry, and a Valet-Fert transport model enables determination of spin polarization in the LaCoO 3 layer. Piezoresponse force microscopy is used to confirm the existence of piezoelectric response in SrTiO 3 grown on Si (001). It is also shown that this structure offers the possibility of achieving exclusive-NOR logic functionality within a single device

  8. Emission of Gas and Al2O3 Smoke in Gas-Al Particle Deflagration: Experiments and Emission Modeling for Explosive Fireballs

    Science.gov (United States)

    Ranc-Darbord, Isabelle; Baudin, Gérard; Genetier, Marc; Ramel, David; Vasseur, Pierre; Legrand, Julien; Pina, Vincent

    2018-03-01

    Emission of gas and Al2O3 smoke within the deflagration of H2{-}O2-{N2{-}CO2}-Al particles has been studied in a closed combustion chamber at pressures of up to 18 bar and at gas temperatures of up to 3700 K. Measurements of radiance intensity were taken using a five wavelength pyrometer (0.660 μ m, 0.850 μ m, 1.083 μ m, 1.260 μ m, 1.481 μ m) and a grating spectrometer in the range (4.10 μ m to 4.30 μ m). In order to characterize the aluminum oxide smoke size and temperature, an inversion method has been developed based on the radiation transfer equation and using pyrometer measurements and thermochemical calculations of Al2O3 smoke volume fractions. Temperatures in combustion gas have been determined using a method based on the assumed blackbody head of the 4.26 μ m CO2 emission line and on its spectral shift with pressure and temperature. For validation purpose, this method has been applied to measurements obtained when calibrated alumina particles are injected in a combustion chamber prior to gaseous deflagrations. This mathematical inversion method was developed to investigate explosive fireballs.

  9. Prospects for Engineering Thermoelectric Properties in La1/3NbO3 Ceramics Revealed via Atomic-Level Characterization and Modeling.

    Science.gov (United States)

    Kepaptsoglou, Demie; Baran, Jakub D; Azough, Feridoon; Ekren, Dursun; Srivastava, Deepanshu; Molinari, Marco; Parker, Stephen C; Ramasse, Quentin M; Freer, Robert

    2018-01-02

    A combination of experimental and computational techniques has been employed to explore the crystal structure and thermoelectric properties of A-site-deficient perovskite La 1/3 NbO 3 ceramics. Crystallographic data from X-ray and electron diffraction confirmed that the room temperature structure is orthorhombic with Cmmm as a space group. Atomically resolved imaging and analysis showed that there are two distinct A sites: one is occupied with La and vacancies, and the second site is fully unoccupied. The diffuse superstructure reflections observed through diffraction techniques are shown to originate from La vacancy ordering. La 1/3 NbO 3 ceramics sintered in air showed promising high-temperature thermoelectric properties with a high Seebeck coefficient of S 1 = -650 to -700 μV/K and a low and temperature-stable thermal conductivity of k = 2-2.2 W/m·K in the temperature range of 300-1000 K. First-principles electronic structure calculations are used to link the temperature dependence of the Seebeck coefficient measured experimentally to the evolution of the density of states with temperature and indicate possible avenues for further optimization through electron doping and control of the A-site occupancies. Moreover, lattice thermal conductivity calculations give insights into the dependence of the thermal conductivity on specific crystallographic directions of the material, which could be exploited via nanostructuring to create high-efficiency compound thermoelectrics.

  10. Negative surface streamers propagating on TiO2 and γ-Al2O3-supported Ag catalysts: ICCD imaging and modeling study

    Science.gov (United States)

    Kim, Hyun-Ha; Teramoto, Yoshiyuki; Ogata, Atsushi; Kang, Woo Seok; Hur, Min; Song, Young-Hoon

    2018-06-01

    Surface streamers propagating on the surface of titanium dioxide (TiO2) and alumina (γ-Al2O3) were studied in negative polarity using intensified charge coupled device (ICCD) imaging and numerical simulation. Detailed time-resolved ICCD images of cathode-directed streamers (CDSs) emanating from a ground electrode are first presented in this report. Instead of primary streamers in positive polarity, only a glow-like discharge appeared in the early stage at the cathode under negative polarity. After this discharge disappeared, a counter-propagating CDS initiated from the ground electrode (anode). Numerical simulation indicated that strong electric fields at the pellet-anode and the formation of positive ion rich local spots were the main reason for the CDS formation near the ground electrode. The maximum velocity was 750 km s‑1 for Ag-supported γ-Al2O3 and 550 km s‑1 for Ag-supported TiO2, respectively. In contrast to the CDS in the gas-phase with a positive polarity, the CDS in a catalyst packed-bed under negative polarity showed more branching and a larger number of streamers in the presence of oxygen than in pure N2.

  11. Study of spinodal decomposition and formation of nc-Al2O3/ZrO2 nanocomposites by combined ab initio density functional theory and thermodynamic modeling

    International Nuclear Information System (INIS)

    Sheng, S.H.; Zhang, R.F.; Veprek, S.

    2011-01-01

    Using ab initio density functional theory, the equilibrium properties, such as the total energy, the molar volume, the bulk modulus and its first derivative, as well as the formation enthalpy of monoclinic ZrO 2 and hexagonal α-Al 2 O 3 phases, were calculated and compared with the published theoretical and experimental data. Based on the good agreement of these data, we calculated the lattice instabilities of hypothetical binary hexagonal Zr 2 O 3 and monoclinic AlO 2 , and the interaction parameters of ternary Zr 1-x Al x O y solid solutions. The binodal and spinodal diagrams were then constructed to predict the possibility of the formation of oxide-based nanocomposites which may display hardness enhancement above that of the solid solutions. It is shown that exponential dependence of the interaction parameter on temperature yields the most reliable results. The system should undergo spinodal phase segregation within the composition range that is relevant for the formation of hard or superhard nanocomposites with high thermal and oxidation stability, which are important for their applications.

  12. Electron correlation in CaRuO3 and SrRuO3

    International Nuclear Information System (INIS)

    Singh, Ravi Shankar; Maiti, Kalobaran

    2005-01-01

    We investigate the role of electron correlation in the electronic structure of 4d transition-metal oxides CaRuO 3 and SrRuO 3 . The photoemission spectra collected at different surface sensitivities reveal qualitatively different surface and bulk electronic structures in these systems. Extracted bulk spectra could be simulated using first principle approaches consistently with their thermodynamic parameters within the same model. The estimated electron correlation strength (U/W ∼ 0.2) is significantly weak as expected in 4d systems and resolves the long-standing issue that arose due to the prediction of large U/W similar to 3d systems. (author)

  13. Electrical transport and temperature coefficient of resistance in polycrystalline La0.7−xAgxCa0.3MnO3 pellets: Analysis in terms of a phase coexistence transport model and phase separation model

    International Nuclear Information System (INIS)

    Phong, P.T.; Nguyen, L.H.; Manh, D.H.; Phuc, N.X.; Lee, I.-J.

    2013-01-01

    The temperature dependent resistivity and temperature coefficient of resistance of Ag doped La 0.7−x Ag x Ca 0.3 MnO 3 polycrystalline pellets (x=0, 0.05, 0.10, 0.15, and 0.20) are investigated. Ag substitution enhances the conductivity of this system. The Curie temperature also increases from 260 to 283 K with increasing Ag content. Using phase-coexistence transport model and phase separation model, we calculated the resistivity as a function of temperature and the temperature coefficient of resistivity (TCR) behavior. Comparing the calculated maximum TCR, we found that it is related to activation energy, transition temperature, and disorder in doped manganites. The relationship between the proposed TCR behavior and the transport parameters can suggest conditions improving TCR max of doped manganites for the use of the bolometric infrared detectors

  14. Relationship Between Kinetics of Inflow and Outflow as the Basis of a Computer Simulation for Solving Compartmental Models: Example of Electrolyte Transfers in Cardiovascular Tissues

    Energy Technology Data Exchange (ETDEWEB)

    Llaurado, J. G. [Biomedical Engineering Group, Marquette University (United States); Marquette School of Medicine, Milwaukee (United States); Nuclear Medicine Service of Veterans Administration Center, Wood, WI (United States)

    1971-02-15

    A method commonly used for the study of the distribution of a substance among the different spaces ol a biological tissue is the continuous washout (outflow) and isotope counting of fragments of tissue previously incubated with a tracer. A first order kinetics compartmental system can be postulated and characterized by the transport rates (k) at which the substance of interest moves across its different compartments. Direct solution from the outflow data requires knowledge of the initial conditions for, or to have access for measurements in, each compartment. This cannot be fulfilled in most biological problems. In the course of studying {sup 22}Na distribution in segments of arteries a digital computer simulation approach was developed to solve the system. In the belief that the approach transcends this particular application, its mathematical basis is herein presented: the movement of radioactive tracer obeys Divides dq/d Divides = - Divides k Divides Divides q Divides + Divides r Divides (1) where |q| is a vector of response functions for each compartment, |k] is a square matrix of transport rate constants and |r| is a vector of input rates to the system. Solution of Eq. 1 is Divides q Divides = e{sup - Divides k Divides t} {integral}{sub 0}{sup t} e{sup Divides k Divides t} Divides r Divides dt + e{sup - Divides k Divides t} Divides q{sub 0} Divides (2) (i) For an inflow experiment, with 0 initial conditions and a constant unit input rate |r{sub u}| Divides q Divides = ( Divides I Divides - e{sup - Divides k Divides t}) Divides k Divides {sup -1} Divides r{sub u} Divides (3) as t --> {infinity}, Divides q{sub {infinity}} Divides = Divides k Divides {sup -1} Divides r{sub u} Divides , which replaced in Eq. 3, Divides q Divides = Divides q{sub {infinity}} Divides -e{sup - Divides k Divides t} Divides q{sub {infinity}} Divides (4) (ii) For an outflow experiment Divides r Divides = 0 and Eq. 2 becomes Divides q Divides = e{sup - Divides k Divides t} Divides q{sub 0

  15. Assessment of Ga2O3 technology

    Science.gov (United States)

    2016-09-15

    this article has given the emerging technology of GaN a valuable push in term of encouragement to stay with it while the painful technology development...Ga2O3 α-Ga2O3 β-Ga2O3 β-Ga2O3 β-Ga2O3 poly - Ga2O3 β-Ga2O3 Epi-layer Growth Method MBE (ozone) MBE (ozone) MBE (ozone) Mist-CVD MBE (ozone... pains to treat the wafer surface with BCl3 RIE to create charges at the interface. The gate contact was also barely a Schottky contact evidenced by

  16. Iodine-131 monitoring in sewage plant outflow

    International Nuclear Information System (INIS)

    McGowan, D R; Crawley, M T; Pratt, B E; Hinton, P J; Peet, D J

    2014-01-01

    Three different hospital sites (Oxford, Sutton and Guildford) have performed sampling of their local sewage plant outflow to determine levels of radioactivity resulting from iodine-131 patients undergoing radionuclide therapies. It was found that a maximum of 20% of activity discharged from the hospitals was present in the sewage plant final effluent channel. This is significantly below the level predicted by mathematical models in current use. The results further show that abatement systems to reduce public exposure are unlikely to be warranted at hospital sites. (paper)

  17. Cosmic ray driven outflows in an ultraluminous galaxy

    Science.gov (United States)

    Fujita, Akimi; Mac Low, Mordecai-Mark

    2018-06-01

    In models of galaxy formation, feedback driven both by supernova (SN) and active galactic nucleus is not efficient enough to quench star formation in massive galaxies. Models of smaller galaxies have suggested that cosmic rays (CRs) play a major role in expelling material from the star-forming regions by diffusing SN energy to the lower density outskirts. We therefore run gas dynamical simulations of galactic outflows from a galaxy contained in a halo with 5 × 1012 M⊙ that resembles a local ultraluminous galaxy, including both SN thermal energy and a treatment of CRs using the same diffusion approximation as Salem & Bryan. We find that CR pressure drives a low-density bubble beyond the edge of the shell swept up by thermal pressure, but the main bubble driven by SN thermal pressure overtakes it later, which creates a large-scale biconical outflow. CRs diffusing into the disc are unable to entrain its gas in the outflows, yielding a mass-loading rate of only ˜ 0.1 per cent with varied CR diffusion coefficients. We find no significant difference in mass-loading rates in SN-driven outflows with or without CR pressure. Our simulations strongly suggest that it is hard to drive a heavily mass-loaded outflow with CRs from a massive halo potential, although more distributed star formation could lead to a different result.

  18. The outflow speed of the coma of Halley's comet

    International Nuclear Information System (INIS)

    Combi, M.R.

    1989-01-01

    Data concerning the outflow speed of the coma of Comet Halley are studied in relation to a generalization of the coupled pure-gas-dynamic/Monte Carlo model of Combi and Smyth (1988) to include the dusty-gas dynamics of the inner coma. Measurements made by the Giotto neutral-gas spectrometer, IR water observations from the Kuiper Airborne Observatory, and Doppler radio line profiles of HCN and OH are used to examine the radial dependence of the outflow speed, the asymmetry in the outflow speed, and the overall heliocentric distance dependence of the Doppler profiles, respectively. The results suggest that the model makes it possible to understand the gross long-term behavior and radial structure of the dynamics of the cometary coma. 23 refs

  19. Multiphase nanodomains in a strained BaTiO3 film on a GdScO3 substrate

    Science.gov (United States)

    Kobayashi, Shunsuke; Inoue, Kazutoshi; Kato, Takeharu; Ikuhara, Yuichi; Yamamoto, Takahisa

    2018-02-01

    Controlling the crystal structure of ferroelectric materials via epitaxial strain, which is a well-known technique in strain engineering, can lead to the formation of unique domain structures generating non-intrinsic phenomena such as electronic conductivity, photovoltages, and enhanced piezoelectric characteristics. Strained BaTiO3 films are promising ferroelectric materials as theoretical modeling predicts that different domain morphologies can introduce additional properties not observed in conventional BaTiO3 ceramics. To rationally design materials for practical application, a thorough understanding of the formation mechanisms and stabilities of different domain structures in strained BaTiO3 films is required. However, there have been very few experimental reports on this topic, and details about the domain structures in strained BaTiO3 films are currently lacking. In this paper, we report multiphase nanodomains in a strained BaTiO3 film deposited on an orthorhombic GdScO3 substrate. The phase-transition behavior of the strained BaTiO3 film reveals that it contains multiple phases at room temperature; the film first undergoes a phase-transition upon heating at around 550 K, and then a paraelectric phase forms at temperatures above 690 K. A picometer-scale analysis of the Ti ion displacements, using an advanced scanning transmission electron microscopy technique, is used to characterize the complex multiphase nanodomains, providing useful insights into the control of domain structures in BaTiO3 films by applying epitaxial strain.

  20. HNbO3 and HTaO3: new cubic perovskites prepared from LiNbO3 and LiTaO3 via ion exchange

    International Nuclear Information System (INIS)

    Rice, C.E.; Jackel, J.L.

    1982-01-01

    The synthesis of HNbO 3 and HTaO 3 from LiNbO 3 via ion exchange in hot aqueous acid solutions is reported. This reaction is accompanied by a topotactic structural transformation from the rhombohedral LiNbO 3 structure to the cubic perovskite structure; cell constants are a = 3.822(1) angstrom for HNbO 3 and 3.810(2) angstrom for HTaO 3 . These new compounds have been characterized by powder X-ray diffraction, thermogravimetric analysis, and solid-state NMR. They are electronic insulators and have low ionic conductivity. Evidence of partially proton-exchange phases Li/sub 1-x/H/sub x/MO 3 was also seen. The possible significance of this ion exchange reaction for devices using LiNbO 3 or LiTaO 3 is discussed

  1. Simulation of Breach Outflow for Earthfill Dam

    International Nuclear Information System (INIS)

    Razad, Azwin Zailti Abdul; Muda, Rahsidi Sabri; Sidek, Lariyah Mohd; Azia, Intan Shafilah Abdul; Mansor, Faezah Hanum; Yalit, Ruzaimei

    2013-01-01

    Dams have been built for many reasons such as irrigation, hydropower, flood mitigation, and water supply to support development for the benefit of human. However, the huge amount of water stored behind the dam can seriously pose adverse impacts to the downstream community should it be released due to unwanted dam break event. To minimise the potential loss of lives and property damages, a workable Emergency Response Plan is required to be developed. As part of a responsible dam owner and operator, TNB initiated a study on dam breach modelling for Cameron Highlands Hydroelectric Scheme to simulate the potential dam breach for Jor Dam. Prediction of dam breach parameters using the empirical equations of Froehlich and Macdonal-Langridge-Monopolis formed the basis of the modelling, coupled with MIKE 11 software to obtain the breach outflow due to Probable Maximum Flood (PMF). This paper will therefore discuss the model setup, simulation procedure and comparison of the prediction with existing equations.

  2. Two separate outflows in the dual supermassive black hole system NGC 6240.

    Science.gov (United States)

    Müller-Sánchez, F; Nevin, R; Comerford, J M; Davies, R I; Privon, G C; Treister, E

    2018-04-01

    Theoretical models and numerical simulations have established a framework of galaxy evolution in which galaxies merge and create dual supermassive black holes (with separations of one to ten kiloparsecs), which eventually sink into the centre of the merger remnant, emit gravitational waves and coalesce. The merger also triggers star formation and supermassive black hole growth, and gas outflows regulate the stellar content 1-3 . Although this theoretical picture is supported by recent observations of starburst-driven and supermassive black hole-driven outflows 4-6 , it remains unclear how these outflows interact with the interstellar medium. Furthermore, the relative contributions of star formation and black hole activity to galactic feedback remain unknown 7-9 . Here we report observations of dual outflows in the central region of the prototypical merger NGC 6240. We find a black-hole-driven outflow of [O III] to the northeast and a starburst-driven outflow of Hα to the northwest. The orientations and positions of the outflows allow us to isolate them spatially and study their properties independently. We estimate mass outflow rates of 10 and 75 solar masses per year for the Hα bubble and the [O III] cone, respectively. Their combined mass outflow is comparable to the star formation rate 10 , suggesting that negative feedback on star formation is occurring.

  3. Multi-phase outflows as probes of AGN accretion history

    Science.gov (United States)

    Nardini, Emanuele; Zubovas, Kastytis

    2018-05-01

    Powerful outflows with a broad range of properties (such as velocity, ionization, radial scale and mass loss rate) represent a key feature of active galactic nuclei (AGN), even more so since they have been simultaneously revealed also in individual objects. Here we revisit in a simple analytical framework the recent remarkable cases of two ultraluminous infrared quasars, IRAS F11119+3257 and Mrk 231, which allow us to investigate the physical connection between multi-phase AGN outflows across the ladder of distance from the central supermassive black hole (SMBH). We argue that any major deviations from the standard outflow propagation models might encode unique information on the past SMBH accretion history, and briefly discuss how this could help address some controversial aspects of the current picture of AGN feedback.

  4. CORONAL MASS EJECTION INDUCED OUTFLOWS OBSERVED WITH HINODE/EIS

    International Nuclear Information System (INIS)

    Jin, M.; Ding, M. D.; Chen, P. F.; Fang, C.; Imada, S.

    2009-01-01

    We investigate the outflows associated with two halo coronal mass ejections (CMEs) that occurred on 2006 December 13 and 14 in NOAA 10930, using the Hinode/EIS observations. Each CME was accompanied by an EIT wave and coronal dimmings. Dopplergrams in the dimming regions are obtained from the spectra of seven EIS lines. The results show that strong outflows are visible in the dimming regions during the CME eruption at different heights from the lower transition region to the corona. It is found that the velocity is positively correlated with the photospheric magnetic field, as well as the magnitude of the dimming. We estimate the mass loss based on height-dependent EUV dimmings and find it to be smaller than the CME mass derived from white-light observations. The mass difference is attributed partly to the uncertain atmospheric model, and partly to the transition region outflows, which refill the coronal dimmings.

  5. Studies of Eu2O3 - Bi2O3 - B2O3 glasses using Raman and IR spectroscopy

    International Nuclear Information System (INIS)

    Pop, Lidia; Culea, Eugen N.; Bratu, I.

    2004-01-01

    The bismuth borate (3Bi 2 O 3 ·B 2 O 3 ) glasses were prepared with different concentrations of Eu 3+ . The structure of these systems were investigated by Raman and IR spectroscopy. The structural study reveals that the glasses contain BiO 3 , BiO 6 , BO 3 , BO 4 and Eu-O structural units. For the samples with a higher content of Eu 2 O 3 , the spectra became very large indicating a more disordered structure. The hygroscopic character of the 3Bi 2 O 3 ·B 2 O 3 glass matrix and the progressive decrease of this behaviour with increasing the Eu 2 O 3 content was observed. Therefore, we conclude that the europium oxide acts as a network modifier in these glasses. (authors)

  6. Multiferroic BiFeO3-BiMnO3 Nanocheckerboard From First Principles

    OpenAIRE

    Palova, L.; Chandra, P.; Rabe, K. M.

    2010-01-01

    We present a first principles study of an unusual heterostructure, an atomic-scale checkerboard of BiFeO3-BiMnO3, and compare its properties to the two bulk constituent materials, BiFeO3 and BiMnO3. The "nanocheckerboard" is found to have a multiferroic ground state with the desired properties of each constituent: polar and ferrimagnetic due to BiFeO3 and BiMnO3, respectively. The effect of B-site cation ordering on magnetic ordering in the BiFeO3-BiMnO3 system is studied. The checkerboard ge...

  7. Potential Fluctuations at Low Temperatures in Mesoscopic-Scale SmTiO3/SrTiO3/SmTiO3 Quantum Well Structures.

    Science.gov (United States)

    Hardy, Will J; Isaac, Brandon; Marshall, Patrick; Mikheev, Evgeny; Zhou, Panpan; Stemmer, Susanne; Natelson, Douglas

    2017-04-25

    Heterointerfaces of SrTiO 3 with other transition metal oxides make up an intriguing family of systems with a bounty of coexisting and competing physical orders. Some examples, such as LaAlO 3 /SrTiO 3 , support a high carrier density electron gas at the interface whose electronic properties are determined by a combination of lattice distortions, spin-orbit coupling, defects, and various regimes of magnetic and charge ordering. Here, we study electronic transport in mesoscale devices made with heterostructures of SrTiO 3 sandwiched between layers of SmTiO 3 , in which the transport properties can be tuned from a regime of Fermi-liquid like resistivity (ρ ∝ T 2 ) to a non-Fermi liquid (ρ ∝ T 5/3 ) by controlling the SrTiO 3 thickness. In mesoscale devices at low temperatures, we find unexpected voltage fluctuations that grow in magnitude as T is decreased below 20 K, are suppressed with increasing contact electrode size, and are independent of the drive current and contact spacing distance. Magnetoresistance fluctuations are also observed, which are reminiscent of universal conductance fluctuations but not entirely consistent with their conventional properties. Candidate explanations are considered, and a mechanism is suggested based on mesoscopic temporal fluctuations of the Seebeck coefficient. An improved understanding of charge transport in these model systems, especially their quantum coherent properties, may lead to insights into the nature of transport in strongly correlated materials that deviate from Fermi liquid theory.

  8. Phase equilibria in the BaUO3-BaZrO3-BaMoO3 system

    International Nuclear Information System (INIS)

    Kurosaki, Ken; Yamanaka, Shinsuke; Matsuda, Tetsushi; Uno, Masayoshi; Yamamoto, Kazuya; Namekawa, Takashi

    2002-01-01

    The phase equilibria in the pseudo-ternary BaUO 3 -BaZrO 3 -BaMoO 3 system were studied to understand the thermochemical properties of the perovskite type gray oxide phase in high burnup MOX fuel. Thermodynamic equilibrium calculation for the system was performed by using a Chem Sage program under the various oxygen potentials. Solid solutions existing in the system were treated by an ideal solution model. The present calculation results well agreed with the previous reported post irradiation examination results, showing that BaMoO 3 was scarcely included in the gray oxide phase. (author)

  9. Superposed epoch analysis of O+ auroral outflow during sawtooth events and substorms

    Science.gov (United States)

    Nowrouzi, N.; Kistler, L. M.; Lund, E. J.; Cai, X.

    2017-12-01

    Sawtooth events are repeated injection of energetic particles at geosynchronous orbit. Studies have shown that 94% of sawtooth events occurred during magnetic storm times. The main factor that causes a sawtooth event is still an open question. Simulations have suggested that heavy ions like O+ may play a role in triggering the injections. One of the sources of the O+ in the Earth's magnetosphere is the nightside aurora. O+ ions coming from the nightside auroral region have direct access to the near-earth magnetotail. A model (Brambles et al. 2013) for interplanetary coronal mass ejection driven sawtooth events found that nightside O+ outflow caused the subsequent teeth of the sawtooth event through a feedback mechanism. This work is a superposed epoch analysis to test whether the observed auroral outflow supports this model. Using FAST spacecraft data from 1997-2007, we examine the auroral O+ outflow as a function of time relative to an injection onset. Then we determine whether the profile of outflow flux of O+ during sawtooth events is different from the outflow observed during isolated substorms. The auroral region boundaries are estimated using the method of (Andersson et al. 2004). Subsequently the O+ outflow flux inside these boundaries are calculated and binned as a function of superposed epoch time for substorms and sawtooth "teeth". In this way, we will determine if sawtooth events do in fact have greater O+ outflow, and if that outflow is predominantly from the nightside, as suggested by the model results.

  10. A new model and gas sensitivity of non-equilibrium xSnO2-(1-x)alpha-Fe2O3 nanopowders prepared by mechanical alloying

    DEFF Research Database (Denmark)

    Zhu, W.; Tan, O.K.; Jiang, Jianzhong

    1998-01-01

    )alpha-Fe2O3 materials. This model can explain non only the lattice expansion of the milled samples, but also takes into account the charge balance by adding oxygen dangling bonds at the particle surfaces, which can be visualized in the nano-sized powders. The thich film gas sensors made by such mechanically......Nano-sized xSnO2-(1-x)alpha-Fe2O3 materials have been prepared using the high energy ball milling technique and their structural and gas sensing properties have been characterized. Based on experimental results, we propose a new structure model, xxx, forthese non-equilibrium, nano-sized xSnO2-(1-x...... alloyed materials have high ethanol gas sensitivity values of 289 in air and 1016 in nitrogen at 1000 p.p.m. and very good gas selectivity to ethanol over CO and H2 gases. It is believed that the high ethanol gas sensitivity of these materials is related to the enormous defects such as O- and O2- dangling...

  11. Giant Polarization Rotation in BiFeO3/SrTiO3 Thin Films.

    Science.gov (United States)

    Langner, M. C.; Chu, Y. H.; Martin, L. M.; Gajek, M.; Ramesh, R.; Orenstein, J.

    2008-03-01

    We use optical second harmonic generation to probe dynamics of the ferroelectric polarization in (111) oriented BiFeO3 thin films grown on SrTiO3 substrates. The second harmonic response indicates 3m point group symmetry and is consistent with a spontaneous polarization normal to the surface of the film. We measure large changes in amplitude and lowering of symmetry, consistent with polarization rotation, when modest electric fields are applied in the plane of the film. At room temperature the rotation is an order of magnitude larger than expected from reported values of the dielectric constant and increases further (as 1/T) as temperature is lowered. We propose a substrate interaction model to explain these results.

  12. modified BiFeO3–BaTiO3

    Indian Academy of Sciences (India)

    based perovskite structures lead- free BiFeO3–BaTiO3 solid solutions are popularly studied due to the high Curie temperature (TC). It was reported that the BiFeO3–BaTiO3 system possessed high piezoelectric. ∗. Author for correspondence ...

  13. Does the X-ray outflow quasar PDS 456 have a UV outflow at 0.3c?

    Science.gov (United States)

    Hamann, Fred; Chartas, George; Reeves, James; Nardini, Emanuele

    2018-05-01

    The quasar PDS 456 (at redshift ˜0.184) has a prototype ultra-fast outflow (UFO) measured in X-rays. This outflow is highly ionized with relativistic speeds, large total column densities log NH(cm-2) > 23, and large kinetic energies that could be important for feedback to the host galaxy. A UV spectrum of PDS 456 obtained with the Hubble Space Telescope in 2000 contains one well-measured broad absorption line (BAL) at ˜1346 Å (observed) that might be Ly α at v ≈ 0.06c or N V λ1240 at v ≈ 0.08c. However, we use photoionization models and comparisons to other outflow quasars to show that these BAL identifications are problematic because other lines that should accompany them are not detected. We argue that the UV BAL is probably C IV at v ≈ 0.30c. This would be the fastest UV outflow ever reported, but its speed is similar to the X-ray outflow and its appearance overall is similar to relativistic UV BALs observed in other quasars. The C IV BAL identification is also supported indirectly by the tentative detection of another broad C IV line at v ≈ 0.19c. The high speeds suggest that the UV outflow originates with the X-ray UFO crudely 20-30 rg from the central black hole. We speculate that the C IV BAL might form in dense clumps embedded in the X-ray UFO, requiring density enhancements of only ≳0.4 dex compared to clumpy structures already inferred for the soft X-ray absorber in PDS 456. The C IV BAL might therefore be the first detection of low-ionization clumps proposed previously to boost the opacities in UFOs for radiative driving.

  14. Phenomenological description of depoling current in Pb0.99Nb0.02(Zr0.95Ti0.05)0.98O3 ferroelectric ceramics under shock wave compression: Relaxation model

    Science.gov (United States)

    Jiang, Dongdong; Du, Jinmei; Gu, Yan; Feng, Yujun

    2012-05-01

    By assuming a relaxation process for depolarization associated with the ferroelectric (FE) to antiferroelectric (AFE) phase transition in Pb0.99Nb0.02(Zr0.95Ti0.05)0.98O3 ferroelectric ceramics under shock wave compression, we build a new model for the depoling current, which is different from both the traditional constant current source (CCS) model and the phase transition kinetics (PTK) model. The characteristic relaxation time and new-equilibrated polarization are dependent on both the shock pressure and electric field. After incorporating a Maxwell s equation, the relaxation model developed applies to all the depoling currents under short-circuit condition and high-impedance condition. Influences of shock pressure, load resistance, dielectric property, and electrical conductivity on the depoling current are also discussed. The relaxation model gives a good description about the suppressing effect of the self-generated electric field on the FE-to-AFE phase transition at low shock pressures, which cannot be described by the traditional models. After incorporating a time- and electric-field-dependent repolarization, this model predicts that the high-impedance current eventually becomes higher than the short-circuit current, which is consistent with the experimental results in the literature. Finally, we make the comparison between our relaxation model and the traditional CCS model and PTK model.

  15. Inhomogeneity at the LaAlO3/SrTiO3 interface

    Science.gov (United States)

    Claeson, T.; Kalabukhov, A.; Gunnarsson, R.; Winkler, D.; Borjesson, J.; Ljustina, N.; Olsson, E.; Popok, V.; Boikov, Yu.; Serenkov, I.; Sakharov, V.

    2010-03-01

    High electrical conductivity has been reported for the interface between two wide-band gap insulators, LaAlO3 (LAO) and SrTiO3 (STO). It occurs above a critical thickness of LAO and can be tuned by an electric field. The conduction has been attributed to i) ``polar catastrophe'' , where the electrostatic charge at the interface is compensated by the transfer of half an electron per unit cell to the interface, ii) oxygen vacancies in the STO, and iii) cation intermixing, which may result in the formation of metallic La1-xSrxTiO3 layer. The relation between microstructure and electrical properties is crucial for understanding the origin of electrical conductivity. We have investigated the interface composition using medium-energy ion spectroscopy, high resolution electron microscopy, and Kelvin probe force microscopy. We find a correlation between cationic intermixing at the interface and electrical properties and inhomogeneities of the interface conductivity that may support a percolation model. Work supported by Swedish VR & KAW, Russian ISTC 3743, EC NANOXIDE

  16. Nanostructured Y2O3

    International Nuclear Information System (INIS)

    Skandan, G.; Hahn, H.; Parker, J.C.

    1991-01-01

    It has been shown that a variety of nanostructured (n-) metal-oxide ceramics such as n-TiO 2 , n-ZrO 2 , n-Al 2 O 3 , n-ZnO and n-MgO can be produced using the inert gas condensation process. Amongst all the nanostructured oxides, the synthesis, microstructure, sintering, and mechanical properties of n-TiO 2 have been studied the most extensively. The gas condensation preparation of nanostructured metal-oxide ceramics involves evaporation of metal nanoparticles, collection and post- oxidation. The original synthesis studies of n-TiO 2 showed that in order to avoid formation of the many low oxidation state oxides in the Ti-O system, the post-oxidation had to be performed by rapidly exposing the Ti nanoparticles to pure oxygen gas. By doing so, the highest oxidation state and the most stable structure, rutile, was obtained. An undesired feature of this step is that the nanoparticles heat up to high temperatures for a brief period of time due to the exothermic nature of the oxidation. As a consequence, the particles with an average size of 12 nm tend to agglomerate into larger structures up to 50 nm. The agglomerated state of the powder is important since it determines the original density and pore size distribution after compaction, as well as the sintering characteristics and final microstructure of the bulk sample. As a consequence of the preparation procedure of n-TiO 2 and the resulting agglomeration, the pore size distribution of n-TiO 2 compacted at room temperature is very wide, with pore sizes ranging from 1 to 200 nm. Nevertheless, the n-TiO 2 sinters at temperatures several hundred degrees lower than conventional coarse grained ceramics. From the previous results on n- TiO 2 it is anticipated that better microstructures and properties can be achieved by reducing the agglomeration of nanostructured powders through a more controlled post- oxidation process

  17. The phase diagram of KNO3-KClO3

    International Nuclear Information System (INIS)

    Zhang Xuejun; Tian Jun; Xu Kangcheng; Gao Yici

    2004-01-01

    The binary phase diagram of KNO 3 -KClO 3 is studied by means of differential scanning calorimetry (DSC) and high-temperature X-ray diffraction. The limited solid solutions, K(NO 3 ) 1-x (ClO 3 ) x (0 3 ) 1-x (ClO 3 ) x (0.90 3 -based solid solutions and KClO 3 -based solid solutions phase, respectively. For KNO 3 -based solid solutions, KNO 3 ferroelectric phase can be stable from 423 to 223 K as a result of substituting of NO 3 by ClO 3 -radicals. The temperatures for solidus and liquidus have been determined based on limited solid solutions. Two models, Henrian solution and regular solution theory for KNO 3 -based (α) phase and KClO 3 -based (β) phase, respectively, are employed to reproduce solidus and liquidus of the phase diagram. The results are in good agreement with the DSC data. The thermodynamic properties for α and β solid solutions have been derived from an optimization procedure using the experimental data. The calculated phase diagram and optimized thermodynamic parameters are thermodynamically self-consistent

  18. Atmospheric transport and outflow of polycyclic aromatic hydrocarbons from China

    Energy Technology Data Exchange (ETDEWEB)

    Chang Lang; Shu Tao; Wenxin Liu; Yanxu Zhang; Staci Simonich [Peking University, Beijing (China). Laboratory for Earth Surface Processes, College of Environmental Sciences

    2008-07-15

    A potential receptor influence function (PRIF) model, based on air mass forward trajectory calculations, was applied to simulate the atmospheric transport and outflow of polycyclic aromatic hydrocarbons (PAHs) emitted from China. With a 10 day atmospheric transport time, most neighboring countries and regions, as well as remote regions, were influenced by PAH emissions from China. Of the total annual PAH emission of 114 Gg, 92.7% remained within the boundary of mainland China. The geographic distribution of PRIFs within China was similar to the geographic distribution of the source regions, with high values in the North China Plain, Sichuan Basin, Shanxi, and Guizhou province. The Tarim basin and Sichuan basin had unfavorable meteorological conditions for PAH outflow. Of the PAH outflow from China (8092 tons or 7.1% of the total annual PAH emission), approximately 69.9% (5655 tons) reached no further than the offshore environment of mainland China and the South China Sea. Approximate 227, 71, 746, and 131 tons PAHs reached North Korea, South Korea, Russia-Mongolia region, and Japan, respectively, 2-4 days after the emission. Only 1.4 tons PAHs reached North America after more than 9 days. Interannual variation in the eastward PAH outflow was positively correlated to cold episodes of El Nino/Southern Oscillation. However, trans-Pacific atmospheric transport of PAHs from China was correlated to Pacific North America index (PNA) which is associated with the strength and position of westerly winds. 38 refs., 4 figs.

  19. Towards positive feedbacks between vegetation and tropospheric O3

    Science.gov (United States)

    VanLoocke, A. D.; Bernacchi, C. J.; Ainsworth, E. A.; Betzelberger, A. M.

    2011-12-01

    C during the midday for the highest O3 treatment. These results suggest the potential for a positive feedback on O3 through vegetation-induced alterations in atmospheric conditions, in particular, higher temperature favor the formation of O3 and lower humidity slows the destruction of O3. The results of this experiment are a first step in assessing the potential for positive vegetation-O3 feedback because they can only be directly applied to soybean. However, similarities in the responses of other C3 plants to elevated O3 suggest that the observed responses may apply to a wide range of species. Integrating these responses in land-atmosphere modeling studies are needed to quantify how canopy-scale fluxes might translate to positive feedbacks on [O3] in the troposphere.

  20. THE ROLE OF COSMIC-RAY PRESSURE IN ACCELERATING GALACTIC OUTFLOWS

    Energy Technology Data Exchange (ETDEWEB)

    Simpson, Christine M.; Pakmor, Rüdiger; Pfrommer, Christoph; Springel, Volker [Heidelberger Institut für Theoretische Studien, Schloss-Wolfsbrunnenweg 35, D-69118 Heidelberg (Germany); Marinacci, Federico [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Glover, Simon C. O. [Zentrum für Astronomie der Universität Heidelberg, ITA, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Clark, Paul C. [School of Physics and Astronomy, Queen’s Buildings, The Parade, Cardiff University, Cardiff CF24 3AA (United Kingdom); Smith, Rowan J., E-mail: Christine.Simpson@h-its.org [Jodrell Bank Centre for Astrophysics, University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom)

    2016-08-20

    We study the formation of galactic outflows from supernova (SN) explosions with the moving-mesh code AREPO in a stratified column of gas with a surface density similar to the Milky Way disk at the solar circle. We compare different simulation models for SN placement and energy feedback, including cosmic rays (CRs), and find that models that place SNe in dense gas and account for CR diffusion are able to drive outflows with similar mass loading as obtained from a random placement of SNe with no CRs. Despite this similarity, CR-driven outflows differ in several other key properties including their overall clumpiness and velocity. Moreover, the forces driving these outflows originate in different sources of pressure, with the CR diffusion model relying on non-thermal pressure gradients to create an outflow driven by internal pressure and the random-placement model depending on kinetic pressure gradients to propel a ballistic outflow. CRs therefore appear to be non-negligible physics in the formation of outflows from the interstellar medium.

  1. C-A-S-H synthesis and thermodynamics modelling in CaO-Al2O3-SiO2-H2O system

    International Nuclear Information System (INIS)

    Haas, J.; Pochard, I.; Nonat, A.

    2015-01-01

    Ordinary Portland cement (OPC) is being increasingly replaced by blended cements, where part of the clinker is replaced by secondary cementitious materials (SCM) such as blast furnace or fly ash. The use of SCM enables to achieve various aims as the cost reduction by recovery of by-products, the CO 2 emission reduction, the obtaining of specific properties as low pH. So, blended cements are more and more current in different fields as civil engineering and nuclear waste repository. The use of silica and/or aluminium rich SCMs directly impacts the amount and the kind of hydrates formed, hence the volume and the porosity and finally the durability of these materials. Aluminates containing hydrates formation is not well understood. Al content can result from Al-uptake in C-S-H due to Al-substitution of Si-tetrahedra to well crystallised hydrates like straetlingite or katoite phases. This study proposes a surface dependant thermodynamic model to predict and to correlate the Al-uptake (substitution) of C-A-S-H with solutions representative of that of cement pores chemistry. For this purpose, pure C-A-S-H alkali-free were synthesized in diluted suspensions. On one hand, hydrates and their solutions were characterized at equilibrium. On the other hand, thermodynamics modelling were performed from these collected data to describe C-A-S-H in the equilibrium solutions. These results allowed evaluating the Al-availability in the cementitious system and especially for aluminates containing hydrates precipitation. (authors)

  2. Phase relations in the SiC-Al2O3-Pr2O3 system

    International Nuclear Information System (INIS)

    Pan, W.; Wu, L.; Jiang, Y.; Huang, Z.

    2016-01-01

    Phase relations in the Si-Al-Pr-O-C system, including the SiC-Al 2 O 3 -Pr 2 O 3 , the Al 2 O 3 -Pr 2 O 3 -SiO 2 and the SiC-Al 2 O 3 -Pr 2 O 3 -SiO 2 subsystems, were determined by means of XRD phase analysis of solid-state-reacted samples fabricated by using SiC, Al 2 O 3 , Pr 2 O 3 and SiO 2 powders as the starting materials. Subsolidus phase diagrams of the systems were presented. Two Pr-aluminates, namely PrAlO 3 (PrAP) and PrAl 11 O 18 (β(Pr) β-Al 2 O 3 type) were formed in the SiC-Al 2 O 3 -Pr 2 O 3 system. SiC was compatible with both of them. Pr-silicates of Pr 2 SiO 5 , Pr 2 Si 2 O 7 and Pr 9.33 Si 6 O 26 (H(Pr) apatite type) were formed owing to presence of SiO 2 impurity in the SiC powder. The presence of the SiO 2 extended the ternary system of SiC-Al 2 O 3 -Pr 2 O 3 into a quaternary system of SiC-Al 2 O 3 -SiO 2 -Pr 2 O 3 (Si-Al-Pr-O-C). SiC was compatible with Al 2 O 3 , Pr 2 O 3 and the Pr-silicates. The effect of SiO 2 on the phase relations and liquid phase sintering of SiC ceramics was discussed.

  3. Melting relations of model lherzolite in the system CaO-MgO-Al2O3-SiO2 at 2.4-3.4 GPa and the generation of komatiites

    Science.gov (United States)

    Gudfinnsson, Gudmundur H.; Presnall, Dean C.

    1996-12-01

    Isobarically invariant phase relations in the CaO-MgO-Al2O3-SiO2 system (CMAS) involving the lherzolite phase assemblage in equilibrium with liquid have been determined at 2.4-3.4 GPa. These phase relations form the solidus of model lherzolite in the CMAS system. Our data, which include determinations of all phase compositions, are in excellent agreement with the 3.0 and 4.0 GPa points of Milholland and Presnall [1991] and Davis and Schairer [1965], respectively. The invariant transition on the P-T solidus curve from spinel- to garnet-lherzolite at 3.0 GPa, 1575°C [Milholland and Presnall, 1991], is confirmed, but we observe that the theoretically required temperature depression on the solidus curve at this point is not experimentally detectable. Composition trends along the solidus take a sharp turn at the transition. In the spinel-lherzolite stability field, melt compositions become increasingly Fo-normative and less En-normative with increasing pressure, but become less Fo-normative and more pyroxenitic as pressure increases in the garnet-lherzolite stability field. Calculated melting reactions indicate that forsterite is in reaction relationship with the melt up to 3.0 GPa. Orthopyroxene is also in reaction relationship at pressures higher than just over 2.8 GPa and is the only phase in reaction relationship with the melt in the garnet-lherzolite stability field. Comparison of the normative compositions and the CaO/Al2O3 values of the komatiites of Gorgona Island and of the Reliance Formation in Zimbabwe with the compositions of liquids along the solidus of model lherzolite in the CMAS system indicates that the former komatiites were generated at pressures close to 3.7 GPa and the latter at close to 4.5 GPa, assuming that the melt generation occurred in the presence of the complete garnet-lherzolite assemblage.

  4. Artificial O3 formation during fireworks

    Science.gov (United States)

    Fiedrich, M.; Kurtenbach, R.; Wiesen, P.; Kleffmann, J.

    2017-09-01

    In several previous studies emission of ozone (O3) during fireworks has been reported, which was attributed to either photolysis of molecular oxygen (O2) or nitrogen dioxide (NO2) by short/near UV radiation emitted during the high-temperature combustion of fireworks. In contrast, in the present study no O3 formation was observed using a selective O3-LOPAP instrument during the combustion of pyrotechnical material in the laboratory, while a standard O3 monitor using UV absorption showed extremely high O3 signals. The artificial O3 response of the standard O3 monitor was caused by known interferences associated with high levels of co-emitted VOCs and could also be confirmed in field measurements during New Year's Eve in the city of Wuppertal, Germany. The present results help to explain unreasonably high ozone levels documented during ambient fireworks, which are in contradiction to the fast titration of O3 by nitrogen monoxide (NO) in the night-time atmosphere.

  5. Density of Ga2O3 Liquid

    OpenAIRE

    Dingwell, Donald B.

    1992-01-01

    The density of Ga2O3 liquid in equilibrium with air has been measured at 18000 to 19000C using an Ir double-bob Archimedean method. The data yield the following description of the density of Ga2O3 liquid: ρ= 4.8374(84)–0.00065(12)(T −18500C). This density-temperature relationship is compared with the partial molar volume of Ga2O3 in glasses in the systems CaO–Ga2O3–SiO2 and Na2O–Ga2O3–SiO2, corrected to the glass transition temperature using thermal expansivities. The comparison illustrates t...

  6. The Role of Ionospheric Outflow Preconditioning in Determining Storm Geoeffectiveness

    Science.gov (United States)

    Welling, D. T.; Liemohn, M. W.; Ridley, A. J.

    2012-12-01

    It is now well accepted that ionospheric outflow plays an important role in the development of the plasma sheet and ring current during geomagnetic storms. Furthermore, even during quiet times, ionospheric plasma populates the magnetospheric lobes, producing a reservoir of hydrogen and oxygen ions. When the Interplanetary Magnetic Field (IMF) turns southward, this reservoir is connected to the plasma sheet and ring current through magnetospheric convection. Hence, the conditions of the ionosphere and magnetospheric lobes leading up to magnetospheric storm onset have important implications for storm development. Despite this, there has been little research on this preconditioning; most global simulations begin just before storm onset, neglecting preconditioning altogether. This work explores the role of preconditioning in determining the geoeffectiveness of storms using a coupled global model system. A model of ionospheric outflow (the Polar Wind Outflow Model, PWOM) is two-way coupled to a global magnetohydrodynamic model (the Block-Adaptive Tree Solar wind Roe-type Upwind Scheme, BATS-R-US), which in turn drives a ring current model (the Ring current Atmosphere interactions Model, RAM). This unique setup is used to simulate an idealized storm. The model is started at many different times, from 1 hour before storm onset to 12 hours before. The effects of storm preconditioning are examined by investigating the total ionospheric plasma content in the lobes just before onset, the total ionospheric contribution in the ring current just after onset, and the effects on Dst, magnetic elevation angle at geosynchronous, and total ring current energy density. This experiment is repeated for different solar activity levels as set by F10.7 flux. Finally, a synthetic double-dip storm is constructed to see how two closely spaced storms affect each other by changing the preconditioning environment. It is found that preconditioning of the magnetospheric lobes via ionospheric

  7. Understanding the effect models of ionic liquids in the synthesis of NH4-Dw and γ-AlOOH nanostructures and their conversion into porous γ-Al2O3.

