WorldWideScience

Sample records for two-dimensional 2d gas

  1. A new model for two-dimensional numerical simulation of pseudo-2D gas-solids fluidized beds

    Energy Technology Data Exchange (ETDEWEB)

    Li, Tingwen; Zhang, Yongmin

    2013-10-11

    Pseudo-two dimensional (pseudo-2D) fluidized beds, for which the thickness of the system is much smaller than the other two dimensions, is widely used to perform fundamental studies on bubble behavior, solids mixing, or clustering phenomenon in different gas-solids fluidization systems. The abundant data from such experimental systems are very useful for numerical model development and validation. However, it has been reported that two-dimensional (2D) computational fluid dynamic (CFD) simulations of pseudo-2D gas-solids fluidized beds usually predict poor quantitative agreement with the experimental data, especially for the solids velocity field. In this paper, a new model is proposed to improve the 2D numerical simulations of pseudo-2D gas-solids fluidized beds by properly accounting for the frictional effect of the front and back walls. Two previously reported pseudo-2D experimental systems were simulated with this model. Compared to the traditional 2D simulations, significant improvements in the numerical predictions have been observed and the predicted results are in better agreement with the available experimental data.

  2. Two-Dimensional Gel Electrophoresis and 2D-DIGE.

    Science.gov (United States)

    Meleady, Paula

    2018-01-01

    Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) continues to be one of the most versatile and widely used techniques to study the proteome of a biological system. In particular, a modified version of 2D-PAGE, two-dimensional difference gel electrophoresis (2D-DIGE), which uses differential labeling of protein samples with up to three fluorescent tags, offers greater sensitivity and reproducibility over conventional 2D-PAGE gels for differential quantitative analysis of protein expression between experimental groups. Both these methods have distinct advantages in the separation and identification of thousands of individual proteins species including protein isoforms and post-translational modifications. This review will discuss the principles of 2D-PAGE and 2D-DIGE including limitations to the methods. 2D-PAGE and 2D-DIGE continue to be popular methods in bioprocessing-related research (particularly on recombinant Chinese hamster ovary cells), which will also be discussed in the review chapter.

  3. Two-Dimensional (2D) Polygonal Electromagnetic Cloaks

    Institute of Scientific and Technical Information of China (English)

    LI Chao; YAO Kan; LI Fang

    2009-01-01

    Transformation optics offers remarkable control over electromagnetic fields and opens an exciting gateway to design 'invisible cloak devices' recently.We present an important class of two-dimensional (2D) cloaks with polygon geometries.Explicit expressions of transformed medium parameters are derived with their unique properties investigated.It is found that the elements of diagonalized permittivity tensors are always positive within an irregular polygon cloak besides one element diverges to plus infinity and the other two become zero at the inner boundary.At most positions,the principle axes of permittivity tensors do not align with position vectors.An irregular polygon cloak is designed and its invisibility to external electromagnetic waves is numerically verified.Since polygon cloaks can be tailored to resemble any objects,the transformation is finally generalized to the realization of 2D cloaks with arbitrary geometries.

  4. Forensic potential of comprehensive two-dimensional gas chromatography

    NARCIS (Netherlands)

    Sampat, A.; Lopatka, M.; Sjerps, M.; Vivo-Truyols, G.; Schoenmakers, P.; van Asten, A.

    2016-01-01

    In this study, the application of comprehensive two-dimensional (2D) gas chromatography (GC × GC) in forensic science is reviewed. The peer-reviewed publications on the forensic use of GC × GC and 2D gas chromatography with mass spectrometric detection (GC × GC-MS) have been studied in detail, not o

  5. Forensic potential of comprehensive two-dimensional gas chromatography

    NARCIS (Netherlands)

    Sampat, A.; Lopatka, M.; Sjerps, M.; Vivo-Truyols, G.; Schoenmakers, P.; van Asten, A.

    2016-01-01

    In this study, the application of comprehensive two-dimensional (2D) gas chromatography (GC × GC) in forensic science is reviewed. The peer-reviewed publications on the forensic use of GC × GC and 2D gas chromatography with mass spectrometric detection (GC × GC-MS) have been studied in detail, not o

  6. Zero sound in a two-dimensional dipolar Fermi gas

    NARCIS (Netherlands)

    Lu, Z.K.; Matveenko, S.I.; Shlyapnikov, G.V.

    2013-01-01

    We study zero sound in a weakly interacting two-dimensional (2D) gas of single-component fermionic dipoles (polar molecules or atoms with a large magnetic moment) tilted with respect to the plane of their translational motion. It is shown that the propagation of zero sound is provided by both mean-f

  7. Decoherence in a Landau Quantized Two Dimensional Electron Gas

    Directory of Open Access Journals (Sweden)

    McGill Stephen A.

    2013-03-01

    Full Text Available We have studied the dynamics of a high mobility two-dimensional electron gas as a function of temperature. The presence of satellite reflections in the sample and magnet can be modeled in the time-domain.

  8. Status for the two-dimensional Navier-Stokes solver EllipSys2D

    DEFF Research Database (Denmark)

    Bertagnolio, F.; Sørensen, Niels N.; Johansen, J.

    2001-01-01

    This report sets up an evaluation of the two-dimensional Navier-Stokes solver EllipSys2D in its present state. This code is used for blade aerodynamics simulations in the Aeroelastic Design group at Risø. Two airfoils are investigated by computing theflow at several angles of attack ranging from...... the linear to the stalled region. The computational data are compared to experimental data and numerical results from other computational codes. Several numerical aspects are studied, as mesh dependency,convective scheme, steady state versus unsteady computations, transition modelling. Some general...... conclusions intended to help in using this code for numerical simulations are given....

  9. Bill2d -- a software package for classical two-dimensional Hamiltonian systems

    CERN Document Server

    Solanpää, Janne; Räsänen, Esa

    2016-01-01

    We present Bill2d, a modern and efficient C++ package for classical simulations of two-dimensional Hamiltonian systems. Bill2d can be used for various billiard and diffusion problems with one or more charged particles with interactions, different external potentials, an external magnetic field, periodic and open boundaries, etc. The software package can also calculate many key quantities in complex systems such as Poincar\\'e sections, survival probabilities, and diffusion coefficients. While aiming at a large class of applicable systems, the code also strives for ease-of-use, efficiency, and modularity for the implementation of additional features. The package comes along with a user guide, a developer's manual, and a documentation of the application program interface (API).

  10. BILL2D - A software package for classical two-dimensional Hamiltonian systems

    Science.gov (United States)

    Solanpää, J.; Luukko, P. J. J.; Räsänen, E.

    2016-02-01

    We present BILL2D, a modern and efficient C++ package for classical simulations of two-dimensional Hamiltonian systems. BILL2D can be used for various billiard and diffusion problems with one or more charged particles with interactions, different external potentials, an external magnetic field, periodic and open boundaries, etc. The software package can also calculate many key quantities in complex systems such as Poincaré sections, survival probabilities, and diffusion coefficients. While aiming at a large class of applicable systems, the code also strives for ease-of-use, efficiency, and modularity for the implementation of additional features. The package comes along with a user guide, a developer's manual, and a documentation of the application program interface (API).

  11. Hysteretic Spin Crossover in Two-Dimensional (2D) Hofmann-Type Coordination Polymers.

    Science.gov (United States)

    Liu, Wei; Wang, Lu; Su, Yu-Jun; Chen, Yan-Cong; Tucek, Jiri; Zboril, Radek; Ni, Zhao-Ping; Tong, Ming-Liang

    2015-09-08

    Three new two-dimensional (2D) Hofmann-type coordination polymers with general formula [Fe(3-NH2py)2M(CN)4] (3-NH2py = 3-aminopyridine, M = Ni (1), Pd (2), Pt (3)) have been synthesized. Magnetic susceptibility measurements show that they exhibited cooperative spin crossover (SCO) with remarkable hysteretic behaviors. Their hysteresis widths are 25, 37, and 30 K for 1-3, respectively. The single-crystal structure of 1 suggest that the pseudo-octahedral Fe sites are equatorially bridged by [M(CN)4](2-) to form 2D grids and axially coordinated by 3-NH2py ligands. The intermolecular interactions between layers (the offset face-to-face π···π interactions, hydrogen bonds, and weak N(amino)···Ni(II) contacts) together with the covalent bonds bridged by [M(CN)4](2-) units are responsible to the significant cooperativity.

  12. Removal of interfering substances in samples prepared for two-dimensional (2-D) electrophoresis.

    Science.gov (United States)

    Berkelman, Tom

    2008-01-01

    Biological samples may contain contaminants that interfere with analysis by two-dimensional (2-D) electrophoresis. Lysates or biological fluids are complex mixtures that contain a wide variety of nonprotein substances in addition to the proteins to be analyzed. These substances often interfere with the resolution of the electrophoretic separation or the visualization of the result. Macromolecules (e.g., polysaccharides and DNA) can interfere with electrophoretic separation by clogging gel pores. Small ionic molecules can impair isoelectric focusing (IEF) separation by rendering the sample too conductive. Other substances (e.g., phenolics and lipids) can bind to proteins, influencing their electrophoretic properties or solubility. In many cases, measures to remove interfering substances can result in significantly clearer 2-D patterns with more visible spots and better resolution. It should be borne in mind, however, that analysis of samples by 2-D electrophoresis is usually most successful and informative when performed with minimally processed samples, so it is important that any steps taken to remove interfering substance be appropriate to the sample and only performed when necessary. Procedures for the removal of interfering substances therefore represent a compromise between removing nonprotein contaminants, and minimizing interference with the integrity and relative abundances of the sample proteins. This chapter presents a number of illustrative examples of optimized sample preparation methods in which specific interfering substances are removed by a variety of different strategies.

  13. Spin dynamics in a two-dimensional quantum gas

    DEFF Research Database (Denmark)

    Pedersen, Poul Lindholm; Gajdacz, Miroslav; Deuretzbacher, Frank

    2014-01-01

    We have investigated spin dynamics in a two-dimensional quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions with superimp......We have investigated spin dynamics in a two-dimensional quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions...

  14. Collective modes of a quasi-two-dimensional Bose condensate in large gas parameter regime

    Indian Academy of Sciences (India)

    S R Mishra; S P Ram; Arup Banerjee

    2007-06-01

    We have theoretically studied the collective modes of a quasi-two-dimensional (Q2D) Bose condensate in the large gas parameter regime by using a formalism which treats the interaction energy beyond the mean-field approximation. The results show that incorporation of this higher order term leads to significant modifications in the mode frequencies.

  15. Quantitative analysis of target components by comprehensive two-dimensional gas chromatography

    NARCIS (Netherlands)

    Mispelaar, V.G. van; Tas, A.C.; Smilde, A.K.; Schoenmakers, P.J.; Asten, A.C. van

    2003-01-01

    Quantitative analysis using comprehensive two-dimensional (2D) gas chromatography (GC) is still rarely reported. This is largely due to a lack of suitable software. The objective of the present study is to generate quantitative results from a large GC x GC data set, consisting of 32 chromatograms. I

  16. PRONTO 2D: A two-dimensional transient solid dynamics program

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, L.M.; Flanagan, D.P.

    1987-03-01

    PRONTO 2D is a two-dimensional transient solid dynamics code for analyzing large deformations of highly nonlinear materials subjected to extremely high strain rates. This Lagrangian finite element program uses an explicit time integration operator to integrate the equations of motion. Four node uniform strain quadrilateral elements are used in the finite element formulation. A number of new numerical algorithms which have been developed for the code are described in this report. An adaptive time step control algorithm is described which greatly improves stability as well as performance in plasticity problems. A robust hourglass control scheme which eliminates hourglass distortions without disturbing the finite element solution is included. All constitutive models in PRONTO are cast in an unrotated configuration defined using the rotation determined from the polar decomposition of the deformation gradient. An accurate incremental algorithm was developed to determine this rotation and is described in detail. A robust contact algorithm was developed which allows for the impact and interaction of deforming contact surfaces of quite general geometry. A number of numerical examples are presented to demonstrate the utility of these algorithms. 41 refs., 51 figs., 5 tabs.

  17. Gas sensing in 2D materials

    Science.gov (United States)

    Yang, Shengxue; Jiang, Chengbao; Wei, Su-huai

    2017-06-01

    Two-dimensional (2D) layered inorganic nanomaterials have attracted huge attention due to their unique electronic structures, as well as extraordinary physical and chemical properties for use in electronics, optoelectronics, spintronics, catalysts, energy generation and storage, and chemical sensors. Graphene and related layered inorganic analogues have shown great potential for gas-sensing applications because of their large specific surface areas and strong surface activities. This review aims to discuss the latest advancements in the 2D layered inorganic materials for gas sensors. We first elaborate the gas-sensing mechanisms and introduce various types of gas-sensing devices. Then, we describe the basic parameters and influence factors of the gas sensors to further enhance their performance. Moreover, we systematically present the current gas-sensing applications based on graphene, graphene oxide (GO), reduced graphene oxide (rGO), functionalized GO or rGO, transition metal dichalcogenides, layered III-VI semiconductors, layered metal oxides, phosphorene, hexagonal boron nitride, etc. Finally, we conclude the future prospects of these layered inorganic materials in gas-sensing applications.

  18. The two-dimensional alternative binary L-J system: liquid-gas phase diagram

    Institute of Scientific and Technical Information of China (English)

    张陟; 陈立溁

    2003-01-01

    A two-dimensional (2D) binary system without considering the Lennard-Jones (L-J) potential has been studied by using the Collins model. In this paper, we introduce the L-J potential into the 2D binary system and consider the existence of the holes that are called the "molecular fraction". The liquid-gas phase diagram of the 2D alternative binary L-J system is obtained. The results are quite analogous to the behaviour of 3D substances.

  19. Two-dimensional Fourier transform ESR in the slow-motional and rigid limits: 2D-ELDOR

    Science.gov (United States)

    Patyal, Baldev R.; Crepeau, Richard H.; Gamliel, Dan; Freed, Jack H.

    1990-12-01

    The two-dimensional Fourier transform ESP techniques of stimulated SECSY and 2D-ELDOR are shown to be powerful methods for the study of slow motions for nitroxides. Stimulated SECSY provides magnetization transfer rates, whereas 2D-ELDOR displays how the rotational motions spread the spins out from their initial spectral positions to new spectral positions, as a function of mixing time. The role of nuclear modulation in studies of structure and dynamics is also considered.

  20. MULTI2D - a computer code for two-dimensional radiation hydrodynamics

    Science.gov (United States)

    Ramis, R.; Meyer-ter-Vehn, J.; Ramírez, J.

    2009-06-01

    Simulation of radiation hydrodynamics in two spatial dimensions is developed, having in mind, in particular, target design for indirectly driven inertial confinement energy (IFE) and the interpretation of related experiments. Intense radiation pulses by laser or particle beams heat high-Z target configurations of different geometries and lead to a regime which is optically thick in some regions and optically thin in others. A diffusion description is inadequate in this situation. A new numerical code has been developed which describes hydrodynamics in two spatial dimensions (cylindrical R-Z geometry) and radiation transport along rays in three dimensions with the 4 π solid angle discretized in direction. Matter moves on a non-structured mesh composed of trilateral and quadrilateral elements. Radiation flux of a given direction enters on two (one) sides of a triangle and leaves on the opposite side(s) in proportion to the viewing angles depending on the geometry. This scheme allows to propagate sharply edged beams without ray tracing, though at the price of some lateral diffusion. The algorithm treats correctly both the optically thin and optically thick regimes. A symmetric semi-implicit (SSI) method is used to guarantee numerical stability. Program summaryProgram title: MULTI2D Catalogue identifier: AECV_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECV_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 151 098 No. of bytes in distributed program, including test data, etc.: 889 622 Distribution format: tar.gz Programming language: C Computer: PC (32 bits architecture) Operating system: Linux/Unix RAM: 2 Mbytes Word size: 32 bits Classification: 19.7 External routines: X-window standard library (libX11.so) and corresponding heading files (X11/*.h) are

  1. Optical properties of two-dimensional (2D) CdSe nanostructures

    Science.gov (United States)

    Cherevkov, S. A.; Baranov, A. V.; Fedorov, A. V.; Litvin, A. P.; Artemyev, M. V.; Prudnikau, A. V.

    2013-09-01

    The resonant and off-resonant Raman spectra of optical phonons in two-dimensional CdSe nanocrystals of 5, 6, and 7 monolayers are analysed. The spectra are dominated by SO and LO phonon bands of CdSe, whose frequencies are thickness-independent in the off-resonant Raman scattering but demonstrate an evident thickness dependence in the case of the resonant Raman scattering.

  2. Extension of the approximate two-dimensional electron gas formulation

    Science.gov (United States)

    Pierret, R. F.

    1985-07-01

    The functional two-dimensional electron gas (2DEG) formalism employed in the analysis of modulation-doped field-effect transistors is extended to properly account for the bulk charge and to more accurately model sub- and near-threshold behavior. The implemented changes basically transform the functional formulation from an above-threshold formalism for lightly doped structures to one of additional utility which automatically approaches expected limits under widely divergent conditions. Sample computations of the surface carrier concentration, relevant energy level positionings, and the semiconductor depletion width as a function of surface potential and doping are also presented and examined. These computations exhibit the general utility of the extended theory and provide an indirect evaluation of the standard two-level 2DEG theory.

  3. Polarons and molecules in a two-dimensional Fermi gas

    DEFF Research Database (Denmark)

    Zöllner, Sascha; Bruun, Georg Morten; Pethick, C. J.

    2011-01-01

    We study an impurity atom in a two-dimensional Fermi gas using variational wave functions for (i) an impurity dressed by particle-hole excitations (polaron) and (ii) a dimer consisting of the impurity and a majority atom. In contrast to three dimensions, where similar calculations predict a sharp...... transition to a dimer state with increasing interspecies attraction, we show that the polaron Ansatz always gives a lower energy. However, the exact solution for a heavy impurity reveals that both a two-body bound state and distortions of the Fermi sea are crucial. This reflects the importance of particle......-hole pairs in lower dimensions and makes simple variational calculations unreliable. We show that the energy of an impurity gives important information about its dressing cloud, for which both Ansätze give inaccurate results....

  4. Diffusion in the two-dimensional nonoverlapping Lorentz gas

    Science.gov (United States)

    James, Corinne P.; Evans, Glenn T.

    1987-10-01

    The self-diffusion coefficient, velocity autocorrelation function, and distribution of collision times for a two-dimensional nonoverlapping Lorentz gas were calculated using molecular dynamics simulation. The systems studied covered a range of densities, from a packing fraction (πNr2/L2) of 0.01 to 0.8. Self-diffusion coefficients were found to agree to all densities with kinetic theory predictions [A. Weijland and J. M. J. van Leeuwen, Physica 38, 35 (1968)] if the radial distribution function (rdf) was taken into account. The density dependence of the decay of the velocity autocorrelation function was qualitatively different from that predicted by kinetic theory. The distribution of collision times was nearly exponential for all but the highest density studied.

  5. Response Functions for the Two-Dimensional Ultracold Fermi Gas: Dynamical BCS Theory and Beyond

    Science.gov (United States)

    Vitali, Ettore; Shi, Hao; Qin, Mingpu; Zhang, Shiwei

    2017-08-01

    Response functions are central objects in physics. They provide crucial information about the behavior of physical systems, and they can be directly compared with scattering experiments involving particles such as neutrons or photons. Calculations of such functions starting from the many-body Hamiltonian of a physical system are challenging and extremely valuable. In this paper, we focus on the two-dimensional (2D) ultracold Fermi atomic gas which has been realized experimentally. We present an application of the dynamical BCS theory to obtain response functions for different regimes of interaction strengths in the 2D gas with zero-range attractive interaction. We also discuss auxiliary-field quantum Monte Carlo (AFQMC) methods for the calculation of imaginary time correlations in these dilute Fermi gas systems. Illustrative results are given and comparisons are made between AFQMC and dynamical BCS theory results to assess the accuracy of the latter.

  6. MARG2D code. 1. Eigenvalue problem for two dimensional Newcomb equation

    Energy Technology Data Exchange (ETDEWEB)

    Tokuda, Shinji [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment; Watanabe, Tomoko

    1997-10-01

    A new method and a code MARG2D have been developed to solve the 2-dimensional Newcomb equation which plays an important role in the magnetohydrodynamic (MHD) stability analysis in an axisymmetric toroidal plasma such as a tokamak. In the present formulation, an eigenvalue problem is posed for the 2-D Newcomb equation, where the weight function (the kinetic energy integral) and the boundary conditions at rational surfaces are chosen so that an eigenfunction correctly behaves as the linear combination of the small solution and the analytical solutions around each of the rational surfaces. Thus, the difficulty on solving the 2-D Newcomb equation has been resolved. By using the MARG2D code, the ideal MHD marginally stable state can be identified for a 2-D toroidal plasma. The code is indispensable on computing the outer-region matching data necessary for the resistive MHD stability analysis. Benchmark with ERATOJ, an ideal MHD stability code, has been carried out and the MARG2D code demonstrates that it indeed identifies both stable and marginally stable states against ideal MHD motion. (author)

  7. Quantum magnetotransport in a modulated two-dimensional electron gas

    Science.gov (United States)

    Park, Tae-ik; Gumbs, Godfrey

    1997-09-01

    Quantum mechanical calculations of the magnetotransport coefficients of a modulated two-dimensional electron gas in a perpendicular magnetic field are presented using the Kubo method. The model modulation potential used is such that the effect of the steepness of the potential and its strength on the band part of the longitudinal resistivity ρxxand the Hall resistivity ρxycould be studied. In the extreme limit of a very steep potential, a two-dimensional square array of antidots is simulated. Impurity scattering is included in the self-consistent t-matrix approximation. The results show that for a strong lateral superlattice potential, ρxyis quenched in the low magnetic field regime and as the magnetic field increases there is a large negative Hall resistivity. The intensity of this negative peak is suppressed as the strength of the modulation potential is decreased. It is also shown that the height of the negative peak depends on the steepness of the potential. The longitudinal resistivity also has some interesting features. There are Aharonov-Bohm oscillations and a double peak structure which depends on both the strength of the modulation potential as well as its slope. The numerical results show that the position and intensity of the lower peak is not very sensitive to a change in the strength of the lattice potential or its steepness. However, the upper peak is greatly reduced when the lattice potential is diminished in strength. The double peak feature in ρxxand the negative peak and quenching of the Hall effect at low magnetic fields have been observed experimentally for antidots in both the quasiclassical and quantum regimes.

  8. Phase correlations and quasicondensate in a two-dimensional ultracold Fermi gas

    Energy Technology Data Exchange (ETDEWEB)

    Tempere, J., E-mail: jacques.tempere@uantwerpen.be [Theory of Quantum and Complex Systems, Universiteit Antwerpen, Universiteitsplein 1, B-2610 Antwerpen (Belgium); Lyman Laboratory of Physics, Harvard University, Cambridge, MA 02138 (United States); Klimin, S.N. [Theory of Quantum and Complex Systems, Universiteit Antwerpen, Universiteitsplein 1, B-2610 Antwerpen (Belgium)

    2015-02-15

    The interplay between dimensionality, coherence and interaction in superfluid Fermi gases is analyzed by the phase correlation function of the field of fermionic pairs. We calculate this phase correlation function for a two-dimensional superfluid Fermi gas with s-wave interactions within the Gaussian pair fluctuation formalism. The spatial behavior of the correlation function is shown to exhibit a rapid (exponential) decay at short distances and a characteristic algebraic decay at large distances, with an exponent matching that expected from the Berezinskii–Kosterlitz–Thouless theory of 2D Bose superfluids. We conclude that the Gaussian pair fluctuation approximation is able to capture the physics of quasi-long-range order in two-dimensional Fermi gases. - Highlights: • The phase correlation functions for an ultracold Fermi gas in 2D are calculated. • The decay of the correlation functions is algebraic at long distances. • The Gaussian pair fluctuation approach is shown to capture the quasicondensate physics in 2D Fermi gases.

  9. Synchronous two-dimensional MIR correlation spectroscopy (2D-COS) as a novel method for screening smoke tainted wine.

    Science.gov (United States)

    Fudge, Anthea L; Wilkinson, Kerry L; Ristic, Renata; Cozzolino, Daniel

    2013-08-15

    In this study, two-dimensional correlation spectroscopy (2D-COS) combined with mid-infrared (MIR) spectroscopy was evaluated as a novel technique for the identification of spectral regions associated with smoke-affected wine, for the purpose of screening taint arising from grapevine exposure to smoke. Smoke-affected wines obtained from experimental and industry sources were analysed using MIR spectroscopy and chemometrics, and calibration models developed. 2D-COS analysis was used to generate synchronous data maps for red and white cask wines spiked with guaiacol, a marker of smoke taint. Correlations were observed at wavelengths that could be attributable to aromatic C-C stretching, i.e., between 1400 and 1500 cm(-1), indicative of volatile phenols. These results demonstrate the potential of 2D-COS as a rapid, high-throughput technique for the preliminary screening of smoke tainted wine.

  10. Bubble dynamics in a two-dimensional gas-solid fluidized bed

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Related referential studies on gas-solid two-phase flows were briefly reviewed. Bubble ascending in a two-dimensional (2D) gas-solid fluidized bed was studied both experimentally and numerically. A modified continuum model expressed in the conservation form was used in numerical simulation. Solid-phase pressure was modeled via local sound speed; gas-phase turbulence was described by the K-ε two-equation model. The modified implicit multiphase formulation (IMF) scheme was used to solve the model equations in 2D Cartesian/cylindrical coordinates. The bubble ascending velocity and particle motion in the 2D fluidized bed were measured using the photochromic dye activation (PDA) technique, which was based on UV light activation of particles impregnated with the dye. Effects of bed height and superficial gas velocity on bubble formation and ascent were investigated numerically. The numerically obtained bubble ascending velocities were compared with experimental measurements. Gas bubble in jetting gas-solids fluidized bed was also simulated numerically.

  11. Optical theorem for two-dimensional (2D) scalar monochromatic acoustical beams in cylindrical coordinates.

    Science.gov (United States)

    Mitri, F G

    2015-09-01

    The optical theorem for plane waves is recognized as one of the fundamental theorems in optical, acoustical and quantum wave scattering theory as it relates the extinction cross-section to the forward scattering complex amplitude function. Here, the optical theorem is extended and generalized in a cylindrical coordinates system for the case of 2D beams of arbitrary character as opposed to plane waves of infinite extent. The case of scalar monochromatic acoustical wavefronts is considered, and generalized analytical expressions for the extinction, absorption and scattering cross-sections are derived and extended in the framework of the scalar resonance scattering theory. The analysis reveals the presence of an interference scattering cross-section term describing the interaction between the diffracted Franz waves with the resonance elastic waves. The extended optical theorem in cylindrical coordinates is applicable to any object of arbitrary geometry in 2D located arbitrarily in the beam's path. Related investigations in optics, acoustics and quantum mechanics will benefit from this analysis in the context of wave scattering theory and other phenomena closely connected to it, such as the multiple scattering by a cloud of particles, as well as the resulting radiation force and torque.

  12. Quantum holographic encoding in a two-dimensional electron gas

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Christopher

    2010-05-26

    The advent of bottom-up atomic manipulation heralded a new horizon for attainable information density, as it allowed a bit of information to be represented by a single atom. The discrete spacing between atoms in condensed matter has thus set a rigid limit on the maximum possible information density. While modern technologies are still far from this scale, all theoretical downscaling of devices terminates at this spatial limit. Here, however, we break this barrier with electronic quantum encoding scaled to subatomic densities. We use atomic manipulation to first construct open nanostructures - 'molecular holograms' - which in turn concentrate information into a medium free of lattice constraints: the quantum states of a two-dimensional degenerate Fermi gas of electrons. The information embedded in the holograms is transcoded at even smaller length scales into an atomically uniform area of a copper surface, where it is densely projected into both two spatial degrees of freedom and a third holographic dimension mapped to energy. In analogy to optical volume holography, this requires precise amplitude and phase engineering of electron wavefunctions to assemble pages of information volumetrically. This data is read out by mapping the energy-resolved electron density of states with a scanning tunnelling microscope. As the projection and readout are both extremely near-field, and because we use native quantum states rather than an external beam, we are not limited by lensing or collimation and can create electronically projected objects with features as small as {approx}0.3 nm. These techniques reach unprecedented densities exceeding 20 bits/nm{sup 2} and place tens of bits into a single fermionic state.

  13. Two-dimensional crystal melting and D4-D2-D0 on toric Calabi-Yau singularities

    CERN Document Server

    Nishinaka, Takahiro; Yoshida, Yutaka

    2013-01-01

    We construct a two-dimensional crystal melting model which reproduces the BPS index of D2-D0 states bound to a non-compact D4-brane on an arbitrary toric Calabi-Yau singularity. The crystalline structure depends on the toric divisor wrapped by the D4-brane. The molten crystals are in one-to-one correspondence with the torus fixed points of the moduli space of the quiver gauge theory on D-branes. The F- and D-term constraints of the gauge theory are regarded as a generalization of the ADHM constraints on instantons. We also show in several examples that our model is consistent with the wall-crossing formula for the BPS index.

  14. Noble gas adsorption in two-dimensional zeolites: a combined experimental and density functional theory study

    Science.gov (United States)

    Wang, Mengen; Zhong, Jianqiang; Boscoboinik, Jorge Anibal; Lu, Deyu

    Zeolites are important industrial catalysts with porous three-dimensional structures. The catalytically active sites are located inside the pores, thus rendering them inaccessible for surface science measurements. We synthesized a two-dimensional (2D) zeolite model system, consisting of an (alumino)silicate bilayer weakly bound to a Ru (0001) surface. The 2D zeolite is suitable for surface science studies; it allows a detailed characterization of the atomic structure of the active site and interrogation of the model system during the catalytic reaction. As an initial step, we use Ar adsorption to obtain a better understanding of the atomic structure of the 2D zeolite. In addition, atomic level studies of rare gas adsorption and separation by zeolite are important for its potential application in nuclear waste sequestration. Experimental studies found that Ar atoms can be trapped inside the 2D-zeolite, raising an interesting question on whether Ar atoms are trapped inside the hexagonal prism nano-cages or at the interface between the (alumino)silicate bilayer and Ru(0001), or both. DFT calculations using van der Waals density functionals were carried out to determine the preferred Ar adsorption sites and the corresponding adsorption energies. This research used resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704.

  15. Current-injection in a ballastic multiterminal superconductor/two-dimensional electron gas Josephson junction

    NARCIS (Netherlands)

    Schäpers, Th.; Guzenko, V.A.; Müller, R.P.; Golubov, A.A.; Brinkman, A.; Crecelius, G.; Kaluza, A.; Lüth, H.

    2003-01-01

    We study the suppression of the critical current in a multi-terminal superconductor/two-dimensional electron gas/superconductor Josephson junction by means of hot carrier injection. As a superconductor Nb is used, while the two-dimensional electron gas is located in a strained InGaAs/InP heterostruc

  16. Two-dimensional gas of massless Dirac fermions in graphene.

    Science.gov (United States)

    Novoselov, K S; Geim, A K; Morozov, S V; Jiang, D; Katsnelson, M I; Grigorieva, I V; Dubonos, S V; Firsov, A A

    2005-11-10

    Quantum electrodynamics (resulting from the merger of quantum mechanics and relativity theory) has provided a clear understanding of phenomena ranging from particle physics to cosmology and from astrophysics to quantum chemistry. The ideas underlying quantum electrodynamics also influence the theory of condensed matter, but quantum relativistic effects are usually minute in the known experimental systems that can be described accurately by the non-relativistic Schrödinger equation. Here we report an experimental study of a condensed-matter system (graphene, a single atomic layer of carbon) in which electron transport is essentially governed by Dirac's (relativistic) equation. The charge carriers in graphene mimic relativistic particles with zero rest mass and have an effective 'speed of light' c* approximately 10(6) m s(-1). Our study reveals a variety of unusual phenomena that are characteristic of two-dimensional Dirac fermions. In particular we have observed the following: first, graphene's conductivity never falls below a minimum value corresponding to the quantum unit of conductance, even when concentrations of charge carriers tend to zero; second, the integer quantum Hall effect in graphene is anomalous in that it occurs at half-integer filling factors; and third, the cyclotron mass m(c) of massless carriers in graphene is described by E = m(c)c*2. This two-dimensional system is not only interesting in itself but also allows access to the subtle and rich physics of quantum electrodynamics in a bench-top experiment.

  17. FireStem2D--a two-dimensional heat transfer model for simulating tree stem injury in fires.

    Directory of Open Access Journals (Sweden)

    Efthalia K Chatziefstratiou

    Full Text Available FireStem2D, a software tool for predicting tree stem heating and injury in forest fires, is a physically-based, two-dimensional model of stem thermodynamics that results from heating at the bark surface. It builds on an earlier one-dimensional model (FireStem and provides improved capabilities for predicting fire-induced mortality and injury before a fire occurs by resolving stem moisture loss, temperatures through the stem, degree of bark charring, and necrotic depth around the stem. We present the results of numerical parameterization and model evaluation experiments for FireStem2D that simulate laboratory stem-heating experiments of 52 tree sections from 25 trees. We also conducted a set of virtual sensitivity analysis experiments to test the effects of unevenness of heating around the stem and with aboveground height using data from two studies: a low-intensity surface fire and a more intense crown fire. The model allows for improved understanding and prediction of the effects of wildland fire on injury and mortality of trees of different species and sizes.

  18. Pressure Tuning of First Dimension Columns in Comprehensive Two-Dimensional Gas Chromatography.

    Science.gov (United States)

    Sharif, Khan M; Kulsing, Chadin; Marriott, Philip J

    2016-09-20

    The experimental approach and mechanism of pressure tuning (PT) are introduced for the first stage of a comprehensive two-dimensional gas chromatography (GC × GC) separation. The PT-GC × GC system incorporates a first dimension ((1)D) coupled column ensemble comprising a pair of (1)D columns ((1)D1 and (1)D2) connected via a microfluidic splitter device, allowing variable decompression of carrier gas across each (1)D column, and a conventional (2)D narrow bore column. By variation of junction pressure between the (1)D1 and (1)D2 columns, tunable total (1)D retentions of analytes are readily derived. Separations of a standard mixture comprising a number of different chemical classes (including alkanes, monoaromatics, alcohols, aldehydes, ketones, and esters) and Australian tea tree oil (TTO) were studied as practical examples of the PT-GC × GC system application. This illustrated the change of analyte retention time with experimental conditions depending on void time and retention on the different columns. In addition to void time change, variation of carrier gas relative decompression in the (1)D ensemble leads to tunable contribution of the (1)D1/(1)D2 columns that changes apparent polarity and selectivity of the ensemble. The resulting changes in (1)D elution order further altered elution temperature and thus retention of each analyte on the (2)D column in temperature-programmed GC × GC. 2D orthogonality measurements were then conducted to evaluate overall separation performance under application of different (1)D junction pressure. As a result, distribution and selectivity of particular target compounds, monoterpenes, sesquiterpenes, and oxygenated terpenes in 2D space, and thus orthogonality, could be adequately tuned. This indicates the potential of PT-GC × GC to be applicable for practical sample separation and provides a general approach to tune selectivity of target compounds.

  19. Fermi liquid-to-Bose condensate crossover in a two-dimensional ultracold gas experiment

    Science.gov (United States)

    Barmashova, T. V.; Mart'yanov, K. A.; Makhalov, V. B.; Turlapov, A. V.

    2016-02-01

    By controling interparticle interactions, it is possible to transform a fermionic system into a bosonic system and vice versa, while preserving quantum degeneracy. Evidence of such a transformation may be found by monitoring the pressure and interference. The Fermi pressure is an indication of the fermion?ic character of a system, while the interference implies a nonzero order parameter and Bose condensation. Lowering from three to two spatial dimensions introduces new physics and makes the system more difficult to describe due to the increased fluctuations and the reduced applicability of mean field methods. An experiment with a two-dimensional ultracold atomic gas shows a crossover between the Bose and Fermi limits, as evident from the value of pressure and from the interference pattern, and provides data to test models of 2D Fermi and Bose systems, including the most-difficult-to-model strongly coupled systems.

  20. WSJointInv2D-MT-DCR: An efficient joint two-dimensional magnetotelluric and direct current resistivity inversion

    Science.gov (United States)

    Amatyakul, Puwis; Vachiratienchai, Chatchai; Siripunvaraporn, Weerachai

    2017-05-01

    An efficient joint two-dimensional direct current resistivity (DCR) and magnetotelluric (MT) inversion, referred to as WSJointInv2D-MT-DCR, was developed with FORTRAN 95 based on the data space Occam's inversion algorithm. Our joint inversion software can be used to invert just the MT data or the DCR data, or invert both data sets simultaneously to get the electrical resistivity structures. Since both MT and DCR surveys yield the same resistivity structures, the two data types enhance each other leading to a better interpretation. Two synthetic and a real field survey are used here to demonstrate that the joint DCR and MT surveys can help constrain each other to reduce the ambiguities occurring when inverting the DCR or MT alone. The DCR data increases the lateral resolution of the near surface structures while the MT data reveals the deeper structures. When the MT apparent resistivity suffers from the static shift, the DCR apparent resistivity can serve as a replacement for the estimation of the static shift factor using the joint inversion. In addition, we also used these examples to show the efficiency of our joint inversion code. With the availability of our new joint inversion software, we expect the number of joint DCR and MT surveys to increase in the future.

  1. Second-Order Phase Transition in the Two-Dimensional Classical Lattice Coulomb Gas of Half-Integer Charges

    Institute of Scientific and Technical Information of China (English)

    罗孟波; 陈庆虎; 许祝安; 焦正宽

    2001-01-01

    The second-order phase transition in the two-dimensional (2D) classical Coulomb gas of half-integer charges on a square lattice is investigated by using Monte Carlo simulations. Based on the finite-size scaling analysis,we estimate the second-order phase transition temperature Tc and the static critical exponents β and v with a new numerical analysis method. More precise critical temperature Tc = 0.1311(2) and critical exponents β/ν = 0.1152(12) and ν = 0.857(15) are obtained. The estimated value of ν indicates that the charge lattice melting transition is different from the pure 2D Ising transition.

  2. Theory of a Nearly Two-Dimensional Dipolar Bose Gas

    Science.gov (United States)

    2016-05-11

    optical data storage, and quantum computing. Today , BECs can be made with a variety of atomic species, including Chromium (Cr) [8] and the rare-earth...out many of these experiments. However, the experi- ments involved atoms that possess negligible dipole moments (like the alkali atoms ). Today , there...gases of bosonic atoms at ultracold, but finite temperatures. Under these circumstances, the gas can undergo a phase transition to a purely quantum

  3. Dipolar quantum electrodynamics of the two-dimensional electron gas

    Science.gov (United States)

    Todorov, Yanko

    2015-03-01

    Similarly to a previous work on the homogeneous electron gas [Y. Todorov, Phys. Rev. B 89, 075115 (2014), 10.1103/PhysRevB.89.075115], we apply the Power-Zienau-Wooley (PZW) formulation of the quantum electrodynamics to the case of an electron gas quantum confined by one-dimensional potential. We provide a microscopic description of all collective plasmon modes of the gas, oscillating both along and perpendicular to the direction of quantum confinement. Furthermore, we study the interaction of the collective modes with a photonic structure, planar metallic waveguide, by using the full expansion of the electromagnetic field into normal modes. We show how the boundary conditions for the electromagnetic field influence both the transverse light-matter coupling and the longitudinal particle-particle interactions. The PZW descriptions appear thus as a convenient tool to study semiconductor quantum optics in geometries where quantum-confined particles interact with strongly confined electromagnetic fields in microresonators, such as the ones used to achieve the ultrastrong light-matter coupling regime.

  4. Superfluidity and relaxation dynamics of a laser-stirred two-dimensional Bose gas

    Science.gov (United States)

    Singh, Vijay Pal; Weitenberg, Christof; Dalibard, Jean; Mathey, Ludwig

    2017-04-01

    We investigate the superfluid behavior of a two-dimensional (2D) Bose gas of 87Rb atoms using classical field dynamics. In the experiment by R. Desbuquois et al. [Nat. Phys. 8, 645 (2012), 10.1038/nphys2378], a 2D quasicondensate in a trap is stirred with a blue-detuned laser beam along a circular path around the trap center. Here, we study this experiment from a theoretical perspective. The heating induced by stirring increases rapidly above a velocity vc, which we define as the critical velocity. We identify the superfluid, the crossover, and the thermal regime by a finite, a sharply decreasing, and a vanishing critical velocity, respectively. We demonstrate that the onset of heating occurs due to the creation of vortex-antivortex pairs. A direct comparison of our numerical results to the experimental ones shows a good agreement, if a systematic shift of the critical phase-space density is included. We relate this shift to the absence of thermal equilibrium between the condensate and the thermal wings, which were used in the experiment to extract the temperature. We expand on this observation by studying the full relaxation dynamics between the condensate and the thermal cloud.

  5. Screening phase transitions in two-dimensional Coulomb gas

    Energy Technology Data Exchange (ETDEWEB)

    Gallavotti, G.; Nicolo, F.

    1984-07-01

    Infrared properties of a Coulomb gas in two dimensions and with fixed ultraviolet cutoff are studied. The existence of infinitely many thresholds Tu = 1/Ke 1/8 pi (1-1/zu)sup-1 in the interval of temperatures 1/Ke1/8 pi, 1/4 pi, where K is the Boltzmann constant and e = /e/ is the charge of the positive particle, is proved. Such thresholds are conjectured to reflect a sequence of transitions from a pure multipole phase (the Koesterlitz-Thouless region) to the plasma phase via an infinite number of intermediate phases. Mathematically the free energy becomes more and more differentiable as a function of the activity lambda, near lambda = 0, as the temperature decreases.

  6. User's Guide for ECAP2D: an Euler Unsteady Aerodynamic and Aeroelastic Analysis Program for Two Dimensional Oscillating Cascades, Version 1.0

    Science.gov (United States)

    Reddy, T. S. R.

    1995-01-01

    This guide describes the input data required for using ECAP2D (Euler Cascade Aeroelastic Program-Two Dimensional). ECAP2D can be used for steady or unsteady aerodynamic and aeroelastic analysis of two dimensional cascades. Euler equations are used to obtain aerodynamic forces. The structural dynamic equations are written for a rigid typical section undergoing pitching (torsion) and plunging (bending) motion. The solution methods include harmonic oscillation method, influence coefficient method, pulse response method, and time integration method. For harmonic oscillation method, example inputs and outputs are provided for pitching motion and plunging motion. For the rest of the methods, input and output for pitching motion only are given.

  7. Ferroelectric control of two dimensional electron gas in oxide heterointerface

    Science.gov (United States)

    Thanh, Tra Vu; Chen, Jhih-Wei; Yeh, Chao-Hui; Chen, Yi-Chun; Wu, Chung-Lin; Lin, Jiunn Yuan; Chu, Ying-Hao

    2012-02-01

    Oxide heterointerfaces are emerging as one of the most exciting materials systems in condensed-matter science. One remarkable example is the LaAlO3 /SrTiO3 (LAO/STO) interface, a model system in which a highly mobile electron gas forms between two band insulators. Our study to manipulate the conductivity at this interface by using ferroeletricity of Pb(Zr,Ti)O3. Our transport data strongly suggests that down polarization direction depletes the conducting interface of LAO/STO. After switching the polarization direction (up), it becomes accumulation. In addition, our experiments show there is obvious the band structure changed by cross-sectional scanning tunneling microscopy and combining with X-ray photoelectron spectroscopy (XPS) measurements. The transport properties are measured to build up the connection between macroscopic properties and local electronic structures that have been applied to study this structure. Controlling the conductivity of this oxide interface suggests that this technique may not only extend more generally to other oxide systems but also open much potential to ferroelectric field effect transistors.

  8. High-temperature two-dimensional gas chromatography of hydrocarbons up to nC60 for analysis of vacuum gas oils.

    Science.gov (United States)

    Dutriez, Thomas; Courtiade, Marion; Thiébaut, Didier; Dulot, Hugues; Bertoncini, Fabrice; Vial, Jérôme; Hennion, Marie-Claire

    2009-04-03

    In a tense energetic context, the characterization of heavy petroleum fractions becomes essential. Conventional comprehensive two-dimensional gas chromatography (2D-GC or GCxGC) is widely used for middle distillates analysis, but only a few applications are devoted to these heavier fractions. In this paper, it is shown how the optimization of GCxGC separation allowed the determination of suitable high-temperature (HT) conditions, adjusting column properties and operating conditions. 2D separations were evaluated using 2D separation criteria and a new concept of 2D asymmetry (As(2D)). New HT conditions allowed the extension of GCxGC range of applications to heavier hydrocarbons, up to nC(60). A first application of high-temperature two-dimensional gas chromatography (HT-2D-GC) to a full vacuum gas oil (VGO) feed stock is described. Comparisons with other standardized methods illustrate the high potential of HT-2D-GC for heavy fractions analysis.

  9. Bouncing, rolling, energy flows, and cluster formation in a two-dimensional vibrated granular gas

    Science.gov (United States)

    Pérez-Ángel, Gabriel; Nahmad-Molinari, Yuri

    2011-10-01

    We study the formation of crystalline clusters for a two-dimensional (2D) sinusoidally vibrated granular gas, with maximum vertical acceleration smaller than gravity, using fully 3D simulations. It is found that this phenomenon arises from the spontaneous segregation of the granulate into two dynamical modes: one of grains that bounce in synchrony with the motion of the sustaining plate (“bouncers”) and another of grains that cease to bounce and simply rolls on the plate, without ever loosing contact with it (“rollers”). These two dynamical categories are quite robust with respect to perturbations. The populations for bouncers and rollers depend on the preparation of the granulate and can be made to take arbitrary values in all the range of accelerations where both dynamical modes are present. It is found that the dynamical mode with the largest population coalesces in clusters under the influence of the other mode, whose grains act as a higher pressure gas that compresses the clusters. In this way it is possible to produce clusters of rollers or clusters of bouncers. A gas made of grains from only one dynamical class shows only weak density fluctuations. When the occupation fractions for both modes are similar, one observes segregation and clusters of both types. The clustering of the gas is monitored using both the average coordination number and the local hexatic order parameter ψ6. Energy flows in the plane are monitored, and it is shown that roller-bouncer collisions increase horizontal kinetic energy, while all other types of collisions reduce this energy. We find that friction with the substrate is the main sink of horizontal energy for these granular gases.

  10. Noise reduction methods applied to two-dimensional correlation spectroscopy (2D-COS) reveal complementary benefits of pre- and post-treatment.

    Science.gov (United States)

    Foist, Rod B; Schulze, H Georg; Ivanov, Andre; Turner, Robin F B

    2011-05-01

    Two-dimensional correlation spectroscopy (2D-COS) is a powerful spectral analysis technique widely used in many fields of spectroscopy because it can reveal spectral information in complex systems that is not readily evident in the original spectral data alone. However, noise may severely distort the information and thus limit the technique's usefulness. Consequently, noise reduction is often performed before implementing 2D-COS. In general, this is implemented using one-dimensional (1D) methods applied to the individual input spectra, but, because 2D-COS is based on sets of successive spectra and produces 2D outputs, there is also scope for the utilization of 2D noise-reduction methods. Furthermore, 2D noise reduction can be applied either to the original set of spectra before performing 2D-COS ("pretreatment") or on the 2D-COS output ("post-treatment"). Very little work has been done on post-treatment; hence, the relative advantages of these two approaches are unclear. In this work we compare the noise-reduction performance on 2D-COS of pretreatment and post-treatment using 1D (wavelets) and 2D algorithms (wavelets, matrix maximum entropy). The 2D methods generally outperformed the 1D method in pretreatment noise reduction. 2D post-treatment in some cases was superior to pretreatment and, unexpectedly, also provided correlation coefficient maps that were similar to 2D correlation spectroscopy maps but with apparent better contrast.

  11. Comprehensive two-dimensional gas chromatographic separations with a temperature programmed microfabricated thermal modulator.

    Science.gov (United States)

    Collin, William R; Nuñovero, Nicolas; Paul, Dibyadeep; Kurabayashi, Katsuo; Zellers, Edward T

    2016-04-29

    Comprehensive two-dimensional gas chromatography (GC×GC) with a temperature-programmed microfabricated thermal modulator (μTM) is demonstrated. The 0.78 cm(2), 2-stage μTM chip with integrated heaters and a PDMS coated microchannel was placed in thermal contact with a solid-state thermoelectric cooler and mounted on top of a bench scale GC. It was fluidically coupled through heated interconnects to an upstream first-dimension ((1)D) PDMS-coated capillary column and a downstream uncoated capillary or second-dimension ((2)D) PEG-coated capillary. A mixture of n-alkanes C6-C10 was separated isothermally and the full-width-at-half-maximum (fwhm) values of the modulated peaks were assessed as a function of the computer-controlled minimum and maximum stage temperatures of μTM, Tmin and Tmax, respectively. With Tmin and Tmax fixed at -25 and 100°C, respectively, modulated peaks of C6 and C7 had fwhm valuesthermal modulator. Replacing the PDMS phase in the μTM with a trigonal-tricationic room temperature ionic liquid eliminated the bleed observed with the PDMS, but also reduced the capacity for several test compounds. Regardless, the demonstrated capability to independently temperature program this low resource μTM enhances its versatility and its promise for use in bench-scale GC×GC systems.

  12. Smart multi-channel two-dimensional micro-gas chromatography for rapid workplace hazardous volatile organic compounds measurement.

    Science.gov (United States)

    Liu, Jing; Seo, Jung Hwan; Li, Yubo; Chen, Di; Kurabayashi, Katsuo; Fan, Xudong

    2013-03-07

    We developed a novel smart multi-channel two-dimensional (2-D) micro-gas chromatography (μGC) architecture that shows promise to significantly improve 2-D μGC performance. In the smart μGC design, a non-destructive on-column gas detector and a flow routing system are installed between the first dimensional separation column and multiple second dimensional separation columns. The effluent from the first dimensional column is monitored in real-time and decision is then made to route the effluent to one of the second dimensional columns for further separation. As compared to the conventional 2-D μGC, the greatest benefit of the smart multi-channel 2-D μGC architecture is the enhanced separation capability of the second dimensional column and hence the overall 2-D GC performance. All the second dimensional columns are independent of each other, and their coating, length, flow rate and temperature can be customized for best separation results. In particular, there is no more constraint on the upper limit of the second dimensional column length and separation time in our architecture. Such flexibility is critical when long second dimensional separation is needed for optimal gas analysis. In addition, the smart μGC is advantageous in terms of elimination of the power intensive thermal modulator, higher peak amplitude enhancement, simplified 2-D chromatogram re-construction and potential scalability to higher dimensional separation. In this paper, we first constructed a complete smart 1 × 2 channel 2-D μGC system, along with an algorithm for automated control/operation of the system. We then characterized and optimized this μGC system, and finally employed it in two important applications that highlight its uniqueness and advantages, i.e., analysis of 31 workplace hazardous volatile organic compounds, and rapid detection and identification of target gas analytes from interference background.

  13. Exact two-body solutions and quantum defect theory of two-dimensional dipolar quantum gas

    Science.gov (United States)

    Jie, Jianwen; Qi, Ran

    2016-10-01

    In this paper, we provide the two-body exact solutions of the two-dimensional (2D) Schrödinger equation with isotropic +/- 1/{r}3 interactions. An analytic quantum defect theory is constructed based on these solutions and it is applied to investigate the scattering properties as well as two-body bound states of an ultracold polar molecules confined in a quasi-2D geometry. Interestingly, we find that for the attractive case, the scattering resonance happens simultaneously in all partial waves, which has not been observed in other systems. The effect of this feature on the scattering phase shift across such resonances is also illustrated.

  14. Direct Measurement of the Band Structure of a Buried Two-Dimensional Electron Gas

    DEFF Research Database (Denmark)

    Miwa, Jill; Hofmann, Philip; Simmons, Michelle Y.;

    2013-01-01

    We directly measure the band structure of a buried two dimensional electron gas (2DEG) using angle resolved photoemission spectroscopy. The buried 2DEG forms 2 nm beneath the surface of p-type silicon, because of a dense delta-type layer of phosphorus n-type dopants which have been placed there. ...

  15. Model for ballistic spin-transport in ferromagnet/two-dimensional electron gas/ferromagnet structures

    NARCIS (Netherlands)

    Schapers, T; Nitta, J; Heersche, HB; Takayanagi, H

    2002-01-01

    The spin dependent conductance of a ferromagnet/two-dimensional electron gas ferromagnet structure is theoretically examined in the ballistic transport regime. It is shown that the spin signal can be improved considerably by making use of the spin filtering effect of a barrier at the ferromagnet two

  16. Tunable secondary dimension selectivity in comprehensive two-dimensional gas chromatography

    NARCIS (Netherlands)

    J. Mommers; G. Pluimakers; J. Knooren; T. Dutriez; S. van der Wal

    2013-01-01

    In this paper two tunable two-dimensional gas chromatography setups are compared and described in which the secondary dimension consists of two different capillary columns coupled in series. In the first setup the selectivity of the second dimension can be tuned by adjusting the effective column len

  17. Comprehensive two-dimensional gas chromatography for the analysis of organohalogenated micro-contaminants

    NARCIS (Netherlands)

    Korytar, P.; Haglund, P.; Boer, de J.; Brinkman, U.A.Th.

    2006-01-01

    We explain the principles of comprehensive two-dimensional gas chromatography (GC × GC), and discuss key instrumental aspects - with emphasis on column combinations and mass spectrometric detection. As the main item of interest, we review the potential of GC × GC for the analysis of organohalogenate

  18. Lattice gas dynamics: application to driven vortices in two dimensional superconductors.

    Science.gov (United States)

    Gotcheva, Violeta; Wang, Albert T J; Teitel, S

    2004-06-18

    A continuous time Monte Carlo lattice gas dynamics is developed to model driven steady states of vortices in two dimensional superconducting networks. Dramatic differences are found when compared to a simpler Metropolis dynamics. Subtle finite size effects are found at low temperature, with a moving smectic that becomes unstable to an anisotropic liquid on sufficiently large length scales.