    Science.gov (United States)

    Duan, Xiaochuan; Kim, Tongil; Li, Di; Ma, Jianmin; Zheng, Wenjun

    2013-05-03

    Well-dispersed ammonium aluminum carbonate hydroxide (NH4-Dw) and γ-AlOOH nanostructures with controlled morphologies have been synthesized by employing an ionic-liquid-assisted hydrothermal process. The basic strategies that were used in this work were: 1) A controllable phase transition from NH4-Dw to γ-AlOOH could be realized by increasing the reaction temperature and 2) the morphological evolution of NH4-Dw and γ-AlOOH nanostructures could be influenced by the concentration of the ionic liquid. Based on these experimental results, the main objective of this work was to clarify the effect models of the ionic liquids on the synthesis of NH4-Dw and γ-AlOOH nanostructures, which could be divided into cationic- or anionic-dominant effect models, as determined by the different surface structures of the targets. Specifically, under the cationic-dominant regime, the ionic liquids mainly showed dispersion effects for the NH4-Dw nanostructures, whereas the anionic-dominant model could induce the self-assembly of the γ-AlOOH particles to form hierarchical structures. Under the guidance of the proposed models, the effect of the ionic liquids would be optimized by an appropriate choice of cations or anions, as well as by considering the different effect models with the substrate surface. We expect that such effect models between ionic liquids and the target products will be helpful for understanding and designing rational ionic liquids that contain specific functional groups, thus open up new opportunities for the synthesis of inorganic nanomaterials with new morphologies and improved properties. In addition, these as-prepared NH4-Dw and γ-AlOOH nanostructures were converted into porous γ-Al2O3 nanostructures by thermal decomposition, whilst preserving the same morphology. By using HRTEM and nitrogen-adsorption analysis, the obtained γ-Al2O3 samples were found to have excellent porous properties and, hence, may have applications in catalysis and adsorption

  8. Effect of composition on properties of In2O3-Ga2O3 thin films

    Science.gov (United States)

    Demin, I. E.; Kozlov, A. G.

    2017-06-01

    The In2O3-Ga2O3 mixed oxide polycrystalline thin films with various ratios of components were obtained by pulsed laser deposition. The effect of films composition on surface morphology, electrophysical and gas sensing properties and energies of adsorption and desorption of combustible gases was studied. The films with50%In2O3-50%Ga2O3 composition showed maximum gas response (˜25 times) combined with minimum optimal working temperature (˜530 °C) as compared with the other films. The optical transmittance of the films in visible range was investigated. For 50%In2O3-50%Ga2O3 films, the transmittance is higher in comparison with the other films. The explanation of the dependency of films behaviors on their composition was presented.The In2O3-Ga2O3 films were assumed to have perspectives as gas sensing material for semiconducting gas sensors.

  9. Heat transfer enhancement and entropy generation analysis of Al2O3-water nanofluid in an alternating oval cross-section tube using two-phase mixture model under turbulent flow

    Science.gov (United States)

    Najafi Khaboshan, Hasan; Nazif, Hamid Reza

    2018-04-01

    Heat transfer and turbulent flow of Al2O3-water nanofluid within alternating oval cross-section tube are numerically simulated using Eulerian-Eulerian two-phase mixture model. The primary goal of the present study is to investigate the effects of nanoparticles volume fraction, nanoparticles diameter and different inlet velocities on heat transfer, pressure drop and entropy generation characteristics of the alternating oval cross-section tube. For numerical simulation validation, the numerical results were compared with experimental data. Also, constant wall temperature boundary condition was considered on the tube wall. In addition, the comparison of thermal-hydraulic performance and the entropy generation characteristics between alternating oval cross-section tube and circular tube under same fluids were done. The results show that the heat transfer coefficient and pressure drop of alternating oval cross-section tube is more than base tube under same fluids. Also, these two parameters are increased when adding Al2O3 nanoparticle into water fluid, at any inlet velocity for both tubes. Furthermore, compared to the base fluid, the value of the heat transfer enhancement of nanofluid is higher than the increase of friction factor of nanofluid at the same given inlet boundary conditions. The results of entropy generation analysis illustrate that the total entropy generation increase with increasing the nanoparticles volume fraction and decreasing the nanoparticles diameter of nanofluid. The generation of thermal entropy is the main part of irreversibility, and Bejan number with an increase of the nanoparticles diameter slightly increases. Finally, at any given inlet velocity the frictional irreversibility is grown with an increase the nanoparticles volume fraction.

  10. Outflow and Accretion Physics in Active Galactic Nuclei

    Science.gov (United States)

    McGraw, Sean Michael

    2016-09-01

    This dissertation focuses on placing observational constraints on outflows and accretion disks in active galactic nuclei (AGN) for the purpose of better understanding the physics of super-massive black holes (SMBHs) and their evolution with the host galaxy over cosmic time. Quasar outflows and their importance in SMBH-host galaxy co-evolution can be further understood by analyzing broad absorption lines (BALs) in rest-frame UV spectra that trace a range of wind conditions. We quantify the properties of the flows by conducting BAL variability studies using multiple-epoch spectra acquired primarily from MDM Observatory and from the Sloan Digital Sky Survey. Iron low-ionization BALs (FeLoBALs) are a rare type of outflow that may represent a transient phase in galaxy evolution, and we analyze the variations in 12 FeLoBAL quasars with redshifts between 0.7 ≤ z ≤ 1.9 and rest frame timescales between ˜10 d to 7.6 yr. We investigate BAL variability in 71 quasar outflows that exhibit P V absorption, a tracer of high column density gas (i.e. NH ≥ 1022 cm -2), in order to quantify the energies and momenta of the flows. We also characterize the variability patterns of 26 quasars with mini-BALs, an interesting class of absorbers that may represent a distinct phase in the evolution of outflows. Low-luminosity AGN (LLAGN) are important objects to study since their prominence in the local Universe suggest a possible evolution from the quasar era, and their low radiative outputs likely indicate a distinct mode of accretion onto the SMBH. We probe the accretion conditions in the LLAGN NGC 4203 by estimating the SMBH mass, which is obtained by modeling the 2-dimensional velocity field of the nebular gas using spectra from the Hubble Space Telescope. We detect significant BAL and mini-BAL variability in a subset of quasars from each of our samples, with measured rest-frame variability time-scales from days to years and over multiple years on average. Variable wavelength

  11. Synthesis and properties of γ-Ga2O3-Al2O3 solid solutions

    Science.gov (United States)

    Afonasenko, T. N.; Leont'eva, N. N.; Talzi, V. P.; Smirnova, N. S.; Savel'eva, G. G.; Shilova, A. V.; Tsyrul'nikov, P. G.

    2017-10-01

    The textural and structural properties of mixed oxides Ga2O3-Al2O3, obtained via impregnating γ-Al2O3 with a solution of Ga(NO3)3 and subsequent heat treatment, are studied. According to the results from X-ray powder diffraction, gallium ions are incorporated into the structure of aluminum oxide to form a solid solution of spinel-type γ-Ga2O3-Al2O3 up to a Ga2O3 content of 50 wt % of the total weight of the sample, accompanied by a reduction in the specific surface area, volume, and average pore diameter. It is concluded that when the Ga2O3 content exceeds 50 wt %, the β-Ga2O3 phase is observed along with γ-Ga2O3-Al2O3 solid solution. 71Ga and 27Al NMR spectroscopy shows that gallium replaces aluminum atoms from the tetrahedral position to the octahedral coordination in the structure of γ-Ga2O3-Al2O3.

  12. Large-Scale Outflows in Seyfert Galaxies

    Science.gov (United States)

    Colbert, E. J. M.; Baum, S. A.

    1995-12-01

    \\catcode`\\@=11 \\ialign{m @th#1hfil ##hfil \\crcr#2\\crcr\\sim\\crcr}}} \\catcode`\\@=12 Highly collimated outflows extend out to Mpc scales in many radio-loud active galaxies. In Seyfert galaxies, which are radio-quiet, the outflows extend out to kpc scales and do not appear to be as highly collimated. In order to study the nature of large-scale (>~1 kpc) outflows in Seyferts, we have conducted optical, radio and X-ray surveys of a distance-limited sample of 22 edge-on Seyfert galaxies. Results of the optical emission-line imaging and spectroscopic survey imply that large-scale outflows are present in >~{{1} /{4}} of all Seyferts. The radio (VLA) and X-ray (ROSAT) surveys show that large-scale radio and X-ray emission is present at about the same frequency. Kinetic luminosities of the outflows in Seyferts are comparable to those in starburst-driven superwinds. Large-scale radio sources in Seyferts appear diffuse, but do not resemble radio halos found in some edge-on starburst galaxies (e.g. M82). We discuss the feasibility of the outflows being powered by the active nucleus (e.g. a jet) or a circumnuclear starburst.

  13. Electric-field gradients at 181Ta impurity sites in Ho2O3 and Eu2O3 bixbyites

    International Nuclear Information System (INIS)

    Errico, Leonardo A.; Renteria, Mario; Bibiloni, Anibal G.; Freitag, Kristian

    2007-01-01

    The time-differential γ-γ perturbed-angular-correlation (PAC) technique with ion-implanted 181 Hf tracers has been applied to study the hyperfine interactions of 181 Ta impurities in the cubic bixbyite structure of Ho 2 O 3 and Eu 2 O 3 . The PAC experiments were performed in air in the temperature range 300-1373 K (in the case of Ho 2 O 3 ) and 77-1273 K (in the case of Eu 2 O 3 ). For both oxides, two electric-quadrupole interactions were found and attributed to the electric-field gradients (EFGs) acting on 181 Ta probes substitutionally located at the two free-of-defects nonequivalent cation sites of the bixbyite structure. In the case of Ho 2 O 3 , two additional interactions were found in the temperature range 300-573 K. These results, as well as previous characterizations of the EFG at 181 Ta sites in bixbyites, were compared to those obtained in experiments using 111 Cd as probe, and to point-charge model calculations. Very recent ab initio predictions for the EFG tensor at impurities sites in binary oxides are also discussed. All these results enable us to discuss the validity of the widely used ionic model to describe the EFG in these highly ionic compounds

  14. Transport pathways for Asian pollution outflow over the Pacific: Interannual and seasonal variations

    Science.gov (United States)

    Liu, Hongyu; Jacob, Daniel J.; Bey, Isabelle; Yantosca, Robert M.; Duncan, Bryan N.; Sachse, Glen W.

    2003-10-01

    The meteorological pathways contributing to Asian pollution outflow over the Pacific are examined with a global three-dimensional model analysis of CO observations from the Transport and Chemical Evolution over the Pacific (TRACE-P) aircraft mission (February-April 2001). The model is used also to place the TRACE-P observations in an interannual (1994-2001) and seasonal context. The major process driving Asian pollution outflow in spring is frontal lifting ahead of southeastward-moving cold fronts (the leading edge of cold surges) and transport in the boundary layer behind the cold fronts. Orographic lifting over central and eastern China combines with the cold fronts to promote the transport of Chinese pollution to the free troposphere. Outflow of seasonal biomass burning in Southeast Asia during spring takes place mostly by deep convection but also by northeastward transport and frontal lifting, mixing with the anthropogenic outflow. Boundary layer outflow over the western Pacific is largely devoid of biomass burning influence. European and African (biomass burning) plumes in Asian outflow during TRACE-P were weak (pollution signal. Spring 2001 (La Niña) was characterized by unusually frequent cold surge events in the Asian Pacific rim and strong convection in Southeast Asia, leading to unusually strong boundary layer outflow of anthropogenic emissions and convective outflow of biomass burning emissions in the upper troposphere. The Asian outflow flux of CO to the Pacific is found to vary seasonally by a factor of 3-4 (maximum in March and minimum in summer). The March maximum results from frequent cold surge events and seasonal biomass burning emissions.

  15. Decoupling peroxyacetyl nitrate from ozone in Chinese outflows observed at Gosan Climate Observatory

    Science.gov (United States)

    Han, Jihyun; Lee, Meehye; Shang, Xiaona; Lee, Gangwoong; Emmons, Louisa K.

    2017-09-01

    We measured peroxyacetyl nitrate (PAN) and other reactive species such as O3, NO2, CO, and SO2 with aerosols including mass, organic carbon (OC), and elemental carbon (EC) in PM2. 5 and K+ in PM1. 0 at Gosan Climate Observatory in Korea (33.17° N, 126.10° E) during 19 October-6 November 2010. PAN was determined through fast gas chromatography with luminol chemiluminescence detection at 425 nm every 2 min. The PAN mixing ratios ranged from 0.1 (detection limit) to 2.4 ppbv with a mean of 0.6 ppbv. For all measurements, PAN was unusually better correlated with PM2. 5 (Pearson correlation coefficient, γ = 0.79) than with O3 (γ = 0.67). In particular, the O3 level was highly elevated with SO2 at midnight, along with a typical midday peak when air was transported rapidly from the Beijing areas. The PAN enhancement was most noticeable during the occurrence of haze under stagnant conditions. In Chinese outflows slowly transported over the Yellow Sea, PAN gradually increased up to 2.4 ppbv at night, in excellent correlation with a concentration increase in PM2. 5 OC and EC, PM2. 5 mass, and PM1. 0 K+. The high K+ concentration and OC / EC ratio indicated that the air mass was impacted by biomass combustion. This study highlights PAN decoupling with O3 in Chinese outflows and suggests PAN as a useful indicator for diagnosing continental outflows and assessing their perturbation of regional air quality in northeast Asia.

  16. Decoupling peroxyacetyl nitrate from ozone in Chinese outflows observed at Gosan Climate Observatory

    Directory of Open Access Journals (Sweden)

    J. Han

    2017-09-01

    Full Text Available We measured peroxyacetyl nitrate (PAN and other reactive species such as O3, NO2, CO, and SO2 with aerosols including mass, organic carbon (OC, and elemental carbon (EC in PM2. 5 and K+ in PM1. 0 at Gosan Climate Observatory in Korea (33.17° N, 126.10° E during 19 October–6 November 2010. PAN was determined through fast gas chromatography with luminol chemiluminescence detection at 425 nm every 2 min. The PAN mixing ratios ranged from 0.1 (detection limit to 2.4 ppbv with a mean of 0.6 ppbv. For all measurements, PAN was unusually better correlated with PM2. 5 (Pearson correlation coefficient, γ =  0.79 than with O3 (γ =  0.67. In particular, the O3 level was highly elevated with SO2 at midnight, along with a typical midday peak when air was transported rapidly from the Beijing areas. The PAN enhancement was most noticeable during the occurrence of haze under stagnant conditions. In Chinese outflows slowly transported over the Yellow Sea, PAN gradually increased up to 2.4 ppbv at night, in excellent correlation with a concentration increase in PM2. 5 OC and EC, PM2. 5 mass, and PM1. 0 K+. The high K+ concentration and OC ∕ EC ratio indicated that the air mass was impacted by biomass combustion. This study highlights PAN decoupling with O3 in Chinese outflows and suggests PAN as a useful indicator for diagnosing continental outflows and assessing their perturbation of regional air quality in northeast Asia.

  17. The MgO-Al2O3-SiO2 system - Free energy of pyrope and Al2O3-enstatite. [in earth mantle formation

    Science.gov (United States)

    Saxena, S. K.

    1981-01-01

    The model of fictive ideal components is used to determine Gibbs free energies of formation of pyrope and Al2O3-enstatite from the experimental data on coexisting garnet and orthopyroxene and orthopyroxene and spinel in the temperature range 1200-1600 K. It is noted that Al2O3 forms an ideal solution with MgSiO3. These thermochemical data are found to be consistent with the Al2O3 isopleths that could be drawn using most recent experimental data and with the reversed experimental data on the garnet-spinel field boundary.

  18. A new molybdenum trioxide hydrate MoO3.1/3H2O and a new monoclinic form of MoO3

    International Nuclear Information System (INIS)

    Harb, F.; Gerand, B.; Nowogrocki, G.; Figlarz, M.

    1986-01-01

    A new hydrate of molybdenum trioxide MoO 3 .1/3H 2 O has been obtained by hydrothermal treatment at 110 0 C of either aqueous suspensions of MoO 3 .2H 2 O or aqueous molybdic acid solutions. The hydrate crystallizes in the orthorhombic system, lattice parameters are given; a structural model is proposed by comparison with the isostructural WO 3 .1/3H 2 O phase. The dehydration of MoO 3 .1/3H 2 O leads to a new anhydrous molybdenum trioxide, monoclinic, the structure of which is of ReO 3 type [fr

  19. A young bipolar outflow from IRAS 15398-3359

    Science.gov (United States)

    Bjerkeli, P.; Jørgensen, J. K.; Brinch, C.

    2016-03-01

    Context. Changing physical conditions in the vicinity of protostars allow for a rich and interesting chemistry to occur. Heating and cooling of the gas allows molecules to be released from and frozen out on dust grains. These changes in physics, traced by chemistry as well as the kinematical information, allows us to distinguish between different scenarios describing the infall of matter and the launching of molecular outflows and jets. Aims: We aim to determine the spatial distribution of different species that are of different chemical origin. This is to examine the physical processes in play in the observed region. From the kinematical information of the emission lines we aim to determine the nature of the infalling and outflowing gas in the system. We also aim to determine the physical properties of the outflow. Methods: Maps from the Submillimeter Array (SMA) reveal the spatial distribution of the gaseous emission towards IRAS 15398-3359. The line radiative transfer code LIME is used to construct a full 3D model of the system taking all relevant components and scales into account. Results: CO, HCO+, and N2H+ are detected and shown to trace the motions of the outflow. For CO, the circumstellar envelope and the surrounding cloud also have a profound impact on the observed line profiles. N2H+ is detected in the outflow, but is suppressed towards the central region, perhaps because of the competing reaction between CO and H3+ in the densest regions as well as the destruction of N2H+ by CO. N2D+ is detected in a ridge south-west of the protostellar condensation and is not associated with the outflow. The morphology and kinematics of the CO emission suggests that the source is younger than ~1000 years. The mass, momentum, momentum rate, mechanical luminosity, kinetic energy, and mass-loss rate are also all estimated to be low. A full 3D radiative transfer model of the system can explain all the kinematical and morphological features in the system.

  20. Phase equilibria in the system Li2O - MoO3 - Sc2O3

    International Nuclear Information System (INIS)

    Safonov, V.V.; Chaban, N.G.; Porotnikov, N.V.

    1984-01-01

    Using the methods of DTA and X-ray phase analysis, interaction of components in the system Li 2 O-MoO 3 -Sc 2 O 3 in concentration range, adjacent to the vertex of MoO 3 , has been studied. Projection of the Li 2 MoO 4 -MoO 3 -Sc 2 (MoO 4 ) 3 system liquidus on concentrational triangle of the compositions Li 2 O-MoO 3 -Sc 2 O 3 , which consists of the fields of primary separation of Li 2 MoO 4 , Li 2 Mo 5 O 17 , Li 2 Mo 4 O 13 , MoO 3 , Sc 2 (MoO 4 ) 3 , Li 3 Sc(MoO 4 ) 3 and LiSc(MoO 4 ) 2 , is built

  1. Raman tensor elements of β-Ga2O3.

    Science.gov (United States)

    Kranert, Christian; Sturm, Chris; Schmidt-Grund, Rüdiger; Grundmann, Marius

    2016-11-03

    The Raman spectrum and particularly the Raman scattering intensities of monoclinic β-Ga 2 O 3 are investigated by experiment and theory. The low symmetry of β-Ga 2 O 3 results in a complex dependence of the Raman intensity for the individual phonon modes on the scattering geometry which is additionally affected by birefringence. We measured the Raman spectra in dependence on the polarization direction for backscattering on three crystallographic planes of β-Ga 2 O 3 and modelled these dependencies using a modified Raman tensor formalism which takes birefringence into account. The spectral position of all 15 Raman active phonon modes and the Raman tensor elements of 13 modes were determined and are compared to results from ab-initio calculations.

  2. Conduction Mechanism by Using CBH Model in Fe3+ and Mn3+ Ion Modified Pb(Zr0.65−xAxTi0.35O3 (A = Mn3+/Fe3+ Ceramics

    Directory of Open Access Journals (Sweden)

    Niranjan Sahu

    2013-01-01

    Full Text Available Polycrystalline samples of manganese and iron substituted lead zirconium titanate (PZT with general formula Pb(Zr0.65−xAxTi0.35O3 (A = Mn3+ and Fe3+ ceramics have been synthesized by high temperature solid state reaction technique. X-ray diffraction (XRD patterns were recorded at room temperature to study the crystal structure. All the patterns could be refined by employing the Rietveld method to R3c space group with rhombohedral symmetry. Microstructural properties of the materials were analyzed by scanning electron microscope (SEM, and compositional analysis was carried out by energy dispersive spectrum (EDS measurements. All the materials exhibit ferroelectric to paraelectric transition. The variation of dielectric constant and loss tangent with temperature and frequency is investigated. The decrease of activation energy and increases of AC conductivity with the Fe3+ or Mn3+ ion concentration have been observed. The AC conductivity has been analyzed by the power law. The frequency exponent with the function of temperature has been analyzed by assuming that the AC conduction mechanism is the correlated barrier hopping (CBH model. The conduction in the present sample is found to be of bipolaron type for Mn3+ ion-doped sample. However, the conduction mechanism could not be explained by CBH model for Fe3+ ion-doped sample.

  3. Modeling of the multilevel conduction characteristics and fatigue profile of Ag/La1/3Ca2/3MnO3/Pt structures using a compact memristive approach

    Science.gov (United States)

    Miranda, E.; Román Acevedo, W.; Rubi, D.; Lüders, U.; Granell, P.; Suñé, J.; Levy, P.

    2017-05-01

    The hysteretic conduction characteristics and fatigue profile of La1/3Ca2/3MnO3 (LCMO)-based memristive devices were investigated. The oxide films were grown by pulsed laser deposition (PLD) and sandwiched between Ag and Pt electrodes. The devices exhibit bipolar resistive switching (RS) effect with well-defined intermediate conduction states that arise from partial SET and RESET events. The current-voltage curves are modeled and simulated using a compact memristive approach. Two equations are considered: one for the electron transport based on the double-diode equation and the other for the memory state of the device driven by the play operator with logistic ridge functions. An expression that accounts for the remnant resistance of the device is obtained after simplifying the model equations in the low-voltage limit. The role played by the power dissipation in the LCMO reset dynamics as well as the asymmetrical reduction of the resistance window caused by long trains of switching pulses are discussed.

  4. Mnx/2Nbx/2O3 ceramics

    Indian Academy of Sciences (India)

    Unknown

    Abstract. The paper reports investigations of relative permittivity, εr, electrical conductivity, σ, saturation polarization, Ps, infrared absorption and structural properties of compensating valency substituted BaTiO3. The compositions investigated are BaTi(1–x)Mnx/2Nbx/2O3 for x = 0⋅00; 0⋅025; 0⋅05; 0⋅1; 0⋅2; 0⋅4.

  5. Spin-Orbit Interaction and Kondo Scattering at the PrAlO3/SrTiO3 Interface

    Science.gov (United States)

    Mozaffari, Shirin; Guchhait, Samaresh; Markert, John

    We have investigated the effect of oxygen content, in the PO2 range of 6 ×10-6 - 1 ×10-3 torr, on the spin-orbit (SO) interaction at PrAlO3/SrTiO3 interface. The most-conducting 2-D-like PrAlO3 interfaces were not as conducting as comparable LaAlO3 samples, indicating either a steric or mixed-valent effect. The least-conducting, most oxygenated PrAlO3 interface exhibits hole conductivity, a departure from the typical electron-doped behavior. For 10-5 and 10-4 torr samples, high-temperature metallic behavior is accompanied by an upturn in resistivity at low temperatures, consistent with Kondo scattering theory; analysis gives a Kondo temperature 17 K. The magnetoresistance (MR) for the low PO2-grown samples was modeled with a positive part due to weak anti-localization (WAL) from a strong SO interaction, and a negative part due to the Kondo effect. The variation of MR suggests a strong SO interaction for the 10-5 torr sample with HSO = 1.25 T in both field orientations. The WAL effect is smaller for higher PO2-grown samples, where the high-field MR is dominated by the Kondo effect.

  6. A young bipolar outflow from IRAS 15398-3359

    DEFF Research Database (Denmark)

    Bjerkeli, Per; Jørgensen, Jes Kristian; Brinch, Christian

    2016-01-01

    emission towards IRAS 15398-3359. The lineradiative transfer code LIME is used to construct a full 3D model of thesystem taking all relevant components and scales into account. Results: CO, HCO+, and N2H+ aredetected and shown to trace the motions of the outflow. For CO, thecircumstellar envelope...... and the surrounding cloud also have a profoundimpact on the observed line profiles. N2H+ isdetected in the outflow, but is suppressed towards the central region,perhaps because of the competing reaction between CO andH3+ in the densest regions as well as thedestruction of N2H+ by CO.N2D+ is detected in a ridge south...

  7. Electrical conductivity of (La,Sr)MnO3

    International Nuclear Information System (INIS)

    Nowotny, J.; Rekas, M.; Sorrell, C.C.

    1998-01-01

    Defect disorder model for undoped and Sr-doped LaMnO 3 was derived from non-stoichiometry data reported in literature. This model is checked against the electrical conductivity data. The regimes corresponding to oxygen deficit and oxygen excess will be discussed. A good agreement between the random defect model and experimental data of the electrical conductivity was revealed. Copyright (1998) Australasian Ceramic Society

  8. VY Canis Majoris: Observational Studies of the Outflow

    Science.gov (United States)

    Harwit, M.

    2001-12-01

    A number of recent studies carried out with the Infrared Space Observatory, ISO, and the Submillimeter Wave Astronomy Satellite, SWAS, provide new information on the chemical composition of the dust and the geometry of the outflow. With ISO, we have obtained a near-, mid-, and far-infrared spectrum of VY CMa that shows the strong preponderance of amorphous, as contrasted to crystalline, silicates. The sharp spectral slope in the near-infrared suggests the presence also of iron grains. While an excellent theoretical fit to the data is obtained, we emphasize that this is far from unique. A resolution of ambiguities will require a self-consistent model that considers not only radiative transfer, but also plausible elemental abundances, laboratory studies of chemical condensation sequences, and gas dynamics. With SWAS we have obtained a high-resolution spectrum of the 557GHz ground state transition of ortho-water. The spectral profile enables us to rule out a number of outflow geometries proposed in the literature. With ISO we also obtained the intensities and velocity structure of several other spectral lines of water. Most of these lines must be optically thick but effectively thin, a circumstance that permits us to make use of recent gas-dynamic models to locate the radial position in the outflow where individual lines are emitted.

  9. Cerebral venous outflow and cerebrospinal fluid dynamics

    Directory of Open Access Journals (Sweden)

    Clive B. Beggs

    2014-12-01

    Full Text Available In this review, the impact of restricted cerebral venous outflow on the biomechanics of the intracranial fluid system is investigated. The cerebral venous drainage system is often viewed simply as a series of collecting vessels channeling blood back to the heart. However there is growing evidence that it plays an important role in regulating the intracranial fluid system. In particular, there appears to be a link between increased cerebrospinal fluid (CSF pulsatility in the Aqueduct of Sylvius and constricted venous outflow. Constricted venous outflow also appears to inhibit absorption of CSF into the superior sagittal sinus. The compliance of the cortical bridging veins appears to be critical to the behaviour of the intracranial fluid system, with abnormalities at this location implicated in normal pressure hydrocephalus. The compliance associated with these vessels appears to be functional in nature and dependent on the free egress of blood out of the cranium via the extracranial venous drainage pathways. Because constricted venous outflow appears to be linked with increased aqueductal CSF pulsatility, it suggests that inhibited venous blood outflow may be altering the compliance of the cortical bridging veins.

  10. OH outflows in star-forming regions

    International Nuclear Information System (INIS)

    Mirabel, I.F.; Ruiz, A.; Rodriguez, L.F.; Canto, J.; Universidad de Puer; Universidad de Puerto Rico, Rio Piedras; Universidad Nacional Autonoma de Mexico, Mexico City)

    1987-01-01

    The results from a survey for high-velocity OH in molecular outflows in star-forming regions are reported. High-velocity OH was detected in absorption in nine of these regions. When the telescope beam can resolve the outflows, they show similar anisotropic angular distribution as the redshifted and blueshifted CO. The OH transitions are markedly subthermal since for several sources it is found that the radiation that is being absorbed is a background continuum constituted by the cosmic component plus a small Galactic contribution. The absorbing OH appears to trace gas with higher velocities and lower densities than does the CO and, in some cases, provides information on the structure of the outflows at larger distances from the central source. At scales of 0.1 pc, the outflows are elongated in the direction of the steepest density gradient of the ambient cloud, suggesting that the large-scale collimation of the outflow is produced by the density structure of the ambient cloud. 29 references

  11. Acute and chronic effects of dysfunction of right ventricular outflow tract components on right ventricular performance in a porcine model: implications for primary repair of tetralogy of fallot

    NARCIS (Netherlands)

    Bove, Thierry; Bouchez, Stefaan; de Hert, Stefan; Wouters, Patrick; de Somer, Filip; Devos, Daniel; Somers, Pamela; van Nooten, Guido

    2012-01-01

    This study investigates the contribution of infundibular versus pulmonary valve (PV) dysfunction on right ventricular (RV) function in a porcine model. Clinical outcome after repair of tetralogy of Fallot is determined by the adaptation of the right ventricle to the physiological sequelae of the

  12. Mars Atmospheric Conversion to Methane and Water: An Engineering Model of the Sabatier Reactor with Characterization of Ru/Al2O3 for Long Duration Use on Mars

    Science.gov (United States)

    Meier, Anne J.; Shah, Malay; Petersen, Elspeth; Hintze, Paul; Muscatello, Tony

    2017-01-01

    The Atmospheric Processing Module (APM) is a Mars In-Situ Resource Utilization (ISRU) technology designed to demonstrate conversion of the Martian atmosphere into methane and water. The Martian atmosphere consists of approximately 95 carbon dioxide (CO2) and residual argon and nitrogen. APM utilizes cryocoolers for CO2 acquisition from a simulated Martian atmosphere and pressure. The captured CO2 is sublimated and pressurized as a feedstock into the Sabatier reactor, which converts CO2 and hydrogen to methane and water. The Sabatier reaction occurs over a packed bed reactor filled with Ru/Al2O3 pellets. The long duration use of the APM system and catalyst was investigated for future scaling and failure limits. Failure of the catalyst was detected by gas chromatography and temperature sensors on the system. Following this, characterization and experimentation with the catalyst was carried out with analysis including x-ray photoelectron spectroscopy and scanning electron microscopy with elemental dispersive spectroscopy. This paper will discuss results of the catalyst performance, the overall APM Sabatier approach, as well as intrinsic catalyst considerations of the Sabatier reactor performance incorporated into a chemical model.

  13. Zooplankton in the Arctic outflow

    Science.gov (United States)

    Soloviev, K. A.; Dritz, A. V.; Nikishina, A. B.

    2009-04-01

    Climate changes in the Arctic cause the changes in the current system that may have cascading effect on the structure of plankton community and consequently on the interlinked and delicately balanced food web. Zooplankton species are by definition incapable to perform horizontal moving. Their transport is connected with flowing water. There are zooplankton species specific for the definite water masses and they can be used as markers for the different currents. That allows us to consider zooplankton community composition as a result of water mixing in the studied area. Little is known however about the mechanisms by which spatial and temporal variability in advection affect dynamics of local populations. Ice conditions are also very important in the function of pelagic communities. Melting time is the trigger to all "plankton blooming" processes, and the duration of ice-free conditions determines the food web development in the future. Fram Strait is one of the key regions for the Arctic: the cold water outflow comes through it with the East Greenland Current and meets warm Atlantic water, the West Spitsbergen Current, producing complicated hydrological situation. During 2007 and 2008 we investigated the structure functional characteristics of zooplankton community in the Fram Strait region onboard KV "Svalbard" (April 2007, April and May 2008) and RV "Jan Mayen" (May 2007, August 2008). This study was conducted in frame of iAOOS Norway project "Closing the loop", which, in turn, was a part of IPY. During this cruises multidisciplinary investigations were performed, including sea-ice observations, CTD and ADCP profiling, carbon flux, nutrients and primary production measurements, phytoplankton sampling. Zooplankton was collected with the Hydro-Bios WP2 net and MultiNet Zooplankton Sampler, (mouth area 0.25 m2, mesh size 180 um).Samples were taken from the depth strata of 2000-1500, 1500-1000, 1000-500,500-200, 200-100, 100-60, 60-30, 30-0 m. Gut fluorescence

  14. Legendre polynomial modeling for vibrations of guided Lamb waves modes in [001]c, [011]c and [111]c polarized (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (x = 0.29 and 0.33) piezoelectric plates: Physical phenomenon of multiple intertwining of An and Sn modes

    Science.gov (United States)

    Othmani, Cherif; Takali, Farid; Njeh, Anouar

    2017-12-01

    Guided wave devices have recently become one of the most important applications in the industry because such waves are directly related to applications in sensor technology, chemical sensing, agricultural science, fields of bio-sensing and surface acoustic wave (SAW) devices that are used in electronic filters and signal processing. On that account, this numerical investigation aims to study the propagation behavior of guided Lamb waves in a (1-x)Pb(Mg1/3Nb2/3)O3- x PbTiO3 [PMN- x PT] ( x=0.29 or 0.33) piezoelectric single crystal plate. In fact, the PMN- xPT ( x=0.29 or 0.33) piezoelectric crystals are being polarized along [001]c, [011]c and [111]c of the cubic reference directions so that the macroscopic symmetries are tetragonal 4 mm, orthogonal mm2 and rhombohedral 3 m, respectively. Both open- and short-circuit conditions are considered. Here, the Legendre polynomial method is proposed to solve the guided Lamb waves equations. The validity of the proposed method is illustrated by comparison with the ordinary differential equation (ODE). The convergence of this method is discussed. Consequently, the converged results are obtained with very low truncation order M . This constitutes a major advantage of the present method when compared with the other matrix methods. There is cross-crossings among multiple modes for both symmetric ( Sn) and the anti-symmetric ( An) guided Lamb waves propagation. A displacement field has been illustrated to judge whether Sn and An modes cross with each other. Moreover, electric displacement, stress field and electric potential for the open-circuit case were presented for both S0 and A0 Lamb modes.

  15. Evolution of the outflow activity of protostars

    International Nuclear Information System (INIS)

    Bontemps, Sylvain

    1996-01-01

    After a first part describing the formation of low-mass stars (sites of stellar formation, protostellar evolution) and matter outflows from young objects (molecular flows and their origin, optical and radio jets, outflow mechanisms), this research thesis discusses the evolution of molecular flows by reprinting a published article (Evolution of outflow activity around low-mass embedded young stellar objects), and by outlining some remaining issues (differences between clouds of stellar formation, morphological evolution of molecular flows). The author then discusses the continuous radio centimetre emission: origin, systematic search for Class 0 objects by using the VLA (Very Large Array radio interferometer), presentation of a new Class 0 protostar (HH24MMS). The author reports the study of H_2 emission in the infrared: generalities on protostellar shocks, infrared jet by HH24MMS, H_2 emission at 10 microns by using the ISOCAM camera [fr

  16. An MCM modeling study of nitryl chloride (ClNO2) impacts on oxidation, ozone production and nitrogen oxide partitioning in polluted continental outflow

    Science.gov (United States)

    Riedel, T. P.; Wolfe, G. M.; Danas, K. T.; Gilman, J. B.; Kuster, W. C.; Bon, D. M.; Vlasenko, A.; Li, S.-M.; Williams, E. J.; Lerner, B. M.; Veres, P. R.; Roberts, J. M.; Holloway, J. S.; Lefer, B.; Brown, S. S.; Thornton, J. A.

    2014-04-01

    Nitryl chloride (ClNO2) is produced at night by reactions of dinitrogen pentoxide (N2O5) on chloride containing surfaces. ClNO2 is photolyzed during the morning hours after sunrise to liberate highly reactive chlorine atoms (Cl·). This chemistry takes place primarily in polluted environments where the concentrations of N2O5 precursors (nitrogen oxide radicals and ozone) are high, though it likely occurs in remote regions at lower intensities. Recent field measurements have illustrated the potential importance of ClNO2 as a daytime Cl· source and a nighttime NOx reservoir. However, the fate of the Cl· and the overall impact of ClNO2 on regional photochemistry remain poorly constrained by measurements and models. To this end, we have incorporated ClNO2 production, photolysis, and subsequent Cl· reactions into an existing master chemical mechanism (MCM version 3.2) box model framework using observational constraints from the CalNex 2010 field study. Cl· reactions with a set of alkenes and alcohols, and the simplified multiphase chemistry of N2O5, ClNO2, HOCl, ClONO2, and Cl2, none of which are currently part of the MCM, have been added to the mechanism. The presence of ClNO2 produces significant changes to oxidants, ozone, and nitrogen oxide partitioning, relative to model runs excluding ClNO2 formation. From a nighttime maximum of 1.5 ppbv ClNO2, the daytime maximum Cl· concentration reaches 1 × 105 atoms cm-3 at 07:00 model time, reacting mostly with a large suite of volatile organic compounds (VOC) to produce 2.2 times more organic peroxy radicals in the morning than in the absence of ClNO2. In the presence of several ppbv of nitrogen oxide radicals (NOx = NO + NO2), these perturbations lead to similar enhancements in hydrogen oxide radicals (HOx = OH + HO2). Neglecting contributions from HONO, the total integrated daytime radical source is 17% larger when including ClNO2, which leads to a similar enhancement in integrated ozone production of 15%. Detectable

  17. CLUSTERED STAR FORMATION AND OUTFLOWS IN AFGL 2591

    International Nuclear Information System (INIS)

    Sanna, A.; Carrasco-González, C.; Menten, K. M.; Brunthaler, A.; Reid, M. J.; Moscadelli, L.; Rygl, K. L. J.

    2012-01-01

    We report on a detailed study of the water maser kinematics and radio continuum emission toward the most massive and young object in the star-forming region AFGL 2591. Our analysis shows at least two spatial scales of multiple star formation, one projected across 0.1 pc on the sky and another one at about 2000 AU from a ZAMS star of about 38 M ☉ . This young stellar object drives a powerful jet- and wind-driven outflow system with the water masers associated to the outflow walls, previously detected as a limb-brightened cavity in the NIR band. At about 1300 AU to the north of this object a younger protostar drives two bow shocks, outlined by arc-like water maser emission, at 200 AU either side of the source. We have traced the velocity profile of the gas that expands along these arc-like maser structures and compared it with the jet-driven outflow model. This analysis suggests that the ambient medium around the northern protostar is swept up by a jet-driven shock (>66 km s –1 ) and perhaps a lower-velocity (∼10 km s –1 ) wind with an opening angle of about 20° from the jet axis.

  18. CLUSTERED STAR FORMATION AND OUTFLOWS IN AFGL 2591

    Energy Technology Data Exchange (ETDEWEB)

    Sanna, A.; Carrasco-Gonzalez, C.; Menten, K. M.; Brunthaler, A. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany); Reid, M. J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Moscadelli, L. [INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze (Italy); Rygl, K. L. J., E-mail: asanna@mpifr-bonn.mpg.de [IFSI-INAF, Istituto di Fisica dello Spazio Interplanetario, Via del Fosso del Cavaliere 100, 00133 Roma (Italy)

    2012-02-01

    We report on a detailed study of the water maser kinematics and radio continuum emission toward the most massive and young object in the star-forming region AFGL 2591. Our analysis shows at least two spatial scales of multiple star formation, one projected across 0.1 pc on the sky and another one at about 2000 AU from a ZAMS star of about 38 M{sub Sun }. This young stellar object drives a powerful jet- and wind-driven outflow system with the water masers associated to the outflow walls, previously detected as a limb-brightened cavity in the NIR band. At about 1300 AU to the north of this object a younger protostar drives two bow shocks, outlined by arc-like water maser emission, at 200 AU either side of the source. We have traced the velocity profile of the gas that expands along these arc-like maser structures and compared it with the jet-driven outflow model. This analysis suggests that the ambient medium around the northern protostar is swept up by a jet-driven shock (>66 km s{sup -1}) and perhaps a lower-velocity ({approx}10 km s{sup -1}) wind with an opening angle of about 20 Degree-Sign from the jet axis.

  19. Fluid outflows from Venus impact craters - Analysis from Magellan data

    Science.gov (United States)

    Asimow, Paul D.; Wood, John A.

    1992-01-01

    Many impact craters on Venus have unusual outflow features originating in or under the continuous ejecta blankets and continuing downhill into the surrounding terrain. These features clearly resulted from flow of low-viscosity fluids, but the identity of those fluids is not clear. In particular, it should not be assumed a priori that the fluid is an impact melt. A number of candidate processes by which impact events might generate the observed features are considered, and predictions are made concerning the rheological character of flows produce by each mechanism. A sample of outflows was analyzed using Magellan images and a model of unconstrained Bingham plastic flow on inclined planes, leading to estimates of viscosity and yield strength for the flow materials. It is argued that at least two different mechanisms have produced outflows on Venus: an erosive, channel-forming process and a depositional process. The erosive fluid is probably an impact melt, but the depositional fluid may consist of fluidized solid debris, vaporized material, and/or melt.

  20. Raman spectroscopic study of structure and crystallisation behaviour of MoO3-La2O3-B2O3 and MoO3-ZnO-B2O3 glasses

    Science.gov (United States)

    Aleksandrov, L.; Komatsu, T.; Nagamine, K.; Oishi, K.

    2011-03-01

    In this study, we focus on the structure and crystallization behavior of MoO3-La2O3-B2O3 and MoO3-ZnO-B2O3 glasses. Glasses of both systems were prepared by a melt-quenching method. The thermal stability of the glasses was examined using differential thermal anaysis (DTA) measurements, and the crystalline phases formed by heat treatments were identified by X-ray diffraction (XRD) analysis. Raman scattering spectra at room temperature for the glasses and crystallized samples were measured with a laser microscope operated with an Ar+ (wavelength: 488 nm) laser. DTA measurements indicated that the thermal stability against crystallization of the glasses decreases drastically with increasing MoO3 content. XRD analysis confirmed that crystallization at 600°C for 3 h of glass with the nominal composition of 50MoO3-25La2O3-25B2O3 resulted in the formation of monoclinic LaMoBO6. Crystallization of 50ZnO-xMoO3-(50-x)B2O3 glasses formed triclinic α-ZnMoO4 as an initial crystalline phase. Moreover, for 30 mol% MoO3 glass, transmission electron microscopy observations showed the formation of α-ZnMoO4 nanocrystals with a diameter of ~ 5 nm. Raman bands at 860, 930 and 950 cm-1 suggested that the coordination state of Mo6+ ions in the glasses were mainly (MoO4)2- tetrahedral units. Therefore, MoO3-containing glasses have good potential for optical applications.

  1. Vacancy induced metallicity at the CaHfO3/SrTiO3 interface

    KAUST Repository

    Nazir, Safdar; Pulikkotil, J. J.; Schwingenschlö gl, Udo; Singh, Nirpendra

    2011-01-01

    Density functional theory is used to study the electronic properties of the oxide heterointerfaceCaHfO3/SrTiO3. Structural relaxation is carried out with and without O vacancies. As compared to related interfaces, strongly reduced octahedral distortions are found. Stoichiometric interfaces between the wide band gap insulatorsCaHfO3 and SrTiO3 turn out to exhibit an insulating state. However, interface metallicity is introduced by O vacancies, in agreement with experiment. The reduced octahedral distortions and necessity of O deficiency indicate a less complicated mechanism for the creation of the interfacial electron gas.

  2. Vacancy induced metallicity at the CaHfO3/SrTiO3 interface

    KAUST Repository

    Nazir, Safdar

    2011-03-31

    Density functional theory is used to study the electronic properties of the oxide heterointerfaceCaHfO3/SrTiO3. Structural relaxation is carried out with and without O vacancies. As compared to related interfaces, strongly reduced octahedral distortions are found. Stoichiometric interfaces between the wide band gap insulatorsCaHfO3 and SrTiO3 turn out to exhibit an insulating state. However, interface metallicity is introduced by O vacancies, in agreement with experiment. The reduced octahedral distortions and necessity of O deficiency indicate a less complicated mechanism for the creation of the interfacial electron gas.

  3. Metastable honeycomb SrTiO_3/SrIrO_3 heterostructures

    International Nuclear Information System (INIS)

    Anderson, T. J.; Ryu, S.; Podkaminer, J. P.; Ma, Y.; Eom, C. B.; Zhou, H.; Xie, L.; Irwin, J.; Rzchowski, M. S.; Pan, X. Q.

    2016-01-01

    Recent theory predictions of exotic band topologies in (111) honeycomb perovskite SrIrO_3 layers sandwiched between SrTiO_3 have garnered much attention in the condensed matter physics and materials communities. However, perovskite SrIrO_3 film growth in the (111) direction remains unreported, as efforts to synthesize pure SrIrO_3 on (111) perovskite substrates have yielded films with monoclinic symmetry rather than the perovskite structure required by theory predictions. In this study, we report the synthesis of ultra-thin metastable perovskite SrIrO_3 films capped with SrTiO_3 grown on (111) SrTiO_3 substrates by pulsed laser deposition. The atomic structure of the ultra-thin films was examined with scanning transmission electron microscopy (STEM), which suggests a perovskite layering distinct from the bulk SrIrO_3 monoclinic phase. In-plane 3-fold symmetry for the entire heterostructure was confirmed using synchrotron surface X-ray diffraction to measure symmetry equivalent crystal truncation rods. Our findings demonstrate the ability to stabilize (111) honeycomb perovskite SrIrO_3, which provides an experimental avenue to probe the phenomena predicted for this material system.

  4. Influence of Asian outflow on Rishiri Island, northernmost Japan: Application of radon as a tracer for characterizing fetch regions and evaluating a global 3D model

    Science.gov (United States)

    Zhu, Chunmao; Yoshikawa-Inoue, Hisayuki; Matsueda, Hidekadzu; Sawa, Yosuke; Niwa, Yosuke; Wada, Akira; Tanimoto, Hiroshi

    2012-04-01

    Atmospheric 222Rn was monitored from December 2008 to November 2010 on Rishiri Island (45°07‧N, 141°12‧E), northernmost Japan. Seasonal 222Rn variation was characterized by high concentrations from November to February and low concentrations from May to July, caused by the alternation of continental and maritime fetch regions. 222Rn tracer and back trajectory cluster analyses indicated that the predominant continental fetch region was southeastern Siberia and northeastern China. 222Rn emitted from China and South Korea, whose economies are growing rapidly, did not significantly affect the Rishiri site. The major maritime fetch region was the Sea of Okhotsk and the Bering Sea. A global three-dimensional model (NICAM-TM) accurately simulated 222Rn concentrations on Rishiri Island and in the seasonal fetch regions. The time series of 222Rn data will make it possible to evaluate the sources and sinks of atmospheric greenhouse gases being monitored at Rishiri Island, which complements other sites in the Asia-Pacific rim region, and to validate model simulations used to examine trans-boundary air pollution.

  5. Wind influence on a coastal buoyant outflow

    Science.gov (United States)

    Whitney, Michael M.; Garvine, Richard W.

    2005-03-01

    This paper investigates the interplay between river discharge and winds in forcing coastal buoyant outflows. During light winds a plume influenced by the Earth's rotation will flow down shelf (in the direction of Kelvin wave propagation) as a slender buoyancy-driven coastal current. Downwelling favorable winds augment this down-shelf flow, narrow the plume, and mix the water column. Upwelling favorable winds drive currents that counter the buoyancy-driven flow, spread plume waters offshore, and rapidly mix buoyant waters. Two criteria are developed to assess the wind influence on a buoyant outflow. The wind strength index (Ws) determines whether a plume's along-shelf flow is in a wind-driven or buoyancy-driven state. Ws is the ratio of the wind-driven and buoyancy-driven along-shelf velocities. Wind influence on across-shelf plume structure is rated with a timescale (ttilt) for the isopycnal tilting caused by wind-driven Ekman circulation. These criteria are used to characterize wind influence on the Delaware Coastal Current and can be applied to other coastal buoyant outflows. The Delaware buoyant outflow is simulated for springtime high-river discharge conditions. Simulation results and Ws values reveal that the coastal current is buoyancy-driven most of the time (∣Ws∣ Wind events, however, overwhelm the buoyancy-driven flow (∣Ws∣ > 1) several times during the high-discharge period. Strong upwelling events reverse the buoyant outflow; they constitute an important mechanism for transporting fresh water up shelf. Across-shelf plume structure is more sensitive to wind influence than the along-shelf flow. Values of ttilt indicate that moderate or strong winds persisting throughout a day can modify plume width significantly. Plume widening during upwelling events is accompanied by mixing that can erase the buoyant outflow.

  6. Explosive Outflows from Forming Massive Stars

    OpenAIRE

    Bally, J.; Ginsburg, A.; Kasliwal, M. M.

    2016-01-01

    AO imaging of the near IR [Fe ii] and H_2 lines and ALMA CO J = 2 − 1 data confirms the explosive nature of the BN/KL outflow in Orion. N-body interactions in compact groups may be responsible for the production of powerful, explosive protostellar outflows and luminous infrared flares. The Orion event may have been triggered by a protostellar merger. First results of a search for Orion-like events in 200 nearby galaxies with the SPitzer InfraRed Intensive Transients Survey (SPIRITS) are brief...

  7. Fading AGN Candidates: AGN Histories and Outflow Signatures

    Energy Technology Data Exchange (ETDEWEB)

    Keel, William C.; Maksym, W. Peter [Department of Physics and Astronomy, University of Alabama, Box 870324, Tuscaloosa, AL 35487 (United States); Lintott, Chris J. [Astrophysics, Oxford University and Adler Planetarium, 1300 S. Lakeshore Drive, Chicago, IL 60605 (United States); Bennert, Vardha N.; Scott, Bryan; Showley, Charles; Flatland, Kelsi [Physics Department, California Polytechnic State University, San Luis Obispo, CA 93407 (United States); Chojnowski, S. Drew [Department of Astronomy, New Mexico State University, P.O. Box 30001, MSC 4500, Las Cruces, NM 88003-8001 (United States); Moiseev, Alexei; Smirnova, Aleksandrina [Special Astrophysical Observatory, Russian Academy of Sciences, Nizhny Arkhyz, 369167 (Russian Federation); Schawinski, Kevin; Sartori, Lia F. [Institute for Astronomy, ETH Zürich, Wolfgang-Pauli-Straße 27, CH-8093 Zurich (Switzerland); Urry, C. Megan [Department of Physics, Yale University, P.O. Box 208120, New Haven, CT 06520-8120 (United States); Pancoast, Anna [Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Schirmer, Mischa, E-mail: wkeel@ua.edu [Gemini Observatory, La Serena (Chile)

    2017-02-01

    We consider the energy budgets and radiative history of eight fading active galactic nuclei (AGNs), identified from an energy shortfall between the requirements to ionize very extended (radius > 10 kpc) ionized clouds and the luminosity of the nucleus as we view it directly. All show evidence of significant fading on timescales of ≈50,000 yr. We explore the use of minimum ionizing luminosity Q {sub ion} derived from photoionization balance in the brightest pixels in H α at each projected radius. Tests using presumably constant Palomar–Green QSOs, and one of our targets with detailed photoionization modeling, suggest that we can derive useful histories of individual AGNs, with the caveat that the minimum ionizing luminosity is always an underestimate and subject to uncertainties about fine structure in the ionized material. These consistency tests suggest that the degree of underestimation from the upper envelope of reconstructed Q {sub ion} values is roughly constant for a given object and therefore does not prevent such derivation. The AGNs in our sample show a range of behaviors, with rapid drops and standstills; the common feature is a rapid drop in the last ≈2×10{sup 4} yr before the direct view of the nucleus. The e -folding timescales for ionizing luminosity are mostly in the thousands of years, with a few episodes as short as 400 yr. In the limit of largely obscured AGNs, we find additional evidence for fading from the shortfall between even the lower limits from recombination balance and the maximum luminosities derived from far-infrared fluxes. We compare these long-term light curves, and the occurrence of these fading objects among all optically identified AGNs, to simulations of AGN accretion; the strongest variations over these timespans are seen in models with strong and local (parsec-scale) feedback. We present Gemini integral-field optical spectroscopy, which shows a very limited role for outflows in these ionized structures. While rings and

  8. Fading AGN Candidates: AGN Histories and Outflow Signatures

    International Nuclear Information System (INIS)

    Keel, William C.; Maksym, W. Peter; Lintott, Chris J.; Bennert, Vardha N.; Scott, Bryan; Showley, Charles; Flatland, Kelsi; Chojnowski, S. Drew; Moiseev, Alexei; Smirnova, Aleksandrina; Schawinski, Kevin; Sartori, Lia F.; Urry, C. Megan; Pancoast, Anna; Schirmer, Mischa

    2017-01-01

    We consider the energy budgets and radiative history of eight fading active galactic nuclei (AGNs), identified from an energy shortfall between the requirements to ionize very extended (radius > 10 kpc) ionized clouds and the luminosity of the nucleus as we view it directly. All show evidence of significant fading on timescales of ≈50,000 yr. We explore the use of minimum ionizing luminosity Q ion derived from photoionization balance in the brightest pixels in H α at each projected radius. Tests using presumably constant Palomar–Green QSOs, and one of our targets with detailed photoionization modeling, suggest that we can derive useful histories of individual AGNs, with the caveat that the minimum ionizing luminosity is always an underestimate and subject to uncertainties about fine structure in the ionized material. These consistency tests suggest that the degree of underestimation from the upper envelope of reconstructed Q ion values is roughly constant for a given object and therefore does not prevent such derivation. The AGNs in our sample show a range of behaviors, with rapid drops and standstills; the common feature is a rapid drop in the last ≈2×10 4 yr before the direct view of the nucleus. The e -folding timescales for ionizing luminosity are mostly in the thousands of years, with a few episodes as short as 400 yr. In the limit of largely obscured AGNs, we find additional evidence for fading from the shortfall between even the lower limits from recombination balance and the maximum luminosities derived from far-infrared fluxes. We compare these long-term light curves, and the occurrence of these fading objects among all optically identified AGNs, to simulations of AGN accretion; the strongest variations over these timespans are seen in models with strong and local (parsec-scale) feedback. We present Gemini integral-field optical spectroscopy, which shows a very limited role for outflows in these ionized structures. While rings and loops of emission

  9. Temporal and spatial variability in the aviation NOx-related O3 impact

    International Nuclear Information System (INIS)

    Gilmore, Christopher K; Barrett, Steven R H; Koo, Jamin; Wang, Qiqi

    2013-01-01

    Aviation NO x emissions promote tropospheric ozone formation, which is linked to climate warming and adverse health effects. Modeling studies have quantified the relative impact of aviation NO x on O 3 in large geographic regions. As these studies have applied forward modeling techniques, it has not been possible to attribute O 3 formation to individual flights. Here we apply the adjoint of the global chemistry–transport model GEOS-Chem to assess the temporal and spatial variability in O 3 production due to aviation NO x emissions, which is the first application of an adjoint to this problem. We find that total aviation NO x emitted in October causes 40% more O 3 than in April and that Pacific aviation emissions could cause 4–5 times more tropospheric O 3 per unit NO x than European or North American emissions. Using this sensitivity approach, the O 3 burden attributable to 83 000 unique scheduled civil flights is computed individually. We find that the ten highest total O 3 -producing flights have origins or destinations in New Zealand or Australia. The top ranked O 3 -producing flights normalized by fuel burn cause 157 times more normalized O 3 formation than the bottom ranked ones. These results show significant spatial and temporal heterogeneity in environmental impacts of aviation NO x emissions. (letter)

  10. Resistance switching at the interface of LaAlO3/SrTiO3

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Zhao, J.L.; Sun, J.R.

    2010-01-01

    At the interface of LaAlO3/SrTiO3 with film thickness of 3 unit cells or greater, a reproducible electric-field-induced bipolar resistance switching of the interfacial conduction is observed on nanometer scale by a biased conducting atomic force microscopy under vacuum environment. The switching ...

  11. Efficient photodecomposition of herbicide imazapyr over mesoporous Ga2O3-TiO2 nanocomposites.

    Science.gov (United States)

    Ismail, Adel A; Abdelfattah, Ibrahim; Faisal, M; Helal, Ahmed

    2018-01-15

    The unabated release of herbicide imazapyr into the soil and groundwater led to crop destruction and several pollution-related concerns. In this contribution, heterogeneous photocatalytic technique was employed utilizing mesoporous Ga 2 O 3 -TiO 2 nanocomposites for degrading imazapyr herbicide as a model pollutant molecule. Mesoporous Ga 2 O 3 -TiO 2 nanocomposites with varied Ga 2 O 3 contents (0-5wt%) were synthesized through sol-gel process. XRD and Raman spectra exhibited extremely crystalline anatase TiO 2 phase at low Ga 2 O 3 content which gradually reduced with the increase of Ga 2 O 3 content. TEM images display uniform TiO 2 particles (10±2nm) with mesoporous structure. The mesoporous TiO 2 exhibits large surface areas of 167m 2 g -1 , diminished to 108m 2 g -1 upon 5% Ga 2 O 3 incorporation, with tunable mesopore diameter in the range of 3-9nm. The photocatalytic efficiency of synthesized Ga 2 O 3 -TiO 2 nanocomposites was assessed by degrading imazapyr herbicide and comparing with commercial photocatalyst UV-100 and mesoporous Ga 2 O 3 under UV illumination. 0.1% Ga 2 O 3 -TiO 2 nanocomposite is considered the optimum photocatalyst, which degrades 98% of imazapyr herbicide within 180min. Also, the photodegradation rate of imazapyr using 0.1% Ga 2 O 3 -TiO 2 nanocomposite is nearly 10 and 3-fold higher than that of mesoporous Ga 2 O 3 and UV-100, respectively. The high photonic efficiency and long-term stability of the mesoporous Ga 2 O 3 -TiO 2 nanocomposites are ascribed to its stronger oxidative capability in comparison with either mesoporous TiO 2 , Ga 2 O 3 or commercial UV-100. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. THE SINS/zC-SINF SURVEY of z {approx} 2 GALAXY KINEMATICS: OUTFLOW PROPERTIES

    Energy Technology Data Exchange (ETDEWEB)

    Newman, Sarah F.; Genzel, Reinhard [Department of Astronomy, Campbell Hall, University of California, Berkeley, CA 94720 (United States); Foerster-Schreiber, Natascha M.; Buschkamp, Peter; Davies, Ric; Eisenhauer, Frank; Kurk, Jaron; Lutz, Dieter [Max-Planck-Institut fuer extraterrestrische Physik (MPE), Giessenbachstr.1, D-85748 Garching (Germany); Griffin, Kristen Shapiro [Space Sciences Research Group, Northrop Grumman Aerospace Systems, Redondo Beach, CA 90278 (United States); Mancini, Chiara; Renzini, Alvio [Osservatorio Astronomico di Padova, Vicolo dellOsservatorio 5, Padova, I-35122 (Italy); Lilly, Simon J.; Carollo, C. Marcella; Peng, Yingjie [Institute of Astronomy, Department of Physics, Eidgenoessische Technische Hochschule, ETH Zuerich, CH-8093 (Switzerland); Bouche, Nicolas [Institut de Recherche en Astrophysique et Planetologie (IRAP), Universite de Toulouse, UPS-OMP, IRAP, 14, avenue Edouard Berlin, F-31400 Toulouse (France); Burkert, Andreas [Department fuer Physik, Universitaets-Sternwarte Ludwig-Maximilians-Universitaet (USM), Scheinerstr. 1, Muenchen, D-81679 (Germany); Cresci, Giovanni [Istituto Nazionale di AstrofisicaOsservatorio Astronomico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Genel, Shy [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hicks, Erin K. S. [Department of Astronomy, University of Washington, Box 351580, U.W., Seattle, WA 98195-1580 (United States); Naab, Thorsten, E-mail: sfnewman@berkeley.edu [Max-Planck Institute for Astrophysics, Karl Schwarzschildstrasse 1, D-85748 Garching (Germany); and others

    2012-12-10

    Using SINFONI H{alpha}, [N II], and [S II] AO data of 27 z {approx} 2 star-forming galaxies (SFGs) from the SINS and zC-SINF surveys, we explore the dependence of outflow strength (via the broad flux fraction) on various galaxy parameters. For galaxies that have evidence for strong outflows, we find that the broad emission is spatially extended to at least the half-light radius ({approx}a few kpc). Decomposition of the [S II] doublet into broad and narrow components suggests that this outflowing gas probably has a density of {approx}10-100 cm{sup -3}, less than that of the star-forming gas (600 cm{sup -3}). There is a strong correlation of the H{alpha} broad flux fraction with the star formation surface density of the galaxy, with an apparent threshold for strong outflows occurring at 1 M{sub Sun} yr{sup -1} kpc{sup -2}. Above this threshold, we find that SFGs with log m{sub *} > 10 have similar or perhaps greater wind mass-loading factors ({eta} = M-dot{sub out}/SFR) and faster outflow velocities than lower mass SFGs, suggesting that the majority of outflowing gas at z {approx} 2 may derive from high-mass SFGs. The mass-loading factor is also correlated with the star formation rate (SFR), galaxy size, and inclination, such that smaller, more star-forming, and face-on galaxies launch more powerful outflows. We propose that the observed threshold for strong outflows and the observed mass loading of these winds can be explained by a simple model wherein break-out of winds is governed by pressure balance in the disk.

  13. Thermoluminescence of LaAlO3

    International Nuclear Information System (INIS)

    Morales H, A.; Zarate M, J.; Rivera M, T.; Azorin N, J.

    2015-10-01

    In this paper the thermoluminescent properties of doped lanthanum aluminate (LaAlO 3 ) with dysprosium ion (Dy) were studied. The thermoluminescence characteristics in the samples were obtained using an ultraviolet radiation of 220 nm. The LaAlO 3 :Dy samples were prepared by the modified Pechini method (Spray Dryer). The structural and morphological characterization was obtained by X-ray diffraction (XRD) and scanning electron microscopy (Sem) techniques respectively. The size particle composing the agglomerate was determined by Sem, agglomerated particles composed size of 2μm were observed. The thermoluminescence response of LaAlO 3 :Dy was compared with that obtained with the undoped sample. Thermoluminescence brightness curves of LaAlO 3 :Dy showed a peak centered at 185 grades C. Sensitivity of doped sample was greater, about 100 times compared with the undoped sample. Thermoluminescence response in function of the wavelength showed a maximum at 220 nm. Also the fading in thermoluminescence response was studied. (Author)

  14. Martian outflow channels: How did their source aquifers form, and why did they drain so rapidly?

    Science.gov (United States)

    Rodriguez, J Alexis P; Kargel, Jeffrey S; Baker, Victor R; Gulick, Virginia C; Berman, Daniel C; Fairén, Alberto G; Linares, Rogelio; Zarroca, Mario; Yan, Jianguo; Miyamoto, Hideaki; Glines, Natalie

    2015-09-08

    Catastrophic floods generated ~3.2 Ga by rapid groundwater evacuation scoured the Solar System's most voluminous channels, the southern circum-Chryse outflow channels. Based on Viking Orbiter data analysis, it was hypothesized that these outflows emanated from a global Hesperian cryosphere-confined aquifer that was infused by south polar meltwater infiltration into the planet's upper crust. In this model, the outflow channels formed along zones of superlithostatic pressure generated by pronounced elevation differences around the Highland-Lowland Dichotomy Boundary. However, the restricted geographic location of the channels indicates that these conditions were not uniform. Furthermore, some outflow channel sources are too high to have been fed by south polar basal melting. Using more recent mission data, we argue that during the Late Noachian fluvial and glacial sediments were deposited into a clastic wedge within a paleo-basin located in the southern circum-Chryse region, which at the time was completely submerged under a primordial northern plains ocean [corrected]. Subsequent Late Hesperian outflow channels were sourced from within these geologic materials and formed by gigantic groundwater outbursts driven by an elevated hydraulic head from the Valles Marineris region. Thus, our findings link the formation of the southern circum-Chryse outflow channels to ancient marine, glacial, and fluvial erosion and sedimentation.

  15. Dehydration of MoO 3 · 2H 2O: A Neutron Thermodiffractometry Study

    Science.gov (United States)

    Boudjada, N.; Rodríguez-Carvajal, J.; Anne, M.; Figlarz, M.

    1993-07-01

    A neutron powder thermodiffractometric study of the dehydration reactions MoO 3 · 2H 2O → MoO 3 · H 2O → MoO 3 has been carried out in order to investigate the topotactic mechanism previously reported. The topotactic character of the reactions is confirmed and an approximate model for the crystal structure of MoO 3 · H 2O is proposed. Quantitative data about the relative amount of the existing phases, as a function of temperature, have been deduced from multiphase profile analysis. The anomalous behavior of the cell parameters of MoO 3 · H 2O, at about 100°C, indicates the existence of a new phase transition. The evolution of the crystallite size of MoO 3 has also been obtained from the broadening of Bragg reflections at high temperature. The preferred direction of growth is along [021].

  16. PROTOSTELLAR OUTFLOW EVOLUTION IN TURBULENT ENVIRONMENTS

    International Nuclear Information System (INIS)

    Cunningham, Andrew J.; Frank, Adam; Carroll, Jonathan; Blackman, Eric G.; Quillen, Alice C.

    2009-01-01

    The link between turbulence in star-forming environments and protostellar jets remains controversial. To explore issues of turbulence and fossil cavities driven by young stellar outflows, we present a series of numerical simulations tracking the evolution of transient protostellar jets driven into a turbulent medium. Our simulations show both the effect of turbulence on outflow structures and, conversely, the effect of outflows on the ambient turbulence. We demonstrate how turbulence will lead to strong modifications in jet morphology. More importantly, we demonstrate that individual transient outflows have the capacity to re-energize decaying turbulence. Our simulations support a scenario in which the directed energy/momentum associated with cavities is randomized as the cavities are disrupted by dynamical instabilities seeded by the ambient turbulence. Consideration of the energy power spectra of the simulations reveals that the disruption of the cavities powers an energy cascade consistent with Burgers'-type turbulence and produces a driving scale length associated with the cavity propagation length. We conclude that fossil cavities interacting either with a turbulent medium or with other cavities have the capacity to sustain or create turbulent flows in star-forming environments. In the last section, we contrast our work and its conclusions with previous studies which claim that jets cannot be the source of turbulence.

  17. Alignment between Protostellar Outflows and Filamentary Structure

    Energy Technology Data Exchange (ETDEWEB)

    Stephens, Ian W.; Dunham, Michael M.; Myers, Philip C.; Pokhrel, Riwaj; Sadavoy, Sarah I.; Lee, Katherine I.; Goodman, Alyssa A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA (United States); Vorobyov, Eduard I. [Institute of Fluid Mechanics and Heat Transfer, TU Wien, Vienna, A-1060 (Austria); Tobin, John J. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks Street, Norman, OK 73019 (United States); Pineda, Jaime E. [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching (Germany); Offner, Stella S. R. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Kristensen, Lars E. [Centre for Star and Planet Formation, Niels Bohr Institute and Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K (Denmark); Jørgensen, Jes K. [Niels Bohr Institute and Center for Star and Planet Formation, Copenhagen University, DK-1350 Copenhagen K. (Denmark); Bourke, Tyler L. [SKA Organization, Jodrell Bank Observatory, Lower Withington, Macclesfield, Cheshire SK11 9DL (United Kingdom); Arce, Héctor G. [Department of Astronomy, Yale University, New Haven, CT 06520 (United States); Plunkett, Adele L., E-mail: ian.stephens@cfa.harvard.edu [European Southern Observatory, Av. Alonso de Cordova 3107, Vitacura, Santiago de Chile (Chile)

    2017-09-01

    We present new Submillimeter Array (SMA) observations of CO(2–1) outflows toward young, embedded protostars in the Perseus molecular cloud as part of the Mass Assembly of Stellar Systems and their Evolution with the SMA (MASSES) survey. For 57 Perseus protostars, we characterize the orientation of the outflow angles and compare them with the orientation of the local filaments as derived from Herschel observations. We find that the relative angles between outflows and filaments are inconsistent with purely parallel or purely perpendicular distributions. Instead, the observed distribution of outflow-filament angles are more consistent with either randomly aligned angles or a mix of projected parallel and perpendicular angles. A mix of parallel and perpendicular angles requires perpendicular alignment to be more common by a factor of ∼3. Our results show that the observed distributions probably hold regardless of the protostar’s multiplicity, age, or the host core’s opacity. These observations indicate that the angular momentum axis of a protostar may be independent of the large-scale structure. We discuss the significance of independent protostellar rotation axes in the general picture of filament-based star formation.

  18. Electronic properties and surface reactivity of SrO-terminated SrTiO3 and SrO-terminated iron-doped SrTiO3.

    Science.gov (United States)

    Staykov, Aleksandar; Tellez, Helena; Druce, John; Wu, Ji; Ishihara, Tatsumi; Kilner, John

    2018-01-01

    Surface reactivity and near-surface electronic properties of SrO-terminated SrTiO 3 and iron doped SrTiO 3 were studied with first principle methods. We have investigated the density of states (DOS) of bulk SrTiO 3 and compared it to DOS of iron-doped SrTiO 3 with different oxidation states of iron corresponding to varying oxygen vacancy content within the bulk material. The obtained bulk DOS was compared to near-surface DOS, i.e. surface states, for both SrO-terminated surface of SrTiO 3 and iron-doped SrTiO 3 . Electron density plots and electron density distribution through the entire slab models were investigated in order to understand the origin of surface electrons that can participate in oxygen reduction reaction. Furthermore, we have compared oxygen reduction reactions at elevated temperatures for SrO surfaces with and without oxygen vacancies. Our calculations demonstrate that the conduction band, which is formed mainly by the d-states of Ti, and Fe-induced states within the band gap of SrTiO 3 , are accessible only on TiO 2 terminated SrTiO 3 surface while the SrO-terminated surface introduces a tunneling barrier for the electrons populating the conductance band. First principle molecular dynamics demonstrated that at elevated temperatures the surface oxygen vacancies are essential for the oxygen reduction reaction.

  19. Hydrothermal syntheses and characterization of two layered molybdenum selenites, Rb2(MoO3)3SeO3 and Tl2(MoO3)3SeO3

    International Nuclear Information System (INIS)

    Dussack, L.L.; Harrison, W.T.A.; Jacobson, A.J.

    1996-01-01

    The hydrothermal syntheses of Rb 2 (MoO 3 ) 3 SeO 3 , and Tl 2 (MoO 3 ) 3 SeO 3 are described. These compounds have structures built up from hexagonal-WO 3 -type sheets and are isostructural with the previously reported Cs 2 (MoO 3 ) 3 SeO 3 and (NH 4 ) 2 (MoO 3 ) 3 SeO 3 . Powder X-ray, thermogravimetric, and spectroscopic data are presented and discussed

  20. Configuring calendar variation based on time series regression method for forecasting of monthly currency inflow and outflow in Central Java

    Science.gov (United States)

    Setiawan, Suhartono, Ahmad, Imam Safawi; Rahmawati, Noorgam Ika

    2015-12-01

    Bank Indonesia (BI) as the central bank of Republic Indonesiahas a single overarching objective to establish and maintain rupiah stability. This objective could be achieved by monitoring traffic of inflow and outflow money currency. Inflow and outflow are related to stock and distribution of money currency around Indonesia territory. It will effect of economic activities. Economic activities of Indonesia,as one of Moslem country, absolutely related to Islamic Calendar (lunar calendar), that different with Gregorian calendar. This research aims to forecast the inflow and outflow money currency of Representative Office (RO) of BI Semarang Central Java region. The results of the analysis shows that the characteristics of inflow and outflow money currency influenced by the effects of the calendar variations, that is the day of Eid al-Fitr (moslem holyday) as well as seasonal patterns. In addition, the period of a certain week during Eid al-Fitr also affect the increase of inflow and outflow money currency. The best model based on the value of the smallestRoot Mean Square Error (RMSE) for inflow data is ARIMA model. While the best model for predicting the outflow data in RO of BI Semarang is ARIMAX model or Time Series Regression, because both of them have the same model. The results forecast in a period of 2015 shows an increase of inflow money currency happened in August, while the increase in outflow money currency happened in July.

  1. Carbonization kinetics of La2O3-Mo cathode materials

    International Nuclear Information System (INIS)

    Jinshu, W.; Meiling, Z.; Tieyong, Z.; Jiuxing, Z.; Zuoren, N.

    2001-01-01

    The carbonization kinetics of La 2 O 3 -Mo cathode materials has been studied by thermal analysis method. Three-stage model of the carbonization has been presented in this paper. The carbonization rate is initially controlled by chemical reaction, then controlled by chemical reaction mixed with diffusion, finally controlled by diffusion. After the initial experimental data are processed according to this model, the correlation coefficients of the kinetic curves are satisfactory. The apparent activation energy of carbonization of La 2 O 3 -Mo cathode materials has been obtained. At the same time, we have deduced the empirical expressions of the amount of weight increased per unit area after carbonization, temperature and time in the temperature range 1393 K - 1493 K. (author)

  2. Determination of oxygen nonstoichiometry and diffusivity in mixed conducting oxides by oxygen Coulometric titration. II. Oxygen nonstoichiometry and defect model for La0.8Sr0.2CoO3-d

    NARCIS (Netherlands)

    Lankhorst, M.H.R.; Lankhorst, M.H.R.; Bouwmeester, Henricus J.M.

    1997-01-01

    The oxygen nonstoichiometry of La0.8Sr0.2CoO3-delta has been determined as a function of oxygen partial pressure and temperature using a high-temperature coulometric titration cell. For each measured value of the oxygen chemical potential, the oxygen nonstoichiometry is found to be nearly

  3. Quasi-steady state power law model for flow of (La0·85Sr0·15)0·9MnO3 ceramic slurry in tape casting

    DEFF Research Database (Denmark)

    Jabbari, M; Bulatova, R; Hattel, J H

    2013-01-01

    work, the flow in the doctor blade region of a slurry containing (La0?85Sr0?15)0?9MnO3 (LSM) material is described with a simple quasi-steady momentum equation in combination with an Ostwald–de Waele power law constitutive equation. Based on rheometer experiments, the constants in the Ostwald–de Waele...

  4. Raman spectra of MgSiO3 . 10% Al2O3-perovskite at various pressures and temperatures

    International Nuclear Information System (INIS)

    Liu Lingun; Irifune, T.

    1995-01-01

    Variations of Raman spectra of MgSiO 3 . 10% Al 2 O 3 -perovskite were investigated up to about 270 kbar at room temperature and in the range 108-425 K at atmospheric pressure. Like MgSiO 3 -perovskite, the Raman frequencies of MgSiO 3 . 10% Al 2 O 3 -perovskite increase nonlinearly with increasing pressure and decrease linearly with increasing temperature within the experimental uncertainties and the range investigated. A comparison of these data with those of MgSiO 3 -perovskite suggests that MgSiO 3 . 10% Al 2 O 3 -perovskite is slightly more compressible than MgSiO 3 -perovskite, and that the volume thermal expansion for MgSiO 3 . 10% Al 2 O 3 -perovskite is also slightly greater than that for MgSiO 3 -perovskite. (orig.)

  5. Raman and Fluorescence Spectroscopy of CeO2, Er2O3, Nd2O3, Tm2O3, Yb2O3, La2O3, and Tb4O7

    Directory of Open Access Journals (Sweden)

    Jianlan Cui

    2015-01-01

    Full Text Available To better understand and ascertain the mechanisms of flotation reagent interaction with rare earth (RE minerals, it is necessary to determine the physical and chemical properties of the constituent components. Seven rare earth oxides (CeO2, Er2O3, Nd2O3, Tm2O3, Yb2O3, La2O3, and Tb4O7 that cover the rare earth elements (REEs from light to heavy REEs have been investigated using Raman spectroscopy. Multiple laser sources (wavelengths of 325 nm, 442 nm, 514 nm, and 632.8 nm for the Raman shift ranges from 100 cm−1 to 5000 cm−1 of these excitations were used for each individual rare earth oxide. Raman shifts and fluorescence emission have been identified. Theoretical energy levels for Er, Nd, and Yb were used for the interpretation of fluorescence emission. The experimental results showed good agreement with the theoretical calculation for Er2O3 and Nd2O3. Additional fluorescence emission was observed with Yb2O3 that did not fit the reported energy level diagram. Tb4O7 was observed undergoing laser induced changes during examination.

  6. Numerical Study on Outflows in Seyfert Galaxies I: Narrow Line Region Outflows in NGC 4151

    Energy Technology Data Exchange (ETDEWEB)

    Mou, Guobin; Wang, Tinggui; Yang, Chenwei, E-mail: gbmou@ustc.edu.cn [CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei 230026 (China)

    2017-07-20

    The origin of narrow line region (NLR) outflows remains unknown. In this paper, we explore the scenario in which these outflows are circumnuclear clouds driven by energetic accretion disk winds. We choose the well-studied nearby Seyfert galaxy NGC 4151 as an example. By performing 3D hydrodynamical simulations, we are able to reproduce the radial distributions of velocity, mass outflow rate, and kinetic luminosity of NLR outflows in the inner 100 pc deduced from spatial resolved spectroscopic observations. The demanded kinetic luminosity of disk winds is about two orders of magnitude higher than that inferred from the NLR outflows, but is close to the ultrafast outflows (UFO) detected in the X-ray spectrum and a few times lower than the bolometric luminosity of the Seyfert. Our simulations imply that the scenario is viable for NGC 4151. The existence of the underlying disk winds can be confirmed by their impacts on higher density ISM, e.g., shock excitation signs, and the pressure in NLR.

  7. Numerical Study on Outflows in Seyfert Galaxies I: Narrow Line Region Outflows in NGC 4151

    International Nuclear Information System (INIS)

    Mou, Guobin; Wang, Tinggui; Yang, Chenwei

    2017-01-01

    The origin of narrow line region (NLR) outflows remains unknown. In this paper, we explore the scenario in which these outflows are circumnuclear clouds driven by energetic accretion disk winds. We choose the well-studied nearby Seyfert galaxy NGC 4151 as an example. By performing 3D hydrodynamical simulations, we are able to reproduce the radial distributions of velocity, mass outflow rate, and kinetic luminosity of NLR outflows in the inner 100 pc deduced from spatial resolved spectroscopic observations. The demanded kinetic luminosity of disk winds is about two orders of magnitude higher than that inferred from the NLR outflows, but is close to the ultrafast outflows (UFO) detected in the X-ray spectrum and a few times lower than the bolometric luminosity of the Seyfert. Our simulations imply that the scenario is viable for NGC 4151. The existence of the underlying disk winds can be confirmed by their impacts on higher density ISM, e.g., shock excitation signs, and the pressure in NLR.

  8. Numerical Study on Outflows in Seyfert Galaxies I: Narrow Line Region Outflows in NGC 4151

    Science.gov (United States)

    Mou, Guobin; Wang, Tinggui; Yang, Chenwei

    2017-07-01

    The origin of narrow line region (NLR) outflows remains unknown. In this paper, we explore the scenario in which these outflows are circumnuclear clouds driven by energetic accretion disk winds. We choose the well-studied nearby Seyfert galaxy NGC 4151 as an example. By performing 3D hydrodynamical simulations, we are able to reproduce the radial distributions of velocity, mass outflow rate, and kinetic luminosity of NLR outflows in the inner 100 pc deduced from spatial resolved spectroscopic observations. The demanded kinetic luminosity of disk winds is about two orders of magnitude higher than that inferred from the NLR outflows, but is close to the ultrafast outflows (UFO) detected in the X-ray spectrum and a few times lower than the bolometric luminosity of the Seyfert. Our simulations imply that the scenario is viable for NGC 4151. The existence of the underlying disk winds can be confirmed by their impacts on higher density ISM, e.g., shock excitation signs, and the pressure in NLR.

  9. Chemical quenching of positronium in Fe2O3/Al2O3 catalysts

    International Nuclear Information System (INIS)

    Li, C.; Zhang, H.J.; Chen, Z.Q.

    2010-01-01

    Fe 2 O 3 /Al 2 O 3 catalysts were prepared by solid state reaction method using α-Fe 2 O 3 and γ-Al 2 O 3 nano powders. The microstructure and surface properties of the catalyst were studied using positron lifetime and coincidence Doppler broadening annihilation radiation measurements. The positron lifetime spectrum shows four components. The two long lifetimes τ 3 and τ 4 are attributed to positronium annihilation in two types of pores distributed inside Al 2 O 3 grain and between the grains, respectively. With increasing Fe 2 O 3 content from 3 wt% to 40 wt%, the lifetime τ 3 keeps nearly unchanged, while the longest lifetime τ 4 shows decrease from 96 ns to 64 ns. Its intensity decreases drastically from 24% to less than 8%. The Doppler broadening S parameter shows also a continuous decrease. Further analysis of the Doppler broadening spectra reveals a decrease in the p-Ps intensity with increasing Fe 2 O 3 content, which rules out the possibility of spin-conversion of positronium. Therefore the decrease of τ 4 is most probably due to the chemical quenching reaction of positronium with Fe ions on the surface of the large pores.

  10. Chemical quenching of positronium in Fe 2O 3/Al 2O 3 catalysts

    Science.gov (United States)

    Li, C.; Zhang, H. J.; Chen, Z. Q.

    2010-09-01

    Fe 2O 3/Al 2O 3 catalysts were prepared by solid state reaction method using α-Fe 2O 3 and γ-Al 2O 3 nano powders. The microstructure and surface properties of the catalyst were studied using positron lifetime and coincidence Doppler broadening annihilation radiation measurements. The positron lifetime spectrum shows four components. The two long lifetimes τ3 and τ4 are attributed to positronium annihilation in two types of pores distributed inside Al 2O 3 grain and between the grains, respectively. With increasing Fe 2O 3 content from 3 wt% to 40 wt%, the lifetime τ3 keeps nearly unchanged, while the longest lifetime τ4 shows decrease from 96 ns to 64 ns. Its intensity decreases drastically from 24% to less than 8%. The Doppler broadening S parameter shows also a continuous decrease. Further analysis of the Doppler broadening spectra reveals a decrease in the p-Ps intensity with increasing Fe 2O 3 content, which rules out the possibility of spin-conversion of positronium. Therefore the decrease of τ4 is most probably due to the chemical quenching reaction of positronium with Fe ions on the surface of the large pores.

  11. Neutron irradiation damage in Al2O3 and Y2O3

    International Nuclear Information System (INIS)

    Clinard, F.W. Jr.; Bunch, J.M.; Ranken, W.A.

    1975-01-01

    Two ceramics under consideration for use in fusion reactors, Al 2 O 3 and Y 2 O 3 , were irradiated in the EBR-II fission reactor at 650, 875, and 1025 0 K to fluences between 2 and 6 x 10 21 n/cm 2 (E greater than 0.1 MeV). Samples evaluated include sapphire, Lucalox, alumina, Y 2 O 3 , and Y 2 O 3 -10 percent ZrO 2 (Yttralox). All Al 2 O 3 specimens swelled significantly (1 to 3 percent), with most of the growth observed in sapphire along the c-axis at the higher temperatures. Al 2 O 3 samples irradiated at 875 to 1025 0 K contained a high density of small aligned ''pores''. Irradiated Y 2 O 3 -based ceramics exhibited dimensional stability and a defect content consisting primarily of unresolved damage and/or dislocation loops. The behavior of these ceramics under irradiation is discussed, and the relevance of fission neutron damage studies to fusion reactor applications is considered. (auth)

  12. Nonvolatile Resistive Switching in Pt/LaAlO_{3}/SrTiO_{3} Heterostructures

    Directory of Open Access Journals (Sweden)

    Shuxiang Wu

    2013-12-01

    Full Text Available Resistive switching heterojunctions, which are promising for nonvolatile memory applications, usually share a capacitorlike metal-oxide-metal configuration. Here, we report on the nonvolatile resistive switching in Pt/LaAlO_{3}/SrTiO_{3} heterostructures, where the conducting layer near the LaAlO_{3}/SrTiO_{3} interface serves as the “unconventional” bottom electrode although both oxides are band insulators. Interestingly, the switching between low-resistance and high-resistance states is accompanied by reversible transitions between tunneling and Ohmic characteristics in the current transport perpendicular to the planes of the heterojunctions. We propose that the observed resistive switching is likely caused by the electric-field-induced drift of charged oxygen vacancies across the LaAlO_{3}/SrTiO_{3} interface and the creation of defect-induced gap states within the ultrathin LaAlO_{3} layer. These metal-oxide-oxide heterojunctions with atomically smooth interfaces and defect-controlled transport provide a platform for the development of nonvolatile oxide nanoelectronics that integrate logic and memory devices.

  13. Porous Na2O-B2O3-Nd2O3 material

    Energy Technology Data Exchange (ETDEWEB)

    De Villiers, D R; Res, M A; Richter, P W

    1986-12-01

    Substitution of SiO2 by Nd2O3 in the sodium borosilicate system produced glasses containing up to 50 mass% Nd2O3. Sodium borate was leached out of some of the materials to produce either a porous Nd2O3-rich glass or a porous glass-ceramic containing NdBO3, depending on the starting material. Surface areas of up to 190 mS g- were measured. Powder X-ray diffraction (XRD) revealed the NdBO3 to be the high-temperature form with low symmetry.

  14. Turbulent mixing layers in supersonic protostellar outflows, with application to DG Tauri

    Science.gov (United States)

    White, M. C.; Bicknell, G. V.; Sutherland, R. S.; Salmeron, R.; McGregor, P. J.

    2016-01-01

    Turbulent entrainment processes may play an important role in the outflows from young stellar objects at all stages of their evolution. In particular, lateral entrainment of ambient material by high-velocity, well-collimated protostellar jets may be the cause of the multiple emission-line velocity components observed in the microjet-scale outflows driven by classical T Tauri stars. Intermediate-velocity outflow components may be emitted by a turbulent, shock-excited mixing layer along the boundaries of the jet. We present a formalism for describing such a mixing layer based on Reynolds decomposition of quantities measuring fundamental properties of the gas. In this model, the molecular wind from large disc radii provides a continual supply of material for entrainment. We calculate the total stress profile in the mixing layer, which allows us to estimate the dissipation of turbulent energy, and hence the luminosity of the layer. We utilize MAPPINGS IV shock models to determine the fraction of total emission that occurs in [Fe II] 1.644 μm line emission in order to facilitate comparison to previous observations of the young stellar object DG Tauri. Our model accurately estimates the luminosity and changes in mass outflow rate of the intermediate-velocity component of the DG Tau approaching outflow. Therefore, we propose that this component represents a turbulent mixing layer surrounding the well-collimated jet in this object. Finally, we compare and contrast our model to previous work in the field.

  15. Bioaccumulation of Fe2O3(magnetic) nanoparticles in Ceriodaphnia dubia

    International Nuclear Information System (INIS)

    Hu Ji; Wang Demin; Wang Jiangtao; Wang Jianmin

    2012-01-01

    While nano-Fe 2 O 3 (magnetic) is generally considered non-toxic, it could serve as a carrier of other toxic chemicals such as As(V) and enhance their toxicity. The bioaccumulation of nano-Fe 2 O 3 (m) with different exposure times, NP concentrations, and pH conditions was investigated using Ceriodaphnia dubia (C. dubia) as the model organism. Under natural pH conditions, C. dubia significantly accumulated nano-Fe 2 O 3 (m) in the gut, with the maximum accumulation being achieved after 6 h of exposure. The concentration of nano-Fe 2 O 3 also impacted its accumulation, with the maximum uptake occurring at 20 mg/L or more. In addition, the highest bioaccumulation occurred in a pH range of 7–8 where the highest feeding rate was reported, confirming that the ingestion of NPs is the main route of nano-Fe 2 O 3 (m) bioaccumulation. In a clean environment without NPs, depuration of nano-Fe 2 O 3 (m) occurred, and food addition accelerated the depuration process. - Highlights: ► Nano-Fe 2 O 3 (m) enhances the toxicity of As(V). ► C. dubia significantly accumulate nano-Fe 2 O 3 (m) through ingestion. ► The bioaccumulation of nano-Fe 2 O 3 (m) is affected by time, NP concentration, and pH. ► Food addition accelerates the depuration process of accumulated nano-Fe 2 O 3 (m). - Nano-Fe 2 O 3 (m) could enhance the toxicity of As(V) due to the significant accumulation of nano-Fe 2 O 3 (m) along with sorbed As(V) by C. dubia through ingestion.

  16. O(3)-invariant tunneling in general relativity

    International Nuclear Information System (INIS)

    Berezin, V.A.; Tkachev, I.I.; Kuzmin, V.A.; AN SSSR, Moscow. Inst. Yadernykh Issledovanij)

    1987-12-01

    We derived a general formula for the action for any O(3)-invariant tunneling processes in false vacuum decay in general relativity. The general classification of the bubble Euclidean trajectories is elaborated and explicit expressions for bounces for some processes like the vacuum creation of a double bubble, in particular in the vicinity of a black hole; the subbarrier creation of the Einstein-Rosen bridge, creation from nothing of two Minkowski worlds connected by a shell etc., are given. (orig.)

  17. The Study of Electrical Properties for Multilayer La2O3/Al2O3 Dielectric Stacks and LaAlO3 Dielectric Film Deposited by ALD.

    Science.gov (United States)

    Feng, Xing-Yao; Liu, Hong-Xia; Wang, Xing; Zhao, Lu; Fei, Chen-Xi; Liu, He-Lei

    2017-12-01

    The capacitance and leakage current properties of multilayer La 2 O 3 /Al 2 O 3 dielectric stacks and LaAlO 3 dielectric film are investigated in this paper. A clear promotion of capacitance properties is observed for multilayer La 2 O 3 /Al 2 O 3 stacks after post-deposition annealing (PDA) at 800 °C compared with PDA at 600 °C, which indicated the recombination of defects and dangling bonds performs better at the high-k/Si substrate interface for a higher annealing temperature. For LaAlO 3 dielectric film, compared with multilayer La 2 O 3 /Al 2 O 3 dielectric stacks, a clear promotion of trapped charges density (N ot ) and a degradation of interface trap density (D it ) can be obtained simultaneously. In addition, a significant improvement about leakage current property is observed for LaAlO 3 dielectric film compared with multilayer La 2 O 3 /Al 2 O 3 stacks at the same annealing condition. We also noticed that a better breakdown behavior for multilayer La 2 O 3 /Al 2 O 3 stack is achieved after annealing at a higher temperature for its less defects.

  18. Schottky contacts to In2O3

    Directory of Open Access Journals (Sweden)

    H. von Wenckstern

    2014-04-01

    Full Text Available n-type binary compound semiconductors such as InN, InAs, or In2O3 are especial because the branch-point energy or charge neutrality level lies within the conduction band. Their tendency to form a surface electron accumulation layer prevents the formation of rectifying Schottky contacts. Utilizing a reactive sputtering process in an oxygen-containing atmosphere, we demonstrate Schottky barrier diodes on indium oxide thin films with rectifying properties being sufficient for space charge layer spectroscopy. Conventional non-reactive sputtering resulted in ohmic contacts. We compare the rectification of Pt, Pd, and Au Schottky contacts on In2O3 and discuss temperature-dependent current-voltage characteristics of Pt/In2O3 in detail. The results substantiate the picture of oxygen vacancies being the source of electrons accumulating at the surface, however, the position of the charge neutrality level and/or the prediction of Schottky barrier heights from it are questioned.

  19. Terahertz Magnon-Polaritons in TmFeO3.

    Science.gov (United States)

    Grishunin, Kirill; Huisman, Thomas; Li, Guanqiao; Mishina, Elena; Rasing, Theo; Kimel, Alexey V; Zhang, Kailing; Jin, Zuanming; Cao, Shixun; Ren, Wei; Ma, Guo-Hong; Mikhaylovskiy, Rostislav V

    2018-04-18

    Magnon-polaritons are shown to play a dominant role in the propagation of terahertz (THz) waves through TmFeO 3 orthoferrite, if the frequencies of the waves are in the vicinity of the quasi-antiferromagnetic spin resonance mode. Both time-domain THz transmission and emission spectroscopies reveal clear beatings between two modes with frequencies slightly above and slightly below this resonance, respectively. Rigorous modeling of the interaction between the spins of TmFeO 3 and the THz light shows that the frequencies correspond to the upper and lower magnon-polariton branches. Our findings reveal the previously ignored importance of propagation effects and polaritons in such heavily debated areas as THz magnonics and THz spectroscopy of electromagnons. It also shows that future progress in these areas calls for an interdisciplinary approach at the interface between magnetism and photonics.

  20. Dynamic Displacement Disorder of Cubic BaTiO3

    Science.gov (United States)

    Paściak, M.; Welberry, T. R.; Kulda, J.; Leoni, S.; Hlinka, J.

    2018-04-01

    The three-dimensional distribution of the x-ray diffuse scattering intensity of BaTiO3 has been recorded in a synchrotron experiment and simultaneously computed using molecular dynamics simulations of a shell model. Together, these have allowed the details of the disorder in paraelectric BaTiO3 to be clarified. The narrow sheets of diffuse scattering, related to the famous anisotropic longitudinal correlations of Ti ions, are shown to be caused by the overdamped anharmonic soft phonon branch. This finding demonstrates that the occurrence of narrow sheets of diffuse scattering agrees with a displacive picture of the cubic phase of this textbook ferroelectric material. The presented methodology allows one to go beyond the harmonic approximation in the analysis of phonons and phonon-related scattering.

  1. Ag+ implantation in Al2O3, LiNbO3 and quartz

    International Nuclear Information System (INIS)

    Rahmani, M.; Townsend, P.D.