  19. Spin and charge transport in a gated two dimensional electron gas

    NARCIS (Netherlands)

    Lerescu, Alexandru Ionut

    2007-01-01

    The work presented in this thesis is centered around the idea of how one can inject, transport and detect the electron's spin in a two dimensional electron gas (a semiconductor heterostructure). Metal based spintronic devices have been established to be the easy way to implement spintronic concepts

  20. Model of two-dimensional electron gas formation at ferroelectric interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Aguado-Puente, P.; Bristowe, N. C.; Yin, B.; Shirasawa, R.; Ghosez, Philippe; Littlewood, P. B.; Artacho, Emilio

    2015-07-01

    The formation of a two-dimensional electron gas at oxide interfaces as a consequence of polar discontinuities has generated an enormous amount of activity due to the variety of interesting effects it gives rise to. Here, we study under what circumstances similar processes can also take place underneath ferroelectric thin films. We use a simple Landau model to demonstrate that in the absence of extrinsic screening mechanisms, a monodomain phase can be stabilized in ferroelectric films by means of an electronic reconstruction. Unlike in the LaAlO3/SrTiO3 heterostructure, the emergence with thickness of the free charge at the interface is discontinuous. This prediction is confirmed by performing first-principles simulations of free-standing slabs of PbTiO3. The model is also used to predict the response of the system to an applied electric field, demonstrating that the two-dimensional electron gas can be switched on and off discontinuously and in a nonvolatile fashion. Furthermore, the reversal of the polarization can be used to switch between a two-dimensional electron gas and a two-dimensional hole gas, which should, in principle, have very different transport properties. We discuss the possible formation of polarization domains and how such configuration competes with the spontaneous accumulation of free charge at the interfaces.

  1. Comprehensive two-dimensional gas chromatography for the analysis of organohalogenated micro-contaminants

    NARCIS (Netherlands)

    Korytar, P.; Haglund, P.; Boer, de J.; Brinkman, U.A.Th.

    2006-01-01

    We explain the principles of comprehensive two-dimensional gas chromatography (GC × GC), and discuss key instrumental aspects - with emphasis on column combinations and mass spectrometric detection. As the main item of interest, we review the potential of GC × GC for the analysis of organohalogenate

  2. Coherent electron focusing with quantum point contacts in a two-dimensional electron gas

    NARCIS (Netherlands)

    Houten, H. van; Beenakker, C.W.J.; Williamson, J.G.; Broekaart, M.E.I.; Loosdrecht, P.H.M. van; Wees, B.J. van; Mooij, J.E.; Foxon, C.T.; Harris, J.J.

    1989-01-01

    Transverse electron focusing in a two-dimensional electron gas is investigated experimentally and theoretically for the first time. A split Schottky gate on top of a GaAs-AlxGa1–xAs heterostructure defines two point contacts of variable width, which are used as injector and collector of ballistic el

  3. A Robust Thermal Modulator for Comprehensive Two-Dimensional Gas Chromatography

    NARCIS (Netherlands)

    Geus, de H.J.; Boer, de J.

    1999-01-01

    In comprehensive two dimensional gas chromatography (GCxGC), two capillary columns are connected in series through an interface known as a 'thermal modulator'. This device transforms effluent from the first capillary column into a series of sharp injection-like chemical pulses suitable for high-spee

  4. Spin-polarized transport in a two-dimensional electron gas with interdigital-ferromagnetic contacts

    DEFF Research Database (Denmark)

    Hu, C.-M.; Nitta, Junsaku; Jensen, Ane

    2001-01-01

    Ferromagnetic contacts on a high-mobility, two-dimensional electron gas (2DEG) in a narrow gap semiconductor with strong spin-orbit interaction are used to investigate spin-polarized electron transport. We demonstrate the use of magnetized contacts to preferentially inject and detect specific spin...

  5. Thermodynamics of Two-Dimensional Electron Gas in a Magnetic Field

    Directory of Open Access Journals (Sweden)

    V. I. Nizhankovskii

    2011-01-01

    Full Text Available Change of the chemical potential of electrons in a GaAs-AlGa1−As heterojunction was measured in magnetic fields up to 6.5 T at several temperatures from 2.17 to 12.3 K. A thermodynamic equation of state of two-dimensional electron gas well describes the experimental results.

  6. Universal relations for the two-dimensional spin-1/2 Fermi gas with contact interactions

    DEFF Research Database (Denmark)

    Valiente, Manuel; Zinner, Nikolaj Thomas; Mølmer, Klaus

    2011-01-01

    We present universal relations for a two-dimensional Fermi gas with pairwise contact interactions. The derivation of these relations is made possible by obtaining the explicit form of a generalized function—selector—in the momentum representation. The selector implements the short-distance bounda...

  7. Pixel-based analysis of comprehensive two-dimensional gas chromatograms (color plots) of petroleum

    DEFF Research Database (Denmark)

    Furbo, Søren; Hansen, Asger B.; Skov, Thomas;

    2014-01-01

    We demonstrate how to process comprehensive two-dimensional gas chromatograms (GC × GC chromatograms) to remove nonsample information (artifacts), including background and retention time shifts. We also demonstrate how this, combined with further reduction of the influence of irrelevant informati...

  8. From spin flip excitations to the spin susceptibility enhancement of a two-dimensional electron gas.

    Science.gov (United States)

    Perez, F; Aku-leh, C; Richards, D; Jusserand, B; Smith, L C; Wolverson, D; Karczewski, G

    2007-07-13

    The g-factor enhancement of the spin-polarized two-dimensional electron gas was measured directly over a wide range of spin polarizations, using spin flip resonant Raman scattering spectroscopy on two-dimensional electron gases embedded in Cd(1-x)Mn(x)Te semimagnetic quantum wells. At zero Raman transferred momentum, the single-particle spin flip excitation, energy Z*, coexists in the Raman spectrum with the spin flip wave of energy Z, the bare giant Zeeman splitting. We compare the measured g-factor enhancement with recent spin-susceptibility enhancement theories and deduce the spin-polarization dependence of the mass renormalization.

  9. Universal relations for the two-dimensional spin-1/2 Fermi gas with contact interactions

    Energy Technology Data Exchange (ETDEWEB)

    Valiente, Manuel; Zinner, Nikolaj T.; Moelmer, Klaus [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark)

    2011-12-15

    We present universal relations for a two-dimensional Fermi gas with pairwise contact interactions. The derivation of these relations is made possible by obtaining the explicit form of a generalized function--selector--in the momentum representation. The selector implements the short-distance boundary condition between two fermions in a straightforward manner and leads to simple derivations of the universal relations, in the spirit of Tan's original method for the three-dimensional gas.

  10. Introducing 2D Materials—a new multidisciplinary journal devoted to all aspects of graphene and related two-dimensional materials

    Science.gov (United States)

    Fal'ko, Vladimir I.

    2014-06-01

    On behalf of the Editorial Board and IOP Publishing, I am pleased to announce the opening of 2D Materials. Research on two-dimensional materials, such as graphene, now involves thousands of researchers worldwide cutting across physics, chemistry, engineering and biology, and extending from fundamental science to novel applications. It is this situation which defines the scope and mission of 2D Materials, a new journal that will serve all sides of this multidisciplinary field by publishing urgent research of the highest quality and impact.

  11. Nonlinear two-dimensional terahertz photon echo and rotational spectroscopy in the gas phase

    CERN Document Server

    Lu, Jian; Hwang, Harold Y; Ofori-Okai, Benjamin K; Fleischer, Sharly; Nelson, Keith A

    2016-01-01

    Ultrafast two-dimensional spectroscopy utilizes correlated multiple light-matter interactions for retrieving dynamic features that may otherwise be hidden under the linear spectrum. Its extension to the terahertz regime of the electromagnetic spectrum, where a rich variety of material degrees of freedom reside, remains an experimental challenge. Here we report ultrafast two-dimensional terahertz spectroscopy of gas-phase molecular rotors at room temperature. Using time-delayed terahertz pulse pairs, we observe photon echoes and other nonlinear signals resulting from molecular dipole orientation induced by three terahertz field-dipole interactions. The nonlinear time-domain orientation signals are mapped into the frequency domain in two-dimensional rotational spectra which reveal J-state-resolved nonlinear rotational dynamics. The approach enables direct observation of correlated rotational transitions and may reveal rotational coupling and relaxation pathways in the ground electronic and vibrational state.

  12. Amino acid analysis by using comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    Mayadunne, Renuka; Nguyen, Thuy-Tien; Marriott, Philip J

    2005-06-01

    The separation characteristics of alkylchloroformate-derivatised amino acids (AAs) by using comprehensive two-dimensional gas chromatography (GCxGC) is reported. The use of a low-polarity/polar column set did not provide as good a separation performance as that achieved with a polar/non-polar column set, where the latter appeared to provide less correlation over the separation space. The degree of component correlation in each column set was estimated by using the correlation coefficient (r(2); for (1)t(R) and (2)t(R) data) with the low-polarity/polar and polar/low-polarity sets returning correlation coefficients of 0.86, and 0.00 respectively, under the respective conditions employed for the experiments. The 1.5-m non-polar (2)D column (0.1-mm ID; 0.1-mum film thickness) gave peak halfwidths of the order of 50-80 ms. Linearity of detection was good, over a three order of magnitude concentration range, with typical lower detection limit of ca. 0.01 mg L(-1), compared with 0.5 mg L(-1) for normal GC operation with splitless injection. The method was demonstrated for analysis of AAs in a range of food and beverage products, including wine, beer and honey. The major AA in these samples was proline. The Heineken beer sample had a relatively more complex and more abundant AA content compared with the other beer sample. The wine and honey samples also gave a range of AA compounds. Repetition of the sample preparation/analysis procedure for the honey sample gave acceptable reproducibility for individual AAs.

  13. Terahertz magneto-optical spectroscopy of a two-dimensional hole gas

    Energy Technology Data Exchange (ETDEWEB)

    Kamaraju, N., E-mail: nkamaraju@lanl.gov; Taylor, A. J.; Prasankumar, R. P., E-mail: rpprasan@lanl.gov [Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Pan, W.; Reno, J. [Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States); Ekenberg, U. [Semiconsultants, Brunnsgrnd 12, SE-18773 Täby (Sweden); Gvozdić, D. M. [School of Electrical Engineering, University of Belgrade, Belgrade 11120 (Serbia); Boubanga-Tombet, S. [Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-Ku, Sendai (Japan); Upadhya, P. C. [Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Laboratory for Electro-Optics Systems, Indian Space Research Organization, Bangalore 560058 (India)

    2015-01-19

    Two-dimensional hole gases (2DHGs) have attracted recent attention for their unique quantum physics and potential applications in areas including spintronics and quantum computing. However, their properties remain relatively unexplored, motivating the use of different techniques to study them. We used terahertz magneto-optical spectroscopy to investigate the cyclotron resonance frequency in a high mobility 2DHG, revealing a nonlinear dependence on the applied magnetic field. This is shown to be due to the complex non-parabolic valence band structure of the 2DHG, as verified by multiband Landau level calculations. We also find that impurity scattering dominates cyclotron resonance decay in the 2DHG, in contrast with the dominance of superradiant damping in two-dimensional electron gases. Our results shed light on the properties of 2DHGs, motivating further studies of these unique 2D nanosystems.

  14. Fission-gas release at extended burnups: effect of two-dimensional heat transfer

    Energy Technology Data Exchange (ETDEWEB)

    Tayal, M. [Atomic Energy of Canada Limited, Mississauga, Ontario (Canada); Yu, S.D. [Ryerson Polytechnic Univ., Toronto, Ontario (Canada); Lau, J.H.K

    2000-09-01

    To better simulate the performance of high-burnup CANDU fuel, a two-dimensional model for heat transfer between the pellet and the sheath has been added to the computer code ELESTRES. The model covers four relative orientations of the pellet and the sheath and their impacts on heat transfer and fission-gas release. The predictions of the code were compared to a database of 27 experimental irradiations involving extended burnups and normal burnups. The calculated values of fission gas release matched the measurements to an average of 94%. Thus, the two-dimensional heat transfer model increases the versatility of the ELESTRES code to better simulate fuels at normal as well as at extended burnups. (author)

  15. [Determination of aromatics in light petroleum products by comprehensive two-dimensional gas chromatography].

    Science.gov (United States)

    Li, Yanyan

    2006-07-01

    In recent years, comprehensive two-dimensional gas chromatography (GC x GC) have been used widely, and the applications of this technique to many fields have already been reported. In the standard method of oil analysis, the concentrations of aromatics and naphthalene hydrocarbons in light petroleum products must be detected by more than two methods. Mono-aromatics, di-aromatics etc. in light petroleum products were detected only by comprehensive two-dimensional gas chromatography. After the proper selection of column system and optimization of chromatographic conditions, the method can achieve the group separations of paraffins, olefins, naphthenes, aromatics with 1 to 2 rings and some target components in light petroleum products with good reproducibility and good precision. The recoveries of standard compounds were 89.5% - 106.1%, and the relative standard deviations of repeatedly detecting the components were all lower than 5.8%. It took only 30 min to finish a determination.

  16. Magnetoresistance of a two-dimensional electron gas in a random magnetic field

    DEFF Research Database (Denmark)

    Smith, Anders; Taboryski, Rafael Jozef; Hansen, Luise Theil

    1994-01-01

    We report magnetoresistance measurements on a two-dimensional electron gas made from a high-mobility GaAs/AlxGa1-xAs heterostructure, where the externally applied magnetic field was expelled from regions of the semiconductor by means of superconducting lead grains randomly distributed on the surf...... on the surface of the sample. A theoretical explanation in excellent agreement with the experiment is given within the framework of the semiclassical Boltzmann equation. © 1994 The American Physical Society...

  17. A New Class of Resonances at the Edge of the Two Dimensional Electron Gas

    OpenAIRE

    Zhitenev, N. B.; Brodsky, M; Ashoori, R. C.; Melloch, M. R.

    1996-01-01

    We measure the frequency dependent capacitance of a gate covering the edge and part of a two-dimensional electron gas in the quantum Hall regime. In applying a positive gate bias, we create a metallic puddle under the gate surrounded by an insulating region. Charging of the puddle occurs via electron tunneling from a metallic edge channel. Analysis of the data allows direct extraction of this tunneling conductance. Novel conductance resonances appear as a function of gate bias. Samples with g...

  18. Interaction of a Surface Acoustic Wave with a Two-dimensional Electron Gas

    Institute of Scientific and Technical Information of China (English)

    YANG Shi-Jie; ZHAO Hu; YU Yue

    2005-01-01

    When a surface acoustic wave (SAW) propagates on the surface of a GaAs semiconductor, coupling between electrons in the two-dimensional electron gas beneath the interface and the elastic host crystal through piezoelectric interaction will attenuate the SAW. The coupling coefficient is calculated for the SAW propagating along an arbitrary direction. It is found that the coupling strength is strongly dependent on the propagating direction. When the SAW propagates along the [011] direction, the coupling becomes quite weak.

  19. Interaction-induced huge magnetoresistance in a high mobility two-dimensional electron gas

    Energy Technology Data Exchange (ETDEWEB)

    Bockhorn, L.; Haug, R. J. [Institut für Festkörperphysik, Leibniz Universität Hannover, D-30167 Hannover (Germany); Gornyi, I. V. [Institut für Nanotechnologie, Karlsruher Institut of Technology, D-76021 Karlsruhe (Germany); Schuh, D. [Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93053 Regensburg (Germany); Wegscheider, W. [ETH Zürich (Switzerland)

    2013-12-04

    A strong negative magnetoresistance is observed in a high-mobility two-dimensional electron gas in a GaAs/Al{sub 0.3}Ga{sub 0.7}As quantum well. We discuss that the negative magnetoresistance consists of a small peak induced by a combination of two types of disorder and a huge magnetoresistance explained by the interaction correction to the conductivity for mixed disorder.

  20. Surface plasmon hurdles leading to a strongly localized giant field enhancement on two-dimensional (2D) metallic diffraction gratings.

    Science.gov (United States)

    Brûlé, Yoann; Demésy, Guillaume; Gralak, Boris; Popov, Evgeny

    2015-04-01

    An extensive numerical study of diffraction of a plane monochromatic wave by a single gold cone on a plane gold substrate and by a periodical array of such cones shows formation of curls in the map of the Poynting vector. They result from the interference between the incident wave, the wave reflected by the substrate, and the field scattered by the cone(s). In case of a single cone, when going away from its base along the surface, the main contribution in the scattered field is given by the plasmon surface wave (PSW) excited on the surface. As expected, it has a predominant direction of propagation, determined by the incident wave polarization. Two particular cones with height approximately 1/6 and 1/3 of the wavelength are studied in detail, as they present the strongest absorption and field enhancement when arranged in a periodic array. While the PSW excited by the smaller single cone shows an energy flux globally directed along the substrate surface, we show that curls of the Poynting vector generated with the larger cone touch the diopter surface. At this point, their direction is opposite to the energy flow of the PSW, which is then forced to jump over the vortex regions. Arranging the cones in a two-dimensional subwavelength periodic array (diffraction grating), supporting a specular reflected order only, resonantly strengthens the field intensity at the tip of cones and leads to a field intensity enhancement of the order of 10 000 with respect to the incident wave intensity. The enhanced field is strongly localized on the rounded top of the cones. It is accompanied by a total absorption of the incident light exhibiting large angular tolerances. This strongly localized giant field enhancement can be of much interest in many applications, including fluorescence spectroscopy, label-free biosensing, surface-enhanced Raman scattering (SERS), nonlinear optical effects and photovoltaics.

  1. An algorithm for circular test and improved optical configuration by two-dimensional (2D) laser heterodyne interferometer

    Science.gov (United States)

    Tang, Shanzhi; Yu, Shengrui; Han, Qingfu; Li, Ming; Wang, Zhao

    2016-09-01

    Circular test is an important tactic to assess motion accuracy in many fields especially machine tool and coordinate measuring machine. There are setup errors due to using directly centring of the measuring instrument for both of contact double ball bar and existed non-contact methods. To solve this problem, an algorithm for circular test using function construction based on matrix operation is proposed, which is not only used for the solution of radial deviation (F) but also should be applied to obtain two other evaluation parameters especially circular hysteresis (H). Furthermore, an improved optical configuration with a single laser is presented based on a 2D laser heterodyne interferometer. Compared with the existed non-contact method, it has a more pure homogeneity of the laser sources of 2D displacement sensing for advanced metrology. The algorithm and modeling are both illustrated. And error budget is also achieved. At last, to validate them, test experiments for motion paths are implemented based on a gantry machining center. Contrast test results support the proposal.

  2. Near-infrared (NIR) monitoring of Nylon 6 during quenching studied by projection two-dimensional (2D) correlation spectroscopy

    Science.gov (United States)

    Shinzawa, Hideyuki; Mizukado, Junji

    2016-11-01

    Evolutionary change in supermolecular structure of Nylon 6 during its melt-quenched process was studied by Near-infrared (NIR) spectroscopy. Time-resolved NIR spectra was measured by taking the advantage of high-speed NIR monitoring based on an acousto-optic tunable filter (AOTF). Fine spectral features associated with the variation of crystalline and amorphous structure occurring in relatively short time scale were readily captured. For example, synchronous and asynchronous 2D correlation spectra reveal the initial decrease in the contribution of the NIR band at 1485 nm due to the amorphous structure, predominantly existing in the melt Nylon 6. This is then followed by the emerging contribution of the band intensity at 1535 nm associated with the crystalline structure. Consequently, the results clearly demonstrate a definite advantage of the high-speed NIR monitoring for analyzing fleeting phenomena.

  3. On Berezinskii-Kosterlitz-Thouless phase transition and universal breathing mode in two dimensional photon gas

    OpenAIRE

    Vyas, Vivek M.; Panigrahi, Prasanta. K.; Banerji, J.

    2013-01-01

    A system of two dimensional photon gas has recently been realized experimentally. It is pointed out that this setup can be used to observe a universal breathing mode of photon gas. It is shown that a modification in the experimental setup would open up a possibility of observing the Berezinskii-Kosterlitz-Thouless (BKT) phase transition in such a system. It is shown that the universal jump in the superfluid density of light in the output channel can be used as an unambiguous signature for the...

  4. On Berezinskii-Kosterlitz-Thouless phase transition and universal breathing mode in two dimensional photon gas

    CERN Document Server

    Vyas, Vivek M; Banerji, J

    2013-01-01

    A system of two dimensional photon gas has recently been realized experimentally. It is pointed out that this setup can be used to observe a universal breathing mode of photon gas. It is shown that a modification in the experimental setup would open up a possibility of observing the Berezinskii-Kosterlitz-Thouless (BKT) phase transition in such a system. It is shown that the universal jump in the superfluid density of light in the output channel can be used as an unambiguous signature for the experimental verification of the BKT transition.

  5. Cromatografia gasosa bidimensional abrangente (GC × GC Comprehensive two-dimensional gas chromatography (GC × GC

    Directory of Open Access Journals (Sweden)

    Marcio Pozzobon Pedroso

    2009-01-01

    Full Text Available This paper presents the fundamental principles, instrumentation and selected applications of comprehensive two-dimensional gas chromatography (GC × GC. In this technique, introduced in 1991, two capillary columns are coupled and proper modulating interfaces continuously collect the eluate from the first column, transferring it to the second column. The result is a geometric increment in the chromatographic resolution, ensuring separation of extremely complex mixtures in time periods shorter or comparable to those of analysis using conventional gas chromatography and with better detectabilities and sensitivities.

  6. Qualitative and quantitative analysis of vetiver essential oils by comprehensive two-dimensional gas chromatography and comprehensive two-dimensional gas chromatography/mass spectrometry.

    Science.gov (United States)

    Filippi, Jean-Jacques; Belhassen, Emilie; Baldovini, Nicolas; Brevard, Hugues; Meierhenrich, Uwe J

    2013-05-03

    Vetiver essential oils (VEO) are important raw ingredients used in perfume industry, entering the formula of numerous modern fragrances. Vetiver oils are considered to be among the most complex essential oils, resulting most of the time in highly coeluted chromatograms whatever the analytical technique. In this context, conventional gas chromatography has failed to provide a routine tool for the accurate qualitative and quantitative analysis of their constituents. Applying comprehensive two-dimensional gas chromatography techniques (GC×GC-FID/MS) afforded the mean to separate efficiently vetiver oil constituents in order to identify them in a more reliable way. Moreover, this is the first time that a complete true quantitation of each constituent is carried out on such complex oils by means of internal calibration. Finally, we have studied the influence of the injection mode on the determined chemical composition, and showed that several alcohols underwent dehydration under defined chromatographic conditions (splitless mode) usually recommended for quantitation purposes. Copyright © 2013 Elsevier B.V. All rights reserved.

  7. Observation of a pairing pseudogap in a two-dimensional Fermi gas.

    Science.gov (United States)

    Feld, Michael; Fröhlich, Bernd; Vogt, Enrico; Koschorreck, Marco; Köhl, Michael

    2011-11-30

    Pairing of fermions is ubiquitous in nature, underlying many phenomena. Examples include superconductivity, superfluidity of (3)He, the anomalous rotation of neutron stars, and the crossover between Bose-Einstein condensation of dimers and the BCS (Bardeen, Cooper and Schrieffer) regime in strongly interacting Fermi gases. When confined to two dimensions, interacting many-body systems show even more subtle effects, many of which are not understood at a fundamental level. Most striking is the (as yet unexplained) phenomenon of high-temperature superconductivity in copper oxides, which is intimately related to the two-dimensional geometry of the crystal structure. In particular, it is not understood how the many-body pairing is established at high temperature, and whether it precedes superconductivity. Here we report the observation of a many-body pairing gap above the superfluid transition temperature in a harmonically trapped, two-dimensional atomic Fermi gas in the regime of strong coupling. Our measurements of the spectral function of the gas are performed using momentum-resolved photoemission spectroscopy, analogous to angle-resolved photoemission spectroscopy in the solid state. Our observations mark a significant step in the emulation of layered two-dimensional strongly correlated superconductors using ultracold atomic gases.

  8. Two Dimensional Electrostrictive Field Effect Transistor (2D-EFET): A sub-60mV/decade Steep Slope Device with High ON current

    Science.gov (United States)

    Das, Saptarshi

    2016-01-01

    This article proposes a disruptive device concept which meets both low power and high performance criterion for post-CMOS computing and at the same time enables aggressive channel length scaling. This device, hereafter refer to as two-dimensional electrostrictive field effect transistor or 2D-EFET, allows sub-60 mV/decade subthreshold swing and considerably higher ON current compared to any state of the art FETs. Additionally, by the virtue of its ultra-thin body nature and electrostatic integrity, the 2D-EFET enjoys scaling beyond 10 nm technology node. The 2D-EFET works on the principle of voltage induced strain transduction. It uses an electrostrictive material as gate oxide which expands in response to an applied gate bias and thereby transduces an out-of-plane stress on the 2D channel material. This stress reduces the inter-layer distance between the consecutive layers of the semiconducting 2D material and dynamically reduces its bandgap to zero i.e. converts it into a semi-metal. Thus the device operates with a large bandgap in the OFF state and a small or zero bandgap in the ON state. As a consequence of this transduction mechanism, internal voltage amplification takes place which results in sub-60 mV/decade subthreshold swing (SS). PMID:27721489

  9. Two Dimensional Electrostrictive Field Effect Transistor (2D-EFET): A sub-60mV/decade Steep Slope Device with High ON current

    Science.gov (United States)

    Das, Saptarshi

    2016-10-01

    This article proposes a disruptive device concept which meets both low power and high performance criterion for post-CMOS computing and at the same time enables aggressive channel length scaling. This device, hereafter refer to as two-dimensional electrostrictive field effect transistor or 2D-EFET, allows sub-60 mV/decade subthreshold swing and considerably higher ON current compared to any state of the art FETs. Additionally, by the virtue of its ultra-thin body nature and electrostatic integrity, the 2D-EFET enjoys scaling beyond 10 nm technology node. The 2D-EFET works on the principle of voltage induced strain transduction. It uses an electrostrictive material as gate oxide which expands in response to an applied gate bias and thereby transduces an out-of-plane stress on the 2D channel material. This stress reduces the inter-layer distance between the consecutive layers of the semiconducting 2D material and dynamically reduces its bandgap to zero i.e. converts it into a semi-metal. Thus the device operates with a large bandgap in the OFF state and a small or zero bandgap in the ON state. As a consequence of this transduction mechanism, internal voltage amplification takes place which results in sub-60 mV/decade subthreshold swing (SS).

  10. Two-dimensional (2D) infrared correlation study of the structural characterization of a surface immobilized polypeptide film stimulated by pH

    Science.gov (United States)

    Chae, Boknam; Son, Seok Ho; Kwak, Young Jun; Jung, Young Mee; Lee, Seung Woo

    2016-11-01

    The pH-induced structural changes to surface immobilized poly (L-glutamic acid) (PLGA) films were examined by Fourier transform infrared (FTIR) spectroscopy and two-dimensional (2D) correlation analysis. Significant spectral changes were observed in the FTIR spectra of the surface immobilized PLGA film between pH 6 and 7. The 2D correlation spectra constructed from the pH-dependent FTIR spectra of the surface immobilized PLGA films revealed the spectral changes induced by the alternations of the protonation state of the carboxylic acid group in the PLGA side chain. When the pH was increased from 6 to 8, weak spectral changes in the secondary structure of the PLGA main chain were induced by deprotonation of the carboxylic acid side group.

  11. A two-dimensional Fermi gas in the BEC-BCS crossover

    Energy Technology Data Exchange (ETDEWEB)

    Ries, Martin Gerhard

    2016-01-21

    This thesis reports on the preparation of a 2D Fermi gas in the BEC-BCS crossover and the observation of the BKT transition into a quasi long-range ordered superfluid phase. The pair momentum distribution of the gas is probed by means of a matter-wave focusing technique which relies on time-of-flight evolution in a weak harmonic potential. This distribution holds the coherence properties of the gas. The quasi long-range ordered phase manifests itself as a sharp low-momentum peak. The temperature where it forms is identified as the transition temperature. By tuning the temperature and the interaction strength, the phase diagram of the 2D Fermi gas in the BEC-BCS crossover is mapped out. The phase coherence is investigated in a self-interference experiment. Furthermore, algebraic decay of correlations is observed in the trap average of the first order correlation function, which is obtained from the Fourier transform of the pair momentum distribution. This is in qualitative agreement with predictions of homogeneous theory for the superfluid phase in a 2D gas. The presented results provide a foundation for future experimental and theoretical studies of strongly correlated 2D Fermi gases. They might thus help to elucidate complex systems such as the electron gas in high-T{sub c} superconductors.

  12. Kinetic Theory of a Confined Quasi-Two-Dimensional Gas of Hard Spheres

    Directory of Open Access Journals (Sweden)

    J. Javier Brey

    2017-02-01

    Full Text Available The dynamics of a system of hard spheres enclosed between two parallel plates separated a distance smaller than two particle diameters is described at the level of kinetic theory. The interest focuses on the behavior of the quasi-two-dimensional fluid seen when looking at the system from above or below. In the first part, a collisional model for the effective two-dimensional dynamics is analyzed. Although it is able to describe quite well the homogeneous evolution observed in the experiments, it is shown that it fails to predict the existence of non-equilibrium phase transitions, and in particular, the bimodal regime exhibited by the real system. A critical revision analysis of the model is presented , and as a starting point to get a more accurate description, the Boltzmann equation for the quasi-two-dimensional gas has been derived. In the elastic case, the solutions of the equation verify an H-theorem implying a monotonic tendency to a non-uniform steady state. As an example of application of the kinetic equation, here the evolution equations for the vertical and horizontal temperatures of the system are derived in the homogeneous approximation, and the results compared with molecular dynamics simulation results.

  13. Metal Oxide Gas Sensor Drift Compensation Using a Two-Dimensional Classifier Ensemble

    Directory of Open Access Journals (Sweden)

    Hang Liu

    2015-04-01

    Full Text Available Sensor drift is the most challenging problem in gas sensing at present. We propose a novel two-dimensional classifier ensemble strategy to solve the gas discrimination problem, regardless of the gas concentration, with high accuracy over extended periods of time. This strategy is appropriate for multi-class classifiers that consist of combinations of pairwise classifiers, such as support vector machines. We compare the performance of the strategy with those of competing methods in an experiment based on a public dataset that was compiled over a period of three years. The experimental results demonstrate that the two-dimensional ensemble outperforms the other methods considered. Furthermore, we propose a pre-aging process inspired by that applied to the sensors to improve the stability of the classifier ensemble. The experimental results demonstrate that the weight of each multi-class classifier model in the ensemble remains fairly static before and after the addition of new classifier models to the ensemble, when a pre-aging procedure is applied.

  14. Piezoelectric Electromechanical Coupling in Nanomechanical Resonators with a Two-Dimensional Electron Gas

    Science.gov (United States)

    Shevyrin, A. A.; Pogosov, A. G.; Bakarov, A. K.; Shklyaev, A. A.

    2016-07-01

    The electrical response of a two-dimensional electron gas to vibrations of a nanomechanical cantilever containing it is studied. Vibrations of perpendicularly oriented cantilevers are experimentally shown to oppositely change the conductivity near their bases. This indicates the piezoelectric nature of electromechanical coupling. A physical model is developed, which quantitatively explains the experiment. It shows that the main origin of the conductivity change is a rapid change in the mechanical stress on the boundary between suspended and nonsuspended areas, rather than the stress itself.

  15. Electromechanical coupling in suspended nanomechanical resonators with a two-dimensional electron gas

    Science.gov (United States)

    Shevyrin, A. A.; Pogosov, A. G.; Bakarov, A. K.; Shklyaev, A. A.

    2017-06-01

    A physical model describing the piezoelectric-effect-mediated influence of bending of a thin suspended cantilever with a two-dimensional electron gas on the conductivity is proposed. The model shows that the conductivity change is almost entirely caused by the rapid change in mechanical stress near the boundary of suspended and non-suspended areas, rather than by the stress itself. An experiment confirming that the electromechanical coupling is associated with the piezoelectric effect is performed. The experimentally measured conductance sensitivity to the cantilever’s vibrations agree with the developed physical model.

  16. Ultra-low-temperature cooling of two-dimensional electron gas

    Science.gov (United States)

    Xia, J. S.; Adams, E. D.; Shvarts, V.; Pan, W.; Stormer, H. L.; Tsui, D. C.

    2000-05-01

    A new design has been used for cooling GaAs/Al xGa 1- xAs sample to ultra-low-temperatures. The sample, with electrical contacts directly soldered to the sintered silver powder heat exchangers, was immersed in liquid 3He, which was cooled by a PrNI 5 nuclear refrigerator. The data analysis shows that the two-dimensional electron gas (2DEG) was cooled to 4.0 mK at the refrigerator base temperature Tb of 2.0 mK. The design with heat exchanger cooling is applicable to any ultra-low-temperature transport measurements of 2DEG system.

  17. Spin injection into a two-dimensional electron gas using inter-digital-ferromagnetic contacts

    DEFF Research Database (Denmark)

    Hu, C.M.; Nitta, J.; Jensen, Ane;

    2002-01-01

    We present a model that describes the spin injection across a single interface with two electrodes. The spin-injection rate across a typical hybrid junction made of ferromagnet (FM) and a two-dimensional electron gas (2DEG) is found at the percentage level. We perforin spin-injection-detection ex......-injection-detection experiment on devices with two ferromagnetic contacts on a 2DEG confined in an InAs quantum well. A spin-injection rate of 4.5% is estimated from the measured magnetoresistance....

  18. Quantum spin-glass transition in the two-dimensional electron gas

    Indian Academy of Sciences (India)

    Subir Sachdev

    2002-02-01

    We discuss the possibility of spin-glass order in the vicinity of the unexpected metallic state of the two-dimensional electron gas in zero applied magnetic field. An average ferromagnetic moment may also be present, and the spin-glass order then resides in the plane orthogonal to the ferromagnetic moment. We argue that a quantum transition involving the destruction of the spin-glass order in an applied in-plane magnetic field offers a natural explanation of some features of recent magnetoconductance measurements. We present a quantum field theory for such a transition and compute its mean field properties.

  19. Electrically Detected Magnetic Resonance of Neutral Donors Interacting with a Two-Dimensional Electron Gas

    Energy Technology Data Exchange (ETDEWEB)

    Lo, C. C.; Lang, V.; George, R. E.; Morton, J. J. L.; Tyryshkin, A. M.; Lyon, A.; Bokor, J.; Schenkel, T.

    2011-04-20

    We have measured the electrically detected magnetic resonance of donor-doped silicon field-effect transistors in resonant X- (9.7 GHz) and W-band (94 GHz) microwave cavities. The two-dimensional electron gas (2DEG) resonance signal increases by two orders of magnitude from X- to W-band, while the donor resonance signals are enhanced by over one order of magnitude. Bolometric effects and spin-dependent scattering are inconsistent with the observations. We propose that polarization transfer from the donor to the 2DEG is the main mechanism giving rise to the spin resonance signals.

  20. Photon-assisted spin transport in a two-dimensional electron gas

    OpenAIRE

    Fistul, M. V.; Efetov, K. B.

    2007-01-01

    We study spin-dependent transport in a two-dimensional electron gas subject to an external step-like potential $V(x)$ and irradiated by an electromagnetic field (EF). In the absence of EF the electronic spectrum splits into spin sub-bands originating from the "Rashba" spin-orbit coupling. We show that the resonant interaction of propagating electrons with the component EF parallel to the barrier induces a \\textit{% non-equilibrium dynamic gap} $(2\\Delta_{R})$ between the spin sub-bands. Exist...

  1. Thermodynamic magnetization of two-dimensional electron gas measured over wide range of densities

    OpenAIRE

    Reznikov, M.; Kuntsevich, A. Yu.; Teneh, N.; Pudalov, V. M.

    2011-01-01

    We report measurements of dm/dn in Si MOSFET, where m is the magnetization of the two-dimensional electron gas and n is its density. We extended the density range of measurements from well in the metallic to deep in the insulating region. The paper discusses in detail the conditions under which this extension is justified, as well as the corrections one should make to extract dm/dn properly. At low temperatures, dm/dn was found to be strongly nonlinear already in weak magnetic fields, on a sc...

  2. Extraordinary waves in two dimensional electron gas with separate spin evolution and Coulomb exchange interaction

    CERN Document Server

    Andreev, Pavel A

    2016-01-01

    Hydrodynamics analysis of waves in two-dimensional degenerate electron gas with the account of separate spin evolution is presented. The transverse electric field is included along with the longitudinal electric field. The Coulomb exchange interaction is included in the analysis. In contrast with the three-dimensional plasma-like mediums the contribution of the transverse electric field is small. We show the decrease of frequency of both the extraordinary (Langmuir) wave and the spin-electron acoustic wave due to the exchange interaction. Moreover, spin-electron acoustic wave has negative dispersion at the relatively large spin-polarization. Corresponding dispersion dependencies are presented and analyzed.

  3. Resonant Peak Splitting for Ballistic Conductance in Two-Dimensional Electron Gas Under Electromagnetic Modulation

    Institute of Scientific and Technical Information of China (English)

    WANG Ru-Zhi; YAN Xiao-Hong

    2000-01-01

    By developing a transfer-matrix method, the resonant peaks splitting of ballistic conductance are investigated into the two-dimensional electron gas system with both electric and magnetic modulations of nanoscale periods. It is found that there exists the n-fold resonant peak splitting for ballistic conductance through n perpendicular magnetic barriers to n electric barriers. With a combination of m magnetic barriers and n electric barriers by increasing the amplitude of electric field, the folds of the splitting would shift from m - 1 to n - 1.

  4. Diffusivity and weak clustering in a quasi-two-dimensional granular gas.

    Science.gov (United States)

    Perera-Burgos, J A; Pérez-Ángel, G; Nahmad-Molinari, Y

    2010-11-01

    We present results from a detailed simulation of a quasi-two-dimensional dissipative granular gas, kept in a noncondensed steady state via vertical shaking over a rough substrate. This gas shows a weak power-law decay in the tails of its pair distribution functions, indicating clustering. This clustering depends monotonically on the dissipation coefficient and disappears when the sphere-sphere collisions are conservative. Clustering is also sensitive to the packing fraction. This gas also displays the standard nonequilibrium characteristics of similar systems, including non-Maxwellian velocity distributions. The diffusion coefficients are calculated over all the conditions of the simulations, and it is found that diluted gases are more diffusive for smaller restitution coefficients.

  5. Shear viscosity and spin-diffusion coefficient of a two-dimensional Fermi gas

    DEFF Research Database (Denmark)

    Bruun, Georg

    2012-01-01

    Using kinetic theory, we calculate the shear viscosity and the spin-diffusion coefficient as well as the associated relaxation times for a two-component Fermi gas in two dimensions, as a function of temperature, coupling strength, polarization, and mass ratio of the two components. It is demonstr......Using kinetic theory, we calculate the shear viscosity and the spin-diffusion coefficient as well as the associated relaxation times for a two-component Fermi gas in two dimensions, as a function of temperature, coupling strength, polarization, and mass ratio of the two components....... It is demonstrated that the minimum value of the viscosity decreases with the mass ratio, since Fermi blocking becomes less efficient. We furthermore analyze recent experimental results for the quadrupole mode of a two-dimensional gas in terms of viscous damping, obtaining a qualitative agreement using no fitting...

  6. Device for two-dimensional gas-phase separation and characterization of ion mixtures

    Science.gov (United States)

    Tang, Keqi; Shvartsburg, Alexandre A.; Smith, Richard D.

    2006-12-12

    The present invention relates to a device for separation and characterization of gas-phase ions. The device incorporates an ion source, a field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer, an ion mobility spectrometry (IMS) drift tube, and an ion detector. In one aspect of the invention, FAIMS operating voltages are electrically floated on top of the IMS drift voltage. In the other aspect, the FAIMS/IMS interface is implemented employing an electrodynamic ion funnel, including in particular an hourglass ion funnel. The present invention improves the efficiency (peak capacity) and sensitivity of gas-phase separations; the online FAIMS/IMS coupling creates a fundamentally novel two-dimensional gas-phase separation technology with high peak capacity, specificity, and exceptional throughput.

  7. Generalized two-dimensional (2D) linear system analysis metrics (GMTF, GDQE) for digital radiography systems including the effect of focal spot, magnification, scatter, and detector characteristics

    Science.gov (United States)

    Kuhls-Gilcrist, Andrew T.; Gupta, Sandesh K.; Bednarek, Daniel R.; Rudin, Stephen

    2010-01-01

    The MTF, NNPS, and DQE are standard linear system metrics used to characterize intrinsic detector performance. To evaluate total system performance for actual clinical conditions, generalized linear system metrics (GMTF, GNNPS and GDQE) that include the effect of the focal spot distribution, scattered radiation, and geometric unsharpness are more meaningful and appropriate. In this study, a two-dimensional (2D) generalized linear system analysis was carried out for a standard flat panel detector (FPD) (194-micron pixel pitch and 600-micron thick CsI) and a newly-developed, high-resolution, micro-angiographic fluoroscope (MAF) (35-micron pixel pitch and 300-micron thick CsI). Realistic clinical parameters and x-ray spectra were used. The 2D detector MTFs were calculated using the new Noise Response method and slanted edge method and 2D focal spot distribution measurements were done using a pin-hole assembly. The scatter fraction, generated for a uniform head equivalent phantom, was measured and the scatter MTF was simulated with a theoretical model. Different magnifications and scatter fractions were used to estimate the 2D GMTF, GNNPS and GDQE for both detectors. Results show spatial non-isotropy for the 2D generalized metrics which provide a quantitative description of the performance of the complete imaging system for both detectors. This generalized analysis demonstrated that the MAF and FPD have similar capabilities at lower spatial frequencies, but that the MAF has superior performance over the FPD at higher frequencies even when considering focal spot blurring and scatter. This 2D generalized performance analysis is a valuable tool to evaluate total system capabilities and to enable optimized design for specific imaging tasks. PMID:21243038

  8. Magnetoelectronic transport of the two-dimensional electron gas in CdSe single quantum wells

    Indian Academy of Sciences (India)

    P K Ghosh; A Ghosal; D Chattopadhyay

    2009-02-01

    Hall mobility and magnetoresistance coefficient for the two-dimensional (2D) electron transport parallel to the heterojunction interfaces in a single quantum well of CdSe are calculated with a numerical iterative technique in the framework of Fermi–Dirac statistics. Lattice scatterings due to polar-mode longitudinal optic (LO) phonons, and acoustic phonons via deformation potential and piezoelectric couplings, are considered together with background and remote ionized impurity interactions. The parallel mode of piezoelectric scattering is found to contribute more than the perpendicular mode. We observe that the Hall mobility decreases with increasing temperature but increases with increasing channel width. The magnetoresistance coefficient is found to decrease with increasing temperature and increase with increasing magnetic field in the classical region.

  9. Properties of two-dimensional electron gas containing self-organized quantum antidots

    Science.gov (United States)

    Vasilyev, Yu.; Suchalkin, S.; Zundel, M.; Heisenberg, D.; Eberl, K.; von Klitzing, K.

    1999-11-01

    A nonuniform two-dimensional electron gas in a heterojunction with inserted self-organized electrically inactive dots (acting as antidots) has been fabricated by molecular-beam epitaxy of AlGaAs/AlInAs/GaAs layer sequences. Transport measurements give the ratio of the transport mobility to the quantum mobility less than four, which suggests that the dominant scattering at low magnetic fields is the short-range scattering from the lateral potential of the antidots. Far-infrared cyclotron resonance (CR) spectra show an absorption mode as narrow as 0.5 cm-1 at high magnetic fields associated with the high-mobility electron gas formed between the antidot islands and confined in the lateral directions. The confinement energy of 14 cm-1 is derived from the CR spectra.

  10. Piecewise parabolic negative magnetoresistance of two-dimensional electron gas with triangular antidot lattice

    Energy Technology Data Exchange (ETDEWEB)

    Budantsev, M. V., E-mail: budants@isp.nsc.ru; Lavrov, R. A.; Pogosov, A. G.; Zhdanov, E. Yu.; Pokhabov, D. A. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

    2011-02-15

    Extraordinary piecewise parabolic behavior of the magnetoresistance has been experimentally detected in the two-dimensional electron gas with a dense triangular lattice of antidots, where commensurability magnetoresistance oscillations are suppressed. The magnetic field range of 0-0.6 T can be divided into three wide regions, in each of which the magnetoresistance is described by parabolic dependences with high accuracy (comparable to the experimental accuracy) and the transition regions between adjacent regions are much narrower than the regions themselves. In the region corresponding to the weakest magnetic fields, the parabolic behavior becomes almost linear. The observed behavior is reproducible as the electron gas density changes, which results in a change in the resistance by more than an order of magnitude. Possible physical mechanisms responsible for the observed behavior, including so-called 'memory effects,' are discussed.

  11. Coupled two-dimensional edge plasma and neutral gas modeling of tokamak scrape-off-layers

    Energy Technology Data Exchange (ETDEWEB)

    Maingi, R. [North Carolina State Univ., Raleigh, NC (United States)

    1992-08-01

    The objective of this study is to devise a detailed description of the tokamak scrape-off-layer (SOL), which includes the best available models of both the plasma and neutral species and the strong coupling between the two in many SOL regimes. A good estimate of both particle flux and heat flux profiles at the limiter/divertor target plates is desired. Peak heat flux is one of the limiting factors in determining the survival probability of plasma-facing-components at high power levels. Plate particle flux affects the neutral flux to the pump, which determines the particle exhaust rate. A technique which couples a two-dimensional (2-D) plasma and a 2-D neutral transport code has been developed (coupled code technique), but this procedure requires large amounts of computer time. Relevant physics has been added to an existing two-neutral-species model which takes the SOL plasma/neutral coupling into account in a simple manner (molecular physics model), and this model is compared with the coupled code technique mentioned above. The molecular physics model is benchmarked against experimental data from a divertor tokamak (DIII-D), and a similar model (single-species model) is benchmarked against data from a pump-limiter tokamak (Tore Supra). The models are then used to examine two key issues: free-streaming-limits (ion energy conduction and momentum flux) and the effects of the non-orthogonal geometry of magnetic flux surfaces and target plates on edge plasma parameter profiles.

  12. An accurate predictor-corrector HOC solver for the two dimensional Riemann problem of gas dynamics

    Science.gov (United States)

    Gogoi, Bidyut B.

    2016-10-01

    The work in the present manuscript is concerned with the simulation of twodimensional (2D) Riemann problem of gas dynamics. We extend our recently developed higher order compact (HOC) method from one-dimensional (1D) to 2D solver and simulate the problem on a square geometry with different initial conditions. The method is fourth order accurate in space and second order accurate in time. We then compare our results with the available benchmark results. The comparison shows an excellent agreement of our results with the existing ones in the literature. Being a finite difference solver, it is quite straight-forward and simple.

  13. Two-dimensional correlation spectroscopy (2D-COS) variable selection for near-infrared microscopy discrimination of meat and bone meal in compound feed.

    Science.gov (United States)

    Lü, Chengxu; Chen, Longjian; Yang, Zengling; Liu, Xian; Han, Lujia

    2014-01-01

    This article presents a novel method for combining auto-peak and cross-peak information for sensitive variable selection in synchronous two-dimensional correlation spectroscopy (2D-COS). This variable selection method is then applied to the case of near-infrared (NIR) microscopy discrimination of meat and bone meal (MBM). This is of important practical value because MBM is currently banned in ruminate animal compound feed. For the 2D-COS analysis, a set of NIR spectroscopy data of compound feed samples (adulterated with varying concentrations of MBM) was pretreated using standard normal variate and detrending (SNVD) and then mapped to the 2D-COS synchronous matrix. For the auto-peak analysis, 12 main sensitive variables were identified at 6852, 6388, 6320, 5788, 5600, 5244, 4900, 4768, 4572, 4336, 4256, and 4192 cm(-1). All these variables were assigned their specific spectral structure and chemical component. For the cross-peak analysis, these variables were divided into two groups, each group containing the six sensitive variables. This grouping resulted in a correlation between the spectral variables that was in accordance with the chemical-component content of the MBM and compound feed. These sensitive variables were then used to build a NIR microscopy discrimination model, which yielded a 97% correct classification. Moreover, this method detected the presence of MBM when its concentration was less than 1% in an adulterated compound feed sample. The concentration-dependent 2D-COS-based variable selection method developed in this study has the unique advantages of (1) introducing an interpretive aspect into variable selection, (2) substantially reducing the complexity of the computations, (3) enabling the transferability of the results to discriminant analysis, and (4) enabling the efficient compression of spectral data.

  14. Direct observation of two dimensional trace gas distributions with an airborne Imaging DOAS instrument

    Directory of Open Access Journals (Sweden)

    K.-P. Heue

    2008-11-01

    Full Text Available In many investigations of tropospheric chemistry information about the two dimensional distribution of trace gases on a small scale (e.g. tens to hundreds of metres is highly desirable. An airborne instrument based on imaging Differential Optical Absorption Spectroscopy has been built to map the two dimensional distribution of a series of relevant trace gases including NO2, HCHO, C2H2O2, H2O, O4, SO2, and BrO on a scale of 100 m.

    Here we report on the first tests of the novel aircraft instrument over the industrialised South African Highveld, where large variations in NO2 column densities in the immediate vicinity of several sources e.g. power plants or steel works, were measured. The observed patterns in the trace gas distribution are interpreted with respect to flux estimates, and it is seen that the fine resolution of the measurements allows separate sources in close proximity to one another to be distinguished.

  15. Retention modelling of polychlorinated biphenyls in comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    D'Archivio, Angelo Antonio; Incani, Angela; Ruggieri, Fabrizio

    2011-01-01

    In this paper, we use a quantitative structure-retention relationship (QSRR) method to predict the retention times of polychlorinated biphenyls (PCBs) in comprehensive two-dimensional gas chromatography (GC×GC). We analyse the GC×GC retention data taken from the literature by comparing predictive capability of different regression methods. The various models are generated using 70 out of 209 PCB congeners in the calibration stage, while their predictive performance is evaluated on the remaining 139 compounds. The two-dimensional chromatogram is initially estimated by separately modelling retention times of PCBs in the first and in the second column ((1) t (R) and (2) t (R), respectively). In particular, multilinear regression (MLR) combined with genetic algorithm (GA) variable selection is performed to extract two small subsets of predictors for (1) t (R) and (2) t (R) from a large set of theoretical molecular descriptors provided by the popular software Dragon, which after removal of highly correlated or almost constant variables consists of 237 structure-related quantities. Based on GA-MLR analysis, a four-dimensional and a five-dimensional relationship modelling (1) t (R) and (2) t (R), respectively, are identified. Single-response partial least square (PLS-1) regression is alternatively applied to independently model (1) t (R) and (2) t (R) without the need for preliminary GA variable selection. Further, we explore the possibility of predicting the two-dimensional chromatogram of PCBs in a single calibration procedure by using a two-response PLS (PLS-2) model or a feed-forward artificial neural network (ANN) with two output neurons. In the first case, regression is carried out on the full set of 237 descriptors, while the variables previously selected by GA-MLR are initially considered as ANN inputs and subjected to a sensitivity analysis to remove the redundant ones. Results show PLS-1 regression exhibits a noticeably better descriptive and predictive

  16. Chemical profiling and adulteration screening of Aquilariae Lignum Resinatum by Fourier transform infrared (FT-IR) spectroscopy and two-dimensional correlation infrared (2D-IR) spectroscopy.

    Science.gov (United States)

    Qu, Lei; Chen, Jian-Bo; Zhang, Gui-Jun; Sun, Su-Qin; Zheng, Jing

    2017-03-05

    As a kind of expensive perfume and valuable herb, Aquilariae Lignum Resinatum (ALR) is often adulterated for economic motivations. In this research, Fourier transform infrared (FT-IR) spectroscopy is employed to establish a simple and quick method for the adulteration screening of ALR. First, the principal chemical constituents of ALR are characterized by FT-IR spectroscopy at room temperature and two-dimensional correlation infrared (2D-IR) spectroscopy with thermal perturbation. Besides the common cellulose and lignin compounds, a certain amount of resin is the characteristic constituent of ALR. Synchronous and asynchronous 2D-IR spectra indicate that the resin (an unstable secondary metabolite) is more sensitive than cellulose and lignin (stable structural constituents) to the thermal perturbation. Using a certified ALR sample as the reference, the infrared spectral correlation threshold is determined by 30 authentic samples and 6 adulterated samples. The spectral correlation coefficient of an authentic ALR sample to the standard reference should be not less than 0.9886 (p=0.01). Three commercial adulterated ALR samples are identified by the correlation threshold. Further interpretation of the infrared spectra of the adulterated samples indicates the common adulterating methods - counterfeiting with other kind of wood, adding ingredient such as sand to increase the weight, and adding the cheap resin such as rosin to increase the content of resin compounds. Results of this research prove that FT-IR spectroscopy can be used as a simple and accurate quality control method of ALR.

  17. Near-infrared (NIR) imaging analysis of polylactic acid (PLA) nanocomposite by multiple-perturbation two-dimensional (2D) correlation spectroscopy

    Science.gov (United States)

    Shinzawa, Hideyuki; Murakami, Takurou N.; Nishida, Masakazu; Kanematsu, Wataru; Noda, Isao

    2014-07-01

    Multiple-perturbation two-dimensional (2D) correlation spectroscopy was applied to sets of near-infrared (NIR) imaging data of polylactic acid (PLA) nanocomposite samples undergoing UV degradation. Incorporation of clay nanoparticles substantially lowers the surface free energy barrier for the nucleation of PLA and eventually increases the frequency of the spontaneous nucleation of PLA crystals. Thus, when exposed to external stimuli such as UV light, PLA nanocomposite may show different structure alternation depending on the clay dispersion. Multiple-perturbation 2D correlation analysis of the PLA nanocomposite samples revealed different spatial variation between crystalline and amorphous structure of PLA, and the phenomenon especially becomes acute in the region where the clay particles are coagulated. The incorporation of the clay leads to the cleavage-induced crystallization of PLA when the sample is subjected to the UV light. The additional development of the ordered crystalline structure then works favorably to restrict the initial degradation of the polymer, providing the delay in the weight loss of the PLA.