    1989-01-01

    Silver implantation in insulators produces colloids whose growth is a function of ion dose, ion energy, implant temperature and crystal orientation. Data for three materials are compared. Colloid growth is favoured by higher energy implants at temperatures where the silver is mobile. Preferential diffusion along the Z axis of Al 2 O 3 , LiNbO 3 and quartz results in a higher fraction of the implanted silver ions appearing in the form of colloids for Y cut crystals than for those of Z cut. Annealing characteristics also show a strong dependence on crystal cut. For the LiNbO 3 the colloids in Z cut crystals anneal most rapidly whereas for Al 2 O 3 those in Y cut material are least stable, their loss being accompanied by a reduction in F centres. (author)

  2. Adsorption heats of olefins on supported MoO3/Al2O3 catalists

    International Nuclear Information System (INIS)

    Grinev, V.E.; Madden, M.; Khalit, V.A.; Aptekar', E.L.; Aldag, A.; Krylov, O.V.

    1983-01-01

    Adsorption heats of C 2 H 4 , C 3 H 6 and C 4 H 8 on supported MoO 3 /Al 2 O 3 catalysts containing 6, 10 and 15 wt. % of MoO 3 at 25, 77 and 195 deg are determimed. Adsorption heat of an olefin increases with a growing length of its carbonic chain. The number of adsorbed olefin molecules grows with an increase in the MoO 3 concentration, while initial adsorption heats decrease. The number of adsorbed olefins is proportional to mean rate of molybdenum reduction in catalysts. Adsorption heats of oxygen on the surface of the catalysts with preliminarily adsorbed olefins are determined. It is shown that adsorption of oxygen and olefins proceeeds both on the same and on different centres of the surface. Mechanisms of surface interactions are discussed

  3. Comparative study of phase structure and dielectric properties for K0.5Bi0.5TiO3-BiAlO3 and LaAlO3-BiAlO3

    International Nuclear Information System (INIS)

    Hou, Yudong; Zheng, Mupeng; Si, Meiju; Cui, Lei; Zhu, Mankang; Yan, Hui

    2013-01-01

    In this work, two perovskite-type compounds, K 0.5 Bi 0.5 TiO 3 and LaAlO 3 , have been selected as host material to incorporate with BiAlO 3 using a solid-state reaction route. The phase evolution and dielectric properties for both systems have been investigated in detail. For the K 0.5 Bi 0.5 TiO 3 -BiAlO 3 system, it is interesting to find that when using Bi 2 O 3 , Al 2 O 3 , K 2 CO 3 , and TiO 2 as starting materials, the formed compounds are K 0.5 Bi 0.5 TiO 3 -K 0.5 Bi 4.5 Ti 4 O 15 and Al 2 O 3 only plays a dopant role. There are two distinct dielectric peaks appearing in the patterns of temperature dependence of dielectric constant, corresponding to the phase-transition points of perovskite-type K 0.5 Bi 0.5 TiO 3 and Aurivillius-type K 0.5 Bi 4.5 Ti 4 O 15 , independently. In comparison, using Bi 2 O 3 , Al 2 O 3 , and La 2 O 3 as starting materials, the pure perovskite phase LaAlO 3 -BiAlO 3 can be obtained. Compared to the inherent paraelectric behavior in LaAlO 3 , the diffuse phase-transition phenomena can be observed in the LaAlO 3 -BiAlO 3 binary system, which corresponds well to the Vogel-Fulcher (VF) relationship. Moreover, compared to pure LaAlO 3 , the synthesized LaAlO 3 -BiAlO 3 compound shows enhanced dielectric properties, which are promising in application as gate dielectric materials. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Differential Canalograms Detect Outflow Changes from Trabecular Micro-Bypass Stents and Ab Interno Trabeculectomy.

    Science.gov (United States)

    Parikh, Hardik A; Loewen, Ralitsa T; Roy, Pritha; Schuman, Joel S; Lathrop, Kira L; Loewen, Nils A

    2016-11-04

    Recently introduced microincisional glaucoma surgeries that enhance conventional outflow offer a favorable risk profile over traditional surgeries, but can be unpredictable. Two paramount challenges are the lack of an adequate training model for angle surgeries and the absence of an intraoperative quantification of surgical success. To address both, we developed an ex vivo training system and a differential, quantitative canalography method that uses slope-adjusted fluorescence intensities of two different chromophores to avoid quenching. We assessed outflow enhancement by trabecular micro-bypass (TMB) implantation or by ab interno trabeculectomy (AIT). In this porcine model, TMB resulted in an insignificant (p > 0.05) outflow increase of 13 ± 5%, 14 ± 8%, 9 ± 3%, and 24 ± 9% in the inferonasal, superonasal, superotemporal, and inferotemporal quadrant, respectively. AIT caused a 100 ± 50% (p = 0.002), 75 ± 28% (p = 0.002), 19 ± 8%, and 40 ± 21% increase in those quadrants. The direct gonioscopy and tactile feedback provided a surgical experience that was very similar to that in human patients. Despite the more narrow and discontinuous circumferential drainage elements in the pig with potential for underperformance or partial stent obstruction, unequivocal patterns of focal outflow enhancement by TMB were seen in this training model. AIT achieved extensive access to outflow pathways beyond the surgical site itself.

  5. Apparent vanishing of ferroelectricity in nanostructured BiScO3PbTiO3

    OpenAIRE

    Amorín , H; Jiménez , R; Ricote , J; Hungría , T; Castro , A; Algueró , M

    2010-01-01

    Abstract Nanostructured ceramics of high-temperature piezoelectric 0.375BiScO 3 -0.625PbTiO 3 were prepared by spark plasma sintering of nanocrystalline powders obtained by mechanosynthesis. The macroscopic electrical properties were characterized on dense ceramics with decreasing average grain size down to 28 nm. Results indicate that the electric field is screened by the electrically insulating grain boundaries at the nanoscale, which needs to be considered when discussing size effects i...

  6. Dielectric enhancement of BaTiO3/SrTiO3 superlattices with embedded Ni nanocrystals

    International Nuclear Information System (INIS)

    Xiong Zhengwei; Sun Weiguo; Wang Xuemin; Jiang Fan; Wu Weidong

    2012-01-01

    Highlights: ► The BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs were successfully fabricated by L-MBE. ► The influence with the various concentrations of Ni nanocrystals embedded in BaTiO 3 /SrTiO 3 superlattices was also discussed. ► The BaTiO 3 /SrTiO 3 superlattices with lower concentration of embedded Ni NCs had higher permittivity and dielectric loss compared with the pure BaTiO 3 /SrTiO 3 superlattices. ► The dielectric enhancement of BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs was proposed to explained by Drude quasi-free-electron theory. - Abstract: The self-organized Ni nanocrystals (NCs) were embedded in BaTiO 3 /SrTiO 3 superlattices using laser molecular beam epitaxy (L-MBE). The stress of the composite films was increased with the increasing concentration of embedded Ni NCs, as investigation in stress calculation. The influence with the various concentrations of Ni NCs embedded in BaTiO 3 /SrTiO 3 superlattices was also discussed. The internal stress of the films was too strong to epitaxial growth of BaTiO 3 /SrTiO 3 superlattices. Compared with the pure BaTiO 3 /SrTiO 3 superlattices, the BaTiO 3 /SrTiO 3 superlattices with lower concentration of embedded Ni NCs had higher permittivity and dielectric loss. Furthermore, the dielectric enhancement of BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs was proposed to explained by Drude quasi-free-electron theory.

  7. Human cerebral venous outflow pathway depends on posture and central venous pressure

    DEFF Research Database (Denmark)

    Gisolf, J; van Lieshout, J J; van Heusden, K

    2004-01-01

    and central venous pressure (CVP) on the distribution of cerebral outflow over the internal jugular veins and the vertebral plexus, using a mathematical model. Input to the model was a data set of beat-to-beat cerebral blood flow velocity and CVP measurements in 10 healthy subjects, during baseline rest......Internal jugular veins are the major cerebral venous outflow pathway in supine humans. In upright humans the positioning of these veins above heart level causes them to collapse. An alternative cerebral outflow pathway is the vertebral venous plexus. We set out to determine the effect of posture...... and a Valsalva manoeuvre in the supine and standing position. The model, consisting of 2 jugular veins, each a chain of 10 units containing nonlinear resistances and capacitors, and a vertebral plexus containing a resistance, showed blood flow mainly through the internal jugular veins in the supine position...

  8. Silo outflow of soft frictionless spheres

    Science.gov (United States)

    Ashour, Ahmed; Trittel, Torsten; Börzsönyi, Tamás; Stannarius, Ralf

    2017-12-01

    Outflow of granular materials from silos is a remarkably complex physical phenomenon that has been extensively studied with simple objects like monodisperse hard disks in two dimensions (2D) and hard spheres in 2D and 3D. For those materials, empirical equations were found that describe the discharge characteristics. Softness adds qualitatively new features to the dynamics and to the character of the flow. We report a study of the outflow of soft, practically frictionless hydrogel spheres from a quasi-2D bin. Prominent features are intermittent clogs, peculiar flow fields in the container, and a pronounced dependence of the flow rate and clogging statistics on the container fill height. The latter is a consequence of the ineffectiveness of Janssen's law: the pressure at the bottom of a bin containing hydrogel spheres grows linearly with the fill height.

  9. Hot Accretion onto Black Holes with Outflow

    Directory of Open Access Journals (Sweden)

    Park Myeong-Gu

    2018-01-01

    Full Text Available Classic Bondi accretion flow can be generalized to rotating viscous accretion flow. Study of hot accretion flow onto black holes show that its physical charateristics change from Bondi-like for small gas angular momentum to disk-like for Keperian gas angular momentum. Especially, the mass accretion rate divided by the Bondi accretion rate is proportional to the viscosity parameter alpha and inversely proportional to the gas angular momentum divided by the Keplerian angular momentum at the Bondi radius for gas angular momentum comparable to the Keplerian value. The possible presence of outflow will increase the mass inflow rate at the Bondi radius but decrease the mass accretion rate across the black hole horizon by many orders of magnitude. This implies that the growth history of supermassive black holes and their coevolution with host galaxies will be dramatically changed when the accreted gas has angular momentum or develops an outflow.

  10. Magnetostriction of Hexagonal HoMnO3 and YMnO3 Single Crystals

    Science.gov (United States)

    Pavlovskii, N. S.; Dubrovskii, A. A.; Nikitin, S. E.; Semenov, S. V.; Terent'ev, K. Yu.; Shaikhutdinov, K. A.

    2018-03-01

    We report on the magnetostriction of hexagonal HoMnO3 and YMnO3 single crystals in a wide range of applied magnetic fields (up to H = 14 T) at all possible combinations of the mutual orientations of magnetic field H and magnetostriction Δ L/L. The measured Δ L/L( H, T) data agree well with the magnetic phase diagram of the HoMnO3 single crystal reported previously by other authors. It is shown that the nonmonotonic behavior of magnetostriction of the HoMnO3 crystal is caused by the Ho3+ ion; the magnetic moment of the Mn3+ ion parallel to the hexagonal crystal axis. The anomalies established from the magnetostriction measurements of HoMnO3 are consistent with the phase diagram of these compounds. For the isostructural YMnO3 single crystal with a nonmagnetic rare-earth ion, the Δ L/L( H, T) dependences are described well by a conventional quadratic law in a wide temperature range (4-100 K). In addition, the magnetostriction effect is qualitatively estimated with regard to the effect of the crystal electric field on the holmium ion.

  11. Electromechanical behavior of [001]-textured Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics

    Science.gov (United States)

    Yan, Yongke; Wang, Yu. U.; Priya, Shashank

    2012-05-01

    [001]-textured Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) ceramics were synthesized by using templated grain growth method. Significantly high [001] texture degree corresponding to 0.98 Lotgering factor was achieved at 1 vol. % BaTiO3 template. Electromechanical properties for [001]-textured PMN-PT ceramics with 1 vol. % BaTiO3 were found to be d33 = 1000 pC/N, d31 = 371 pC/N, ɛr = 2591, and tanδ = ˜0.6%. Elastoelectric composite based modeling results showed that higher volume fraction of template reduces the overall dielectric constant and thus has adverse effect on the piezoelectric response. Clamping effect was modeled by deriving the changes in free energy as a function of applied electric field and microstructural boundary condition.

  12. Electrical conductivity of In2O3 and Ga2O3 after low temperature ion irradiation; implications for instrinsic defect formation and charge neutrality level.

    Science.gov (United States)

    Vines, L; Bhoodoo, C; von Wenckstern, H; Grundmann, M

    2017-12-13

    The evolution of sheet resistance of n-type In 2 O 3 and Ga 2 O 3 exposed to bombardment with MeV 12 C and 28 Si ions at 35 K is studied in situ. While the sheet resistance of Ga 2 O 3 increased by more than eight orders of magnitude as a result of ion irradiation, In 2 O 3 showed a more complex defect evolution and became more conductive when irradiated at the highest doses. Heating up to room temperature reduced the sheet resistivity somewhat, but Ga 2 O 3 remained highly resistive, while In 2 O 3 showed a lower resistance than as deposited samples. Thermal admittance spectroscopy and deep level transient spectroscopy did not reveal new defect levels for irradiation up to [Formula: see text] cm -2 . A model where larger defect complexes preferentially produce donor like defects in In 2 O 3 is proposed, and may reveal a microscopic view of a charge neutrality level within the conduction band, as previously proposed.

  13. Electrical conductivity of In2O3 and Ga2O3 after low temperature ion irradiation; implications for instrinsic defect formation and charge neutrality level

    Science.gov (United States)

    Vines, L.; Bhoodoo, C.; von Wenckstern, H.; Grundmann, M.

    2018-01-01

    The evolution of sheet resistance of n-type In2O3 and Ga2O3 exposed to bombardment with MeV 12C and 28Si ions at 35 K is studied in situ. While the sheet resistance of Ga2O3 increased by more than eight orders of magnitude as a result of ion irradiation, In2O3 showed a more complex defect evolution and became more conductive when irradiated at the highest doses. Heating up to room temperature reduced the sheet resistivity somewhat, but Ga2O3 remained highly resistive, while In2O3 showed a lower resistance than as deposited samples. Thermal admittance spectroscopy and deep level transient spectroscopy did not reveal new defect levels for irradiation up to 2 × 1012 cm-2. A model where larger defect complexes preferentially produce donor like defects in In2O3 is proposed, and may reveal a microscopic view of a charge neutrality level within the conduction band, as previously proposed.

  14. ITO-free flexible organic photovoltaics with multilayer MoO3/LiF/MoO3/Ag/MoO3 as the transparent electrode

    International Nuclear Information System (INIS)

    Chen, Shilin; Dai, Yunjie; Zhang, Hongmei; Zhao, Dewei

    2016-01-01

    We present efficient flexible organic photovoltaics (OPVs) with multiple layers of molybdenum oxide (MoO 3 )/LiF/MoO 3 /Ag/MoO 3 as the transparent electrode, where the thin Ag layer yields high conductivity and the dielectric layer MoO 3 /LiF/MoO 3 has high transparency due to optical interference, leading to improved power conversion efficiency compared with indium tin oxide (ITO) based devices. The MoO 3 contacting organic active layer is used as a buffer layer for good hole extraction. Thus, the multilayer MoO 3 /LiF/MoO 3 /Ag/MoO 3 can improve light transmittance and also facilitate charge carrier extraction. Such an electrode shows excellent mechanical bendability with a 9% reduction of efficiency after 1000 cycles of bending due to the ductile nature of the thin metal layer and dielectric layer used. Our results suggest that the MoO 3 /LiF/MoO 3 /Ag/MoO 3 multilayer electrode is a promising alternative to ITO as an electrode in OPVs. (paper)

  15. Conductivity of A- and B-site doped LaAlO3, LaGaO3, LaScO3 and LaInO3 perovskites

    DEFF Research Database (Denmark)

    Lybye, D.; Poulsen, F.W.; Mogensen, Mogens Bjerg

    2000-01-01

    The conductivity of the materials LaAlO3, LaGaO3, LaScO3 and LaInO3 all doped with 10% strontium on the A-site and 10% magnesium at the B-site has been measured at different temperatures and oxygen partial pressures. The doped LaGaO3 is found to be an almost pure ionic conductor with a conductivi...

  16. Photoinduced modulation and relaxation characteristics in LaAlO3/SrTiO3 heterointerface

    KAUST Repository

    Jin, K. X.

    2015-03-05

    We report the modulation and relaxation characteristics in the two-dimensional electron gas system at LaAlO3/SrTiO3 heterointerface induced by the ultraviolet light illumination (365 nm). The suppression of Kondo effect at the interface illuminated by the light originates from the light irradiation-induced decoherence effect of localized states. It is interesting to note that the persistent and transient photoinduced effects are simultaneously observed and the photoinduced maximum change values in resistance are 80.8% and 51.4% at T = 20 K, respectively. Moreover, the photoinduced relaxation processes after the irradiation are systematically analyzed using the double exponential model. These results provide the deeper understanding of the photoinduced effect and the experimental evidence of tunable Kondo effect in oxides-based two-dimensional electron gas systems.

  17. Regulation of depletion layer width in Pb(Zr,Ti)O3/Nb:SrTiO3 heterostructures

    Science.gov (United States)

    Bai, Yu; Jie Wang, Zhan; Cui, Jian Zhong; Zhang, Zhi Dong

    2018-05-01

    Improving the tunability of depletion layer width (DLW) in ferroelectric/semiconductor heterostructures is important for the performance of some devices. In this work, 200-nm-thick Pb(Zr0.4Ti0.6)O3 (PZT) films were deposited on different Nb-doped SrTiO3 (NSTO) substrates, and the tunability of DLW at PZT/NSTO interfaces were studied. Our results showed that the maximum tunability of the DLW was achieved at the NSTO substrate with 0.5 wt% Nb. On the basis of the modified capacitance model and the ferroelectric semiconductor theory, we suggest that the tunability of the DLW in PZT/NSTO heterostructures can be attributed to a delicate balance of the depletion layer charge and the ferroelectric polarization charge. Therefore, the performance of some devices related to the tunability of DLW in ferroelectric/semiconductor heterostructures can be improved by modulating the doping concentration in semiconducting electrode materials.

  18. Photoinduced modulation and relaxation characteristics in LaAlO3/SrTiO3 heterointerface

    KAUST Repository

    Jin, K. X.; Lin, W.; Luo, B. C.; Wu, Tao

    2015-01-01

    We report the modulation and relaxation characteristics in the two-dimensional electron gas system at LaAlO3/SrTiO3 heterointerface induced by the ultraviolet light illumination (365 nm). The suppression of Kondo effect at the interface illuminated by the light originates from the light irradiation-induced decoherence effect of localized states. It is interesting to note that the persistent and transient photoinduced effects are simultaneously observed and the photoinduced maximum change values in resistance are 80.8% and 51.4% at T = 20 K, respectively. Moreover, the photoinduced relaxation processes after the irradiation are systematically analyzed using the double exponential model. These results provide the deeper understanding of the photoinduced effect and the experimental evidence of tunable Kondo effect in oxides-based two-dimensional electron gas systems.

  19. Containerless solidification of BiFeO3 oxide under microgravity

    Science.gov (United States)

    Yu, Jianding; Arai, Yasutomo; Koshikawa, Naokiyo; Ishikawa, Takehito; Yoda, Shinichi

    1999-07-01

    Containerless solidification of BiFeO3 oxide has been carried out under microgravity with Electrostatic Levitation Furnace (ELF) aboard on the sounding rocket (TR-IA). It is a first containerless experiment using ELF under microgravity for studying the solidification of oxide insulator material. Spherical BiFeO3 sample with diameter of 5mm was heated by two lasers in oxygen and nitrogen mixing atmosphere, and the sample position by electrostatic force under pinpoint model and free drift model. In order to compare the solidification behavior in microgravity with on ground, solidification experiments of BiFeO3 in crucible and drop tube were carried out. In crucible experiment, it was very difficult to get single BiFeO3 phase, because segregation of Fe2O3 occured very fast and easily. In drop tube experiment, fine homogeneous BiFeO3 microstructure was obtained in a droplet about 300 μm. It implies that containerless processing can promote the phase selection in solidification. In microgravity experiment, because the heating temperature was lower than that of estimated, the sample was heated into Fe2O3+liquid phase region. Fe2O3 single crystal grew on the surface of the spherical sample, whose sample was clearly different from that observed in ground experiments.

  20. Ionized Gas Outflows from the MAGNUM Survey: NGC 1365 and NGC 4945

    Energy Technology Data Exchange (ETDEWEB)

    Venturi, Giacomo; Marconi, Alessandro [Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze, Sesto Fiorentino (Italy); Osservatorio Astrofisico di Arcetri (INAF), Firenze (Italy); Mingozzi, Matilde [Osservatorio Astrofisico di Arcetri (INAF), Firenze (Italy); Dipartimento di Fisica e Astronomia, Università di Bologna, Bologna (Italy); Carniani, Stefano [Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge (United Kingdom); Kavli Institute for Cosmology, University of Cambridge, Cambridge (United Kingdom); Cresci, Giovanni [Osservatorio Astrofisico di Arcetri (INAF), Firenze (Italy); Risaliti, Guido [Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze, Sesto Fiorentino (Italy); Osservatorio Astrofisico di Arcetri (INAF), Firenze (Italy); Mannucci, Filippo, E-mail: gventuri@arcetri.astro.it [Osservatorio Astrofisico di Arcetri (INAF), Firenze (Italy)

    2017-11-24

    AGN feedback, acting through strong outflows accelerated in the nuclear region of AGN hosts, is invoked as a key ingredient for galaxy evolution by many models to explain the observed BH-galaxy scaling relations. Recently, some direct observational evidence of radiative mode feedback in action has been finally found in quasars at z >1.5. However, it is not possible to study outflows in quasars at those redshifts on small scales (≲100 pc), as spatial information is limited by angular resolution. This is instead feasible in nearby active galaxies, which are ideal laboratories to explore outflow structure and properties, as well as the effects of AGN on their host galaxies. In this proceeding we present preliminary results from the MAGNUM survey, which comprises nearby Seyfert galaxies observed with the integral field spectrograph VLT/MUSE. We focus on two sources, NGC 1365 and NGC 4945, that exhibit double conical outflows extending on distances >1 kpc. We disentangle the dominant contributions to ionization of the various gas components observed in the central ~5.3 kpc of NGC 1365. An attempt to infer outflow 3D structure in NGC 4945 is made via simple kinematic modeling, suggesting a hollow cone geometry.

  1. Ionized Gas Outflows from the MAGNUM Survey: NGC 1365 and NGC 4945

    Directory of Open Access Journals (Sweden)

    Giacomo Venturi

    2017-11-01

    Full Text Available AGN feedback, acting through strong outflows accelerated in the nuclear region of AGN hosts, is invoked as a key ingredient for galaxy evolution by many models to explain the observed BH-galaxy scaling relations. Recently, some direct observational evidence of radiative mode feedback in action has been finally found in quasars at z >1.5. However, it is not possible to study outflows in quasars at those redshifts on small scales (≲100 pc, as spatial information is limited by angular resolution. This is instead feasible in nearby active galaxies, which are ideal laboratories to explore outflow structure and properties, as well as the effects of AGN on their host galaxies. In this proceeding we present preliminary results from the MAGNUM survey, which comprises nearby Seyfert galaxies observed with the integral field spectrograph VLT/MUSE. We focus on two sources, NGC 1365 and NGC 4945, that exhibit double conical outflows extending on distances >1 kpc. We disentangle the dominant contributions to ionization of the various gas components observed in the central ~5.3 kpc of NGC 1365. An attempt to infer outflow 3D structure in NGC 4945 is made via simple kinematic modeling, suggesting a hollow cone geometry.

  2. ERUPTIVE VARIABLE STARS AND OUTFLOWS IN SERPENS NW

    Energy Technology Data Exchange (ETDEWEB)

    Hodapp, Klaus W. [Institute for Astronomy, University of Hawaii, 640 N. Aohoku Place, Hilo, HI 96720 (United States); Chini, Rolf; Watermann, Ramon; Lemke, Roland, E-mail: hodapp@ifa.hawaii.edu [Ruhr Universitaet Bochum, Astronomisches Institut, Universitaetsstrasse 150, D-44801 Bochum (Germany)

    2012-01-01

    We study the outflow activity, photometric variability, and morphology of three very young stellar objects in the Serpens NW star-forming region: OO Serpentis, EC 37 (V370 Ser), and EC 53 (V371 Ser). High spatial resolution Keck/NIRC2 laser guide star adaptive optics images obtained in 2007 and 2009 in broadband K and in a narrowband filter centered on the 1-0 S(1) emission line of H{sub 2} allow us to identify the outflows from all three objects. We also present new, seeing-limited data on the photometric evolution of the OO Ser reflection nebula and re-analyze previously published data. We find that OO Ser declined in brightness from its outburst peak in 1995 to about 2003, but that this decline has recently stopped and actually reversed itself in some areas of the reflection nebula. The morphology and proper motions of the shock fronts MHO 2218 near EC 37 suggest that they all originate in EC 37 and that this is an outflow seen nearly along its axis. We identify an H{sub 2} jet emerging from the cometary nebula EC 53. The star illuminating EC 53 is periodically variable with a period of 543 days and has a close-by, non-variable companion at a projected distance of 92 AU. We argue that the periodic variability is the result of accretion instabilities triggered by another very close, not directly observable, binary companion and that EC 53 can be understood in the model of a multiple system developing into a hierarchical configuration.

  3. DENSE CLUMPS AND CANDIDATES FOR MOLECULAR OUTFLOWS IN W40

    Energy Technology Data Exchange (ETDEWEB)

    Shimoikura, Tomomi; Dobashi, Kazuhito [Department of Astronomy and Earth Sciences, Tokyo Gakugei University, Koganei, Tokyo 184-8501 (Japan); Nakamura, Fumitaka; Hara, Chihomi; Kawabe, Ryohei [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Tanaka, Tomohiro [Department of Physical Science, Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan); Shimajiri, Yoshito [Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot, IRFU/Service d’Astrophysique, CEA Saclay, F-91191 Gif-sur-Yvette (France); Sugitani, Kouji, E-mail: ikura@u-gakugei.ac.jp [Graduate School of Natural Sciences, Nagoya City University, Mizuho-ku, Nagoya 467-8501 (Japan)

    2015-06-20

    We report the results of the {sup 12}CO (J = 3−2) and HCO{sup +} (J = 4−3) observations of the W40 H ii region with the Atacama Submillimeter Telescope Experiment (ASTE) 10 m telescope (HPBW ≃ 22″) to search for molecular outflows and dense clumps. We found that the velocity field in the region is highly complex, consisting of at least four distinct velocity components at V{sub LSR} ≃ 3, 5, 7, and 10 km s{sup −1}. The ∼7 km s{sup −1} component represents the systemic velocity of cold gas surrounding the entire region, and causes heavy absorption in the {sup 12}CO spectra over the velocity range 6 ≲ V{sub LSR} ≲ 9 km s{sup −1}. The ∼5 and ∼10 km s{sup −1} components exhibit high {sup 12}CO temperature (≳40 K) and are found mostly around the H ii region, suggesting that these components are likely to be tracing dense gas interacting with the expanding shell around the H ii region. Based on the {sup 12}CO data, we identified 13 regions of high velocity gas, which we interpret as candidate outflow lobes. Using the HCO{sup +} data, we also identified six clumps and estimated their physical parameters. On the basis of the ASTE data and near-infrared images from 2MASS, we present an updated three-dimensional model of this region. In order to investigate molecular outflows in W40, the SiO (J = 1−0, v = 0) emission line and some other emission lines at 40 GHz were also observed with the 45 m telescope at the Nobeyama Radio Observatory, but they were not detected at the present sensitivity.

  4. Outflow Kinematics Manifested by the Hα Line: Gas Outflows in Type 2 AGNs. IV

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Daeun; Woo, Jong-Hak; Bae, Hyun-Jin, E-mail: woo@astro.snu.ac.kr [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of)

    2017-08-20

    Energetic ionized gas outflows driven by active galactic nuclei (AGNs) have been studied as a key phenomenon related to AGN feedback. To probe the kinematics of the gas in the narrow-line region, [O iii] λ 5007 has been utilized in a number of studies showing nonvirial kinematic properties due to AGN outflows. In this paper, we statistically investigate whether the H α emission line is influenced by AGN-driven outflows by measuring the kinematic properties based on the H α line profile and comparing them with those of [O iii]. Using the spatially integrated spectra of ∼37,000 Type 2 AGNs at z < 0.3 selected from the Sloan Digital Sky Survey DR7, we find a nonlinear correlation between H α velocity dispersion and stellar velocity dispersion that reveals the presence of the nongravitational component, especially for AGNs with a wing component in H α . The large H α velocity dispersion and velocity shift of luminous AGNs are clear evidence of AGN outflow impacts on hydrogen gas, while relatively smaller kinematic properties compared to those of [O iii] imply that the observed outflow effect on the H α line is weaker than the case of [O iii].

  5. Appearance and disappearance of ferromagnetism in ultrathin LaMnO3 on SrTiO3 substrate: A viewpoint from first principles

    Science.gov (United States)

    An, Ming; Weng, Yakui; Zhang, Huimin; Zhang, Jun-Jie; Zhang, Yang; Dong, Shuai

    2017-12-01

    The intrinsic magnetic state (ferromagnetic or antiferromagnetic) of ultrathin LaMnO3 films on the most commonly used SrTiO3 substrate is a long-existing question under debate. Either strain effect or nonstoichiometry was argued to be responsible for the experimental ferromagnetism. In a recent experiment [X. R. Wang, C. J. Li, W. M. Lü, T. R. Paudel, D. P. Leusink, M. Hoek, N. Poccia, A. Vailionis, T. Venkatesan, J. M. D. Coey, E. Y. Tsymbal, Ariando, and H. Hilgenkamp, Science 349, 716 (2015), 10.1126/science.aaa5198], one more mechanism, namely, the self-doping due to polar discontinuity, was argued to be the driving force of ferromagnetism beyond the critical thickness. Here systematic first-principles calculations have been performed to check these mechanisms in ultrathin LaMnO3 films as well as superlattices. Starting from the very precise descriptions of both LaMnO3 and SrTiO3, it is found that the compressive strain is the dominant force for the appearance of ferromagnetism, while the open surface with oxygen vacancies leads to the suppression of ferromagnetism. Within LaMnO3 layers, the charge reconstructions involve many competitive factors and certainly go beyond the intuitive polar catastrophe model established for LaAlO3/SrTiO3 heterostructures. Our paper not only explains the long-term puzzle regarding the magnetism of ultrathin LaMnO3 films but also sheds light on how to overcome the notorious magnetic dead layer in ultrathin manganites.

  6. Ketoprofen removal by O3 and O3/UV processes: Kinetics, transformation products and ecotoxicity

    International Nuclear Information System (INIS)

    Illés, Erzsébet; Szabó, Emese; Takács, Erzsébet; Wojnárovits, László; Dombi, András; Gajda-Schrantz, Krisztina

    2014-01-01

    Ozonation (O 3 ) and its combination with ultraviolet radiation (O 3 /UV) were used to decompose ketoprofen (KET). Depending on the initial KET concentration, fourteen to fifty time's faster KET degradation was achieved using combined O 3 /UV method compared to simple ozonation. Using both methods, formation of four major aromatic transformation products were observed: 3-(1-hydroxyethyl)benzophenone, 3-(1-hydroperoxyethyl) benzophenone, 1-(3-benzoylphenyl) ethanone and 3-ethylbenzophenone. In the combined treatment the degradation was mainly due to the direct effect of UV light, however, towards the end of the treatment, O 3 highly contributed to the mineralization of small carboxylic acids. High (∼ 90%) mineralization degree was achieved using the O 3 /UV method. Toxicity tests performed using representatives of three trophic levels of the aquatic ecosystems (producers, consumers and decomposers) Pseudokirchneriella subcapitata green algae, Daphnia magna zooplanktons and Vibrio fischeri bacteria showed that under the used experimental conditions the transformation products have significantly higher toxicity towards all the test organisms, than KET itself. The bacteria and the zooplanktons showed higher tolerance to the formed products than algae. The measured toxicity correlates well with the concentration of the aromatic transformation products, therefore longer treatments than needed for complete degradation of KET are strongly suggested, in order to avoid possible impact of aromatic transformation products on the aquatic ecosystem. - Highlights: • Ketoprofen degradation is significantly faster using O 3 /UV compared to ozonation. • The presence of O 3 enhances the overall mineralization. • Formation of four major aromatic by-products was observed. • The main step in the decomposition is the decarboxylation. • Degradation products have higher toxicity than ketoprofen itself

  7. Cloud Formation and Water Transport on Mars after Major Outflow Events

    Science.gov (United States)

    Santiago, D. L.; Colaprete, A.; Kreslavsky, M.; Kahre, M. A.; Asphaug, E.

    2012-01-01

    The triggering of a robust water cycle on Mars might have been caused by the gigantic flooding events evidenced by outflow channels. We use the Ames Mars General Circulation Model (MGCM) to test this hypothesis, studying how these presumably abrupt eruptions of water might have affected the climate of Mars in the past. We model where the water ultimately went as part of a transient atmospheric water cycle, to answer questions including: (1) Can sudden introductions of large amounts of water on the Martian surface lead to a new equilibrated water cycle? (2) What are the roles of water vapor and water ice clouds to sudden changes in the water cycle on Mars? (3) How are radiative feedbacks involved with this? (4) What is the ultimate fate of the outflow water? (5) Can we tie certain geological features to outflow water redistributed by the atmosphere?

  8. Atmospheric pollutant outflow from southern Asia: a review

    Directory of Open Access Journals (Sweden)

    M. G. Lawrence

    2010-11-01

    Full Text Available Southern Asia, extending from Pakistan and Afghanistan to Indonesia and Papua New Guinea, is one of the most heavily populated regions of the world. Biofuel and biomass burning play a disproportionately large role in the emissions of most key pollutant gases and aerosols there, in contrast to much of the rest of the Northern Hemisphere, where fossil fuel burning and industrial processes tend to dominate. This results in polluted air masses which are enriched in carbon-containing aerosols, carbon monoxide, and hydrocarbons. The outflow and long-distance transport of these polluted air masses is characterized by three distinct seasonal circulation patterns: the winter monsoon, the summer monsoon, and the monsoon transition periods. During winter, the near-surface flow is mostly northeasterly, and the regional pollution forms a thick haze layer in the lower troposphere which spreads out over millions of square km between southern Asia and the Intertropical Convergence Zone (ITCZ, located several degrees south of the equator over the Indian Ocean during this period. During summer, the heavy monsoon rains effectively remove soluble gases and aerosols. Less soluble species, on the other hand, are lifted to the upper troposphere in deep convective clouds, and are then transported away from the region by strong upper tropospheric winds, particularly towards northern Africa and the Mediterranean in the tropical easterly jet. Part of the pollution can reach the tropical tropopause layer, the gateway to the stratosphere. During the monsoon transition periods, the flow across the Indian Ocean is primarily zonal, and strong pollution plumes originating from both southeastern Asia and from Africa spread across the central Indian Ocean. This paper provides a review of the current state of knowledge based on the many observational and modeling studies over the last decades that have examined the southern Asian atmospheric pollutant outflow and its large scale

  9. Atmospheric pollutant outflow from southern Asia: a review

    Science.gov (United States)

    Lawrence, M. G.; Lelieveld, J.

    2010-11-01

    Southern Asia, extending from Pakistan and Afghanistan to Indonesia and Papua New Guinea, is one of the most heavily populated regions of the world. Biofuel and biomass burning play a disproportionately large role in the emissions of most key pollutant gases and aerosols there, in contrast to much of the rest of the Northern Hemisphere, where fossil fuel burning and industrial processes tend to dominate. This results in polluted air masses which are enriched in carbon-containing aerosols, carbon monoxide, and hydrocarbons. The outflow and long-distance transport of these polluted air masses is characterized by three distinct seasonal circulation patterns: the winter monsoon, the summer monsoon, and the monsoon transition periods. During winter, the near-surface flow is mostly northeasterly, and the regional pollution forms a thick haze layer in the lower troposphere which spreads out over millions of square km between southern Asia and the Intertropical Convergence Zone (ITCZ), located several degrees south of the equator over the Indian Ocean during this period. During summer, the heavy monsoon rains effectively remove soluble gases and aerosols. Less soluble species, on the other hand, are lifted to the upper troposphere in deep convective clouds, and are then transported away from the region by strong upper tropospheric winds, particularly towards northern Africa and the Mediterranean in the tropical easterly jet. Part of the pollution can reach the tropical tropopause layer, the gateway to the stratosphere. During the monsoon transition periods, the flow across the Indian Ocean is primarily zonal, and strong pollution plumes originating from both southeastern Asia and from Africa spread across the central Indian Ocean. This paper provides a review of the current state of knowledge based on the many observational and modeling studies over the last decades that have examined the southern Asian atmospheric pollutant outflow and its large scale effects. An outlook

  10. Crystalline and electronic structure of epitaxial γ-Al2O3 films

    International Nuclear Information System (INIS)

    Wu, Huiyan; Lu, Dawei; Zhu, Kerong; Xu, Guoyong; Wang, Hu

    2013-01-01

    Epitaxial γ-Al 2 O 3 films were fabricated on SrTiO 3 (1 0 0) substrates using pulsed laser deposition (PLD) technique. The high quality of epitaxial growth γ-Al 2 O 3 films was confirmed by X-ray diffraction (XRD). Atomic force microscopy (AFM) images indicated the smooth surfaces and the step-flow growth of the films. In order to illuminate the electronic properties and the local structure of the epitaxial γ-Al 2 O 3 , we experimentally measured the X-ray absorption near-edge structure (XANES) spectrum at the O K-edge and compared the spectrum with the theoretical simulations by using various structure models. Our results based on XANES spectrum analysis indicated that the structure of the epitaxial γ-Al 2 O 3 film was a defective spinel with Al vacancies, which prefer to be located at the octahedral sites

  11. Tin-Assisted Synthesis of ɛ -Ga2O3 by Molecular Beam Epitaxy

    Science.gov (United States)

    Kracht, M.; Karg, A.; Schörmann, J.; Weinhold, M.; Zink, D.; Michel, F.; Rohnke, M.; Schowalter, M.; Gerken, B.; Rosenauer, A.; Klar, P. J.; Janek, J.; Eickhoff, M.

    2017-11-01

    The synthesis of ɛ -Ga2O3 and β -Ga2O3 by plasma-assisted molecular beam epitaxy on (001 )Al2O3 substrates is studied. The growth window of β -Ga2O3 in the Ga-rich regime, usually limited by the formation of volatile gallium suboxide, is expanded due to the presence of tin during the growth process, which stabilizes the formation of gallium oxides. X-ray diffraction, transmission electron microscopy, time-of-flight secondary-ion mass spectrometry, Raman spectroscopy, and atomic force microscopy are used to analyze the influence of tin on the layer formation. We demonstrate that it allows the synthesis of phase-pure ɛ -Ga2O3 . A growth model based on the oxidation of gallium suboxide by reduction of an intermediate sacrificial tin oxide is suggested.

  12. Photochemistry of the α-Al2O3-PETN Interface

    Directory of Open Access Journals (Sweden)

    Roman V. Tsyshevsky

    2016-02-01

    Full Text Available Optical absorption measurements are combined with electronic structure calculations to explore photochemistry of an α-Al2O3-PETN interface formed by a nitroester (pentaerythritol tetranitrate, PETN, C5H8N4O12 and a wide band gap aluminum oxide (α-Al2O3 substrate. The first principles modeling is used to deconstruct and interpret the α-Al2O3-PETN absorption spectrum that has distinct peaks attributed to surface F0-centers and surface—PETN transitions. We predict the low energy α-Al2O3 F0-center—PETN transition, producing the excited triplet state, and α-Al2O3 F0-center—PETN charge transfer, generating the PETN anion radical. This implies that irradiation by commonly used lasers can easily initiate photodecomposition of both excited and charged PETN at the interface. The feasible mechanism of the photodecomposition is proposed.

  13. Fundamental absorption of Y2O3 and YAlO3

    International Nuclear Information System (INIS)

    Abramov, V.N.; Kuznetsov, A.I.

    1978-01-01

    Reflection spectra in the range of 4-14 eV were measured for Y 2 O 3 and YAlO 3 crystals. The spectra of the following optical characteristics were calculated with the aid of the Kramers-Kroning relation: absorption, refraction, dielectric constant, and effective number of electrons. Excitons with an energy of 6.0 eV and an oscillator strength of f approximately 0.1 were found in Y 2 O 3 , and the width of the forbidden zone was determined (approximately 6.1 eV). The scheme of genealogy and arrangement of the plane zones of Y 2 O 3 , in which a substantial role is attributed to interaction of 5s and 4d states of yttrium cations, is proposed and discussed at the qualitative level. The range of the beginning of fundamental absorption (hν > or approximately 7.5 eV) was determined for YAlO 3 . The composition dependence of the width of the forbidden zone of aluminated Ysub(x)Alsub(y)Osub(z) is plotted

  14. Structural and electrical characterization of BiFeO3-NaTaO3 multiferroic

    International Nuclear Information System (INIS)

    Mohanty, Suchismita; Choudhary, R.N.P.; Parida, B.N.; Padhee, R.

    2014-01-01

    Using a standard high-temperature solid-state reaction technique, polycrystalline samples of (Bi 1-x , Na x ) (Fe 1-x , Ta x ) O 3 (x = 0.0, 0.5) were prepared. The formation of the desired materials was confirmed by X-ray diffraction. The surface texture of the prepared materials recorded by scanning electron microscope exhibits a uniform grain distribution with small voids suggesting the formation of high-density pellet samples. The impedance and dielectric properties of the materials were investigated as a function of temperature and frequency. The relative dielectric constant and loss tangent of BiFeO 3 decrease on addition of NaTaO 3 (x = 0.5). The effect of addition of NaTaO 3 on grain and grain boundary contributions in the resistive and capacitive components of BiFeO 3 was studied using complex impedance spectroscopy. The value of activation energy due to both grain and grain boundary of both the samples is nearly same. The nature of variation of dc conductivity confirms the Arrhenius behavior of the materials. Study of frequency dependence of ac conductivity suggests that the materials obey Jonscher's universal power law and the presence of ionic conductivity. (orig.)

  15. Quenching of I(2P1/2) by O3 and O(3P).

    Science.gov (United States)

    Azyazov, Valeriy N; Antonov, Ivan O; Heaven, Michael C

    2007-04-26

    Oxygen-iodine lasers that utilize electrical or microwave discharges to produce singlet oxygen are currently being developed. The discharge generators differ from conventional chemical singlet oxygen generators in that they produce significant amounts of atomic oxygen. Post-discharge chemistry includes channels that lead to the formation of ozone. Consequently, removal of I(2P1/2) by O atoms and O3 may impact the efficiency of discharge driven iodine lasers. In the present study, we have measured the rate constants for quenching of I(2P1/2) by O(3P) atoms and O3 using pulsed laser photolysis techniques. The rate constant for quenching by O3, (1.8 +/- 0.4) x 10(-12) cm3 s-1, was found to be a factor of 5 smaller than the literature value. The rate constant for quenching by O(3P) was (1.2 +/- 0.2) x 10(-11) cm3 s-1.

  16. High quality TbMnO3 films deposited on YAlO3

    International Nuclear Information System (INIS)

    Glavic, Artur; Voigt, Joerg; Persson, Joerg; Su, Yixi; Schubert, Juergen; Groot, Joost de; Zande, Willi; Brueckel, Thomas

    2011-01-01

    Research highlights: → We found a good substrate and suitable deposition parameters to create untwinned, epitaxial thin films of TbMnO 3 . → Laboratory experiments prove the crystalline quality of the films. → We were able to measure the micro magnetic structure in the films by polarized neutron diffraction (to our knowledge the first neutron investigations on TbMnO 3 thin films). - Abstract: High quality thin films of TbMnO 3 were grown by pulsed laser deposition on orthorhombicYAlO 3 (1 0 0). The interface and surface roughness of a 55 nm thick film were probed by X-ray reflectometry and atomic force microscopy, yielding a roughness of 1 nm. X-ray diffraction revealed untwinned films and a small mosaic spread of 0.04 o and 0.2 o for out-of-plane and in-plane reflections, respectively. This high degree of epitaxy was also confirmed by Rutherford backscattering spectrometry. Using polarized neutron diffraction we could identify a magnetic structure with the propagation vector (0 0.27 0), identical to the bulk magnetic structure of TbMnO 3 .

  17. Subsolidus phase relations of Bi2O3-Nd2O3-CuO

    International Nuclear Information System (INIS)

    Sun Yezhou

    1997-01-01

    The subsolidus phase relations of the Bi 2 O 3 -Nd 2 O 3 -CuO ternary system and its binary systems along with crystallographic parameters of the compounds were investigated by X-ray powder diffraction and differential thermal analysis. The room temperature section of the phase diagram of the Bi 2 O 3 -Nd 2 O 3 -CuO system can be divided into two diphase regions and six triphase regions. No ternary compound was found. There exist two solid solutions (α, β) and a compound Bi 0.55 Nd 0.45 O 1.5 in the (Bi 2 O 2 ) 1-x (Nd 2 O 3 ) x system. Both solid solution α (0.05≤x≤0.30) and β (0.53≤x≤0.73) belong to the rhombohedral system (R3m). The lattice parameters represented by a hexagonal cell are a=3.9832(4), c=27.536(5) A for Bi 0.8 Nd 0.2 O 1.5 (α phase) and a=3.8826(3), c=9.727(1) A for Bi 0.4 Nd 0.8 O 1.5 (β phase). The Bi 0.55 Nd 0.45 O 1.5 compound crystallizes in a face-centered cubic (f.c.c.) lattice with a=5.5480(2) A. (orig.)

  18. Structural and Physical Properties of Fe2O3-B2O3-V2O5 Glasses

    Directory of Open Access Journals (Sweden)

    Virender Kundu

    2008-01-01

    Full Text Available The structural and physical properties of xFe2O3-(40-x B2O3-60V2O5  (0≤x≤20 glass system have been investigated. The samples were prepared by normal melt-quench technique. The structural changes were inferred by means of FTIR by monitoring the infrared (IR spectra in the spectral range 600–4000 cm-1. The absence of boroxol ring (806 cm-1 in the present glass system suggested that these glasses consist of randomly connected BO3 and BO4 units. The conversion of BO3 to BO4 and VO5 to VO4 tetrahedra along with the formation of non-bridging oxygen's (NBOs attached to boron and vanadium takes place in the glasses under investigation. The density and molar volume of the present glass system were found to depend on Fe2O3 content. DC conductivity of the glass system has been determined in the temperature range 310–500 K. It was found that the general behavior of electrical conductivity was similar for all glass compositions and found to increase with increasing iron content. The parameters such as activation energy, average separation between transition metal ions (TMIs, polaron radius, and so forth have been calculated in adiabatic region and are found consistent with Mott's model of phonon-assisted polaronic hopping.

  19. Atomic structures of Ruddlesden-Popper faults in LaCoO3/SrRuO3 multilayer thin films induced by epitaxial strain

    Science.gov (United States)

    Wang, Wei; Zhang, Hui; Shen, Xi; Guan, Xiangxiang; Yao, Yuan; Wang, Yanguo; Sun, Jirong; Yu, Richeng

    2018-05-01

    In this paper, scanning transmission electron microscopy is used to study the microstructures of the defects in LaCoO3/SrRuO3 multilayer films grown on the SrTiO3 substrates, and these films have different thickness of SrRuO3 (SRO) layers. Several types of Ruddlesden-Popper (R.P.) faults at an atomic level are found, and these chemical composition fluctuations in the growth process are induced by strain fields originating from the film-film and film-substrate lattice mismatches. Furthermore, we propose four types of structural models based on the atomic arrangements of the R.P. planar faults, which severely affect the functional properties of the films.

  20. Formation of epitaxial Al 2O 3/NiAl(1 1 0) films: aluminium deposition

    Science.gov (United States)

    Lykhach, Y.; Moroz, V.; Yoshitake, M.

    2005-02-01

    Structure of epitaxial Al 2O 3 layers formed on NiAl(1 1 0) substrates has been studied by means of reflection high-energy electron diffraction (RHEED). The elucidated structure was compared to the model suggested for 0.5 nm-thick Al 2O 3 layers [K. Müller, H. Lindner, D.M. Zehner, G. Ownby, Verh. Dtsch. Phys. Ges. 25 (1990) 1130; R.M. Jaeger, H. Kuhlenbeck, H.J. Freund, Surf. Sci. 259 (1991) 235]. The stepwise growth of Al 2O 3 film, involving deposition and subsequent oxidation of aluminium onto epitaxial 0.5 nm-thick Al 2O 3 layers, has been investigated. Aluminium was deposited at room temperature, whereas its oxidation took place during annealing at 1070 K. The Al 2O 3 thickness was monitored by means of Auger electron spectroscopy (AES). It was found that Al 2O 3 layer follows the structure of 0.5 nm thick Al 2O 3 film, although a tilting of Al 2O 3(1 1 1) surface plane with respect to NiAl(1 1 0) surface appeared after Al deposition.

  1. Evidence for ultrafast outflows in radio-quiet AGNs - III. Location and energetics

    Science.gov (United States)

    Tombesi, F.; Cappi, M.; Reeves, J. N.; Braito, V.

    2012-05-01

    Using the results of a previous X-ray photoionization modelling of blueshifted Fe K absorption lines on a sample of 42 local radio-quiet AGNs observed with XMM-Newton, in this Letter we estimate the location and energetics of the associated ultrafast outflows (UFOs). Due to significant uncertainties, we are essentially able to place only lower/upper limits. On average, their location is in the interval ˜0.0003-0.03 pc (˜ 102-104rs) from the central black hole, consistent with what is expected for accretion disc winds/outflows. The mass outflow rates are constrained between ˜0.01 and 1 M⊙ yr-1, corresponding to >rsim5-10 per cent of the accretion rates. The average lower/upper limits on the mechanical power are log? 42.6-44.6 erg s-1. However, the minimum possible value of the ratio between the mechanical power and bolometric luminosity is constrained to be comparable or higher than the minimum required by simulations of feedback induced by winds/outflows. Therefore, this work demonstrates that UFOs are indeed capable to provide a significant contribution to the AGN cosmological feedback, in agreement with theoretical expectations and the recent observation of interactions between AGN outflows and the interstellar medium in several Seyfert galaxies.

  2. Evidence for Ultra-Fast Outflows in Radio-Quiet AGNs: III - Location and Energetics

    Science.gov (United States)

    Tombesi, F.; Cappi, M.; Reeves, J. N.; Braito, V.

    2012-01-01

    Using the results of a previous X-ray photo-ionization modelling of blue-shifted Fe K absorption lines on a sample of 42 local radio-quiet AGNs observed with XMM-Newton, in this letter we estimate the location and energetics of the associated ultrafast outflows (UFOs). Due to significant uncertainties, we are essentially able to place only lower/upper limits. On average, their location is in the interval approx.0.0003-0.03pc (approx.10(exp 2)-10(exp 4)tau(sub s) from the central black hole, consistent with what is expected for accretion disk winds/outflows. The mass outflow rates are constrained between approx.0.01- 1 Stellar Mass/y, corresponding to approx. or >5-10% of the accretion rates. The average lower-upper limits on the mechanical power are logE(sub K) approx. or = 42.6-44.6 erg/s. However, the minimum possible value of the ratio between the mechanical power and bolometric luminosity is constrained to be comparable or higher than the minimum required by simulations of feedback induced by winds/outflows. Therefore, this work demonstrates that UFOs are indeed capable to provide a significant contribution to the AGN r.osmological feedback, in agreement with theoretical expectations and the recent observation of interactions between AGN outflows and the interstellar medium in several Seyferts galaxies .

  3. Photocatalytic Degradation of Methyl Orange on Bi2O3 and Ag2O-Bi2O3 Nano Photocatalysts

    Directory of Open Access Journals (Sweden)

    Seyed Ali Hosseini

    2017-04-01

    Full Text Available The photocatalytic activity of Bi2O3 and Ag2O-Bi2O3 was evaluated by degradation of aqueous methyl orange as a model dye effluent. Bi2O3 was synthesized using chemical precipitation method. Structural analysis revealed that Bi2O3 contain a unique well-crystallized phase and the average crystallite size of 22.4 nm. The SEM analysis showed that the size of Bi2O3 particles was mainly in the range of 16-22 nm. The most important variables affecting the photocatalytic degradation of dyes, namely reaction time, initial pH and catalyst dosage were studied, and their optimal amounts were found at 60 min, 5.58 and 0.025 g, respectively. A good correlation was found between experimental and predicted responses, confirming the reliability of the model. Incorporation of Ag2O in the structure of composite caused decreasing band gap and its response to visible light. Because a high percentage of sunlight is visible light, hence Ag2O-Bi2O3 nano-composite could be used as an efficient visible light driven photocatalyst for degradation of dye effluents by sunlight. Copyright © 2017 BCREC GROUP. All rights reserved Received: 15th August 2016; Revised: 20th December 2016; Accepted: 21st December 2016 How to Cite: Hosseini, S.A., Saeedi, R. (2017. Photocatalytic Degradation of Methyl Orange on Bi2O3 and Ag2O-Bi2O3 Nano Photocatalysts. Bulletin of Chemical Reaction Engineering & Catalysis, 12 (1: 96-105 (doi:10.9767/bcrec.12.1.623.96-105 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.12.1.623.96-105

  4. Octahedral rotations in strained LaAlO3/SrTiO3 (001 heterostructures

    Directory of Open Access Journals (Sweden)

    T. T. Fister

    2014-02-01

    Full Text Available Many complex oxides display an array of structural instabilities often tied to altered electronic behavior. For oxide heterostructures, several different interfacial effects can dramatically change the nature of these instabilities. Here, we investigate LaAlO3/SrTiO3 (001 heterostructures using synchrotron x-ray scattering. We find that when cooling from high temperature, LaAlO3 transforms from the Pm3¯m to the Imma phase due to strain. Furthermore, the first 4 unit cells of the film adjacent to the substrate exhibit a gradient in rotation angle that can couple with polar displacements in films thinner than that necessary for 2D electron gas formation.

  5. Magnetism Control by Doping in LaAlO3/SrTiO3 Heterointerfaces.

    Science.gov (United States)

    Yan, Hong; Zhang, Zhaoting; Wang, Shuanhu; Wei, Xiangyang; Chen, Changle; Jin, Kexin

    2018-04-25

    Magnetic two-dimensional electron gases at the oxide interfaces are always one of the key issues in spintronics, giving rise to intriguing magnetotransport properties. However, reports about magnetic two-dimensional electron gases remain elusive. Here, we obtain the magnetic order of LaAlO 3 /SrTiO 3 systems by introducing magnetic dopants at the La site. The transport properties with a characteristic of metallic behavior at the interfaces are investigated. More significantly, magnetic-doped samples exhibit obvious magnetic hysteresis loops and the mobility is enhanced. Meanwhile, the photoresponsive experiments are realized by irradiating all samples with a 360 nm light. Compared to magnetism, the effects of dopants on photoresponsive and relaxation properties are negligible because the behavior originates from SrTiO 3 substrates. This work paves a way for revealing and better controlling the magnetic properties of oxide heterointerfaces.

  6. Variations of surface ozone at Ieodo Ocean Research Station in the East China Sea and the influence of Asian outflows

    Science.gov (United States)

    Han, J.; Shin, B.; Lee, M.; Hwang, G.; Kim, J.; Shim, J.; Lee, G.; Shim, C.

    2015-11-01

    Ieodo Ocean Research Station (IORS), a research tower (~ 40 m a.s.l.) for atmospheric and oceanographic observations, is located in the East China Sea (32.07° N, 125.10° E). The IORS is almost equidistant from South Korea, China, and Japan and, therefore, it is an ideal place to observe Asian outflows without local emission effects. The seasonal variation of ozone was distinct, with a minimum in August (37 ppbv) and two peaks in April and October (62 ppbv), and was largely affected by the seasonal wind pattern over east Asia. At IORS, six types of air masses were distinguished with different levels of O3 concentrations by the cluster analysis of backward trajectories. Marine air masses from the Pacific Ocean represent a relatively clean background air with a lowest ozone level of 32 ppbv, which was most frequently observed in summer (July-August). In spring (March-April) and winter (December-February), the influence of Chinese outflows was dominant with higher ozone concentrations of 62 and 49 ppbv, respectively. This study confirms that the influence of Chinese outflows was the main factor determining O3 levels at IORS and its extent was dependent on meteorological state, particularly at a long-term scale.

  7. Universality of electron mobility in LaAlO3/SrTiO3 and bulk SrTiO3

    Science.gov (United States)

    Trier, Felix; Reich, K. V.; Christensen, Dennis Valbjørn; Zhang, Yu; Tuller, Harry L.; Chen, Yunzhong; Shklovskii, B. I.; Pryds, Nini

    2017-08-01

    Metallic LaAlO3/SrTiO3 (LAO/STO) interfaces attract enormous attention, but the relationship between the electron mobility and the sheet electron density, ns, is poorly understood. Here, we derive a simple expression for the three-dimensional electron density near the interface, n3 D , as a function of ns and find that the mobility for LAO/STO-based interfaces depends on n3 D in the same way as it does for bulk doped STO. It is known that undoped bulk STO is strongly compensated with N ≃5 ×1018 cm-3 background donors and acceptors. In intentionally doped bulk STO with a concentration of electrons n3 DN , the mobility collapses because scattering happens on n3 D intentionally introduced donors. For LAO/STO, the polar catastrophe which provides electrons is not supposed to provide an equal number of random donors and thus the mobility should be larger. The fact that the mobility is still the same implies that for the LAO/STO, the polar catastrophe model should be revisited.

  8. Better Than Nothing: A Rational Approach for Minimizing the Impact of Outflow Strategy on Cerebrovascular Simulations.

    Science.gov (United States)

    Chnafa, C; Brina, O; Pereira, V M; Steinman, D A

    2018-02-01

    Computational fluid dynamics simulations of neurovascular diseases are impacted by various modeling assumptions and uncertainties, including outlet boundary conditions. Many studies of intracranial aneurysms, for example, assume zero pressure at all outlets, often the default ("do-nothing") strategy, with no physiological basis. Others divide outflow according to the outlet diameters cubed, nominally based on the more physiological Murray's law but still susceptible to subjective choices about the segmented model extent. Here we demonstrate the limitations and impact of these outflow strategies, against a novel "splitting" method introduced here. With our method, the segmented lumen is split into its constituent bifurcations, where flow divisions are estimated locally using a power law. Together these provide the global outflow rate boundary conditions. The impact of outflow strategy on flow rates was tested for 70 cases of MCA aneurysm with 0D simulations. The impact on hemodynamic indices used for rupture status assessment was tested for 10 cases with 3D simulations. Differences in flow rates among the various strategies were up to 70%, with a non-negligible impact on average and oscillatory wall shear stresses in some cases. Murray-law and splitting methods gave flow rates closest to physiological values reported in the literature; however, only the splitting method was insensitive to arbitrary truncation of the model extent. Cerebrovascular simulations can depend strongly on the outflow strategy. The default zero-pressure method should be avoided in favor of Murray-law or splitting methods, the latter being released as an open-source tool to encourage the standardization of outflow strategies. © 2018 by American Journal of Neuroradiology.

  9. Advection-dominated Inflow/Outflows from Evaporating Accretion Disks.

    Science.gov (United States)

    Turolla; Dullemond

    2000-03-01

    In this Letter we investigate the properties of advection-dominated accretion flows (ADAFs) fed by the evaporation of a Shakura-Sunyaev accretion disk (SSD). In our picture, the ADAF fills the central cavity evacuated by the SSD and extends beyond the transition radius into a coronal region. We find that, because of global angular momentum conservation, a significant fraction of the hot gas flows away from the black hole, forming a transsonic wind, unless the injection rate depends only weakly on radius (if r2sigma&d2;~r-xi, xiBernoulli number of the inflowing gas is negative if the transition radius is less, similar100 Schwarzschild radii, so matter falling into the hole is gravitationally bound. The ratio of inflowing to outflowing mass is approximately 1/2, so in these solutions the accretion rate is of the same order as in standard ADAFs and much larger than in advection-dominated inflow/outflow models. The possible relevance of evaporation-fed solutions to accretion flows in black hole X-ray binaries is briefly discussed.

  10. Multiferroic properties in NdFeO3-PbTiO3 solid solutions

    Science.gov (United States)

    Kumar, Sunil; Pal, Jaswinder; Kaur, Shubhpreet; Agrawal, P.; Singh, Mandeep; Singh, Anupinder

    2018-05-01

    The x(NdFeO3) - 1-x(PbTiO3) where x = 0.2 solid solution was prepared using solid state reaction route. The X-ray diffraction (XRD) data reveals the single phase formation. The microstructure shows grain growth with lesser porosity. The energy dispersive analysis confirms the presence of elements in stochiometric proportion. The polarization vs. Electric field loop estabilished a ferroelectric type behavior but lossy in nature. This lossy nature may be due to the presence of large leakage current in solid solution. The Magnetization vs. Magnetic field plot exhibits a unsaturated hysteriss loop indicates that the sample is not purely ferromagnetic.

  11. Radiative forcing for changes in tropospheric O3

    International Nuclear Information System (INIS)

    Grossman, A.S.; Wuebbles, D.J.; Grant, K.E.

    1994-06-01

    We have evaluated the radiative forcing for assumed changes in tropospheric O 3 in the 500-1650 cm -1 wavenumber range. The radiative forcing calculations were performed as a function of latitude as well as for a globally and seasonally averaged model atmosphere, both in a clear sky approximation and in a model containing a representative cloud distribution. The scenarios involved radiative forcing calculations for O 3 at normal atmospheric abundance and at a tropospheric abundance depleted by 25 ppbv, at each altitude, for all northern hemisphere latitudes. Normal abundances of H 2 O, CO 2 , CH 4 , and N 2 O were included in the calculations. The IR radiative forcing was calculated using a correlated k-distribution radiative transfer model. The tropospheric radiative forcing values are compared to the IPCC formulae for ozone tropospheric forcing as well as other published values to determine the validity of the correlated k-distribution approach to the radiative forcing calculations. The results for the global average atmosphere show agreement with previous results to the order of 10 percent. We conclude that the O 3 forcing is linear in the background abundance and that the radiative forcing for ozone for the globally averaged atmosphere and the latitude averaged radiative forcing in the clear sky approximation are in agreement to within 10 percent. For the case of an atmosphere in which the tropospheric ozone has been depleted by 25 ppbv at all altitudes in the northern hemisphere, the mid latitude zone contributes ∼50 percent of the forcing, tropic zone contributes ∼37 percent of the forcing and the polar zone contributes ∼13 percent of the total forcing

  12. ATOMIC HYDROGEN IN A GALACTIC CENTER OUTFLOW

    Energy Technology Data Exchange (ETDEWEB)

    McClure-Griffiths, N. M.; Green, J. A.; Hill, A. S. [Australia Telescope National Facility, CSIRO Astronomy and Space Science, Marsfield, NSW 2122 (Australia); Lockman, F. J. [National Radio Astronomy Observatory, Green Bank, WV 24944 (United States); Dickey, J. M. [School of Physics and Mathematics, University of Tasmania, TAS 7001 (Australia); Gaensler, B. M.; Green, A. J., E-mail: naomi.mcclure-griffiths@csiro.au [Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006 (Australia)

    2013-06-10

    We describe a population of small, high-velocity, atomic hydrogen clouds, loops, and filaments found above and below the disk near the Galactic center. The objects have a mean radius of 15 pc, velocity widths of {approx}14 km s{sup -1}, and are observed at |z| heights up to 700 pc. The velocity distribution of the clouds shows no signature of Galactic rotation. We propose a scenario where the clouds are associated with an outflow from a central star-forming region at the Galactic center. We discuss the clouds as entrained material traveling at {approx}200 km s{sup -1} in a Galactic wind.

  13. New noninvasive treatment for prostate outflow obstruction

    International Nuclear Information System (INIS)

    Richards, D.; Milroy, E.; Chapple, C.; Eldin, A.; Wallstein, H.

    1989-01-01

    Sixteen patients with prostatic outflow obstruction underwent implantation of the Wallstent endoprothesis, a woven mesh of fine stainless steel, mounted on a 9-F delivery system with an unconstrained diameter of 14 mm. The stent was inserted under local anesthesia, and placement was guided by linear transrectal US and flexible urethroscopy. In no patient was the distal sphincter mechanism compromised. In four, stent balloon dilation was needed. Urodynamic parameters (especially flow rate, voiding detrusor pressure, and postvoid residual) improved in all patients. Our experience showed the Wallstent endoprosthesis to be a safe, clinically acceptable, and minimally invasive alternative to prostatectomy

  14. Interferometric Mapping of Perseus Outflows with MASSES

    Science.gov (United States)

    Stephens, Ian; Dunham, Michael; Myers, Philip C.; MASSES Team

    2017-01-01

    The MASSES (Mass Assembly of Stellar Systems and their Evolution with the SMA) survey, a Submillimeter Array (SMA) large-scale program, is mapping molecular lines and continuum emission about the 75 known Class 0/I sources in the Perseus Molecular Cloud. In this talk, I present some of the key results of this project, with a focus on the CO(2-1) maps of the molecular outflows. In particular, I investigate how protostars inherit their rotation axes from large-scale magnetic fields and filamentary structure.

  15. ATOMIC HYDROGEN IN A GALACTIC CENTER OUTFLOW

    International Nuclear Information System (INIS)

    McClure-Griffiths, N. M.; Green, J. A.; Hill, A. S.; Lockman, F. J.; Dickey, J. M.; Gaensler, B. M.; Green, A. J.

    2013-01-01

    We describe a population of small, high-velocity, atomic hydrogen clouds, loops, and filaments found above and below the disk near the Galactic center. The objects have a mean radius of 15 pc, velocity widths of ∼14 km s –1 , and are observed at |z| heights up to 700 pc. The velocity distribution of the clouds shows no signature of Galactic rotation. We propose a scenario where the clouds are associated with an outflow from a central star-forming region at the Galactic center. We discuss the clouds as entrained material traveling at ∼200 km s –1 in a Galactic wind.

  16. GGD 37: AN EXTREME PROTOSTELLAR OUTFLOW

    International Nuclear Information System (INIS)

    Green, J. D.; Watson, D. M.; Forrest, W. J.; Kim, K. H.; Bergin, E.; Maret, S.; Melnick, G.; Tolls, V.; Sonnentrucker, P.; Sargent, B. A.; Raines, S. N.

    2011-01-01

    We present the first Spitzer-IRS spectral maps of the Herbig-Haro flow GGD 37 detected in lines of [Ne III], [O IV], [Ar III], and [Ne V]. The detection of extended [O IV] (55 eV) and some extended emission in [Ne V] (97 eV) indicates a shock temperature in excess of 100,000 K, in agreement with X-ray observations, and a shock speed in excess of 200 km s -1 . The presence of an extended photoionization or collisional ionization region indicates that GGD 37 is a highly unusual protostellar outflow.

  17. Microstructure and dielectric parameters of epitaxial SrRuO3/BaTiO3/SrRuO3 heterostructures

    Science.gov (United States)

    Boikov, Yu. A.; Claeson, T.

    2001-05-01

    Epitaxial films of ferroelectric barium titanate are desirable in a number of applications but their properties are inferior to those of bulk material. Relations between microstructure and dielectric properties may give better understanding of limitations. Trilayer heterostructures SrRuO3/BaTiO3/SrRuO3 were grown by laser ablation on (100)LaAlO3 and (100)MgO substrates. The BaTiO3 layer was granular in structure. When grown on (100)SrRuO3/(100)LaAlO3, it was preferentially a-axis oriented due to tensile mechanical stress. Using (100)MgO as a substrate, on the other hand, produced a mixture of about equal value of a-axis and c-axis oriented grains of BaTiO3. The dielectric permittivity, ɛ, of the BaTiO3 layer was almost twice as large, at T>200 K and f=100 kHz, for the LaAlO3 substrate as compared to the MgO one. Its maximum value (ɛ/ɛ0≈6200) depended on temperature of growth, grain size, and electric field and compares well with optimal values commonly used for ceramic material. The maximum in the ɛ(T) shifted from about 370 to 320 K when the grain size in the BaTiO3 film decreased from 100 to 40 nm. At T300 K, hysteresis loops in polarization versus electric field were roughly symmetric. The BaTiO3 films grown on (100)SrRuO3/(100)MgO exhibit the largest remnant polarizations and coercive fields in the temperature range 100-380 K.

  18. Incision of the Jezero Crater Outflow Channel by Fluvial Sediment Transport

    Science.gov (United States)

    Holo, S.; Kite, E. S.

    2017-12-01

    Jezero crater, the top candidate landing site for the Mars 2020 rover, once possessed a lake that over-spilled and eroded a large outflow channel into the Eastern rim. The Western deltaic sediments that would be the primary science target of the rover record a history of lake level, which is modulated by the inflow and outflow channels. While formative discharges for the Western delta exist ( 500 m3/s), little work has been done to see if these flows are the same responsible for outflow channel incision. Other models of the Jezero outflow channel incision assume that a single rapid flood (incision timescales of weeks), with unknown initial hydraulic head and no discharge into the lake (e.g. from the inflow channels or the subsurface), incised an open channel with discharge modulated by flow over a weir. We present an alternate model where, due to an instability at the threshold of sediment motion, the incision of the outflow channel occurs in concert with lake filling. In particular, we assume a simplified lake-channel-valley system geometry and that the channel is hydraulically connected to the filling/draining crater lake. Bed load sediment transport and water discharge through the channel are quantified using the Meyer-Peter and Mueller relation and Manning's law respectively. Mass is conserved for both water and sediment as the lake level rises/falls and the channel incises. This model does not resolve backwater effects or concavity in the alluvial system, but it does capture the non-linear feedbacks between lake draining, erosion rate, channel flow rate, and slope relaxation. We identify controls on incision of the outflow channel and estimate the time scale of outflow channel formation through a simple dynamical model. We find that the observed 300m of channel erosion can be reproduced in decades to centuries of progressive bed load as the delta forming flows fill the lake. This corresponds to time scales on the order of or smaller than the time scale

  19. Human cerebral venous outflow pathway depends on posture and central venous pressure

    DEFF Research Database (Denmark)

    Gisolf, J; van Lieshout, J J; van Heusden, K

    2004-01-01

    Internal jugular veins are the major cerebral venous outflow pathway in supine humans. In upright humans the positioning of these veins above heart level causes them to collapse. An alternative cerebral outflow pathway is the vertebral venous plexus. We set out to determine the effect of posture...... and during a Valsalva manoeuvre in both body positions, correlate highly with model simulation of the jugular cross-sectional area (R(2) = 0.97). The results suggest that the cerebral venous flow distribution depends on posture and CVP: in supine humans the internal jugular veins are the primary pathway...

  20. Compact binary merger and kilonova: outflows from remnant disc

    Science.gov (United States)

    Yi, Tuan; Gu, Wei-Min; Liu, Tong; Kumar, Rajiv; Mu, Hui-Jun; Song, Cui-Ying

    2018-05-01

    Outflows launched from a remnant disc of compact binary merger may have essential contribution to the kilonova emission. Numerical calculations are conducted in this work to study the structure of accretion flows and outflows. By the incorporation of limited-energy advection in the hyper-accretion discs, outflows occur naturally from accretion flows due to imbalance between the viscous heating and the sum of the advective and radiative cooling. Following this spirit, we revisit the properties of the merger outflow ejecta. Our results show that around 10-3 ˜ 10-1 M⊙ of the disc mass can be launched as powerful outflows. The amount of unbound mass varies with the disc mass and the viscosity. The outflow-contributed peak luminosity is around 1040 ˜ 1041 erg s-1. Such a scenario can account for the observed kilonovae associated with short gamma-ray bursts, including the recent event AT2017gfo (GW170817).

  1. Towards Isotropic Vortex Pinning in YBCO Films with Double-doping BHO-Y2O3 and BZO-Y2O3 Artificial Pining Centers

    Science.gov (United States)

    Gautam, Bibek; Sebastian, Mary Ann; Chen, Shihong; Haugan, Timothy; Chen, Yanbin; Xing, Zhongwen; Prestigiacomo, Joseph; Osofsky, Mike; Wu, Judy

    2017-12-01

    Strong and isotropic vortex pinning landscape is demanded for high field applications of YaBa2Cu3O7-x (YBCO) epitaxial thin films. Double-doping (DD) of artificial pinning centers (APCs) of mixed morphologies has been identified as a viable approach for this purpose. This work presents a comparative study on the transport critical current density J c (H, θ) of 3.0 vol.%Y2O3+2.0 (or 6.0) vol.% BaZrO3 (BZO DD) and 3.0 vol.%Y2O3+ 2.0 (or 6.0) vol.% BaHfO3 (BHO DD) films. Based on the elastic strain model, BaHfO3 (BHO) nanorods have lower rigidity than their BaZrO3 (BZO) counterparts, which means their c-axis alignment is more susceptible to the local strain generated by the secondary dopant of Y2O3. Considering the increasing strain field with higher BZO (or BHO doping), the higher susceptibility may result in a large portion of the BHO APCs moving away from perfect c-axis alignment and enhancing isotropic pinning with respect to the H orientation. This is confirmed since the BHO DD films illustrate a less pronounced J c peak at H//c-axis and hence more isotropic J c(θ) than their BZO DD counterparts. At 9.0 T, the variation of the J c across the entire θ range (0-90 degree) is less than 18% for the BHO DD film, in contrast to about 100% for the 2.0 vol.% BZO DD counterpart. At the higher BHO concentration of 6.0 vol.%, this higher tunability of the Y2O3 leads to increased ab-plane aligned BHO APCs and hence enhanced J c at H//ab-plane.

  2. Influence of Al2O3 reinforcement on precipitation kinetic of Cu–Cr nanocomposite

    International Nuclear Information System (INIS)

    Sheibani, S.; Ataie, A.; Heshmati-Manesh, S.; Caballero, A.; Criado, J.M.

    2011-01-01

    Highlights: ► Cr precipitation in Cu-1 wt.% Cr solid solution is based on nucleation and growth models. ► The overall ageing process is accelerated by the presence of Al 2 O 3 reinforcement. ► Al 2 O 3 –Cu interfaces act as primary nucleation sites. ► Structural defects act as secondary nucleation sites. - Abstract: In this paper, the kinetic of precipitation process in mechanically alloyed Cu-1 wt.% Cr and Cu-1 wt.% Cr/3 wt.% Al 2 O 3 solid solution was compared using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The ageing kinetics in Cu–Cr and Cu–Cr/Al 2 O 3 can be described using Johnson–Mehl–Avrami (JMA) and Sestak–Berggren (SB) models, respectively. These different behaviors have been discussed in details. It was found that in presence of Al 2 O 3 reinforcement, the ageing activation energy is decreased and the overall ageing process is accelerated. This behavior is probably due to higher dislocation density previously obtained during ball milling and Al 2 O 3 –Cu interface. TEM observations confirm that Al 2 O 3 –Cu interface and structural defects act as a primary and secondary nucleation sites, respectively.

  3. New exposure-based metric approach for evaluating O3 risk to North American aspen forests

    International Nuclear Information System (INIS)

    Percy, K.E.; Nosal, M.; Heilman, W.; Dann, T.; Sober, J.; Legge, A.H.; Karnosky, D.F.

    2007-01-01

    The United States and Canada currently use exposure-based metrics to protect vegetation from O 3 . Using 5 years (1999-2003) of co-measured O 3 , meteorology and growth response, we have developed exposure-based regression models that predict Populus tremuloides growth change within the North American ambient air quality context. The models comprised growing season fourth-highest daily maximum 8-h average O 3 concentration, growing degree days, and wind speed. They had high statistical significance, high goodness of fit, include 95% confidence intervals for tree growth change, and are simple to use. Averaged across a wide range of clonal sensitivity, historical 2001-2003 growth change over most of the 26 M ha P. tremuloides distribution was estimated to have ranged from no impact (0%) to strong negative impacts (-31%). With four aspen clones responding negatively (one responded positively) to O 3 , the growing season fourth-highest daily maximum 8-h average O 3 concentration performed much better than growing season SUM06, AOT40 or maximum 1 h average O 3 concentration metrics as a single indicator of aspen stem cross-sectional area growth. - A new exposure-based metric approach to predict O 3 risk to North American aspen forests has been developed

  4. Misalignment of Magnetic Fields and Outflows in Protostellar Cores

    OpenAIRE

    Hull, Charles L. H.; Plambeck, Richard L.; Bolatto, Alberto D.; Bower, Geoffrey C.; Carpenter, John M.; Crutcher, Richard M.; Fiege, Jason D.; Franzmann, Erika; Hakobian, Nicholas S.; Heiles, Carl; Houde, Martin; Hughes, A. Meredith; Jameson, Katherine; Kwon, Woojin; Lamb, James W.

    2013-01-01

    We present results of λ1.3 mm dust-polarization observations toward 16 nearby, low-mass protostars, mapped with ~2."5 resolution at CARMA. The results show that magnetic fields in protostellar cores on scales of ~1000 AU are not tightly aligned with outflows from the protostars. Rather, the data are consistent with scenarios where outflows and magnetic fields are preferentially misaligned (perpendicular), or where they are randomly aligned. If one assumes that outflows emerge along the rotati...

  5. Molecular outflows in the L1641 region of Orion

    International Nuclear Information System (INIS)

    Morgan, J.A.

    1990-01-01

    Little is known about the interaction between molecular outflows associated with young stellar objects and the parent molecular cloud that produced them. This is because molecular outflows are a recently discovered phenomenon and, so, have not had their global properties studied in great detail and molecular clouds were not mapped to sufficiently high spatial resolution to resolve the interaction. The interaction between molecular outflows and the L1641 molecular cloud is addressed by both identifying and mapping all the molecular outflows as well as the detailed structure of the cloud. Candidate molecular outflows were found from single point 12-CO observations of young stellar objects identified from the IRAS survey data. The candidate sources were then mapped to confirm their molecular outflow nature. From these maps, molecular outflow characteristics such as their morphology, orientation, and energetics were determined. In addition, the Orion molecular cloud was mapped to compare directly with the molecular outflows. The molecular outflows identified were found to have rising infrared spectra, radio continuum emission that suggests a stellar wind or optically thick H II region, and molecular line strengths that indicate that they are embedded within a very dense environment. The lack of an optical counterpart for many molecular outflows suggests that they occur at the earliest stages of stellar evolution. The lack of an optical counterpart for many molecular outflows suggest that they occur at the earliest stages of stellar evolution. The orientations of the molecular outflows appear to lie in no preferred direction and they have shapes that indicate that the molecular cloud is responsible for determining their direction and collimation

  6. Cooper Pair Writing at the LaAlO3/ SrTiO 3 Interface

    Science.gov (United States)

    Cen, Cheng; Bogorin, Daniela F.; Bark, Chung Wung; Folkman, Chad M.; Eom, Chang-Beom; Levy, Jeremy

    2011-03-01

    Superconducting semiconductors offer unique ways to exert electrostatic control over macroscopic quantum phases. The recently demonstrated nanoscale control over conductivity at the LaAl O3 / SrTi O3 interface raises the question of whether nanoscale control over superconducting phases can be realized. Here we report low-temperature magnetotransport experiments on structures defined with nanoscale precision at the LaAl O3 / SrTi O3 interface. A quantum phase transition is observed that is associated with the formation of Cooper pairs, but a finite resistance is observed at the lowest temperatures. Higher mobility interfaces exhibit larger Ginsburg-Landau coherence lengths, a stronger suppression of pairing by magnetic field as well as Shubnikov-de Haas oscillations. Cooper pair localization, spin-orbit coupling, and finite-size effects may factor into an explanation for some of the unusual properties observed. The work is supported by Department of Energy and State of Florida, NSF (DMR-0906443 and DMR-0704022), DOE (DE-FG02-06ER46327) and the Fine Foundation.

  7. Studying the outflow-core interaction with ALMA Cycle 1 observations of the HH 46/47 molecular outflow

    Science.gov (United States)

    Zhang, Yichen; Arce, Hector G.; Mardones, Diego; Dunham, Michael; Garay, Guido; Noriega-Crespo, Alberto; Corder, Stuartt; Offner, Stella; Cabrit, Sylvie

    2016-01-01

    We present ALMA Cycle 1 observations of the HH 46/47 molecular outflow which is driven by a low-mass Class 0/I protostar. Previous ALMA Cycle 0 12CO observation showed outflow cavities produced by the entrainment of ambient gas by the protostellar jet and wide-angle wind. Here we present analysis of observation of 12CO, 13CO, C18O and other species using combined 12m array and ACA observations. The improved angular resolution and sensitivity allow us to detect details of the outflow structure. Specially, we see that the outflow cavity wall is composed of two or more layers of outflowing gas, which separately connect to different shocked regions along the outflow axis inside the cavity, suggesting the outflow cavity wall is composed of multiple shells entrained by a series of jet bow-shock events. The new 13CO and C18O data also allow us to trace relatively denser and slower outflow material than that traced by the 12CO. These species are only detected within about 1 to 2 km/s from the cloud velocity, tracing the outflow to lower velocities than what is possible using only the 12CO emission. Interestingly, the cavity wall of the red lobe appears at very low outflow velocities (as low as ~0.2 km/s). In addition, 13CO and C18O allow us to correct for the CO optical depth, allowing us to obtain more accurate estimates of the outflow mass, momentum and kinetic energy. Applying the optical depth correction significantly increases the previous mass estimate by a factor of 14. The outflow kinetic energy distribution shows that even though the red lobe is mainly entrained by jet bow-shocks, most of the outflow energy is being deposited into the cloud at the base of the outflow cavity rather than around the heads of the bow shocks. The estimated total mass, momentum, and energy of the outflow indicate that the outflow has the ability to disperse the parent core. We found possible evidence for a slowly moving rotating outflow in CS. Our 13CO and C18O observations also trace a

  8. Supernova blast wave within a stellar cluster outflow

    Science.gov (United States)

    Rodríguez-Ramírez, J. C.; Raga, A. C.; Velázquez, P. F.; Rodríguez-González, A.; Toledo-Roy, J. C.

    2014-11-01

    In this paper, we develop a semi-analytic model of a supernova which goes off in the centre of a stellar cluster. The supernova remnant interacts with a stratified, pre-existent outflow produced by the winds of the cluster stars. We compare our semi-analytic model with numerical simulations using the spherically symmetric Euler equations with appropriate mass and energy source terms. We find good agreement between these two approaches, and we find that for typical parameters the blast wave is likely to reach the Taylor-Sedov regime outside the cluster radius. We also calculate the predicted X-ray luminosity of the flow as a function of time, and we obtain its dependence on the outer radius and the number of stars of the cluster.

  9. Effective theory of exotic superconductivity in LaAlO3/SrTiO3 interfaces

    Science.gov (United States)

    Esmailzadeh, Haniyeh; Moghaddam, Ali G.

    2018-05-01

    Motivated by experimental and theoretical works about superconductivity at the oxide interfaces, we provide a simple model for possible unconventional pairings inside the exotic two-dimensional electron gas formed in heterostructures of SrTiO3 and LaAlO3. At the low energy limit, the electron gas at the interfaces is usually modeled with an effective three band model considering of 3d t2g orbitals which are slightly coupled by atomic spin-orbit couplings (SOC). Considering direct superconducting pairing in two higher delocalized bands and by exploiting a perturbative scheme based on canonical transformation, we derive the effective pairing amplitudes with possibly exotic nature inside the localized dxy band as well as various inter-band pairing components. In particular we show that equal-spin triplet pairings are possible between the band dxy and any of other dxz and dyz bands. In addition weaker effective pairings take place inside the localized band itself and between delocalized dxz and dyz bands with singlet and opposite-spin triplet characters. These unconventional effective pairings are indeed mediated by SOC-induced higher order virtual transitions between the bands and particularly into the localized band. Our model suggest that unconventional effective superconductivity is possible at oxide interfaces, simply, due to the special band structure and important role of atomic SOC and perhaps other magnetic effects present at these heterostructures.

  10. Investigation of phase relationships in subsolidus region of Ln2O3-MoO3-B2O3 systems

    International Nuclear Information System (INIS)

    Lysanova, C.V.; Dzhurinskij, B.F.; Komova, M.G.; Tananaev, I.V.

    1983-01-01

    Phase formation in subsolidus region of Ln 2 O 3 -MoO 3 B 2 O 3 systems (Ln-La, Nd) is studied. Three compounds with mixed oxyanions-boratomolybdates of LnMoBO 6 composition (Ln-La, Ce, Pr, Nd), Ln 2 MoB 2 O 9 (Ln-La, Ce, Pr, Nd, Sm, EU, Gde Tb) Ln 6 Mo 3 B 4 0 24 (Ln-Pr, Nd) are revealed and described

  11. Nanosized As2O3/Fe2O3 complexes combined with magnetic fluid hyperthermia selectively target liver cancer cells.

    Science.gov (United States)

    Wang, Zi-Yu; Song, Jian; Zhang, Dong-Sheng

    2009-06-28

    To study the methods of preparing the magnetic nano-microspheres of Fe(2)O(3) and As(2)O(3)/Fe(2)O(3) complexes and their therapeutic effects with magnetic fluid hyperthermia (MFH). Nanospheres were prepared by chemical co-precipitation and their shape and diameter were observed. Hemolysis, micronucleus, cell viability, and LD(50) along with other in vivo tests were performed to evaluate the Fe(2)O(3) microsphere biocompatibility. The inhibition ratio of tumors after Fe(2)O(3) and As(2)O(3)/Fe(2)O(3) injections combined with induced hyperthermia in xenograft human hepatocarcinoma was calculated. Fe(2)O(3) and As(2)O(3)/Fe(2)O(3) particles were round with an average diameter of 20 nm and 100 nm as observed under transmission electron microscope. Upon exposure to an alternating magnetic field (AMF), the temperature of the suspension of magnetic particles increased to 41-51 degrees C, depending on different particle concentrations, and remained stable thereafter. Nanosized Fe(2)O(3) microspheres are a new kind of biomaterial without cytotoxic effects. The LD(50) of both Fe(2)O(3) and As(2)O(3)/Fe(2)O(3) in mice was higher than 5 g/kg. One to four weeks after Fe(2)O(3) and As(2)O(3)/Fe(2)O(3) complex injections into healthy pig livers, no significant differences were found in serum AST, ALT, BUN and Cr levels among the pigs of all groups (P > 0.05), and no obvious pathological alterations were observed. After exposure to alternating magnetic fields, the inhibition ratio of the tumors was significantly different from controls in the Fe(2)O(3) and As(2)O(3)/Fe(2)O(3) groups (68.74% and 82.79%, respectively; P < 0.01). Tumors of mice in treatment groups showed obvious necrosis, while normal tissues adjoining the tumor and internal organs did not. Fe(2)O(3) and As(2)O(3)/Fe(2)O(3) complexes exerted radiofrequency-induced hyperthermia and drug toxicity on tumors without any liver or kidney damage. Therefore, nanospheres are ideal carriers for tumor-targeted therapy.

  12. Y2O3-W Continuous Graded Materials by Co-sedimentation

    Directory of Open Access Journals (Sweden)

    WANG Shi-yang

    2017-09-01

    Full Text Available The raw Y2O3 powder was classified and graded based on modified co-sedimentation mathematical model,using the size distribution of W particles as the known condition. Y2O3-W continuous graded materials with the composition distribution index P values of 1.0, 0.7, 0.3 and 0.1 were prepared by co-sedimentation and hot-pressing. The results show that the Y2O3 powder consistent with the design requirements can be obtained by graduation method. The gradient continuity of materials can be verified by microstructure observation and hardness testing.

  13. High energy transmission of Al2O3 doped with light transition metals

    KAUST Repository

    Schuster, Cosima

    2012-01-31

    The transmission of transparent colored ceramics based on Al2O3doped with light transition metals is measured in the visible and infrared range. To clarify the role of the dopands we perform ab initiocalculations. We discuss the electronic structure and present optical spectra obtained in the independent particle approximation. We argue that the gross spectral features of Co- and Ni-doped Al2O3 samples are described by our model, while the validity of the approach is limited for Cr-doped Al2O3.

  14. First principles calculations for interaction of tyrosine with (ZnO)3 cluster

    Science.gov (United States)

    Singh, Satvinder; Singh, Gurinder; Kaura, Aman; Tripathi, S. K.

    2018-04-01

    First Principles Calculations have been performed to study interactions of Phenol ring of Tyrosine (C6H5OH) with (ZnO)3 atomic cluster. All the calculations have been performed under the Density Functional Theory (DFT) framework. Structural and electronic properties of (ZnO)3/C6H5OH have been studied. Gaussian basis set approach has been adopted for the calculations. A ring type most stable (ZnO)3 atomic cluster has been modeled, analyzed and used for the calculations. The compatibility of the results with previous studies has been presented here.

  15. High energy transmission of Al2O3 doped with light transition metals

    KAUST Repository

    Schuster, Cosima; Klimke, J.; Schwingenschlö gl, Udo

    2012-01-01

    The transmission of transparent colored ceramics based on Al2O3doped with light transition metals is measured in the visible and infrared range. To clarify the role of the dopands we perform ab initiocalculations. We discuss the electronic structure and present optical spectra obtained in the independent particle approximation. We argue that the gross spectral features of Co- and Ni-doped Al2O3 samples are described by our model, while the validity of the approach is limited for Cr-doped Al2O3.

  16. Outflows in the narrow-line region of bright Seyfert galaxies - I. GMOS-IFU data

    Science.gov (United States)

    Freitas, I. C.; Riffel, R. A.; Storchi-Bergmann, T.; Elvis, M.; Robinson, A.; Crenshaw, D. M.; Nagar, N. M.; Lena, D.; Schmitt, H. R.; Kraemer, S. B.

    2018-05-01

    We present two-dimensional maps of emission-line fluxes and kinematics, as well as of the stellar kinematics of the central few kpc of five bright nearby Seyfert galaxies - Mrk 6, Mrk 79, Mrk 348, Mrk 607, and Mrk 1058 - obtained from observations with the Gemini Multi-Object Spectrograph Integral Field Unit on the Gemini North Telescope. The data cover the inner 3.5 arcsec × 5.0 arcsec - corresponding to physical scales in the range 0.6 × 0.9-1.5 × 2.2 kpc2 - at a spatial resolution ranging from 110 to 280 pc with a spectral coverage of 4300-7100 Å and velocity resolution of ≈90 km s-1. The gas excitation is Seyfert like everywhere but show excitation gradients that are correlated with the gas kinematics, reddening and/or the gas density. The gas kinematics show in all cases two components: a rotation one similar to that observed in the stellar velocity field, and an outflow component. In the case of Mrk607, the gas is counter-rotating relative to the stars. Enhanced gas velocity dispersion is observed in association with the outflows according to two patterns: at the locations of the highest outflow velocities along the ionization axis or perpendicularly to it in a strip centred at the nucleus that we attribute to an equatorial outflow. Bipolar outflows are observed in Mrk 348 and Mrk 79, while in Mrk 1058 only the blueshifted part is clearly observed, while in cases of Mrk 6 and Mrk 607, the geometry of the outflow needs further constraints from modelling to be presented in a forthcoming study, where the mass flow rate and powers will also be obtained.

  17. Effect of particle shape on thermal conductivity of Al2O3 nanofluids

    International Nuclear Information System (INIS)

    Kim, Hyun Jin; Lee, Seung Hyun; Kwon, Hey Lim; Jang, Seok Pil; Lim, Hyung Mi

    2009-01-01

    In this paper, thermal conductivities of water-based Al 2 O 3 nanofluids with brick, blade, platelet and rod type nanoparticle are measured by transient hot wire method to investigate the effect of nanoparticle shape on thermal conductivity. Water-based Al 2 O 3 nanofluids are prepared by two-step method and that of volume fraction is 3%. Temperature dependency of thermal conductivity of water-based Al 2 O 3 nanofluids is also studied by measuring of thermal conductivity from 22 .deg. C to 42 .deg. C. TEM micrograph, zeta potential and BET are measured to investigate suspension and disperse stability of water-based Al 2 O 3 nanofluids. Furthermore, Experimental results are compared with theoretical models such as Hamilton-Crosser model considering the shape effects on thermal conductivity.

  18. Growth mechanism of NaClO 3 and NaBrO 3 crystals from aqueous ...

    Indian Academy of Sciences (India)

    A study of growth rates of NaClO3 and NaBrO3 has been carried out using a small growth cell by in situ observation. Normal growth rates of {100} faces of NaClO3 and {111} faces of NaBrO3 along ⟨ 110 ⟩ direction are measured under relatively high supersaturation ranging from 3–8%. In the initial stages of growth, {100}, ...

  19. Unidirectional THz radiation propagation in BiFeO3

    Science.gov (United States)

    Room, Toomas

    The mutual coupling between magnetism and electricity present in many multiferroic materials permit the magnetic control of the electric polarization and the electric control of the magnetization. These static magnetoelectric (ME) effects are of enormous interest: The ability to write a magnetic state current-free by an electric voltage would provide a huge technological advantage. However, ME coupling changes the low energy electrodynamics of these materials in unprecedented way - optical ME effects give rise to unidirectional light propagation as recently observed in low-temperature multiferroics. The transparent direction can be switched with dc magnetic or electric field, thus opening up new possibilities to manipulate the propagation of electromagnetic waves in multiferroic materials. We studied the unidirectional transmission of THz radiation in BiFeO3 crystals, the unique multiferroic compound offering a real potential for room temperature applications. The electrodynamics of BiFeO3 at 1THz and below is dominated by the spin wave modes of cycloidal spin order. We found that the optical magnetoelectric effect generated by spin waves in BiFeO3 is robust enough to cause considerable nonreciprocal directional dichroism in the GHz-THz range even at room temperature. The supporting theory attributes the observed unidirectional transmission to the spin-current-driven dynamic ME effect. Our work demonstrates that the nonreciprocal directional dichroism spectra of low energy excitations and their theoretical analysis provide microscopic model of ME couplings in multiferroic materials. Recent THz spectroscopy studies of multiferroic materials are an important step toward the realization of optical diodes, devices which transmit light in one but not in the opposite direction.