  18. Chemical profiling and adulteration screening of Aquilariae Lignum Resinatum by Fourier transform infrared (FT-IR) spectroscopy and two-dimensional correlation infrared (2D-IR) spectroscopy

    Science.gov (United States)

    Qu, Lei; Chen, Jian-bo; Zhang, Gui-Jun; Sun, Su-qin; Zheng, Jing

    2017-03-01

    As a kind of expensive perfume and valuable herb, Aquilariae Lignum Resinatum (ALR) is often adulterated for economic motivations. In this research, Fourier transform infrared (FT-IR) spectroscopy is employed to establish a simple and quick method for the adulteration screening of ALR. First, the principal chemical constituents of ALR are characterized by FT-IR spectroscopy at room temperature and two-dimensional correlation infrared (2D-IR) spectroscopy with thermal perturbation. Besides the common cellulose and lignin compounds, a certain amount of resin is the characteristic constituent of ALR. Synchronous and asynchronous 2D-IR spectra indicate that the resin (an unstable secondary metabolite) is more sensitive than cellulose and lignin (stable structural constituents) to the thermal perturbation. Using a certified ALR sample as the reference, the infrared spectral correlation threshold is determined by 30 authentic samples and 6 adulterated samples. The spectral correlation coefficient of an authentic ALR sample to the standard reference should be not less than 0.9886 (p = 0.01). Three commercial adulterated ALR samples are identified by the correlation threshold. Further interpretation of the infrared spectra of the adulterated samples indicates the common adulterating methods - counterfeiting with other kind of wood, adding ingredient such as sand to increase the weight, and adding the cheap resin such as rosin to increase the content of resin compounds. Results of this research prove that FT-IR spectroscopy can be used as a simple and accurate quality control method of ALR.

  19. Effects on the Thermo-Mechanical and Crystallinity Properties of Nylon 6,6 Electrospun Fibres Reinforced with One Dimensional (1D and Two Dimensional (2D Carbon

    Directory of Open Access Journals (Sweden)

    Francisco Medellín-Rodríguez

    2013-08-01

    Full Text Available Electrospun one dimensional (1D and two dimensional (2D carbon based polymer nanocomposites are studied in order to determine the effect provided by the two differently structured nanofillers on crystallinity and thermo-mechanical properties of the nanofibres. The nanomaterials studied are pristine carbon nanotubes, oxidised carbon nanotubes, reduced graphene oxide and graphene oxide. Functional groups associated with the order structure of the polymers are analysed by infrared and Raman spectroscopies; the morphology is studied by scanning electron microscopy and the crystallinity properties are investigated by differential scanning calorimetry and X-ray diffraction. Differences in crystallisation behaviour between 1D and 2D carbon based nanofibres are shown by their crystallinity degree and their crystal sizes. The nanocomposite crystal sizes perpendicular to the plane (100 decrease with nanofiller content in all cases. The crystallinity trend and crystal sizes are in accordance with storage modulus response. The results also suggest that functionalisation favours interfacial bonding and dispersion of the nanomaterials within the polymer matrix. As a consequence the number of nucleating sites increases which in turn decreases the crystal size in the nanocomposites. These features explain the improved thermo-mechanical properties in the nanocomposites.

  20. A two-dimensional position sensitive gas chamber with scanned charge transfer readout

    Science.gov (United States)

    Gómez, F.; Iglesias, A.; Lobato, R.; Mosquera, J.; Pardo, J.; Pena, J.; Pazos, A.; Pombar, M.; Rodríguez, A.

    2003-10-01

    We have constructed and tested a two-dimensional position sensitive parallel-plate gas ionization chamber with scanned charge transfer readout. The scan readout method described here is based on the development of a new position-dependent charge transfer technique. It has been implemented by using gate strips perpendicularly oriented to the collector strips. This solution reduces considerably the number of electronic readout channels needed to cover large detector areas. The use of a 25 μm thick kapton etched circuit allows high charge transfer efficiency with a low gating voltage, consequently needing a very simple commutating circuit. The present prototype covers 8×8 cm2 with a pixel size of 1.27×1.27 mm2. Depending on the intended use and beam characteristics a smaller effective pixel is feasible and larger active areas are possible. This detector can be used for X-ray or other continuous beam intensity profile monitoring.

  1. Hydrodynamics for a model of a confined quasi-two-dimensional granular gas.

    Science.gov (United States)

    Brey, J Javier; Buzón, V; Maynar, P; García de Soria, M I

    2015-05-01

    The hydrodynamic equations for a model of a confined quasi-two-dimensional gas of smooth inelastic hard spheres are derived from the Boltzmann equation for the model, using a generalization of the Chapman-Enskog method. The heat and momentum fluxes are calculated to Navier-Stokes order, and the associated transport coefficients are explicitly determined as functions of the coefficient of normal restitution and the velocity parameter involved in the definition of the model. Also an Euler transport term contributing to the energy transport equation is considered. This term arises from the gradient expansion of the rate of change of the temperature due to the inelasticity of collisions, and it vanishes for elastic systems. The hydrodynamic equations are particularized for the relevant case of a system in the homogeneous steady state. The relationship with previous works is analyzed.

  2. Realization and Characterization of a Curved Two-dimensional Electron Gas

    Science.gov (United States)

    Shaji, Nakul; Deneke, Christoph

    2005-03-01

    Using the built-in strain from lattice mismatch between Al0.33Ga0.67As and In0.2Ga0.8As as a bending force, a strip of two-dimensional electron gas (2DEG) in an AlxGa1-xAs/GaAs/AlxGa1-xAs heterostructure is curved into a tube when released from the substrate by wet etching. A variety of mesoscopic quantum devices can be defined in such curved 2DEG structures. This technology opens the door for investigating geometry-dependent electron transport under non-uniform magnetic fields. We have defined Hall bar patterns from a sheet of 2DEG using both optical and electron-beam lithography. The sample characterization under an external magnetic field will be discussed.

  3. Modulation techniques and applications in comprehensive two-dimensional gas chromatography (GC x GC)

    Energy Technology Data Exchange (ETDEWEB)

    Pursch, Matthias [Dow Deutschland GmbH and Co. OHG, Analytical Sciences, 77836 Rheinmuenster (Germany); Sun, Kefu; Winniford, Bill; Weber, Andy [Dow Chemical Company, Analytical Sciences, Freeport, TX 77541 (United States); Cortes, Hernan; McCabe, Terry [Dow Chemical Company, Analytical Sciences, Midland MI 48667 (United States); Luong, Jim [Dow Canada, Analytical Sciences, Fort Saskatchewan (Canada)

    2002-07-01

    More than a decade after Phillips' first published work this article reviews recent developments in comprehensive two-dimensional gas chromatography (GC x GC). Special attention is devoted to the further development and diversity of modulation devices. These include heated sweepers, cryofocused modulators, and a variety of diaphragm valve-switching strategies. It is demonstrated that all modulation approaches can be very well suited to GC x GC, depending on the particular application. Diaphragm-valve modulation is very powerful for volatile organic compounds. Slotted heater and cryofocused modulation are preferred for samples that contain non-volatile components. Applications ranging from petroleum to environmental and biological samples are illustrated. Extension of the technique to GC x GC-mass spectrometry (MS) is also discussed and trends for future research activity are pointed out. (orig.)

  4. Gas-kinetic numerical schemes for one- and two-dimensional inner flows

    Institute of Scientific and Technical Information of China (English)

    Zhi-hui LI; Lin BI; Zhi-gong TANG

    2009-01-01

    Several kinds of explicit and implicit finite-difference schemes directly solving the discretized velocity distribution functions are designed with precision of different orders by analyzing the inner characteristics of the gas-kinetic numerical algorithm for Boltzmann model equation.The peculiar flow phenomena and mechanism from various flow regimes are revealed in the numerical simulations of the unsteady Sod shock-tube problems and the two-dimensional channel flows with different Knudsen numbers.The numerical remainder-effects of the difference schemes are investigated and analyzed based on the computed results.The ways of improving the computational efficiency of the gaskinetic numerical method and the computing principles of difference discretization are discussed.

  5. Automated multivariate analysis of comprehensive two-dimensional gas chromatograms of petroleum

    DEFF Research Database (Denmark)

    Skov, Søren Furbo

    Petroleum is an economically and industrially important resource. Crude oil must be refined before use to ensure suitable properties of the product. Among the processes used in this refining is distillation and desulfurization. In order to optimize these processes, it is essential to understand...... them. Comprehensive two-dimensional gas chromatography (GCGC) is a method for analyzing the volatile parts of a sample. It can separate hundreds or thousands of compounds based on their boiling point, polarity and polarizability. This makes it ideally suited for petroleum analysis. The number...... impossible to find it. For a special class of models, multi-way models, unique solutions often exist, meaning that the underlying phenomena can be found. I have tested this class of models on GCGC data from petroleum and conclude that more work is needed before they can be automated. I demonstrate how...

  6. Cavity quantum electrodynamics with many-body states of a two-dimensional electron gas.

    Science.gov (United States)

    Smolka, Stephan; Wuester, Wolf; Haupt, Florian; Faelt, Stefan; Wegscheider, Werner; Imamoglu, Ataç

    2014-10-17

    Light-matter interaction has played a central role in understanding as well as engineering new states of matter. Reversible coupling of excitons and photons enabled groundbreaking results in condensation and superfluidity of nonequilibrium quasiparticles with a photonic component. We investigated such cavity-polaritons in the presence of a high-mobility two-dimensional electron gas, exhibiting strongly correlated phases. When the cavity was on resonance with the Fermi level, we observed previously unknown many-body physics associated with a dynamical hole-scattering potential. In finite magnetic fields, polaritons show distinct signatures of integer and fractional quantum Hall ground states. Our results lay the groundwork for probing nonequilibrium dynamics of quantum Hall states and exploiting the electron density dependence of polariton splitting so as to obtain ultrastrong optical nonlinearities.

  7. Terahertz Radiation Heterodyne Detector Using Two-Dimensional Electron Gas in a GaN Heterostructure

    Science.gov (United States)

    Karasik, Boris S.; Gill, John J.; Mehdi, Imran; Crawford, Timothy J.; Sergeev, Andrei V.; Mitin, Vladimir V.

    2012-01-01

    High-resolution submillimeter/terahertz spectroscopy is important for studying atmospheric and interstellar molecular gaseous species. It typically uses heterodyne receivers where an unknown (weak) signal is mixed with a strong signal from the local oscillator (LO) operating at a slightly different frequency. The non-linear mixer devices for this frequency range are unique and are not off-the-shelf commercial products. Three types of THz mixers are commonly used: Schottky diode, superconducting hot-electron bolometer (HEB), and superconductor-insulation-superconductor (SIS) junction. A HEB mixer based on the two-dimensional electron gas (2DEG) formed at the interface of two slightly dissimilar semiconductors was developed. This mixer can operate at temperatures between 100 and 300 K, and thus can be used with just passive radiative cooling available even on small spacecraft.

  8. Hidden long-range order in a two-dimensional spin-orbit coupled Bose gas

    CERN Document Server

    Su, Shih-Wei; Gou, Shih-Chuan; Liao, Renyuan; Fialko, Oleksandr; Brand, Joachim

    2016-01-01

    A two-dimensional spin-orbit coupled Bose gas is shown to simultaneously possess quasi and true long-range orders in the total and relative phases, respectively. The total phase undergoes a conventional Berenzinskii- Kosterlitz-Thouless transition, where an quasi long-range order is expected. Additionally, the relative phase undergoes an Ising-type transition building up true long-range order, which is induced by the anisotropic spin- orbit coupling. Based on the Bogoliubov approach, expressions for the total- and relative-phase fluctuations are derived analytically for the low temperature regime. Numerical simulations of the stochastic projected Gross- Pitaevskii equation give a good agreement with the analytical predictions.

  9. Optimization of micro-strip gas chamber as two-dimensional neutron detector using gadolinium converter

    Energy Technology Data Exchange (ETDEWEB)

    Masaoka, Sei; Nakamura, Tatsuya; Yamagishi, Hideshi; Soyama, Kazuhiko [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2002-02-01

    A micro-strip gas chamber (MSGC) has been developing as a two-dimensional position sensitive neutron detector for neutron scattering experiments using high-intensity pulsed-neutron source in a high-intensity proton accelerator facility. MSGC is required for the high count rate, high detective efficiency, high positional resolution, stabilization and covering large area. Our purpose in this paper is to verify the proper of Gadolinium as MSGC converter. First, the basic property of Gadolinium converter was examined by simple experiments using a zero-dimensional neutron detector on the purpose of deriving the detective efficiency. Second, the optimization of the arrangement of a capillary plate in MSGC has been done by simulation on the MSGC using Gadolinium converter. As a result of that, it has been proved that Gadolinium can be theoretically used as a converter of MSGC. (author)

  10. Offline coupling of high-speed counter-current chromatography and gas chromatography/mass spectrometry generates a two-dimensional plot of toxaphene components.

    Science.gov (United States)

    Kapp, Thomas; Vetter, Walter

    2009-11-20

    High-speed counter-current chromatography (HSCCC), a separation technique based solely on the partitioning of solutes between two immiscible liquid phases, was applied for the fractionation of technical toxaphene, an organochlorine pesticide which consists of a complex mixture of structurally closely related compounds. A solvent system (n-hexane/methanol/water 34:24:1, v/v/v) was developed which allowed to separate compounds of technical toxaphene (CTTs) with excellent retention of the stationary phase (S(f) = 88%). Subsequent analysis of all HSCCC fractions by gas chromatography coupled to electron-capture negative ion mass spectrometry (GC/ECNI-MS) provided a wealth of information regarding separation characteristics of HSCCC and the composition of technical toxaphene. The visualization of the large amount of data obtained from the offline two-dimensional HSCCC-GC/ECNI-MS experiment was facilitated by the creation of a two-dimensional (2D) contour plot. The contour plot not only provided an excellent overview of the HSCCC separation progress, it also illustrated the differences in selectivity between HSCCC and GC. The results of this proof-of-concept study showed that the 2D chromatographic approach involving HSCCC facilitated the separation of CTTs that coelute in unidimensional GC. Furthermore, the creation of 2D contour plots may provide a useful means of enhancing data visualization for other offline two-dimensional separations.

  11. Thermalization of a two-dimensional photon gas in a polymeric host matrix

    Science.gov (United States)

    Schmitt, Julian; Damm, Tobias; Vewinger, Frank; Weitz, Martin; Klaers, Jan

    2012-07-01

    We investigate thermodynamic properties of a two-dimensional photon gas confined by a dye-filled optical microcavity. A thermally equilibrated state of the photon gas is achieved by radiative coupling to a heat bath that is realized with dye molecules embedded in a polymer at room temperature. The chemical potential of the gas is freely adjustable. The optical microcavity consisting of two curved mirrors induces both a non-vanishing effective photon mass and a harmonic trapping potential for the photons. While previous experiments of our group have used liquid dye solutions, the measurements described here are based on dye molecules incorporated into a polymer host matrix. The solid state material allows a simplified operation of the experimental scheme. We furthermore describe studies of fluorescence properties of dye-doped polymers, and verify the applicability of Kennard-Stepanov theory in this system. In the future, dye-based solid state systems hold promise for the realization of single-mode light sources in thermal equilibrium based on Bose-Einstein condensation of photons, as well as for solar energy concentrators.

  12. 2D-MoO3 nanosheets for superior gas sensors

    Science.gov (United States)

    Ji, Fangxu; Ren, Xianpei; Zheng, Xiaoyao; Liu, Yucheng; Pang, Liuqing; Jiang, Jiaxing; Liu, Shengzhong (Frank)

    2016-04-01

    By taking advantages of both grinding and sonication, an effective exfoliation process is developed to prepare two-dimensional (2D) molybdenum oxide (MoO3) nanosheets. The approach avoids high-boiling-point solvents that would leave a residue and cause aggregation. Gas sensors fabricated using the 2D-MoO3 nanosheets provide a significantly enhanced chemical sensor performance. Compared with the sensors using bulk MoO3, the response of the 2D-MoO3 sensor increases from 7 to 33; the sensor response time is reduced from 27 to 21 seconds, and the recovery time is shortened from 26 to 10 seconds. We attribute the superior performance to the 2D-structure with a much increased surface area and reactive sites.By taking advantages of both grinding and sonication, an effective exfoliation process is developed to prepare two-dimensional (2D) molybdenum oxide (MoO3) nanosheets. The approach avoids high-boiling-point solvents that would leave a residue and cause aggregation. Gas sensors fabricated using the 2D-MoO3 nanosheets provide a significantly enhanced chemical sensor performance. Compared with the sensors using bulk MoO3, the response of the 2D-MoO3 sensor increases from 7 to 33; the sensor response time is reduced from 27 to 21 seconds, and the recovery time is shortened from 26 to 10 seconds. We attribute the superior performance to the 2D-structure with a much increased surface area and reactive sites. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00880a

  13. Determination of toxaphene enantiomers by comprehensive two-dimensional gas chromatography with electron-capture detection.

    Science.gov (United States)

    Bordajandi, Luisa R; Ramos, Lourdes; González, María José

    2006-09-01

    Comprehensive two-dimensional gas chromatography with micro electron-capture detection (GC x GC-microECD) has been evaluated for the enantioseparation of five chiral toxaphenes typically found in real-life samples (Parlar 26, 32, 40, 44 and 50). From the two enantioselective beta-cyclodextrin-based columns evaluated as first dimension column, BGB-176SE and BGB-172, the latter provided the best results and was further combined with three non-enantioselective columns in the second dimension: HT-8, BPX-50 and Supelcowax-10. The combination BGB-172 x BPX-50 was finally selected because it provided a complete separation among all enantiomers. A satisfactory repeatability and reproducibility of the retention times in both the first and the second dimension were observed for all target compounds (RSDs below 0.8%, n = 4). Linear responses in the tested range of 10-200 pg/microl and limits of detection in the range of 2-6 pg/microl were obtained. The repeatability and reproducibility at a concentration of 100 pg/microl, evaluated as the RSDs calculated for the enantiomeric fraction (EF), was better than 11% (n = 4) in all instances. The feasibility of the method developed for real-life analyses was illustrated by the determination of the enantiomeric ratios and concentration levels of the test compounds in four commercial fish oil samples. These results were compared to those obtained by heart-cut multidimensional gas chromatography using the same enantioselective column.

  14. Thermalization of a two-dimensional photonic gas in a `white wall' photon box

    Science.gov (United States)

    Klaers, Jan; Vewinger, Frank; Weitz, Martin

    2010-07-01

    Bose-Einstein condensation, the macroscopic accumulation of bosonic particles in the energetic ground state below a critical temperature, has been demonstrated in several physical systems. The perhaps best known example of a bosonic gas, blackbody radiation, however exhibits no Bose-Einstein condensation at low temperatures. Instead of collectively occupying the lowest energy mode, the photons disappear in the cavity walls when the temperature is lowered-corresponding to a vanishing chemical potential. Here we report on evidence for a thermalized two-dimensional photon gas with a freely adjustable chemical potential. Our experiment is based on a dye-filled optical microresonator, acting as a `white wall' box for photons. Thermalization is achieved in a photon-number-conserving way by photon scattering off the dye molecules, and the cavity mirrors provide both an effective photon mass and a confining potential-key prerequisites for the Bose-Einstein condensation of photons. As a striking example of the unusual system properties, we demonstrate a yet unobserved light concentration effect into the centre of the confining potential, an effect with prospects for increasing the efficiency of diffuse solar light collection.

  15. Observation of Spin Coulomb Drag in a Two-Dimensional Electron Gas

    Energy Technology Data Exchange (ETDEWEB)

    Weber, C.P.

    2011-08-19

    An electron propagating through a solid carries spin angular momentum in addition to its mass and charge. Of late there has been considerable interest in developing electronic devices based on the transport of spin, which offer potential advantages in dissipation, size, and speed over charge-based devices. However, these advantages bring with them additional complexity. Because each electron carries a single, fixed value (-e) of charge, the electrical current carried by a gas of electrons is simply proportional to its total momentum. A fundamental consequence is that the charge current is not affected by interactions that conserve total momentum, notably collisions among the electrons themselves. In contrast, the electron's spin along a given spatial direction can take on two values, {+-} {h_bar}/2 (conventionally {up_arrow}, {down_arrow}), so that the spin current and momentum need not be proportional. Although the transport of spin polarization is not protected by momentum conservation, it has been widely assumed that, like the charge current, spin current is unaffected by electron-electron (e-e) interactions. Here we demonstrate experimentally not only that this assumption is invalid, but that over a broad range of temperature and electron density, the flow of spin polarization in a two-dimensional gas of electrons is controlled by the rate of e-e collisions.

  16. A laterally averaged two-dimensional simulation of unsteady supersaturated total dissolved gas in deep reservoir

    Institute of Scientific and Technical Information of China (English)

    FENG Jing-jie; LI Ran; YANG Hui-xia; LI Jia

    2013-01-01

    Elevated levels of the Total Dissolved Gas (TDG) may be reached downstream of dams,leading to increased incidences of gas bubble diseases in fish.The supersaturated TDG dissipates and transports more slowly in reservoirs than in natural rivers because of the greater depth and the lower turbulence,which endangers the fish more seriously.With consideration of the topographical characteristics of a deep reservoir,a laterally averaged two-dimensional unsteady TDG model for deep reservoir is proposed.The dissipation process of the TDG inside the waterbody and the mass transfer through the free surface are separately modeled with different functions in the model.Hydrodynamics equations are solved coupling with those of water temperature and density.The TDG concentration is calculated based on the density current field.A good agreement is found in the simulation of the Dachaoshan Reservoir between the simulation results and the field data of the hydrodynamics parameters and the TDG distribution in the vertical direction and their unsteady evolution with time.The hydrodynamics parameters,the temperature and the TDG concentration are analyzed based on the simulation results.This study demonstrates that the model can be used to predict the evolutions of hydrodynamics parameters,the temperature and the TDG distribution in a deep reservoir with unsteady inflow and outflow.The results can be used in the study of the mitigation measures of the supersaturated TDG.

  17. Density of states in a two-dimensional electron gas: Impurity bands and band tails

    Science.gov (United States)

    Gold, A.; Serre, J.; Ghazali, A.

    1988-03-01

    We calculate the density of states of a two-dimensional electron gas in the presence of charged impurities within Klauder's best multiple-scattering approach. The silicon metal-oxide-semiconductor (MOS) system with impurities at the interface is studied in detail. The finite extension of the electron wave function into the bulk is included as well as various dependences of the density of states on the electron, the depletion, and the impurity densities. The transition from an impurity band at low impurity concentration to a band tail at high impurity concentration is found to take place at a certain impurity concentration. If the screening parameter of the electron gas is decreased, the impurity band shifts to lower energy. For low impurity density we find excited impurity bands. Our theory at least qualitatively explains conductivity and infrared-absorption experiments on impurity bands in sodium-doped MOS systems and deep band tails in the gap observed for high doping levels in these systems.

  18. Macroporous polymer monoliths as second dimension columns in comprehensive two-dimensional gas chromatography: a feasibility study

    NARCIS (Netherlands)

    D. Peroni; R.J. Vonk; W. van Egmond; H.-G. Janssen

    2012-01-01

    When the typical column combinations are used, comprehensive two-dimensional gas chromatography (GC × GC) suffers from the impossibility to operate both dimensions at their optimum carrier gas velocities at the same time. This as a result of the flow mismatch caused by the different dimensions of th

  19. Haptic-2D: A new haptic test battery assessing the tactual abilities of sighted and visually impaired children and adolescents with two-dimensional raised materials.

    Science.gov (United States)

    Mazella, Anaïs; Albaret, Jean-Michel; Picard, Delphine

    2016-01-01

    To fill an important gap in the psychometric assessment of children and adolescents with impaired vision, we designed a new battery of haptic tests, called Haptic-2D, for visually impaired and sighted individuals aged five to 18 years. Unlike existing batteries, ours uses only two-dimensional raised materials that participants explore using active touch. It is composed of 11 haptic tests, measuring scanning skills, tactile discrimination skills, spatial comprehension skills, short-term tactile memory, and comprehension of tactile pictures. We administered this battery to 138 participants, half of whom were sighted (n=69), and half visually impaired (blind, n=16; low vision, n=53). Results indicated a significant main effect of age on haptic scores, but no main effect of vision or Age × Vision interaction effect. Reliability of test items was satisfactory (Cronbach's alpha, α=0.51-0.84). Convergent validity was good, as shown by a significant correlation (age partialled out) between total haptic scores and scores on the B101 test (rp=0.51, n=47). Discriminant validity was also satisfactory, as attested by a lower but still significant partial correlation between total haptic scores and the raw score on the verbal WISC (rp=0.43, n=62). Finally, test-retest reliability was good (rs=0.93, n=12; interval of one to two months). This new psychometric tool should prove useful to practitioners working with young people with impaired vision.

  20. Two Dimensional Spin-Polarized Electron Gas at the Oxide Interfaces

    OpenAIRE

    Nanda, B. R. K.; Satpathy, S.

    2008-01-01

    The formation of a novel spin-polarized 2D electron gas at the LaMnO$_3$ monolayer embedded in SrMnO$_3$ is predicted from the first-principles density-functional calculations. The La (d) electrons become confined in the direction normal to the interface in the potential well of the La layer, serving as a positively-charged layer of electron donors. These electrons mediate a ferromagnetic alignment of the Mn t$_{2g}$ spins near the interface via the Anderson-Hasegawa double exchange and becom...

  1. The success of Fermi gas model for overall scaling of 2D metal-to-insulator transition data

    Science.gov (United States)

    Cheremisin, M. V.

    2017-03-01

    The melting condition for two-dimensional Wigner solid (Platzman and Fukuyama, 1974) [14] is shown to contain an error of a factor of π. The analysis of experimental data for apparent 2D metal-to-insulator transition shows that the Wigner solidification (Tanatar and Ceperley, 1989) [16] has been never achieved. Within routine Fermi gas model both the metallic and insulating behavior of different 2D system for actual range of carrier densities and temperatures is explained.

  2. Tuning the conductivity threshold and carrier density of two-dimensional electron gas at oxide interfaces through interface engineering

    Directory of Open Access Journals (Sweden)

    H. J. Harsan Ma

    2015-08-01

    Full Text Available The two-dimensional electron gas (2DEG formed at the perovskite oxides heterostructures is of great interest because of its potential applications in oxides electronics and nanoscale multifunctional devices. A canonical example is the 2DEG at the interface between a polar oxide LaAlO3 (LAO and non-polar SrTiO3 (STO. Here, the LAO polar oxide can be regarded as the modulating or doping layer and is expected to define the electronic properties of 2DEG at the LAO/STO interface. However, to practically implement the 2DEG in electronics and device design, desired properties such as tunable 2D carrier density are necessary. Here, we report the tuning of conductivity threshold, carrier density and electronic properties of 2DEG in LAO/STO heterostructures by insertion of a La0.5Sr0.5TiO3 (LSTO layer of varying thicknesses, and thus modulating the amount of polarization of the oxide over layers. Our experimental result shows an enhancement of carrier density up to a value of about five times higher than that observed at the LAO/STO interface. A complete thickness dependent metal-insulator phase diagram is obtained by varying the thickness of LAO and LSTO providing an estimate for the critical thickness needed for the metallic phase. The observations are discussed in terms of electronic reconstruction induced by polar oxides.

  3. Doppler Velocimetry of Current Driven Spin Helices in a Two-Dimensional Electron Gas

    Science.gov (United States)

    Yang, Luyi

    Spins in semiconductors provide a pathway towards the development of spin-based electronics. The appeal of spin logic devices lies in the fact that the spin current is even under time reversal symmetry, yielding non-dissipative coupling to the electric field. To exploit the energy-saving potential of spin current it is essential to be able to control it. While recent demonstrations of electrical-gate control in spin-transistor configurations show great promise, operation at room temperature remains elusive. Further progress requires a deeper understanding of the propagation of spin polarization, particularly in the high mobility semiconductors used for devices. This thesis presents the demonstration and application of a powerful new optical technique, Doppler spin velocimetry, for probing the motion of spin polarization at the level of 1 nm on a picosecond time scale. We discuss experiments in which this technique is used to measure the motion of spin helices in high mobility n-GaAs quantum wells as a function of temperature, in-plane electric field, and photoinduced spin polarization amplitude. We find that the spin helix velocity changes sign as a function of wave vector and is zero at the wave vector that yields the largest spin lifetime. This observation is quite striking, but can be explained by the random walk model that we have developed. We discover that coherent spin precession within a propagating spin density wave is lost at temperatures near 150 K. This finding is critical to understanding why room temperature operation of devices based on electrical gate control of spin current has so far remained elusive. We report that, at all temperatures, electron spin polarization co-propagates with the high-mobility electron sea, even when this requires an unusual form of separation of spin density from photoinjected electron density. Furthermore, although the spin packet co-propagates with the two-dimensional electron gas, spin diffusion is strongly suppressed

  4. Quenching Plasma Waves in Two Dimensional Electron Gas by a Femtosecond Laser Pulse

    Science.gov (United States)

    Shur, Michael; Rudin, Sergey; Greg Rupper Collaboration; Andrey Muraviev Collaboration

    Plasmonic detectors of terahertz (THz) radiation using the plasma wave excitation in 2D electron gas are capable of detecting ultra short THz pulses. To study the plasma wave propagation and decay, we used femtosecond laser pulses to quench the plasma waves excited by a short THz pulse. The femtosecond laser pulse generates a large concentration of the electron-hole pairs effectively shorting the 2D electron gas channel and dramatically increasing the channel conductance. Immediately after the application of the femtosecond laser pulse, the equivalent circuit of the device reduces to the source and drain contact resistances connected by a short. The total response charge is equal to the integral of the current induced by the THz pulse from the moment of the THz pulse application to the moment of the femtosecond laser pulse application. This current is determined by the plasma wave rectification. Registering the charge as a function of the time delay between the THz and laser pulses allowed us to follow the plasmonic wave decay. We observed the decaying oscillations in a sample with a partially gated channel. The decay depends on the gate bias and reflects the interplay between the gated and ungated plasmons in the device channel. Army Research Office.

  5. Strongly anomalous non-thermal fixed point in a quenched two-dimensional Bose gas

    CERN Document Server

    Karl, Markus

    2016-01-01

    Universal scaling behavior in the relaxation dynamics of an isolated two-dimensional Bose gas is studied by means of semi-classical stochastic simulations of the Gross-Pitaevskii model. The system is quenched far out of equilibrium by imprinting vortex defects into an otherwise phase-coherent condensate. A strongly anomalous non-thermal fixed point is identified, associated with a slowed decay of the defects in the case that the dissipative coupling to the thermal background noise is suppressed. At this fixed point, a large anomalous exponent $\\eta \\simeq -3$ and, related to this, a large dynamical exponent $z \\simeq 5$ are identified. The corresponding power-law decay is found to be consistent with three-vortex-collision induced loss. The article discusses these aspects of non-thermal fixed points in the context of phase-ordering kinetics and coarsening dynamics, thus relating phenomenological and analytical approaches to classifying far-from-equilibrium scaling dynamics with each other. In particular, a clo...

  6. Strongly anomalous non-thermal fixed point in a quenched two-dimensional Bose gas

    Science.gov (United States)

    Karl, Markus; Gasenzer, Thomas

    2017-09-01

    Universal scaling behavior in the relaxation dynamics of an isolated two-dimensional Bose gas is studied by means of semi-classical stochastic simulations of the Gross–Pitaevskii model. The system is quenched far out of equilibrium by imprinting vortex defects into an otherwise phase-coherent condensate. A strongly anomalous non-thermal fixed point is identified, associated with a slowed decay of the defects in the case that the dissipative coupling to the thermal background noise is suppressed. At this fixed point, a large anomalous exponent η ≃ -3 and, related to this, a large dynamical exponent z≃ 5 are identified. The corresponding power-law decay is found to be consistent with three-vortex-collision induced loss. The article discusses these aspects of non-thermal fixed points in the context of phase-ordering kinetics and coarsening dynamics, thus relating phenomenological and analytical approaches to classifying far-from-equilibrium scaling dynamics with each other. In particular, a close connection between the anomalous scaling exponent η, introduced in a quantum-field theoretic approach, and conservation-law induced scaling in classical phase-ordering kinetics is revealed. Moreover, the relation to superfluid turbulence as well as to driven stationary systems is discussed.

  7. A two-dimensional position sensitive gas chamber with scanned charge transfer readout

    Energy Technology Data Exchange (ETDEWEB)

    Gomez, F. E-mail: faustgr@usc.es; Iglesias, A.; Lobato, R.; Mosquera, J.; Pardo, J.; Pena, J.; Pazos, A.; Pombar, M.; Rodriguez, A

    2003-10-21

    We have constructed and tested a two-dimensional position sensitive parallel-plate gas ionization chamber with scanned charge transfer readout. The scan readout method described here is based on the development of a new position-dependent charge transfer technique. It has been implemented by using gate strips perpendicularly oriented to the collector strips. This solution reduces considerably the number of electronic readout channels needed to cover large detector areas. The use of a 25 {mu}m thick kapton etched circuit allows high charge transfer efficiency with a low gating voltage, consequently needing a very simple commutating circuit. The present prototype covers 8x8 cm{sup 2} with a pixel size of 1.27x1.27 mm{sup 2}. Depending on the intended use and beam characteristics a smaller effective pixel is feasible and larger active areas are possible. This detector can be used for X-ray or other continuous beam intensity profile monitoring.

  8. Forensic profiling of sassafras oils based on comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    Schäffer, M; Gröger, T; Pütz, M; Zimmermann, R

    2013-06-10

    Safrole, the main compound in the essential oil of several plants of the Laurel family (Lauraceae), and its secondary product piperonylmethylketone are the predominantly used precursors for the illicit synthesis of 3,4-methylenedioxymethamphetamine (MDMA) which is, in turn, the most common active ingredient in Ecstasy tablets. Analytical methods with adequate capacity to identify links and origin of precursors, such as safrole, provide valuable information for drug-related police intelligence. Authentic sassafras oil samples from police seizures were subjected to comparative analysis based on their chemical profiles obtained by comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC-TOFMS). The enhanced separation power and increased sensitivity of GC × GC allowed for the detection of minor compounds present in the essential oils which were of particular interest in case of very pure samples whose impurity profiles were not very pronounced. Discrimination of such samples was still possible even in the absence of characteristic main compounds.

  9. Analysis of siloxanes in hydrocarbon mixtures using comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    Ghosh, Abhijit; Seeley, Stacy K; Nartker, Steven R; Seeley, John V

    2014-09-19

    A comprehensive two-dimensional gas chromatography (GC×GC) method for separating siloxanes from hydrocarbons has been developed using a systematic process. First, the retention indices of a set of siloxanes and a set of hydrocarbons were determined on 6 different stationary phases. The retention indices were then used to model GC×GC separation on 15 different stationary phase pairs. The SPB-Octyl×DB-1 pair was predicted to provide the best separation of the siloxanes from the hydrocarbons. The efficacy of this stationary phase pair was experimentally tested by performing a GC×GC analysis of gasoline spiked with siloxanes and by analyzing biogas obtained from a local wastewater treatment facility. The model predictions agreed well with the experimental results. The SPB-Octyl×DB-1 stationary phase pair constrained the hydrocarbons to a narrow range of secondary retention times and fully isolated the siloxanes from the hydrocarbon band. The resulting GC×GC method allows siloxanes to be resolved from complex mixtures of hydrocarbons without requiring the use of a selective detector.

  10. Electrical transport of an AlGaN/GaN two-dimensional electron gas

    Energy Technology Data Exchange (ETDEWEB)

    Saxler, A.; Debray, P.; Perrin, R. [and others

    2000-07-01

    An Al{sub x}Ga{sub 1{minus}x}N/GaN two-dimensional electron gas structure with x = 0.13 deposited by molecular beam epitaxy on a GaN layer grown by organometallic vapor phase epitaxy on a sapphire substrate was characterized. Hall effect measurements gave a sheet electron concentration of 5.1x10{sup 12} cm{sup {minus}2} and a mobility of 1.9 x 10{sup 4} cm{sup 2}/Vs at 10 K. Mobility spectrum analysis showed single-carrier transport and negligible parallel conduction at low temperatures. The sheet carrier concentrations determined from Shubnikov-de Haas magnetoresistance oscillations were in good agreement with the Hall data. The electron effective mass was determined to be 0.21 {+-} 0.006 m{sub 0} based on the temperature dependence of the amplitude of Shubnikov-de Haas oscillations. The quantum lifetime was about one-fifth of the transport lifetime of 2.3 x 10{sup {minus}12} s.

  11. Analysis of oxidised heavy paraffininc products by high temperature comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    Potgieter, H; Bekker, R; Beigley, J; Rohwer, E

    2017-08-04

    Heavy petroleum fractions are produced during crude and synthetic crude oil refining processes and they need to be upgraded to useable products to increase their market value. Usually these fractions are upgraded to fuel products by hydrocracking, hydroisomerization and hydrogenation processes. These fractions are also upgraded to other high value commercial products like lubricant oils and waxes by distillation, hydrogenation, and oxidation and/or blending. Oxidation of hydrogenated heavy paraffinic fractions produces high value products that contain a variety of oxygenates and the characterization of these heavy oxygenates is very important for the control of oxidation processes. Traditionally titrimetric procedures are used to monitor oxygenate formation, however, these titrimetric procedures are tedious and lack selectivity toward specific oxygenate classes in complex matrices. Comprehensive two-dimensional gas chromatography (GC×GC) is a way of increasing peak capacity for the comprehensive analysis of complex samples. Other groups have used HT-GC×GC to extend the carbon number range attainable by GC×GC and have optimised HT-GC×GC parameters for the separation of aromatics, nitrogen-containing compounds as well as sulphur-containing compounds in heavy petroleum fractions. HT-GC×GC column combinations for the separation of oxygenates in oxidised heavy paraffinic fractions are optimised in this study. The advantages of the HT-GC×GC method in the monitoring of the oxidation reactions of heavy paraffinic fraction samples are illustrated. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Comprehensive two-dimensional gas chromatography for determination of the terpenes profile of blue honeysuckle berries.

    Science.gov (United States)

    Kupska, Magdalena; Chmiel, Tomasz; Jędrkiewicz, Renata; Wardencki, Waldemar; Namieśnik, Jacek

    2014-01-01

    Terpenes are the main group of secondary metabolites, which play essential role in human. The establishment of the terpenes profile of berries of different blue honeysuckle cultivars was achieved by headspace solid-phase microextraction coupled with comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (HS-SPME/GC×GC-TOFMS). The berries were found to contain 44 terpenes identified by GC×GC-TOFMS. From these, 10 were previously reported in blueberries. According to their chemical structure, the compounds were organised in different groups: monoterpene hydrocarbons and monoterpene oxygen-containing compounds (oxides, alcohols, aldehydes, and ketones). Positive identification of some of the compounds was performed using authentic standards, while tentative identification of the compounds was based on deconvoluted mass spectra and comparison of linear retention indices (LRI) with literature values. The major components of volatile fraction were monoterpenes, such as eucalyptol, linalool and p-cymene. Furthermore, quantitative analysis showed that eucalyptol was the most abundant bioactive terpene in analysed berries (12.4-418.2 μg/L).

  13. Magnetic oscillations in two-dimensional Dirac systems and Shear viscosity and spin diffusion in a two-dimensional Fermi gas

    NARCIS (Netherlands)

    Küppersbusch, C.S.

    2015-01-01

    In the first part of the thesis I derive a full quantitative formula which describes the amplitude and frequency of magnetic oscillations in two-dimensional Dirac systems. The investigations are on the basis of graphene, but they generally also hold for other two-dimensional Dirac systems. Starting

  14. DISPLAY-2: a two-dimensional shallow layer model for dense gas dispersion including complex features.

    Science.gov (United States)

    Venetsanos, A G; Bartzis, J G; Würtz, J; Papailiou, D D

    2003-04-25

    A two-dimensional shallow layer model has been developed to predict dense gas dispersion, under realistic conditions, including complex features such as two-phase releases, obstacles and inclined ground. The model attempts to predict the time and space evolution of the cloud formed after a release of a two-phase pollutant into the atmosphere. The air-pollutant mixture is assumed ideal. The cloud evolution is described mathematically through the Cartesian, two-dimensional, shallow layer conservation equations for mixture mass, mixture momentum in two horizontal directions, total pollutant mass fraction (vapor and liquid) and mixture internal energy. Liquid mass fraction is obtained assuming phase equilibrium. Account is taken in the conservation equations for liquid slip and eventual liquid rainout through the ground. Entrainment of ambient air is modeled via an entrainment velocity model, which takes into account the effects of ground friction, ground heat transfer and relative motion between cloud and surrounding atmosphere. The model additionally accounts for thin obstacles effects in three ways. First a stepwise description of the obstacle is generated, following the grid cell faces, taking into account the corresponding area blockage. Then obstacle drag on the passing cloud is modeled by adding flow resistance terms in the momentum equations. Finally the effect of extra vorticity generation and entrainment enhancement behind obstacles is modeled by adding locally into the entrainment formula without obstacles, a characteristic velocity scale defined from the obstacle pressure drop and the local cloud height.The present model predictions have been compared against theoretical results for constant volume and constant flux gravity currents. It was found that deviations of the predicted cloud footprint area change with time from the theoretical were acceptably small, if one models the frictional forces between cloud and ambient air, neglecting the Richardson

  15. Programmed automation of modulator cold jet flow for comprehensive two-dimensional gas chromatographic analysis of vacuum gas oils.

    Science.gov (United States)

    Rathbun, Wayne

    2007-01-01

    A method is described for automating the regulation of cold jet flow of a comprehensive two-dimensional gas chromatograph (GCxGC) configured with flame ionization detection. This new capability enables the routine automated separation, identification, and quantitation of hydrocarbon types in petroleum fractions extending into the vacuum gas oil (VGO) range (IBP-540 degrees C). Chromatographic data acquisition software is programmed to precisely change the rate of flow from the cold jet of a nitrogen cooled loop modulator of a GCxGC instrument during sample analysis. This provides for the proper modulation of sample compounds across a wider boiling range. The boiling point distribution of the GCxGC separation is shown to be consistent with high temperature simulated distillation results indicating recovery of higher boiling semi-volatile VGO sample components. GCxGC configured with time-of-flight mass spectrometry is used to determine the molecular identity of individual sample components and boundaries of different molecular types.

  16. The Characteristics Method Applied to Stationary Two-Dimensional and Rotationally Symmetrical Gas Flows

    Science.gov (United States)

    Pfeiffer, F.; Meyer-Koenig, W.

    1949-01-01

    By means of characteristics theory, formulas for the numerical treatment of stationary compressible supersonic flows for the two-dimensional and rotationally symmetrical cases have been obtained from their differential equations.

  17. Two dimensional numerical simulation of gas discharges: comparison between particle-in-cell and FCT techniques

    Energy Technology Data Exchange (ETDEWEB)

    Soria-Hoyo, C; Castellanos, A [Departamento de Electronica y Electromagnetismo, Facultad de Fisica, Universidad de Sevilla, Avda. Reina Mercedes s/n, 41012 Sevilla (Spain); Pontiga, F [Departamento de Fisica Aplicada II, EUAT, Universidad de Sevilla, Avda. Reina Mercedes s/n, 41012 Sevilla (Spain)], E-mail: cshoyo@us.es

    2008-10-21

    Two different numerical techniques have been applied to the numerical integration of equations modelling gas discharges: a finite-difference flux corrected transport (FD-FCT) technique and a particle-in-cell (PIC) technique. The PIC technique here implemented has been specifically designed for the simulation of 2D electrical discharges using cylindrical coordinates. The development and propagation of a streamer between two parallel electrodes has been used as a convenient test to compare the performance of both techniques. In particular, the phase velocity of the cathode directed streamer has been used to check the internal consistency of the numerical simulations. The results obtained from the two techniques are in reasonable agreement with each other, and both techniques have proved their ability to follow the high gradients of charge density and electric field present in this type of problems. Moreover, the streamer velocities predicted by the simulation are in accordance with the typical experimental values.

  18. Allergic asthma exhaled breath metabolome: a challenge for comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    Caldeira, M; Perestrelo, R; Barros, A S; Bilelo, M J; Morête, A; Câmara, J S; Rocha, S M

    2012-09-07

    Allergic asthma represents an important public health issue, most common in the paediatric population, characterized by airway inflammation that may lead to changes in volatiles secreted via the lungs. Thus, exhaled breath has potential to be a matrix with relevant metabolomic information to characterize this disease. Progress in biochemistry, health sciences and related areas depends on instrumental advances, and a high throughput and sensitive equipment such as comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-ToFMS) was considered. GC×GC-ToFMS application in the analysis of the exhaled breath of 32 children with allergic asthma, from which 10 had also allergic rhinitis, and 27 control children allowed the identification of several hundreds of compounds belonging to different chemical families. Multivariate analysis, using Partial Least Squares-Discriminant Analysis in tandem with Monte Carlo Cross Validation was performed to assess the predictive power and to help the interpretation of recovered compounds possibly linked to oxidative stress, inflammation processes or other cellular processes that may characterize asthma. The results suggest that the model is robust, considering the high classification rate, sensitivity, and specificity. A pattern of six compounds belonging to the alkanes characterized the asthmatic population: nonane, 2,2,4,6,6-pentamethylheptane, decane, 3,6-dimethyldecane, dodecane, and tetradecane. To explore future clinical applications, and considering the future role of molecular-based methodologies, a compound set was established to rapid access of information from exhaled breath, reducing the time of data processing, and thus, becoming more expedite method for the clinical purposes.

  19. Thermodynamic-based retention time predictions of endogenous steroids in comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    Silva, Aline C A; Ebrahimi-Najafadabi, Heshmatollah; McGinitie, Teague M; Casilli, Alessandro; Pereira, Henrique M G; Aquino Neto, Francisco R; Harynuk, James J

    2015-05-01

    This work evaluates the application of a thermodynamic model to comprehensive two-dimensional gas chromatography (GC × GC) coupled with time-of-flight mass spectrometry for anabolic agent investigation. Doping control deals with hundreds of drugs that are prohibited in sports. Drug discovery in biological matrices is a challenging task that requires powerful tools when one is faced with the rapidly changing designer drug landscape. In this work, a thermodynamic model developed for the prediction of both primary and secondary retention times in GC × GC has been applied to trimethylsilylated hydroxyl (O-TMS)- and methoxime-trimethylsilylated carbonyl (MO-TMS)-derivatized endogenous steroids. This model was previously demonstrated on a pneumatically modulated GC × GC system, and is applied for the first time to a thermally modulated GC × GC system. Preliminary one-dimensional experiments allowed the calculation of thermodynamic parameters (ΔH, ΔS, and ΔC p ) which were successfully applied for the prediction of the analytes' interactions with the stationary phases of both the first-dimension column and the second-dimension column. The model was able to predict both first-dimension and second-dimension retention times with high accuracy compared with the GC × GC experimental measurements. Maximum differences of -8.22 s in the first dimension and 0.4 s in the second dimension were encountered for the O-TMS derivatives of 11β-hydroxyandrosterone and 11-ketoetiocholanolone, respectively. For the MO-TMS derivatives, the largest discrepancies were from testosterone (9.65 ) for the first-dimension retention times and 11-keto-etiocholanolone (0.4 s) for the second-dimension retention times.

  20. Reentrant resistance and giant Andreev back scattering in a two-dimensional electron gas coupled to superconductors

    NARCIS (Netherlands)

    den Hartog, Sander; Wees, B.J. van; Nazarov, Yu.V.; Klapwijk, T.M.; Borghs, G.

    1998-01-01

    We first present the bias-voltage dependence of the superconducting phase-dependent reduction in the differential resistance of a disordered T-shaped two-dimensional electron gas (2DEG) coupled to two superconductors. This reduction exhibits a reentrant behavior, since it first increases upon loweri

  1. Attempt to unravel the composition of toxaphene by comprehensive two-dimensional gas chromatography with selective detection

    NARCIS (Netherlands)

    Korytar, P.; Stee, van L.L.P.; Leonards, P.E.G.; Boer, de J.; Brinkman, U.A.Th.

    2003-01-01

    Comprehensive two-dimensional gas chromatography (GCxGC) coupled with micro electron-capture and time-of-flight mass spectrometric (TOF-MS) detection has been used to analyse technical toxaphene. An HP-1xHT-8 column combination yielded highly structured chromatograms and revealed a complex mixture o

  2. Four-terminal magnetoresistance of a two-dimensional electron-gas constriction in the ballistic regime

    NARCIS (Netherlands)

    Houten, H. van; Beenakker, C.W.J.; Loosdrecht, P.H.M. van; Thornton, T.J.; Ahmed, H.; Pepper, M.; Foxon, C.T.; Harris, J.J.

    1988-01-01

    A novel negative magnetoresistance effect is found in four-terminal measurements of the voltage drop across a short constriction of variable width in a high-mobility two-dimensional electron gas. The effect is interpreted as the suppression by a magnetic field of the geometrical constriction resista

  3. Classification of highly similar crude oils using data sets from comprehensive two-dimensional gas chromatography and multivariate techniques

    NARCIS (Netherlands)

    Mispelaar, V.G. van; Smilde, A.K.; Noord, O.E. de; Blomberg, J.; Schoenmakers, P.J.

    2005-01-01

    Comprehensive two-dimensional gas chromatography (GC × GC) has proven to be an extremely powerful separation technique for the analysis of complex volatile mixtures. This separation power can be used to discriminate between highly similar samples. In this article we will describe the use of GC × GC

  4. Integration of complementary circuits and two-dimensional electron gas in a Si/SiGe heterostructure

    Science.gov (United States)

    Lu, T. M.; Lee, C.-H.; Tsui, D. C.; Liu, C. W.

    2010-06-01

    We have realized complementary devices on an undoped Si/SiGe substrate where both two-dimensional electrons and holes can be induced capacitively. The design of the heterostructure and the fabrication process are reported. Magnetotransport measurements show that the induced two-dimensional electron gas exhibits the quantum Hall effect characteristics. A p-channel field-effect transistor is characterized and the operation of an inverter is demonstrated. The proof-of-principle experiment shows the feasibility of integrating complementary logic circuits with quantum devices.

  5. Two-dimensional electron gas in the regime of strong light-matter coupling: Dynamical conductivity and all-optical measurements of Rashba and Dresselhaus coupling

    Science.gov (United States)

    Yudin, Dmitry; Shelykh, Ivan A.

    2016-10-01

    A nonperturbative interaction of an electronic system with a laser field can substantially modify its physical properties. In particular, in two-dimensional (2D) materials with a lack of inversion symmetry, the achievement of a regime of strong light-matter coupling allows direct optical tuning of the strength of the Rashba spin-orbit interaction (SOI). Capitalizing on these results, we build a theory of the dynamical conductivity of a 2D electron gas with both Rashba and Dresselhaus SOIs coupled to an off-resonant high-frequency electromagnetic wave. We argue that strong light-matter coupling modifies qualitatively the dispersion of the electrons and can be used as a powerful tool to probe and manipulate the coupling strengths and adjust the frequency range where optical conductivity is essentially nonzero.

  6. A two-dimensional model for gas mixing in the upper dilute zone of a circulating fluidized bed

    Energy Technology Data Exchange (ETDEWEB)

    Kruse, M.; Schoenfelder, H.; Werther, J. [Technical University of Hamburg-Harburg, Hamburg (Germany)

    1995-10-01

    A two-dimensional two-phase flow model for gas/solid flow and gas mixing in the upper zone of a circulating fluidized bed is described. Continuous functions are used to describe variations of local flow parameters horizontally and vertically. Numerical values of dispersion parameters and interfacial mass transfer coefficients are derived from the results of tracer gas mixing experiments. There is good agreement between calculated and measured tracer gas profiles in the upper dilute zone of the circulating fluidized bed. The model is applicable to calculation of chemical reactions in CFB risers. 37 refs., 26 figs., 3 tabs.

  7. Doppler Velocimetry of Current Driven Spin Helices in a Two-Dimensional Electron Gas

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Luyi [Univ. of California, Berkeley, CA (United States)

    2013-05-17

    Spins in semiconductors provide a pathway towards the development of spin-based electronics. The appeal of spin logic devices lies in the fact that the spin current is even under time reversal symmetry, yielding non-dissipative coupling to the electric field. To exploit the energy-saving potential of spin current it is essential to be able to control it. While recent demonstrations of electrical-gate control in spin-transistor configurations show great promise, operation at room temperature remains elusive. Further progress requires a deeper understanding of the propagation of spin polarization, particularly in the high mobility semiconductors used for devices. This dissertation presents the demonstration and application of a powerful new optical technique, Doppler spin velocimetry, for probing the motion of spin polarization at the level of 1 nm on a picosecond time scale. We discuss experiments in which this technique is used to measure the motion of spin helices in high mobility n-GaAs quantum wells as a function of temperature, in-plane electric field, and photoinduced spin polarization amplitude. We find that the spin helix velocity changes sign as a function of wave vector and is zero at the wave vector that yields the largest spin lifetime. This observation is quite striking, but can be explained by the random walk model that we have developed. We discover that coherent spin precession within a propagating spin density wave is lost at temperatures near 150 K. This finding is critical to understanding why room temperature operation of devices based on electrical gate control of spin current has so far remained elusive. We report that, at all temperatures, electron spin polarization co-propagates with the high-mobility electron sea, even when this requires an unusual form of separation of spin density from photoinjected electron density. Furthermore, although the spin packet co-propagates with the two-dimensional electron gas, spin diffusion is strongly

  8. Three-body recombination in a quasi-two-dimensional quantum gas

    Science.gov (United States)

    Huang, Bo; Zenesini, Alessandro; Grimm, Rudolf

    2016-05-01

    Quantum three-body recombination in three-dimensional systems is influenced by a series of weakly bound trimers known as Efimov states, which are induced by short-range interactions and exhibit a discrete scaling symmetry. On the other hand, two-dimensional systems with contact interactions are characterized by continuous scale invariance and support no Efimov physics. This raises questions about the behaviour of three-body recombination in the transition from three to two dimensions. We use ultracold caesium atoms trapped in anisotropic potentials formed by a pair of counter-propagating laser beams to experimentally investigate three-body recombination in quasi-two-dimensional systems with tunable confinement and tunable interactions. In our recent experiments, we observed a smooth transition of the three-body recombination rate coefficient from a three-dimensional to a deeply quasi-two-dimensional system. A comparison between the results obtained near two Feshbach resonances indicates a universal behaviour of three-body recombination in the quasi-two-dimensional regime. Austrian Science Fund FWF within project P23106.