  20. Synthesis and characterization of BaTiO3 ferroelectric material

    International Nuclear Information System (INIS)

    Osman, K.I.

    2011-01-01

    BaTiO 3 powder was prepared at low temperatures using the solid-state reaction, starting with two different precursors; the BaCO 3 /TiO 2 and the Ba(NO 3 ) 2 /TiO 2 powder mixtures. It was found that, a single phase BaTiO 3 was formed after calcination at 750 degree C for 10 h and at 600 degree C for 6 h for the first and second mixtures, respectively. Thermal and XRD analyses were used to study the formation kinetics of BaTiO 3 . Contracting volume reaction model was found to control both reactions. The SEM of the as milled powder, TMA, TG and thermodynamics analysis have been used to propose a realistic approach describing the reaction mechanism of BaTiO 3 . Characterization and the dielectric properties of the sintered BaTiO 3 were investigated. The relative permittivity and the dielectric loss measured at room temperature and at 1 khz were 2028.5 and 0.043 for BaTiO 3 prepared from BaCO 3 /TiO 2 , while they were 1805.33 and 0.41 for BaTiO 3 prepared from Ba(NO 3 ) 2 /TiO 2 .

  1. Fabrication of hierarchical porous ZnO-Al2O3 microspheres with enhanced adsorption performance

    Science.gov (United States)

    Lei, Chunsheng; Pi, Meng; Xu, Difa; Jiang, Chuanjia; Cheng, Bei

    2017-12-01

    Hierarchical porous ZnO-Al2O3 microspheres were fabricated through a simple hydrothermal route. The as-prepared hierarchical porous ZnO-Al2O3 composites were utilized as adsorbents to remove organic dye Congo red (CR) from water. The ZnO-Al2O3 composites had morphology of microspheres with diameters in the range of 12-16 μm, which were assembled by nanosheets with thicknesses of approximately 60 nm. The adsorption kinetics of CR onto the ZnO-Al2O3 composites was properly fitted by the pseudo-second-order kinetic model. The equilibrium adsorption data were perfectly described by the Langmuir isotherm and had a maximum adsorption capacity that reached 397 mg/g, which was significantly higher than the value of the pure alumina (Al2O3) and zinc oxide (ZnO) samples. The superior CR removal efficiency of the ZnO-Al2O3 composites was attributed to its well-developed hierarchical porous structures and larger specific surface area (201 m2/g), which were conducive to the diffusion and adsorption of CR molecules. Moreover, the regeneration study reveals that the ZnO-Al2O3 composites have suitable stability and reusability. The results also indicate that the as-prepared sample can act as a highly effective adsorbent in anionic dye removal from wastewater.

  2. Elevated tropospheric CO2 and O3 concentrations impair organic pollutant removal from grassland soil.

    Science.gov (United States)

    Ai, Fuxun; Eisenhauer, Nico; Jousset, Alexandre; Butenschoen, Olaf; Ji, Rong; Guo, Hongyan

    2018-04-03

    The concentrations of tropospheric CO 2 and O 3 have been rising due to human activities. These rising concentrations may have strong impacts on soil functions as changes in plant physiology may lead to altered plant-soil interactions. Here, the effects of eCO 2 and eO 3 on the removal of polycyclic aromatic hydrocarbon (PAH) pollutants in grassland soil were studied. Both elevated CO 2 and O 3 concentrations decreased PAH removal with lowest removal rates at elevated CO 2 and elevated O 3 concentrations. This effect was linked to a shift in soil microbial community structure by structural equation modeling. Elevated CO 2 and O 3 concentrations reduced the abundance of gram-positive bacteria, which were tightly linked to soil enzyme production and PAH degradation. Although plant diversity did not buffer CO 2 and O 3 effects, certain soil microbial communities and functions were affected by plant communities, indicating the potential for longer-term phytoremediation approaches. Results of this study show that elevated CO 2 and O 3 concentrations may compromise the ability of soils to degrade organic pollutants. On the other hand, the present study also indicates that the targeted assembly of plant communities may be a promising tool to shape soil microbial communities for the degradation of organic pollutants in a changing world.

  3. Synthesis of Phase Pure Hexagonal YFeO3 Perovskite as Efficient Visible Light Active Photocatalyst

    Directory of Open Access Journals (Sweden)

    Mohammed Ismael

    2017-11-01

    Full Text Available Hexagonal perovskite YFeO3 was synthesized by a complex-assisted sol-gel technique allowing crystallization at calcination temperatures below 700 °C. As determined by diffuse reflectance spectroscopy (DRS and Tauc plots, the hexagonal YFeO3 exhibits a lower optical band gap (1.81 eV than the orthorhombic structure (about 2.1 eV or even higher being typically obtained at elevated temperatures (>700 °C, and thus enables higher visible light photocatalysis activity. Structure and morphology of the synthesized YFeO3 perovskites were analyzed by powder X-ray diffraction (XRD and nitrogen adsorption, proving that significantly smaller crystallite sizes and higher surface areas are obtained for YFeO3 with a hexagonal phase. The photocatalytic activity of the different YFeO3 phases was deduced via the degradation of the model pollutants methyl orange and 4-chlorophenol. Experiments under illumination with light of different wavelengths, in the presence of different trapping elements, as well as photoelectrochemical tests allow conclusions regarding band positions of YFeO3 and the photocatalytic degradation mechanism. X-ray photoelectron spectroscopy indicates that a very thin layer of Y2O3 might support the photocatalysis by improving the separation of photogenerated charge carriers.

  4. Nonstoichiometry of Epitaxial FeTiO(3+delta) Films

    Science.gov (United States)

    2003-01-01

    nonstoichiometry of the FeTiO3 +8 films was probably produced by cation vacancies and disarrangement of Fe3+ and Ti4 ions, which randomly occupied both interstitial...and substitutional sites of the FeTiO 3 related structure. INTRODUCTION Solid solutions of ot-Fe20 3- FeTiO3 (hematite-ilmenite) series are known to...tried to confirm preparation conditions of stoichiometric FeTiO 3 films. According to a literature on bulk crystal growth of FeTiO3 [5], very low oxygen

  5. Anti-bombing insensitivity life of molybdenum cathode doped with La2O3 and Y2O3

    International Nuclear Information System (INIS)

    Wang Jinshu; Wang Yiman; Zhou Meiling

    2006-01-01

    Anti-bombing insensitivity of La 2 O 3 -Y 2 O 3 -Mo secondary emitter has been studied in this paper. The variation of maximum secondary emission coefficient δ max with time was measured. The cathode after life experiment was analyzed by means of HRM, SEM, EDS and XRD. The results showed that δ max of La 2 O 3 -Y 2 O 3 -Mo cathode operating at 1100 deg. C under continuous electron bombardment of 300 W/cm 2 was still about 2.5 after 1000 h operation, indicating that this kind of cathode had good anti-bombing insensitivity. In the internal part of the cathode, RE 2 O 3 (rare earth oxide) and molybdenum grains distributed alternately and there existed a certain relationship between crystallographic orientation of RE 2 O 3 and that of molybdenum. It was found that a RE 2 O 3 layer was formed on the surface after operation. The high δ max of La 2 O 3 -Y 2 O 3 -Mo cathode was related to the RE 2 O 3 layer on the surface and the amount of nanosized La 2 O 3 particles on the Y 2 O 3 layer

  6. Positron annihilation studies on the behaviour of vacancies in LaAlO3/SrTiO3 heterostructures

    Science.gov (United States)

    Yuan, Guoliang; Li, Chen; Yin, Jiang; Liu, Zhiguo; Wu, Di; Uedono, Akira

    2012-11-01

    The formation and diffusion of vacancies are studied in LaAlO3/SrTiO3 heterostructures. Oxygen vacancies (VOS) appear easily in the SrTiO3 substrate during LaAlO3 film growth at 700 °C and 10-4 Pa oxygen pressure rather than at 10-3-10-1 Pa, thus the latter two-dimensional electron gas should come from the polarity discontinuity at the (LaO)+/(TiO2)0 interface. For SrTiO3-δ/LaAlO3/SrTiO3, high-density VOS of the SrTiO3-δ film can pass through the LaAlO3 film and then diffuse to 1.7 µm depth in the SrTiO3 substrate, suggesting that LaAlO3 has VOS at its middle-deep energy levels within the band gap. Moreover, high-density VOS may combine with a strontium/titanium vacancy (VSr/Ti) to form VSr/Ti-O complexes in the SrTiO3 substrate at 700 °C.

  7. Effect of Ga2O3 addition on the properties of Y2O3-doped AlN ceramics

    Directory of Open Access Journals (Sweden)

    Shin H.

    2015-01-01

    Full Text Available Effect Ga2O3 addition on the densification and properties of Y2O3-doped AlN ceramics was investigated under the constraint of total sintering additives (Y2O3 and Ga2O3 of 4.5 wt%. Ga was detected in the AlN grain as well as the grain boundary phases. YAlO3 and Y4Al2O9 were observed as the secondary crystalline phases in all of the investigated compositions. As the substitution of Ga2O3 for Y2O3 increased, the quantity of the Y4Al2O9 phase decreased while that of YAlO3 was more or less similar. Neither additional secondary phases was identified, nor was the sinterability inhibited by the Ga2O3 addition; the linear shrinkage and apparent density were above 20 percent and 3.34-3.37 g/cm3, respectively. However, the optical reflectance and the elastic modulus generally decreased whereas the Poisson ratio increased significantly. The dielectric constant and the loss tangent of 4.0Y2O3-0.5Ga2O3-95.5Y2O3 at the resonant frequency of 8.22 GHz were 8.63 and 0.003, respectively.

  8. DIRECT IMAGING OF A COMPACT MOLECULAR OUTFLOW FROM A VERY LOW LUMINOSITY OBJECT: L1521F-IRS

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Satoko [Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago (Chile); Ohashi, Nagayoshi [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China); Bourke, Tyler L., E-mail: satoko.takahashi@nao.ac.jp [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2013-09-01

    Studying the physical conditions of very low luminosity objects (VeLLOs; L{sub bol} < 0.1 L{sub Sun }) is important for understanding the earliest evolutionary stage of protostars and brown dwarfs. We report interferometric observations of the VeLLO L1521F-IRS, in {sup 12}CO (2-1) line emission and the 1.3 mm continuum emission, using the Submillimeter Array. With the {sup 12}CO (2-1) high-resolution observations, we have spatially resolved a compact but poorly collimated molecular outflow associated with L1521F-IRS for the first time. The blueshifted and redshifted lobes are aligned along the east and west side of L1521F-IRS with a lobe size of Almost-Equal-To 1000 AU. The estimated outflow mass, maximum outflow velocity, and outflow force are (9.0-80) Multiplication-Sign 10{sup -4} M{sub Sun }, 7.2 km s{sup -1}, and (7.4-66) Multiplication-Sign 10{sup -7} M{sub Sun} km s{sup -1} yr{sup -1}, respectively. The estimated outflow parameters such as size, mass, and momentum rate are similar to values derived for other VeLLOs, and are located at the lower end of values compared to previously studied outflows associated with low- to high-mass star-forming regions. Low-velocity less collimated (1.5 km s{sup -1}/1200 AU) and higher-velocity compact (4.0 km s{sup -1}/920 AU) outflow components are suggested by the data. These velocity structures are not consistent with those expected in the jet-driven or wind-driven outflow models, perhaps suggesting a remnant outflow from the first hydrostatic core as well as an undeveloped outflow from the protostar. Detection of an infrared source and compact millimeter continuum emission suggests the presence of the protostar, while its low bolometric luminosity (0.034-0.07 L{sub Sun }) and small outflow suggests that L1521F is in the earliest protostellar stage (<10{sup 4} yr) and contains a substellar mass object. The bolometric (or internal) luminosity of L1521F-IRS suggests that the current mass accretion rate is an order of

  9. Multiferroic properties of BiFeO3/BaTiO3 multilayered thin films

    International Nuclear Information System (INIS)

    Sharma, Savita; Tomar, Monika; Kumar, Ashok; Puri, Nitin K.; Gupta, Vinay

    2014-01-01

    Multilayered structures of multiferroic BiFeO 3 (BFO) and ferroelectric BaTiO 3 (BTO) have been fabricated using pulsed laser deposition (PLD). Ferromagnetic and ferroelectric properties of the multilayered system (BFO/BTO) have been investigated. It could be inferred that the magnetization increases with the incorporation of BTO buffer layer, which indicates a coupling between the ferroelectric and ferromagnetic orders. Vibrating sample magnetometer (VSM) measurements performed on the prepared multiferroic samples show that the magnetization is significantly increased (M s =56.88 emu/cm 3 ) for the multilayer system with more number of layers (four) keeping the total thickness of the multilayered system constant (350 nm) meanwhile maintaining the sufficiently enhanced ferroelectric properties (P r =29.68 µC/cm 2 )

  10. Growing LaAlO3/SrTiO3 interfaces by sputter deposition

    Directory of Open Access Journals (Sweden)

    I. M. Dildar

    2015-06-01

    Full Text Available Sputter deposition of oxide materials in a high-pressure oxygen atmosphere is a well-known technique to produce thin films of perovskite oxides in particular. Also interfaces can be fabricated, which we demonstrated recently by growing LaAlO3 on SrTiO3 substrates and showing that the interface showed the same high degree of epitaxy and atomic order as is made by pulsed laser deposition. However, the high pressure sputtering of oxides is not trivial and number of parameters are needed to be optimized for epitaxial growth. Here we elaborate on the earlier work to show that only a relatively small parameter window exists with respect to oxygen pressure, growth temperature, radiofrequency power supply and target to substrate distance. In particular the sensitivity to oxygen pressure makes it more difficult to vary the oxygen stoichiometry at the interface, yielding it insulating rather than conducting.

  11. Electric Properties of Pb(Sb1/2Nb1/2)O3 PbTiO3 PbZrO3 Ceramics

    Science.gov (United States)

    Kawamura, Yasushi; Ohuchi, Hiromu

    1994-09-01

    Solid-solution ceramics of ternary system xPb(Sb1/2Nb1/2)O3 yPbTiO3 zPbZrO3 were prepared by the solid-state reaction of powder materials. Ceramic, electric, dielectric and piezoelectric properties and crystal structures of the system were studied. Sintering of the system xPb(Sb1/2Nb1/2)O3 yPbTiO3 zPbZrO3 is much easier than that of each end composition, and well-sintered high-density ceramics were obtained for the compositions near the morphotropic transformation. Piezoelectric ceramics with high relative dielectric constants, high radial coupling coefficient and low resonant resistance were obtained for the composition near the morphotropic transformation. The composition Pb(Sb1/2Nb1/2)0.075Ti0.45Zr0.475O3 showed the highest dielectric constant (ɛr=1690), and the composition Pb(Sb1/2Nb1/2)0.05Ti0.45Zr0.5O3 showed the highest radial coupling coefficient (kp=64%).

  12. Enhanced ion acoustic fluctuations and ion outflows

    Directory of Open Access Journals (Sweden)

    F. R. E. Forme

    1999-02-01

    Full Text Available A number of observations showing enhanced ion acoustic echoes observed by means of incoherent scatter radars have been reported in the literature. The received power is extremely enhanced by up to 1 or 2 orders of magnitude above usual values, and it is mostly contained in one of the two ion acoustic lines. This spectral asymmetry and the intensity of the received signal cannot be resolved by the standard analysis procedure and often causes its failure. As a result, and in spite of a very clear spectral signature, the analysis is unable to fit the plasma parameters inside the regions of ion acoustic turbulence. We present European Incoherent Scatter radar (EISCAT observations of large ion outflows associated with the simultaneous occurrence of enhanced ion acoustic echoes. The ion fluxes can reach 1014 m-2 s-1 at 800 km altitude. From the very clear spectral signatures of these echoes, a method is presented to extract estimates of the electron temperature and the ion drift within the turbulent regions. It is shown that the electron gas is strongly heated up to 11 000 K. Also electron temperature gradients of about 0.02 K/m exist. Finally, the estimates of the electron temperature and of the ion drift are used to study the possible implications for the plasma transport inside turbulent regions. It is shown that strong electron temperature gradients cause enhancement of the ambipolar electric field and can account for the observed ion outflows.Key words. Ionosphere (auroral ionosphere; ionosphere · magnetosphere interactions; plasma waves and instabilities.

  13. Circumstellar Disks and Outflows in Turbulent Molecular Cloud Cores: Possible Formation Mechanism for Misaligned Systems

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, Tomoaki [Faculty of Sustainability Studies, Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160 (Japan); Machida, Masahiro N. [Department of Earth and Planetary Sciences, Kyushu University, Fukuoka 812-8581 (Japan); Inutsuka, Shu-ichiro, E-mail: matsu@hosei.ac.jp [Department of Physics, Nagoya University, Chikusa-ku, Nagoya 464-8602 (Japan)

    2017-04-10

    We investigate the formation of circumstellar disks and outflows subsequent to the collapse of molecular cloud cores with the magnetic field and turbulence. Numerical simulations are performed by using an adaptive mesh refinement to follow the evolution up to ∼1000 years after the formation of a protostar. In the simulations, circumstellar disks are formed around the protostars; those in magnetized models are considerably smaller than those in nonmagnetized models, but their size increases with time. The models with stronger magnetic fields tend to produce smaller disks. During evolution in the magnetized models, the mass ratios of a disk to a protostar is approximately constant at ∼1%–10%. The circumstellar disks are aligned according to their angular momentum, and the outflows accelerate along the magnetic field on the 10–100 au scale; this produces a disk that is misaligned with the outflow. The outflows are classified into two types: a magnetocentrifugal wind and a spiral flow. In the latter, because of the geometry, the axis of rotation is misaligned with the magnetic field. The magnetic field has an internal structure in the cloud cores, which also causes misalignment between the outflows and the magnetic field on the scale of the cloud core. The distribution of the angular momentum vectors in a core also has a non-monotonic internal structure. This should create a time-dependent accretion of angular momenta onto the circumstellar disk. Therefore, the circumstellar disks are expected to change their orientation as well as their sizes in the long-term evolutions.

  14. What's in the Wind? Determining the Properties of Outflowing Gas in Powerful Broad Absorption Line Quasars

    Science.gov (United States)

    Leighly, Karen

    2017-08-01

    A significant fraction of quasars exhibits blueshifted broadabsorption lines (BALs) in their rest-UV spectra, indicating powerfuloutflows emerging from the central engine. These outflows may removeangular momentum to enable black hole growth, enrich the intergalacticmedium with metals, and trigger quenching of star formation ingalaxies. Despite years of study, the physical conditions of theoutflowing gas are poorly understood. The handful of objects that havebeen subjected to detailed analysis are atypical and characterized byrelatively narrow lines where blending is unimportant. However,investigating more powerful BAL quasars will give us better insightinto the types of outflows much more likely to impact galaxyevolution.SimBAL is a novel spectral synthesis fitting method for BAL quasarsthat uses Bayesian model calibration to compare synthetic to observedspectra. With the model inputs of ionization parameter, columndensity, and covering fraction specified, the gas properties givingrise to the BAL features can be determined. We propose to applySimBAL to archival spectra of a sample of 14 luminous BAL quasars to characterize their bulk outflow properties as a function of velocityfor the first time. Our results will show the range of parameterstypical of powerful outflows, an essential step towards constrainingthe physics behind quasar winds and thus their impact on theirenvironments.

  15. A Massive X-ray Outflow From The Quasar PDS 456

    Science.gov (United States)

    Reeves, J. N.; O'Brien, P. T.; Ward, M. J.

    2003-01-01

    We report on XMM-Newton spectroscopic observations of the luminous, radio-quiet quasar PDS 456. The hard X-ray spectrum of PDS 456 shows a deep absorption trough (constituting 50% of the continuum) at energies above 7 keV in the quasar rest frame, which can be attributed to a series of blue-shifted K-shell absorption edges due to highly ionized iron. The higher resolution soft X-ray grating RGS spectrum exhibits a broad absorption line feature near 1 keV, which can be modeled by a blend of L-shell transitions from highly ionized iron (Fe XVII - XXIV). An extreme outflow velocity of approx. 50000 km/s is required to model the K and L shell iron absorption present in the XMM-Newton data. Overall, a large column density (N(sub H) = 5 x 10(exp 23)/sq cm) of highly ionized gas (log xi = 2.5) is required in PDS 456. A large mass outflow rate of approx. 10 solar mass/year (assuming a conservative outflow covering factor of 0.1 steradian) is derived, which is of the same order as the overall mass accretion rate in PDS 456. This represents a substantial fraction (approx. 10%) of the quasar energy budget, whilst the large column and outflow velocity place PDS 456 towards the extreme end of the broad absorption line quasar population.

  16. Analysis of Al2O3 Nanostructure Using Scanning Microscopy

    Directory of Open Access Journals (Sweden)

    Marek Kubica

    2018-01-01

    Full Text Available It has been reported that the size and shape of the pores depend on the structure of the base metal, the type of electrolyte, and the conditions of the anodizing process. The paper presents thin Al2O3 oxide layer formed under hard anodizing conditions on a plate made of EN AW-5251 aluminum alloy. The oxidation of the ceramic layer was carried out for 40–80 minutes in a three-component SAS electrolyte (aqueous solution of acids: sulphuric 33 ml/l, adipic 67 g/l, and oxalic 30 g/l at a temperature of 293–313 K, and the current density was 200–400 A/m2. Presented images were taken by a scanning microscope. A computer analysis of the binary images of layers showed different shapes of pores. The structure of ceramic Al2O3 layers is one of the main factors determining mechanical properties. The resistance to wear of specimen-oxide coating layer depends on porosity, morphology, and roughness of the ceramic layer surface. A 3D oxide coating model, based on the computer analysis of images from a scanning electron microscope (Philips XL 30 ESEM/EDAX, was proposed.

  17. Analysis of Al2O3 Nanostructure Using Scanning Microscopy

    Science.gov (United States)

    Kubica, Marek; Bara, Marek

    2018-01-01

    It has been reported that the size and shape of the pores depend on the structure of the base metal, the type of electrolyte, and the conditions of the anodizing process. The paper presents thin Al2O3 oxide layer formed under hard anodizing conditions on a plate made of EN AW-5251 aluminum alloy. The oxidation of the ceramic layer was carried out for 40–80 minutes in a three-component SAS electrolyte (aqueous solution of acids: sulphuric 33 ml/l, adipic 67 g/l, and oxalic 30 g/l) at a temperature of 293–313 K, and the current density was 200–400 A/m2. Presented images were taken by a scanning microscope. A computer analysis of the binary images of layers showed different shapes of pores. The structure of ceramic Al2O3 layers is one of the main factors determining mechanical properties. The resistance to wear of specimen-oxide coating layer depends on porosity, morphology, and roughness of the ceramic layer surface. A 3D oxide coating model, based on the computer analysis of images from a scanning electron microscope (Philips XL 30 ESEM/EDAX), was proposed. PMID:29861823

  18. Defect phase diagram for doping of Ga2O3

    Science.gov (United States)

    Lany, Stephan

    2018-04-01

    For the case of n-type doping of β-Ga2O3 by group 14 dopants (C, Si, Ge, Sn), a defect phase diagram is constructed from defect equilibria calculated over a range of temperatures (T), O partial pressures (pO2), and dopant concentrations. The underlying defect levels and formation energies are determined from first-principles supercell calculations with GW bandgap corrections. Only Si is found to be a truly shallow donor, C is a deep DX-like (lattice relaxed donor) center, and Ge and Sn have defect levels close to the conduction band minimum. The thermodynamic modeling includes the effect of association of dopant-defect pairs and complexes, which causes the net doping to decline when exceeding a certain optimal dopant concentration. The optimal doping levels are surprisingly low, between about 0.01% and 1% of cation substitution, depending on the (T, pO2) conditions. Considering further the stability constraints due to sublimation of molecular Ga2O, specific predictions of optimized pO2 and Si dopant concentrations are given. The incomplete passivation of dopant-defect complexes in β-Ga2O3 suggests a design rule for metastable doping above the solubility limit.

  19. Defect phase diagram for doping of Ga2O3

    Directory of Open Access Journals (Sweden)

    Stephan Lany

    2018-04-01

    Full Text Available For the case of n-type doping of β-Ga2O3 by group 14 dopants (C, Si, Ge, Sn, a defect phase diagram is constructed from defect equilibria calculated over a range of temperatures (T, O partial pressures (pO2, and dopant concentrations. The underlying defect levels and formation energies are determined from first-principles supercell calculations with GW bandgap corrections. Only Si is found to be a truly shallow donor, C is a deep DX-like (lattice relaxed donor center, and Ge and Sn have defect levels close to the conduction band minimum. The thermodynamic modeling includes the effect of association of dopant-defect pairs and complexes, which causes the net doping to decline when exceeding a certain optimal dopant concentration. The optimal doping levels are surprisingly low, between about 0.01% and 1% of cation substitution, depending on the (T, pO2 conditions. Considering further the stability constraints due to sublimation of molecular Ga2O, specific predictions of optimized pO2 and Si dopant concentrations are given. The incomplete passivation of dopant-defect complexes in β-Ga2O3 suggests a design rule for metastable doping above the solubility limit.

  20. The new magnetic structure of LaMnO3

    International Nuclear Information System (INIS)

    Gontchar, L.E.; Nikiforov, A.E.

    1999-01-01

    Complete text of publication follows. The LaMnO 3 is known to be a parent compound for materials having colossal magnetoresistance. The magnetic and structural properties of LaMnO 3 are of the great interest now. In the present work, the new four-sublattices magnetic structure - (A x , F y , G z ) + (G x , C y , A z ) - is proposed. The Spin-Hamiltonian used in this model is based on calculated crystal structure and includes isotropic exchange interaction, the single-ion anisotropy and the antisymmetric exchange and Zeeman interactions. All of these components depend upon JT distortion. The spin-wave approximation is used and the dispersion dependencies of the spin waves are calculated. Our previous consideration of KCuF 3 shows that spin-wave method is not sensitive to small antisymmetric exchange interaction and inequivalency of the g tensors, but these small effects could not be neglected in calculations of magnetic structure. The dependence of antiferromagnetic resonance field upon angle is predicted. It could clarify the real magnetic structure. In spite of the sufficient energy gap in the Γ-point of magnetic Brillouin zone (ΔE = 2.7 meV) the measurements of this dependence could be carried out. (author)

  1. Ion-irradiation-induced phase transformation in rare earth sesquioxides (Dy2O3,Er2O3,Lu2O3)

    International Nuclear Information System (INIS)

    Tang, M.; Lu, P.; Valdez, J.A.; Sickafus, K.E.

    2006-01-01

    Polycrystalline pellets of cubic C-type rare earth structure (Ia3) Dy 2 O 3 , Er 2 O 3 , and Lu 2 O 3 were irradiated at cryogenic temperature (120 K) with 300 keV Kr ++ ions to a maximum fluence of 1x10 20 Kr/m 2 . Irradiated specimens were examined using grazing incidence x-ray diffraction and transmission electron microscopy. Ion irradiation leads to different radiation effects in these three materials. First, Dy 2 O 3 begins to transform to a monoclinic B-type rare earth structure (C2/m) at a peak dose of ∼5 displacements per atom (dpa) (corresponding to a fluence of 2x10 19 Kr/m 2 ). This transformation is nearly complete at a peak dose of 25 dpa (a fluence of 1x10 20 Kr/m 2 ). Er 2 O 3 also transforms to the B-type structure, but the transformation starts at a higher irradiation dose of about 15-20 dpa [a fluence of about (6-8)x10 19 Kr/m 2 ]. Lu 2 O 3 was found to maintain the C-type structure even at the highest irradiation dose of 25 dpa (a fluence of 1x10 20 Kr/m 2 ). No C-to-B transformation was observed in Lu 2 O 3 . The irradiation dose dependence of the C-to-B phase transformation observed in Dy 2 O 3 , Er 2 O 3 , and Lu 2 O 3 is closely related to the temperature dependence of the C-to-B phase transformation found in phase diagrams for these three materials

  2. Outflows from black hole hyperaccretion systems: short and long-short gamma-ray bursts and `quasi-supernovae'

    Science.gov (United States)

    Song, Cui-Ying; Liu, Tong; Li, Ang

    2018-06-01

    The detections of some long gamma-ray bursts (LGRBs) relevant to mergers of neutron star (NS)-NS or black hole (BH)-NS, as well as some short gamma-ray bursts (SGRBs) probably produced by collapsars, muddle the boundary of two categories of gamma-ray bursts (GRBs). In both cases, a plausible candidate of central engine is a BH surrounded by a hyperaccretion disc with strong outflows, launching relativistic jets driven by Blandford-Znajek mechanism. In the framework of compact binary mergers, we test the applicability of the BH hyperaccretion inflow-outflow model on powering observed GRBs. We find that, for a low outflow ratio, ˜ 50 per cent, post-merger hyperaccretion processes could power not only all SGRBs but also most of LGRBs. Some LGRBs might originate from merger events in the BH hyperaccretion scenario, at least on the energy requirement. Moreover, kilonovae might be produced by neutron-rich outflows, and their luminosities and time-scales significantly depend on the outflow strengths. GRBs and their associated kilonovae are competitive with each other on the disc mass and total energy budgets. The stronger the outflow, the more similar the characteristics of kilonovae to supernovae (SNe). This kind of `nova' might be called `quasi-SN'.

  3. Structural, magnetic and electrical properties of the hexagonal ferrites MFeO3 (M=Y, Yb, In)

    International Nuclear Information System (INIS)

    Downie, Lewis J.; Goff, Richard J.; Kockelmann, Winfried; Forder, Sue D.; Parker, Julia E.; Morrison, Finlay D.; Lightfoot, Philip

    2012-01-01

    The hexagonal ferrites MFeO 3 (M=Y, Yb, In) have been studied using a combination of neutron and X-ray powder diffraction, magnetic susceptibility, dielectric measurements and 57 Fe Mössbauer spectroscopy. This study confirms the previously reported crystal structure of InFeO 3 (YAlO 3 structure type, space group P6 3 /mmc), but YFeO 3 and YbFeO 3 both show a lowering of symmetry to at most P6 3 cm (ferrielectric YMnO 3 structure type). However, Mössbauer spectroscopy shows at least two distinct Fe sites for both YFeO 3 and YbFeO 3 and we suggest that the best model to rationalise this involves phase separation into more than one similar hexagonal YMnO 3 -like phase. Rietveld analysis of the neutron diffraction data was carried out using two hexagonal phases as a simplest case scenario. In both YFeO 3 and YbFeO 3 , distinct dielectric anomalies are observed near 130 K and 150 K, respectively. These are tentatively correlated with weak anomalies in magnetic susceptibility and lattice parameters, for YFeO 3 and YbFeO 3 , respectively, which may suggest a weak magnetoelectric effect. Comparison of neutron and X-ray powder diffraction shows evidence of long-range magnetic order in both YFeO 3 and YbFeO 3 at low temperatures. Due to poor sample crystallinity, the compositional and structural effects underlying the phase separation and possible magnetoelectric phenomena cannot be ascertained. - Graphical abstract: Hexagonal MFeO 3 (M=Y, Yb) exhibit phase separation into two YMnO 3 -like phases. Variable temperature crystallographic, electrical and magnetic studies suggest weak correlations between electrical and magnetic responses and long-range magnetic order at low temperature. Highlights: ► Multi-technique study of multiferroic hexagonal MFeO 3 . ► Phase separation into two similar hexagonal phases. ► Weak coupling of electrical and magnetic responses. ► Long-range magnetic order at low T.

  4. Trends in (LaMnO3)n/(SrTiO3)m superlattices with varying layer thicknesses

    KAUST Repository

    Jilili, J.

    2015-09-01

    We investigate the thickness dependence of the structural, electronic, and magnetic properties of (LaMnO3)n/(SrTiO3)m (n, m = 2, 4, 6, 8) superlattices using density functional theory. The electronic structure turns out to be highly sensitive to the onsite Coulomb interaction. In contrast to bulk SrTiO3, strongly distorted O octahedra are observed in the SrTiO3 layers with a systematic off centering of the Ti atoms. The systems favour ferromagnetic spin ordering rather than the antiferromagnetic spin ordering of bulk LaMnO3 and all show half-metallicity, while a systematic reduction of the minority spin band gaps as a function of the LaMnO3 and SrTiO3 layer thicknesses originates from modifications of the Ti dxy states.

  5. Synergistic toxic effect of nano-Al2O3 and As(V) on Ceriodaphnia dubia

    International Nuclear Information System (INIS)

    Wang Demin; Hu Ji; Forthaus, Brett E.; Wang Jianmin

    2011-01-01

    Engineered nanomaterials (ENMs) alone could negatively impact the environment and human health. However, their role in the presence of other toxic substances is not well understood. The toxicity of nano-Al 2 O 3 , inorganic As(V), and a combination of both was examined with C. dubia as the model organisms. Bare nano-Al 2 O 3 particles exhibited partial mortality at concentrations of greater than 200 mg/L. When As(V) was also present, a significant amount of As(V) was accumulated on the nano-Al 2 O 3 surface, and the calculated LC 50 of As(V) in the presence of nano-Al 2 O 3 was lower than that it was without the nano-Al 2 O 3 . The adsorption of As(V) on the nano-Al 2 O 3 surface and the uptake of nano-Al 2 O 3 by C. dubia were both verified. Therefore, the uptake of As(V)-loaded nano-Al 2 O 3 was a major reason for the enhanced toxic effect. - Highlights: → Nano-Al 2 O 3 particles alone do not have significant toxic effect on C. dubia. → However, nano-Al 2 O 3 particles significantly enhance the toxicity of As(V). → The uptake of As-loaded nano-Al 2 O 3 by C. dubia plays the major role on the toxicity. - Nano-Al 2 O 3 could accumulate background As(V) and enhance As(V) toxicity on C. dubia through the uptake of As(V)-loaded nano-Al 2 O 3 particles.

  6. Thermal behaviour of GdCo1-xMnxO3 cobaltates

    Science.gov (United States)

    Thakur, Rasna; Thakur, Rajesh K.; Gaur, N. K.

    2018-05-01

    With the objective of exploring the unknown thermodynamic behavior of GdCo1-xMnxO3 family, we present here an investigation of the temperature-dependent (10K≤T≤1000K) thermodynamic properties of GdCo1-xMnxO3 (x=0.1 to 0.8). The specific heat of GdCoO3 with Mn doping in the perovskite structure at B-site has been studied by means of a Modified Rigid Ion Model (MRIM). The cohesive energy, specific heat (C), volume thermal expansion (α) and Gruneisen parameter (γ) of GdCo1-xMnxO3 compounds are also discussed.

  7. Structure of glasses of the TeO2-MoO3 system

    International Nuclear Information System (INIS)

    Dimitriev, Y.; Dimitrov, V.; Bart, J.C.J.

    1981-01-01

    Structural models for glasses of the TeO 2 -MoO 3 system are suggested. On the basis of X-ray and infrared spectral investigations, by comparing with known crystalline structures of TeO 2 , MoO 3 and Te 2 MoO 7 9t 2 M, it is shown that the glasses from TeO 2 to Te 2 MoO 7 possess [TeO 4 ] and [MoO 5 ] groups as basic structural units. The latter are connected to form [Mo 2 O 8 ] complexes. The glasses in the MoO 3 -rich compositional range are built up of [TeO 3 ] and [MoO 6 ] polyhedra. The glass-formation tendency is discussed in relation to the role of the free electron pair and the disruption of secondary and weak primary bonds in the crystals. (author)

  8. Near-ground ozone source attributions and outflow in central eastern China during MTX2006

    Science.gov (United States)

    Li, J.; Wang, Z.; Akimoto, H.; Yamaji, K.; Takigawa, M.; Pochanart, P.; Liu, Y.; Tanimoto, H.; Kanaya, Y.

    2008-12-01

    A 3-D regional chemical transport model, the Nested Air Quality Prediction Model System (NAQPMS), with an on-line tracer tagging module was used to study the source of the near-ground (pollutants, and it captured highly polluted and clean cases well. The simulated near-ground ozone level over CEC was 60-85 ppbv (parts per billion by volume), which was higher than values in Japan and over the North Pacific (20-50 ppbv). The simulated tagged tracer data indicated that the regional-scale transport of chemically produced ozone over other areas in CEC contributed to the greatest fraction (49%) of the near-ground mean ozone at Mt. Tai in June; in situ photochemistry contributed only 12%. Due to high anthropogenic and biomass burning emissions that occurred in the southern part of the CEC, the contribution to ground ozone levels from this area played the most important role (32.4 ppbv, 37.9% of total ozone) in the monthly mean ozone concentration at Mt. Tai; values reached 59 ppbv (62%) on 6-7 June 2006. The monthly mean horizontal distribution of chemically produced ozone from various ozone production regions indicated that photochemical reactions controlled the spatial distribution of O3 over CEC. The regional-scale transport of pollutants also played an important role in the spatial and temporal distribution of ozone over CEC. Chemically produced ozone from the southern part of the study region can be transported northeastwardly to the northern rim of CEC; the mean contribution was 5-10 ppbv, and it reached 25 ppbv during high ozone events. Studies of the outflow of CEC ozone and its precursors, as well as their influences and contributions to the ozone level over adjacent regions/countries, revealed that the contribution of CEC ozone to mean ozone mixing ratios over the Korean Peninsula and Japan was 5-15 ppbv, of which about half was due to the direct transport of ozone from CEC and half was produced locally by ozone precursors transported from CEC.

  9. FEATURES OF OUTFLOW OF INTRAOCULAR LIQUID AFTER AN EKSIMERLAZER SKLEREKTOMY (PILOT STUDY

    Directory of Open Access Journals (Sweden)

    E. A. Korchuganova

    2017-01-01

    Full Text Available Modern approaches to surgical glaucoma treatment is based on the safe and effective methods. In recent years, great attention is paid to the techniques of stimulating uveoscleral path outtake aqueous humor from the eye. Uveoscleral space in the extended outflow pathways is dominant and constitutes about 72%. Sclera is a field of the greatest interest, as the end stages of the outflow of aqueous humor via the uveoscleral path. The aim of the study was to investigate the influence of excimer laser sclerectomy on the drainage function of the eye and development of a mathematical model based on the permeability of the sclera of the amount of laser ablation at a defined area of laser exposure and the level of IOP. Studies were conducted on 12 human cadaver eyes isolated person. The domestic excimer laser “MicroScan Vizum” with a wavelength of 193нм (0,193 µm was used for the thinning of sclera. In the experiment used a special computer program provided ablation of scleral tissue, the scleral bed forming a rectangular shape with a size 7,0x5,0 mm. the Depth of influence started from 100 microns to 600 microns in increments of 50 µn. The exposure was carried out at a constant perfusion pressure of 25 mm Hg After each impact was measured of the coefficient ease the outflow. A correlation was established between the factor and effective features, i.e., between the excimer laser deep sclerectomy (µm and ratio of lightness outflow (mm3/min/mm Hg.St. Thinning of the sclera leads to an improvement of its permeability and increasing the coefficient ease the outflow. A mathematical model, allowing to achieve the desired ratio of lightness outflow experiment by excimer laser sclerectomy was developed. The mathematical model has the form of the regression equation.The sclera is a promising object for further developments in the surgical treatment of glaucoma. Laser ablation of the sclera leads to an improvement of outflow via the uveoscleral path and

  10. Synthesis of MgO nanoparticle loaded mesoporous Al2O3 and its defluoridation study

    International Nuclear Information System (INIS)

    Dayananda, Desagani; Sarva, Venkateswara R.; Prasad, Sivankutty V.; Arunachalam, Jayaraman; Parameswaran, Padmanabhan; Ghosh, Narendra N.

    2015-01-01

    Highlights: • Simple and cost effective preparation of MgO nanoparticles loaded mesoporous Al 2 O 3 . • Adsorbents possess high surface area and mesoporous structure. • Higher fluoride removal capacity of MgO loaded Al 2 O 3 than that of pure Al 2 O 3 . • Faster fluoride adsorption kinetics of MgO loaded Al 2 O 3 from water. - Abstract: MgO nanoparticle loaded mesoporous alumina has been synthesized using a simple aqueous solution based cost effective method for removal of fluoride from water. Wide angle powder X-ray diffraction, nitrogen adsorption desorption analysis, transmission electron microscopy techniques and energy dispersive X-ray spectroscopy were used to characterize the synthesized adsorbents. Synthesized adsorbents possess high surface area with mesoporous structure. The adsorbents have been thoroughly investigated for the adsorption of F − using batch adsorption method. MgO nanoparticle loading on mesoporous Al 2 O 3 enhances the F − adsorption capacity of Al 2 O 3 from 56% to 90% (initial F − concentration = 10 mg L −1 ). Kinetic study revealed that adsorption kinetics follows the pseudo-second order model, suggesting the chemisorption mechanism. The F − adsorption isotherm data was explained by both Langmuir and Freundlich model. The maximum adsorption capacity of 40MgO@Al 2 O 3 was 37.35 mg g −1 . It was also observed that, when the solutions having F − concentration of 5 mg L −1 and 10 mg L −1 was treated with 40MgO@Al 2 O 3 , the F − concentration in treated water became <1 mg L −1 , which is well below the recommendation of WHO

  11. Thermal conductivity and viscosity of Al2O3 nanofluid based on car engine coolant

    International Nuclear Information System (INIS)

    Kole, Madhusree; Dey, T K

    2010-01-01

    Various suspensions containing Al 2 O 3 nanoparticles ( 2 O 3 nanoparticles as well as temperature between 10 and 80 0 C. The prepared nanofluid, containing only 0.035 volume fraction of Al 2 O 3 nanoparticles, displays a fairly higher thermal conductivity than the base fluid and a maximum enhancement (k nf /k bf ) of ∼10.41% is observed at room temperature. The thermal conductivity enhancement of the Al 2 O 3 nanofluid based on engine coolant is proportional to the volume fraction of Al 2 O 3 . The volume fraction and temperature dependence of the thermal conductivity of the studied nanofluids present excellent correspondence with the model proposed by Prasher et al (2005 Phys. Rev. Lett. 94 025901), which takes into account the role of translational Brownian motion, interparticle potential and convection in fluid arising from Brownian movement of nanoparticles for thermal energy transfer in nanofluids. Viscosity data demonstrate transition from Newtonian characteristics for the base fluid to non-Newtonian behaviour with increasing content of Al 2 O 3 in the base fluid (coolant). The data also show that the viscosity increases with an increase in concentration and decreases with an increase in temperature. An empirical correlation of the type log(μ nf ) = A exp(-BT) explains the observed temperature dependence of the measured viscosity of Al 2 O 3 nanofluid based on car engine coolant. We further confirm that Al 2 O 3 nanoparticle concentration dependence of the viscosity of nanofluids is very well predicted on the basis of a recently reported theoretical model (Masoumi et al 2009 J. Phys. D: Appl. Phys. 42 055501), which considers Brownian motion of nanoparticles in the nanofluid.

  12. Calculation of Al2O3 contents in Al2O3-PTFE composite thick films fabricated by using the aerosol deposition

    International Nuclear Information System (INIS)

    Kim, Hyung-Jun; Kim, Yoon-Hyun; Nam, Song-Min; Yoon, Young-Joon; Kim, Jong-Hee

    2010-01-01

    Low-temperature fabrication of Al 2 O 3 -PTFE (poly tetra fluoro ethylene) composite thick films for flexible integrated substrates was attempted by using the aerosol deposition method. For optimization of composite thick films, a novel calculation method for the ceramic contents in the composites was attempted. Generally, a thermogravimetry (TG) analysis is used to calculate the ceramic contents in the ceramic-polymer composites. However, the TG analysis requires a long measurement time in each analysis, so we studied a novel calculation method that used a simple dielectric measurement. We used Hashin-Shtrikman bounds to obtain numerical results for the relationship between the dielectric constant of the composites and the contents of Al 2 O 3 . A 3-D electrostatic simulation model similar to the deposited Al 2 O 3 -PTFE composite thick films was prepared, and the simulation result was around the lower bound of the Hashin-Shtrikman bounds. As a result, we could calculate the Al 2 O 3 contents in the composites with a low error of below 5 vol.% from convenient dielectric measurements, and the Al 2 O 3 contents ranged from 51 vol.% to 54 vol.%.

  13. Phenomenological theory of size effects in ultrafine ferroelectric particles (PbTiO3-type)

    International Nuclear Information System (INIS)

    Jiang, B.; Bursill, L.A.

    1998-01-01

    A new phenomenological model is proposed and discussed to study the size effects on phase transitions in PbTiO 3 -type ferroelectric particles. This model, by taking size effects on the phenomenological Landau-Ginzburg-Devonshire coefficients into consideration, can successfully explain the size effects on Curie temperature, c/a ratio, thermal and dielectric properties of lead-titanate-type ferroelectric particles. Theoretical and experimental results for PbTiO 3 fine particles are also compared and discussed. The relationship between the current model and the model of Zhong et al (Phys. Rev. B 50, 698 (1994)) is also presented. (authors)

  14. Luminescence and energy transfer of Tb3+-doped BaO-Gd2O3-Al2O3-B2O3-SiO2 glasses.

    Science.gov (United States)

    Zuo, Chenggang; Huang, Jinze; Liu, Shaoyou; Xiao, Anguo; Shen, Youming; Zhang, Xiangyang; Zhou, Zhihua; Zhu, Ligang

    2017-12-05

    Transparent Tb 3+ -doped BaO-Gd 2 O 3 -Al 2 O 3 -B 2 O 3 -SiO 2 glasses with the greater than 4g/cm 3 were prepared by high temperature melting method and its luminescent properties have been investigated by measured UV-vis transmission, excitation, emission and luminescence decay spectra. The transmission spectrum shows there are three weak absorption bands locate at about 312, 378 and 484nm in the glasses and it has good transmittance in the visible spectrum region. Intense green emission can be observed under UV excitation. The effective energy transfer from Gd 3+ ion to Tb 3+ ion could occur and sensitize the luminescence of Tb 3+ ion. The green emission intensity of Tb 3+ ion could change with the increasing SiO 2 /B 2 O 3 ratio in the borosilicate glass matrix. With the increasing concentration of Tb 3+ ion, 5 D 4 → 7 F J transitions could be enhanced through the cross relaxation between the two nearby Tb 3+ ions. Luminescence decay time of 2.12ms from 546nm emission is obtained. The results indicate that Tb 3+ -doped BaO-Gd 2 O 3 -Al 2 O 3 -B 2 O 3 -SiO 2 glasses would be potential scintillating material for applications in X-ray imaging. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Liquid Acquisition Device Hydrogen Outflow Testing on the Cryogenic Propellant Storage and Transfer Engineering Design Unit

    Science.gov (United States)

    Zimmerli, Greg; Statham, Geoff; Garces, Rachel; Cartagena, Will

    2015-01-01

    As part of the NASA Cryogenic Propellant Storage and Transfer (CPST) Engineering Design Unit (EDU) testing with liquid hydrogen, screen-channel liquid acquisition devices (LADs) were tested during liquid hydrogen outflow from the EDU tank. A stainless steel screen mesh (325x2300 Dutch T will weave) was welded to a rectangular cross-section channel to form the basic LAD channel. Three LAD channels were tested, each having unique variations in the basic design. The LADs fed a common outflow sump at the aft end of the 151 cu. ft. volume aluminum tank, and included a curved section along the aft end and a straight section along the barrel section of the tank. Wet-dry sensors were mounted inside the LAD channels to detect when vapor was ingested into the LADs during outflow. The use of warm helium pressurant during liquid hydrogen outflow, supplied through a diffuser at the top of the tank, always led to early breakdown of the liquid column. When the tank was pressurized through an aft diffuser, resulting in cold helium in the ullage, LAD column hold-times as long as 60 minutes were achieved, which was the longest duration tested. The highest liquid column height at breakdown was 58 cm, which is 23 less than the isothermal bubble-point model value of 75 cm. This paper discusses details of the design, construction, operation and analysis of LAD test data from the CPST EDU liquid hydrogen test.

  16. Zn2(TeO3Br2

    Directory of Open Access Journals (Sweden)

    Mats Johnsson

    2008-05-01

    Full Text Available Single crystals of dizinc tellurium dibromide trioxide, Zn2(TeO3Br2, were synthesized via a transport reaction in sealed evacuated silica tubes. The compound has a layered crystal structure in which the building units are [ZnO4Br] distorted square pyramids, [ZnO2Br2] distorted tetrahedra, and [TeO3E] tetrahedra (E being the 5s2 lone pair of Te4+ joined through sharing of edges and corners to form layers of no net charge. Bromine atoms and tellurium lone pairs protrude from the surfaces of each layer towards adjacent layers. This new compound Zn2(TeO3Br2 is isostructural with the synthetic compounds Zn2(TeO3Cl2, CuZn(TeO32, Co2(TeO3Br2 and the mineral sophiite, Zn2(SeO3Cl2.

  17. Molecular outflows driven by low-mass protostars. I. Correcting for underestimates when measuring outflow masses and dynamical properties

    Energy Technology Data Exchange (ETDEWEB)

    Dunham, Michael M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 78, Cambridge, MA 02138 (United States); Arce, Héctor G. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520 (United States); Mardones, Diego [Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago (Chile); Lee, Jeong-Eun [Department of Astronomy and Space Science, Kyung Hee University, Yongin, Gyeonggi 446-701 (Korea, Republic of); Matthews, Brenda C. [National Research Council of Canada, Herzberg Astronomy and Astrophysics, 5071 W. Saanich Road, Victoria, BC V9E 2E7 (Canada); Stutz, Amelia M. [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany); Williams, Jonathan P., E-mail: mdunham@cfa.harvard.edu [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States)

    2014-03-01

    We present a survey of 28 molecular outflows driven by low-mass protostars, all of which are sufficiently isolated spatially and/or kinematically to fully separate into individual outflows. Using a combination of new and archival data from several single-dish telescopes, 17 outflows are mapped in {sup 12}CO (2-1) and 17 are mapped in {sup 12}CO (3-2), with 6 mapped in both transitions. For each outflow, we calculate and tabulate the mass (M {sub flow}), momentum (P {sub flow}), kinetic energy (E {sub flow}), mechanical luminosity (L {sub flow}), and force (F {sub flow}) assuming optically thin emission in LTE at an excitation temperature, T {sub ex}, of 50 K. We show that all of the calculated properties are underestimated when calculated under these assumptions. Taken together, the effects of opacity, outflow emission at low velocities confused with ambient cloud emission, and emission below the sensitivities of the observations increase outflow masses and dynamical properties by an order of magnitude, on average, and factors of 50-90 in the most extreme cases. Different (and non-uniform) excitation temperatures, inclination effects, and dissociation of molecular gas will all work to further increase outflow properties. Molecular outflows are thus almost certainly more massive and energetic than commonly reported. Additionally, outflow properties are lower, on average, by almost an order of magnitude when calculated from the {sup 12}CO (3-2) maps compared to the {sup 12}CO (2-1) maps, even after accounting for different opacities, map sensitivities, and possible excitation temperature variations. It has recently been argued in the literature that the {sup 12}CO (3-2) line is subthermally excited in outflows, and our results support this finding.

  18. Stomatal uptake of O3 in aspen and aspen-birch forests under free-air CO2 and O3 enrichment

    Science.gov (United States)

    Johan Uddling; Alan J. Hogg; Ronald M. Teclaw; Mary Anne. Carroll; David S. Ellsworth

    2010-01-01

    Rising atmospheric carbon dioxide (CO2) may alleviate the toxicological impacts of concurrently rising tropospheric ozone (O3) during the present century if higher CO2 is accompanied by lower stomatal conductance (gs), as assumed by many models. We investigated how elevated...

  19. Removal of diethyl phthalate from water solution by adsorption, photo-oxidation, ozonation and advanced oxidation process (UV/H2O2, O3/H2O2 and O3/activated carbon)

    International Nuclear Information System (INIS)

    Medellin-Castillo, Nahum A.; Ocampo-Pérez, Raúl; Leyva-Ramos, Roberto; Sanchez-Polo, Manuel; Rivera-Utrilla, José; Méndez-Díaz, José D.

    2013-01-01

    The objective of this work was to compare the effectiveness of conventional technologies (adsorption on activated carbon, AC, and ozonation) and technologies based on advanced oxidation processes, AOPs, (UV/H 2 O 2 , O 3 /AC, O 3 /H 2 O 2 ) to remove phthalates from aqueous solution (ultrapure water, surface water and wastewater). Diethyl phthalate (DEP) was chosen as a model pollutant because of its high water solubility (1080 mg/L at 293 K) and toxicity. The activated carbons showed a high adsorption capacity to adsorb DEP in aqueous solution (up to 858 mg/g), besides the adsorption mechanism of DEP on activated carbon is governed by dispersive interactions between π electrons of its aromatic ring with π electrons of the carbon graphene planes. The photodegration process showed that the pH solution does not significantly affect the degradation kinetics of DEP and the first-order kinetic model satisfactorily fitted the experimental data. It was observed that the rate of decomposition of DEP with the O 3 /H 2 O 2 and O 3 /AC systems is faster than that with only O 3 . The technologies based on AOPs (UV/H 2 O 2 , O 3 /H 2 O 2 , O 3 /AC) significantly improve the degradation of DEP compared to conventional technologies (O 3 , UV). AC adsorption, UV/H 2 O 2 , O 3 /H 2 O 2 , and O 3 /AC showed a high yield to remove DEP; however, the disadvantage of AC adsorption is its much longer time to reach maximum removal. The best system to treat water (ultrapure and natural) polluted with DEP is the O 3 /AC one since it achieved the highest DEP degradation and TOC removal, as well as the lower water toxicity. -- Highlights: ► Activated carbons showed a high adsorption capacity (up to 858 mg/g) to remove DEP. ► The pH solution did not significantly affect the photodegradation kinetics of DEP. ► The O 3 /H 2 O 2 and O 3 /AC systems were more efficient than O 3 to degrade DEP. ► The generation of HO • from O 3 was enhanced by ACs, mainly by those of basic nature. ► O

  20. Strain-Mediated Inverse Photoresistivity in SrRuO3/La0.7Sr0.3MnO3Superlattices

    KAUST Repository

    Liu, Heng-Jui

    2015-12-09

    © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. In the pursuit of novel functionalities by utilizing the lattice degree of freedom in complex oxide heterostructure, the control mechanism through direct strain manipulation across the interfaces is still under development, especially with various stimuli, such as electric field, magnetic field, light, etc. In this study, the superlattices consisting of colossal-magnetoresistive manganites La0.7Sr0.3MnO3 (LSMO) and photostrictive SrRuO3 (SRO) have been designed to investigate the light-dependent controllability of lattice order in the corresponding functionalities and rich interface physics. Two substrates, SrTiO3 (STO) and LaAlO3 (LAO), have been employed to provide the different strain environments to the superlattice system, in which the LSMO sublayers exhibit different orbital occupations. Subsequently, by introducing light, we can modulate the strain state and orbital preference of LSMO sublayers through light-induced expansion of SRO sublayers, leading to surprisingly opposite changes in photoresistivity. The observed photoresistivity decreases in the superlattice grown on STO substrate while increases in the superlattice grown on LAO substrate under light illumination. This work has presented a model system that demonstrates the manipulation of orbital-lattice coupling and the resultant functionalities in artificial oxide superlattices via light stimulus. A fascinating model system of optic-driven functionalities has been achieved by artificial superlattices consisting of manganite La0.7Sr0.3MnO3 (LSMO) and photostrictive SrRuO3 (SRO). With design of different initial strain and orbital states in superlattices, we can even control the photoresistivity of the superlattices in an opposite trend that cannot be achieved in pure single film.

  1. AGN outflows as neutrino sources: an observational test

    Science.gov (United States)

    Padovani, P.; Turcati, A.; Resconi, E.

    2018-04-01

    We test the recently proposed idea that outflows associated with Active Galactic Nuclei (AGN) could be neutrino emitters in two complementary ways. First, we cross-correlate a list of 94 "bona fide" AGN outflows with the most complete and updated repository of IceCube neutrinos currently publicly available, assembled by us for this purpose. It turns out that AGN with outflows matched to an IceCube neutrino have outflow and kinetic energy rates, and bolometric powers larger than those of AGN with outflows not matched to neutrinos. Second, we carry out a statistical analysis on a catalogue of [O III] λ5007 line profiles using a sample of 23,264 AGN at z values (˜6 and 18 per cent respectively, pre-trial) for relatively high velocities and luminosities. Our results are consistent with a scenario where AGN outflows are neutrino emitters but at present do not provide a significant signal. This can be tested with better statistics and source stacking. A predominant role of AGN outflows in explaining the IceCube data appears in any case to be ruled out.

  2. Formation and spatial distribution of hypervelocity stars in AGN outflows

    Science.gov (United States)

    Wang, Xiawei; Loeb, Abraham

    2018-05-01

    We study star formation within outflows driven by active galactic nuclei (AGN) as a new source of hypervelocity stars (HVSs). Recent observations revealed active star formation inside a galactic outflow at a rate of ∼ 15M⊙yr-1 . We verify that the shells swept up by an AGN outflow are capable of cooling and fragmentation into cold clumps embedded in a hot tenuous gas via thermal instabilities. We show that cold clumps of ∼ 103 M⊙ are formed within ∼ 105 yrs. As a result, stars are produced along outflow's path, endowed with the outflow speed at their formation site. These HVSs travel through the galactic halo and eventually escape into the intergalactic medium. The expected instantaneous rate of star formation inside the outflow is ∼ 4 - 5 orders of magnitude greater than the average rate associated with previously proposed mechanisms for producing HVSs, such as the Hills mechanism and three-body interaction between a star and a black hole binary. We predict the spatial distribution of HVSs formed in AGN outflows for future observational probe.

  3. Strain induced optical properties of BaReO3

    Science.gov (United States)

    Kumavat, Sandip R.; Kansara, Shivam; Gupta, Sanjeev K.; Sonvane, Yogesh

    2018-05-01

    Here, we have performed strain induce optical properties of BaReO3 by using density functional theory (DFT). We noticed that after applying intrinsic and extrinsic strain to the BaReO3, it shows the metallic behavior. We also studied optical properties, which show good activity in the ultraviolet region. The results show that after applying intrinsic and extrinsic strain to BaReO3 the absorption peaks are shifted towards the high UV region of the spectrum. Thus, we concluded that, BaReO3 material with extrinsic strain can be useful for high frequency UV device and optoelectronic devices.

  4. Estimation of future outflows of e-waste in India

    International Nuclear Information System (INIS)

    Dwivedy, Maheshwar; Mittal, R.K.

    2010-01-01

    The purpose of this study is to construct an approach and a methodology to estimate the future outflows of electronic waste (e-waste) in India. Consequently, the study utilizes a time-series multiple lifespan end-of-life model proposed by Peralta and Fontanos for estimating the current and future quantities of e-waste in India. The model estimates future e-waste generation quantities by modeling their usage and disposal. The present work considers two scenarios for the approximation of e-waste generation based on user preferences to store or to recycle the e-waste. This model will help formal recyclers in India to make strategic decisions in planning for appropriate recycling infrastructure and institutional capacity building. Also an extension of the model proposed by Peralta and Fontanos is developed with the objective of helping decision makers to conduct WEEE estimates under a variety of assumptions to suit their region of study. During 2007-2011, the total WEEE estimates will be around 2.5 million metric tons which include waste from personal computers (PC), television, refrigerators and washing machines. During the said period, the waste from PC will account for 30% of total units of WEEE generated.

  5. The unusual magnetism of nanoparticle LaCoO3

    International Nuclear Information System (INIS)

    Durand, A M; Belanger, D P; Hamil, T J; Ye, F; Chi, S; Fernandez-Baca, J A; Booth, C H; Abdollahian, Y; Bhat, M

    2015-01-01

    Bulk and nanoparticle powders of LaCoO 3 (LCO) were synthesized and their magnetic and structural properties were studied using SQUID magnetometry and neutron diffraction. The bulk and large nanoparticles exhibit weak ferromagnetism (FM) below T ≈ 85 K and a crossover from strong to weak antiferromagnetic (AFM) correlations near a transition expressed in the lattice parameters, T o ≈40 K. This crossover does not occur in the smallest nanoparticles; instead, the magnetic behavior is predominantly ferromagnetic. The amount of FM in the nanoparticles depends on the amount of Co 3 O 4 impurity phase, which induces tensile strain on the LCO lattice. A core-interface model is introduced, with the core region exhibiting the AFM crossover and with FM in the interface region near surfaces and impurity phases. (paper)

  6. Superparamagnetism in AFM Cr2O3 nanoparticles

    International Nuclear Information System (INIS)

    Tobia, D.; Winkler, E.L.; Zysler, R.D.; Granada, M.; Troiani, H.E.

    2010-01-01

    In this work we report the size effects on the magnetic properties of AFM Cr 2 O 3 nanoparticles. From transmission electron microscopy we determined that the system presents high crystallinity and narrow lognormal size distribution centred at = 7.8 nm with σ = 0.3. The magnetic properties of the nanoparticles were studied by magnetization and electron paramagnetic resonance (EPR) experiments. By EPR spectroscopy we established that the AFM order temperature, T N , shifted to ∼270 K when the size is reduced (T N (Bulk) ∼ 308 K). From the zero-field-cooling and the field-cooling magnetization curves we determined the blocking temperature T B = 28 K. Below T B the system presents exchange bias effect. We discuss the results by using recent models in terms of the internal magnetic structures of the nanoparticles.

  7. Fabrication of Li_2TiO_3 pebbles by a selective laser sintering process

    International Nuclear Information System (INIS)

    Zhou, Qilai; Gao, Yue; Liu, Kai; Xue, Lihong; Yan, Youwei

    2015-01-01

    Highlights: • Selective laser sintering (SLS) is employed to fabricate ceramic pebbles. • Quantities and diameter of the pebbles could be easily controlled by adjusting the model of pebbles. • All the pebbles could be prepared at a time within several minutes. • The Li_2TiO_3 pebbles sintered at 1100 °C show a notable crush load of 43 N. - Abstract: Lithium titanate, Li_2TiO_3, is an important tritium breeding material for deuterium (D)–tritium (T) fusion reactor. In test blanket module (TBM) design of China, Li_2TiO_3 is considered as one candidate material of tritium breeders. In this study, selective laser sintering (SLS) technology was introduced to fabricate Li_2TiO_3 ceramic pebbles. This fabrication process is computer assisted and has a high level of flexibility. Li_2TiO_3 powder with a particle size of 1–3 μm was used as the raw material, whilst epoxy resin E06 was adopted as a binder. Green Li_2TiO_3 pebbles with certain strengths were successfully prepared via SLS. Density of the green pebbles was subsequently increased by cold isostatic pressing (CIP) process. Li_2TiO_3 pebbles with a diameter of about 2 mm were obtained after high temperature sintering. Density of the pebbles reaches 80% of theoretical density (TD) with a comparable crush load of 43 N. This computer assisted approach provides a new efficient route for the production of Li_2TiO_3 ceramic pebbles.

  8. Accessible switching of electronic defect type in SrTi O3 via biaxial strain

    Science.gov (United States)

    Chi, Yen-Ting; Youssef, Mostafa; Sun, Lixin; Van Vliet, Krystyn J.; Yildiz, Bilge

    2018-05-01

    Elastic strain is used widely to alter the mobility of free electronic carriers in semiconductors, but a predictive relationship between elastic lattice strain and the extent of charge localization of electronic defects is still underdeveloped. Here we considered SrTi O3 , a prototypical perovskite as a model functional oxide for thin film electronic devices and nonvolatile memories. We assessed the effects of biaxial strain on the stability of electronic defects at finite temperature by combining density functional theory (DFT) and quasiharmonic approximation (QHA) calculations. We constructed a predominance diagram for free electrons and small electron polarons in this material, as a function of biaxial strain and temperature. We found that biaxial tensile strain in SrTi O3 can stabilize the small polaron, leading to a thermally activated and slower electronic transport, consistent with prior experimental observations on SrTi O3 and distinct from our prior theoretical assessment of the response of SrTi O3 to hydrostatic stress. These findings also resolved apparent conflicts between prior atomistic simulations and conductivity experiments for biaxially strained SrTi O3 thin films. Our computational approach can be extended to other functional oxides, and for the case of SrTi O3 our findings provide concrete guidance for conditions under which strain engineering can shift the electronic defect type and concentration to modulate electronic transport in thin films.

  9. Outflow and hot dust emission in broad absorption line quasars

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shaohua; Zhou, Hongyan [Polar Research Institute of China, 451 Jinqiao Road, Shanghai 200136 (China); Wang, Huiyuan; Wang, Tinggui; Xing, Feijun; Jiang, Peng [Key Laboratory for Research in Galaxies and Cosmology, University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026 (China); Zhang, Kai, E-mail: zhangshaohua@pric.gov.cn, E-mail: whywang@mail.ustc.edu.cn [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)

    2014-05-01

    We have investigated a sample of 2099 broad absorption line (BAL) quasars with z = 1.7-2.2 built from the Sloan Digital Sky Survey Data Release Seven and the Wide-field Infrared Survey. This sample is collected from two BAL quasar samples in the literature and is refined by our new algorithm. Correlations of outflow velocity and strength with a hot dust indicator (β{sub NIR}) and other quasar physical parameters—such as an Eddington ratio, luminosity, and a UV continuum slope—are explored in order to figure out which parameters drive outflows. Here β{sub NIR} is the near-infrared continuum slope, which is a good indicator of the amount of hot dust emission relative to the accretion disk emission. We confirm previous findings that outflow properties moderately or weakly depend on the Eddington ratio, UV slope, and luminosity. For the first time, we report moderate and significant correlations of outflow strength and velocity with β{sub NIR} in BAL quasars. It is consistent with the behavior of blueshifted broad emission lines in non-BAL quasars. The statistical analysis and composite spectra study both reveal that outflow strength and velocity are more strongly correlated with β{sub NIR} than the Eddington ratio, luminosity, and UV slope. In particular, the composites show that the entire C IV absorption profile shifts blueward and broadens as β{sub NIR} increases, while the Eddington ratio and UV slope only affect the high and low velocity part of outflows, respectively. We discuss several potential processes and suggest that the dusty outflow scenario, i.e., that dust is intrinsic to outflows and may contribute to the outflow acceleration, is most likely.

  10. Electric field effects in graphene/LaAlO3/SrTiO3 heterostructures and nanostructures

    Directory of Open Access Journals (Sweden)

    Mengchen Huang

    2015-06-01

    Full Text Available We report the development and characterization of graphene/LaAlO3/SrTiO3 heterostructures. Complex-oxide heterostructures are created by pulsed laser deposition and are integrated with graphene using both mechanical exfoliation and transfer from chemical-vapor deposition on ultraflat copper substrates. Nanoscale control of the metal-insulator transition at the LaAlO3/SrTiO3 interface, achieved using conductive atomic force microscope lithography, is demonstrated to be possible through the graphene layer. LaAlO3/SrTiO3-based electric field effects using a graphene top gate are also demonstrated. The ability to create functional field-effect devices provides the potential of graphene-complex-oxide heterostructures for scientific and technological advancement.

  11. ALMA Studies of the Disk-Jet-Outflow Connection

    Science.gov (United States)

    Dougados, Catherine; Louvet, F.; Mardones, D.; Cabrit, S.

    2017-06-01

    I will describe in this contribution recent results obtained with ALMA on the origin of the disk/jet/outflow connexion in T Tauri stars. I will first present ALMA observations of the disk associated with the jet source Th 28, which question previous jet rotation measurements in this source and the implications drawn from them. I will then discuss Cycle 2 ALMA observations of the disk and small scale CO outflow associated with the prototypical edge-on HH 30 source. The unprecedented angular resolution of this dataset brings new constraints on the origin of the CO outflows in young stars.

  12. Investigation of cerebral venous outflow in microgravity.

    Science.gov (United States)

    Taibi, A; Gadda, G; Gambaccini, M; Menegatti, E; Sisini, F; Zamboni, P

    2017-10-31

    The gravitational gradient is the major component to face when considering the physiology of venous return, and there is a growing interest in understanding the mechanisms ensuring the heart filling, in the absence of gravity, for astronauts who perform long-term space missions. The purpose of the Drain Brain project was to monitor the cerebral venous outflow of a crew member during an experiment on the International Space Station (ISS), so as to study the compensatory mechanisms that facilitate this essential physiological action in subjects living in a microgravity environment. Such venous function has been characterized by means of a novel application of strain-gauge plethysmography which uses a capacitive sensor. In this contribution, preliminary results of our investigation have been presented. In particular, comparison of plethysmography data confirmed that long duration spaceflights lead to a redistribution of venous blood volume, and showed interesting differences in the amplitude of cardiac oscillations measured at the level of the neck veins. The success of the experiment has also demonstrated that thanks to its easy portability, non-invasiveness, and non-operator dependence, the proposed device can be considered as a novel tool for use aboard the ISS. Further trials are now under way to complete the investigation on the drainage function of the neck veins in microgravity.

  13. Prehistory effect on dielectric properties of NaNbO3-Gd1/3NbO3

    International Nuclear Information System (INIS)

    Burkhanov, A.I.; Bondarenko, P.V.; Shil'nikov, A.V.; Raevskaya, S.I.; Raevskij, I.P.

    2006-01-01

    One studied the low- and the infralow-frequency dielectric response of 0.9NaNbO 3 -0.1Gd 1/3 NbO 3 (NNG10) composition ceramics and single crystal at the material different prehistory. One revealed the differences in the nature of dielectric aging in NaNbO 3 antiferroelectric base material with a diffused phase transition in contrast to manifestation of similar phenomena in ferroelectrics-relaxors [ru

  14. Direct Observation of Room-Temperature Stable Magnetism in LaAlO3/SrTiO3 Heterostructures.

    Science.gov (United States)

    Yang, Ming; Ariando; Zhou, Jun; Asmara, Teguh Citra; Krüger, Peter; Yu, Xiao Jiang; Wang, Xiao; Sanchez-Hanke, Cecilia; Feng, Yuan Ping; Venkatesan, T; Rusydi, Andrivo

    2018-03-21

    Along with an unexpected conducting interface between nonmagnetic insulating perovskites LaAlO 3 and SrTiO 3 (LaAlO 3 /SrTiO 3 ), striking interfacial magnetisms have been observed in LaAlO 3 /SrTiO 3 heterostructures. Interestingly, the strength of the interfacial magnetic moment is found to be dependent on oxygen partial pressures during the growth process. This raises an important, fundamental question on the origin of these remarkable interfacial magnetic orderings. Here, we report a direct evidence of room-temperature stable magnetism in a LaAlO 3 /SrTiO 3 heterostructure prepared at high oxygen partial pressure by using element-specific soft X-ray magnetic circular dichroism at both Ti L 3,2 and O K edges. By combining X-ray absorption spectroscopy at both Ti L 3,2 and O K edges and first-principles calculations, we qualitatively ascribe that this strong magnetic ordering with dominant interfacial Ti 3+ character is due to the coexistence of LaAlO 3 surface oxygen vacancies and interfacial (Ti Al -Al Ti ) antisite defects. On the basis of this new understanding, we revisit the origin of the weak magnetism in LaAlO 3 /SrTiO 3 heterostructures prepared at low oxygen partial pressures. Our calculations show that LaAlO 3 surface oxygen vacancies are responsible for the weak magnetism at the interface. Our result provides direct evidence on the presence of room-temperature stable magnetism and a novel perspective to understand magnetic and electronic reconstructions at such strategic oxide interfaces.

  15. Ensemble and Bias-Correction Techniques for Air-Quality Model Forecasts of Surface O3 and PM2.5 during the TEXAQS-II Experiment of 2006

    Science.gov (United States)

    Several air quality forecasting ensembles were created from seven models, running in real-time during the 2006 Texas Air Quality (TEXAQS-II) experiment. These multi-model ensembles incorporated a diverse set of meteorological models, chemical mechanisms, and emission inventories...

  16. LOW-ALTITUDE RECONNECTION INFLOW-OUTFLOW OBSERVATIONS DURING A 2010 NOVEMBER 3 SOLAR ERUPTION

    Energy Technology Data Exchange (ETDEWEB)

    Savage, Sabrina L.; Holman, Gordon; Su, Yang [NASA/Goddard Space Flight Center, Oak Ridge Associated Universities, 8800 Greenbelt Road, Code 671, Greenbelt, MD 20771 (United States); Reeves, Katharine K. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street MS 58, Cambridge, MA 02138 (United States); Seaton, Daniel B. [Royal Observatory of Belgium-SIDC, Avenue Circulaire 3, B-1180 Brussels (Belgium); McKenzie, David E. [Department of Physics, Montana State University, P.O. Box 173840, Bozeman, MT 59717-3840 (United States)

    2012-07-20

    For a solar flare occurring on 2010 November 3, we present observations using several SDO/AIA extreme-ultraviolet (EUV) passbands of an erupting flux rope followed by inflows sweeping into a current sheet region. The inflows are soon followed by outflows appearing to originate from near the termination point of the inflowing motion-an observation in line with standard magnetic reconnection models. We measure average inflow plane-of-sky speeds to range from {approx}150 to 690 km s{sup -1} with the initial, high-temperature inflows being the fastest. Using the inflow speeds and a range of Alfven speeds, we estimate the Alfvenic Mach number which appears to decrease with time. We also provide inflow and outflow times with respect to RHESSI count rates and find that the fast, high-temperature inflows occur simultaneously with a peak in the RHESSI thermal light curve. Five candidate inflow-outflow pairs are identified with no more than a minute delay between detections. The inflow speeds of these pairs are measured to be {approx}10{sup 2} km s{sup -1} with outflow speeds ranging from {approx}10{sup 2} to 10{sup 3} km s{sup -1}-indicating acceleration during the reconnection process. The fastest of these outflows are in the form of apparently traveling density enhancements along the legs of the loops rather than the loop apexes themselves. These flows could possibly either be accelerated plasma, shocks, or waves prompted by reconnection. The measurements presented here show an order of magnitude difference between the retraction speeds of the loops and the speed of the density enhancements within the loops-presumably exiting the reconnection site.

  17. LOW-ALTITUDE RECONNECTION INFLOW-OUTFLOW OBSERVATIONS DURING A 2010 NOVEMBER 3 SOLAR ERUPTION

    International Nuclear Information System (INIS)

    Savage, Sabrina L.; Holman, Gordon; Su, Yang; Reeves, Katharine K.; Seaton, Daniel B.; McKenzie, David E.

    2012-01-01

    For a solar flare occurring on 2010 November 3, we present observations using several SDO/AIA extreme-ultraviolet (EUV) passbands of an erupting flux rope followed by inflows sweeping into a current sheet region. The inflows are soon followed by outflows appearing to originate from near the termination point of the inflowing motion—an observation in line with standard magnetic reconnection models. We measure average inflow plane-of-sky speeds to range from ∼150 to 690 km s –1 with the initial, high-temperature inflows being the fastest. Using the inflow speeds and a range of Alfvén speeds, we estimate the Alfvénic Mach number which appears to decrease with time. We also provide inflow and outflow times with respect to RHESSI count rates and find that the fast, high-temperature inflows occur simultaneously with a peak in the RHESSI thermal light curve. Five candidate inflow-outflow pairs are identified with no more than a minute delay between detections. The inflow speeds of these pairs are measured to be ∼10 2 km s –1 with outflow speeds ranging from ∼10 2 to 10 3 km s –1 —indicating acceleration during the reconnection process. The fastest of these outflows are in the form of apparently traveling density enhancements along the legs of the loops rather than the loop apexes themselves. These flows could possibly either be accelerated plasma, shocks, or waves prompted by reconnection. The measurements presented here show an order of magnitude difference between the retraction speeds of the loops and the speed of the density enhancements within the loops—presumably exiting the reconnection site.

  18. Damped soft phonons and diffuse scattering in 40%Pb(Mg1/3Nb2/3)O3-60%PbTiO3

    International Nuclear Information System (INIS)

    Stock, C.; Ellis, D.; Swainson, I. P.; Xu, Guangyong; Hiraka, H.; Shirane, G.; Zhong, Z.; Luo, H.; Zhao, X.; Viehland, D.; Birgeneau, R. J.

    2006-01-01

    Using neutron elastic and inelastic scattering and high-energy x-ray diffraction, we present a comparison of 40% Pb(Mg 1/3 Nb 2/3 )O 3 -60% PbTiO 3 (PMN-60PT) with pure Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) and PbTiO 3 (PT). We measure the structural properties of PMN-60PT to be identical to pure PT, however, the lattice dynamics are exactly that previously found in relaxors PMN and Pb(Zn 1/3 Nb 2/3 )O 3 (PZN). PMN-60PT displays a well-defined macroscopic structural transition from a cubic to tetragonal unit cell at 550 K. The diffuse scattering is shown to be weak indicating that the structural distortion is long-range in PMN-60PT and short-range polar correlations (polar nanoregions) are not present. Even though polar nanoregions are absent, the soft optic mode is short-lived for wave vectors near the zone center. Therefore PMN-60PT displays the same waterfall effect as prototypical relaxors PMN and PZN. We conclude that it is random fields resulting from the intrinsic chemical disorder which is the reason for the broad transverse optic mode observed in PMN and PMN-60PT near the zone center and not due to the formation of short-ranged polar correlations. Through our comparison of PMN, PMN-60PT, and pure PT, we interpret the dynamic and static properties of the PMN-xPT system in terms of a random field model in which the cubic anisotropy term dominates with increasing doping of PbTiO 3

  19. Synthesis of ferrite grade γ-Fe2O3

    Indian Academy of Sciences (India)

    Unknown

    carboxylates in air yield α-Fe2O3, but the controlled atmosphere of moisture requires for the oxalates to stabi- ... structure form, α-Fe2O3, is made to react with the cubic divalent metal .... water of crystallization show multistep exothermic peaks.

  20. BiFeO3 Crystal Structure at Low Temperatures

    International Nuclear Information System (INIS)

    Palewicz, A.; Sosnowska, I.; Przenioslo, R.; Hewat, A.W.

    2010-01-01

    The crystal and magnetic structure of BiFeO 3 have been studied with the use of high resolution neutron diffraction between 5 K and 300 K. The atomic coordinates in BiFeO 3 are almost unchanged between 5 K and 300 K. (authors)

  1. Catalytic Methane Decomposition over Fe-Al2O3

    KAUST Repository

    Zhou, Lu; Enakonda, Linga Reddy; Saih, Youssef; Loptain, Sergei; Gary, Daniel; Del-Gallo, Pascal; Basset, Jean-Marie

    2016-01-01

    The presence of a Fe-FeAl2O4 structure over an Fe-Al2O3 catalysts is demonstrated to be vital for the catalytic methane decomposition (CMD) activity. After H2 reduction at 750°C, Fe-Al2O3 prepared by means of a fusion method, containing 86.5wt% Fe

  2. Photoelectrochemical properties of LaRhO3

    International Nuclear Information System (INIS)

    Viswanathan, B.; Narayanan, S.R.; Viswanath, R.P.; Varadrajan, T.K.

    1982-01-01

    The photoelectrochemical properties of LaRhO 3 at different values of pH were studied by current-voltage measurements and cyclic voltammetry and the results obtained are compared with those obtained for LaRhO 3 , a potential photoelectrode. (author)

  3. Facile combustion synthesis of novel CaZrO 3

    Indian Academy of Sciences (India)

    Abstract. A facile sol–gel combustion route was reported for the direct preparation of CaZrO3:Eu3+ and CaZrO3:Eu3+, Gd3+. The obtained deposits were characterized by XRD, TGA-DSC, SEM, EDS, PL measurements and microscope fluorescence. When the Gd3+ ions were introduced in this compound, the emissions of ...

  4. Depolarization temperature and piezoelectric properties of TiO3 ...

    Indian Academy of Sciences (India)

    WINTEC

    2TiO3–Na1/2Bi1/2(Zn1/3Nb2/3)O3, was synthesized using the two-stage calcination method and depolarization temperatures and piezoelectric properties were also investigated. The XRD analysis showed that the ceramics system had a ...

  5. NaIrO3-A pentavalent post-perovskite

    International Nuclear Information System (INIS)

    Bremholm, M.; Dutton, S.E.; Stephens, P.W.; Cava, R.J.

    2011-01-01

    Sodium iridium (V) oxide, NaIrO 3, was synthesized by a high pressure solid state method and recovered to ambient conditions. It is found to be isostructural with CaIrO 3 , the much-studied structural analog of the high-pressure post-perovskite phase of MgSiO 3 . Among the oxide post-perovskites, NaIrO 3 is the first example with a pentavalent cation. The structure consists of layers of corner- and edge-sharing IrO 6 octahedra separated by layers of NaO 8 bicapped trigonal prisms. NaIrO 3 shows no magnetic ordering and resistivity measurements show non-metallic behavior. The crystal structure, electrical and magnetic properties are discussed and compared to known post-perovskites and pentavalent perovskite metal oxides. -- Graphical abstract: Sodium iridium(V) oxide, NaIrO 3 , synthesized by a high pressure solid state method and recovered to ambient conditions is found to crystallize as the post-perovskite structure and is the first example of a pentavalent ABO 3 post-perovskite. Research highlights: → NaIrO 3 post-perovskite stabilized by pressure. → First example of a pentavalent oxide post-perovskite. → Non-metallic and non-magnetic behavior of NaIrO 3 .

  6. Manipulating Conduction in Metal Oxide Semiconductors: Mechanism Investigation and Conductance Tuning in Doped Fe2O3 Hematite and Metal/Ga2O3/Metal Heterostructure

    Science.gov (United States)

    Zhao, Bo

    switching, non-volatility, and repeatable switching are tested for the devices fabricated. Following previous discoveries on Ni/Ga2O3 single crystal which shows interface barrier type change (Schottky ↔ Ohmic) upon annealing accompanied by defects migration, characterization of the interface behavior on resistive switching cell Ni/Ga2O 3(thin film)/Ir under two different resistive states was performed using X-ray photoemission spectroscopy (XPS). Most interestingly, feathers in XPS spectrum of Ga allow for a unique nondestructive approach to investigate interface by XPS through electron transparent top contact. Theoretical modeling shows that Ga migrate towards the interface upon switching to low resistive state, indicating a possible mechanism that involves interfacial switch through barrier height modifying. Such device holds potential to become the next generation of non-volatile memory device, resistive RAM.

  7. Cumulative neutrino background from quasar-driven outflows

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiawei; Loeb, Abraham, E-mail: xiawei.wang@cfa.harvard.edu, E-mail: aloeb@cfa.harvard.edu [Department of Astronomy, Harvard University, 60 Garden Street, Cambridge, MA 02138 (United States)

    2016-12-01

    Quasar-driven outflows naturally account for the missing component of the extragalactic γ-ray background through neutral pion production in interactions between protons accelerated by the forward outflow shock and interstellar protons. We study the simultaneous neutrino emission by the same protons. We adopt outflow parameters that best fit the extragalactic γ-ray background data and derive a cumulative neutrino background of ∼ 10{sup −7} GeV cm{sup −2} s{sup −1} sr{sup −1} at neutrino energies E {sub ν} ∼> 10 TeV, which naturally explains the most recent IceCube data without tuning any free parameters. The link between the γ-ray and neutrino emission from quasar outflows can be used to constrain the high-energy physics of strong shocks at cosmological distances.

  8. Radioluminescence in Al2O3: C - analytical and numerical simulation results

    DEFF Research Database (Denmark)

    Pagonis, V.; Lawless, J.; Chen, R.

    2009-01-01

    The phenomenon of radioluminescence (RL) has been reported in a number of materials including Al2O3 : C, which is one of the main dosimetric materials. In this work, we study RL using a kinetic model involving two trapping states and two kinds of recombination centres. The model has been previous...

  9. Neutronic analysis of Gd2O3 as burnable poison

    International Nuclear Information System (INIS)

    Lecot, C.A.

    1990-01-01

    For the reactors core design, the use of burnable poisons is one of the options for the control of in excess reactivity and the power form factor. As alternative procedures, the absorbing material may be included in pellets of an inert material or in fuel pellets. Besides, a cladding material and the locations of the fuel elements must be chosen for the first case. The CAREM reactor core design foresees the use of gadolinium oxide (Gd 2 O 3 ) as burnable poison. In this work, a comparative study was made, from the neutronic point of view, among the following alternatives for the poisons location: a) Gd 2 O 3 bars supports in alumina (Al 2 O 3 ), sheathed in steel; b) Gd 2 O 3 bars supports in alumina sheathed in Zry-4; c) Gd 2 O 3 in uranium dioxide (UO 2 ) fuel pellets. (Author) [es

  10. Influence of B2O3 content on sintering behaviour and dielectric properties of La2O3-B2O3-CaO/Al2O3 glass-ceramic composites for LTCC applications

    Science.gov (United States)

    Wang, F. L.; Zhang, Y. W.; Chen, X. Y.; Mao, H. J.; Zhang, W. J.

    2018-01-01

    La2O3-B2O3-CaO glasses with different B2O3 content were synthesized by melting method to produce glass/ceramic composites in this work. XRD and DSC results revealed that the diminution of B2O3 content was beneficial to increase the crystallization tendency of glass and improve the quality of crystalline phase, while decreasing the effect of glass during sintering process as sintering aids. The choice of glass/ceramic mass ratio was also influenced by the B2O3 content of glass. Dense samples sintered at 875 ºC showed good dielectric properties which meet the requirement of LTCC applications: moderate dielectric constant (7.8-9.4) and low dielectric loss (2.0×10-3).

  11. Highly flexible, conductive and transparent MoO3/Ag/MoO3 multilayer electrode for organic photovoltaic cells

    International Nuclear Information System (INIS)

    Abachi, T.; Cattin, L.; Louarn, G.; Lare, Y.; Bou, A.; Makha, M.; Torchio, P.

    2013-01-01

    MoO 3 /Ag/MoO 3 (MAM) multilayer structures were deposited by vacuum evaporation on polyethylene terephthalate (PET) substrate. We demonstrate that, as in the case of glass substrate, the sheet resistance of such structures depends significantly on the Ag film deposition rate. When it is deposited between 0.2 and 0.4 nm/s, an Ag thickness of 11 nm allows achieving sheet resistance of 13 Ω/sq and an averaged transmission of 74%. A study of the influence of the PET substrate on the optimum MoO 3 thicknesses was done. A good qualitative agreement between the theoretical calculations of the variation of the optical transmittance of the MoO 3 /Ag/MoO 3 structures is obtained. The optimum MAM structures MoO 3 (17.5 nm)/Ag (11 nm)/MoO 3 (35 nm) has a factor of merit F M = 4.21 10 −3 (Ω/sq) −1 . Proven by the scotch test the MAM structures exhibit a good adhesion to the PET substrates. The MAM structures were also submitted to bending tests. For outer bending, the samples exhibit no variation of their resistance value, while for inner bending there is a small increase of the resistance of the MAM structures. However this increasing is smaller than that exhibited by Indium Tin Oxide. When the PET/MAM structures are used as anode in organic photovoltaic cells, it is shown that the need to use thicker Ag films inside the multilayer and to cover the MAM with Au to obtain promising Current density vs Voltage characteristics is due to the heating of the PET substrate during the deposition process. - Highlights: • MoO 3 /Ag/MoO 3 structures deposited on polyethylene terephthalate substrate. • MoO 3 /Ag/MoO 3 structures deposited by vacuum evaporation. • The Ag deposition rate influences the properties of the structures. • The MoO 3 /Ag/MoO 3 optimum structure has a factor of merit F M = 4.21 10 −3 (Ω/sq) −1 . • The MoO 3 /Ag/MoO 3 structures exhibit a high flexibility

  12. Combined use of O3/H2O2 and O3/Mn2+ in flotation of dairy wastewater

    Directory of Open Access Journals (Sweden)

    Marta Cristina Silva Carvalho

    2018-05-01

    Full Text Available This work investigated the degradation of organic matter present in synthetic dairy wastewater by the combination of ozonation (ozone (O3/hydrogen peroxide (H2O2 and catalytic ozonation (ozone (O3/manganese (Mn2+ associated with dispersed air flotation process. The effect of independent factors such as O3 concentration, pH and H2O2 and Mn2+ concentration was evaluated. For the flotation/O3/H2O2 treatment, the significant variables (p ≤ 0.05 were: O3 concentration (linear and quadratic effect, H2O2 concentration linear and quadratic effect, pH values (linear and quadratic effect and interaction O3 concentration versus pH. For catalytic ozonation, it was observed that the significant variable was the linear effect of O3 concentration. According to the desirability function, it was concluded that the optimal condition for the treatment of flotation/O3/H2O2 can be obtained in acidic solution using O3 concentrations greater than 42.9 mg L-1 combined with higher concentrations of H2O2 to 1071.5 mg L-1. On other hand, at pH values higher than 9.0, the addition of O3 may be neglected when using higher concentrations than 1071.5 mg L-1 of H2O2. For flotation/ozonation catalyzed by Mn2+, it was observed that metal addition did not affect treatment, resulting in an optimum condition: 53.8 mg L-1 of O3 and pH 3.6.

  13. SAW propagation characteristics of TeO3/3C-SiC/LiNbO3 layered structure

    Science.gov (United States)

    Soni, Namrata D.

    2018-04-01

    Surface acoustic wave (SAW) devices based on Lithium Niobate (LiNbO3) single crystal are advantageous because of its high SAW phase velocity, electromechanical coupling coefficient and cost effectiveness. In the present work a new multi-layered TeO3/3C-SiC/128° Y-X LiNbO3 SAW device has been proposed. SAW propagation properties such as phase velocity, coupling coefficient and temperature coefficient of delay (TCD) of the TeO3/SiC/128° Y-X LiNbO3 multi layered structure is examined using theoretical calculations. It is found that the integration of 0.09λ thick 3C-SiC over layer on 128° Y-X LiNbO3 increases its electromechanical coupling coefficient from 5.3% to 9.77% and SAW velocity from 3800 ms‑1 to 4394 ms‑1. The SiC/128° Y-X LiNbO3 bilayer SAW structure exhibits a high positive TCD value. A temperature stable layered SAW device could be obtained with introduction of 0.007λ TeO3 over layer on SiC/128° Y-X LiNbO3 bilayer structure without sacrificing the efficiency of the device. The proposed TeO3/3C-SiC/128° Y-X LiNbO3 multi-layered SAW structure is found to be cost effective, efficient, temperature stable and suitable for high frequency application in harsh environment.

  14. Characterization of molecular outflows in the substellar domain

    International Nuclear Information System (INIS)

    Phan-Bao, Ngoc; Dang-Duc, Cuong; Lee, Chin-Fei; Ho, Paul T. P.; Li, Di

    2014-01-01

    We report here our latest search for molecular outflows from young brown dwarfs and very low-mass stars in nearby star-forming regions. We have observed three sources in Taurus with the Submillimeter Array and the Combined Array for Research in Millimeter-wave Astronomy at 230 GHz frequency to search for CO J = 2 → 1 outflows. We obtain a tentative detection of a redshifted and extended gas lobe at about 10 arcsec from the source GM Tau, a young brown dwarf in Taurus with an estimated mass of 73 M J , which is right below the hydrogen-burning limit. No blueshifted emission around the brown dwarf position is detected. The redshifted gas lobe that is elongated in the northeast direction suggests a possible bipolar outflow from the source with a position angle of about 36°. Assuming that the redshifted emission is outflow emission from GM Tau, we then estimate a molecular outflow mass in the range from 1.9 × 10 –6 M ☉ to 2.9 × 10 –5 M ☉ and an outflow mass-loss rate from 2.7 × 10 –9 M ☉ yr –1 to 4.1 × 10 –8 M ☉ yr –1 . These values are comparable to those we have observed in the young brown dwarf ISO-Oph 102 of 60 M J in ρ Ophiuchi and the very low-mass star MHO 5 of 90 M J in Taurus. Our results suggest that the outflow process in very low-mass objects is episodic with a duration of a few thousand years and the outflow rate of active episodes does not significantly change for different stages of the formation process of very low-mass objects. This may provide us with important implications that clarify the formation process of brown dwarfs.

  15. Characterization of molecular outflows in the substellar domain

    Energy Technology Data Exchange (ETDEWEB)

    Phan-Bao, Ngoc; Dang-Duc, Cuong [Department of Physics, International University-Vietnam National University HCM, Block 6, Linh Trung Ward, Thu Duc District, Ho Chi Minh City (Viet Nam); Lee, Chin-Fei; Ho, Paul T. P. [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 106, Taiwan (China); Li, Di, E-mail: pbngoc@hcmiu.edu.vn, E-mail: pbngoc@asiaa.sinica.edu.tw [National Astronomical Observatories, Chinese Academy of Science, Chaoyang District Datun Rd A20, Beijing (China)

    2014-11-01

    We report here our latest search for molecular outflows from young brown dwarfs and very low-mass stars in nearby star-forming regions. We have observed three sources in Taurus with the Submillimeter Array and the Combined Array for Research in Millimeter-wave Astronomy at 230 GHz frequency to search for CO J = 2 → 1 outflows. We obtain a tentative detection of a redshifted and extended gas lobe at about 10 arcsec from the source GM Tau, a young brown dwarf in Taurus with an estimated mass of 73 M {sub J}, which is right below the hydrogen-burning limit. No blueshifted emission around the brown dwarf position is detected. The redshifted gas lobe that is elongated in the northeast direction suggests a possible bipolar outflow from the source with a position angle of about 36°. Assuming that the redshifted emission is outflow emission from GM Tau, we then estimate a molecular outflow mass in the range from 1.9 × 10{sup –6} M {sub ☉} to 2.9 × 10{sup –5} M {sub ☉} and an outflow mass-loss rate from 2.7 × 10{sup –9} M {sub ☉} yr{sup –1} to 4.1 × 10{sup –8} M {sub ☉} yr{sup –1}. These values are comparable to those we have observed in the young brown dwarf ISO-Oph 102 of 60 M {sub J} in ρ Ophiuchi and the very low-mass star MHO 5 of 90 M {sub J} in Taurus. Our results suggest that the outflow process in very low-mass objects is episodic with a duration of a few thousand years and the outflow rate of active episodes does not significantly change for different stages of the formation process of very low-mass objects. This may provide us with important implications that clarify the formation process of brown dwarfs.