  9. Organophosphorus pesticide and ester analysis by using comprehensive two-dimensional gas chromatography with flame photometric detection

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiangping; Li, Dengkun; Li, Jiequan [Nanjing Centre for Disease Control and Prevention, Zizhulin Street, Gulou 210003, Nanjing (China); Rose, Gavin [Department of Environment and Primary Industries, Macleod Centre, Ernest Jones Drive, Macleod, Vic 3085 (Australia); Marriott, Philip J., E-mail: philip.marriott@monash.edu [Australian Centre for Research on Separation Science, School of Chemistry, Monash University, Wellington Road, Clayton 3800 (Australia)

    2013-12-15

    Highlights: • GC × GC-FPD(P-mode) was applied to detection of 37 phosphorus (P)-containing compounds. • The method improves resolution of P-compounds that coelute in the first dimension. • P-compounds are analyzed with excellent sensitivity supported by cryogenic modulation. • The FPD(P-mode) selectivity allows analysis in high hydrocarbon (H/C) matrix. • Soil samples and spiked chemical weapon compounds in H/C matrix are readily screened. -- Abstract: Thirty-seven phosphorus (P)-containing compounds comprising organophosphorus pesticides and organophosphate esters were analyzed by using comprehensive two-dimensional gas chromatography with flame photometric detection in P mode (GC × GC-FPD(P)), with a non-polar/moderately polar column set. A suitable modulation temperature and period was chosen based on experimental observation. A number of co-eluting peak pairs on the {sup 1}D column were well separated in 2D space. Excellent FPD(P) detection selectivity, responding to compounds containing the P atom, produces clear 2D GC × GC plots with little interference from complex hydrocarbon matrices. Limits of detection (LOD) were within the range of 0.0021–0.048 μmol L{sup −1}, and linear calibration correlation coefficients (R{sup 2}) for all 37 P-compounds were at least 0.998. The P-compounds were spiked in 2% diesel and good reproducibility for their response areas and retention times was obtained. Spiked recoveries were 88%–157% for 5 μg L{sup −1} and 80%–138% for 10 μg L{sup −1} spiked levels. Both {sup 1}t{sub R} and {sup 2}t{sub R} shifts were noted when the content of diesel was in excess of 5% in the matrix. Soil samples were analyzed by using the developed method; some P-compounds were positively detected. In general, this study shows that GC × GC-FPD(P) is an accurate, sensitive and simple method for P-compound analysis in complicated environmental samples.

  10. Complete elution of vacuum gas oil resins by comprehensive high-temperature two-dimensional gas chromatography.

    Science.gov (United States)

    Boursier, Laure; Souchon, Vincent; Dartiguelongue, Cyril; Ponthus, Jérémie; Courtiade, Marion; Thiébaut, Didier

    2013-03-08

    The development of efficient conversion processes requires extended knowledge on vacuum gas oils (VGOs). Among these processes, hydrocracking is certainly one of the best suited to meet the increasing demand on high quality diesel fuels. Most of refractory and inhibiting compounds towards hydrocracking and especially nitrogen containing compounds are contained in a fraction of the VGO called the resin fraction, which corresponds to the most polar fraction of a VGO obtained by liquid chromatography (LC) fractionation on a silica column. However, the lack of resolution observed through existing analytical methods does not allow a detailed characterization of these fractions. A recent study showed that comprehensive high temperature two-dimensional gas chromatography (HT-GC×GC) methods could be optimized in order to elute heavy compounds. This method was implemented for the analysis of VGO resin fractions and complete elution was reached. Firstly, the method was validated through repeatability, accuracy, linearity and response factors calculations. Four VGO resin fractions were analyzed and their HT-GC×GC simulated distillation curves were compared to their GC simulated distillation (GC-SimDist) curves. This comparison showed that the method allows complete elution of most of the analyzed VGO resin fractions. However, a detailed characterization of these fractions is not yet obtained due to the very large number of heteroatomic and aromatic species that a flame ionization detector can detect. Current work aims at increasing the selectivity of GC×GC by using heteroatom selective detectors in order to improve the characterization of such products.

  11. Collective modes of a two-dimensional spin-1/2 Fermi gas in a harmonic trap

    DEFF Research Database (Denmark)

    Baur, Stefan; Vogt, Enrico; Köhl, Michael

    2013-01-01

    We derive analytical expressions for the frequency and damping of the lowest collective modes of a two-dimensional Fermi gas using kinetic theory. For strong coupling, we furthermore show that pairing correlations overcompensate the effects of Pauli blocking on the collision rate for a large rang...... the experimental bounds results in a damping of the breathing mode which is comparable to what is observed, even for a scale-invariant system....

  12. Two-Dimensional Gas Chromatography-Mass Spectrometry to Determine Composition of the Pro ducts of Waste Tire Pyrolysis

    OpenAIRE

    Gertsiuk, M.M.; Kovalchuk, T.; Kapral, K.; Lysychenko, G.V.

    2014-01-01

    The method of two-dimensional gas chromatography cou pled with mass-spectrometry detection was used for determination of pyrolysis liquid — a mixture of pyrolysis products of waste tires. 6500 organic compounds have been identified: the saturated, unsaturated, aromatic hydrocarbons, the derivatives of thiophene, cyclic aminocompounds. By its composition pyrolytic liquid is close to the diesel fuel and can be used as the alternative fuel.

  13. Two-Dimensional Gas Chromatography-Mass Spectrometry to Determine Composition of the Pro ducts of Waste Tire Pyrolysis

    Directory of Open Access Journals (Sweden)

    Gertsiuk, M.M.

    2014-03-01

    Full Text Available The method of two-dimensional gas chromatography cou pled with mass-spectrometry detection was used for determination of pyrolysis liquid — a mixture of pyrolysis products of waste tires. 6500 organic compounds have been identified: the saturated, unsaturated, aromatic hydrocarbons, the derivatives of thiophene, cyclic aminocompounds. By its composition pyrolytic liquid is close to the diesel fuel and can be used as the alternative fuel.

  14. Mixed valence as a necessary criteria for quasi-two dimensional electron gas in oxide hetero-interfaces

    Science.gov (United States)

    Singh, Vijeta; Pulikkotil, J. J.

    2017-02-01

    The origin of quasi-two dimensional electron gas at the interface of polar-nonpolar oxide hetero-structure, such as LaAlO3/SrTiO3, is debated over electronic reconstruction and defects/disorder models. Common to these models is the partial valence transformation of substrate Ti ions from its equilibrium 4 + state to an itinerant 3 + state. Given that the Hf ions have a lower ionization potential than Ti due to the 4 f orbital screening, one would expect a hetero-interface conductivity in the polar-nonpolar LaAlO3/SrHfO3 system as well. However, our first principles calculations show the converse. Unlike the Ti3+ -Ti4+ valence transition which occur at a nominal energy cost, the barrier energy associated with its isoelectronic Hf3+ -Hf4+ counterpart is very high, hence suppressing the formation of quasi-two dimensional electron gas at LaAlO3/SrHfO3 hetero-interface. These calculations, therefore, emphasize on the propensity of mixed valence at the interface as a necessary condition for an oxide hetero-structure to exihibit quasi two-dimensional electron gas.

  15. Pseudogap Phenomena Near the BKT Transition of a Two-Dimensional Ultracold Fermi Gas in the Crossover Region

    Science.gov (United States)

    Matsumoto, M.; Hanai, R.; Inotani, D.; Ohashi, Y.

    2017-06-01

    We investigate strong-coupling properties of a two-dimensional ultracold Fermi gas in the normal phase. In the three-dimensional case, it has been shown that the so-called pseudogap phenomena can be well described by a (non-self-consistent) T-matrix approximation (TMA). In the two-dimensional case, while this strong-coupling theory can explain the pseudogap phenomenon in the strong-coupling regime, it unphysically gives large pseudogap size in the crossover region, as well as in the weak-coupling regime. We show that this difficulty can be overcome when one improves TMA to include higher-order pairing fluctuations within the framework of a self-consistent T-matrix approximation (SCTMA). The essence of this improvement is also explained. Since the observation of the BKT transition has recently been reported in a two-dimensional ^6{Li} Fermi gas, our results would be useful for the study of strong-coupling physics associated with this quasi-long-range order.

  16. Qualitative analysis of Copaifera oleoresin using comprehensive two-dimensional gas chromatography and gas chromatography with classical and cold electron ionisation mass spectrometry.

    Science.gov (United States)

    Wong, Yong Foo; Uekane, Thais M; Rezende, Claudia M; Bizzo, Humberto R; Marriott, Philip J

    2016-12-16

    Improved separation of both sesquiterpenes and diterpenic acids in Copaifera multijuga Hayne oleoresin, is demonstrated by using comprehensive two-dimensional gas chromatography (GC×GC) coupled to accurate mass time-of-flight mass spectrometry (accTOFMS). GC×GC separation employs polar phases (including ionic liquid phases) as the first dimension ((1)D) column, combined with a lower polarity (2)D phase. Elution temperatures (Te) of diterpenic acids (in methyl ester form, DAME) increased as the (1)D McReynolds' polarity value of the column phase decreased. Since Te of sesquiterpene hydrocarbons decreased with increased polarity, the very polar SLB-IL111 (1)D phase leads to excessive peak broadening in the (2)D apolar phase due to increased second dimension retention ((2)tR). The combination of SLB-IL59 with a nonpolar column phase was selected, providing reasonable separation and low Te for sesquiterpenes and DAME, compared to other tested column sets, without excessive (2)tR. Identities of DAME were aided by both soft (30eV) electron ionisation (EI) accurate mass TOFMS analysis and supersonic molecular beam ionisation (cold EI) TOFMS, both which providing less fragmentation and increased relative abundance of molecular ions. The inter-relation between EI energies, emission current, signal-to-noise and mass error for the accurate mass measurement of DAME are reported. These approaches can be used as a basis for conducting of GC×GC with soft EI accurate mass measurement of terpenes, particularly for unknown phytochemicals.

  17. Bound states in optical absorption of semiconductor quantum wells containing a two-dimensional electron Gas

    Science.gov (United States)

    Huard; Cox; Saminadayar; Arnoult; Tatarenko

    2000-01-01

    The dependence of the optical absorption spectrum of a semiconductor quantum well on two-dimensional electron concentration n(e) is studied using CdTe samples. The trion peak (X-) seen at low n(e) evolves smoothly into the Fermi edge singularity at high n(e). The exciton peak (X) moves off to high energy, weakens, and disappears. The X,X- splitting is linear in n(e) and closely equal to the Fermi energy plus the trion binding energy. For Cd0.998Mn0.002Te quantum wells in a magnetic field, the X,X- splitting reflects unequal Fermi energies for M = +/-1/2 electrons. The data are explained by Hawrylak's theory of the many-body optical response including spin effects.

  18. Strongly anisotropic spin-orbit splitting in a two-dimensional electron gas

    DEFF Research Database (Denmark)

    Michiardi, Matteo; Bianchi, Marco; Dendzik, Maciej

    2015-01-01

    Near-surface two-dimensional electron gases on the topological insulator Bi$_2$Te$_2$Se are induced by electron doping and studied by angle-resolved photoemission spectroscopy. A pronounced spin-orbit splitting is observed for these states. The $k$-dependent splitting is strongly anisotropic...... Rashba Hamiltonian. However, a $\\mathbf{k} \\cdot \\mathbf{p}$ model that includes the possibility of band structure anisotropy as well as both isotropic and anisotropic third order Rashba splitting can explain the results. The isotropic third order contribution to the Rashba Hamiltonian is found...... to be negative, reducing the energy splitting at high $k$. The interplay of band structure, higher order Rashba effect and tuneable doping offers the opportunity to engineer not only the size of the spin-orbit splitting but also its direction....

  19. Two-dimensional HRCT for monitoring postoperative results of the anterior cruciate ligament reconstruction. Zweidimensionale (2-D) CT-Arthrotomographie zur postoperativen Kontrolle einer neuen vorderen Kreuzbandplastik

    Energy Technology Data Exchange (ETDEWEB)

    Tosch, U.; Witt, H. (Freie Univ. Berlin (Germany, F.R.). Roentgendiagnostisches Zentralinstitut); Hertel, P.; Lais, E. (Freie Univ. Berlin (Germany, F.R.). Unfallchirurgische Klinik)

    1989-11-01

    Fifty-eight patients underwent intraarticular reconstruction of the anterior cruciate ligament. This was performed by using an autogenous transplant from the mid portion of the patellar ligament with a proximal and distal bone block, as described by Hertel. For comparison with the conventional X-ray examination, HRCT was performed to study the early postoperative results. In four patients (7%) dislocation of the bone block in the femoral condyle was seen. Two-dimensional reconstruction proved to be a satisfactory method for demonstration of the exact position of the autogenous transplant in both coronary and sagittal planes. (orig.).

  20. [Characterization of aromatic hydrocarbons in heavy gas oil using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry].

    Science.gov (United States)

    Guo, Kun; Zhou, Jian; Liu, Zelong

    2012-02-01

    An analytical method for separating and identifying the aromatic hydrocarbons in heavy gas oil using comprehensive two-dimensional gas chromatography (GC x GC) coupled to time-of-flight mass spectrometry (TOF MS) was established. The two-dimensional distribution by ring number of the aromatic hydrocarbons was obtained. Besides phenanthrene and methyl-phenanthrene, many other polycyclic aromatic hydrocarbons (PAHs) such as pyrene and benzo [a] anthracene were identified by using the retention times, standard mass spectra or literature reports. The method was successfully applied to the hydrotreating process of heavy gas oil and the hydrotreated products of phenanthrene, pyrene were identified. This method provided technical support for the characterization of aromatic hydrocarbons in heavy gas oil and the investigation of hydrogenation mechanism of polycyclic aromatic hydrocarbons. Compared with the conventional method, gas chromatography coupled to mass spectrometry (GC-MS), the GC x GC-TOF MS method illustrated the obvious advantages for heavy gas oil analysis.

  1. One-dimensional lattices topologically equivalent to two-dimensional lattices within the context of the lattice gas model

    Science.gov (United States)

    Costanza, E. F.; Costanza, G.

    2016-10-01

    Continuum partial differential equations are obtained from a set of discrete stochastic evolution equations of both non-Markovian and Markovian processes and applied to the diffusion within the context of the lattice gas model. A procedure allowing to construct one-dimensional lattices that are topologically equivalent to two-dimensional lattices is described in detail in the case of a rectangular lattice. This example shows the general features that possess the procedure and extensions are also suggested in order to provide a wider insight in the present approach.

  2. Optical probing of the metal-to-insulator transition in a two-dimensional high-mobility electron gas

    Energy Technology Data Exchange (ETDEWEB)

    Dionigi, F; Rossella, F; Bellani, V [Dipartimento di Fisica ' A Volta' and CNISM, Universita degli Studi di Pavia, 27100 Pavia (Italy); Amado, M [GISC and Departamento de Fisica de Materiales, Universidad Complutense, 28040 Madrid (Spain); Diez, E [Laboratorio de Bajas Temperaturas, Universidad de Salamanca, 37008 Salamanca (Spain); Kowalik, K [Laboratoire National des Champs Magnetiques Intenses, CNRS, 38042 Grenoble (France); Biasiol, G [Istituto Officina dei Materiali CNR, Laboratorio TASC, 34149 Trieste (Italy); Sorba, L, E-mail: vittorio.bellani@unipv.it [NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, 56126 Pisa (Italy)

    2011-06-15

    We study the quantum Hall liquid and the metal-insulator transition in a high-mobility two-dimensional electron gas, by means of photoluminescence and magnetotransport measurements. In the integer and fractional regime at {nu}>1/3, by analyzing the emission energy dispersion we probe the magneto-Coulomb screening and the hidden symmetry of the electron liquid. In the fractional regime above {nu}=1/3, the system undergoes metal-to-insulator transition, and in the insulating phase the dispersion becomes linear with evidence of an increased renormalized mass.

  3. Hole-Hole Interaction Effect in the Conductance of the Two-Dimensional Hole Gas in the Ballistic Regime

    OpenAIRE

    Proskuryakov, Y. Y.; Savchenko, A. K.; Safonov, S. S.; Pepper, M; Simmons, M.Y.; Ritchie, D. A.

    2001-01-01

    On a high mobility two-dimensional hole gas (2DHG) in a GaAs/GaAlAs heterostructure we study the interaction correction to the Drude conductivity in the ballistic regime, $k_BT\\tau /\\hbar $ $>1$. It is shown that the 'metallic' behaviour of the resistivity ($d\\rho /dT>0$) of the low-density 2DHG is caused by hole-hole interaction effect in this regime. We find that the temperature dependence of the conductivity and the parallel-field magnetoresistance are in agreement with this description, a...

  4. Metal Decoration Effects on the Gas-Sensing Properties of 2D Hybrid-Structures on Flexible Substrates

    Directory of Open Access Journals (Sweden)

    Byungjin Cho

    2015-09-01

    Full Text Available We have investigated the effects of metal decoration on the gas-sensing properties of a device with two-dimensional (2D molybdenum disulfide (MoS2 flake channels and graphene electrodes. The 2D hybrid-structure device sensitively detected NO2 gas molecules (>1.2 ppm as well as NH3 (>10 ppm. Metal nanoparticles (NPs could tune the electronic properties of the 2D graphene/MoS2 device, increasing sensitivity to a specific gas molecule. For instance, palladium NPs accumulate hole carriers of graphene/MoS2, electronically sensitizing NH3 gas molecules. Contrarily, aluminum NPs deplete hole carriers, enhancing NO2 sensitivity. The synergistic combination of metal NPs and 2D hybrid layers could be also applied to a flexible gas sensor. There was no serious degradation in the sensing performance of metal-decorated MoS2 flexible devices before/after 5000 bending cycles. Thus, highly sensitive and endurable gas sensor could be achieved through the metal-decorated 2D hybrid-structure, offering a useful route to wearable electronic sensing platforms.

  5. Metal Decoration Effects on the Gas-Sensing Properties of 2D Hybrid-Structures on Flexible Substrates.

    Science.gov (United States)

    Cho, Byungjin; Yoon, Jongwon; Lim, Sung Kwan; Kim, Ah Ra; Choi, Sun-Young; Kim, Dong-Ho; Lee, Kyu Hwan; Lee, Byoung Hun; Ko, Heung Cho; Hahm, Myung Gwan

    2015-09-25

    We have investigated the effects of metal decoration on the gas-sensing properties of a device with two-dimensional (2D) molybdenum disulfide (MoS₂) flake channels and graphene electrodes. The 2D hybrid-structure device sensitively detected NO₂ gas molecules (>1.2 ppm) as well as NH₃ (>10 ppm). Metal nanoparticles (NPs) could tune the electronic properties of the 2D graphene/MoS₂ device, increasing sensitivity to a specific gas molecule. For instance, palladium NPs accumulate hole carriers of graphene/MoS₂, electronically sensitizing NH₃ gas molecules. Contrarily, aluminum NPs deplete hole carriers, enhancing NO₂ sensitivity. The synergistic combination of metal NPs and 2D hybrid layers could be also applied to a flexible gas sensor. There was no serious degradation in the sensing performance of metal-decorated MoS₂ flexible devices before/after 5000 bending cycles. Thus, highly sensitive and endurable gas sensor could be achieved through the metal-decorated 2D hybrid-structure, offering a useful route to wearable electronic sensing platforms.

  6. Magnetocapacitance oscillations and thermoelectric effect in a two-dimensional electron gas irradiated by microwaves

    Science.gov (United States)

    Levin, A. D.; Gusev, G. M.; Raichev, O. E.; Momtaz, Z. S.; Bakarov, A. K.

    2016-07-01

    To study the influence of microwave irradiation on two-dimensional electrons, we apply a method based on capacitance measurements in GaAs quantum well samples where the gate covers a central part of the layer. We find that the capacitance oscillations at high magnetic fields, caused by the oscillations of thermodynamic density of states, are not essentially modified by microwaves. However, in the region of fields below 1 T, we observe another set of oscillations, with the period and the phase identical to those of microwave-induced resistance oscillations. The phenomenon of microwave-induced capacitance oscillations is explained in terms of violation of the Einstein relation between conductivity and the diffusion coefficient in the presence of microwaves, which leads to a dependence of the capacitor charging on the anomalous conductivity. We also observe microwave-induced oscillations in the capacitive response to periodic variations of external heating. These oscillations appear due to the thermoelectric effect and are in antiphase with microwave-induced resistance oscillations because of the Corbino-like geometry of our experimental setup.

  7. Observation of mesoscopic crystalline structures in a two-dimensional Rydberg gas

    CERN Document Server

    Schauß, Peter; Endres, Manuel; Fukuhara, Takeshi; Hild, Sebastian; Omran, Ahmed; Pohl, Thomas; Gross, Christian; Kuhr, Stefan; Bloch, Immanuel

    2012-01-01

    The ability to control and tune interactions in ultracold atomic gases has paved the way towards the realization of new phases of matter. Whereas experiments have so far achieved a high degree of control over short-ranged interactions, the realization of long-range interactions would open up a whole new realm of many-body physics and has become a central focus of research. Rydberg atoms are very well-suited to achieve this goal, as the van der Waals forces between them are many orders of magnitude larger than for ground state atoms. Consequently, the mere laser excitation of ultracold gases can cause strongly correlated many-body states to emerge directly when atoms are transferred to Rydberg states. A key example are quantum crystals, composed of coherent superpositions of different spatially ordered configurations of collective excitations. Here we report on the direct measurement of strong correlations in a laser excited two-dimensional atomic Mott insulator using high-resolution, in-situ Rydberg atom imag...

  8. Two-Dimensional Riemann Solver for Euler Equations of Gas Dynamics

    Science.gov (United States)

    Brio, M.; Zakharian, A. R.; Webb, G. M.

    2001-02-01

    We construct a Riemann solver based on two-dimensional linear wave contributions to the numerical flux that generalizes the one-dimensional method due to Roe (1981, J. Comput. Phys.43, 157). The solver is based on a multistate Riemann problem and is suitable for arbitrary triangular grids or any other finite volume tessellations of the plane. We present numerical examples illustrating the performance of the method using both first- and second-order-accurate numerical solutions. The numerical flux contributions are due to one-dimensional waves and multidimensional waves originating from the corners of the computational cell. Under appropriate CFL restrictions, the contributions of one-dimensional waves dominate the flux, which explains good performance of dimensionally split solvers in practice. The multidimensional flux corrections increase the accuracy and stability, allowing a larger time step. The improvements are more pronounced on a coarse mesh and for large CFL numbers. For the second-order method, the improvements can be comparable to the improvements resulting from a less diffusive limiter.

  9. Analysis of branched DNA replication and recombination intermediates from prokaryotic cells by two-dimensional (2D) native-native agarose gel electrophoresis.

    Science.gov (United States)

    Robinson, Nicholas P

    2013-01-01

    Branched DNA molecules are generated by the essential processes of replication and recombination. Owing to their distinctive extended shapes, these intermediates migrate differently from linear double-stranded DNA under certain electrophoretic conditions. However, these branched species exist in the cell at much low abundance than the bulk linear DNA. Consequently, branched molecules cannot be visualized by conventional electrophoresis and ethidium bromide staining. Two-dimensional native-native agarose electrophoresis has therefore been developed as a method to facilitate the separation and visualization of branched replication and recombination intermediates. A wide variety of studies have employed this technique to examine branched molecules in eukaryotic, archaeal, and bacterial cells, providing valuable insights into how DNA is duplicated and repaired in all three domains of life.

  10. Mechanism to generate a two-dimensional electron gas at the surface of the charge-ordered semiconductor BaBiO3.

    Science.gov (United States)

    Vildosola, Verónica; Güller, Francisco; Llois, Ana María

    2013-05-17

    In this Letter, we find by means of first-principles calculations a new physical mechanism to generate a two-dimensional electron gas, namely, the breaking of charge ordering at the surface of a charge-ordered semiconductor due to the incomplete oxygen environment of the surface ions. The emergence of the 2D gas is independent of the presence of oxygen vacancies or polar discontinuities; this is a self-doping effect. This mechanism might apply to many charge-ordered systems, in particular, we study the case of BaBiO(3)(001). Our calculations show that the outer layer of the Bi-terminated simulated surface turns more cubiclike and metallic while the inner layers remain in the insulating monoclinic state that the system present in the bulk form. On the other hand, the metallization does not occur for the Ba termination, a fact that makes this system appealing for nanostructuring. Finally, in view of the bulk properties of this material under doping, this particular finding sets another possible route for future exploration: the potential scenario of 2D superconductivity at the BaBiO(3) surface.

  11. Ballistic and diffusive dynamics in a two-dimensional ideal gas of macroscopic chaotic Faraday waves.

    Science.gov (United States)

    Welch, Kyle J; Hastings-Hauss, Isaac; Parthasarathy, Raghuveer; Corwin, Eric I

    2014-04-01

    We have constructed a macroscopic driven system of chaotic Faraday waves whose statistical mechanics, we find, are surprisingly simple, mimicking those of a thermal gas. We use real-time tracking of a single floating probe, energy equipartition, and the Stokes-Einstein relation to define and measure a pseudotemperature and diffusion constant and then self-consistently determine a coefficient of viscous friction for a test particle in this pseudothermal gas. Because of its simplicity, this system can serve as a model for direct experimental investigation of nonequilibrium statistical mechanics, much as the ideal gas epitomizes equilibrium statistical mechanics.

  12. Quantum Oscillations in an Interfacial 2D Electron Gas.

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Bingop [Zhejiang Univ., Hangzhou (China); Lu, Ping [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Liu, Henan [Univ. of North Carolina, Charlotte, NC (United States); Lin, Jiao [Zhejiang Univ., Hangzhou (China); Ye, Zhenyu [Zhejiang Univ., Hangzhou (China); Jaime, Marcelo [Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab. (MagLab); Balakirev, Fedor F. [Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab. (MagLab); Yuan, Huiqiu [Zhejiang Univ., Hangzhou (China); Wu, Huizhen [Zhejiang Univ., Hangzhou (China); Pan, Wei [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Zhang, Yong [Univ. of North Carolina, Charlotte, NC (United States)

    2016-01-01

    Recently, it has been predicted that topological crystalline insulators (TCIs) may exist in SnTe and Pb1-xSnxTe thin films [1]. To date, most studies on TCIs were carried out either in bulk crystals or thin films, and no research activity has been explored in heterostructures. We present here the results on electronic transport properties of the 2D electron gas (2DEG) realized at the interfaces of PbTe/ CdTe (111) heterostructures. Evidence of topological state in this interfacial 2DEG was observed.

  13. STUDY OF AXIAL VELOCITY IN GAS CYCLONES BY 2D-PIV, 3D-PIY, AND SIMULATION

    Institute of Scientific and Technical Information of China (English)

    Zhengliang Liu; Jinyu Jiao; Ying Zheng

    2006-01-01

    The axial velocity distribution in a gas cyclone has been examined with two-dimensional particle image velocimetry (2D-PIV) and three-dimensional particle image velocimetry (3D-PIV) experiments in this study. Due to the limitation of 2D-PIV configuration, the contamination generated by the strong tangential velocity in the cyclone can be registered in the axial velocity detected by 2D-PIV. Efficient methods are proposed in this work to remove this contamination. The contamination-removed 2D-PIV data agree well with 3D-PIV results. The distributions of the axial velocity are also computed by the Reynolds stress model (RSM) and verified using the PIV experimental results. Reasonable agreements are obtained.

  14. Application of highly sensitive fluorescent dyes (CyDye DIGE Fluor saturation dyes) to laser microdissection and two-dimensional difference gel electrophoresis (2D-DIGE) for cancer proteomics.

    Science.gov (United States)

    Kondo, Tadashi; Hirohashi, Setsuo

    2006-01-01

    Proteome data combined with histopathological information provides important, novel clues for understanding cancer biology and reveals candidates for tumor markers and therapeutic targets. We have established an application of a highly sensitive fluorescent dye (CyDye DIGE Fluor saturation dye), developed for two-dimensional difference gel electrophoresis (2D-DIGE), to the labeling of proteins extracted from laser microdissected tissues. The use of the dye dramatically decreases the protein amount and, in turn, the number of cells required for 2D-DIGE; the cells obtained from a 1 mm2 area of an 8-12 microm thick tissue section generate up to 5,000 protein spots in a large-format 2D gel. This protocol allows the execution of large-scale proteomics in a more efficient, accurate and reproducible way. The protocol can be used to examine a single sample in 5 d or to examine hundreds of samples in large-scale proteomics.

  15. Analysis of cave atmospheres by comprehensive two-dimensional gas chromatography (GC×GC with flame ionization detection (FID

    Directory of Open Access Journals (Sweden)

    Ryan C. Blase

    2015-03-01

    Full Text Available In this paper, we describe a simple method for sampling, pre-concentrating, and separating volatile and semi-volatile components from two different cave atmospheres. Sampling is performed by capturing a volume of cave atmosphere in a Tedlar bag or Suma canister for sample storage and transport back to the laboratory. Loading a portion of the sample on a multi-bed sorption trap allows for sample pre-concentration prior to separation and detection of components on a comprehensive two-dimensional gas chromatograph (GC×GC. Comparison of two Texas caves reveals the power of comprehensive two-dimensional gas chromatography (GC×GC for volatile separation and detection, and to our knowledge marks the first use of GC×GC for the analysis of cave atmospheres. Analysis of the results revealed 138 and 146 chromatographic signals over an S/N threshold of 500 and direct comparison of the two samples revealed 50 identical chromatographic signals. This study is a first step toward demonstrating the ability of GC×GC to separate the complex volatiles and semi-volatiles in the cave atmosphere as a fingerprinting tool.

  16. JAC2D: A two-dimensional finite element computer program for the nonlinear quasi-static response of solids with the conjugate gradient method; Yucca Mountain Site Characterization Project

    Energy Technology Data Exchange (ETDEWEB)

    Biffle, J.H.; Blanford, M.L.

    1994-05-01

    JAC2D is a two-dimensional finite element program designed to solve quasi-static nonlinear mechanics problems. A set of continuum equations describes the nonlinear mechanics involving large rotation and strain. A nonlinear conjugate gradient method is used to solve the equations. The method is implemented in a two-dimensional setting with various methods for accelerating convergence. Sliding interface logic is also implemented. A four-node Lagrangian uniform strain element is used with hourglass stiffness to control the zero-energy modes. This report documents the elastic and isothermal elastic/plastic material model. Other material models, documented elsewhere, are also available. The program is vectorized for efficient performance on Cray computers. Sample problems described are the bending of a thin beam, the rotation of a unit cube, and the pressurization and thermal loading of a hollow sphere.

  17. Comprehensive two-dimensional gas chromatography for characterizing mineral oils in foods and distinguishing them from synthetic hydrocarbons.

    Science.gov (United States)

    Biedermann, Maurus; Grob, Koni

    2015-01-02

    Many foods are contaminated by hydrocarbons of mineral oil or synthetic origin. High performance liquid chromatography on-line coupled with gas chromatography and flame ionization detection (HPLC-GC-FID) is a powerful tool for the quantitative determination, but it would often be desirable to obtain more information about the type of hydrocarbons in order to identify the source of the contamination and specify pertinent legislation. Comprehensive two-dimensional gas chromatography (GC×GC) is shown to produce plots distinguishing mineral oil saturated hydrocarbons (MOSH) from polymer oligomeric saturated hydrocarbons (POSH) and characterizing the degree of raffination of a mineral oil. The first dimension separation occurred on a phenyl methyl polysiloxane, the second on a dimethyl polysiloxane. Mass spectrometry (MS) was used for identification, FID for quantitative determination. This shows the substantial advances in chromatography to characterize complex hydrocarbon mixtures even as contaminants in food.

  18. Quantum anomaly, universal relations, and breathing mode of a two-dimensional Fermi gas.

    Science.gov (United States)

    Hofmann, Johannes

    2012-05-01

    In this Letter, we show that the classical SO(2,1) symmetry of a harmonically trapped Fermi gas in two dimensions is broken by quantum effects. The anomalous correction to the symmetry algebra is given by a two-body operator that is well known as the contact. Taking into account this modification, we are able to derive the virial theorem for the system and a universal relation for the pressure of a homogeneous gas. The existence of an undamped breathing mode is associated with the classical symmetry. We provide an estimate for the anomalous frequency shift of this oscillation at zero temperature and compare the result with a recent experiment by [E. Vogt et al., Phys. Rev. Lett. 108, 070404 (2012)]. Discrepancies are attributed to finite temperature effects.

  19. Evolution of the vortex state in the BCS-BEC crossover of a quasi two-dimensional superfluid Fermi gas

    Science.gov (United States)

    Luo, Xuebing; Zhou, Kezhao; Zhang, Zhidong

    2016-11-01

    We use the path-integral formalism to investigate the vortex properties of a quasi-two dimensional (2D) Fermi superfluid system trapped in an optical lattice potential. Within the framework of mean-field theory, the cooper pair density, the atom number density, and the vortex core size are calculated from weakly interacting BCS regime to strongly coupled while weakly interacting BEC regime. Numerical results show that the atoms gradually penetrate into the vortex core as the system evolves from BEC to BCS regime. Meanwhile, the presence of the optical lattice allows us to analyze the vortex properties in the crossover from three-dimensional (3D) to 2D case. Furthermore, using a simple re-normalization procedure, we find that the two-body bound state exists only when the interaction is stronger than a critical one denoted by G c which is obtained as a function of the lattice potential’s parameter. Finally, we investigate the vortex core size and find that it grows with increasing interaction strength. In particular, by analyzing the behavior of the vortex core size in both BCS and BEC regimes, we find that the vortex core size behaves quite differently for positive and negative chemical potentials. Project supported by the National Natural Science Foundation of China (Grant Nos. 51331006, 51590883, and 11204321) and the Project of Chinese Academy of Sciences (Grant No. KJZD-EW-M05-3).

  20. Conductivity of the two-dimensional electron gas at LaAlO3/SrTiO3 interface

    Science.gov (United States)

    Kirichenko, E. V.; Stephanovich, V. A.; Dugaev, V. K.

    2017-02-01

    We propose an analytical theory of metallic conductivity in the two-dimensional (2D) LaAlO3/SrTiO3 (LAO/STO) interface. For that we consider the electron-phonon interaction at the interface. The electronic part is taken from our previous work [Phys. Chem. Chem. Phys. 18, 2104 (2016), 10.1039/C5CP06627A], considering the conditions for the interfacial charge carrier (electron or hole) to become itinerant. The second ingredient deals with the atomic oscillations localized near the interface and decaying rapidly at its both sides, which can be regarded as 2D acoustic phonons. The dispersion of such phonons depends on the characteristics of phonon spectra of LAO and STO. Calculating the corresponding scattering rate by Fermi's golden rule, we show that the resulting resistivity (i.e., inverse conductivity) has typical metallic character, growing linearly with temperature and tending to zero (without defects forming so-called residual resistivity) at T →0 . The results of our calculations are in agreement with available experimental data.

  1. Partial least squares analysis of rocket propulsion fuel data using diaphragm valve-based comprehensive two-dimensional gas chromatography coupled with flame ionization detection.

    Science.gov (United States)

    Freye, Chris E; Fitz, Brian D; Billingsley, Matthew C; Synovec, Robert E

    2016-06-01

    The chemical composition and several physical properties of RP-1 fuels were studied using comprehensive two-dimensional (2D) gas chromatography (GC×GC) coupled with flame ionization detection (FID). A "reversed column" GC×GC configuration was implemented with a RTX-wax column on the first dimension ((1)D), and a RTX-1 as the second dimension ((2)D). Modulation was achieved using a high temperature diaphragm valve mounted directly in the oven. Using leave-one-out cross-validation (LOOCV), the summed GC×GC-FID signal of three compound-class selective 2D regions (alkanes, cycloalkanes, and aromatics) was regressed against previously measured ASTM derived values for these compound classes, yielding root mean square errors of cross validation (RMSECV) of 0.855, 0.734, and 0.530mass%, respectively. For comparison, using partial least squares (PLS) analysis with LOOCV, the GC×GC-FID signal of the entire 2D separations was regressed against the same ASTM values, yielding a linear trend for the three compound classes (alkanes, cycloalkanes, and aromatics), yielding RMSECV values of 1.52, 2.76, and 0.945 mass%, respectively. Additionally, a more detailed PLS analysis was undertaken of the compounds classes (n-alkanes, iso-alkanes, mono-, di-, and tri-cycloalkanes, and aromatics), and of physical properties previously determined by ASTM methods (such as net heat of combustion, hydrogen content, density, kinematic viscosity, sustained boiling temperature and vapor rise temperature). Results from these PLS studies using the relatively simple to use and inexpensive GC×GC-FID instrumental platform are compared to previously reported results using the GC×GC-TOFMS instrumental platform.

  2. Direct Imaging of Charge Density Modulation in Switchable Two-Dimensional Electron Gas at the Oxide Hetero-Interfaces by Using Electron Bean Inline Holography

    Science.gov (United States)

    2015-08-16

    SUPPLEMENTARY NOTES 14. ABSTRACT The recent discovery of a two-dimensional electron gas (2DEG) at the interface between insulating perovskite ...3/10/2015 Abstract The recent discovery of a two-dimensional electron gas (2DEG) at the interface between insulating perovskite oxides SrTiO3...associated charge distributions in semiconductor materials, and therefore regarded as the only tool that can completely visualize the spatial

  3. Upgrade of PARC2D to include real gas effects. [computer program for flowfield surrounding aeroassist flight experiment

    Science.gov (United States)

    Saladino, Anthony; Praharaj, Sarat C.; Collins, Frank G.; Seaford, C. Mark

    1990-01-01

    This paper presents a description of the changes and additions to the perfect gas PARC2D code to include chemical equilibrium effects, resulting in a code called PARCEQ2D. The work developed out of a need to have the capability of more accurately representing the flowfield surrounding the aeroassist flight experiment (AFE) vehicle. Use is made of the partition function of statistical mechanics in the evaluation of the thermochemical properties. This approach will allow the PARC code to be extended to thermal nonequilibrium when this task is undertaken in the future. The transport properties follow from formulae from the kinetic theory of gases. Results are presented for a two-dimensional AFE that compare perfect gas and real gas solutions at flight conditions, showing vast differences between the two cases.

  4. A high density two-dimensional electron gas in an oxide heterostructure on Si (001

    Directory of Open Access Journals (Sweden)

    E. N. Jin

    2014-11-01

    Full Text Available We present the growth and characterization of layered heterostructures comprised of LaTiO3 and SrTiO3 epitaxially grown on Si (001. Magnetotransport measurements show that the sheet carrier densities of the heterostructures scale with the number of LaTiO3/SrTiO3 interfaces, consistent with the presence of an interfacial 2-dimensional electron gas (2DEG at each interface. Sheet carrier densities of 8.9 × 1014 cm−2 per interface are observed. Integration of such high density oxide 2DEGs on silicon provides a bridge between the exceptional properties and functionalities of oxide 2DEGs and microelectronic technologies.

  5. A scintillating gas detector for 2D dose measurements in clinical carbon beams.

    Science.gov (United States)

    Seravalli, E; de Boer, M; Geurink, F; Huizenga, J; Kreuger, R; Schippers, J M; van Eijk, C W E; Voss, B

    2008-09-07

    A two-dimensional position sensitive dosimetry system based on a scintillating gas detector has been developed for pre-treatment verification of dose distributions in hadron therapy. The dosimetry system consists of a chamber filled with an Ar/CF4 scintillating gas mixture, inside which two cascaded gas electron multipliers (GEMs) are mounted. A GEM is a thin kapton foil with copper cladding structured with a regular pattern of sub-mm holes. The primary electrons, created in the detector's sensitive volume by the incoming beam, drift in an electric field towards the GEMs and undergo gas multiplication in the GEM holes. During this process, photons are emitted by the excited Ar/CF4 gas molecules and detected by a mirror-lens-CCD camera system. Since the amount of emitted light is proportional to the dose deposited in the sensitive volume of the detector by the incoming beam, the intensity distribution of the measured light spot is proportional to the 2D hadron dose distribution. For a measurement of a 3D dose distribution, the scintillating gas detector is mounted at the beam exit side of a water-bellows phantom, whose thickness can be varied in steps. In this work, the energy dependence of the output signal of the scintillating gas detector has been verified in a 250 MeV/u clinical 12C ion beam by means of a depth-dose curve measurement. The underestimation of the measured signal at the Bragg peak depth is only 9% with respect to an air-filled ionization chamber. This is much smaller than the underestimation found for a scintillating Gd2O2S:Tb ('Lanex') screen under the same measurement conditions (43%). Consequently, the scintillating gas detector is a promising device for verifying dose distributions in high LET beams, for example to check hadron therapy treatment plans which comprise beams with different energies.

  6. Development and Design of a Single-Stage Cryogenic Modulator for Comprehensive Two-Dimensional Gas Chromatography.

    Science.gov (United States)

    Mostafa, Ahmed; Górecki, Tadeusz

    2016-05-17

    A new liquid nitrogen-based single-stage cryogenic modulator was developed and characterized. In addition, a dedicated liquid nitrogen delivery system was developed. A well-defined restriction placed inside a deactivated fused silica capillary was used to increase the cooling surface area and provide very efficient trapping. At the same time, it enabled modulation of the carrier gas flow owing to changes in gas viscosity with temperature. Gas flow is almost unimpeded at the trapping temperature but reduced to nearly zero at the desorption temperature, which prevents analyte breakthrough. Peak widths for n-alkanes of 30-40 ms at half height were obtained. Most importantly, even the solvent peak could be modulated, which is not feasible with any commercially available thermal modulator. Evaluation of the newly developed system in two-dimensional gas chromatography (GC × GC) separations of some real samples such as regular gasoline and diesel fuel showed that the analytical performance of this single-stage modulator is fully competitive to those of the more complicated dual-stage modulators.

  7. Comprehensive two-dimensional gas chromatography combined to multivariate data analysis for detection of disease-resistant clones of Eucalyptus.

    Science.gov (United States)

    Hantao, Leandro Wang; Toledo, Bruna Regina; Ribeiro, Fabiana Alves de Lima; Pizetta, Marilia; Pierozzi, Caroline Geraldi; Furtado, Edson Luiz; Augusto, Fabio

    2013-11-15

    In this paper it is reported the use of the chromatographic profiles from volatile fractions of plant clones - in this case, hybrids of Eucalyptus grandis×Eucalyptus urophylla - to determine specimens susceptible to rust disease. The analytes were isolated by headspace solid phase microextraction (HS-SPME) and analyzed by comprehensive two-dimensional gas chromatography combined to fast quadrupole mass spectrometry (GC×GC-qMS). Parallel Factor Analysis (PARAFAC) was employed for estimate the correlation between the chromatographic profiles and resistance against Eucalyptus rust, after preliminary variable selection performed by Fisher ratio analysis. The proposed method allowed the differentiation between susceptible and non-susceptible clones and determination of three resistance biomarkers. This approach can be a valuable alternative for the otherwise time-consuming and labor-intensive methods commonly used.

  8. Liquid-Gated High Mobility and Quantum Oscillation of the Two-Dimensional Electron Gas at an Oxide Interface.

    Science.gov (United States)

    Zeng, Shengwei; Lü, Weiming; Huang, Zhen; Liu, Zhiqi; Han, Kun; Gopinadhan, Kalon; Li, Changjian; Guo, Rui; Zhou, Wenxiong; Ma, Haijiao Harsan; Jian, Linke; Venkatesan, Thirumalai; Ariando

    2016-04-26

    Electric field effect in electronic double layer transistor (EDLT) configuration with ionic liquids as the dielectric materials is a powerful means of exploring various properties in different materials. Here, we demonstrate the modulation of electrical transport properties and extremely high mobility of two-dimensional electron gas at LaAlO3/SrTiO3 (LAO/STO) interface through ionic liquid-assisted electric field effect. With a change of the gate voltages, the depletion of charge carrier and the resultant enhancement of electron mobility up to 19 380 cm(2)/(V s) are realized, leading to quantum oscillations of the conductivity at the LAO/STO interface. The present results suggest that high-mobility oxide interfaces, which exhibit quantum phenomena, could be obtained by ionic liquid-assisted field effect.

  9. Effect of In Composition on Two-Dimensional Electron Gas in Wurtzite AlGaN/InGaN Heterostructures

    Institute of Scientific and Technical Information of China (English)

    KIM Bong-Hwan; PARK Seoung-Hwan; LEE Jung-Hee; MOON Yong-Tae

    2010-01-01

    @@ The effect of In composition on two-dimensional electron gas in wurtzite AIGaN/InGaN heterostructures is theoretically investigated.The sheet carrier density is shown to increase nearly linearly with In mole fraction x,due to the increase in the polarization charge at the AlGaN/InGaN interface.The electron sheet density is enhanced with the doping in the AlGaN layer.The sheet carrier density is as high as 3.7 × 1013 cm-2 at the donor density of 10 x 1018 cm-3 for the HEMT structure with x = 0.3.The contribution of additional donor density on the electron sheet density is nearly independent of the In mole fraction.

  10. Hole-hole interaction effect in the conductance of the two-dimensional hole gas in the ballistic regime.

    Science.gov (United States)

    Proskuryakov, Y Y; Savchenko, A K; Safonov, S S; Pepper, M; Simmons, M Y; Ritchie, D A

    2002-08-12

    On a high-mobility two-dimensional hole gas (2DHG) in a GaAs/GaAlAs heterostructure we study the interaction correction to the Drude conductivity in the ballistic regime, k(B)Ttau/ variant Planck's over 2pi >1. It is shown that the "metallic" behavior of the resistivity (drho/dT>0) of the low-density 2DHG is caused by the hole-hole interaction effect in this regime. We find that the temperature dependence of the conductivity and the parallel-field magnetoresistance are in agreement with this description, and determine the Fermi-liquid interaction constant Fsigma0 which controls the sign of drho/dT.

  11. Development of an ultra-fast data-acquisition system for a two-dimensional microstrip gas chamber.

    Science.gov (United States)

    Ochi, A; Tanimori, T; Nishi, Y; Aoki, S; Nishi, Y

    1998-05-01

    A high-performance data-acquisition system has been developed in order to obtain time-resolved sequential images from a two-dimensional microstrip gas chamber (MSGC). This was achieved using fully digital processing with a synchronized pipeline method. Complex logical circuits for processing large numbers of signals are mounted on a small number of complex programmable logic devices. The system is operated with a 10 MHz synchronous clock, and has the capability of handling more than 3 x 10(6) counts s(-1) for asynchronous events. The system was examined using a 5 x 5 cm MSGC and the recently developed 10 x 10 cm MSGC (1024 outputs); the anticipated performances were achieved.

  12. Bound states of a negative test charge due to many-body effects in the two-dimensional electron gas

    Science.gov (United States)

    Ghazali, A.; Gold, A.

    1995-12-01

    Bound states of a negative test electron in the low-density regime of the two-dimensional electron gas are obtained when many-body effects (exchange and correlation) are incorporated in the screening function via the local-field correction. Using the Green's-function method and a variational method we determine the energies and the wave functions of the ground state and the excited states as functions of the electron density. For high electron density no bound state is found. Below a critical density the number and the energy of bound states increase with decreasing electron density. The ground state is described by the wave function ψ2s~r exp(-r/α).

  13. Determining indicator toxaphene congeners in soil using comprehensive two-dimensional gas chromatography-tandem mass spectrometry.

    Science.gov (United States)

    Zhu, Shuai; Gao, Lirong; Zheng, Minghui; Liu, Huimin; Zhang, Bing; Liu, Lidan; Wang, Yiwen

    2014-01-01

    Toxaphene, which is a broad spectrum chlorinated pesticide, is a complex mixture of several hundred congeners, mainly polychlorinated bornanes. Quantifying toxaphene in environmental samples is difficult because of its complexity, and because each congener has a different response factor. Toxaphene chromatograms acquired using one-dimensional gas chromatography (1DGC) show that this technique cannot be used to separate all of the toxaphene congeners. We developed and validated a sensitive and quantitative method for determining three indicator toxaphene congeners in soil using an isotope dilution/comprehensive two-dimensional gas chromatography-tandem mass spectrometry (GC × GC-MS). The samples were extracted using accelerated solvent extraction, and then the extracts were purified using silica gel columns. (13)C₁₀-labeled Parlar 26 and 50 were used as internal standards and (13)C₁₀-labeled Parlar 62 was used as an injection standard. The sample extraction and purification treatments and the GC × GC-MS parameters were optimized. Subsequently the samples were determined by GC × GC-MS. The limits of detection for Parlar 26, 50, and 62 were 0.6 pg/g, 0.4 pg/g, and 1.0 pg/g (S/N=3), respectively, and the calibration curves had good linear correlations between 50 and 1000 μg/L (r(2)>0.99). Comprehensive two-dimensional GC gave substantial improvements over one-dimensional GC in the toxaphene analysis. We analyzed soil samples containing trace quantities of toxaphene to demonstrate that the developed method could be used to analyze toxaphene in environmental samples.

  14. Interplay between Rashba spin-orbit coupling and adiabatic rotation in a two-dimensional Fermi gas

    Science.gov (United States)

    Doko, E.; Subaşı, A. L.; Iskin, M.

    2017-01-01

    We explore the trap profiles of a two-dimensional atomic Fermi gas in the presence of a Rashba spin-orbit coupling and under an adiabatic rotation. We first consider a noninteracting gas and show that the competition between the effects of Rashba coupling on the local density of single-particle states and the Coriolis effects caused by rotation gives rise to a characteristic ring-shaped density profile that survives at experimentally accessible temperatures. Furthermore, Rashba splitting of the Landau levels gives the density profiles a ziggurat shape in the rapid-rotation limit. We then consider an interacting gas under the BCS mean-field approximation for local pairing, and study the pair-breaking mechanism that is induced by the Coriolis effects on superfluidity, where we calculate the critical rotation frequencies both for the onset of pair breaking and for the complete destruction of superfluidity in the system. In particular, by comparing the results of a fully-quantum-mechanical Bogoliubov-de Gennes approach with those of a semiclassical local-density approximation, we construct extensive phase diagrams for a wide range of parameter regimes in the trap where the aforementioned competition may, e.g., favor an outer normal edge that is completely phase separated from the central superfluid core by vacuum.

  15. Chemical characterization of bio-oils using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry.

    Science.gov (United States)

    Tessarolo, Nathalia S; dos Santos, Luciana R M; Silva, Raphael S F; Azevedo, Débora A

    2013-03-01

    The liquid product obtained via the biomass flash pyrolysis is commonly called bio-oil or pyrolysis oil. Bio-oils can be used as sources for chemicals or as fuels, primarily in mixtures or emulsions with fossil fuels. A detailed chemical characterization of bio-oil is necessary to determine its potential uses. Such characterization demands a powerful analytical technique such as comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS). Limited chemical information can be obtained from conventional gas chromatography coupled mass spectrometry (GC-MS) because of the large number of compounds and coelutions. Thus, GC×GC-TOFMS was used for the individual identification of bio-oil components from two samples prepared via the flash pyrolysis of empty palm fruit bunch and pine wood chips. To the best of our knowledge, few papers have reported comprehensive two-dimensional gas chromatography (GC×GC) for bio-oil analysis. Many classes of compounds such as phenols, benzenediols, cyclopentenones, furanones, indanones and alkylpyridines were identified. Several coelutions present in the GC-MS were resolved using GC×GC-TOFMS. Many peaks were detected for the samples by GC-MS (~166 and 129), but 631 and 857 were detected by GC×GC-TOFMS, respectively. The GC×GC-TOFMS analyses indicated that the major classes of components (analytes>0.5% relative area) in the two bio-oil samples are ketones, cyclopentenones, furanones, furans, phenols, benzenediols, methoxy- and dimethoxy-phenols and sugars. In addition, esters, aldehydes and pyridines were found for sample obtained from empty palm fruit bunch, while alcohols and cyclopentanediones were found in sample prepared from pine wood chips indicating different composition profiles due to the biomass sources. The elucidation of the composition of empty fruit bunch and pine wood chips bio-oils indicates that these oils are suitable for the production of value-added chemicals. The

  16. Lipidic ionic liquid stationary phases for the separation of aliphatic hydrocarbons by comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    Nan, He; Zhang, Cheng; O'Brien, Richard A; Benchea, Adela; Davis, James H; Anderson, Jared L

    2017-01-20

    Lipidic ionic liquids (ILs) possessing long alkyl chains as well as low melting points have the potential to provide unique selectivity as well as wide operating ranges when used as stationary phases in gas chromatography. In this study, a total of eleven lipidic ILs containing various structural features (i.e., double bonds, linear thioether chains, and cyclopropanyl groups) were examined as stationary phases in comprehensive two dimensional gas chromatography (GC×GC) for the separation of nonpolar analytes in kerosene. N-alkyl-N'-methyl-imidazolium-based ILs containing different alkyl side chains were used as model structures to investigate the effects of alkyl moieties with different structural features on the selectivities and operating temperature ranges of the IL-based stationary phases. Compared to a homologous series of ILs containing saturated side chains, lipidic ILs exhibit improved selectivity toward the aliphatic hydrocarbons in kerosene. The palmitoleyl IL provided the highest selectivity compared to all other lipidic ILs as well as the commercial SUPELCOWAX 10 column. The linoleyl IL containing two double bonds within the alkyl side chain showed the lowest chromatographic selectivity. The lipidic IL possessing a cyclopropanyl group within the alkyl moiety exhibited the highest thermal stability. The Abraham solvation parameter model was used to evaluate the solvation properties of the lipidic ILs. This study provides the first comprehensive examination into the relation between lipidic IL structure and the resulting solvation characteristics. Furthermore, these results establish a basis for applying lipidic ILs as stationary phases for solute specific separations in GC×GC.