  16. Electrical conduction of glasses in the system Fe2O3-Sb2O3-TeO2; Fe2O3-Sb2O3-TeO2 kei garasu no denki dendo

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, Honghua; Mori, H; Sakata, H; Hirayama, T [Tokai Univ., Tokyo (Japan). Faculty of Engineering

    1995-01-01

    In this study, taking into consideration that TeO2 is a component of the glass network and Sb2O3 shows the redox effect in the glasses reducing its possibility of transformation of Sb{sup 3+} to Sb{sup 5+} as well as glass basicity, highly conductive tellurite based glasses have been prepared by the press-quenching method selecting the Fe2O3-Sb2O3-TeO2 system, and the electroconductive mechanism of the glasses has been examined by measuring its D.C. conductivity {sigma}. Part of the obtained information is as follows; the glass formation range of the Fe2O3-Sb2O3-TeO2 system has been 0 {le} Fe2O3 {le} 15mol%, 0 {le} Sb2O3 {le} 18mol% and 78 {le} TeO2 {le} 100mol% and about 15mol% of the additional amount of Fe2O3 has been the limit of glass formation. As the amount of Fe2O3 has increased, C{sub Fe} has also increased and with this, the linear electroconductivity of the glasses has increased from 1.86 {times} 10{sup -7}S{center_dot}cm{sup -1} to 1.62 {times} 10{sup -6}S{center_dot}cm{sup -1} and the glasses have been confirmed as the n-type semiconductor. The factor determining {sigma} of the glasses has been C{sub Fe} which has increased as the amount of Fe2O3 has increased. 34 refs., 8 figs., 2 tabs.

  17. Relativistic Outflows from Advection-dominated Accretion Disks around Black Holes

    Science.gov (United States)

    Becker, Peter A.; Subramanian, Prasad; Kazanas, Demosthenes

    2001-05-01

    Advection-dominated accretion flows (ADAFs) have a positive Bernoulli parameter and are therefore gravitationally unbound. The Newtonian ADAF model has been generalized recently to obtain the ADIOS model that includes outflows of energy and angular momentum, thereby allowing accretion to proceed self-consistently. However, the utilization of a Newtonian gravitational potential limits the ability of this model to describe the inner region of the disk, where any relativistic outflows are likely to originate. In this paper we modify the ADIOS scenario to incorporate a pseudo-Newtonian potential, which approximates the effects of general relativity. The analysis yields a unique, self-similar solution for the structure of the coupled disk/wind system. Interesting features of the new solution include the relativistic character of the outflow in the vicinity of the radius of marginal stability, which represents the inner edge of the quasi-Keplerian disk in our model. Hence, our self-similar solution may help to explain the origin of relativistic jets in active galaxies. At large distances the radial dependence of the accretion rate approaches the unique form M~r1/2, with an associated density variation given by ρ~r-1. This density variation agrees with that implied by the dependence of the hard X-ray time lags on the Fourier frequency for a number of accreting galactic black hole candidates. While intriguing, the predictions made using our self-similar solution need to be confirmed in the future using a detailed model that includes a physical description of the energization mechanism that drives the outflow, which is likely to be powered by the shear of the underlying accretion disk.

  18. Topographic control on the nascent Mediterranean outflow

    Science.gov (United States)

    Gasser, M.; Pelegrí, J. L.; Nash, J. D.; Peters, H.; García-Lafuente, J.

    2011-12-01

    Data collected during a 12-day cruise in July 2009 served to examine the structure of the nascent Mediterranean Outflow Water (MOW) immediately west of the Espartel Sill, the westernmost sill in the Strait of Gibraltar. The MOW is characterized by high salinities (>37.0 and reaching 38.3) and high velocities (exceeding 1 m s-1 at 100 m above the seafloor), and follows a submerged valley along a 30 km stretch, the natural western extension of the strait. It is approx. 150 m thick and 10 km wide, and experiences a substantial drop from 420 to 530 m over a distance of some 3 km between two relatively flat regions. Measurements indicate that the nascent MOW behaves as a gravity current with nearly maximal traveling speed; if this condition is maintained, then the maximum MOW velocity would decrease slowly with distance from the Espartel Sill, remaining significantly high until the gravity current excess density is only a small fraction of its original value. The sharp pycnocline between the Mediterranean and the overlying North Atlantic Central waters is dynamically unstable, particularly where the flow interacts with the 100 m decrease in bottom depth. Here, subcritical gradient Richardson numbers coincide with the development of large interfacial undulations and billows. The very energetic downslope flow is likely responsible for the development of a narrow V-shaped channel downstream of the seafloor drop along the axis of the submerged valley, this probably being the very first erosional scour produced by the nascent MOW. The coincidence of subcritical gradient Richardson numbers with relatively high turbidity values above the channel flanks suggests it may be undergoing upstream erosion.

  19. Quasar outflow energetics from broad absorption line variability

    Science.gov (United States)

    McGraw, S. M.; Shields, J. C.; Hamann, F. W.; Capellupo, D. M.; Herbst, H.

    2018-03-01

    Quasar outflows have long been recognized as potential contributors to the co-evolution between supermassive black holes (SMBHs) and their host galaxies. The role of outflows in active galactic nucleus (AGN) feedback processes can be better understood by placing observational constraints on wind locations and kinetic energies. We utilize broad absorption line (BAL) variability to investigate the properties of a sample of 71 BAL quasars with P V broad absorption. The presence of P V BALs indicates that other BALs like C IV are saturated, such that variability in those lines favours clouds crossing the line of sight. We use these constraints with measurements of BAL variability to estimate outflow locations and energetics. Our data set consists of multiple-epoch spectra from the Sloan Digital Sky Survey and MDM Observatory. We detect significant (4σ) BAL variations from 10 quasars in our sample over rest-frame time-scales between ≤0.2-3.8 yr. Our derived distances for the 10 variable outflows are nominally ≲ 1-10 pc from the SMBH using the transverse-motion scenario, and ≲ 100-1000 pc from the central source using ionization-change considerations. These distances, in combination with the estimated high outflow column densities (i.e. NH ≳ 1022 cm-2), yield outflow kinetic luminosities between ˜ 0.001 and 1 times the bolometric luminosity of the quasar, indicating that many absorber energies within our sample are viable for AGN feedback.

  20. Crystal growth and spectroscopic characterization of Yb3+:LiTaO3

    International Nuclear Information System (INIS)

    Gruber, John B.; Allik, Toomas H.; Sardar, Dhiraj K.; Yow, Raylon M.; Scripsick, Michael; Wechsler, Barry

    2006-01-01

    Spectroscopic properties are presented for Yb 3+ incorporated into single crystals of LiTaO 3 grown by the top-seeded solution growth method. From an analysis of the absorption and fluorescence spectra, we are able to determine the Stark-level components of the 2 F 7/2 (the ground-state multiplet manifold) and the 2 F 5/2 (the excited-state multiplet manifold of Yb 3+ (4f 13 )). The room-temperature fluorescence lifetime of 2 F 5/2 is 678μs as measured on a thin sample to reduce possibilities for reabsorption. Spectral comparisons of Yb 3+ -doped LiTaO 3 and LiNbO 3 are drawn. The crystal-field splitting of Yb 3+ (4f 13 ) in both crystal hosts is modeled using a set of crystal-field splitting parameters, B nm , determined from a recent spectroscopic analysis of Er 3+ (4f 11 ) in LiNbO 3 . Without adjustment of the B nm parameters, the model predicts the Stark-level energy and the symmetry label for each level in reasonable agreement with the experimental values. Less photorefractive than its niobate cousin, LiTaO 3 has potential for use in numerous integrated electro-optical circuits and devices

  1. The Vaporization of B2O3(l) to B2O3(g) and B2O2(g)

    Science.gov (United States)

    Jacobson, Nathan S.; Myers, Dwight L.

    2011-01-01

    The vaporization of B2O3 in a reducing environment leads to formation of both B2O3(g) and B2O2(g). While formation of B2O3(g) is well understood, many questions about the formation of B2O2(g) remain. Previous studies using B(s) + B2O3(l) have led to inconsistent thermodynamic data. In this study, it was found that after heating, B(s) and B2O3(l) appear to separate and variations in contact area likely led to the inconsistent vapor pressures of B2O2(g). To circumvent this problem, an activity of boron is fixed with a two-phase mixture of FeB and Fe2B. Both second and third law enthalpies of formation were measured for B2O2(g) and B2O3(g). From these the enthalpies of formation at 298.15 K are calculated to be -479.9 +/- 41.5 kJ/mol for B2O2(g) and -833.4 +/- 13.1 kJ/mol for B2O3(g). Ab initio calculations to determine the enthalpies of formation of B2O2(g) and B2O3(g) were conducted using the W1BD composite method and show good agreement with the experimental values.

  2. High charge carrier density at the NaTaO3/SrTiO3 hetero-interface

    KAUST Repository

    Nazir, Safdar; Schwingenschlö gl, Udo

    2011-01-01

    The formation of a (quasi) two-dimensional electron gas between the band insulators NaTaO3 and SrTiO3 is studied by means of the full-potential linearized augmented plane-wave method of density functional theory. Optimization of the atomic positions

  3. Favorable ultraviolet photoelectric effects in TbMnO3/Nb-SrTiO3 heterostructures

    KAUST Repository

    Jin, Kexin; Zhai, Y. X.; Li, Hui; Tian, Y. F.; Luo, B. C.; Wu, Tao

    2014-01-01

    The rectifying properties and ultraviolet photoelectric effects in TbMnO3/Nb-doped SrTiO3 heterostructures have been investigated. The ideality factors and the diffusion voltages obtained from the current-voltage curves nonlinearly decrease

  4. Stability and electronic structure studies of LaAlO3/SrTiO3 (110) heterostructures

    International Nuclear Information System (INIS)

    Du Yan-Ling; Wang Chun-Lei; Li Ji-Chao; Xu Pan-Pan; Zhang Xin-Hua; Liu Jian; Su Wen-Bin; Mei Liang-Mo

    2014-01-01

    The first-principles calculations are employed to investigate the stability, magnetic, and electrical properties of the oxide heterostructure of LaAlO 3 /SrTiO 3 (110). By comparing their interface energies, it is obtained that the buckled interface is more stable than the abrupt interface. This result is consistent with experimental observation. At the interface of LaAlO 3 /SrTiO 3 (110) heterostructure, the Ti—O octahedron distortions cause the Ti t 2g orbitals to split into the two-fold degenerate d xz /d yz and nondegenerate d xy orbitals. The former has higher energy than the latter. The partly filled two-fold degenerate t 2g orbitals are the origin of two-dimensional electron gas, which is confined at the interface. Lattice mismatch between LaAlO 3 and SrTiO 3 leads to ferroelectric-like lattice distortions at the interface, and this is the origin of spin-splitting of Ti 3d electrons. Hence the magnetism appears at the interface of LaAlO 3 /SrTiO 3 (110). (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  5. Magnetic properties of the alkali metal ozonides KO3, RbO3, and CsO3

    International Nuclear Information System (INIS)

    Lueken, H.; Deussen, M.; Jansen, M.; Hesse, W.; Schnick, W.

    1987-01-01

    The magnetic susceptibilities of KO 3 , RbO 3 and CsO 3 have been determined between 3.6 and 250 K. Above 50 K Curie-Weiss behaviour is observed. Magnetic moments of 1.74 μ B (KO 3 , CsO 3 ) and 1.80 μ B (RbO 3 ) calculated from the Curie-Weiss straight lines correspond with spin-only moments expected for isolated O 3 - species with one unpaired electron. The Weiss constants Θ are -34 K (KO 3 ), -23 K (RbO 3 ) and -10 K (CsO 3 ). The low temperature behaviour of KO 3 and RbO 3 (broad maxima in susceptibility at 20 and 17 K, respectively, and minima at 6 K) is typical of systems which show with decreasing temperature low-dimensional antiferromagnetic and three-dimensional magnetic ordering. Inspecting the intermolecular distances between oxygen atoms the pathways of exchange interactions are discussed. (author)

  6. Trends in (LaMnO3)n/(SrTiO3)m superlattices with varying layer thicknesses

    KAUST Repository

    Jilili, J.; Cossu, Fabrizio; Schwingenschlö gl, Udo

    2015-01-01

    We investigate the thickness dependence of the structural, electronic, and magnetic properties of (LaMnO3)n/(SrTiO3)m (n, m = 2, 4, 6, 8) superlattices using density functional theory. The electronic structure turns out to be highly sensitive

  7. Contributions of conduction band offset to the enhanced separation efficiency of photoinduced charges for SrTiO3/Bi2O3 heterojunction semiconductor

    International Nuclear Information System (INIS)

    Zhang, Zhenlong; Zhu, Jichun; Li, Shengjun; Mao, Yanli

    2014-01-01

    SrTiO 3 /Bi 2 O 3 heterojunction semiconductor was prepared and characterized by X-ray diffraction, UV–vis absorption spectrum, and scanning electron microscope, surface photovoltage spectroscopy, and photoluminescence spectroscopy. The surface photovoltage spectra indicate that the separation efficiency of photoinduced charges for SrTiO 3 /Bi 2 O 3 was enhanced compared with that of SrTiO 3 or Bi 2 O 3 . The energy band diagram of SrTiO 3 /Bi 2 O 3 heterojunction was directly determined with X-ray photoelectron spectroscopy, and the conduction band offset between SrTiO 3 and Bi 2 O 3 was quantified to be 0.28±0.03 eV. The photoluminescence spectra display that the recombination rate of photoinduced carriers for SrTiO 3 /Bi 2 O 3 decreases compared with that of SrTiO 3 or Bi 2 O 3 , which is mainly due to the energy levels matching between them. Therefore the enhanced separation efficiency of photoinduced charges is resulting from the energy difference between the conduction band edges of SrTiO 3 and Bi 2 O 3 . -- Graphical abstract: Enhanced separation efficiency for SrTiO 3 /Bi 2 O 3 is resulting from the energy difference between the conduction band edges. Highlights: ●Heterojunction semiconductor of SrTiO 3 /Bi 2 O 3 was prepared. ●SrTiO 3 /Bi 2 O 3 presents enhanced separation efficiency. ●Conduction band offset between SrTiO 3 and Bi 2 O 3 is quantified. ●Recombination rate of SrTiO 3 /Bi 2 O 3 decreases compared with single phases

  8. Upper-tropospheric CO and O3 budget during the Asian summer monsoon

    Directory of Open Access Journals (Sweden)

    B. Barret

    2016-07-01

    Full Text Available During the Asian summer monsoon, the circulation in the upper troposphere/lower stratosphere (UTLS is dominated by the Asian monsoon anticyclone (AMA. Pollutants convectively uplifted to the upper troposphere are trapped within this anticyclonic circulation that extends from the Pacific Ocean to the Eastern Mediterranean basin. Among the uplifted pollutants are ozone (O3 and its precursors, such as carbon monoxide (CO and nitrogen oxides (NOx. Many studies based on global modeling and satellite data have documented the source regions and transport pathways of primary pollutants (CO, HCN into the AMA. Here, we aim to quantify the O3 budget by taking into consideration anthropogenic and natural sources. We first use CO and O3 data from the MetOp-A/IASI sensor to document their tropospheric distributions over Asia, taking advantage of the useful information they provide on the vertical dimension. These satellite data are used together with MOZAIC tropospheric profiles recorded in India to validate the distributions simulated by the global GEOS-Chem chemistry transport model. Over the Asian region, UTLS monthly CO and O3 distributions from IASI and GEOS-Chem display the same large-scale features. UTLS CO columns from GEOS-Chem are in agreement with IASI, with a low bias of 11 ± 9 % and a correlation coefficient of 0.70. For O3, the model underestimates IASI UTLS columns over Asia by 14 ± 26 % but the correlation between both is high (0.94. GEOS-Chem is further used to quantify the CO and O3 budget through sensitivity simulations. For CO, these simulations confirm that South Asian anthropogenic emissions have a more important impact on enhanced concentrations within the AMA (∼  25 ppbv than East Asian emissions (∼  10 ppbv. The correlation between enhanced emissions over the Indo-Gangetic Plain and monsoon deep convection is responsible for this larger impact. Consistently, South Asian anthropogenic NOx emissions also

  9. GEOMETRIC AND KINEMATIC STRUCTURE OF THE OUTFLOW/ENVELOPE SYSTEM OF L1527 REVEALED BY SUBARCSECOND-RESOLUTION OBSERVATION OF CS

    Energy Technology Data Exchange (ETDEWEB)

    Oya, Yoko; López-Sepulcre, Ana; Watanabe, Yoshimasa; Yamamoto, Satoshi [Department of Physics, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Sakai, Nami [The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198 (Japan); Lefloch, Bertrand; Ceccarelli, Cecilia, E-mail: oya@taurus.phys.s.u-tokyo.ac.jp [Universite Grenoble Alpes, IPAG, F-38000 Grenoble (France)

    2015-10-10

    Subarcsecond-resolution images of the rotational line emissions of CS and c-C{sub 3}H{sub 2} obtained toward the low-mass protostar IRAS 04368+2557 in L1527 with the Atacama Large Millimeter/submillimeter Array are investigated to constrain the orientation of the outflow/envelope system. The distribution of CS consists of an envelope component extending from north to south and a faint butterfly shaped outflow component. The kinematic structure of the envelope is well reproduced by a simple ballistic model of an infalling rotating envelope. Although the envelope has a nearly edge-on configuration, we find that the western side of the envelope faces the observer. This configuration is opposite to the direction of the large-scale (∼10{sup 4} AU) outflow suggested previously from the {sup 12}CO (J = 3–2) observation, and to the morphology of infrared reflection near the protostar (∼200 AU). The latter discrepancy could originate from high extinction by the outflow cavity of the western side, or may indicate that the outflow axis is not parallel to the rotation axis of the envelope. Position–velocity diagrams show the accelerated outflow cavity wall, and its kinematic structure in the 2000 AU scale is explained by a standard parabolic model with the inclination angle derived from the analysis of the envelope. The different orientation of the outflow between the small and large scale implies a possibility of precession of the outflow axis. The shape and the velocity of the outflow in the vicinity of the protostar are compared with those of other protostars.

  10. Effects of climate change, CO2 and O3 on wheat productivity in Eastern China, singly and in combination

    Science.gov (United States)

    Tao, Fulu; Feng, Zhaozhong; Tang, Haoye; Chen, Yi; Kobayashi, Kazuhiko

    2017-03-01

    Air pollution and climate change are increasing threats to agricultural production and food security. Extensive studies have focused on the effect of climate change, but the interactive effects of multiple global change factors are poorly understood. Here, we incorporate the interactions between climate change, carbon dioxide (CO2) and ozone (O3) into an eco-physiological mechanistic model based on three years of O3 Free-Air Concentration Elevation (O3-FACE) experiments. We then investigate the effects of climate change, elevated CO2 concentration ([CO2]) and rising O3 concentration ([O3]) on wheat growth and productivity in eastern China in 1996-2005 (2000s) and 2016-2025 (2020s) under two climate change scenarios, singly and in combination. We find the interactive effects of climate change, CO2 and O3 on wheat productivity have spatially explicit patterns; the effect of climate change dominates the general pattern, which is however subject to the large uncertainties of climate change scenarios. Wheat productivity is estimated to increase by 2.8-9.0% due to elevated [CO2] however decline by 2.8-11.7% due to rising [O3] in the 2020s, relative to the 2000s. The combined effects of CO2 and O3 are less than that of O3 only, on average by 4.6-5.2%, however with O3 damage outweighing CO2 benefit in most of the region. This study demonstrates a more biologically meaningful and appropriate approach for assessing the interactive effects of climate change, CO2 and O3 on crop growth and productivity. Our findings promote the understanding on the interactive effects of multiple global change factors across contrasting climate conditions, cast doubt on the potential of CO2 fertilization effect in offsetting possible negative effect of climate change on crop productivity as suggested by many previous studies.

  11. Electronic properties of Fe2+ in MTiO3

    International Nuclear Information System (INIS)

    Ito, A.; Morimoto, S.

    1975-01-01

    Moessbauer spectra were observed in a temperature range from 4.2 to 300 K for the ilmenite structure compounds MTiO 3 -2 % 57 Fe (M = Mg, Mn-I, Fe, Co, Ni) and for the disordered ilmenite structure compound MnTiO 2 -II-1 % 57 Fe. The Neel temperature and the spin orientation of host materials are tabulated. A well resolved quadrupole doublet was observed for all the samples at temperatures above the respective Neel temperatures. Below the Neel temperature a magnetic structure appeared. The Moessbauer spectra obtained at 4.2 K are presented. The spectra were analyzed on the basis of the well-known Hamiltonian for sup(57m)Fe. Moessbauer parameters obtained are tabulated. Analyzing the spectra at 4.2 K, quadrupole interaction was determined to be negative in MnTiO 3 -II and positive in all other compounds. Hyperfine magnetic field intensities observed a6 4.2 K were 34, 85, 47, 105 and 91 kOe for MnTiO 3 -I, MnTiO 3 -II, FeTiO 3 , CoTiO 3 and NiTiO 3 , respectively. (Z.S.)

  12. Zn2(TeO3)Br2

    Science.gov (United States)

    Zhang, Dong; Johnsson, Mats

    2008-01-01

    Single crystals of dizinc tellurium dibromide trioxide, Zn2(TeO3)Br2, were synthesized via a transport reaction in sealed evacuated silica tubes. The compound has a layered crystal structure in which the building units are [ZnO4Br] distorted square pyramids, [ZnO2Br2] distorted tetra­hedra, and [TeO3 E] tetra­hedra (E being the 5s 2 lone pair of Te4+) joined through sharing of edges and corners to form layers of no net charge. Bromine atoms and tellurium lone pairs protrude from the surfaces of each layer towards adjacent layers. This new compound Zn2(TeO3)Br2 is isostructural with the synthetic compounds Zn2(TeO3)Cl2, CuZn(TeO3)2, Co2(TeO3)Br2 and the mineral sophiite, Zn2(SeO3)Cl2. PMID:21202162

  13. Production of the entire range of r-process nuclides by black hole accretion disc outflows from neutron star mergers

    Science.gov (United States)

    Wu, Meng-Ru; Fernández, Rodrigo; Martínez-Pinedo, Gabriel; Metzger, Brian D.

    2016-12-01

    We consider r-process nucleosynthesis in outflows from black hole accretion discs formed in double neutron star and neutron star-black hole mergers. These outflows, powered by angular momentum transport processes and nuclear recombination, represent an important - and in some cases dominant - contribution to the total mass ejected by the merger. Here we calculate the nucleosynthesis yields from disc outflows using thermodynamic trajectories from hydrodynamic simulations, coupled to a nuclear reaction network. We find that outflows produce a robust abundance pattern around the second r-process peak (mass number A ˜ 130), independent of model parameters, with significant production of A spike at A = 132 that is absent in the Solar system r-process distribution. The spike arises from convection in the disc and depends on the treatment of nuclear heating in the simulations. We conclude that disc outflows provide an important - and perhaps dominant - contribution to the r-process yields of compact binary mergers, and hence must be included when assessing the contribution of these systems to the inventory of r-process elements in the Galaxy.

  14. A comparative study of radiation damage in Al2O3, FeTiO3, and MgTiO3

    International Nuclear Information System (INIS)

    Mitchell, J.N.; Yu, Ning; Sickafus, K.E.; Nastasi, M.; Taylor, T.N.; McClellan, K.J.; Nord, G.L. Jr.

    1995-01-01

    Oriented single crystals of synthetic alpha-alumina (α-Al 2 O 3 ), geikielite (MgTiO 3 ) natural ilmenite (FeTiO 3 ) were irradiated with 200 keV argon ions under cryogenic conditions (100 K) to assess their damage response. Using Rutherford backscattering spectrometry combined with ion channeling techniques, it was found that ilmenite amorphized readily at doses below 5x10 14 , alumina amorphized at a dose of 1-2x 15 , and geikielite was amorphized at ∼2x10 15 Ar cm -2 . The radiation damage response of the ilmenite crystal may be complicated by the presence of hematite exsolution lamellae and the experimentally induced oxidation of iron. The relative radiation-resistance of geikielite holds promise for similar behavior in other Mg-Ti oxides

  15. Identifying open-volume defects in doped and undoped perovskite-type LaCoO3, PbTiO3, and BaTiO3

    International Nuclear Information System (INIS)

    Ghosh, Vinita J.; Nielsen, Bent; Friessnegg, Thomas

    2000-01-01

    Dopants, vacancies, and impurity-vacancy clusters have a substantial impact on the properties of perovskite-type metal oxides (general formula ABO 3 ). In order to determine synthesis and processing conditions that optimize the desirable properties of these materials a careful study of these defects is required. It is essential to identify the defects and to map the defect densities. Positron annihilation spectroscopy has often been used to identify vacancy-type defects. Calculations of the positron lifetime and Doppler-broadened profiles of the positron-electron annihilation radiation in undoped and doped LaCoO 3 , PbTiO 3 , and BaTiO 3 are reported, and compared with available experimental data. The results show that these positron techniques are excellent for studying open-volume defects, vacancy-impurity complexes, and for identifying the sublattice occupied by the dopants. (c) 2000 The American Physical Society

  16. Optical properties of SrTiO3 films

    International Nuclear Information System (INIS)

    Agasiyev, A.A.; Magerramov, E.M.; Mammadov, M.Z.; Sarmasov, S.M.

    2010-01-01

    The spectrums of optical absorption of amorphous and single crystalline films SrTiO 3 at temperatures : 105 K, 300 K, 400 K are investigated. The temperature dependences of slope absorption edge, forbidden gap and characteristic constant of Urbah rule are obtained. The forbidden gap of single crystalline film SrTiO 3 and average shift shift of absorption edge degree are defined. It is established that edge of optical absorption of SrTiO 3 film is obeyed to Urbah rule and the absorption in the investigated region is caused by the transition of electron interacting with phonon

  17. Properties of MoO3 thin film polymorphs

    International Nuclear Information System (INIS)

    McCarron, E.M.; Carcia, P.F.

    1987-01-01

    Thin film polymorphs of molybdenum trioxide have been synthesized by RF sputtering. Films deposited on thermally floating substrates are polycrystalline and exhibit preferred orientation. Depending upon the oxygen partial pressure maintained during sputtering, the films can be made to crystallize in either the thermodynamically stable orthorhombic α MoO 3 form (unique 2D-layered structure) or the metastable monoclinic β MoO 3 phase (3D ReO 3 -related structure). Metastable β films can be converted thermally to the α phase and the transformation appears topotactic. Films deposited on the cooled substrates are amorphous. A correlation between the particular phase formed and adatom mobility is noted

  18. Synthesis and characterization of FeTiO3 ceramics

    OpenAIRE

    Anil B. Gambhire; Machhindra K. Lande; Sandip B. Rathod; Balasaheb R. Arbad; Kaluram N. Vidhate; Ramakrishna S. Gholap; Kashinath R. Patil

    2016-01-01

    Nanocrystalline FeTiO3 ceramic powders were prepared by the sol–gel process combined with a surfactant-assisted template method. The resulting powders were calcined at different temperatures ranging from 150 °C to 600 °C for 2 h in air. The results revealed that a pure hexagonal phase of FeTiO3 could be obtained at a low temperature, 600 °C. The phase evolution of FeTiO3 was investigated by X-ray diffraction patterns (XRD), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelect...

  19. Electrical compensation by Ga vacancies in Ga2O3

    OpenAIRE

    Korhonen, Esa; Tuomisto, F.; Gogova, D.; Wagner, G.; Baldini, M.; Galazka, Z.; Schewski, R.; Albrecht, M.

    2015-01-01

    The authors have applied positron annihilation spectroscopy to study the vacancy defects in undoped and Si-doped Ga2O3 thin films. The results show that Ga vacancies are formed efficiently during metal-organic vapor phase epitaxy growth of Ga2O3 thin films. Their concentrations are high enough to fully account for the electrical compensation of Si doping. This is in clear contrast to another n-type transparent semiconducting oxide In2O3, where recent results show that n-type conductivity is n...

  20. Cathodoluminescence from beta-Ga_2O_3 nanowires

    OpenAIRE

    Nogales Díaz, Emilio; Méndez Martín, Bianchi; Piqueras de Noriega, Javier

    2005-01-01

    ß-Ga_2O_3 nano- and microwires with diameters ranging from tens of nanometers to about one micron and lengths of up to tens of microns, have been obtained by sintering Ga_2O_3 powder under argon flow. The structures have been investigated by cathodoluminescence in the scanning electron microscope. The samples showed the violet-blue emission characteristic of Ga_2O_3 and a red emission at 1.73 eV dominant in the nanowires and other nano- and microstructures formed during the sintering treatmen...

  1. Synthesis of metallic ReO3 nanowires

    International Nuclear Information System (INIS)

    Myung, Dongshin; Lee, Yumin; Lee, Jaeyeon; Kim, Myung Hwa; Yu, Hak Ki; Lee, Jong-Lam; Baik, Jeong Min; Kim, Woong

    2010-01-01

    We present the synthesis of highly crystalline metallic rhenium trioxide (ReO 3 ) nanowires via a simple physical vapor transport at 300 C for the first time. Based on HRTEM, the ReO 3 nanowires exhibit a core of perfect cubic perovskite-type single crystal structure with a shell of thin amorphous and disordered structures of less than 2 nm in the near surface layers. Possibly this is due to proton intercalation induced by the surface reaction of single crystal ReO 3 with water. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Synthesis of nanometre-thick MoO3 sheets

    Science.gov (United States)

    Kalantar-Zadeh, Kourosh; Tang, Jianshi; Wang, Minsheng; Wang, Kang L.; Shailos, Alexandros; Galatsis, Kosmas; Kojima, Robert; Strong, Veronica; Lech, Andrew; Wlodarski, Wojtek; Kaner, Richard B.

    2010-03-01

    The formation of MoO3 sheets of nanoscale thickness is described. They are made from several fundamental sheets of orthorhombic α-MoO3, which can be processed in large quantities via a low cost synthesis route that combines thermal evaporation and mechanical exfoliation. These fundamental sheets consist of double-layers of linked distorted MoO6 octahedra. Atomic force microscopy (AFM) measurements show that the minimum resolvable thickness of these sheets is 1.4 nm which is equivalent to the thickness of two double-layers within one unit cell of the α-MoO3 crystal.

  3. Al atom on MoO3(010) surface: adsorption and penetration using density functional theory.

    Science.gov (United States)

    Wu, Hong-Zhang; Bandaru, Sateesh; Wang, Da; Liu, Jin; Lau, Woon Ming; Wang, Zhenling; Li, Li-Li

    2016-03-14

    Interfacial issues, such as the interfacial structure and the interdiffusion of atoms at the interface, are fundamental to the understanding of the ignition and reaction mechanisms of nanothermites. This study employs first-principle density functional theory to model Al/MoO3 by placing an Al adatom onto a unit cell of a MoO3(010) slab, and to probe the initiation of interfacial interactions of Al/MoO3 nanothermite by tracking the adsorption and subsurface-penetration of the Al adatom. The calculations show that the Al adatom can spontaneously go through the topmost atomic plane (TAP) of MoO3(010) and reach the 4-fold hollow adsorption-site located below the TAP, with this subsurface adsorption configuration being the most preferred one among all plausible adsorption configurations. Two other plausible configurations place the Al adatom at two bridge sites located above the TAP of MoO3(010) but the Al adatom can easily penetrate below this TAP to a relatively more stable adsorption configuration, with a small energy barrier of merely 0.2 eV. The evidence of subsurface penetration of Al implies that Al/MoO3 likely has an interface with intermixing of Al, Mo and O atoms. These results provide new insights on the interfacial interactions of Al/MoO3 and the ignition/combustion mechanisms of Al/MoO3 nanothermites.

  4. Winter- and summertime continental influences on tropospheric O3 and CO observed by TES over the western North Atlantic Ocean

    Directory of Open Access Journals (Sweden)

    R. Talbot

    2010-04-01

    mixing ratios to >110 ppbv with O3-CO slopes >0.50 mol mol−1 south of 45° N. Intense cyclones, which were not as common in the summer, enhanced export by lofting of boundary layer pollutants from over the US and also provided a possible mechanism for transporting pollutants from boreal fire outflow southward to the US east coast. Overall, for winter and summer the TES retrievals showed substantial evidence of air pollution export to the western North Atlantic Ocean with the most distinct differences in distribution patterns related to strong influences of mid-latitude cyclones in winter and the Bermuda High anticyclone in summer.

  5. Positron annihilation lifetime study of positive temperature coefficient BaTiO3 samples

    International Nuclear Information System (INIS)

    Ling Chen; Mingkang Teng; Guanghou Wang; Xiaoyun Li; Tianchang Lu

    1989-01-01

    In order to investigate the doped vacancies in BaTiO 3 samples as well as their influence on the positive temperature coefficient (PTC) the positron annihilation lifetime spectroscopy was applied. Two groups of BaTiO 3 samples with BaO excess were prepared by doping different concentrations of La 2 O 3 and Nb 2 O 5 , respectively in the range from 0.1 to 3 at%. A third group of samples of two Sb-doped PTC BaTiO 3 semiconductors with excess BaO or TiO 2 were studied by the aid of positron technique before and after being reduced. It is shown that the positron lifetime parameters are sensitive to changes in the vacancy concentration in BaTiO 3 ceramics near the 0.1 mol% region. But they are almost unchanged during reduction processing; the resistivity of samples changed by one to two orders of magnitude through the reduction. It can be concluded that the PTC effect is due to oxygen on the grain boundary rather than vacancies, and that the Heywang-Jonker model is more reasonable

  6. Lithium recovery from salt lake brine by H2TiO3.

    Science.gov (United States)

    Chitrakar, Ramesh; Makita, Yoji; Ooi, Kenta; Sonoda, Akinari

    2014-06-21

    The details of the ion exchange properties of layered H2TiO3, derived from the layered Li2TiO3 precursor upon treatment with HCl solution, with lithium ions in the salt lake brine (collected from Salar de Uyuni, Bolivia) are reported. The lithium adsorption rate is slow, requiring 1 d to attain equilibrium at room temperature. The adsorption of lithium ions by H2TiO3 follows the Langmuir model with an adsorptive capacity of 32.6 mg g(-1) (4.7 mmol g(-1)) at pH 6.5 from the brine containing NaHCO3 (NaHCO3 added to control the pH). The total amount of sodium, potassium, magnesium and calcium adsorbed from the brine was lithium ions from the brine containing competitive cations such as sodium, potassium, magnesium and calcium in extremely large excess. The results indicate that the selectivity order Li(+) ≫ Na(+), K(+), Mg(2+), Ca(2+) originates from a size effect. The H2TiO3 can be regenerated and reused for lithium exchange in the brine with an exchange capacity very similar to the original H2TiO3.

  7. Canted antiferromagnetic and optical properties of nanostructures of Mn2O3 prepared by hydrothermal synthesis

    International Nuclear Information System (INIS)

    Javed, Qurat-ul-ain; Feng-Ping Wang; Rafique, M. Yasir; Toufiq, Arbab Mohammad; Iqbal, M. Zubair

    2012-01-01

    We have reported new magnetic and optical properties of Mn 2 O 3 nanostructures. The nanostructures have been synthesized by the hydrothermal method combined with the adjustment of pH values in the reaction system. The particular characteristics of the nanostructures have been analyzed by employing X-Ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS), UV—visible spectroscopy, and the vibrating sample magnetometer (VSM). Structural investigation manifests that the synthesized Mn 2 O 3 nanostructures are orthorhombic crystal. Magnetic investigation indicates that the Mn 2 O 3 nanostructures are antiferromagnetic and the antiferromagnetic transition temperature is at T N = 83 K. Furthermore, the Mn 2 O 3 nanostructures possess canted antiferromagnetic order below the Neel temperature due to spin frustration, resulting in hysteresis with large coercivity (1580 Oe) and remnant magnetization (1.52 emu/g). The UV—visible spectrophotometry was used to determine the transmittance behaviour of Mn 2 O 3 nanostructures. A direct optical band gap of 1.2 eV was acquired by using the Davis—Mott model. The UV—visible spectrum indicates that the absorption is prominent in the visible region, and transparency is more than 80% in the UV region

  8. Aircraft observations of aerosols O3 and NOy in a nighttime urban plume

    International Nuclear Information System (INIS)

    Berkowitz, C.M.; Zaveri, R.A.; Xindi Bian; Shiyuan Zhong; Disselkamp, R.S.; Laulainen, N.S.; Chapman, E.G.

    2001-01-01

    Nighttime measurements of aerosol surface area, O 3 , NO y and moisture were made downwind of Portland, Oregon, as part of a study to characterize the chemistry in a nocturnal urban plume. Air parcels sampled within the urban plume soon after sunset had positive correlations between O 3 , relative humidity, NO y and aerosol number density. However, the air parcels sampled within the urban plume just before dawn had O 3 mixing ratios that were highly anti-correlated with aerosol number density, NO y and relative humidity. Back-trajectories from a mesoscale model show that both the post-sunset and pre-dawn parcels came from a common maritime source to the northwest of Portland. The pre-dawn parcels with strong anti-correlations passed directly over Portland in contrast to the other parcels that were found to pass west of Portland. Several gas-phase mechanisms and a heterogeneous mechanism involving the loss of O 3 to the aerosol surface, are examined to explain the observed depletion in O 3 within the pre-dawn parcels that had passed over Portland. (Author)

  9. OUTFLOW AND HOT DUST EMISSION IN HIGH-REDSHIFT QUASARS

    International Nuclear Information System (INIS)

    Wang, Huiyuan; Xing, Feijun; Wang, Tinggui; Zhou, Hongyan; Zhang, Kai; Zhang, Shaohua

    2013-01-01

    Correlations of hot dust emission with outflow properties are investigated, based on a large z ∼ 2 non-broad absorption line quasar sample built from the Wide-field Infrared Survey and the Sloan Digital Sky Survey data releases. We use the near-infrared slope and the infrared to UV luminosity ratio to indicate the hot dust emission relative to the emission from the accretion disk. In our luminous quasars, these hot dust emission indicators are almost independent of the fundamental parameters, such as luminosity, Eddington ratio and black hole mass, but moderately dependent on the blueshift and asymmetry index (BAI) and FWHM of C IV lines. Interestingly, the latter two correlations dramatically strengthen with increasing Eddington ratio. We suggest that, in high Eddington ratio quasars, C IV regions are dominated by outflows so the BAI and FWHM (C IV) can reliably reflect the general properties and velocity of outflows, respectively. In low Eddington ratio quasars, on the other hand, C IV lines are primarily emitted by virialized gas so the BAI and FWHM (C IV) become less sensitive to outflows. Therefore, the correlations for the highest Eddington ratio quasars are more likely to represent the true dependence of hot dust emission on outflows and the correlations for the entire sample are significantly diluted by the low Eddington ratio quasars. Our results show that an outflow with a large BAI or velocity can double the hot dust emission on average. We suggest that outflows either contain hot dust in themselves or interact with the dusty interstellar medium or torus

  10. Particulate waste outflow from fish-farming cages. How much is uneaten feed?

    Science.gov (United States)

    Ballester-Moltó, M; Sanchez-Jerez, P; Cerezo-Valverde, J; Aguado-Giménez, F

    2017-06-15

    Particulate wastes drive benthic organic enrichment from cage fish farming. Differentiation between faeces and uneaten feed estimates at cage level are of great value to both economize the feeding process and reduce waste. This study estimates the particulate waste outflowing cages at different depths and orientations, and the wasted feed component by combining in situ measurements and modelling. Particulate matter flux (PMF) was greater vertically through the cage bottoms (60.89%), but lateral outflow was also substantial (39.11%). PMF occurs all around the cages, and the influence of the mainstream current was low. Wasted feed was greatly variable, reaching high values (about 50% of supplied feed. The self-application of feed wastage monitoring and estimates by fish farmers is recommended to improve sustainability. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Revealing the ultrafast outflow in IRAS 13224-3809 through spectral variability

    Science.gov (United States)

    Parker, M. L.; Alston, W. N.; Buisson, D. J. K.; Fabian, A. C.; Jiang, J.; Kara, E.; Lohfink, A.; Pinto, C.; Reynolds, C. S.

    2017-08-01

    We present an analysis of the long-term X-ray variability of the extreme narrow-line Seyfert 1 galaxy IRAS 13224-3809 using principal component analysis (PCA) and fractional excess variability (Fvar) spectra to identify model-independent spectral components. We identify a series of variability peaks in both the first PCA component and Fvar spectrum which correspond to the strongest predicted absorption lines from the ultrafast outflow (UFO) discovered by Parker et al. (2017). We also find higher order PCA components, which correspond to variability of the soft excess and reflection features. The subtle differences between RMS and PCA results argue that the observed flux-dependence of the absorption is due to increased ionization of the gas, rather than changes in column density or covering fraction. This result demonstrates that we can detect outflows from variability alone and that variability studies of UFOs are an extremely promising avenue for future research.

  12. Low energy spin dynamics of rare-earth orthoferrites YFeO3 and LaFeO3

    Science.gov (United States)

    Park, Kisoo; Sim, Hasung; Leiner, Jonathan; Yoshida, Yoshiyuki; Eisaki, Hiroshi; Yano, Shinichiro; Gardner, Jason; Park, Je-Geun

    YFeO3 and LaFeO3\\ are members of the rare-earth orthoferrites (RFeO3) family with Pbnm space group. With the strong superexchange interaction between Fe3 + ions, both compounds exhibit the room temperature antiferromagnetic order (TN >600 K) with a slight spin canting. Here we report low-energy magnetic excitation of YFeO3 and LaFeO3 using inelastic neutron scattering measurements, showing evidence of magnon mode splitting and a spin anisotropy gap at the zone center. Spin wave calculations with the spin Hamiltonian including both Dzyaloshinsky-Moriya interaction and single-ion anisotropy accounts for the observed features well. Our results offer insight into the underlying physics of other RFeO3\\ with magnetic rare-earth ions or related Fe3+-based multiferroic perovskites such as BiFeO3. The work at the IBS CCES (South Korea) was supported by the research program of the Institute for Basic Science (IBS-R009-G1).

  13. Preparation, structural, dielectric and magnetic properties of LaFeO3–PbTiO3 solid solutions

    International Nuclear Information System (INIS)

    Ivanov, S.A.; Tellgren, R.; Porcher, F.; Ericsson, T.; Mosunov, A.; Beran, P.; Korchagina, S.K.; Kumar, P. Anil; Mathieu, R.; Nordblad, P.

    2012-01-01

    Highlights: ► Solid-solutions of (1−x)LaFeO 3 –(x)PbTiO 3 were synthesized by solid-state reaction. ► XRPD and NPD evidence orthorhombic (x 0.8) crystal structures. ► LaFeO 3 -rich compositions order antiferromagnetically (x 3 -rich compositions exhibit ferroelectric order (x larger than 0.8). ► Magnetic and dielectric (relaxor) ordering coexist near room-temperature around x = 0.4. -- Abstract: Solid solutions of (1−x)LaFeO 3 –(x)PbTiO 3 (0 3+ cations in the B-site with propagation vector k = (0,0,0). Based on the obtained experimental data, a combined structural and magnetic phase diagram has been constructed. The factors governing the structural, dielectric and magnetic properties of (1−x)LaFeO 3 –(x)PbTiO 3 solid solutions are discussed, as well as their possible multiferroicity.

  14. Ultra-Fast Outflows in Radio-Loud AGN: New Constraints on Jet-Disk Connection

    Science.gov (United States)

    Sambruna, Rita

    There is strong observational and theoretical evidence that outflows/jets are coupled to accretion disks in black hole accreting systems, from Galactic to extragalactic sizes. While in radio-quiet AGN there is ample evidence for the presence of Ultra-Fast Outflows (UFOs) from the presence of blue-shifted absorption features in their 4-10~keV spectra, sub-relativistic winds are expected on theoretical basis in radio-loud AGN but have not been observed until now. Our recent Suzaku observations of 5 bright Broad- Line Radio Galaxies (BLRGs, the radio-loud counterparts of Seyferts) has started to change this picture. We found strong evidence for UFOs in 3 out of 5 BLRGs, with ionization parameters, column densities, and velocities of the absorber similar to Seyferts. Moreover, the outflows in BLRGs are likely to be energetically very significant: from the Suzaku data of the three sources, outflow masses similar to the accretion masses and kinetic energies of the wind similar to the X-ray luminosity and radio power of the jet are inferred. Clearly, UFOs in radio-loud AGN represent a new key ingredient to understand their central engines and in particular, the jet-disk linkage. Our discovery of UFOs in a handful of BLRGs raises the questions of how common disk winds are in radio-loud AGN, what the absorber physical and dynamical characteristics are, and what is the outflow role in broader picture of galaxy-black hole connection for radio sources, i.e., for large-scale feedback models. To address these and other issues, we propose to use archival XMM-Newton and Suzaku spectra to search for Ultra-Fast Outflows in a large number of radio sources. Over a period of two years, we will conduct a systematic, uniform analysis of the archival X-ray data, building on our extensive experience with a similar previous project for Seyferts, and using robust analysis and statistical methodologies. As an important side product, we will also obtain accurate, self- consistent measurements

  15. FLAPW Study of the EFG Tensor at Cd Impurities in In2O3

    International Nuclear Information System (INIS)

    Errico, L. A.; Renteria, M.; Fabricius, G.; Darriba, G. N.

    2004-01-01

    We report an ab initio study of the electric-field gradient tensor (EFG) at Cd impurities located at both nonequivalent cationic sites in the semiconductor In 2 O 3 . Calculations were performed with the FLAPW method that allows us to treat the electronic structure of the doped system and the atomic relaxations introduced by the impurities in the host in a fully self-consistent way. From our results for the EFG (in excellent agreement with the experiments), it is clear that the problem of the EFG at Cd impurities in In 2 O 3 cannot be described by the point-charge model and antishielding factors.

  16. Strongly gapped spin-wave excitation in the insulating phase of NaOsO3

    International Nuclear Information System (INIS)

    Calder, S.; Vale, J. G.; Bogdanov, N.; Donnerer, C.

    2017-01-01

    NaOsO_3 hosts a rare manifestation of a metal-insulator transition driven by magnetic correlations, placing the magnetic exchange interactions in a central role. We use resonant inelastic x-ray scattering to directly probe these magnetic exchange interactions. A dispersive and strongly gapped (58 meV) excitation is observed indicating appreciable spin-orbit coupling in this 5d"3 system. The excitation is well described within a minimal model Hamiltonian with strong anisotropy and Heisenberg exchange (J_1 = J_2 = 13.9 meV). As a result, the observed behavior places NaOsO_3 on the boundary between local