  17. Using comprehensive two-dimensional gas chromatography to explore the geochemistry of the Santa Barbara oil seeps

    Energy Technology Data Exchange (ETDEWEB)

    Reddy, Christopher; Nelson, Robert

    2013-03-27

    The development of comprehensive two-dimensional gas chromatography (GC x GC) has expanded the analytical window for studying complex mixtures like oil. Compared to traditional gas chromatography, this technology separates and resolves at least an order of magnitude more compounds, has a much larger signal to noise ratio, and sorts compounds based on their chemical class; hence, providing highly refined inventories of petroleum hydrocarbons in geochemical samples that was previously unattainable. In addition to the increased resolution afforded by GC x GC, the resulting chromatograms have been used to estimate the liquid vapor pressures, aqueous solubilities, octanol-water partition coefficients, and vaporization enthalpies of petroleum hydrocarbons. With these relationships, powerful and incisive analyses of phase-transfer processes affecting petroleum hydrocarbon mixtures in the environment are available. For example, GC x GC retention data has been used to quantitatively deconvolve the effects of phase transfer processes such as water washing and evaporation. In short, the positive attributes of GC x GC-analysis have led to a methodology that has revolutionized the analysis of petroleum hydrocarbons. Overall, this research has opened numerous fields of study on the biogeochemical "genetics" (referred to as petroleomics) of petroleum samples in both subsurface and surface environments. Furthermore, these new findings have already been applied to the behavior of oil at other seeps as well, for petroleum exploration and oil spill studies.

  18. Comprehensive two-dimensional gas chromatography coupled with fast sulphur-chemiluminescence detection: implications of detector electronics.

    Science.gov (United States)

    Blomberg, Jan; Riemersma, Toby; van Zuijlen, Manfred; Chaabani, Hassan

    2004-09-24

    Within the petrochemical industry, there has been a growing interest in methods capable of providing detailed information on the distribution of sulphur-containing compounds in various product streams, going down to the level of separating and quantifying individual sulphur species. Since no single capillary gas chromatographic column is able to perform this separation, a refuge to multi-dimensional separation techniques has to be taken. In this respect, comprehensive two-dimensional gas chromatography (GC x GC) coupled with sulphur chemiluminescence detection (SCD) has shown to be highly promising. It has been suggested, however, that the detector volume of an SCD restricts its potential to keep up with the fast second-dimension separations of contemporary GC x GC. In this paper, we will demonstrate that the lack of speed of the SCD does not originate from its physical dimensions, but is largely determined by the speed of the electronics used. Additionally, some typical examples will be presented to illustrate the potential of GC x GC coupled with fast SCD.

  19. Two-dimensional time-dependent modelling of fume formation in a pulsed gas metal arc welding process

    Science.gov (United States)

    Boselli, M.; Colombo, V.; Ghedini, E.; Gherardi, M.; Sanibondi, P.

    2013-06-01

    Fume formation in a pulsed gas metal arc welding (GMAW) process is investigated by coupling a time-dependent axi-symmetric two-dimensional model, which takes into account both droplet detachment and production of metal vapour, with a model for fume formation and transport based on the method of moments for the solution of the aerosol general dynamic equation. We report simulative results of a pulsed process (peak current = 350 A, background current 30 A, period = 9 ms) for a 1 mm diameter iron wire, with Ar shielding gas. Results showed that metal vapour production occurs mainly at the wire tip, whereas fume formation is concentrated in the fringes of the arc in the spatial region close to the workpiece, where metal vapours are transported by convection. The proposed modelling approach allows time-dependent tracking of fumes also in plasma processes where temperature-time variations occur faster than nanoparticle transport from the nucleation region to the surrounding atmosphere, as is the case for most pulsed GMAW processes.

  20. Analysis of special surfactants by comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry.

    Science.gov (United States)

    Wulf, Volker; Wienand, Nils; Wirtz, Michaela; Kling, Hans-Willi; Gäb, Siegmar; Schmitz, Oliver J

    2010-01-29

    Multidimensional gas-chromatographic analyses of olesochemically based nonionic, anionic and several cationic surfactants in industrial cleaners are demonstrated. Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry allows the simultaneous determination of fatty alcohols, fatty alcohol sulphates and alkyl polyglucosides. In addition, the determination of fatty alcohol ethoxylates up to C(10)EO(8) (highest degree of ethoxylation) and C(18)EO(5) (longest C-chain at an ethoxylation degree of five) and the analysis of fatty alcohol alkoxylates that contain ethoxy (EO) and propoxy (PO) groups could be realized. Because of decomposition in the injector and a weak EI-fragmentation, cationic surfactants such as alkyl benzyl dimethyl ammonium chloride could also be identified by their characteristic fragments. Thermogravimetric analyses confirmed that the temperature in a normal GC injector is not high enough to cause thermal decomposition of esterquats. However, we could demonstrate that a modified silylation procedure forms decomposition products of esterquats in the GC injector which are detectable by GCxGC-(TOF)MS and allows the identification of such GC-atypical analytes.

  1. Discrete particle simulation of bubble and slug formation in a two-dimensional gas-fluidised bed: A hard-sphere approach.

    NARCIS (Netherlands)

    Hoomans, B.P.B.; Kuipers, J.A.M.; Briels, Willem J.; van Swaaij, Willibrordus Petrus Maria

    1996-01-01

    A discrete particle model of a gas-fluidised bed has been developed and in this the two-dimensional motion of the individual, spherical particles was directly calculated from the forces acting on them, accounting for the interaction between the particles and the interstitial gas phase. Our collision

  2. A peaklet-based generic strategy for the untargeted analysis of comprehensive two-dimensional gas chromatography mass spectrometry data sets.

    Science.gov (United States)

    Egert, Björn; Weinert, Christoph H; Kulling, Sabine E

    2015-07-31

    Comprehensive two-dimensional gas chromatography mass spectrometry (GC×GC-MS) is a well-established key technology in analytical chemistry and increasingly used in the field of untargeted metabolomics. However, automated processing of large GC×GC-MS data sets is still a major bottleneck in untargeted, large-scale metabolomics. For this reason we introduce a novel peaklet-based alignment strategy. The algorithm is capable of an untargeted deterministic alignment exploiting a density based clustering procedure within a time constrained similarity matrix. Exploiting minimal (1)D and (2)D retention time shifts between peak modulations, the alignment is done without the need for peak merging which also eliminates the need for linear or nonlinear retention time correction procedures. The approach is validated in detail using data of urine samples from a large human metabolomics study. The data was acquired by a Shimadzu GCMS-QP2010 Ultra GC×GC-qMS system and consists of 512 runs, including 312 study samples and 178 quality control sample injections, measured within a time period of 22 days. The final result table consisted of 313 analytes, each of these being detectable in at least 75% of the study samples. In summary, we present an automated, reliable and fully transparent workflow for the analysis of large GC×GC-qMS metabolomics data sets.

  3. Validated Method for the Quantification of Buprenorphine in Postmortem Blood Using Solid-Phase Extraction and Two-Dimensional Gas Chromatography-Mass Spectrometry.

    Science.gov (United States)

    Nahar, Limon Khatun; Andrews, Rebecca; Paterson, Sue

    2015-09-01

    A highly sensitive and fully validated method was developed for the quantification of buprenorphine in postmortem blood. After a two-step protein precipitation process using acetonitrile, buprenorphine was purified using mixed-mode (C8/cation exchange) solid-phase extraction cartridges. Endogenous water-soluble compounds and lipids were removed from the cartridges before the samples were eluted, concentrated and derivatized using N-methyl-N-trimethylsilyltrifluoroacetamide. The samples were analyzed using two-dimensional gas chromatography-mass spectrometry (2D GC-MS) in selective ion-monitoring mode. A low polarity Rxi(®)-5MS (30 m × 0.25 mm I.D. × 0.25 µm) was used as the primary column and the secondary column was a mid-polarity Rxi(®) -17Sil MS (15 m × 0.32 mm I.D. × 0.25 µm). The assay was linear from 1.0 to 50.0 ng/mL (r(2) > 0.99; n = 6). Intraday (n = 6) and interday (n = 9) imprecisions (percentage relative standard deviation, % RSD) were selective with no interference from endogenous compounds or from 62 commonly encountered drugs. To prove method applicability to forensic postmortem cases, 14 authentic postmortem blood samples were analyzed.

  4. The quantification of short-chain chlorinated paraffins in sediment samples using comprehensive two-dimensional gas chromatography with μECD detection.

    Science.gov (United States)

    Muscalu, Alina M; Morse, Dave; Reiner, Eric J; Górecki, Tadeusz

    2017-03-01

    The analysis of persistent organic pollutants in environmental samples is a challenge due to the very large number of compounds with varying chemical and physical properties. Chlorinated paraffins (CPs) are complex mixtures of chlorinated n-alkanes with varying chain lengths (C10 to C30) and degree of chlorination (30 to 70% by weight). Their physical-chemical properties make these compounds persistent in the environment and able to bioaccumulate in living organisms. Comprehensive two-dimensional gas chromatography (GC × GC) coupled with micro-electron capture detection (μECD) was used to separate and quantify short-chain chlorinated paraffins (SCCP) in sediment samples. Distinct ordered bands were observed in the GC × GC chromatograms pointing to group separation. Using the Classification function of the ChromaTOF software, summary tables were generated to determine total area counts to set up multilevel-calibration curves for different technical mixes. Fortified sediment samples were analyzed by GC × GC-μECD with minimal extraction and cleanup. Recoveries ranged from 120 to 130%. To further validate the proposed method for the analysis of SCCPs, the laboratory participated in interlaboratory studies for the analysis of standards and sediment samples. The results showed recoveries between 75 and 95% and z-score values <2, demonstrating that the method is suitable for the analysis of SCCPs in soil/sediment samples. Graphical abstract Quantification of SCCPs by 2D-GC-μECD.

  5. Tailoring the Two Dimensional Electron Gas at Polar ABO3/SrTiO3 Interfaces for Oxide Electronics

    Science.gov (United States)

    Li, Changjian; Liu, Zhiqi; Lü, Weiming; Wang, Xiao Renshaw; Annadi, Anil; Huang, Zhen; Zeng, Shengwei; Ariando; Venkatesan, T.

    2015-08-01

    The 2D electron gas at the polar/non-polar oxide interface has become an important platform for several novel oxide electronic devices. In this paper, the transport properties of a wide range of polar perovskite oxide ABO3/SrTiO3 (STO) interfaces, where ABO3 includes LaAlO3, PrAlO3, NdAlO3, NdGaO3 and LaGaO3 in both crystalline and amorphous forms, were investigated. A robust 4 unit cell (uc) critical thickness for metal insulator transition was observed for crystalline polar layer/STO interface while the critical thickness for amorphous ones was strongly dependent on the B site atom and its oxygen affinity. For the crystalline interfaces, a sharp transition to the metallic state (i.e. polarization catastrophe induced 2D electron gas only) occurs at a growth temperature of 515 °C which corresponds to a critical relative crystallinity of ~70 ± 10% of the LaAlO3 overlayer. This temperature is generally lower than the metal silicide formation temperature and thus offers a route to integrate oxide heterojunction based devices on silicon.

  6. Determination of disease biomarkers in Eucalyptus by comprehensive two-dimensional gas chromatography and multivariate data analysis.

    Science.gov (United States)

    Hantao, Leandro Wang; Aleme, Helga Gabriela; Passador, Martha Maria; Furtado, Edson Luiz; Ribeiro, Fabiana Alves de Lima; Poppi, Ronei Jesus; Augusto, Fabio

    2013-03-01

    In this paper is reported the use of the chromatographic profiles of volatiles to determine disease markers in plants - in this case, leaves of Eucalyptus globulus contaminated by the necrotroph fungus Teratosphaeria nubilosa. The volatile fraction was isolated by headspace solid phase microextraction (HS-SPME) and analyzed by comprehensive two-dimensional gas chromatography-fast quadrupole mass spectrometry (GC×GC-qMS). For the correlation between the metabolic profile described by the chromatograms and the presence of the infection, unfolded-partial least squares discriminant analysis (U-PLS-DA) with orthogonal signal correction (OSC) were employed. The proposed method was checked to be independent of factors such as the age of the harvested plants. The manipulation of the mathematical model obtained also resulted in graphic representations similar to real chromatograms, which allowed the tentative identification of more than 40 compounds potentially useful as disease biomarkers for this plant/pathogen pair. The proposed methodology can be considered as highly reliable, since the diagnosis is based on the whole chromatographic profile rather than in the detection of a single analyte.

  7. Mineral oil in human tissues, part II: characterization of the accumulated hydrocarbons by comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    Biedermann, Maurus; Barp, Laura; Kornauth, Christoph; Würger, Tanja; Rudas, Margaretha; Reiner, Angelika; Concin, Nicole; Grob, Koni

    2015-02-15

    Mineral oil hydrocarbons are by far the largest contaminant in the human body. Their composition differs from that in the mineral oils humans are exposed to, and varies also between different tissues of the same individual. Using the presently best technique for characterizing the composition of mineral oil hydrocarbons, comprehensive two-dimensional gas chromatography (GC×GC), the hydrocarbons in human tissues were compared to those of various mineral oils. This provided information about the strongly accumulated species and might give hints on the flow path through the human body. The selectivity of accumulation is probably also of interest for the risk assessment of synthetic hydrocarbons (polyolefins). GC×GC grouped the MOSH into classes of n-alkanes, paraffins with a low degree of branching, multibranched paraffins and naphthenes (alkylated cyclic hydrocarbons) with 1-4 rings. Metabolic elimination was observed for constituents of all these classes, but was selective within each class. The MOSH in the subcutaneous abdominal fat tissues and the mesenteric lymph nodes (MLN) had almost the same composition and included the distinct signals observed in mineral oil, though in reduced amounts relative to the cloud of unresolved hydrocarbons. The MOSH in the liver and the spleen were different from those in the MLN and fat tissue, but again with largely identical composition for a given individual. Virtually all constituents forming distinct signals were eliminated, leaving an unresolved residue of highly isomerized hydrocarbons.

  8. The low-temperature mobility of two-dimensional electron gas in AlGaN/GaN heterostructures

    Institute of Scientific and Technical Information of China (English)

    Zhang Jin-Feng; Mao Wei; Zhang Jin-Cheng; Hao Yue

    2008-01-01

    To reveal the internal physics of the low-temperature mobility of two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures, we present a theoretical study of the strong dependence of 2DEG mobility on Al content and thickness of AlGaN barrier layer. The theoretical results are compared with one of the highest measured of 2DEG mobility reported for AlGaN/GaN heterostructures. The 2DEG mobility is modelled as a combined effect of the scattering mechanisms including acoustic deformation-potential, piezoelectric, ionized background donor, surface donor, dislocation, alloy disorder and interface roughness scattering. The analyses of the individual scattering processes show that the dominant scattering mechanisms are the alloy disorder scattering and the interface roughness scattering at low temperatures. The variation of 2DEG mobility with the barrier layer parameters results mainly from the change of 2DEG density and distribution. It is suggested that in AlGaN/GaN samples with a high Al content or a thick AlGaN layer, the interface roughness scattering may restrict the 2DEG mobility significantly, for the AlGan/GaN interface roughness increases due to the stress accumulation in AlGaN layer.

  9. The mobility of two-dimensional electron gas in AlGaN/GaN heterostructures with varied Al content

    Institute of Scientific and Technical Information of China (English)

    ZHANG JinFeng; HAO Yue; ZHANG JinCheng; NI JinYu

    2008-01-01

    The mobility of the two-dimensional electron gas (2DEG) in AlGaN/GaN hetero-structures changes significantly with AI content in the AlGaN barrier layer, while few mechanism analyses focus on it. Theoretical calculation and analysis of the 2DEG mobility in AlGaN/GaN heterostructures with varied Al content are carried out based on the recently reported experimental data. The 2DEG mobility is modeled analytically as the total effects of the scattering mechanisms including acoustic deformation-potential, piezoelectric, polar optic phonon, alloy disorder, interface roughness, dislocation and remote modulation doping scattering. We show that the increase of the 2DEG density, caused by the ascension of the Al content in the barrier layer, is a dominant factor that leads to the changes of the individual scat-tering processes. The change of the 2DEG mobility with Al content are mainly de-termined by the interface roughness scattering and the alloy disorder scattering at 77 K, and the polar optic phonon scattering and the interface roughness scattering at the room temperature. The calculated function of the interface roughness pa-rameters on the Al content shows that the stress caused AlGaN/GaN interface degradation at higher Al content is an important factor in the limitation of the in-terface roughness scattering on the 2DEG mobility in AlGaN/GaN heterostructures with high Al content.

  10. Characterization of the Clostridium difficile volatile metabolome using comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry.

    Science.gov (United States)

    Rees, Christiaan A; Shen, Aimee; Hill, Jane E

    2016-12-15

    Clostridium difficile is a bacterial pathogen capable of causing life-threatening infections of the gastrointestinal tract characterized by severe diarrhea. Exposure to certain classes of antibiotics, advanced age, and prolonged hospitalizations are known risk factors for infection by this organism. Anecdotally, healthcare providers have reported that they can smell C. difficile infections in their patients, and several studies have suggested that there may indeed be an olfactory signal associated with C. difficile-associated diarrhea. In this study, we sought to characterize the volatile molecules produced by an epidemic strain of C. difficile (R20291) using headspace solid-phase microextraction (HS-SPME) followed by two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS). We report on a set of 77 volatile compounds, of which 59 have not previously been associated with C. difficile growth in vitro. Amongst these reported compounds, we detect both straight-chain and branched-chain carboxylic acids, as well as p-cresol, which have been the primary foci of C. difficile volatile metabolomic studies to-date. We additionally report on novel sulfur-containing and carbonyl-containing molecules that have not previously been reported for C. difficile. With the identification of these novel C. difficile-associated volatile compounds, we demonstrate the superior resolution and sensitivity of GC×GC-TOFMS relative to traditional GC-MS. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Two-Dimensional Electron Gas at SrTiO3-Based Oxide Heterostructures via Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Sang Woon Lee

    2016-01-01

    Full Text Available Two-dimensional electron gas (2DEG at an oxide interface has been attracting considerable attention for physics research and nanoelectronic applications. Early studies reported the formation of 2DEG at semiconductor interfaces (e.g., AlGaAs/GaAs heterostructures with interesting electrical properties such as high electron mobility. Besides 2DEG formation at semiconductor junctions, 2DEG was realized at the interface of an oxide heterostructure such as the LaAlO3/SrTiO3 (LAO/STO heterojunction. The origin of 2DEG was attributed to the well-known “polar catastrophe” mechanism in oxide heterostructures, which consist of an epitaxial LAO layer on a single crystalline STO substrate among proposed mechanisms. Recently, it was reported that the creation of 2DEG was achieved using the atomic layer deposition (ALD technique, which opens new functionality of ALD in emerging nanoelectronics. This review is focused on the origin of 2DEG at oxide heterostructures using the ALD process. In particular, it addresses the origin of 2DEG at oxide interfaces based on an alternative mechanism (i.e., oxygen vacancies.

  12. A comparison of the transport properties of bilayer graphene,monolayer graphene, and two-dimensional electron gas

    Institute of Scientific and Technical Information of China (English)

    Sun Li-Feng; Dong Li-Min; Wu Zhi-Fang; Fang Chao

    2013-01-01

    we studied and compared the transport properties of charge carriers in bilayer graphene,monolayer graphene,and the conventional semiconductors (the two-dimensional electron gas (2DEG)).It is elucidated that the normal incidence transmission in the bilayer graphene is identical to that in the 2DEG but totally different from that in the monolayer graphene.However,resonant peaks appear in the non-normal incidence transmission profile for a high barrier in the bilayer graphene,which do not occur in the 2DEG.Furthermore,there are tunneling and forbidden regions in the transmission spectrum for each material,and the division of the two regions has been given in the work.The tunneling region covers a wide range of the incident energy for the two graphene systems,but only exists under specific conditions for the 2DEG.The counterparts of the transmission in the conductance profile are also given for the three materials,which may be used as high-performance devices based on the bilayer graphene.

  13. Characterization of incense smoke by solid phase microextraction—Comprehensive two-dimensional gas chromatography (GC×GC)

    Science.gov (United States)

    Tran, Tin C.; Marriott, Philip J.

    Comprehensive two-dimensional gas chromatography in tandem with flame ionization detection (GC×GC-FID) was used for the qualitative fingerprint characterisation of four different types of powdered incense headspace (H/S), and incense smoke. Volatile organic compounds (VOCs) in the incense powder and smoke were extracted by using solid phase microextraction (SPME) with a polydimethylsiloxane/divinylbenzene (PDMS/DVB) 65 μm fiber. Low-polarity/polar, and polar/non-polar phase combinations were tested to contrast the GC×GC separation of components in these two column sets. A total of 324 compounds were tentatively identified, with more than 100 compounds in incense powders and more than 200 compounds in the incense smoke, by using GC coupled to quadrupole mass spectrometric detection. Identification required at least 90% match with the NIST library; otherwise they were considered as unidentified. The smoke stream comprised compounds originating from the incense powder, and combustion products such as PAH, N-heterocyclics, and furans. However, GC×GC was able to separate many more volatile compounds (possibly hundreds more) present in the complex smoke samples, many of which cannot be separated by conventional 1D-GC; this is a direct consequence of the high-resolution power of GC×GC. GC×GC fingerprint comparison of powder H/S with smoke allows facile subtraction of the former from the latter to assist identification of compounds generated from burning incense.

  14. Andreev reflection and bound state formation in a ballistic two-dimensional electron gas probed by a quantum point contact

    Science.gov (United States)

    Irie, Hiroshi; Todt, Clemens; Kumada, Norio; Harada, Yuichi; Sugiyama, Hiroki; Akazaki, Tatsushi; Muraki, Koji

    2016-10-01

    We study coherent transport and bound state formation of Bogoliubov quasiparticles in a high-mobility I n0.75G a0.25As two-dimensional electron gas (2DEG) coupled to a superconducting Nb electrode by means of a quantum point contact (QPC) as a tunable single-mode probe. Below the superconducting critical temperature of Nb, the QPC shows a single-channel conductance greater than the conductance quantum 2 e2/h at zero bias, which indicates the presence of Andreev-reflected quasiparticles, time-reversed states of the injected electron, returning back through the QPC. The marked sensitivity of the conductance enhancement to voltage bias and perpendicular magnetic field suggests a mechanism analogous to reflectionless tunneling—a hallmark of phase-coherent transport, with the boundary of the 2DEG cavity playing the role of scatterers. When the QPC transmission is reduced to the tunneling regime, the differential conductance vs bias voltage probes the single-particle density of states in the proximity area. Measured conductance spectra show a double peak within the superconducting gap of Nb, demonstrating the formation of Andreev bound states in the 2DEG. Both of these results, obtained in the open and closed geometries, underpin the coherent nature of quasiparticles, i.e., phase-coherent Andreev reflection at the InGaAs/Nb interface and coherent propagation in the ballistic 2DEG.

  15. High-Throughput Design of Two-Dimensional Electron Gas Systems Based on Polar/Nonpolar Perovskite Oxide Heterostructures

    Science.gov (United States)

    Yang, Kesong; Nazir, Safdar; Behtash, Maziar; Cheng, Jianli

    2016-10-01

    The two-dimensional electron gas (2DEG) formed at the interface between two insulating oxides such as LaAlO3 and SrTiO3 (STO) is of fundamental and practical interest because of its novel interfacial conductivity and its promising applications in next-generation nanoelectronic devices. Here we show that a group of combinatorial descriptors that characterize the polar character, lattice mismatch, band gap, and the band alignment between the perovskite-oxide-based band insulators and the STO substrate, can be introduced to realize a high-throughput (HT) design of SrTiO3-based 2DEG systems from perovskite oxide quantum database. Equipped with these combinatorial descriptors, we have carried out a HT screening of all the polar perovskite compounds, uncovering 42 compounds of potential interests. Of these, Al-, Ga-, Sc-, and Ta-based compounds can form a 2DEG with STO, while In-based compounds exhibit a strain-induced strong polarization when deposited on STO substrate. In particular, the Ta-based compounds can form 2DEG with potentially high electron mobility at (TaO2)+/(SrO)0 interface. Our approach, by defining materials descriptors solely based on the bulk materials properties, and by relying on the perovskite-oriented quantum materials repository, opens new avenues for the discovery of perovskite-oxide-based functional interface materials in a HT fashion.

  16. Durability-enhanced two-dimensional hole gas of C-H diamond surface for complementary power inverter applications

    Science.gov (United States)

    Kawarada, Hiroshi; Yamada, Tetsuya; Xu, Dechen; Tsuboi, Hidetoshi; Kitabayashi, Yuya; Matsumura, Daisuke; Shibata, Masanobu; Kudo, Takuya; Inaba, Masafumi; Hiraiwa, Atsushi

    2017-02-01

    Complementary power field effect transistors (FETs) based on wide bandgap materials not only provide high-voltage switching capability with the reduction of on-resistance and switching losses, but also enable a smart inverter system by the dramatic simplification of external circuits. However, p-channel power FETs with equivalent performance to those of n-channel FETs are not obtained in any wide bandgap material other than diamond. Here we show that a breakdown voltage of more than 1600 V has been obtained in a diamond metal-oxide-semiconductor (MOS) FET with a p-channel based on a two-dimensional hole gas (2DHG). Atomic layer deposited (ALD) Al2O3 induces the 2DHG ubiquitously on a hydrogen-terminated (C-H) diamond surface and also acts as both gate insulator and passivation layer. The high voltage performance is equivalent to that of state-of-the-art SiC planar n-channel FETs and AlGaN/GaN FETs. The drain current density in the on-state is also comparable to that of these two FETs with similar device size and VB.

  17. Attempt to unravel the composition of toxaphene by comprehensive two-dimensional gas chromatography with selective detection.

    Science.gov (United States)

    Korytár, P; van Stee, L L P; Leonards, P E G; de Boer, J; Brinkman, U A Th

    2003-04-25

    Comprehensive two-dimensional gas chromatography (GC x GC) coupled with micro electron-capture and time-of-flight mass spectrometric (TOF-MS) detection has been used to analyse technical toxaphene. An HP-1 x HT-8 column combination yielded highly structured chromatograms and revealed a complex mixture of over 1000 compounds what is significantly higher number than in any study before. The analysis of a mixture of 23 individual congeners and TOF-MS evaluation of technical toxaphene showed that the chromatogram is structured according to the number of chlorine substituents in a molecule. The nature of the compounds (bornane and camphene) does not appear to have any influence. The sum of the peak areas of all congeners in each group was calculated using laboratory-written software; based on these results, the composition of technical toxaphene as a function of the number of chlorine substituents was provisionally calculated and was found that hepta- and octachlorinated compounds represents 75% of the total toxaphene area.

  18. Fluctuations in an ordered c (2×2) two-dimensional lattice-gas system with repulsive interactions

    Science.gov (United States)

    Argyrakis, P.; Chumak, A. A.; Maragakis, M.

    2005-06-01

    Fluctuations of the particle density in an ordered c(2×2) two-dimensional lattice-gas system are studied both analytically and by means of Monte Carlo simulations. The ordering is caused by a strong interparticle repulsive interaction resulting in the second order phase transition. The lattice of adsorption sites is divided into two sublattices (almost filled and almost empty sublattices) each of which contains a small number of structural “defects,” i.e., vacancies and excess particles. The relaxation of the correlation function of fluctuations turns out to be governed by two different functions. This peculiarity is to be contrasted with the traditional fluctuation theory which predicts the existence of a single damping constant, determined by the collective diffusion coefficient. A specific thesis of the proposed approach is that transport phenomena in ordered systems may be described in terms of both displacements and generation-recombination of structural defects. Accordingly, the correlation function of fluctuations depends on diffusion coefficients of two defect species as well as on the generation-recombination frequency. Our theory reduces to the usual one when fluctuations occur under local equilibrium conditions, i.e., for a sufficiently large size of probe areas and not too great values of interaction parameter. The analytical results agree well with those obtained in the Monte Carlo framework.

  19. Broadband terahertz radiation from a biased two-dimensional electron gas in an AlGaN/GaN heterostructure

    Science.gov (United States)

    Zhongxin, Zheng; Jiandong, Sun; Yu, Zhou; Zhipeng, Zhang; Hua, Qin

    2015-10-01

    The broadband terahertz (THz) emission from drifting two-dimensional electron gas (2DEG) in an AlGaN/GaN heterostructure at 6 K is reported. The devices are designed as THz plasmon emitters according to the Smith-Purcell effect and the ‘shallow water’ plasma instability mechanism in 2DEG. Plasmon excitation is excluded since no signature of electron-density dependent plasmon mode is observed. Instead, the observed THz emission is found to come from the heated lattice and/or the hot electrons. Simulated emission spectra of hot electrons taking into account the THz absorption in air and Fabry-Pérot interference agree well with the experiment. It is confirmed that a blackbody-like THz emission will inevitably be encountered in similar devices driven by a strong in-plane electric field. A conclusion is drawn that a more elaborate device design is required to achieve efficient plasmon excitation and THz emission. Project supported by the National Basic Research Program of China (No. G2009CB929303), the National Natural Science Foundation of China (No. 61271157), the China Postdoctoral Science Foundation (No. 2014M551678), and the Jiangsu Planned Projects for Postdoctoral Research Funds (No. 1301054B).

  20. Screened test-charge - test-charge interaction in the two-dimensional electron gas: bound states

    Science.gov (United States)

    Gold, A.; Ghazali, A.

    1997-08-01

    We study the test-charge - test-charge interaction when screening effects of a two-dimensional electron gas are taken into account. The Schrödinger equation is solved in the momentum space by diagonalizing the corresponding matrix and the results are compared with variational calculations. For two positive (or negative) test-charges bound states are obtained for low electron densities when many-body effects are incorporated in the screening function. For a density larger than a critical density, 0953-8984/9/32/011/img5 (0953-8984/9/32/011/img6 is the Wigner - Seitz parameter), no bound states are found. Below the critical density, 0953-8984/9/32/011/img7, the number of bound states and their energy increase with decreasing density and the ground-state binding energy saturates near 0953-8984/9/32/011/img8. Finite-width effects for quantum wells are also discussed. We present new results for bound states between a positive and a negative test charge and we discuss effects of exchange and correlation on the binding energies.

  1. Quantification of real thermal, catalytic, and hydrodeoxygenated bio-oils via comprehensive two-dimensional gas chromatography with mass spectrometry.

    Science.gov (United States)

    Silva, Raquel V S; Tessarolo, Nathalia S; Pereira, Vinícius B; Ximenes, Vitor L; Mendes, Fábio L; de Almeida, Marlon B B; Azevedo, Débora A

    2017-03-01

    The elucidation of bio-oil composition is important to evaluate the processes of biomass conversion and its upgrading, and to suggest the proper use for each sample. Comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOFMS) is a widely applied analytical approach for bio-oil investigation due to the higher separation and resolution capacity from this technique. This work addresses the issue of analytical performance to assess the comprehensive characterization of real bio-oil samples via GC×GC-TOFMS. The approach was applied to the individual quantification of compounds of real thermal (PWT), catalytic process (CPO), and hydrodeoxygenation process (HDO) bio-oils. Quantification was performed with reliability using the analytical curves of oxygenated and hydrocarbon standards as well as the deuterated internal standards. The limit of quantification was set at 1ngµL(-1) for major standards, except for hexanoic acid, which was set at 5ngµL(-1). The GC×GC-TOFMS method provided good precision (bio-oil samples. Sugars, furans, and alcohols appear as the major constituents of the PWT, CPO, and HDO samples, respectively. In order to obtain bio-oils with better quality, the catalytic pyrolysis process may be a better option than hydrogenation due to the effective reduction of oxygenated compound concentrations and the lower cost of the process, when hydrogen is not required to promote deoxygenation in the catalytic pyrolysis process.

  2. Durability-enhanced two-dimensional hole gas of C-H diamond surface for complementary power inverter applications

    Science.gov (United States)

    Kawarada, Hiroshi; Yamada, Tetsuya; Xu, Dechen; Tsuboi, Hidetoshi; Kitabayashi, Yuya; Matsumura, Daisuke; Shibata, Masanobu; Kudo, Takuya; Inaba, Masafumi; Hiraiwa, Atsushi

    2017-01-01

    Complementary power field effect transistors (FETs) based on wide bandgap materials not only provide high-voltage switching capability with the reduction of on-resistance and switching losses, but also enable a smart inverter system by the dramatic simplification of external circuits. However, p-channel power FETs with equivalent performance to those of n-channel FETs are not obtained in any wide bandgap material other than diamond. Here we show that a breakdown voltage of more than 1600 V has been obtained in a diamond metal-oxide-semiconductor (MOS) FET with a p-channel based on a two-dimensional hole gas (2DHG). Atomic layer deposited (ALD) Al2O3 induces the 2DHG ubiquitously on a hydrogen-terminated (C-H) diamond surface and also acts as both gate insulator and passivation layer. The high voltage performance is equivalent to that of state-of-the-art SiC planar n-channel FETs and AlGaN/GaN FETs. The drain current density in the on-state is also comparable to that of these two FETs with similar device size and VB. PMID:28218234

  3. Detection of an extended human volatome with comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry.

    Directory of Open Access Journals (Sweden)

    Michael Phillips

    Full Text Available BACKGROUND: Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC-TOF MS has been proposed as a powerful new tool for multidimensional analysis of complex chemical mixtures. We investigated GCxGC-TOF MS as a new method for identifying volatile organic compounds (VOCs in normal human breath. METHODS: Samples of alveolar breath VOCs and ambient room air VOC were collected with a breath collection apparatus (BCA onto separate sorbent traps from 34 normal healthy volunteers (mean age = 40 yr, SD = 17 yr, male/female = 19/15. VOCs were separated on two serial capillary columns separated by a cryogenic modulator, and detected with TOF MS. The first and second dimension columns were non-polar and polar respectively. RESULTS: BCA collection combined with GC×GC-TOF MS analysis identified approximately 2000 different VOCs in samples of human breath, many of which have not been previously reported. The 50 VOCs with the highest alveolar gradients (abundance in breath minus abundance in ambient room air mostly comprised benzene derivatives, acetone, methylated derivatives of alkanes, and isoprene. CONCLUSIONS: Collection and analysis of breath VOCs with the BCA-GC×GC-TOF MS system extended the size of the detectable human volatile metabolome, the volatome, by an order of magnitude compared to previous reports employing one-dimensional GC-MS. The size of the human volatome has been under-estimated in the past due to coelution of VOCs in one-dimensional GC analytical systems.

  4. Negative differential conductivity induced current instability in two-dimensional electron gas system in high magnetic fields

    Science.gov (United States)

    Lee, Ching-Ping; Komiyama, Susumu; Chen, Jeng-Chung

    2015-03-01

    High mobility two-dimensional electron gas (2DEG) formed in the interface of a GaAs/AlGaAs hetero-structure in high magnetic field (B) exhibits interring nonlinear response either under microwave radiation or to a dc electric field (E). It is general believed that this kind nonlinear behavior is closely related to the occurrence of negative-differential conductance (NDC) in the presence of strong B and E. We observe a new type NDC state driven by a direct current above a threshold value (Ith) applied to a 2DEG as a function of B at relatively high temperatures (T). A current instability is observed in 2DEG system at high B ~6-8 T and at high T ~ 20- 30 K while the applied current is over Ith. The longitudinal voltage Vxx shows sub-linear behavior with the increase of I. As the current exceed Ith, Vxx suddenly drops a ΔVxx and becomes irregular associated with the appearance of hysteresis with sweeping I. We find that Ith increases with the increase of B and of T; meanwhile, ΔVxx is larger at higher B but lower T. Data analysis suggest that the onset of voltage fluctuation can be described by a NDC model proposed by Kurosawa et al. in 1976. The general behaviors of T and B dependence of current instability are analog to those recently reported at lower both T and B. This consistence suggests the same genuine mechanism of NDC phenomena observed in 2DEG system.

  5. Quantitative analysis of essential oils in perfume using multivariate curve resolution combined with comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    de Godoy, Luiz Antonio Fonseca; Hantao, Leandro Wang; Pedroso, Marcio Pozzobon; Poppi, Ronei Jesus; Augusto, Fabio

    2011-08-05

    The use of multivariate curve resolution (MCR) to build multivariate quantitative models using data obtained from comprehensive two-dimensional gas chromatography with flame ionization detection (GC×GC-FID) is presented and evaluated. The MCR algorithm presents some important features, such as second order advantage and the recovery of the instrumental response for each pure component after optimization by an alternating least squares (ALS) procedure. A model to quantify the essential oil of rosemary was built using a calibration set containing only known concentrations of the essential oil and cereal alcohol as solvent. A calibration curve correlating the concentration of the essential oil of rosemary and the instrumental response obtained from the MCR-ALS algorithm was obtained, and this calibration model was applied to predict the concentration of the oil in complex samples (mixtures of the essential oil, pineapple essence and commercial perfume). The values of the root mean square error of prediction (RMSEP) and of the root mean square error of the percentage deviation (RMSPD) obtained were 0.4% (v/v) and 7.2%, respectively. Additionally, a second model was built and used to evaluate the accuracy of the method. A model to quantify the essential oil of lemon grass was built and its concentration was predicted in the validation set and real perfume samples. The RMSEP and RMSPD obtained were 0.5% (v/v) and 6.9%, respectively, and the concentration of the essential oil of lemon grass in perfume agreed to the value informed by the manufacturer. The result indicates that the MCR algorithm is adequate to resolve the target chromatogram from the complex sample and to build multivariate models of GC×GC-FID data. Copyright © 2011 Elsevier B.V. All rights reserved.

  6. High-Throughput Computational Design of Advanced Functional Materials: Topological Insulators and Two-Dimensional Electron Gas Systems

    Science.gov (United States)

    Yang, Kesong

    As a rapidly growing area of materials science, high-throughput (HT) computational materials design is playing a crucial role in accelerating the discovery and development of novel functional materials. In this presentation, I will first introduce the strategy of HT computational materials design, and take the HT discovery of topological insulators (TIs) as a practical example to show the usage of such an approach. Topological insulators are one of the most studied classes of novel materials because of their great potential for applications ranging from spintronics to quantum computers. Here I will show that, by defining a reliable and accessible descriptor, which represents the topological robustness or feasibility of the candidate, and by searching the quantum materials repository aflowlib.org, we have automatically discovered 28 TIs (some of them already known) in five different symmetry families. Next, I will talk about our recent research work on the HT computational design of the perovskite-based two-dimensional electron gas (2DEG) systems. The 2DEG formed on the perovskite oxide heterostructure (HS) has potential applications in next-generation nanoelectronic devices. In order to achieve practical implementation of the 2DEG in the device design, desired physical properties such as high charge carrier density and mobility are necessary. Here I show that, using the same strategy with the HT discovery of TIs, by introducing a series of combinatorial descriptors, we have successfully identified a series of candidate 2DEG systems based on the perovskite oxides. This work provides another exemplar of applying HT computational design approach for the discovery of advanced functional materials.

  7. Enantiomeric separation and quantification of ephedrine-type alkaloids in herbal materials by comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    Wang, Min; Marriott, Philip J; Chan, Wing-Hong; Lee, Albert W M; Huie, Carmen W

    2006-04-21

    The separation of ephedrine-type alkaloids and their enantiomers in raw herbs and commercial herbal products was investigated by carrying out enantioselective separation in the first-dimension column (containing beta-cyclodextrin as the chiral selector) of a comprehensive two-dimensional gas chromatography (GC x GC) system, whereas a polar polyethylene glycol capillary column was used for separation in the second dimension. Naturally occurring ephedrine-type alkaloids and their synthetic analogues (enantiomeric counterparts) were adequately resolved from each other, as well as from potential interference species in the sample matrix using GC x GC, whereas single column GC analysis was unable to separate all the alkaloids of interest. Detection limits in the order of 0.1-1.3 microg/mL and linearity of calibration with R(2)>or=0.999 over approximately the range of 0.5-100 microg/mL for the quantitative determination of various ephedrine-type alkaloids were obtained. The commercial herbal products tested contained mostly (-)-ephedrine, (+)-pseudoephedrine, (-)-N-methylephedrine and (-)-norephedrine, with concentrations in the range of 40-2100, 0-1,300, 15-300 and 0-30 microg/g of the product, respectively, and repeatability of analysis was generally in the range of 1-5%. The present GCxGC method is effective and useful for the determination of the dosage levels of the principle ephedrine-type alkaloids in commercial health supplements and complex raw herb formulations, as well the differentiation of ephedrine-containing products that were derived from natural plant or synthetic sources, e.g., simply by visualizing the presence or absence of the enantiomeric pairs of (+/-) ephedrine and (+/-)-N-methylephedrine in the GC x GC chromatograms.

  8. Hydrocarbon Specificity During Aerobic oil Biodegradation Revealed in Marine Microcosms With the use of Comprehensive, Two-Dimensional Gas Chromatography.

    Science.gov (United States)

    Wardlaw, G. D.; Reddy, C. M.; Nelson, R. K.; Valentine, D. L.

    2008-12-01

    In 2003 the National Research Council reported more than 380 million gallons of oil is emitted into the ocean each year from natural seepage and as a result of anthropogenic activities. Many of the hydrocarbons making up this oil are persistent and toxic to marine life. Petroleum emitted into biologically sensitive areas can lead to environmental stress and ecosystem collapse. As a result many studies and a substantial amount of resources have been devoted to creating efficient and effective remediation tools and developing a better understanding of natural hydrocarbon weathering processes occurring in marine environments. The goal of this study is to elucidate patterns and extent of aerobic hydrocarbon degradation in marine sediments. In order to assess the specific molecular transformations occurring in petroleum emitted into oxic marine environments, we prepared microcosm experiments using sediments and seawater collected from the natural oil seeps offshore Coal Oil Point, California. Petroleum recovered from Platform Holly in the Santa Barbara Channel, was added to a sediment-seawater mixture and the microcosm bottles were allowed to incubate under aerobic conditions for slightly more than 100 days. Comprehensive, two-dimensional gas chromatography was employed in this study to quantify changes in the concentrations of individual hydrocarbon compounds because of the increased resolution and resolving power provided with this robust analytical method. We show significant hydrocarbon mass loss due to aerobic biodegradation for hundreds of tracked compounds in the microcosm bottles. The results shown here provide quantitative evidence for broad-scale metabolic specificity during aerobic hydrocarbon degradation in surface and shallow subsurface marine sediments.

  9. A data acquisition system for two-dimensional position sensitive micropattern gas detectors with delay-line readout

    Energy Technology Data Exchange (ETDEWEB)

    Hanu, A.R., E-mail: hanua@mcmaster.ca [Department of Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Ontario, Canada L8S 4K1 (Canada); NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Prestwich, W.V.; Byun, S.H. [Department of Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Ontario, Canada L8S 4K1 (Canada)

    2015-04-21

    We present a data acquisition (DAQ) system for two-dimensional position sensitive micropattern gas detectors using the delay-line method for readout. The DAQ system consists of a field programmable gate array (FPGA) as the main data processor and our time-to-digital (TDC) mezzanine card for making time measurements. We developed the TDC mezzanine card around the Acam TDC-GPX ASIC and it features four independent stop channels referenced to a common start, a typical timing resolution of ~81 ps, and a 17-bit measurement range, and is compliant with the VITA 57.1 standard. For our DAQ system, we have chosen the Xilinx SP601 development kit which features a single Spartan 6 FPGA, 128 MB of DDR2 memory, and a serial USB interface for communication. Output images consist of 1024×1024 square pixels, where each pixel has a 32-bit depth and corresponds to a time difference of 162 ps relative to its neighbours. When configured for a 250 ns acquisition window, the DAQ can resolve periodic event rates up to 1.8×10{sup 6} Hz without any loses and will report a maximum event rate of 6.11×10{sup 5} Hz for events whose arrival times follow Poisson statistics. The integral and differential non-linearities have also been measured and are better than 0.1% and 1.5%, respectively. Unlike commercial units, our DAQ system implements the delay-line image reconstruction algorithm entirely in hardware and is particularly attractive for its modularity, low cost, ease of integration, excellent linearity, and high throughput rate.

  10. Analysis of sex pheromone gland content of individual Symmetrischema tangolias by means of direct gland introduction into a two-dimensional gas chromatograph

    NARCIS (Netherlands)

    Griepink, F.C.; Drijfhout, F.P.; Beek, van T.A.; Visser, H.J.; Groot, de C.P.G.M.

    2000-01-01

    The amounts and ratios of the four constituents of the sex pheromone gland of the moth Symmetrischema tangolias were measured during a 24-hr dark–light cycle. A new approach was followed that involved the direct introduction of sex pheromone glands into the liner of a two-dimensional gas chromatogra

  11. Characterisation of volatile components of Pinotage wines using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC x GC–TOFMS)

    NARCIS (Netherlands)

    Weldegergis, B.T.; Villiers, de A.; McNeish, C.; Seethapathy, S.; Mostafa, A.; Górecki, T.; Crouch, A.M.

    2011-01-01

    As part of the ongoing research into the chemical composition of the uniquely South African wine cultivar Pinotage, the volatile composition of nine young wines of this cultivar was investigated using comprehensive two-dimensional gas chromatography (GC × GC) in combination with time-of-flight mass

  12. Characterisation of volatile components of Pinotage wines using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC x GC–TOFMS)

    NARCIS (Netherlands)

    Weldegergis, B.T.; Villiers, de A.; McNeish, C.; Seethapathy, S.; Mostafa, A.; Górecki, T.; Crouch, A.M.

    2011-01-01

    As part of the ongoing research into the chemical composition of the uniquely South African wine cultivar Pinotage, the volatile composition of nine young wines of this cultivar was investigated using comprehensive two-dimensional gas chromatography (GC × GC) in combination with time-of-flight mass

  13. Effects of anisotropy and magnetic fields on the specific heat of a quasi-two-dimensional Boltzmann gas in an elliptical parabolic quantum dot

    Institute of Scientific and Technical Information of China (English)

    Zhai Zhi-Yuan; Li Yu-Qi; Pan Xiao-Yin

    2012-01-01

    We investigate the effects due to anisotropy and magnetic field interaction for a quasi-two-dimensional Boltzmann gas in an elliptical parabolic quantum dot.The specific heat is studied with varying temperature,anisotropy,and magnetic field strength.The cases without and with the inclusion of the spin Zeeman interaction are considered.

  14. AlGaAs/GaAs two-dimensional electron gas structures studied by photo reflectance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Guillen Cervantes, A; Rivera Alvarez, Z; Hernandez, F; Huerta, J. [Instituto Politecnico Nacional, Mexico, D.F. (Mexico); Mendez Garcia, V. H.; Lastras Martinez, A.; Zamora, L.; Saucedo, N. [Universidad Autonoma de San Luis Potosi, San Luis Potosi (Mexico); Melendez Lira, M; Lopez, M [Instituto Politecnico Nacional, Mexico, D.F. (Mexico)

    2001-12-01

    Al{sub x} Ga{sub 1}-x As/GaAs two-dimensional electron gas (2-DEG) heterostructures were fabricated by molecular beam epitaxy in three different laboratories. The samples were characterized by room temperature Photo reflectance (PR) spectroscopy and measurements at 77 K. Internal electric fields were detected by the presence of Franz-Keldysh (FK) oscillations in the PR spectra. >From a FK analysis we obtained the GaAs band-gap energy and the built-in electric field strength in each sample. On the other hand, in the energy region corresponding to Al{sub x} Ga{sub 1}-x As a broad PR signal was registered typical of a highly doped material. Using the third derivative theory we obtained the Al{sub x} Ga{sub 1}-x As band-gap energy, and from this value the Al concentration in the samples. Results showed that the sample with highest electron mobility exhibited the lowest internal electric field strength. [Spanish] Se fabricaron heteroestructuras del tipo Al{sub x} Ga{sub 1}-x As/GaAs con un gas de electrones en dos dimensiones por medio de epitaxia de haces moleculares en tres laboratorios diferentes. Las muestras se caracterizaron por fotorreflectancia (FR) a temperatura ambiente y por mediciones del efecto mayor a 77 K. Campos electricos internos se detectaron por la presencia de oscilaciones Franz-Leldysh (FK) en los espectros de FR. Del analisis de las oscilaciones FK obtuvimos la energia de la brecha prohibida del GaAs y la intensidad del campo electrico interno en cada muestra. Por otra parte, en la region de energia correspondiente al Al{sub x} Ga{sub 1}-x As observamos una senal de FR ancha, tipica de un material altamente impurificado. Usando la teoria de la tercera derivada, obtuvimos el valor de la brecha de energia del Al{sub x}Ga{sub 1}-xAs, y de este valor la concentracion de Al en las muestras. Los resultados mostraron que la estructura con el valor de movilidad electronica mas alto tiene la intensidad de campo electrico interno mas baja.

  15. A two-dimensional microscale model of gas exchange during photosynthesis in maize (Zea mays L.) leaves.

    Science.gov (United States)

    Retta, Moges; Ho, Quang Tri; Yin, Xinyou; Verboven, Pieter; Berghuijs, Herman N C; Struik, Paul C; Nicolaï, Bart M

    2016-05-01

    CO2 exchange in leaves of maize (Zea mays L.) was examined using a microscale model of combined gas diffusion and C4 photosynthesis kinetics at the leaf tissue level. Based on a generalized scheme of photosynthesis in NADP-malic enzyme type C4 plants, the model accounted for CO2 diffusion in a leaf tissue, CO2 hydration and assimilation in mesophyll cells, CO2 release from decarboxylation of C4 acids, CO2 fixation in bundle sheath cells and CO2 retro-diffusion from bundle sheath cells. The transport equations were solved over a realistic 2-D geometry of the Kranz anatomy obtained from light microscopy images. The predicted responses of photosynthesis rate to changes in ambient CO2 and irradiance compared well with those obtained from gas exchange measurements. A sensitivity analysis showed that the CO2 permeability of the mesophyll-bundle sheath and airspace-mesophyll interfaces strongly affected the rate of photosynthesis and bundle sheath conductance. Carbonic anhydrase influenced the rate of photosynthesis, especially at low intercellular CO2 levels. In addition, the suberin layer at the exposed surface of the bundle sheath cells was found beneficial in reducing the retro-diffusion. The model may serve as a tool to investigate CO2 diffusion further in relation to the Kranz anatomy in C4 plants.

  16. Rationally synthesized two-dimensional polymers.

    Science.gov (United States)

    Colson, John W; Dichtel, William R

    2013-06-01

    Synthetic polymers exhibit diverse and useful properties and influence most aspects of modern life. Many polymerization methods provide linear or branched macromolecules, frequently with outstanding functional-group tolerance and molecular weight control. In contrast, extending polymerization strategies to two-dimensional periodic structures is in its infancy, and successful examples have emerged only recently through molecular framework, surface science and crystal engineering approaches. In this Review, we describe successful 2D polymerization strategies, as well as seminal research that inspired their development. These methods include the synthesis of 2D covalent organic frameworks as layered crystals and thin films, surface-mediated polymerization of polyfunctional monomers, and solid-state topochemical polymerizations. Early application targets of 2D polymers include gas separation and storage, optoelectronic devices and membranes, each of which might benefit from predictable long-range molecular organization inherent to this macromolecular architecture.

  17. Topological defects in two-dimensional crystals

    OpenAIRE

    Chen, Yong; Qi, Wei-Kai

    2008-01-01

    By using topological current theory, we study the inner topological structure of the topological defects in two-dimensional (2D) crystal. We find that there are two elementary point defects topological current in two-dimensional crystal, one for dislocations and the other for disclinations. The topological quantization and evolution of topological defects in two-dimensional crystals are discussed. Finally, We compare our theory with Brownian-dynamics simulations in 2D Yukawa systems.

  18. Analysis of homogeneity of 2D electron gas at decreasing of electron density

    OpenAIRE

    Sherstobitov, A. A.; Minkov, G. M.; Germanenko, A. V.; Rut, O. E.; Soldatov, I. V.; Zvonkov, B. N.

    2010-01-01

    We investigate the gate voltage dependence of capacitance of a system gate - 2D electron gas (C-Vg). The abrupt drop of capacitance at decreasing concentration was found. The possible reasons of this drop, namely inhomogeneity of electron density distribution and serial resistance of 2D electron gas are discussed. Simultaneous analysis of gate voltage dependences of capacitance and resistance has shown that in heavily doped 2D systems the main role in the drop of capacitance at decreasing con...

  19. The Non-selfsimilar Riemann Problem for 2-D Zero-Pressure Flow in Gas Dynamics

    Institute of Scientific and Technical Information of China (English)

    Wenhua SUN; Wancheng SHENG

    2007-01-01

    The non-selfsimilar Riemann problem for two-dimensional zero-pressure flow in gas dynamics with two constant states separated by a convex curve is considered. By means of the generalized Rankine-Hugoniot relation and the generalized characteristic analysis method, the global solution involving delta shock wave and vacuum is constructed. The explicit solution for a special case is also given.

  20. Multidimensional gas chromatography for the detailed PIONA analysis of heavy naphtha: hyphenation of an olefin trap to comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    Vendeuvre, Colombe; Bertoncini, Fabrice; Espinat, Didier; Thiébaut, Didier; Hennion, Marie-Claire

    2005-10-07

    A multidimensional method providing the composition of a heavy naphtha in paraffins, isoparaffins, olefins, naphthenes, and aromatics (PIONA) in the C8-C14 range is presented. The analytical set-up consists in a silver modified silica olefin trap on-line coupled to comprehensive two-dimensional gas chromatography (GC x GC). In this configuration, hydrocarbons are separated, in gaseous state, in two fractions, saturate and unsaturate, each fraction being subsequently analysed by GC or by GC x GC. The resolution between saturates and olefins was found to be improved compared to a single GC x GC run. The characterisation of the olefin trap highlights the benefits and the limits related to the use of that stationary phase as a double bond selective fractionation medium.

  1. Vacuum ultraviolet absorption spectroscopy in combination with comprehensive two-dimensional gas chromatography for the monitoring of volatile organic compounds in breath gas: A feasibility study.

    Science.gov (United States)

    Gruber, Beate; Groeger, Thomas; Harrison, Dale; Zimmermann, Ralf

    2016-09-16

    Vacuum ultraviolet (VUV) absorption spectroscopy was recently introduced as a new detection system for one, as well as comprehensive two-dimensional gas chromatography (GC×GC) and successfully applied to the analysis of various analytes in several matrices. In this study, its suitability for the analysis of breath metabolites was investigated and the impact of a finite volume of the absorption cell and makeup gas pressure was evaluated for volatile analytes in terms of sensitivity and chromatographic resolution. A commercial available VUV absorption spectrometer was coupled to GC×GC and applied to the analysis of highly polar volatile organic compounds (VOCs). Breath gas samples were acquired by needle trap micro extraction (NTME) during a glucose challenge and analysed by the applied technique. Regarding qualitative and quantitative information, the VGA-100 is compatible with common GC×GC detection systems like FID and even TOFMS. Average peak widths of 300ms and LODs in the lower ng range were achieved using GC×GC-VUV. Especially small oxygenated breath metabolites show intense and characteristic absorption patterns in the VUV region. Challenge responsive VOCs could be identified and monitored during a glucose challenge. The new VUV detection technology might especially be of benefit for applications in clinical research.

  2. Determination of diamondoids in crude oils using gas purge microsyringe extraction with comprehensive two dimensional gas chromatography-time-of-flight mass spectrometry.

    Science.gov (United States)

    Zhang, Wanfeng; Zhu, Shukui; Pang, Liling; Gao, Xuanbo; Zhu, Gang-Tian; Li, Donghao

    2016-12-23

    Based on a homemade device, gas purge microsyringe extraction (GP-MSE) of crude oil samples was developed for the first time. As a simple, fast, low-cost, sensitive and solvent-saving technique, GP-MSE provides some outstanding advantages over the widely used sample preparation methods for crude oils such as column chromatography (ASTM D2549). Several parameters affecting extraction efficiency were optimized, including extraction temperature, extraction time, extraction solvent, condensing temperature and purge gas flow rate. With the optimized GP-MSE conditions, several real crude oil samples were extracted, and trace diamondoids were determined using comprehensive two dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS). In total, more than 100 diamondoids were detected and 27 marker compounds were identified and quantified accurately. The limits of detection (LODs, S/N=3) were less than 0.08μg/L for all diamondoids. The relative standard deviation (RSD) was below 8%, ranging from 1.1 to 7.6%. The linearity of the developed method was in the range of 0.5-100.0μg/L with correlation coefficients (R(2)) more than 0.996. The recoveries obtained at spiking 50μg/L were between 81 and 108% for diamondoids in crude oil samples. The developed method can also be extended to the analysis of other components in crude oils and other complex matrices.

  3. Terahertz signal detection in a short gate length field-effect transistor with a two-dimensional electron gas

    Energy Technology Data Exchange (ETDEWEB)

    Vostokov, N. V., E-mail: vostokov@ipm.sci-nnov.ru; Shashkin, V. I. [Institute for Physics of Microstructures of the Russian Academy of Sciences, 603950 Nizhny Novgorod, Russia and N. I. Lobachevsky State University of Nizhny Novgorod, 603950 Nizhny Novgorod (Russian Federation)

    2015-11-28

    We consider the problem of non-resonant detection of terahertz signals in a short gate length field-effect transistor having a two-dimensional electron channel with zero external bias between the source and the drain. The channel resistance, gate-channel capacitance, and quadratic nonlinearity parameter of the transistor during detection as a function of the gate bias voltage are studied. Characteristics of detection of the transistor connected in an antenna with real impedance are analyzed. The consideration is based on both a simple one-dimensional model of the transistor and allowance for the two-dimensional distribution of the electric field in the transistor structure. The results given by the different models are discussed.

  4. Measurements and analysis of Hall effect of a two dimensional electron gas in the close proximity of a superconducting YBa2Cu3O(7 - x) film

    Science.gov (United States)

    Tseng, M. Z.; Jiang, W. N.; Hu, E. L.

    1994-09-01

    A direct integration of YBa2Cu3O(7 - x) and a two dimensional electron gas Hall probe was made possible through the use of a MgO buffer layer. We demonstrate the use of this structure for the measurements of the magnetization hysteresis of a superconducting YBa2Cu3O(7 - x) thin film, and we make an estimate of the sensitivity and resolution that can be achieved with this probe structure. The close proximity of the YBa2Cu3O(7 - x) to the two dimensional electron gas (approximately 1700 A) allows sensitive measurements of interactions between the two; more importantly, closer superconductor-semiconductor spacing can be achieved without severe compromise of the component material quality.

  5. Comparison of column phase configurations for comprehensive two dimensional gas chromatographic analysis of crude oil and bitumen

    Energy Technology Data Exchange (ETDEWEB)

    Tran, T.C.; Harynuk, J.; Marriott, P. [RMIT University, Melbourne (Australia). Dept. of Applied Chemistry; Logan, G.A.; Grosjean, E. [Geoscience Australia, Canberra (Australia); Ryan, D. [Charles Sturt University, Wagga Wagga (Australia). School of Science and Technology

    2006-09-15

    An inverted phase (polar to non-polar) column set has been compared with a non-polar to polar column set for the GC x GC separation of petroleum hydrocarbons. This column configuration is shown to provide greatly enhanced resolution for less polar compounds and makes greater use of the two dimensional separation space. It improves resolution of a greater number of components within one analysis and offers new possibilities for crude oil fingerprinting. (Author)

  6. Full evaporation dynamic headspace in combination with selectable one-dimensional/two-dimensional gas chromatography-mass spectrometry for the determination of suspected fragrance allergens in cosmetic products.

    Science.gov (United States)

    Devos, Christophe; Ochiai, Nobuo; Sasamoto, Kikuo; Sandra, Pat; David, Frank

    2012-09-14

    Suspected fragrance allergens were determined in cosmetic products using a combination of full evaporation-dynamic headspace (FEDHS) with selectable one-dimensional/two-dimensional GC-MS. The full evaporation dynamic headspace approach allows the non-discriminating extraction and injection of both apolar and polar fragrance compounds, without contamination of the analytical system by high molecular weight non-volatile matrix compounds. The method can be applied to all classes of cosmetic samples, including water containing matrices such as shower gels or body creams. In combination with selectable (1)D/(2)D GC-MS, consisting of a dedicated heart-cutting GC-MS configuration using capillary flow technology (CFT) and low thermal mass GC (LTM-GC), a highly flexible and easy-to-use analytical solution is offered. Depending on the complexity of the perfume fraction, analyses can be performed in one-dimensional GC-MS mode or in heart-cutting two-dimensional GC-MS mode, without the need of hardware reconfiguration. The two-dimensional mode with independent temperature control of the first and second dimension column is especially useful to confirm the presence of detected allergen compounds when mass spectral deconvolution is not possible.

  7. Two-dimensional coupled electron-hole layers in high magnetic fields

    NARCIS (Netherlands)

    Parlangeli, Andrea

    2000-01-01

    In solids, it is nowadays possible to create structures in which electrons are confined into a two-dimensional (2D) plane. The physics of a 2D electron gas (2DEG) has proved to be very rich, in particular in the presence of a transverse magnetic field. The Quantum Hall Effect, i.e. the quantization

  8. [Characterization of compounds in crude oils by gas purge micro-syringe extraction coupled to comprehensive two-dimensional gas chromatography].

    Science.gov (United States)

    Tong, Ting; Zhang, Wanfeng; Li, Donghao; Zhao, Jinhua; Chang, Zhenyang; Gao, Xuanbo; Dai, Wei; He, Sheng; Zhu, Shukui

    2014-10-01

    A novel sample pretreatment method, gas purge micro-syringe extraction (GP- MSE), coupled to comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC x GC/TOFMS) has been developed for the characterization of volatile and semi-volatile compounds in crude oils. In the sample pretreatment process, the analytes were carried to the microsyringe barrel by inert gas, and at the same time, trapped by an organic solvent. The whole process of extraction takes less than 10 min, and only 20 μL of organic solvent was needed. Using two custom standard solutions containing alkanes and polycyclic aromatic hydrocarbons (PAHs), the influences of the extraction conditions were investigated. The optimized conditions were as follows: 5 mg crude oil, 20 μL hexane (extraction solvent), extraction for 3 min at 300 °C, condensation temperature set at -2 °C, gas flow rate set at 2 mL/min. Under the optimized conditions, a real crude oil sample was extracted and then analyzed in detail. It showed that the proposed method was very effective in simultaneously analyzing the normal and branched alkanes, cycloalkanes, aromatic hydrocarbons, and biomarkers of crude oil such as steranes and terpanes. The recoveries obtained ranged from 82.0% to 107.3% and the detection limits ranged from 34 to 93 μg/L. The correlation coefficients (R2) were more than 0.99. The relative standard deviations (RSDs, n = 5) for all the analytes were below 10%. The results indicate that the proposed method is suitable for the characterization of volatile and semi-volatile compounds in crude oils with easy operation, high sensitivity and efficiency.

  9. Elucidation of the aroma compositions of Zhenjiang aromatic vinegar using comprehensive two dimensional gas chromatography coupled to time-of-flight mass spectrometry and gas chromatography-olfactometry.

    Science.gov (United States)

    Zhou, Zhilei; Liu, Shuangping; Kong, Xiangwei; Ji, Zhongwei; Han, Xiao; Wu, Jianfeng; Mao, Jian

    2017-03-03

    In this work, a method to characterize the aroma compounds of Zhenjiang aromatic vinegar (ZAV) was developed using comprehensive two dimensional gas chromatography (GC×GC) coupled with time-of-flight mass spectrometry (TOFMS) and gas chromatography olfactometry (GC-O). The column combination was optimized and good separation was achieved. Structured chromatograms of furans and pyrazines were obtained and discussed. A total of 360 compounds were tentatively identified based on mass spectrum match factors, structured chromatogram and linear retention indices comparison. The most abundant class in number was ketones. A large number of esters, furans and derivatives, aldehydes and alcohols were also detected. The odor-active components were identified by comparison of the reported odor of the identified compounds with the odor of corresponding GC-O region. The odorants of methanethiol, 2-methyl-propanal, 2-methyl-butanal/3-methyl-butanal, octanal, 1-octen-3-one, dimethyl trisulfide, trimethyl-pyrazine, acetic acid, 3-(methylthio)-propanal, furfural, benzeneacetaldehyde, 3-methyl-butanoic acid/2-methyl-butanoic acid and phenethyl acetate were suspected to be the most potent. About half of them were identified as significant aroma constituents in ZAV for the first time. Their contribution to specific sensory attribute of ZAJ was also studied. The results indicated that the presented method is suitable for characterization of ZAV aroma constituents. This study also enriches our knowledge on the components and aroma of ZAV.

  10. Chemical characterization of aromatic compounds in extra heavy gas oil by comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry.

    Science.gov (United States)

    Avila, Bárbara M F; Pereira, Ricardo; Gomes, Alexandre O; Azevedo, Débora A

    2011-05-27

    Comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS) was used for the characterization of aromatic compounds present in extra heavy gas oil (EHGO) from Brazil. Individual identification of EHGO compounds was successfully achieved in addition to group-type separation on the chromatographic plane. Many aromatic hydrocarbons, especially polycyclic aromatic hydrocarbons and sulfur compounds, were detected and identified, such as chrysenes, phenanthrenes, perylenes, benzonaphthothiophenes and alkylbenzonaphthothiophenes. In addition, triaromatic steroids, methyl-triaromatic steroids, tetrahydrochrysenes and tetraromatic pentacyclic compounds were present in the EHGO aromatic fractions. Considering the roof-tile effect observed for many of these compound classes and the high number of individual compounds identified, GC×GC-TOFMS is an excellent technique to characterize the molecular composition of the aromatic fraction from EHGO samples. Moreover, data processing allowed the quantification of aromatic compounds, in class and individually, using external standards. EHGO data were obtained in μgg(-1), e.g., benzo[a]pyrene were in the range 351 to 1164μgg(-1). Thus, GC×GC-TOFMS was successfully applied in EHGO quantitative analysis.

  11. Determination of aromatic sulphur compounds in heavy gas oil by using (low-)flow modulated comprehensive two-dimensional gas chromatography-triple quadrupole mass spectrometry.

    Science.gov (United States)

    Franchina, Flavio Antonio; Machado, Maria Elisabete; Tranchida, Peter Quinto; Zini, Cláudia Alcaraz; Caramão, Elina Bastos; Mondello, Luigi

    2015-03-27

    The present research is focused on the development of a flow-modulated comprehensive two-dimensional gas chromatography-triple quadrupole mass spectrometry (FM GC × GC-MS/MS) method for the determination of classes of aromatic organic sulphur compounds (benzothiophenes, dibenzothiophenes, and benzonaphthothiophene) in heavy gas oil (HGO). The MS/MS instrument was used to provide both full-scan and multiple-reaction-monitoring (MRM) data. Linear retention index (LRI) ranges were used to define the MRM windows for each chemical class. Calibration solutions (internal standard: 1-fluoronaphthalene) were prepared by using an HGO sample, depleted of S compounds. Calibration information was also derived for the thiophene class (along with MRM and LRI data), even though such constituents were not present in the HGO. Linearity was satisfactory over the analyzed concentration range (1-100 mg/L); intra-day precision for the lowest calibration point was always below 17%. Accuracy was also satisfactory, with a maximum percentage error of 3.5% (absolute value) found among the S classes subjected to (semi-)quantification. The highest limit of quantification was calculated to be 299 μg/L (for the C1-benzothiophene class), while the lowest was 21 μg/L (for the C4-benzothiophene class).

  12. Ultra resolution chemical fingerprinting of dense non-aqueous phase liquids from manufactured gas plants by reversed phase comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    McGregor, Laura A; Gauchotte-Lindsay, Caroline; Daéid, Niamh Nic; Thomas, Russell; Daly, Paddy; Kalin, Robert M

    2011-07-22

    Ultra resolution chemical fingerprinting of dense non-aqueous phase liquids (DNAPLs) from former manufactured gas plants (FMGPs) was investigated using comprehensive two-dimensional gas chromatography coupled with time of flight mass spectrometry (GC×GC TOFMS). Reversed phase GC×GC (i.e. a polar primary column coupled to a non-polar secondary column) was found to significantly improve the separation of polycyclic aromatic hydrocarbons (PAHs) and their alkylated homologues. Sample extraction and cleanup was performed simultaneously using accelerated solvent extraction (ASE), with recovery rates between 76% and 97%, allowing fast, efficient extraction with minimal solvent consumption. Principal component analysis (PCA) of the GC×GC data was performed in an attempt to differentiate between twelve DNAPLs based on their chemical composition. Correlations were discovered between DNAPL composition and historic manufacturing processes used at different FMGP sites. Traditional chemical fingerprinting methods generally follow a tiered approach with sample analysis on several different instruments. We propose ultra resolution chemical fingerprinting as a fast, accurate and precise method of obtaining more chemical information than traditional tiered approaches while using only a single analytical technique.

  13. Terahertz optical-Hall effect characterization of two-dimensional electron gas properties in AlGaN/GaN high electron mobility transistor structures

    Science.gov (United States)

    Schöche, S.; Shi, Junxia; Boosalis, A.; Kühne, P.; Herzinger, C. M.; Woollam, J. A.; Schaff, W. J.; Eastman, L. F.; Schubert, M.; Hofmann, T.

    2011-02-01

    The free-charge carrier mobility, sheet density, and effective mass of a two-dimensional electron gas are exemplarily determined in the spectral range from 640 GHz to 1 THz in a AlGaN/GaN heterostructure using the optical-Hall effect at room temperature. Complementary midinfrared spectroscopic ellipsometry measurements are performed for analysis of heterostructure constituents layer thickness, phonon mode, and free-charge carrier parameters. The electron effective mass is determined to be (0.22±0.04)m0. The high-frequency sheet density and carrier mobility parameters are in good agreement with results from dc electrical Hall effect measurements, indicative for frequency-independent carrier scattering mechanisms of the two-dimensional carrier distribution.

  14. Determination of scale-invariant equations of state without fitting parameters: application to the two-dimensional Bose gas across the Berezinskii-Kosterlitz-Thouless transition.

    Science.gov (United States)

    Desbuquois, Rémi; Yefsah, Tarik; Chomaz, Lauriane; Weitenberg, Christof; Corman, Laura; Nascimbène, Sylvain; Dalibard, Jean

    2014-07-11

    We present a general "fit-free" method for measuring the equation of state (EoS) of a scale-invariant gas. This method, which is inspired from the procedure introduced by Ku et al. [Science 335, 563 (2012)] for the unitary three-dimensional Fermi gas, provides a general formalism which can be readily applied to any quantum gas in a known trapping potential, in the frame of the local density approximation. We implement this method on a weakly interacting two-dimensional Bose gas across the Berezinskii-Kosterlitz-Thouless transition and determine its EoS with unprecedented accuracy in the critical region. Our measurements provide an important experimental benchmark for classical-field approaches which are believed to accurately describe quantum systems in the weakly interacting but nonperturbative regime.

  15. A high-mobility two-dimensional electron gas at the spinel/perovskite interface of γ-Al2O3/SrTiO3

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Bovet, N.; Trier, Felix

    2013-01-01

    The discovery of two-dimensional electron gases at the heterointerface between two insulating perovskite-type oxides, such as LaAlO3 and SrTiO3, provides opportunities for a new generation of all-oxide electronic devices. Key challenges remain for achieving interfacial electron mobilities much be...... confined within a layer of 0.9 nm in proximity to the interface. Our findings pave the way for studies of mesoscopic physics with complex oxides and design of high-mobility all-oxide electronic devices.......The discovery of two-dimensional electron gases at the heterointerface between two insulating perovskite-type oxides, such as LaAlO3 and SrTiO3, provides opportunities for a new generation of all-oxide electronic devices. Key challenges remain for achieving interfacial electron mobilities much...... beyond the current value of approximately 1,000 cm2V-1 s-1 (at low temperatures). Here we create a new type of two-dimensional electron gas at the heterointerface between SrTiO3 and a spinel g-Al2O3 epitaxial film with compatible oxygen ions sublattices. Electron mobilities more than one order...

  16. Characterization of sulfur compounds in whisky by full evaporation dynamic headspace and selectable one-dimensional/two-dimensional retention time locked gas chromatography-mass spectrometry with simultaneous element-specific detection.

    Science.gov (United States)

    Ochiai, Nobuo; Sasamoto, Kikuo; MacNamara, Kevin

    2012-12-28

    A method is described for characterization of sulfur compounds in unaged and aged whisky. The method is based on full evaporation dynamic headspace (FEDHS) of 100 μL of whisky samples followed by selectable one-dimensional ((1)D) or two-dimensional ((2)D) retention-time-locked (RTL) gas chromatography (GC)-mass spectrometry (MS) with simultaneous element-specific detection using a sulfur chemiluminescence detector (SCD) and a nitrogen chemiluminescence detector (NCD). Sequential heart-cuts of the 16 sulfur fractions were used to identify each individual sulfur compound in the unaged whisky. Twenty sulfur compounds were positively identified by a MS library search, linear retention indices (LRI), and formula identification using MS calibration software. Additionally eight formulas were also identified for unknown sulfur compounds. Simultaneous heart-cuts of the 16 sulfur fractions were used to produce the (2)D RTL GC-SCD chromatograms for principal component analysis. PCA of the (2)D RTL GC-SCD data clearly demonstrated the difference between unaged and aged whisky, as well as two different whisky samples. Fourteen sulfur compounds could be characterized as key sulfur compounds responsible for the changes in the aging step and/or the difference between two kinds of whisky samples. The determined values of the key sulfur compounds were in the range of 0.3-210 ng mL(-1) (RSD: 0.37-12%, n=3).

  17. Two-Dimensional Planetary Surface Lander

    Science.gov (United States)

    Hemmati, H.; Sengupta, A.; Castillo, J.; McElrath, T.; Roberts, T.; Willis, P.

    2014-06-01

    A systems engineering study was conducted to leverage a new two-dimensional (2D) lander concept with a low per unit cost to enable scientific study at multiple locations with a single entry system as the delivery vehicle.

  18. Evolution and structure of the plasma of current sheets forming in two-dimensional magnetic fields with a null line at low initial gas ionization and their interpretation

    Science.gov (United States)

    Ostrovskaya, G. V.; Frank, A. G.

    2012-04-01

    An analysis of the experimental data obtained by holographic interferometry in our work [1] makes it possible to explain most of the observed specific features of the structure and evolution of the plasma sheets developing in a two-dimensional magnetic field with a null line in a plasma with a low initial degree of ionization (≈10-4). The following two processes are shown to play a key role here: additional gas ionization in an electric field and the peculiarities of plasma dynamics in a current sheet expanding in time.

  19. One-dimensional lattices topologically equivalent to two-dimensional lattices within the context of the lattice gas model. II The triangular lattice

    Science.gov (United States)

    Costanza, E. F.; Costanza, G.

    2016-12-01

    Continuum partial differential equations are obtained from a set of discrete stochastic evolution equations of both non-Markovian and Markovian processes and applied to the diffusion within the context of the lattice gas model. A procedure allowing to construct one-dimensional lattices that are topologically equivalent to two-dimensional lattices is described in detail in the case of a triangular lattice. This example shows the general features that possess the procedure and extensions are also suggested in order to provide a wider insight in the present approach.

  20. Onset of quantum criticality in the topological-to-nematic transition in a two-dimensional electron gas at filling factor ν =5 /2

    Science.gov (United States)

    Schreiber, K. A.; Samkharadze, N.; Gardner, G. C.; Biswas, Rudro R.; Manfra, M. J.; Csáthy, G. A.

    2017-07-01

    Under hydrostatic pressure, the ground state of a two-dimensional electron gas at ν =5 /2 changes from a fractional quantum Hall state to the stripe phase. By measuring the energy gap of the fractional quantum Hall state and of the onset temperature of the stripe phase, we mapped out a phase diagram of these competing phases in the pressure-temperature plane. Our data highlight the dichotomy of two descriptions of the half-filled Landau level near the quantum critical point: one based on electrons and another on composite fermions.

  1. Acoustic phonon-limited resistivity of spin-orbit coupled two-dimensional electron gas: the deformation potential and piezoelectric scattering.

    Science.gov (United States)

    Biswas, Tutul; Ghosh, Tarun Kanti

    2013-01-23

    We study the interaction between electron and acoustic phonons in a Rashba spin-orbit coupled two-dimensional electron gas using Boltzmann transport theory. Both the deformation potential and piezoelectric scattering mechanisms are considered in the Bloch-Grüneisen (BG) regime as well as in the equipartition (EP) regime. The effect of the Rashba spin-orbit interaction on the temperature dependence of the resistivity in the BG and EP regimes is discussed. We find that the effective exponent of the temperature dependence of the resistivity in the BG regime decreases due to spin-orbit coupling.

  2. Enantioselective comprehensive two-dimensional gas chromatography. A route to elucidate the authenticity and origin of Rosa damascena Miller essential oils.

    Science.gov (United States)

    Krupčík, Ján; Gorovenko, Roman; Špánik, Ivan; Sandra, Pat; Armstrong, Daniel W

    2015-10-01

    The analysis of Bulgarian and Turkish Rosa damascena Miller essential oils was performed by flow-modulated comprehensive two-dimensional gas chromatography using simultaneous detection of the second column effluent by flame ionization and quadrupole mass spectrometric detection. Enantioselective separations were obtained by running the samples on 2,3-di-O-ethyl-6-O-tert-butyldimethylsilyl-β-cyclodextrin column as the first column and on polyethylene glycol as the second column. The determination of enantiomeric or diastereomeric excess of some terpenoic solutes is a possible route for quality or authenticity control as well as for the elucidation of the country of origin.

  3. Suppression of the two-dimensional electron gas in LaGaO3/SrTiO3 by cation intermixing

    KAUST Repository

    Nazir, S.

    2013-12-03

    Cation intermixing at the n-type polar LaGaO 3 /SrTiO 3 (001) interface is investigated by first principles calculations. Ti"Ga, Sr"La, and SrTi"LaGa intermixing are studied in comparison to each other, with a focus on the interface stability. We demonstrate in which cases intermixing is energetically favorable as compared to a clean interface. A depopulation of the Ti 3d xy orbitals under cation intermixing is found, reflecting a complete suppression of the two-dimensional electron gas present at the clean interface.

  4. One-dimensional lattices topologically equivalent to two-dimensional lattices within the context of the lattice gas model, III. The hexagonal lattice

    Science.gov (United States)

    Costanza, E. F.; Costanza, G.

    2017-02-01

    Continuum partial differential equations are obtained from a set of discrete stochastic evolution equations of both non-Markovian and Markovian processes and applied to the diffusion within the context of the lattice gas model. A procedure allowing to construct one-dimensional lattices that are topologically equivalent to two-dimensional lattices is described in detail in the case of a hexagonal lattice which has the particular feature that need four types of dynamical variables. This example shows additional features to the general procedure and some extensions are also suggested in order to provide a wider insight in the present approach.

  5. Giant spin splitting of the two-dimensional electron gas at the surface of SrTiO3

    Science.gov (United States)

    Santander-Syro, A. F.; Fortuna, F.; Bareille, C.; Rödel, T. C.; Landolt, G.; Plumb, N. C.; Dil, J. H.; Radović, M.

    2014-12-01

    Two-dimensional electron gases (2DEGs) forming at the interfaces of transition metal oxides exhibit a range of properties, including tunable insulator-superconductor-metal transitions, large magnetoresistance, coexisting ferromagnetism and superconductivity, and a spin splitting of a few meV (refs , ). Strontium titanate (SrTiO3), the cornerstone of such oxide-based electronics, is a transparent, non-magnetic, wide-bandgap insulator in the bulk, and has recently been found to host a surface 2DEG (refs , , , ). The most strongly confined carriers within this 2DEG comprise two subbands, separated by an energy gap of 90 meV and forming concentric circular Fermi surfaces. Using spin- and angle-resolved photoemission spectroscopy (SARPES), we show that the electron spins in these subbands have opposite chiralities. Although the Rashba effect might be expected to give rise to such spin textures, the giant splitting of almost 100 meV at the Fermi level is far larger than anticipated. Moreover, in contrast to a simple Rashba system, the spin-polarized subbands are non-degenerate at the Brillouin zone centre. This degeneracy can be lifted by time-reversal symmetry breaking, implying the possible existence of magnetic order. These results show that confined electronic states at oxide surfaces can be endowed with novel, non-trivial properties that are both theoretically challenging to anticipate and promising for technological applications.

  6. Absence of localization in disordered two-dimensional electron gas at weak magnetic field and strong spin-orbit coupling

    Science.gov (United States)

    Su, Ying; Wang, C.; Avishai, Y.; Meir, Yigal; Wang, X. R.

    2016-09-01

    The one-parameter scaling theory of localization predicts that all states in a disordered two-dimensional system with broken time reversal symmetry are localized even in the presence of strong spin-orbit coupling. While at constant strong magnetic fields this paradigm fails (recall the quantum Hall effect), it is believed to hold at weak magnetic fields. Here we explore the nature of quantum states at weak magnetic field and strongly fluctuating spin-orbit coupling, employing highly accurate numerical procedure based on level spacing distribution and transfer matrix technique combined with one parameter finite-size scaling hypothesis. Remarkably, the metallic phase, (known to exist at zero magnetic field), persists also at finite (albeit weak) magnetic fields, and eventually crosses over into a critical phase, which has already been confirmed at high magnetic fields. A schematic phase diagram drawn in the energy-magnetic field plane elucidates the occurrence of localized, metallic and critical phases. In addition, it is shown that nearest-level statistics is determined solely by the symmetry parameter β and follows the Wigner surmise irrespective of whether states are metallic or critical.

  7. Detailed compositional characterization of plastic waste pyrolysis oil by comprehensive two-dimensional gas-chromatography coupled to multiple detectors.

    Science.gov (United States)

    Toraman, Hilal E; Dijkmans, Thomas; Djokic, Marko R; Van Geem, Kevin M; Marin, Guy B

    2014-09-12

    The detailed compositional characterization of plastic waste pyrolysis oil was performed with comprehensive two-dimensional GC (GC×GC) coupled to four different detectors: a flame ionization detector (FID), a sulfur chemiluminescence detector (SCD), a nitrogen chemiluminescence detector (NCD) and a time of flight mass spectrometer (TOF-MS). The performances of different column combinations were assessed in normal i.e. apolar/mid-polar and reversed configurations for the GC×GC-NCD and GC×GC-SCD analyses. The information obtained from the four detectors and the use of internal standards, i.e. 3-chlorothiophene for the FID and the SCD and 2-chloropyridine for the NCD analysis, enabled the identification and quantification of the pyrolysis oil in terms of both group type and carbon number: hydrocarbon groups (n-paraffins, iso-paraffins, olefins and naphthenes, monoaromatics, naphthenoaromatics, diaromatics, naphthenodiaromatics, triaromatics, naphthenotriaromatics and tetra-aromatics), nitrogen (nitriles, pyridines, quinolines, indole, caprolactam, etc.), sulfur (thiols/sulfides, thiophenes/disulfides, benzothiophenes, dibenzothiophenes, etc.) and oxygen containing compounds (ketones, phenols, aldehydes, ethers, etc.). Quantification of trace impurities is illustrated for indole and caprolactam. The analyzed pyrolysis oil included a significant amount of nitrogen containing compounds (6.4wt%) and to a lesser extent sulfur containing compounds (0.6wt%). These nitrogen and sulfur containing compounds described approximately 80% of the total peak volume for respectively the NCD and SCD analysis. TOF-MS indicated the presence of the oxygen containing compounds. However only a part of the oxygen containing compounds (2.5wt%) was identified because of their low concentrations and possible overlap with the complex hydrocarbon matrix as no selective detector or preparative separation for oxygen compounds was used.

  8. Identification of volatiles from pineapple (Ananas comosus L.) pulp by comprehensive two-dimensional gas chromatography and gas chromatography/mass spectrometry.

    Science.gov (United States)

    Pedroso, Marcio P; Ferreira, Ernesto C; Hantao, Leandro W; Bogusz, Stanislau; Augusto, Fabio

    2011-07-01

    Combining qualitative data from the chromatographic structure of 2-D gas chromatography with flame ionization detection (GC×GC-FID) and that from gas chromatography-mass spectrometry (GC/MS) should result in a more accurate assignment of the peak identities than the simple analysis by GC/MS, where coelution of analytes is unavoidable in highly complex samples (rendering spectra unsuitable for qualitative purposes) or for compounds in very low concentrations. Using data from GC×GC-FID combined with GC/MS can reveal coelutions that were not detected by mass spectra deconvolution software. In addition, some compounds can be identified according to the structure of the GC×GC-FID chromatogram. In this article, the volatile fractions of fresh and dehydrated pineapple pulp were evaluated. The extraction of the volatiles was performed by dynamic headspace extraction coupled to solid-phase microextraction (DHS-SPME), a technique appropriate for slurries or solid matrices. Extracted analytes were then analyzed by GC×GC-FID and GC/MS. The results obtained using both techniques were combined to improve compound identifications.

  9. Si-B-C陶瓷涂敷2D C/SiC复合材料的抗氧化性能%Oxidation resistance of two dimensional C/SiC composite coated with Si-B-C ceramic

    Institute of Scientific and Technical Information of China (English)

    左新章; 张立同; 刘永胜; 成来飞; 龚慧灵

    2013-01-01

    Two dimensional C/SiC composite coated with Si-B-C ceramic was prepared via chemical vapor deposition (CVD).Properties and structure evolution and self-healing mechanisms of the C/SiC composite were studied after oxidation for 10 h during 700-1200 ℃.At the same time,the evolution of morphologies,composition and phase for Si-B-C ceramic were also investigated.The experimental results show that the oxidation of Si-B-C ceramic accelerates with the temperature increasing,however,the oxidation scale is shallow and no more than 7 μm.With the temperature increasing,viscosity of borosilicate glass oxidized from Si-B-C ceramic reduces but volatilization accelerates.When the temperature increases to 1200 ℃,SiO2 crystallizes from borosilicate glass.C/SiC composite coated with Si-B-C ceramic shows an excellent oxidation resistance.Mass loss increases with temperature increasing,which is only 0.47% after oxidation for 10 h at 1200 ℃.Furthermore,the strength retention ratio is 91.6% at 1000 ℃,higher than that at other temperatures.The main mechanisms for excellent oxidation resistance of C/SiC composite is that borosilicatc glass oxidized from Si-B-C ceramic can seal cracks in composite effectively.%利用化学气相沉积(CVD)法制备了Si-B-C陶瓷涂敷改性的2D C/SiC复合材料,研究了其在700~1200℃氧化10 h性能和结构的演变规律以及自愈合机制,同时获得了Si-B-C涂层在不同温度氧化后的形貌、组分和物相转变规律.结果表明:涂敷在复合材料表面的Si-B-C陶瓷随温度的升高氧化加快,但氧化程度较低,不深于7μm;随温度的升高,氧化形成的硅硼玻璃黏度降低,挥发增强;当温度达到1200℃时,硅硼玻璃析出SiO2晶体;Si-B-C陶瓷涂敷改性的C/SiC具有优良的抗氧化性能,随氧化温度的升高,复合材料失重率增加,但在1200℃氧化10h后失重率仅为0.47%;此外材料在1000℃氧化后的强度保持率最高,达到91.6%,Si-B-C陶瓷氧化形

  10. Proximity Induced Superconducting Properties in One and Two Dimensional Semiconductors

    DEFF Research Database (Denmark)

    Kjærgaard, Morten

    a voltage is passed through the Josephson junction, we observe multiple Andreev reflections and preliminary results point to a highly transmissive interface between the 2D electron gas and the superconductor. In the theoretical section we demonstrate analytically and numerically, that in a 1D nanowire......This report is concerned with the properties of one and two dimensional semiconducting materials when brought into contact with a superconductor. Experimentally we study the 2D electron gas in an InGaAs/InAs heterostructure with aluminum grown in situ on the surface, and theoretically we show...... that a superconducting 1D nanowire can harbor Majorana bound states in the absence of spin–orbit coupling. We fabricate and measure micrometer–sized mesoscopic devices demonstrating the inheritance of superconducting properties in the 2D electron gas. By placing a quantum point contact proximal to the interface between...

  11. Two-dimensional gas chromatography and trilinear partial least squares for the quantitative analysis of aromatic and naphthene content in naphtha.

    Science.gov (United States)

    Prazen, B J; Johnson, K J; Weber, A; Synovec, R E

    2001-12-01

    Quantitative analysis of naphtha samples is demonstrated using comprehensive two-dimensional gas chromatography (GC x GC) and chemometrics. This work is aimed at providing a GC system for the quantitative and qualitative analysis of complex process streams for process monitoring and control. The high-speed GC x GC analysis of naphtha is accomplished through short GC columns, high carrier gas velocities, and partial chromatographic peak resolution followed by multivariate quantitative analysis. Six min GC x GC separations are analyzed with trilinear partial least squares (tri-PLS) to predict the aromatic and naphthene (cycloalkanes) content of naphtha samples. The 6-min GC x GC separation time is over 16 times faster than a single-GC-column standard method in which a single-column separation resolves the aromatic and naphthene compounds in naphtha and predicts the aromatic and naphthene percent concentrations through addition of the resolved signals. Acceptable quantitative precision is provided by GC x GC/tri-PLS.

  12. Identification and quantification of alkene-based drilling fluids in crude oils by comprehensive two-dimensional gas chromatography with flame ionization detection.

    Science.gov (United States)

    Reddy, Christopher M; Nelson, Robert K; Sylva, Sean P; Xu, Li; Peacock, Emily A; Raghuraman, Bhavani; Mullins, Oliver C

    2007-04-27

    Comprehensive two-dimensional gas chromatography with flame ionization detection (GC x GC-FID) was used to measure alkene-based drilling fluids in crude oils. Compared to one-dimensional gas chromatography, GC x GC-FID is more robust for detecting alkenes due to the increased resolution afforded by second dimension separations. Using GC x GC-FID to analyze four oil samples from one reservoir contaminated with the same drilling fluid, C(15), C(16), C(17), C(18) and C(20) alkenes were identified. The drilling fluid that contaminated these samples also differed from another commercially obtained fluid, which only contained C(16) and C(18) alkenes. These results should motivate the petroleum industry to consider GC x GC-FID for measuring drilling fluids.

  13. Flow-modulated comprehensive two-dimensional gas chromatography combined with a vacuum ultraviolet detector for the analysis of complex mixtures.

    Science.gov (United States)

    Zoccali, Mariosimone; Schug, Kevin A; Walsh, Phillip; Smuts, Jonathan; Mondello, Luigi

    2017-05-12

    The present paper is focused on the use of a vacuum ultraviolet absorption spectrometer (VUV) for gas chromatography (GC), within the context of flow modulated comprehensive two-dimensional gas chromatography (FM GC×GC). The features of the VUV detector were evaluated through the analysis of petrochemical and fatty acids samples. Besides responding in a predictable fashion via Beer's law principles, the detector provides additional spectroscopic information for qualitative analysis. Virtually all chemical species absorb and have unique gas phase absorption features in the 120-240nm wavelength range monitored. The VUV detector can acquire up to 90 full range absorption spectra per second, allowing its coupling with comprehensive two-dimensional gas chromatography. This recent form of detection can address specific limitations related to mass spectrometry (e.g., identification of isobaric and isomeric species with very similar mass spectra or labile chemical compounds), and it is also able to deconvolute co-eluting peaks. Moreover, it is possible to exploit a pseudo-absolute quantitation of analytes based on pre-recorded absorption cross-sections for target analytes, without the need for traditional calibration. Using this and the other features of the detector, particular attention was devoted to the suitability of the FM GC×GC-VUV system toward qualitative and quantitative analysis of bio-diesel fuel and different kinds of fatty acids. Satisfactory results were obtained in terms of tailing factor (1.1), asymmetry factor (1.1), and similarity (average value 97%), for the FAMEs mixtures analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. 2D fluid model analysis for the effect of 3D gas flow on a capacitively coupled plasma deposition reactor

    Science.gov (United States)

    Kim, Ho Jun; Lee, Hae June

    2016-06-01

    The wide applicability of capacitively coupled plasma (CCP) deposition has increased the interest in developing comprehensive numerical models, but CCP imposes a tremendous computational cost when conducting a transient analysis in a three-dimensional (3D) model which reflects the real geometry of reactors. In particular, the detailed flow features of reactive gases induced by 3D geometric effects need to be considered for the precise calculation of radical distribution of reactive species. Thus, an alternative inclusive method for the numerical simulation of CCP deposition is proposed to simulate a two-dimensional (2D) CCP model based on the 3D gas flow results by simulating flow, temperature, and species fields in a 3D space at first without calculating the plasma chemistry. A numerical study of a cylindrical showerhead-electrode CCP reactor was conducted for particular cases of SiH4/NH3/N2/He gas mixture to deposit a hydrogenated silicon nitride (SiN x H y ) film. The proposed methodology produces numerical results for a 300 mm wafer deposition reactor which agree very well with the deposition rate profile measured experimentally along the wafer radius.

  15. Two-dimensional cubic convolution.

    Science.gov (United States)

    Reichenbach, Stephen E; Geng, Frank

    2003-01-01

    The paper develops two-dimensional (2D), nonseparable, piecewise cubic convolution (PCC) for image interpolation. Traditionally, PCC has been implemented based on a one-dimensional (1D) derivation with a separable generalization to two dimensions. However, typical scenes and imaging systems are not separable, so the traditional approach is suboptimal. We develop a closed-form derivation for a two-parameter, 2D PCC kernel with support [-2,2] x [-2,2] that is constrained for continuity, smoothness, symmetry, and flat-field response. Our analyses, using several image models, including Markov random fields, demonstrate that the 2D PCC yields small improvements in interpolation fidelity over the traditional, separable approach. The constraints on the derivation can be relaxed to provide greater flexibility and performance.

  16. Stationary phase selection and comprehensive two-dimensional gas chromatographic analysis of trace biodiesel in petroleum-based fuel.

    Science.gov (United States)

    Seeley, John V; Bates, Carly T; McCurry, James D; Seeley, Stacy K

    2012-02-24

    The GC×GC solvation parameter model has been used to identify effective stationary phases for the separation of fatty acid methyl esters (FAMEs) from petroleum hydrocarbons. This simple mathematical model was used to screen the 1225 different combinations of 50 stationary phases. The most promising pairs combined a poly(methyltrifluoropropylsiloxane) stationary phase with a poly(dimethyldiphenylsiloxane) stationary phase. The theoretical results were experimentally tested by equipping a GC×GC instrument with a DB-210 primary stationary phase and an HP-50+ secondary stationary phase. This instrument was used to analyze trace levels of FAMEs in kerosene. The FAMEs were fully separated from the petroleum hydrocarbons on the secondary dimension of the 2-D chromatogram. The resulting GC×GC method was shown to be capable of accurately quantifying FAME levels as low as 2 ppm (w/w). These results demonstrate the utility of the solvation parameter model for identifying optimal stationary phases for high resolution GC×GC separations. Furthermore, this work presents an effective method for determining the level of biodiesel contamination in aviation fuel and other petroleum-based fuels. Copyright © 2011 Elsevier B.V. All rights reserved.

  17. Two-dimensional subwavelength plasmonic lattice solitons

    CERN Document Server

    Ye, F; Hu, B; Panoiu, N C

    2010-01-01

    We present a theoretical study of plasmonic lattice solitons (PLSs) formed in two-dimensional (2D) arrays of metallic nanowires embedded into a nonlinear medium with Kerr nonlinearity. We analyze two classes of 2D PLSs families, namely, fundamental and vortical PLSs in both focusing and defocusing media. Their existence, stability, and subwavelength spatial confinement are studied in detai

  18. Quantification of trace O-containing compounds in GTL process samples via Fischer-Tropsch reaction by comprehensive two-dimensional gas chromatography/mass spectrometry.

    Science.gov (United States)

    Fernandes, Daniella R; Pereira, Vinícius B; Stelzer, Karen T; Gomes, Alexandre O; Neto, Francisco R Aquino; Azevedo, Débora A

    2015-11-01

    Comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS) was successfully applied to eight real Brazilian Fischer-Tropsch (FT) product samples for the quantitative analysis of O-containing compounds. It not only allowed identifying and quantifying simultaneously a large number of O-containing compounds but also resolved many co-eluting components, such as carboxylic acids, which co-elute in one-dimensional gas chromatography. The homologous series of alcohols and carboxylic acids as trimethylsilyl derivatives were detected and identified at trace levels. The absolute quantification of each compound was accomplished with reliability using analytical curves. Linear alcohols (from C5 to C19), branched alcohols (C6-C13) and carboxylic acids (C4 to C12) were obtained in the range of 1.58 mg g(-1) to 14.75 mg g(-1), 0.51 mg g(-1) to 1.12 mg g(-1) and 0.21 mg g(-1) to 1.63 mg g(-1) of FT product samples, respectively. GC×GC-TOFMS provided a linear range (from 0.3 ng µL(-1) to 10 ng µL(-1)), good precision (gas-to-liquid technologies from natural gas and guide the choice of an FT conversion process that generates clean products with higher added value.

  19. Local doping of two-dimensional materials

    Science.gov (United States)

    Wong, Dillon; Velasco, Jr, Jairo; Ju, Long; Kahn, Salman; Lee, Juwon; Germany, Chad E.; Zettl, Alexander K.; Wang, Feng; Crommie, Michael F.

    2016-09-20

    This disclosure provides systems, methods, and apparatus related to locally doping two-dimensional (2D) materials. In one aspect, an assembly including a substrate, a first insulator disposed on the substrate, a second insulator disposed on the first insulator, and a 2D material disposed on the second insulator is formed. A first voltage is applied between the 2D material and the substrate. With the first voltage applied between the 2D material and the substrate, a second voltage is applied between the 2D material and a probe positioned proximate the 2D material. The second voltage between the 2D material and the probe is removed. The first voltage between the 2D material and the substrate is removed. A portion of the 2D material proximate the probe when the second voltage was applied has a different electron density compared to a remainder of the 2D material.

  20. Comprehensive two-dimensional gas chromatography in combination with rapid scanning quadrupole mass spectrometry in perfume analysis.

    Science.gov (United States)

    Mondello, Luigi; Casillia, Alessandro; Tranchida, Peter Quinto; Dugo, Giovanni; Dugo, Paola

    2005-03-04

    Single column gas chromatography (GC) in combination with a flame ionization detector (FID) and/or a mass spectrometer is routinely employed in the determination of perfume profiles. The latter are to be considered medium to highly complex matrices and, as such, can only be partially separated even on long capillaries. Inevitably, several monodimensional peaks are the result of two or more overlapping components, often hindering reliable identification and quantitation. The present investigation is based on the use of a comprehensive GC (GC x GC) method, in vacuum outlet conditions, for the near to complete resolution of a complex perfume sample. A rapid scanning quadrupole mass spectrometry (qMS) system, employed for the assignment of GC x GC peaks, supplied high quality mass spectra. The validity of the three-dimensional (3D) GC x GC-qMS application was measured and compared to that of GC-qMS analysis on the same matrix. Peak identification, in all applications, was achieved through MS spectra library matching and the interactive use of linear retention indices (LRI).

  1. Cooperative Reformable Channel System with Unique Recognition of Small Gas Molecules in a two-dimensional ZIF-membrane

    Science.gov (United States)

    Motevalli, Benyamin; Taherifar, Neda; Liu, Zhe

    We report a cooperative reformable channel system in a coordination porous polymer, named as ZIF-L. Three types of local flexible ligands coexist in the crystal structure of this polymer, resulting in ultra-flexibility. The reformable channel is able to regulate permeation of a nonspherical guest molecule, such as N2 or CO2, based on its longer molecular dimension, which is in a striking contrast to conventional molecular sieves that regulate the shorter cross-sectional dimension of the guest molecules. Our density functional theory (DFT) calculations reveal that the guest molecule induces dynamic motion of the flexible ligands, leading to the channel reformation, and then the guest molecule reorientates itself to fit in the reformed channel. Such a unique ``induced fit-in'' mechanism causes the gas molecule to pass through 6 membered-ring windows in the c- crystal direction of ZIF-L with its longer axis parallel to the window plane. Our experimental permeance of N2 through the ZIF-L membranes is about three times greater than that of CO2, supporting the DFT simulation predictions.

  2. In Silico Modeling of Hundred Thousand Experiments for Effective Selection of Ionic Liquid Phase Combinations in Comprehensive Two-Dimensional Gas Chromatography.

    Science.gov (United States)

    Nolvachai, Yada; Kulsing, Chadin; Marriott, Philip J

    2016-02-16

    The selection of the best column sets is one of the most tedious processes in comprehensive two-dimensional gas chromatography (GC × GC) where a multitude of choices of column sets could be employed for an individual sample analysis. We demonstrate analyte/stationary phase dependent selection approaches based on the linear solvation energy relationship (LSER), which is a reliable concept for the study of interaction mechanisms and retention prediction with a large database pool of columns and compounds. Good correlations between our predicted results, with experimental results reported in the literature, were obtained. The developed approaches were applied to the simulation of 157 920 individual experiments in GC × GC, focusing on the application of 30 nonionic liquid and 111 ionic liquid (IL) stationary phases for separation of some example sets of model compounds present in practical samples. The best column sets for each sample separation could then be extracted according to maximizing orthogonality, which estimates the quality of separation.

  3. Comprehensive two-dimensional gas chromatography for enhanced analysis of naphthas: new column combination involving permethylated cyclodextrin in the second dimension.

    Science.gov (United States)

    Adam, Frédérick; Vendeuvre, Colombe; Bertoncini, Fabrice; Thiébaut, Didier; Espinat, Didier; Hennion, Marie-Claire

    2008-01-18

    A new column association using comprehensive two-dimensional gas chromatography for the detailed molecular analysis of hydrocarbon mixtures is reported in this paper. In order to compare the impact of two different secondary columns, a novel column combination relying on a GC x 2GC system was used. This system is based on a non-polar first column (PONA) combined with both a permethylated beta-cyclodextrin (beta-Dex 120) stationary phase and a polysilphenylensiloxane (BPX 50) in the second dimension. Compared to BPX 50 stationary phase, the implementation of beta-cyclodextrin columns as the second dimension was found to improve the resolution between paraffins and naphthenes in the naphtha range but not in the middle distillate range. Attempts to improve the results and to understand the interaction mechanism remained unsuccessful. Therefore, the benefits of the beta-Dex 120-column are only demonstrated on heavy naphtha cut for the quantitation of hydrocarbons.

  4. Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry reveals the correlation between chemical compounds in Japanese sake and its organoleptic properties.

    Science.gov (United States)

    Takahashi, Kei; Kabashima, Fumie; Tsuchiya, Fumihiko

    2016-03-01

    Japanese sake is a traditional alcoholic beverage composed of a wide variety of metabolites, which give it many types of tastes and flavors. Previously, we have reported that medium-chain fatty acids contribute to a fatty odor in sake (Takahashi, K., et al., J. Agric. Food Chem., 62, 8478-8485, 2014). In this study, we have reanalyzed the data obtained using two-dimensional gas chromatography coupled with time-of-flight mass spectrometry. The relationship between the chemical components in sake and specific organoleptic properties such as off-flavor and quality has been explored. This led to the identification of the type of chemical compounds present and an assessment of the numerous candidate compounds that correlate with such organoleptic properties in sake. This research provides important fundamental knowledge for the sake-brewing industry. Copyright © 2015 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  5. Spin beam splitter based on Goos-Haenchen shifts in two-dimensional electron gas modulated by ferromagnetic and Schottky metal stripes

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Mao-Wang; Huang, Xin-Hong; Zhang, Gui-Lin; Chen, Sai-Yan [College of Science, Guilin University of Technology, Guilin 541004 (China)

    2012-11-15

    We present a theoretical study on the spin-dependent Goos-Haenchen (GH) effect in a two-dimensional electron gas modulated by ferromagnetic and Schottky metal (SM) stripes. The GH shifts for spin electron beams across this device are calculated with the help of the stationary phase method. It is shown that the GH shift of spin-up beam is significantly different from that of spin-down beam, i.e., this device shows up a considerable spin polarization effect in GH shifts of electron beams. It also is shown that both magnitude and sign of spin polarization of GH shifts are closely related to the stripe width, the magnetic strength and the gated voltage under SM stripe. These interesting properties not only provide an effective method of spin injection for spintronics application, but also give rise to a tunable spin beam splitter. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Detailed analysis of petroleum hydrocarbon attenuation in biopiles by high-performance liquid chromatography followed by comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    Mao, Debin; Lookman, Richard; Van De Weghe, Hendrik; Van Look, Dirk; Vanermen, Guido; De Brucker, Nicole; Diels, Ludo

    2009-02-27

    Enhanced bioremediation of petroleum hydrocarbons in two biopiles was quantified by high-performance liquid chromatography (HPLC) followed by comprehensive two-dimensional gas chromatography (GCXGC). The attenuation of 34 defined hydrocarbon classes was calculated by HPLC-GCXGC analysis of representative biopile samples at start-up and after 18 weeks of biopile operation. In general, a-cyclic alkanes were most efficiently removed from the biopiles, followed by monoaromatic hydrocarbons. Cycloalkanes and polycyclic aromatic hydrocarbons (PAHs) were more resistant to degradation. A-cyclic biomarkers farnesane, trimethyl-C13, norpristane, pristane and phytane dropped to only about 10% of their initial concentrations. On the other hand, C29-C31 hopane concentrations remained almost unaltered after 18 weeks of biopile operation, confirming their resistance to biodegradation. They are thus reliable indicators to estimate attenuation potential of petroleum hydrocarbons in biopile processed soils.

  7. Quantum transport in two dimensional electron gas/p-wave superconductor junction with Rashba spin–orbit coupling at the interface and in the normal layer

    Energy Technology Data Exchange (ETDEWEB)

    Mohammadkhani, R., E-mail: rmkhani@znu.ac.ir; Hassanloo, Gh.

    2014-11-01

    We have studied the tunneling conductance of a clean two dimensional electron gas/p- wave superconductor junction with Rashba spin–orbit coupling (RSOC) which is present in the normal layer and at the interface. Using the extended Blonder–Tinkham–Klapwijk formalism we have found that the subgap conductance peaks are shifted to a nonzero bias by RSOC at the interface which are the same as Ref. [1]. It is shown that for low insulating barrier and in the absence of the interface RSOC, the tunneling conductance decreases within energy gap with increasing of the RSOC in the normal layer while for high insulating barrier it enhances by increase of the RSOC. We have also shown that the RSOC inside the normal cannot affect the location of the subgap conductance peaks shifted by the interface RSOC.

  8. Analysis of Salvinorin A in plants, water, and urine using solid-phase microextraction-comprehensive two-dimensional gas chromatography-time of flight mass spectrometry.

    Science.gov (United States)

    Barnes, Brian B; Snow, Nicholas H

    2012-02-24

    Salvinorin A, a psychoactive hallucinogen, and related compounds, were analyzed in plants, water, and urine using liquid-liquid extraction (LLE), solid-phase microextraction (SPME) and comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-ToFMS). A semi-qualitative study of the extraction of Salvinorin A and analogs from Salvia divinorum plants by LLE showed ppb levels of Salvinorin A and several analogs in the leaves and stems of S. divinorum plants, much lower than expected. Quantitative analysis of Salvinorin A spiked into water and urine showed much better figures of merit for SPME than LLE, with limit of detection of about 5 ng/mL, linear range from 8 to 500 ng/mL and precision about ±10% for the SPME-based analyses using external standard quantitation. GC×GC-ToFMS was especially effective in separating the peaks of interest from matrix and chromatographic interferences.

  9. Transport properties of the two-dimensional electron gas in GaN/AlGaN heterostructures grown by ammonia molecular-beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Pogosov, A.G.; Budantsev, M.V.; Lavrov, R.A.; Mansurov, V.G.; Nikitin, A.Yu.; Preobrazhenskii, V.V.; Zhuravlev, K.S. [Institute of Semiconductor Physics, 13 Lavrentiev Avenue, 630090 Novosibirsk (Russian Federation)

    2006-07-15

    Transport properties of the two-dimensional electron gas in AlGaN/GaN heterostructures grown by ammonia molecular-beam epitaxy are experimentally investigated. Conventional Hall and Shubnikov-de Haas measurements as well as investigations of quantum transport phenomena are reported. It is found that negative magnetoresistance (NMR) caused by weak localization demonstrates an unusual behavior at low temperature (1.8 K). The observed NMR cannot be described by the ordinary theory of quantum corrections to conductivity based on a single phase breaking time {tau}{sub {phi}}. The anomalous NMR behavior can be explained by the presence of two occupied quantum subbands, characterized by their own phase breaking times {tau} {sub {phi}} {sub 1} and {tau} {sub {phi}} {sub 2}. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Donor-Like Surface Traps on Two-Dimensional Electron Gas and Current Collapse of AlGaN/GaN HEMTs

    Science.gov (United States)

    Yu, Chen-hui; Luo, Qing-zhou; Luo, Xiang-dong; Liu, Pei-sheng

    2013-01-01

    The effect of donor-like surface traps on two-dimensional electron gas (2DEG) and drain current collapse of AlGaN/GaN high electron mobility transistors (HEMTs) has been investigated in detail. The depletion of 2DEG by the donor-like surface states is shown. The drain current collapse is found to be more sensitive to the addition of positive surface charges. Surface trap states with higher energy levels result in weaker current collapse and faster collapse process. By adopting an optimized backside doping scheme, the electron density of 2DEG has been improved greatly and the current collapse has been greatly eliminated. These results give reference to the improvement in device performance of AlGaN/GaN HEMTs. PMID:24348195

  11. Two-dimensional electron gas generated by La-doping at SrTiO3(001 surface: A first-principles study

    Directory of Open Access Journals (Sweden)

    Yun Li

    2013-06-01

    Full Text Available We carried out first-principles calculations to study the electronic properties of SrO-terminated and TiO2-terminated SrTiO3(001 surfaces with La-doping at the surface. We find that an intrinsic lower-lying state at the SrO-terminated surface can accommodate a two-dimensional electron gas (2DEG. By introducing La-doping at the SrO-terminated surface the energy position of the surface state and the 2DEG density can be tuned by changing the doping concentration. The higher the La-doping concentration, the lower the lower-lying state and the higher the 2DEG density. This 2DEG has a small effective mass and hopefully shows a high mobility.

  12. Patterning the two dimensional electron gas at the LaAlO3/SrTiO3 interface by structured Al capping

    Science.gov (United States)

    Zhou, Y.; Wang, P.; Luan, Z. Z.; Shi, Y. J.; Jiang, S. W.; Ding, H. F.; Wu, D.

    2017-04-01

    We demonstrate an approach for patterning a quasi-two dimensional electron gas (q-2DEG) at the interface of LaAlO3 (LAO) and SrTiO3 (STO) utilizing a structured Al capping layer. The capping of Al enables the formation of q-2DEG at the interface of 1-3 unit cells (uc) of LAO on STO, which was originally insulating before capping. The properties of the q-2DEG induced by the Al capping layer are essentially the same as those of q-2DEG without Al. Therefore, we can pattern q-2DEG by simply patterning the Al film on LAO (2 or 3 uc)/STO using a one-step liftoff process. Our approach circumvents the difficulty of direct patterning of oxide materials and provides a simple and robust patterning method for future device applications based on complex oxide interfaces.

  13. Predictive Control over Charge Density in the Two-Dimensional Electron Gas at the Polar-Nonpolar NdTiO3/SrTiO3 Interface

    Science.gov (United States)

    Xu, Peng; Ayino, Yilikal; Cheng, Christopher; Pribiag, Vlad S.; Comes, Ryan B.; Sushko, Peter V.; Chambers, Scott A.; Jalan, Bharat

    2016-09-01

    Through systematic control of the Nd concentration, we show that the carrier density of the two-dimensional electron gas (2DEG) in SrTiO3/NdTiO3/SrTiO3(001 ) can be modulated over a wide range. We also demonstrate that the NdTiO3 in heterojunctions without a SrTiO3 cap is degraded by oxygen absorption from air, resulting in the immobilization of donor electrons that could otherwise contribute to the 2DEG. This system is, thus, an ideal model to understand and control the insulator-to-metal transition in a 2DEG based on both environmental conditions and film-growth processing parameters.

  14. Photoluminescence Investigation of Two-Dimensional Electron Gas in an Undoped AlxGa1-xN/GaN Heterostructure

    Institute of Scientific and Technical Information of China (English)

    HAN Xiu-Xun; WU Jie-Jun; LI Jie-Min; CONG Guang-Wei; LIU Xiang-Lin; ZHU Qin-Sheng; WANG Zhan-Guo

    2005-01-01

    @@ Low-temperature photoluminescence measurement is performed on an undoped Alx Ga1-xN/GaN heterostructure. Temperature-dependent Hall mobility confirms the formation of two-dimensional electron gas (2DEG) near the heterointerface. A weak photoluminescence (PL) peak with the energy of ~79meV lower than the free exciton (FE) emission of bulk GaN is related to the radiative recombination between electrons confined in the triangular well and the holes near the flat-band region of GaN. Its identification is supported by the solution of coupled one-dimensional Poisson and Schrodinger equations. When the temperature increases, the red shift of the 2DEG related emission peak is slower than that of the FE peak. The enhanced screening effect coming from the increasing 2DEG concentration and the varying electron distribution at two lowest subbands as a function of temperature account for such behaviour.

  15. Subband Structure of a Two-Dimensional Electron Gas Formed at the Polar Surface of the Strong Spin-Orbit Perovskite KTaO3

    Energy Technology Data Exchange (ETDEWEB)

    King, P.D.C.

    2012-03-01

    We demonstrate the formation of a two-dimensional electron gas (2DEG) at the (100) surface of the 5d transition-metal oxide KTaO{sub 3}. From angle-resolved photoemission, we find that quantum confinement lifts the orbital degeneracy of the bulk band structure and leads to a 2DEG composed of ladders of subband states of both light and heavy carriers. Despite the strong spin-orbit coupling, we find no experimental signatures of a Rashba spin splitting, which has important implications for the interpretation of transport measurements in both KTaO{sub 3}- and SrTiO{sub 3}-based 2DEGs. The polar nature of the KTaO{sub 3}(100) surface appears to help mediate formation of the 2DEG as compared to non-polar SrTiO{sub 3}(100).

  16. Two-Dimensional MHD Numerical Simulations of Magnetic Reconnection Triggered by A Supernova Shock in Interstellar Medium, Generation of X-Ray Gas in Galaxy

    CERN Document Server

    Tanuma, S; Kudoh, T; Shibata, K; Tanuma, Syuniti; Yokoyama, Takaaki; Kudoh, Takahiro; Shibata, Kazunari

    2001-01-01

    We examine the magnetic reconnection triggered by a supernova (or a point explosion) in interstellar medium, by performing two-dimensional resistive magnetohydrodynamic (MHD) numerical simulations with high spatial resolution. We found that the magnetic reconnection starts long after a supernova shock (fast-mode MHD shock) passes a current sheet. The current sheet evolves as follows: (i) Tearing-mode instability is excited by the supernova shock, and the current sheet becomes thin in its nonlinear stage. (ii) The current-sheet thinning is saturated when the current-sheet thickness becomes comparable to that of Sweet-Parker current sheet. After that, Sweet-Parker type reconnection starts, and the current-sheet length increases. (iii) ``Secondary tearing-mode instability'' occurs in the thin Sweet-Parker current sheet. (iv) As a result, further current-sheet thinning occurs and anomalous resistivity sets in, because gas density decreases in the current sheet. Petschek type reconnection starts and heats interste...

  17. Quantitative analysis of biodiesel in blends of biodiesel and conventional diesel by comprehensive two-dimensional gas chromatography and multivariate curve resolution.

    Science.gov (United States)

    Mogollon, Noroska Gabriela Salazar; Ribeiro, Fabiana Alves de Lima; Lopez, Monica Mamian; Hantao, Leandro Wang; Poppi, Ronei Jesus; Augusto, Fabio

    2013-09-24

    In this paper, a method to determine the composition of blends of biodiesel with mineral diesel (BXX) by multivariate curve resolution with Alternating Least Squares (MRC-ALS) combined to comprehensive two-dimensional gas chromatography with Flame Ionization Detection (GC×GC-FID) is presented. Chromatographic profiles of BXX blends produced with biodiesels from different sources were used as input data. An initial evaluation carried out after multiway principal component analysis (MPCA) was used to reveal regions of the chromatograms were the signal was likely to be dependent on the concentration of biodiesel, regardless its vegetable source. After this preliminary step MCR-ALS modeling was carried out only using relevant parts of the chromatograms. The resulting procedure was able to predict accurately the concentration of biodiesel in the BXX samples regardless of its origin.

  18. Comprehensive two-dimensional gas chromatography - time-of-flight mass spectrometry and simultaneous electron capture detection/nitrogen phosphorous detection for incense analysis

    Science.gov (United States)

    Tran, Tin C.; Marriott, Philip J.

    This study reports comprehensive two-dimensional gas chromatography hyphenated to time-of-flight mass spectrometry detection (GC × GC/TOFMS) for characterisation and identification of components generated by four different types of powdered incense headspace (H/S) and incense smoke. GC × GC/TOFMS allowed simultaneous separation and identification of compounds emitted into the atmosphere as a result of combustion of incense powder. The smoke stream comprised compounds originating from the incense powder, and combustion products such as saturated and unsaturated hydrocarbons, essential oil type compounds, nitromusks, fatty acid methyl esters (FAMEs), polycyclic aromatic hydrocarbons (PAHs, which possibly include oxygenated and nitrated PAH), N-heterocyclics, pyrans and furans, which were detected and tentatively identified by GC × GC/TOFMS. GC × GC-electron capture detector/nitrogen phosphorous detector (ECD/NPD) potentially offers the prospect of providing selective chemical compositional information of incense powder and smoke, such as nitrogen-containing (N-containing) and halogenated compounds. Results of GC×GC-ECD/NPD showed that both incense powder and smoke generated emission of N-containing and halogenated compounds. A significant number of halogenated and N-containing compounds were emitted during the incomplete combustion of incense. However, one further objective of this paper is to demonstrate the capacity of comprehensive two-dimensional gas chromatography coupled to specific and/or selective detectors such as those used in this study (GC × GC-ECD/NPD) for the detection of particular classes of compounds such as N-containing and halogenated compounds at trace level concentrations in complex smoke samples.

  19. Application of a quantitative structure retention relationship approach for the prediction of the two-dimensional gas chromatography retention times of polycyclic aromatic sulfur heterocycle compounds.

    Science.gov (United States)

    Gieleciak, Rafal; Hager, Darcy; Heshka, Nicole E

    2016-03-11

    Information on the sulfur classes present in petroleum is a key factor in determining the value of refined products and processing behavior in the refinery. A large part of the sulfur present is included in polycyclic aromatic sulfur heterocycles (PASHs), which in turn are difficult to desulfurize. Furthermore, some PASHs are potentially more mutagenic and carcinogenic than polycyclic aromatic hydrocarbons, PAHs. All of this calls for improved methods for the identification and quantification of individual sulfur species. Recent advances in analytical techniques such as comprehensive two-dimensional gas chromatography (GC×GC) have enabled the identification of many individual sulfur species. However, full identification of individual components, particularly in virgin oil fractions, is still out of reach as standards for numerous compounds are unavailable. In this work, a method for accurately predicting retention times in GC×GC using a QSRR (quantitative structure retention relationship) method was very helpful for the identification of individual sulfur compounds. Retention times for 89 saturated, aromatic, and polyaromatic sulfur-containing heterocyclic compounds were determined using two-dimensional gas chromatography. These retention data were correlated with molecular descriptors generated with CODESSA software. Two independent QSRR relationships were derived for the primary as well as the secondary retention characteristics. The predictive ability of the relationships was tested by using both independent sets of compounds and a cross-validation technique. When the corresponding chemical standards are unavailable, the equations developed for predicting retention times can be used to identify unknown chromatographic peaks by matching their retention times with those of sulfur compounds of known molecular structure.

  20. Two-dimensional radiation MHD modeling assessment of designs for argon gas puff distributions for future experiments on the refurbished Z machine

    Science.gov (United States)

    Thornhill, J. W.; Giuliani, J. L.; Chong, Y. K.; Velikovich, A. L.; Dasgupta, A.; Apruzese, J. P.; Jones, B.; Ampleford, D. J.; Coverdale, C. A.; Jennings, C. A.; Waisman, E. M.; Lamppa, D. C.; McKenney, J. L.; Cuneo, M. E.; Krishnan, M.; Coleman, P. L.; Madden, R. E.; Elliott, K. W.

    2012-09-01

    Argon Z-pinch experiments are to be performed on the refurbished Z machine (which we will refer to as ZR here in order to distinguish between pre-refurbishment Z) at Sandia National Laboratories with a new 8 cm diameter double-annulus gas puff nozzle constructed by Alameda Applied Sciences Corporation (AASC). The gas exits the nozzle from an outer and inner annulus and a central jet. The amount of gas present in each region can be varied. Here a two-dimensional radiation MHD (2DRMHD) model, MACH2-TCRE, with tabular collisional radiative equilibrium atomic kinetics is used to theoretically investigate stability and K-shell emission properties of several measured (interferometry) initial gas distributions emanating from this new nozzle. Of particular interest is to facilitate that the distributions employed in future experiments have stability and K-shell emission properties that are at least as good as the Titan nozzle generated distribution that was successfully fielded in earlier experiments on the Z machine before it underwent refurbishment. The model incorporates a self-consistent calculation for non-local thermodynamic equilibrium kinetics and ray-trace based radiation transport. This level of detail is necessary in order to model opacity effects, non-local radiation effects, and the high temperature state of K-shell emitting Z-pinch loads. Comparisons of radiation properties and stability of measured AASC gas profiles are made with that of the distribution used in the pre-refurbished Z experiments. Based on these comparisons, an optimal K-shell emission producing initial gas distribution is determined from among the AASC nozzle measured distributions and predictions are made for K-shell yields attainable from future ZR experiments.

  1. Two-Dimensional Numerical Simulations of Ultrasound in Liquids with Gas Bubble Agglomerates: Examples of Bubbly-Liquid-Type Acoustic Metamaterials (BLAMMs).

    Science.gov (United States)

    Vanhille, Christian

    2017-01-17

    This work deals with a theoretical analysis about the possibility of using linear and nonlinear acoustic properties to modify ultrasound by adding gas bubbles of determined sizes in a liquid. We use a two-dimensional numerical model to evaluate the effect that one and several monodisperse bubble populations confined in restricted areas of a liquid have on ultrasound by calculating their nonlinear interaction. The filtering of an input ultrasonic pulse performed by a net of bubbly-liquid cells is analyzed. The generation of a low-frequency component from a single cell impinged by a two-frequency harmonic wave is also studied. These effects rely on the particular dispersive character of attenuation and nonlinearity of such bubbly fluids, which can be extremely high near bubble resonance. They allow us to observe how gas bubbles can change acoustic signals. Variations of the bubbly medium parameters induce alterations of the effects undergone by ultrasound. Results suggest that acoustic signals can be manipulated by bubbles. This capacity to achieve the modification and control of sound with oscillating gas bubbles introduces the concept of bubbly-liquid-based acoustic metamaterials (BLAMMs).

  2. Fermi-to-Bose crossover in a trapped quasi-2D gas of fermionic atoms

    Science.gov (United States)

    Turlapov, A. V.; Kagan, M. Yu

    2017-09-01

    The physics of many-body systems where particles are restricted to move in two spatial dimensions is challenging and even controversial: on one hand, neither long-range order nor Bose condensation may appear in infinite uniform 2D systems at finite temperature, on the other hand this does not prohibit superfluidity or superconductivity. Moreover, 2D superconductors, such as cuprates, are among the systems with the highest critical temperatures. Ultracold atoms are a platform for studying 2D physics. Unique from other physical systems, quantum statistics may be completely changed in an ultracold gas: an atomic Fermi gas may be smoothly crossed over into a gas of Bose molecules (or dimers) by tuning interatomic interactions. We review recent experiments where such crossover has been demonstrated, as well as critical phenomena in the Fermi-to-Bose crossover. We also present simple theoretical models describing the gas at different points of the crossover and compare the data to these and more advanced models.

  3. Binding energy of two-dimensional biexcitons

    DEFF Research Database (Denmark)

    Singh, Jai; Birkedal, Dan; Vadim, Lyssenko;

    1996-01-01

    Using a model structure for a two-dimensional (2D) biexciton confined in a quantum well, it is shown that the form of the Hamiltonian of the 2D biexciton reduces into that of an exciton. The binding energies and Bohr radii of a 2D biexciton in its various internal energy states are derived...... analytically using the fractional dimension approach. The ratio of the binding energy of a 2D biexciton to that of a 2D exciton is found to be 0.228, which agrees very well with the recent experimental value. The results of our approach are compared with those of earlier theories....

  4. Two-dimensional electron gas at surfaces of (001), (110), and (111) oriented SrTiO3 induced by Ar+-irradiation

    Science.gov (United States)

    Miao, Ludi; Du, Renzhong; Yin, Yuewei; Li, Qi

    2015-03-01

    Two-dimensional electron gases (2DEGs) at transition metal oxide surfaces and interfaces have attracted much attention due to their fascinating exotic properties such as superconductivity, large magneto-resistance (MR), and ferromagnetism. We have created 2DEGs at the surfaces of (001), (110), and (111) oriented SrTiO3 (STO) by Ar+-irradiation and measured their transport properties. The 2DEGs exhibit a fully metallic behavior with the 2D charge carrier density around 2 ×1014 cm-2 and the mobility as large as 5500 cm2V-1s-1 at low temperatures, which is tunable by electric fields applied through STO back gates. We have measured MR anisotropy of the 2DEGs at surfaces of STO with all orientations. We observed combinations of two types of components in their anisotropic MR at low temperatures. While the first type is an STO-orientation-independent two-fold component results from the Lorentz force effect, the second type shows stark differences between these 2DEGs as a consequence of distinct Fermi surface symmetries with different STO orientations. Indeed, it is four-fold for STO (001), two-fold for STO (110) and six-fold for STO (111), respectively.

  5. Magneto-thermoelectric effects in the two-dimensional electron gas of a HgTe quantum well due to THz laser heating by cyclotron resonance absorption

    Science.gov (United States)

    Pakmehr, Mehdi; Bruene, Christoph; Buhmann, Hartmut; Molenkamp, Laurens; McCombe, Bruce

    2015-03-01

    HgTe quantum wells (QWs) have shown a number of interesting phenomena over the past 20 years, most recently the first two-dimensional topological insulating state. We have studied thermoelectric photovoltages of 2D electrons in a 6.1 nm wide HgTe quantum well induced by cyclotron resonance absorption (B = 2 - 5 T) of a focused THz laser beam. We have estimated thermo-power coefficients by detailed analysis of the beam profile at the sample surface and the photovoltage signals developed across various contacts of a large Hall bar structure at a bath temperature of 1.6 K. We obtain reasonable values of the magneto-thermopower coefficients. Work at UB was supported by NSF DMR 1008138 and the Office of the Provost, and at the University of Wuerzburg by DARPA MESO Contract N6601-11-1-4105, by DFG Grant HA5893/4-1 within SPP 1666 and the Leibnitz Program, and the EU ERC-AG Program (Project 3-TOP.

  6. 2D hydrodynamic simulations of a variable length gas target for density down-ramp injection of electrons into a laser wakefield accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Kononenko, O., E-mail: olena.kononenko@desy.de [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany); Lopes, N.C.; Cole, J.M.; Kamperidis, C.; Mangles, S.P.D.; Najmudin, Z. [The John Adams Institute for Accelerator Science, The Blackett Laboratory, Imperial College London, SW7 2BZ UK (United Kingdom); Osterhoff, J. [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany); Poder, K. [The John Adams Institute for Accelerator Science, The Blackett Laboratory, Imperial College London, SW7 2BZ UK (United Kingdom); Rusby, D.; Symes, D.R. [Central Laser Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX (United Kingdom); Warwick, J. [Queens University Belfast, North Ireland (United Kingdom); Wood, J.C. [The John Adams Institute for Accelerator Science, The Blackett Laboratory, Imperial College London, SW7 2BZ UK (United Kingdom); Palmer, C.A.J. [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany)

    2016-09-01

    In this work, two-dimensional (2D) hydrodynamic simulations of a variable length gas cell were performed using the open source fluid code OpenFOAM. The gas cell was designed to study controlled injection of electrons into a laser-driven wakefield at the Astra Gemini laser facility. The target consists of two compartments: an accelerator and an injector section connected via an aperture. A sharp transition between the peak and plateau density regions in the injector and accelerator compartments, respectively, was observed in simulations with various inlet pressures. The fluid simulations indicate that the length of the down-ramp connecting the sections depends on the aperture diameter, as does the density drop outside the entrance and the exit cones. Further studies showed, that increasing the inlet pressure leads to turbulence and strong fluctuations in density along the axial profile during target filling, and consequently, is expected to negatively impact the accelerator stability.

  7. Superconductivity in the two-dimensional electron gas induced by high-energy optical phonon mode and large polarization of the SrTiO3 substrate

    Science.gov (United States)

    Rosenstein, Baruch; Shapiro, B. Ya.; Shapiro, I.; Li, Dingping

    2016-07-01

    Pairing in one-atomic-layer-thick two-dimensional electron gas (2DEG) by a single flat band of high-energy longitudinal optical phonons is considered. The polar dielectric SrTiO3 (STO) exhibits such an energetic phonon mode and the 2DEG is created both when one unit cell FeSe layer is grown on its (100 ) surface and on the interface with another dielectric like LaAlO3 (LAO). We obtain a quantitative description of both systems solving the gap equation for Tc for arbitrary Fermi energy ɛF, electron-phonon coupling λ , and the phonon frequency Ω , and direct (random-phase approximation) electron-electron repulsion strength α . The focus is on the intermediate region between the adiabatic, ɛF>>Ω , and the nonadiabatic, ɛF<<Ω , regimes. The high-temperature superconductivity in single-unit-cell FeSe/STO is possible due to a combination of three factors: high-longitudinal-optical phonon frequency, large electron-phonon coupling λ ˜0.5 , and huge dielectric constant of the substrate suppression the Coulomb repulsion. It is shown that very low density electron gas in the interfaces is still capable of generating superconductivity of the order of 0.1 K in LAO/STO.

  8. Using comprehensive two-dimensional gas chromatography for the analysis of oxygenates in middle distillates I. Determination of the nature of biodiesels blend in diesel fuel.

    Science.gov (United States)

    Adam, Frédérick; Bertoncini, Fabrice; Coupard, Vincent; Charon, Nadège; Thiébaut, Didier; Espinat, Didier; Hennion, Marie-Claire

    2008-04-04

    In the current energetic context (increasing consumption of vehicle fuels, greenhouse gas emission etc.) government policies lead to mandatory introduction in fossil fuels of fuels resulting from renewable sources of energy such as biomass. Blending of fatty acid alkyl esters from vegetable oils (also known as biodiesel) with conventional diesel fuel is one of the solutions technologically available; B5 blends (up to 5%w/w esters in fossil fuel) are marketed over Europe. Therefore, for quality control as well as for forensic reasons, it is of major importance to monitor the biodiesel origin (i.e. the fatty acid ester distribution) and its content when it is blend with petroleum diesel. This paper reports a comprehensive two-dimensional gas chromatography (GC x GC) method that was developed for the individual quantitation of fatty acid esters in middle distillates matrices. Several first and the second dimension columns have been investigated and their performances to achieve (i) a group type separation of hydrocarbons and (ii) individual identification and quantitation of fatty acid ester blend with diesel are reported and discussed. Finally, comparison of quantitative GC x GC results with reference methods demonstrates the benefits of GC x GC approach which enables fast and reliable individual quantitation of fatty acid esters in one single run. Results show that under developed chromatographic conditions, quantitative group type analysis of hydrocarbons is also possible, meaning that simultaneous quantification of hydrocarbons and fatty acid esters can be achieved in one single run.

  9. A one-step method for priority compounds of concern in tar from former industrial sites: trimethylsilyl derivatisation with comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    Gauchotte-Lindsay, C; Richards, P; McGregor, L A; Thomas, R; Kalin, R M

    2012-08-31

    A dense non-aqueous phase liquid sample formed by release of coal tar into the environment was derivatised by trimethylsilylation using the reagent N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and extracted in hexane using accelerated solvent extraction. This procedure enables comprehensive extraction of an extensive suite of organic compounds from tar, which has not previously been described. Comprehensive two dimensional gas chromatography coupled to time of flight mass spectrometry (GC×GC-TOFMS) was used for the analysis of the sample for concurrent evaluation of -OH functional group-containing compounds along with aliphatics, polycyclic aromatic hydrocarbons and other typical tar compounds normally determined via classic gas chromatography. Using statistically designed experiments, a range of conditions were tested for complete recovery of four different surrogates. The robustness and repeatability of the optimised derivatisation/extraction method was demonstrated. Finally, more than a hundred and fifty derivatised compounds were identified using mass spectra elucidation and GC×GC logical order of elution. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. Evolution of Matter Wave Interference of Bose-Condensed Gas in a 2D Optical Lattice

    Institute of Scientific and Technical Information of China (English)

    XUZhi-Jun; LINGuo-Cheng; XUJun; LIZhen

    2005-01-01

    We investigate the average particle-number distribution of the atoms in the combined potential of 2D optical lattices and 31) harmonic magnetic trap based on the Gross-Pitaevskii equation. After the combined potential is switched of[, and only the optical lattice is switched off, we give the analytical results of the wavefunction of the Bosecondensed gas at any time t by using a propagator method. For both disk-shaped and cigar-shaped Bose-condensed gas,we discuss the evolution process of the central and side peaks of the interference pattern.

  11. Characterization of sulfur and nitrogen compounds in Brazilian petroleum derivatives using ionic liquid capillary columns in comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometric detection.

    Science.gov (United States)

    Cappelli Fontanive, Fernando; Souza-Silva, Érica Aparecida; Macedo da Silva, Juliana; Bastos Caramão, Elina; Alcaraz Zini, Claudia

    2016-08-26

    Diesel and naphtha samples were analyzed using ionic liquid (IL) columns to evaluate the best column set for the investigation of organic sulfur compounds (OSC) and nitrogen(N)-containing compounds analyses with comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry detector (GC×GC/TOFMS). Employing a series of stationary phase sets, namely DB-5MS/DB-17, DB-17/DB-5MS, DB-5MS/IL-59, and IL-59/DB-5MS, the following parameters were systematically evaluated: number of tentatively identified OSC, 2D chromatographic space occupation, number of polyaromatic hydrocarbons (PAH) and OSC co-elutions, and percentage of asymmetric peaks. DB-5MS/IL-59 was chosen for OSC analysis, while IL59/DB-5MS was chosen for nitrogen compounds, as each stationary phase set provided the best chromatographic efficiency for these two classes of compounds, respectively. Most compounds were tentatively identified by Lee and Van den Dool and Kratz retention indexes, and spectra-matching to library. Whenever available, compounds were also positively identified via injection of authentic standards.

  12. Identification of organic sulfur compounds in coal bitumen obtained by different extraction techniques using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometric detection.

    Science.gov (United States)

    Machado, Maria Elisabete; Fontanive, Fernando Cappelli; de Oliveira, José Vladimir; Caramão, Elina Bastos; Zini, Cláudia Alcaraz

    2011-11-01

    The determination of organic sulfur compounds (OSC) in coal is of great interest. Technically and operationally these compounds are not easily removed and promote corrosion of equipment. Environmentally, the burning of sulfur compounds leads to the emission of SO(x) gases, which are major contributors to acid rain. Health-wise, it is well known that these compounds have mutagenic and carcinogenic properties. Bitumen can be extracted from coal by different techniques, and use of gas chromatography coupled to mass spectrometric detection enables identification of compounds present in coal extracts. The OSC from three different bitumens were tentatively identified by use of three different extraction techniques: accelerated solvent extraction (ASE), ultrasonic extraction (UE), and supercritical-fluid extraction (SFE). Results obtained from one-dimensional gas chromatography (1D GC) coupled to quadrupole mass spectrometric detection (GC-qMS) and from two-dimensional gas chromatography with time-of-flight mass spectrometric detection (GC × GC-TOFMS) were compared. By use of 2D GC, a greater number of OSC were found in ASE bitumen than in SFE and UE bitumens. No OSC were identified with 1D GC-qMS, although some benzothiophenes and dibenzothiophenes were detected by use of EIM and SIM modes. GC × GC-TOFMS applied to investigation of OSC in bitumens resulted in analytical improvement, as more OSC classes and compounds were identified (thiols, sulfides, thiophenes, naphthothiophenes, benzothiophenes, and benzonaphthothiophenes). The roof-tile effect was observed for OSC and PAH in all bitumens. Several co-elutions among analytes and with matrix interferents were solved by use of GC × GC.

  13. Local Probing of Phase Coherence in a Strongly Interacting 2D Quantum Gas

    Science.gov (United States)

    Luick, Niclas; Siegl, Jonas; Hueck, Klaus; Morgener, Kai; Lompe, Thomas; Weimer, Wolf; Moritz, Henning

    2016-05-01

    The dimensionality of a quantum system has a profound impact on its coherence and superfluid properties. In 3D superfluids, bosonic atoms or Cooper pairs condense into a macroscopic wave function exhibiting long-range phase coherence. Meanwhile, 2D superfluids show a strikingly different behavior: True long-range coherence is precluded by thermal fluctuations, nevertheless Berezinskii-Kosterlitz-Thouless (BKT) theory predicts that 2D systems can still become superfluid. The superfluid state is characterized by an algebraic decay of phase correlations g1(r) ~r - τ / 4 , where the decay exponent τ is directly related to the superfluid density ns according to τ = 4 /(nsλdB2) . I will present local coherence measurements in a strongly interacting 2D gas of diatomic 6 Li molecules. A self-interference technique allows us to locally extract the algebraic decay exponent and to reconstruct the superfluid density. We determine the scaling of the decay exponent with phase space density to provide a benchmark for studies of 2D superfluids in the strongly interacting regime.

  14. Two-dimensional photonic crystal surfactant detection.

    Science.gov (United States)

    Zhang, Jian-Tao; Smith, Natasha; Asher, Sanford A

    2012-08-07

    We developed a novel two-dimensional (2-D) crystalline colloidal array photonic crystal sensing material for the visual detection of amphiphilic molecules in water. A close-packed polystyrene 2-D array monolayer was embedded in a poly(N-isopropylacrylamide) (PNIPAAm)-based hydrogel film. These 2-D photonic crystals placed on a mirror show intense diffraction that enables them to be used for visual determination of analytes. Binding of surfactant molecules attaches ions to the sensor that swells the PNIPAAm-based hydrogel. The resulting increase in particle spacing red shifts the 2-D diffracted light. Incorporation of more hydrophobic monomers increases the sensitivity to surfactants.

  15. Gas-Sensing Devices Based on Zn-Doped NiO Two-Dimensional Grainy Films with Fast Response and Recovery for Ammonia Molecule Detection.

    Science.gov (United States)

    Wang, Jian; Wei, Xiaowei; Wangyang, Peihua

    2015-12-01

    Zn-doped NiO two-dimensional grainy films on glass substrates are shown to be an ammonia-sensing material with excellent comprehensive performance, which could real-time detect and monitor ammonia (NH3) in the surrounding environment. The morphology and structure analysis indicated that the as-fabricated semiconductor films were composed of particles with diameters ranging from 80 to 160 nm, and each particle was composed of small crystalline grain with a narrow size about 20 nm, which was the face-centered cubic single crystal structure. X-ray diffraction peaks shifted toward lower angle, and the size of the lattice increased compared with undoped NiO, which demonstrated that zinc ions have been successfully doped into the NiO host structure. Simultaneously, we systematically investigated the gas-sensing properties of the Zn-doped NiO sensors for NH3 detection at room temperature. The sensor based on doped NiO sensing films gave four to nine times faster response and four to six times faster recovery speeds than those of sensor with undoped NiO films, which is important for the NiO sensor practical applications. Moreover, we found that the doped NiO sensors owned outstanding selectivity toward ammonia.

  16. A Vacuum Ultraviolet Absorption Array Spectrometer as a Selective Detector for Comprehensive Two-Dimensional Gas Chromatography: Concept and First Results.

    Science.gov (United States)

    Gröger, Thomas; Gruber, Beate; Harrison, Dale; Saraji-Bozorgzad, Mohammad; Mthembu, Makhosazana; Sutherland, Aimée; Zimmermann, Ralf

    2016-03-15

    Fast and selective detectors are very interesting for comprehensive two-dimensional gas chromatography (GC × GC). This is particularly true if the detector system can provide additional spectroscopic information on the compound structure and/or functionality. Other than mass spectrometry (MS), only optical spectroscopic detectors are able to provide selective spectral information. However, until present the application of optical spectroscopy technologies as universal detectors for GC × GC has been restricted mainly due to physical limitations such as insufficient acquisition speed or high detection limits. A recently developed simultaneous-detection spectrometer working in the vacuum ultraviolet (VUV) region of 125-240 nm overcomes these limitations and meets all the criteria of a universal detector for GC × GC. Peak shape and chromatographic resolution is preserved and unique spectral information, complementary to mass spectrometry data, is gained. The power of this detector is quickly recognized as it has the ability to discriminate between isomeric compounds or difficult to separate structurally related isobaric species; thus, it provides additional selectivity. A further promising feature of this detector is the data analysis concept of spectral filtering, which is accomplished by targeting special electronic transitions that allows for a fast screening of GC × GC chromatograms for designated compound classes.

  17. Quantitative and qualitative analysis of hemicellulose, cellulose and lignin bio-oils by comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry.

    Science.gov (United States)

    Michailof, Chrysoula; Sfetsas, Themistoklis; Stefanidis, Stylianos; Kalogiannis, Konstantinos; Theodoridis, Georgios; Lappas, Angelos

    2014-11-21

    Thermal and catalytic pyrolysis are efficient processes for the transformation of biomass to bio-oil, a liquid energy carrier and a general source of chemicals. The elucidation of the bio-oil's composition is essential for a rational design of both its production and utilization process. However, the complex composition of bio-oils hinders their complete qualitative and quantitative analysis, and conventional chromatographic techniques lack the necessary separation power. Two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-ToFMS) is considered a suitable technique for bio-oil analysis due to its increased separation and resolution capacity. This work presents the tentative qualitative and quantitative analysis of bio-oils resulting from the thermal and catalytic pyrolysis of standard xylan, cellulose, lignin and their mixture by GC×GC-ToFMS. Emphasis is placed on the development of the quantitative method using phenol-d6 as internal standard. During the method development, a standard solution of 39 compounds was used for the determination of the respective Relative Response Factors (RRF) employing statistical methods, ANOVA and WLSLR, for verification of the data. The developed method was applied to the above mentioned bio-oils and their detailed analysis is presented. The different compounds produced and their diverse concentration allows for an elucidation of the pyrolysis mechanism and highlight the effect of the catalyst.

  18. Analysis of alkyl phosphates in petroleum samples by comprehensive two-dimensional gas chromatography with nitrogen phosphorus detection and post-column Deans switching.

    Science.gov (United States)

    Nizio, Katie D; Harynuk, James J

    2012-08-24

    Alkyl phosphate based gellants used as viscosity builders for fracturing fluids used in the process of hydraulic fracturing have been implicated in numerous refinery-fouling incidents in North America. In response, industry developed an inductively coupled plasma optical emission spectroscopy (ICP-OES) based method for the analysis of total volatile phosphorus in distillate fractions of crude oil; however, this method is plagued by poor precision and a high limit of detection (0.5±1μg phosphorus mL(-1)). Furthermore this method cannot provide speciation information, which is critical for developing an understanding of the challenge of alkyl phosphates at a molecular level. An approach using comprehensive two-dimensional gas chromatography with nitrogen phosphorus detection (GC×GC-NPD) and post-column Deans switching is presented. This method provides qualitative and quantitative profiles of alkyl phosphates in industrial petroleum samples with increased precision and at levels comparable to or below those achievable by ICP-OES. A recovery study in a fracturing fluid sample and a profiling study of alkyl phosphates in four recovered fracturing fluid/crude oil mixtures (flowback) are also presented.

  19. In-plane anisotropy in two-dimensional electron gas at LaAlO3/SrTiO3(110) interface

    Science.gov (United States)

    Sheng-Chun, Shen; Yan-Peng, Hong; Cheng-Jian, Li; Hong-Xia, Xue; Xin-Xin, Wang; Jia-Cai, Nie

    2016-07-01

    A systematic study of the two-dimensional electron gas at LaAlO3/SrTiO3(110) interface reveals an anisotropy along two specific directions, [001] and . The anisotropy becomes distinct for the interface prepared under high oxygen pressure with low carrier density. Angular dependence of magnetoresistance shows that the electron confinement is stronger along the direction. Gate-tunable magnetoresistance reveals a clear in-plane anisotropy of the spin-orbit coupling, and the spin relaxation mechanism along both directions belongs to D’yakonov-Perel’ (DP) scenario. Moreover, in-plane anisotropic superconductivity is observed for the sample with high carrier density, the superconducting transition temperature is lower but the upper critical field is higher along the direction. This in-plane anisotropy could be ascribed to the anisotropic band structure along the two crystallographic directions. Project supported by the Ministry of Science and Technology of China (Grant Nos. 2013CB921701, 2013CBA01603, and 2014CB920903), the National Natural Science Foundation of China (Grant Nos. 10974019, 51172029, 91121012, 11422430, 11374035, 11474022, and 11474024), the Program for New Century Excellent Talents in the University of the Ministry of Education of China (Grant No. NCET-13-0054), and the Beijing Higher Education Young Elite Teacher Project, China (Grant No. YETP0238).

  20. Identifying important structural features of ionic liquid stationary phases for the selective separation of nonpolar analytes by comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    Zhang, Cheng; Ingram, Isaiah C; Hantao, Leandro W; Anderson, Jared L

    2015-03-20

    A series of dicationic ionic liquid (IL)-based stationary phases were evaluated as secondary columns in comprehensive two-dimensional gas chromatography (GC×GC) for the separation of aliphatic hydrocarbons from kerosene. In order to understand the role that structural features of ILs play on the selectivity of nonpolar analytes, the solvation parameter model was used to probe the solvation properties of the IL-based stationary phases. It was observed that room temperature ILs containing long free alkyl side chain substituents and long linker chains between the two cations possess less cohesive forces and exhibited the highest resolution of aliphatic hydrocarbons. The anion component of the IL did not contribute significantly to the overall separation, as similar selectivities toward aliphatic hydrocarbons were observed when examining ILs with identical cations and different anions. In an attempt to further examine the separation capabilities of the IL-based GC stationary phases, columns of the best performing stationary phases were prepared with higher film thickness and resulted in enhanced selectivity of aliphatic hydrocarbons.

  1. Solid phase microextraction-comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry for the analysis of honey volatiles.

    Science.gov (United States)

    Cajka, Tomás; Hajslová, Jana; Cochran, Jack; Holadová, Katerina; Klimánková, Eva

    2007-03-01

    Head-space solid phase microextration (SPME), followed by comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GCxGC-TOFMS), has been implemented for the analysis of honey volatiles, with emphasis on the optimal selection of SPME fibre and the first- and second-dimension GC capillaries. From seven SPME fibres investigated, a divinylbenzene/Carboxen/polydimethylsiloxane (DVB/CAR/PDMS) 50/30 microm fibre provided the best sorption capacity and the broadest range of volatiles extracted from the headspace of a mixed honey sample. A combination of DB-5ms x SUPELCOWAX 10 columns enabled the best resolution of sample components compared to the other two tested column configurations. Employing this powerful analytical strategy led to the identification of 164 volatile compounds present in a honey mixture during a 19-min GC run. Combination of this simple and inexpensive SPME-based sampling/concentration technique with the advanced separation/identification approach represented by GCxGC-TOFMS allows a rapid and comprehensive examination of the honey volatiles profile. In this way, the laboratory sample throughput can be increased significantly and, at the same time, the risk of erroneous identification, which cannot be avoided in one-dimensional GC separation, is minimised.

  2. Two-dimensional gas chromatography/mass spectrometry, physical property modeling and automated production of component maps to assess the weathering of pollutants.

    Science.gov (United States)

    Antle, Patrick M; Zeigler, Christian D; Livitz, Dimitri G; Robbat, Albert

    2014-10-17

    Local conditions influence how pollutants will weather in subsurface environments and sediment, and many of the processes that comprise environmental weathering are dependent upon these substances' physical and chemical properties. For example, the effects of dissolution, evaporation, and organic phase partitioning can be related to the aqueous solubility (SW), vapor pressure (VP), and octanol-water partition coefficient (KOW), respectively. This study outlines a novel approach for estimating these physical properties from comprehensive two-dimensional gas chromatography-mass spectrometry (GC×GC/MS) retention index-based polyparameter linear free energy relationships (LFERs). Key to robust correlation between GC measurements and physical properties is the accurate and precise generation of retention indices. Our model, which employs isovolatility curves to calculate retention indices, provides improved retention measurement accuracy for families of homologous compounds and leads to better estimates of their physical properties. Results indicate that the physical property estimates produced from this approach have the same error on a logarithmic-linear scale as previous researchers' log-log estimates, yielding a markedly improved model. The model was embedded into a new software program, allowing for automated determination of these properties from a single GC×GC analysis with minimal model training and parameter input. This process produces component maps that can be used to discern the mechanism and progression of how a particular site weathers due to dissolution, organic phase partitioning, and evaporation into the surrounding environment.

  3. Carrier dynamics of optical emission from two-dimensional electron gas in undoped AlGaN/GaN single heterojunctions

    Energy Technology Data Exchange (ETDEWEB)

    Kwack, H.S.; Cho, Y.H. [Department of Physics and Institute for Basic Science Research, Chungbuk National University, Cheongju 361-763 (Korea); Kim, G.H. [School of Information and Communication Engineering, Sungkyunkwan University, Suwon 440-746 (Korea); Park, M.R.; Youn, D.H.; Bae, S.B.; Lee, K.S. [Basic Research Laboratory, Electronics and Telecommunications Research Institute, Daejeon 305-350 (Korea); Lee, J.H.; Lee, J.H. [Department of Electric and Electronic Engineering, Kyungpook National University, Taegu 702-701 (Korea)

    2006-06-15

    The structural and optical properties of undoped AlGaN/GaN single heterojunctions (HJs) were studied by means of high-resolution x-ray diffraction, photoluminescence (PL), cathodoluminescence (CL), and time-resolved PL spectroscopy. An additional two-dimensional electron gas (2DEG)-related PL and CL emission appeared at about 40 meV below the GaN band-edge emission energy and persisted up to about 100 K, while this peak disappeared when the top AlGaN layer was removed by reactive ion etching. Depth-resolved CL spectra reveal the presence of a 2DEG at the heterointerface. The additional PL and CL emission below the GaN band-edge emission is attributed to the recombination between photogenerated holes and electrons confined at 2DEG states in the triangular-shaped interface potential. For the 2DEG emission, we observed an about 50-ps delayed rise time than the GaN and AlGaN emissions by using time-resolved PL, indicating effective carrier transfer from the GaN flatband and AlGaN regions to the heterointerface. From the results, we explained the optical properties and carrier recombination dynamics of 2DEG, GaN, and AlGaN emissions in undoped AlGaN/GaN single HJs. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Carrier dynamics of optical emission from two-dimensional electron gas in undoped AlGaN/GaN single heterojunctions

    Science.gov (United States)

    Kwack, H. S.; Cho, Y. H.; Kim, G. H.; Park, M. R.; Youn, D. H.; Bae, S. B.; Lee, K.-S.; Lee, J. H.; Lee, J. H.

    2006-06-01

    The strucutral and optical properties of undoped AlGaN/GaN single heterojunctions (HJs) were studied by means of high-resolution x-ray diffraction, photoluminescence (PL), cathodoluminescence (CL), and time-resolved PL spectroscopy. An additional two-dimensional electron gas (2DEG)-related PL and CL emission appeared at about 40 meV below the GaN band-edge emission energy and persisted up to about 100 K, while this peak disappeared when the top AlGaN layer was removed by reactive ion etching. Depth-resolved CL spectra reveal the presence of a 2DEG at the heterointerface. The additional PL and CL emission below the GaN band-edge emission is attributed to the recombination between photogenerated holes and electrons confined at 2DEG states in the triangular-shaped interface potential. For the 2DEG emission, we observed an about 50-ps delayed rise time than the GaN and AlGaN emissions by using time-resolved PL, indicating effective carrier transfer from the GaN flatband and AlGaN regions to the heterointerface. From the results, we explained the optical properties and carrier recombination dynamics of 2DEG, GaN, and AlGaN emissions in undoped AlGaN/GaN single HJs.

  5. Fano resonance in the nonadiabatically pumped shot noise of a time-dependent quantum well in a two-dimensional electron gas and graphene

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Rui, E-mail: rzhu@scut.edu.cn; Dai, Jiao-Hua [Department of Physics, South China University of Technology, Guangzhou 510641 (China); Guo, Yong [Department of Physics and State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China)

    2015-04-28

    Interference between different quantum paths can generate Fano resonance. One of the examples is transport through a quasibound state driven by a time-dependent scattering potential. Previously it is found that Fano resonance occurs as a result of energy matching in one-dimensional systems. In this work, we demonstrate that when transverse motion is present, Fano resonance occurs precisely at the wavevector matching situation. Using the Floquet scattering theory, we considered the transport properties of a nonadiabatic time-dependent well both in a two-dimensional electron gas and monolayer graphene structure. Dispersion of the quasibound state of a static quantum well is obtained with transverse motion present. We found that Fano resonance occurs when the wavevector in the transport direction of one of the Floquet sidebands is exactly identical to that of the quasibound state in the well at equilibrium and follows the dispersion pattern of the latter. To observe the Fano resonance phenomenon in the transmission spectrum, we also considered the pumped shot noise properties when time and spatial symmetry secures vanishing current in the considered configuration. Prominent Fano resonance is found in the differential pumped shot noise with respect to the reservoir Fermi energy.

  6. Comparison between theoretical and experimental results for energy states of two-dimensional electron gas in pseudomorphically strained InAs high-electron-mobility transistors

    Science.gov (United States)

    Nishio, Yui; Tange, Takahiro; Hirayama, Naomi; Iida, Tsutomu; Takanashi, Yoshifumi

    2014-01-01

    The energy states of a two-dimensional electron gas (2DEG) in high-electron-mobility transistors with a pseudomorphically strained InAs channel (PHEMTs) were analyzed rigorously using a recently established theory that takes into account the nonparabolicity of the conduction band of the channel layer. The sheet density of the 2DEG in InxGa1-xAs-PHEMTs and the drain I-V characteristics of those devices were calculated theoretically and compared with the density and characteristics obtained experimentally. Not only the calculated threshold voltage (VTH) but also the calculated transconductance agreed fairly well with the corresponding values obtained experimentally. When the effects of the compositions of the InxGa1-xAs subchannel layer in the composite channel and the channel layer on energy states of 2DEG were investigated in order to establish a guiding principle for a design of the channel structure in PHEMTs, it was found that VTH is determined by the effective conduction-band offset energy ΔEC between the InAlAs barrier and the channel layers.

  7. On-line combination of high performance liquid chromatography with comprehensive two-dimensional gas chromatography-triple quadrupole mass spectrometry: a proof of principle study.

    Science.gov (United States)

    Zoccali, Mariosimone; Tranchida, Peter Quinto; Mondello, Luigi

    2015-02-03

    The present contribution is focused on the on-line combination of high performance liquid chromatography (HPLC), cryogenically modulated comprehensive two-dimensional gas chromatography (GC × GC), and triple quadrupole mass spectrometry (QqQ MS), generating a very powerful unified separation-science tool. The instrument can be used in seven different combinations ranging from one-dimensional HPLC with a photodiode array detector to on-line LC × GC × GC/QqQ MS. The main focus of the present research is directed to the LC-GC × GC/QqQ MS configuration, with its analytical potential shown in a proof-of-principle study involving a very complex sample, namely, coal tar. Specifically, a normal-phase LC process enabled the separation of three classes of coal tar compounds: (1) nonaromatic hydrocarbons; (2) unsaturated compounds (with and without S); (3) oxygenated constituents. The HPLC fractions were transferred to the GC × GC instrument via a syringe-based interface mounted on an autosampler. Each fraction was subjected to a specific programmed temperature vaporizer GC × GC/QqQ MS untargeted or targeted analysis. For example, the coal tar S-containing compounds were pinpointed through multiple-reaction-monitoring analysis, while full-scan information was attained for the oxygenated constituents.

  8. Comprehensive magnetotransport characterization of two dimensional electron gas in AlGaN/GaN high electron mobility transistor structures leading to the assessment of interface roughness

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, Manna Kumari [Solid State Physics Laboratory, Lucknow Road, Timarpur, Delhi-110054 (India); Netaji Subhas Institute of Technology, Dwarka, New Delhi-110078 (India); Sharma, Rajesh K., E-mail: rksharma@sspl.drdo.in; Manchanda, Rachna; Bag, Rajesh K.; Muralidharan, Rangarajan [Solid State Physics Laboratory, Lucknow Road, Timarpur, Delhi-110054 (India); Thakur, Om Prakash [Netaji Subhas Institute of Technology, Dwarka, New Delhi-110078 (India)

    2014-09-15

    Magnetotransport in two distinct AlGaN/GaN HEMT structures grown by Molecular Beam Epitaxy (MBE) on Fe-doped templates is investigated using Shubnikov de-Haas Oscillations in the temperature range of 1.8–6 K and multicarrier fitting in the temperature range of 1.8–300 K. The temperature dependence of the two dimensional electron gas mobility is extracted from simultaneous multicarrier fitting of transverse and longitudinal resistivity as a function of magnetic field and the data is utilized to estimate contribution of interface roughness to the mobility and the corresponding transport lifetime. The quantum scattering time obtained from the analysis of Shubnikov de Haas Oscillations in transverse magnetoresistance along with the transport lifetime time were used to estimate interface roughness amplitude and lateral correlation length. The results indicate that the insertion of AlN over layer deposited prior to the growth of GaN base layer on Fe doped GaN templates for forming HEMT structures reduced the parallel conduction but resulted in an increase in interface roughness.

  9. Comprehensive magnetotransport characterization of two dimensional electron gas in AlGaN/GaN high electron mobility transistor structures leading to the assessment of interface roughness

    Directory of Open Access Journals (Sweden)

    Manna Kumari Mishra

    2014-09-01

    Full Text Available Magnetotransport in two distinct AlGaN/GaN HEMT structures grown by Molecular Beam Epitaxy (MBE on Fe-doped templates is investigated using Shubnikov de-Haas Oscillations in the temperature range of 1.8–6 K and multicarrier fitting in the temperature range of 1.8–300 K. The temperature dependence of the two dimensional electron gas mobility is extracted from simultaneous multicarrier fitting of transverse and longitudinal resistivity as a function of magnetic field and the data is utilized to estimate contribution of interface roughness to the mobility and the corresponding transport lifetime. The quantum scattering time obtained from the analysis of Shubnikov de Haas Oscillations in transverse magnetoresistance along with the transport lifetime time were used to estimate interface roughness amplitude and lateral correlation length. The results indicate that the insertion of AlN over layer deposited prior to the growth of GaN base layer on Fe doped GaN templates for forming HEMT structures reduced the parallel conduction but resulted in an increase in interface roughness.

  10. Giant tunneling electroresistance induced by ferroelectrically switchable two-dimensional electron gas at nonpolar BaTiO3/SrTiO3 interface

    Science.gov (United States)

    Wu, Qingyun; Shen, Lei; Yang, Ming; Zhou, Jun; Chen, Jingsheng; Feng, Yuan Ping

    2016-10-01

    Using first-principles calculations, we investigate the tunneling electroresistance (TER) of ferroelectric tunnel junctions [Pt /BaTiO3(BTO)/SrTiO3(STO )/Pt ]. It is found that the TER of Pt/BTO/STO/Pt junctions can be greatly increased with increasing thickness of STO layers. The underlying physics of this giant TER is the switchable two-dimensional electron gas (2DEG) at a nonpolar BTO/STO interface induced by the ferroelectric polarization. Our calculations show that when the ferroelectric polarization is pointing from BTO to STO, a 2DEG forms at the interface and acts as bridge for electrons to tunnel through the junctions. Nevertheless, there is no 2DEG at the interface under the opposite direction of the ferroelectric polarization, which results in a large tunnel resistance. More importantly, this ferroelectrically switchable 2DEG leads to a low resistance area product for Pt/BTO/STO/Pt junctions, which offers good compatibility with other components in an integrated circuit and is highly desired for industrial applications.

  11. Application of comprehensive two-dimensional gas chromatography with mass spectrometric detection for the analysis of selected drug residues in wastewater and surface water

    Institute of Scientific and Technical Information of China (English)

    Petr Lacina; Ludmila Mravcová; Milada Vávrová

    2013-01-01

    Pharmaceutical residues have become tightly controlled environmental contaminants in recent years,due to their increasing concentration in environmental components.This is mainly caused by their high level of production and everyday consumption.Therefore there is a need to apply new and sufficiently sensitive analytical methods,which can detect the presence of these contaminants even in very low concentrations.This study is focused on the application of a reliable analytical method for the analysis of 10 selected drug residues,mainly from the group of non-steroidal anti-iaffammatory drugs (salicylic acid,acetylsalicylic acid,clofibric acid,ibuprofen,acetaminophen,caffeine,naproxen,mefenamic acid,ketoprofen,and dicofenac),in wastewaters and surface waters.This analytical method is based on solid phase extraction,derivatization by N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) and finally analysis by comprehensive two-dimensional gas chromatography with Time-of-Flight mass spectrometric detection (GCxGC-TOF MS).Detection limits ranged from 0.18 to 5 ng/L depending on the compound and selected matrix.The method was successfully applied for detection of the presence of selected pharmaceuticals in the Svratka River and in wastewater from the wastewater treatment plant in Brno-Modrice,Czech Republic.The concentration of pharmaceuticals varied from one to several hundreds of ng/L in surface water and from one to several tens of μg/L in wastewater.

  12. Analysis of honeybush tea (Cyclopia spp.) volatiles by comprehensive two-dimensional gas chromatography using a single-stage thermal modulator.

    Science.gov (United States)

    Ntlhokwe, Gaalebalwe; Tredoux, Andreas G J; Górecki, Tadeusz; Edwards, Matthew; Vestner, Jochen; Muller, Magdalena; Erasmus, Lené; Joubert, Elizabeth; Christel Cronje, J; de Villiers, André

    2017-07-01

    The applicability of comprehensive two-dimensional gas chromatography (GC×GC) using a single-stage thermal modulator was explored for the analysis of honeybush tea (Cyclopia spp.) volatile compounds. Headspace solid phase micro-extraction (HS-SPME) was used in combination with GC×GC separation on a non-polar × polar column set with flame ionisation (FID) detection for the analysis of fermented Cyclopia maculata, Cyclopia subternata and Cyclopia genistoides tea infusions of a single harvest season. Method optimisation entailed evaluation of the effects of several experimental parameters on the performance of the modulator, the choice of columns in both dimensions, as well as the HS-SPME extraction fibre. Eighty-four volatile compounds were identified by co-injection of reference standards. Principal component analysis (PCA) showed clear differentiation between the species based on their volatile profiles. Due to the highly reproducible separations obtained using the single-stage thermal modulator, multivariate data analysis was simplified. The results demonstrate both the complexity of honeybush volatile profiles and the potential of GC×GC separation in combination with suitable data analysis techniques for the investigation of the relationship between sensory properties and volatile composition of these products. The developed method therefore offers a fast and inexpensive methodology for the profiling of honeybush tea volatiles. Graphical abstract Surface plot obtained for the GC×GC-FID analysis of honeybush tea volatiles.

  13. Two-dimensional Kagome photonic bandgap waveguide

    DEFF Research Database (Denmark)

    Nielsen, Jens Bo; Søndergaard, Thomas; Libori, Stig E. Barkou;

    2000-01-01

    The transverse-magnetic photonic-bandgap-guidance properties are investigated for a planar two-dimensional (2-D) Kagome waveguide configuration using a full-vectorial plane-wave-expansion method. Single-moded well-localized low-index guided modes are found. The localization of the optical modes...... is investigated with respect to the width of the 2-D Kagome waveguide, and the number of modes existing for specific frequencies and waveguide widths is mapped out....

  14. Complex Saddles in Two-dimensional Gauge Theory

    CERN Document Server

    Buividovich, P V; Valgushev, S N

    2015-01-01

    We study numerically the saddle point structure of two-dimensional (2D) lattice gauge theory, represented by the Gross-Witten-Wadia unitary matrix model. The saddle points are in general complex-valued, even though the original integration variables and action are real. We confirm the trans-series/instanton gas structure in the weak-coupling phase, and identify a new complex-saddle interpretation of non-perturbative effects in the strong-coupling phase. In both phases, eigenvalue tunneling refers to eigenvalues moving off the real interval, into the complex plane, and the weak-to-strong coupling phase transition is driven by saddle condensation.

  15. Characterisation of dense non-aqueous phase liquids of coal tar using comprehensive two-dimensional gas chromatography coupled with time of flight mass spectrometry.

    Science.gov (United States)

    Gauchotte-Lindsay, Caroline; McGregor, Laura; Richards, Phil; Kerr, Stephanie; Glenn, Aliyssa; Thomas, Russell; Kalin, Robert

    2013-04-01

    Comprehensive two-dimensional gas chromatography (GCxGC) is a recently developed analytical technique in which two capillary columns with different stationary phases are placed in series enabling planar resolution of the analytes. The resolution power of GCxGC is one order of magnitude higher than that of one dimension gas chromatography. Because of its high resolution capacity, the use of GCxGC for complex environmental samples such as crude oils, petroleum derivatives and polychlorinated biphenyls mixtures has rapidly grown in recent years. We developed a one-step method for the forensic analysis of coal tar dense non-aqueous phase liquids (DNAPLs) from former manufactured gas plant (FMGP) sites. Coal tar is the by-product of the gasification of coal for heating and lighting and it is composed of thousands of organic and inorganic compounds. Before the boom of natural gases and oils, most towns and cities had one or several manufactured gas plants that have, in many cases, left a devastating environmental print due to coal tar contamination. The fate of coal tar DNAPLs, which can persist in the environment for more than a hundred years, is therefore of crucial interest. The presented analytical method consists of a unique clean-up/ extraction stage by pressurized liquid extraction and a single analysis of its organic chemical composition using GCxGC coupled with time of flight mass spectrometry (TOFMS). The chemical fingerprinting is further improved by derivatisation by N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) of the tar compounds containing -OH functions such as alcohols and carboxylic acids. We present here how, using the logical order of elution in GCxGC-TOFMS system, 1) the identification of never before observed -OH containing compounds is possible and 2) the isomeric selectivity of an oxidation reaction on a DNAPL sample can be revealed. Using samples collected at various FMGP sites, we demonstrate how this GCxGC method enables the simultaneous

  16. Coherence properties of a 2D trapped Bose gas around the superfluid transition

    CERN Document Server

    Plisson, T; Holzmann, M; Salomon, G; Aspect, Alain; Bouyer, Philippe; Bourdel, Thomas

    2011-01-01

    We measure the momentum distribution of a 2D trapped Bose gas and observe the increase of the range of coherence around the Berezinskii-Kosterlitz-Thouless (BKT) transition. We quantitatively compare our observed profiles to both a Hartee-Fock mean-field theory and to quantum Monte-Carlo simulations. In the normal phase, we already observe a sharpening of the momentum distribution. This behavior is partially captured in a mean-field approach, in contrast to the physics of the BKT transition.

  17. High Sensitivity 1-D and 2-D Microwave Spectroscopy via Cryogenic Buffer Gas Cooling

    Science.gov (United States)

    Patterson, David; Eibenberger, Sandra

    2017-06-01

    All rotationally resolved spectroscopic methods rely on sources of cold molecules. For the last three decades, the workhorse technique for producing highly supersaturated samples of cold molecules has been the pulsed supersonic jet. We present here progress on our alternative method, cryogenic buffer gas cooling. Our high density, continuous source, and low noise temperature allow us to record microwave spectra at unprecedented sensitivity, with a dynamic range in excess of 10^6 achievable in a few minutes of integration time. This high sensitivity enables new protocols in both 1-D and 2-D microwave spectroscopy, including sensitive chiral analysis via nonlinear three wave mixing and applications as an analytical chemistry tool

  18. Coulomb scattering in a 2D interacting electron gas and production of EPR pairs.

    Science.gov (United States)

    Saraga, D S; Altshuler, B L; Loss, Daniel; Westervelt, R M

    2004-06-18

    We propose a setup to generate nonlocal spin Einstein-Podolsky-Rosen pairs via pair collisions in a 2D interacting electron gas, based on constructive two-particle interference in the spin-singlet channel at the pi/2 scattering angle. We calculate the scattering amplitude via the Bethe-Salpeter equation in the ladder approximation and small r(s) limit and find that the Fermi sea leads to a substantial renormalization of the bare scattering process. From the scattering length, we estimate the current of spin-entangled electrons and show that it is within experimental reach.

  19. Piezoelectricity in Two-Dimensional Materials

    KAUST Repository

    Wu, Tao

    2015-02-25

    Powering up 2D materials: Recent experimental studies confirmed the existence of piezoelectricity - the conversion of mechanical stress into electricity - in two-dimensional single-layer MoS2 nanosheets. The results represent a milestone towards embedding low-dimensional materials into future disruptive technologies. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.

  20. A two-dimensional Dirac fermion microscope

    DEFF Research Database (Denmark)

    Bøggild, Peter; Caridad, Jose; Stampfer, Christoph

    2017-01-01

    in the solid state. Here we provide a perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons. We use semiclassical simulations to propose concrete architectures and design rules of 2...

  1. Laser Absorption spectrometer instrument for tomographic 2D-measurement of climate gas emission from soils

    Science.gov (United States)

    Seidel, Anne; Wagner, Steven; Dreizler, Andreas; Ebert, Volker

    2014-05-01

    One of the most intricate effects in climate modelling is the role of permafrost thawing during the global warming process. Soil that has formerly never totally lost its ice cover now emits climate gases due to melting processes[1]. For a better prediction of climate development and possible feedback mechanisms, insights into physical procedures (like e.g. gas emission from underground reservoirs) are required[2]. Therefore, a long-term quantification of greenhouse gas concentrations (and further on fluxes) is necessary and the related structures that are responsible for emission need to be identified. In particular the spatial heterogeneity of soils caused by soil internal structures (e.g. soil composition changes or surface cracks) or by surface modifications (e.g. by plant growth) generate considerable complexities and difficulties for local measurements, for example with soil chambers. For such situations, which often cannot be avoided, a spatially resolved 2D-measurement to identify and quantify the gas emission from the structured soil would be needed, to better understand the influence of the soil sub-structures on the emission behavior. Thus we designed a spatially scanning laser absorption spectrometer setup to determine a 2D-gas concentration map in the soil-air boundary layer. The setup is designed to cover the surfaces in the range of square meters in a horizontal plane above the soil to be investigated. Existing field instruments for gas concentration or flux measurements are based on point-wise measurements, so structure identification is very tedious or even impossible. For this reason, we have developed a tomographic in-situ instrument based on TDLAS ('tunable diode laser absorption spectroscopy') that delivers absolute gas concentration distributions of areas with 0.8m × 0.8m size, without any need for reference measurements with a calibration gas. It is a simple and robust device based on a combination of scanning mirrors and reflecting foils, so

  2. Two-dimensional calculus

    CERN Document Server

    Osserman, Robert

    2011-01-01

    The basic component of several-variable calculus, two-dimensional calculus is vital to mastery of the broader field. This extensive treatment of the subject offers the advantage of a thorough integration of linear algebra and materials, which aids readers in the development of geometric intuition. An introductory chapter presents background information on vectors in the plane, plane curves, and functions of two variables. Subsequent chapters address differentiation, transformations, and integration. Each chapter concludes with problem sets, and answers to selected exercises appear at the end o

  3. Two dimensional vernier

    Science.gov (United States)

    Juday, Richard D. (Inventor)

    1992-01-01

    A two-dimensional vernier scale is disclosed utilizing a cartesian grid on one plate member with a polar grid on an overlying transparent plate member. The polar grid has multiple concentric circles at a fractional spacing of the spacing of the cartesian grid lines. By locating the center of the polar grid on a location on the cartesian grid, interpolation can be made of both the X and Y fractional relationship to the cartesian grid by noting which circles coincide with a cartesian grid line for the X and Y direction.

  4. Correlation of rocket propulsion fuel properties with chemical composition using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry followed by partial least squares regression analysis.

    Science.gov (United States)

    Kehimkar, Benjamin; Hoggard, Jamin C; Marney, Luke C; Billingsley, Matthew C; Fraga, Carlos G; Bruno, Thomas J; Synovec, Robert E

    2014-01-31

    There is an increased need to more fully assess and control the composition of kerosene-based rocket propulsion fuels such as RP-1. In particular, it is critical to make better quantitative connections among the following three attributes: fuel performance (thermal stability, sooting propensity, engine specific impulse, etc.), fuel properties (such as flash point, density, kinematic viscosity, net heat of combustion, and hydrogen content), and the chemical composition of a given fuel, i.e., amounts of specific chemical compounds and compound classes present in a fuel as a result of feedstock blending and/or processing. Recent efforts in predicting fuel chemical and physical behavior through modeling put greater emphasis on attaining detailed and accurate fuel properties and fuel composition information. Often, one-dimensional gas chromatography (GC) combined with mass spectrometry (MS) is employed to provide chemical composition information. Building on approaches that used GC-MS, but to glean substantially more chemical information from these complex fuels, we recently studied the use of comprehensive two dimensional (2D) gas chromatography combined with time-of-flight mass spectrometry (GC×GC-TOFMS) using a "reversed column" format: RTX-wax column for the first dimension, and a RTX-1 column for the second dimension. In this report, by applying chemometric data analysis, specifically partial least-squares (PLS) regression analysis, we are able to readily model (and correlate) the chemical compositional information provided by use of GC×GC-TOFMS to RP-1 fuel property information such as density, kinematic viscosity, net heat of combustion, and so on. Furthermore, we readily identified compounds that contribute significantly to measured differences in fuel properties based on results from the PLS models. We anticipate this new chemical analysis strategy will have broad implications for the development of high fidelity composition-property models, leading to an

  5. Two-dimensional graphene analogues for biomedical applications.

    Science.gov (United States)

    Chen, Yu; Tan, Chaoliang; Zhang, Hua; Wang, Lianzhou

    2015-05-07

    The increasing demand of clinical biomedicine and fast development of nanobiotechnology has substantially promoted the generation of a variety of organic/inorganic nanosystems for biomedical applications. Biocompatible two-dimensional (2D) graphene analogues (e.g., nanosheets of transition metal dichalcogenides, transition metal oxides, g-C3N4, Bi2Se3, BN, etc.), which are referred to as 2D-GAs, have emerged as a new unique family of nanomaterials that show unprecedented advantages and superior performances in biomedicine due to their unique compositional, structural and physicochemical features. In this review, we summarize the state-of-the-art progress of this dynamically developed material family with a particular focus on biomedical applications. After the introduction, the second section of the article summarizes a range of synthetic methods for new types of 2D-GAs as well as their surface functionalization. The subsequent section provides a snapshot on the use of these biocompatible 2D-GAs for a broad spectrum of biomedical applications, including therapeutic (photothermal/photodynamic therapy, chemotherapy and synergistic therapy), diagnostic (fluorescent/magnetic resonance/computed tomography/photoacoustic imaging) and theranostic (concurrent diagnostic imaging and therapy) applications, especially on oncology. In addition, we briefly present the biosensing applications of these 2D-GAs for the detection of biomacromolecules and their in vitro/in vivo biosafety evaluations. The last section summarizes some critical unresolved issues, possible challenges/obstacles and also proposes future perspectives related to the rational design and construction of 2D-GAs for biomedical engineering, which are believed to promote their clinical translations for benefiting the personalized medicine and human health.

  6. Crosslinked structurally-tuned polymeric ionic liquids as stationary phases for the analysis of hydrocarbons in kerosene and diesel fuels by comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    Zhang, Cheng; Park, Rodney A; Anderson, Jared L

    2016-04-01

    Structurally-tuned ionic liquids (ILs) have been previously applied as the second dimension column in comprehensive two-dimensional gas chromatography (GC×GC) and have demonstrated high selectivity in the separation of individual aliphatic hydrocarbons from other aliphatic hydrocarbons. However, the maximum operating temperatures of these stationary phases limit the separation of analytes with high boiling points. In order to address this issue, a series of polymeric ionic liquid (PIL)-based stationary phases were prepared in this study using imidazolium-based IL monomers via in-column free radical polymerization. The IL monomers were functionalized with long alkyl chain substituents to provide the needed selectivity for the separation of aliphatic hydrocarbons. Columns were prepared with different film thicknesses to identify the best performing stationary phase for the separation of kerosene. The bis[(trifluoromethyl)sulfonyl]imide ([NTf2](-))-based PIL stationary phase with larger film thickness (0.28μm) exhibited higher selectivity for aliphatic hydrocarbons and showed a maximum allowable operating temperature of 300°C. PIL-based stationary phases containing varied amount of IL-based crosslinker were prepared to study the effect of the crosslinker on the selectivity and thermal stability of the resulting stationary phase. The optimal resolution of aliphatic hydrocarbons was achieved when 50% (w/w) of crosslinker was incorporated into the PIL-based stationary phase. The resulting stationary phase exhibited good selectivity for different groups of aliphatic hydrocarbons even after being conditioned at 325°C. Finally, the crosslinked PIL-based stationary phase was compared with SUPELCOWAX 10 and DB-17 columns for the separation of aliphatic hydrocarbons in diesel fuel. Better resolution of aliphatic hydrocarbons was obtained when employing the crosslinked PIL-based stationary phase as the second dimension column.

  7. Improved electrical properties of the two-dimensional electron gas in AlGaN/GaN heterostructures using high temperature AlN interlayers

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The electrical properties of two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures using high temperature (HT) AlN interlayers (ITs) grown on c-plane sapphire substrate by metal organic chemical vapor deposition (MOCVD) have been investigated.It is found that the electrical properties (electron mobility and sheet carrier density) are improved compared with those in the conventional AlGaN/GaN heterostructures without HT AlN ITs,and the improved 2DEG properties result in the reduction of the sheet resistance.The results from high resolution X-ray diffraction (HRXRD) and Raman spectroscopy measurements show that HT AlN ITs increase the in-plane compressive strain in the upper GaN layer,which enhances the piezoelectric polarization in it and consequently causes increasing of 2DEG density at the AlGaN/GaN interface.Meanwhile,the compressive strain induced by HT AlN ITs leads to a less tensile strain in AlGaN barrier layer and causes positive and negative effects on the sheet carrier density of 2DEG,which counteract each other.The HT AlN ITs reduce the lattice mismatch between the GaN and AlGaN layers and smooth the interface between them,thus increasing the electric mobility of 2DEG by weakening the alloy-related interface roughness and scattering.In addition,the surface morphology of AlGaN/GaN heterostructures is improved by the insertion of HT AlN ITs.The reason for the improved properties is discussed in this paper.

  8. Impurity Profiling of a Chemical Weapon Precursor for Possible Forensic Signatures by Comprehensive Two-Dimensional Gas Chromatography/Mass Spectrometry and Chemometrics

    Energy Technology Data Exchange (ETDEWEB)

    Hoggard, Jamin C.; Wahl, Jon H.; Synovec, Robert E.; Mong, Gary M.; Fraga, Carlos G.

    2010-01-15

    In this work we present the feasibility of using analytical chemical and chemometric methodologies to reveal and exploit the organic impurity profiles from commercial dimethyl methylphosphonate (DMMP) samples to illustrate the type of forensic information that may be obtained from chemical-attack evidence. Using DMMP as a model compound for a toxicant that may be used in a chemical attack, we used comprehensive two-dimensional gas chromatography mass spectrometric detection (GC × GC-TOFMS) to detect and identify trace organic impurities in six samples of commercially acquired DMMP. The GC x GC-TOFMS data were analyzed to produce impurity profiles for all six DMMP samples using 29 analyte impurities. The use of PARAFAC for the mathematical resolution of overlap GC x GC peaks ensured clean spectra for the identification of many of the detected analytes by spectral library matching. The use of statistical pairwise comparison revealed that there were trace impurities that were quantitatively similar and different among five of the six DMMP samples. Two of the DMMP samples were revealed to have identical impurity profiles by this approach. The use of nonnegative matrix factorization proved that there were five distinct DMMP sample types as illustrated by the clustering of the multiple DMMP analyses into 5 distinct clusters in the scores plots. The two indistinguishable DMMP samples were confirmed by their chemical supplier to be from the same bulk source. Sample information from the other chemical suppliers supported that the other five DMMP samples were likely from different bulk sources. These results demonstrate that the matching of synthesized products from the same source is possible using impurity profiling. In addition, the identified impurities common to all six DMMP samples provide strong evidence that basic route information can be obtained from impurity profiles. In addition, impurities that may be unique to the sole bulk manufacturer of DMMP were found in

  9. Effect of {sup 60}Co gamma-irradiation on two-dimensional electron gas transport and device characteristics of AlGaN/GaN HEMTs

    Energy Technology Data Exchange (ETDEWEB)

    Umana-Membreno, G.A.; Dell, J.M.; Parish, G.; Nener, B.D.; Faraone, L. [School of Electrical, Electronic and Computer Engineering, The University ofWestern Australia, Crawley WA 6009 (Australia); Ventury, R.; Mishra, U.K. [Dept. of Electrical and Computer Engineering, University of California, Santa Barbara, CA 93106 (United States)

    2005-05-01

    The effect of {sup 60}Co gamma-irradiation on Al{sub 0.33}Ga{sub 0.67}N/GaN high-electron-mobility transistors (HEMTs) has been investigated using DC and geometrical magnetoresistance measurements. The devices studied were of similar epitaxial structure, yet differed in the doping levels of the Al{sub 0.33}Ga{sub 0.67}N barrier layer: (A) nominally undoped and (B) Si-doped with SiN{sub x} passivation. Exposure to cumulative gamma-ray doses up to 20 Mrad(Si) is shown to induce significant changes in drain-current level, threshold voltage and gate leakage current level. Analysis of magnetoresistance characteristics measured at 80 K indicated that irradiation induced an increase in two-dimensional electron-gas (2DEG) density, which leads to negative threshold voltage shifts observable in the drain current versus gate voltage characteristics, attributable to the introduction of defect centers in the Al{sub 0.33}Ga{sub 0.67}N layer and/or at the gate-AlGaN interface. The 2DEG mobility-concentration profiles are shown to remain approximately unchanged for doses up to 20 Mrad(Si). Device failure, evidenced as loss of gate control over the channel and/or excessive gate leakage, occurred after exposure to 30 Mrad(Si) for device A, whereas sample B failed after 20 Mrad(Si) total dose due to failure of half of the gate contact. Degradation of gate and source/drain contacts characteristics with total dose appears to limit the tolerance of the studied HEMTs to {sup 60}Co gamma-irradiation. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Separation and screening of short-chain chlorinated paraffins in environmental samples using comprehensive two-dimensional gas chromatography with micro electron capture detection.

    Science.gov (United States)

    Xia, Dan; Gao, Lirong; Zhu, Shuai; Zheng, Minghui

    2014-11-01

    Short-chain chlorinated paraffins (SCCPs) are highly complex technical mixtures with thousands of isomers and numerous homologs. They are classified as priority candidate persistent organic pollutants under the Stockholm Convention for their persistence, bioaccumulation, and toxicity. Analyzing SCCPs is challenging because of the complexity of the mixtures. Chromatograms of SCCPs acquired using one-dimensional (1D) gas chromatography (GC) contain a large characteristic "peak" with a broad and unresolved profile. Comprehensive two-dimensional GC (GC×GC) shows excellent potential for separating complex mixtures. In this study, GC×GC coupled with micro electron capture detection (μECD) was used to separate and screen SCCPs. The chromatographic parameters, including the GC column types, oven temperature program, and modulation period, were systematically optimized. The SCCP congeners were separated into groups using a DM-1 column connected to a BPX-50 column. The SCCP congeners in technical mixtures were separated according to the number of chlorine substituents for a given carbon chain length and according to the number of carbon atoms plus chlorine atoms for different carbon chain lengths. A fish tissue sample was analyzed to illustrate the feasibility of the GC×GC-μECD method in analyzing biological samples. Over 1,500 compounds were identified in the fish extract, significantly more than were identified using 1D GC. The detection limits for five selected SCCP congeners were between 1 and 5 pg/L using the GC×GC method, and these were significantly lower than those achieved using 1D GC. This method is a good choice for analysis of SCCPs in environmental samples, exhibiting good separation and good sensitivity.

  11. Implementation of comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry for the simultaneous determination of halogenated contaminants and polycyclic aromatic hydrocarbons in fish

    Energy Technology Data Exchange (ETDEWEB)

    Kalachova, Kamila; Pulkrabova, Jana; Cajka, Tomas; Drabova, Lucie; Hajslova, Jana [Institute of Chemical Technology, Prague (Czech Republic). Department of Food Chemistry and Analysis, Faculty of Food and Biochemical Technology

    2012-07-15

    In the presented study, comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC x GC-TOFMS) was shown to be a powerful tool for the simultaneous determination of various groups of contaminants including 18 polychlorinated biphenyls (PCBs), seven polybrominated diphenyl ethers (PBDEs), and 16 polycyclic aromatic hydrocarbons (PAHs). Since different groups of analytes (traditionally analyzed separately) were included into one instrumental method, significant time savings were achieved. Following the development of an integrated sample preparation procedure for an effective and rapid isolation of several groups of contaminants from fish tissue, the GC x GC-TOFMS instrumental method was optimized to obtain the best chromatographic resolution and low quantification limits (LOQs) of all target analytes in a complex mixture. Using large-volume programmable temperature vaporization, the following LOQs were achieved - PCBs, 0.01-0.25 {mu}g/kg; PBDEs, 0.025-5 {mu}g/kg; PAHs 0.025-0.5 {mu}g/kg. Furthermore, several capillary column combinations (BPX5, BPX50, and Rxi-17Sil-ms in the first dimension and BPX5, BPX50, Rt-LC35, and HT8 in the second dimension) were tested during the experiments, and the optimal separation of all target analytes even of critical groups of PAHs (group (a): benz[a]anthracene, cyclopenta[cd]pyrene and chrysene; group (b): benzo[b]fluoranthene, benzo[j]fluoranthene and benzo[k]fluoranthene; group (c): dibenz[ah]anthracene, indeno[1,2,3-cd]pyrene and benzo[ghi]perylene) was observed on BPX5 x BPX50 column setup. Moreover, since the determination of target analytes was performed using TOFMS detector, further identification of other non-target compounds in real life samples was also feasible. (orig.)

  12. Congener-specific carbon isotopic analysis of technical PCB and PCN mixtures using two-dimensional gas chromatography-isotope ratio mass spectrometry.

    Science.gov (United States)

    Horii, Yuichi; Kannan, Kurunthachalam; Petrick, Gert; Gamo, Toshitaka; Falandysz, Jerzy; Yamashita, Nobuyoshi

    2005-06-01

    Analysis of stable carbon isotope fractionation is a useful method to study the sources and fate of anthropogenic organic contaminants such as polychlorinated biphenyls (PCBs) in the environment. To evaluate the utility of carbon isotopes, determination of isotopic ratios of 13C/12C in source materials, for example, technical PCB preparations, is needed. In this study, we determined delta13C values of 31 chlorobiphenyl (CB) congeners in 18 technical PCB preparations and 15 chloronaphthalene (CN) congeners in 6 polychlorinated naphthalene preparations using two-dimensional gas chromatography-combustion furnace-isotope ratio mass spectrometry (2DGC-C-IRMS). Development of 2DGC-IRMS enabled improved resolution and sensitivity of compound-specific carbon isotope analysis (CSIA) of CB or CN congeners. Delta13C values of PCB congeners ranged from -34.4 (Delors) to -22.0/1000 (Sovol). Analogous PCB preparations with similar chlorine content, but different geographical origin, had different delta13C values. PCB preparations from Eastern European countries--Delors, Sovol, Trichlorodiphenyl, and Chlorofen--had distinct delta13C values. PCB mixtures showed increased 13C depletion with increasing chlorine content. Delta13C values for individual CB congeners varied depending on the degree of chlorination in technical mixtures. Delta13C values of CN congeners in Halowaxes ranged from -26.3 to -21.7/1000 and these values are within the ranges observed for PCBs. This study establishes the range of delta13C values in technical PCB and PCN preparations, which may prove to be useful in the determination of sources of these compounds in the environment. This is the first study to employ 2DGC-IRMS analysis of delta13C values in technical PCB and PCN preparations.

  13. Energetic, spatial, and momentum character of the electronic structure at a buried interface: The two-dimensional electron gas between two metal oxides

    Science.gov (United States)

    Nemšák, S.; Conti, G.; Gray, A. X.; Palsson, G. K.; Conlon, C.; Eiteneer, D.; Keqi, A.; Rattanachata, A.; Saw, A. Y.; Bostwick, A.; Moreschini, L.; Rotenberg, E.; Strocov, V. N.; Kobayashi, M.; Schmitt, T.; Stolte, W.; Ueda, S.; Kobayashi, K.; Gloskovskii, A.; Drube, W.; Jackson, C. A.; Moetakef, P.; Janotti, A.; Bjaalie, L.; Himmetoglu, B.; Van de Walle, C. G.; Borek, S.; Minar, J.; Braun, J.; Ebert, H.; Plucinski, L.; Kortright, J. B.; Schneider, C. M.; Balents, L.; de Groot, F. M. F.; Stemmer, S.; Fadley, C. S.

    2016-06-01

    The interfaces between two condensed phases often exhibit emergent physical properties that can lead to new physics and novel device applications and are the subject of intense study in many disciplines. We here apply experimental and theoretical techniques to the characterization of one such interesting interface system: the two-dimensional electron gas (2DEG) formed in multilayers consisting of SrTi O3 (STO) and GdTi O3 (GTO). This system has been the subject of multiple studies recently and shown to exhibit very high carrier charge densities and ferromagnetic effects, among other intriguing properties. We have studied a 2DEG-forming multilayer of the form [6unit cells (u .c .) STO /3 u .c .of GTO ] 20 using a unique array of photoemission techniques including soft and hard x-ray excitation, soft x-ray angle-resolved photoemission, core-level spectroscopy, resonant excitation, and standing-wave effects, as well as theoretical calculations of the electronic structure at several levels and of the actual photoemission process. Standing-wave measurements below and above a strong resonance have been exploited as a powerful method for studying the 2DEG depth distribution. We have thus characterized the spatial and momentum properties of this 2DEG in detail, determining via depth-distribution measurements that it is spread throughout the 6 u.c. layer of STO and measuring the momentum dispersion of its states. The experimental results are supported in several ways by theory, leading to a much more complete picture of the nature of this 2DEG and suggesting that oxygen vacancies are not the origin of it. Similar multitechnique photoemission studies of such states at buried interfaces, combined with comparable theory, will be a very fruitful future approach for exploring and modifying the fascinating world of buried-interface physics and chemistry.

  14. Determination of nonylphenol isomers in landfill leachate and municipal wastewater using steam distillation extraction coupled with comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry

    Science.gov (United States)

    Zhang, Caixiang; Eganhouse, Robert P.; Pontolillo, James; Cozzarelli, Isabelle M.; Wang, Yanxin

    2012-01-01

    4-Nonylphenols (4-NPs) are known endocrine disruptors and by-products of the microbial degradation of nonylphenol polyethoxylate surfactants. One of the challenges to understanding the toxic effects of nonylphenols is the large number of isomers that may exist in environmental samples. In order to attribute toxic effects to specific compounds, a method is needed for the separation and quantitation of individual nonylphenol isomers. The pre-concentration methods of solvent sublimation, solid-phase extraction or liquid–liquid extraction prior to chromatographic analysis can be problematic because of co-extraction of thousands of compounds typically found in complex matrices such as municipal wastewater or landfill leachate. In the present study, steam distillation extraction (SDE) was found to be an effective pre-concentration method for extraction of 4-NPs from leachate and wastewater, and comprehensive two-dimensional gas chromatography (GC × GC) coupled with fast mass spectral data acquisition by time-of-flight mass spectrometry (ToFMS) enhanced the resolution and identification of 4-NP isomers. Concentrations of eight 4-NP isomers were determined in leachate from landfill cells of different age and wastewater influent and effluent samples. 4-NP isomers were about 3 times more abundant in leachate from the younger cell than the older one, whereas concentrations in wastewater effluent were either below detection limits or <1% of influent concentrations. 4-NP isomer distribution patterns were found to have been altered following release to the environment. This is believed to reflect isomer-specific degradation and accumulation of 4-NPs in the aquatic environment.

  15. Identifying unknown by-products in drinking water using comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry and in silico toxicity assessment.

    Science.gov (United States)

    Li, Chunmei; Wang, Donghong; Li, Na; Luo, Qian; Xu, Xiong; Wang, Zijian

    2016-11-01

    Improvements in extraction and detection technologies have increased our abilities to identify new disinfection by-products (DBPs) over the last 40 years. However, most previous studies combined DBP identification and measurement efforts with toxicology to address concerns on a few expected DBPs, making it difficult to better define the health risk from the individual DBPs. In this study, a nontargeted screening method involving comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry (GC × GC-qMS) combined with OECD QSAR Toolbox Ver. 3.2 was developed for identifying and prioritizing of volatile and semi-volatile DBPs in drinking water. The method was successfully applied to analyze DBPs formed during chlorination, chloramination or ozonation of the raw water. Over 500 compounds were tentatively identified in each sample, showing the superior performance of this analytical technique. A total of 170 volatile and semi-volatile DBPs representing fourteen chemical classes were then identified, according to the criteria that the DBP was presented in the duplicate treated samples. The genotoxicity and carcinogenicity of the DBPs were evaluated using Toolbox, and 58 DBPs were found to be actual or potential genotoxicants. The accuracy of the compound identification was determined by comparing 47 identified compounds with commercially available standards. About 90% (41 of the 47) of the compounds that were automatically identified using the library were correct. The results show that GC×GC-qMS coupled with a quantitative structure-activity relationship model is a powerful and fast nontargeted screening technique for compounds. The method and results provide us a new idea for identification and prioritization of DBPs.

  16. Separation of seventeen 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans and 12 dioxin-like polychlorinated biphenyls by comprehensive two-dimensional gas chromatography with electron-capture detection

    NARCIS (Netherlands)

    Korytar, P.; Danielsson, C.; Leonards, P.E.G.; Haglund, P.; Boer, de J.; Brinkman, U.A.Th.

    2004-01-01

    Comprehensive two-dimensional gas chromatography (GCxGC) with electron-capture detection (ECD) has been optimized for the separation of seventeen 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans and 12 dioxin-like polychlorinated biphenyls, with emphasis on the selection of th

  17. metAlignID: A high-throughout sofware tool set for automated detection of trace level contaminants in comprehensive LECO two-dimensional gas chromatography time-of-flight mass spectrometry data

    NARCIS (Netherlands)

    Lommen, A.; Kamp, van der H.J.; Kools, H.J.; Lee, van der M.K.; Weg, van der G.

    2012-01-01

    A new alternative data processing tool set, metAlignID, is developed for automated pre-processing and library-based identification and concentration estimation of target compounds after analysis by comprehensive two-dimensional gas chromatography with mass spectrometric detection. The tool set has b

  18. Solid phase extraction in combination with comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry for the detailed investigation of volatiles in South African red wines

    NARCIS (Netherlands)

    Weldegergis, B.T.; Crouch, A.M.; Górecki, T.; Villiers, de A.

    2011-01-01

    Comprehensive two-dimensional gas chromatography in combination with time-of-flight mass spectrometry (GC × GC–TOFMS) has been applied for the analysis of volatile compounds in three young South African red wines. In spite of the significant benefits offered by GC × GC–TOFMS for the separation and

  19. Two-dimensional heterostructures for energy storage

    Science.gov (United States)

    Pomerantseva, Ekaterina; Gogotsi, Yury

    2017-07-01

    Two-dimensional (2D) materials provide slit-shaped ion diffusion channels that enable fast movement of lithium and other ions. However, electronic conductivity, the number of intercalation sites, and stability during extended cycling are also crucial for building high-performance energy storage devices. While individual 2D materials, such as graphene, show some of the required properties, none of them can offer all properties needed to maximize energy density, power density, and cycle life. Here we argue that stacking different 2D materials into heterostructured architectures opens an opportunity to construct electrodes that would combine the advantages of the individual building blocks while eliminating the associated shortcomings. We discuss characteristics of common 2D materials and provide examples of 2D heterostructured electrodes that showed new phenomena leading to superior electrochemical performance. We also consider electrode fabrication approaches and finally outline future steps to create 2D heterostructured electrodes that could greatly expand current energy storage technologies.

  20. Extension of the two-dimensional mass channel cluster plot method to fast separations utilizing low thermal mass gas chromatography with time-of-flight mass spectrometry.

    Science.gov (United States)

    Fitz, Brian D; Synovec, Robert E

    2016-03-24

    Implementation of a data reduction and visualization method for use with high-speed gas chromatography and time-of-flight mass spectrometry (GC-TOFMS) is reported. The method, called the "2D m/z cluster method" facilitates analyte detection, deconvolution, and identification, by accurately measuring peak widths and retention times using a fast TOFMS sampling frequency (500 Hz). Characteristics and requirements for high speed GC are taken into consideration: fast separations with narrow peak widths and high peak capacity, rapid data collection rate, and effective peak deconvolution. Transitioning from standard GC (10-60+ minute separations) to fast GC (1-10 min separations) required consideration of how to properly analyze the data. This report validates use of the 2D m/z cluster method with newly developed GC technology that produces ultra-fast separations (∼1 min) with narrow analyte peak widths. Low thermal mass gas chromatography (LTM-GC) operated at a heating rate of 250 °C/min coupled to a LECO Pegasus III TOFMS analyzed a 115 component test mixture in 120 s with peak widths-at-base, wb (4σ), of 350 ms (average) to produce a separation with a high peak capacity, nc ∼ 340 (at unit resolution Rs = 1). The 2D m/z cluster method is shown to separate overlapped analytes to a limiting Rs ∼ 0.03, so the effective peak capacity was increased nearly 30-fold to nc ∼10,000 in the 120 s separation. The method, when coupled with LTM-GC-TOFMS, is demonstrated to provide unambiguous peak rank (i.e. the number of analytes per overlapped peak in the total ion current (TIC)), by visualizing locations of pure and chromatographically overlapped m/z. Hence, peak deconvolution and identification using MCR-ALS (multivariate curve resolution - alternating least squares) is demonstrated.

  1. Phase diagram of a two-dimensional liquid in GaAs/AlxGa1-xAs biased double quantum wells

    DEFF Research Database (Denmark)

    Timofeev, V. B.; Larionov, A. V.; Alessi, M. G.;

    2000-01-01

    densities, P, and temperatures, T. For increasing P or decreasing T, a sharp transition from two gases of photoexcited electrons and holes, spatially separated and confined in the two wells, to two two-dimensional (2D) liquids has been observed. The gas-to-2D-liquid transition is evidenced by a strong...

  2. Two-dimensional x-ray diffraction

    CERN Document Server

    He, Bob B

    2009-01-01

    Written by one of the pioneers of 2D X-Ray Diffraction, this useful guide covers the fundamentals, experimental methods and applications of two-dimensional x-ray diffraction, including geometry convention, x-ray source and optics, two-dimensional detectors, diffraction data interpretation, and configurations for various applications, such as phase identification, texture, stress, microstructure analysis, crystallinity, thin film analysis and combinatorial screening. Experimental examples in materials research, pharmaceuticals, and forensics are also given. This presents a key resource to resea

  3. Two-dimensional optical spectroscopy

    CERN Document Server

    Cho, Minhaeng

    2009-01-01

    Discusses the principles and applications of two-dimensional vibrational and optical spectroscopy techniques. This book provides an account of basic theory required for an understanding of two-dimensional vibrational and electronic spectroscopy.

  4. Evaluation of comprehensive two-dimensional gas chromatography with accurate mass time-of-flight mass spectrometry for the metabolic profiling of plant-fungus interaction in Aquilaria malaccensis.

    Science.gov (United States)

    Wong, Yong Foo; Chin, Sung-Tong; Perlmutter, Patrick; Marriott, Philip J

    2015-03-27

    To explore the possible obligate interactions between the phytopathogenic fungus and Aquilaria malaccensis which result in generation of a complex array of secondary metabolites, we describe a comprehensive two-dimensional gas chromatography (GC × GC) method, coupled to accurate mass time-of-flight mass spectrometry (TOFMS) for the untargeted and comprehensive metabolic profiling of essential oils from naturally infected A. malaccensis trees. A polar/non-polar column configuration was employed, offering an improved separation pattern of components when compared to other column sets. Four different grades of the oils displayed quite different metabolic patterns, suggesting the evolution of a signalling relationship between the host tree (emergence of various phytoalexins) and fungi (activation of biotransformation). In total, ca. 550 peaks/metabolites were detected, of which tentative identification of 155 of these compounds was reported, representing between 20.1% and 53.0% of the total ion count. These are distributed over the chemical families of monoterpenic and sesquiterpenic hydrocarbons, oxygenated monoterpenes and sesquiterpenes (comprised of ketone, aldehyde, oxide, alcohol, lactone, keto-alcohol and diol), norterpenoids, diterpenoids, short chain glycols, carboxylic acids and others. The large number of metabolites detected, combined with the ease with which they are located in the 2D separation space, emphasises the importance of a comprehensive analytical approach for the phytochemical analysis of plant metabolomes. Furthermore, the potential of this methodology in grading agarwood oils by comparing the obtained metabolic profiles (pattern recognition for unique metabolite chemical families) is discussed. The phytocomplexity of the agarwood oils signified the production of a multitude of plant-fungus mediated secondary metabolites as chemical signals for natural ecological communication. To the best of our knowledge, this is the most complete

  5. Two-Dimensional Electrons.

    Science.gov (United States)

    2014-09-26

    Isihara and Y. Nalane, Elementary Excitations and Energy Dispersion in TTF-TCNQ;Proc. Internat. Conf. on Phys. and Chem. of Low-Dimen. Syn. Conductors ...Abano Terme, Molec. Crys. Liq. Crys. 120, 85 (1984). One-dimensiona4 conductors such as TTF-TCNQ are attracting considerable attention for their...A. Isihara and Y. Nakane; Magnetoconductivity of 2D Conductors ; Proc. Internat. Conf. on Phys. and Chem. of Low-Dimen. Syn. Conductors , Abano Terme

  6. Finite-size scaling in a 2D disordered electron gas with spectral nodes.

    Science.gov (United States)

    Sinner, Andreas; Ziegler, Klaus

    2016-08-03

    We study the DC conductivity of a weakly disordered 2D electron gas with two bands and spectral nodes, employing the field theoretical version of the Kubo-Greenwood conductivity formula. Disorder scattering is treated within the standard perturbation theory by summing up ladder and maximally crossed diagrams. The emergent gapless (diffusion) modes determine the behavior of the conductivity on large scales. We find a finite conductivity with an intermediate logarithmic finite-size scaling towards smaller conductivities but do not obtain the logarithmic divergence of the weak-localization approach. Our results agree with the experimentally observed logarithmic scaling of the conductivity in graphene with the formation of a plateau near [Formula: see text].

  7. Conductivity of disordered 2d binodal Dirac electron gas: Effect of the internode scattering

    CERN Document Server

    Sinner, Andreas

    2016-01-01

    We study the dc conductivity of a weakly disordered 2d Dirac electron gas with two bands and two spectral nodes, employing a field theoretical version of the Kubo--Greenwood conductivity formula. In this paper we are concerned with the question how the internode scattering affects the conductivity. We use and compare two established techniques for treating the disorder scattering: The perturbation theory, there ladder and maximally crossed diagrams are summed up, and the functional integral approach. Both turn out to be entirely equivalent. For a large number of random potential configurations we have found only two different conductivity scenarios. Both scenarios appear independently of whether the disorder does or does not create the internode scattering. In particular we do not confirm the conjecture that the internode scattering tends to Anderson localization.

  8. Finite-size scaling in a 2D disordered electron gas with spectral nodes

    Science.gov (United States)

    Sinner, Andreas; Ziegler, Klaus

    2016-08-01

    We study the DC conductivity of a weakly disordered 2D electron gas with two bands and spectral nodes, employing the field theoretical version of the Kubo-Greenwood conductivity formula. Disorder scattering is treated within the standard perturbation theory by summing up ladder and maximally crossed diagrams. The emergent gapless (diffusion) modes determine the behavior of the conductivity on large scales. We find a finite conductivity with an intermediate logarithmic finite-size scaling towards smaller conductivities but do not obtain the logarithmic divergence of the weak-localization approach. Our results agree with the experimentally observed logarithmic scaling of the conductivity in graphene with the formation of a plateau near {{e}2}/π h .

  9. Predicting percent composition of blends of biodiesel and conventional diesel using gas chromatography-mass spectrometry, comprehensive two-dimensional gas chromatography-mass spectrometry, and partial least squares analysis.

    Science.gov (United States)

    Pierce, Karisa M; Schale, Stephen P

    2011-01-30

    The percent composition of blends of biodiesel and conventional diesel from a variety of retail sources were modeled and predicted using partial least squares (PLS) analysis applied to gas chromatography-total-ion-current mass spectrometry (GC-TIC), gas chromatography-mass spectrometry (GC-MS), comprehensive two-dimensional gas chromatography-total-ion-current mass spectrometry (GCxGC-TIC) and comprehensive two-dimensional gas chromatography-mass spectrometry (GCxGC-MS) separations of the blends. In all four cases, the PLS predictions for a test set of chromatograms were plotted versus the actual blend percent composition. The GC-TIC plot produced a best-fit line with slope=0.773 and y-intercept=2.89, and the average percent error of prediction was 12.0%. The GC-MS plot produced a best-fit line with slope=0.864 and y-intercept=1.72, and the average percent error of prediction was improved to 6.89%. The GCxGC-TIC plot produced a best-fit line with slope=0.983 and y-intercept=0.680, and the average percent error was slightly improved to 6.16%. The GCxGC-MS plot produced a best-fit line with slope=0.980 and y-intercept=0.620, and the average percent error was 6.12%. The GCxGC models performed best presumably due to the multidimensional advantage of higher dimensional instrumentation providing more chemical selectivity. All the PLS models used 3 latent variables. The chemical components that differentiate the blend percent compositions are reported. Copyright © 2010 Elsevier B.V. All rights reserved.

  10. Analysis of directional dependence of the two-dimensional array of detectors 2D array seven 29 implications in the planning system; Analisis de la dependencia direcccional de la matriz bidimensional de detectores 2D array seven29. Implicaciones en el sistema de planificacion

    Energy Technology Data Exchange (ETDEWEB)

    Mora Melendez, R.; Seguro Fernandez, A.; Iborra Oquendo, M.; Urena Llinares, A.

    2013-07-01

    The main objective of our study is to find correction factors dependent on the 2D array incidence angles, and to give account of the phenomenon, allowing the Planner to faithfully reproduce data and curves measured experimentally. (Author)

  11. Validation of automated Library-Based Qualitative Screening of Pesticides by Comprehensive Two-Dimensional Gas Chromatography/Time-of-Flight Mass Spectrometry

    NARCIS (Netherlands)

    Mol, J.G.J.; Kamp, van der H.J.; Weg, van der G.; Lee, van der M.K.; Punt, A.M.; Rijk, de T.C.

    2011-01-01

    A method for automated detection and reporting of pesticides in plant materials based on comprehensive two-dimensional GC/time-of-flight MS with library-based detection by software has been developed and validated. Optimum settings for detection parameters such as spectral match threshold and first

  12. Comparative analysis between two-dimensional (2D) and three-dimensional (3D) MRI acquisitions - clinical applications for the evaluation of the knees in juvenile rheumatoid arthritis (JRA); Analise comparativa entre aquisicao tri (3D) e bidimensional (2D) em ressonancia magnetica - aplicabilidade clinica em joelhos em artrite reumatoide juvenil (ARJ)

    Energy Technology Data Exchange (ETDEWEB)

    Doria, Andre S. [Hospital das Clinicas, Sao Paulo, SP (Brazil). Inst. de Radiologia; Rebelo, Marina de Sa [Hospital das Clinicas, Sao Paulo, SP (Brazil). Instituto do Coracao. Servico de Informatica; Castro, Claudio Campi de [Hospital das Clinicas, Sao Paulo, SP (Brazil). Instituto do Coracao. Servico de Ressonancia Magnetica] [and others

    2000-06-01

    In this cross-sectional study in patients with juvenile rheumatoid arthritis the authors compare two-dimensional evaluation of the maximum synovial diameter on post-contrast axial T1-weighted SE (spin-echo) sequences with volumetric (three-dimensional assessment) on post-contrast axial T1-weighted SPIR (spectral presaturation with inversion recovery) SE sequences. With the aim of determining their cost-effectiveness these two methods of assessment were compared to clinical and laboratorial parameters, as well as the presence of synovial enhancement seen on magnetic resonance imaging. (author)

  13. Two-dimensional effects in nonlinear Kronig-Penney models

    DEFF Research Database (Denmark)

    Gaididei, Yuri Borisovich; Christiansen, Peter Leth; Rasmussen, Kim

    1997-01-01

    An analysis of two-dimensional (2D) effects in the nonlinear Kronig-Penney model is presented. We establish an effective one-dimensional description of the 2D effects, resulting in a set of pseudodifferential equations. The stationary states of the 2D system and their stability is studied...

  14. A two-dimensional Dirac fermion microscope

    Science.gov (United States)

    Bøggild, Peter; Caridad, José M.; Stampfer, Christoph; Calogero, Gaetano; Papior, Nick Rübner; Brandbyge, Mads

    2017-06-01

    The electron microscope has been a powerful, highly versatile workhorse in the fields of material and surface science, micro and nanotechnology, biology and geology, for nearly 80 years. The advent of two-dimensional materials opens new possibilities for realizing an analogy to electron microscopy in the solid state. Here we provide a perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons. We use semiclassical simulations to propose concrete architectures and design rules of 2D electron guns, deflectors, tunable lenses and various detectors. The simulations show how simple objects can be imaged with well-controlled and collimated in-plane beams consisting of relativistic charge carriers. Finally, we discuss the potential of such microscopes for investigating edges, terminations and defects, as well as interfaces, including external nanoscale structures such as adsorbed molecules, nanoparticles or quantum dots.

  15. A two-dimensional Dirac fermion microscope.

    Science.gov (United States)

    Bøggild, Peter; Caridad, José M; Stampfer, Christoph; Calogero, Gaetano; Papior, Nick Rübner; Brandbyge, Mads

    2017-06-09

    The electron microscope has been a powerful, highly versatile workhorse in the fields of material and surface science, micro and nanotechnology, biology and geology, for nearly 80 years. The advent of two-dimensional materials opens new possibilities for realizing an analogy to electron microscopy in the solid state. Here we provide a perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons. We use semiclassical simulations to propose concrete architectures and design rules of 2D electron guns, deflectors, tunable lenses and various detectors. The simulations show how simple objects can be imaged with well-controlled and collimated in-plane beams consisting of relativistic charge carriers. Finally, we discuss the potential of such microscopes for investigating edges, terminations and defects, as well as interfaces, including external nanoscale structures such as adsorbed molecules, nanoparticles or quantum dots.

  16. An Excel(®)-based visualization tool of 2-D soil gas concentration profiles in petroleum vapor intrusion.

    Science.gov (United States)

    Verginelli, Iason; Yao, Yijun; Suuberg, Eric M

    2016-01-01

    In this study we present a petroleum vapor intrusion tool implemented in Microsoft(®) Excel(®) using Visual Basic for Applications (VBA) and integrated within a graphical interface. The latter helps users easily visualize two-dimensional soil gas concentration profiles and indoor concentrations as a function of site-specific conditions such as source strength and depth, biodegradation reaction rate constant, soil characteristics and building features. This tool is based on a two-dimensional explicit analytical model that combines steady-state diffusion-dominated vapor transport in a homogeneous soil with a piecewise first-order aerobic biodegradation model, in which rate is limited by oxygen availability. As recommended in the recently released United States Environmental Protection Agency's final Petroleum Vapor Intrusion guidance, a sensitivity analysis and a simplified Monte Carlo uncertainty analysis are also included in the spreadsheet.

  17. Performance of a Micro-Strip Gas Chamber for event wise, high rate thermal neutron detection with accurate 2D position determination

    Science.gov (United States)

    Mindur, B.; Alimov, S.; Fiutowski, T.; Schulz, C.; Wilpert, T.

    2014-12-01

    A two-dimensional (2D) position sensitive detector for neutron scattering applications based on low-pressure gas amplification and micro-strip technology was built and tested with an innovative readout electronics and data acquisition system. This detector contains a thin solid neutron converter and was developed for time- and thus wavelength-resolved neutron detection in single-event counting mode, which improves the image contrast in comparison with integrating detectors. The prototype detector of a Micro-Strip Gas Chamber (MSGC) was built with a solid natGd/CsI thermal neutron converter for spatial resolutions of about 100 μm and counting rates up to 107 neutrons/s. For attaining very high spatial resolutions and counting rates via micro-strip readout with centre-of-gravity evaluation of the signal amplitude distributions, a fast, channel-wise, self-triggering ASIC was developed. The front-end chips (MSGCROCs), which are very first signal processing components, are read out into powerful ADC-FPGA boards for on-line data processing and thereafter via Gigabit Ethernet link into the data receiving PC. The workstation PC is controlled by a modular, high performance dedicated software suite. Such a fast and accurate system is crucial for efficient radiography/tomography, diffraction or imaging applications based on high flux thermal neutron beam. In this paper a brief description of the detector concept with its operation principles, readout electronics requirements and design together with the signals processing stages performed in hardware and software are presented. In more detail the neutron test beam conditions and measurement results are reported. The focus of this paper is on the system integration, two dimensional spatial resolution, the time resolution of the readout system and the imaging capabilities of the overall setup. The detection efficiency of the detector prototype is estimated as well.

  18. Mobility anisotropy of two-dimensional semiconductors

    CERN Document Server

    Lang, Haifeng; Liu, Zhirong

    2016-01-01

    The carrier mobility of anisotropic two-dimensional (2D) semiconductors under longitudinal acoustic (LA) phonon scattering was theoretically studied with the deformation potential theory. Based on Boltzmann equation with relaxation time approximation, an analytic formula of intrinsic anisotropic mobility was deduced, which shows that the influence of effective mass to the mobility anisotropy is larger than that of deformation potential constant and elastic modulus. Parameters were collected for various anisotropic 2D materials (black phosphorus, Hittorf's phosphorus, BC$_2$N, MXene, TiS$_3$, GeCH$_3$) to calculate their mobility anisotropy. It was revealed that the anisotropic ratio was overestimated in the past.

  19. Two-dimensional microstrip detector for neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Oed, A. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1997-04-01

    Because of their robust design, gas microstrip detectors, which were developed at ILL, can be assembled relatively quickly, provided the prefabricated components are available. At the beginning of 1996, orders were received for the construction of three two-dimensional neutron detectors. These detectors have been completed. The detectors are outlined below. (author). 2 refs.

  20. Intracellular ROS mediates gas plasma-facilitated cellular transfection in 2D and 3D cultures

    Science.gov (United States)

    Xu, Dehui; Wang, Biqing; Xu, Yujing; Chen, Zeyu; Cui, Qinjie; Yang, Yanjie; Chen, Hailan; Kong, Michael G.

    2016-01-01

    This study reports the potential of cold atmospheric plasma (CAP) as a versatile tool for delivering oligonucleotides into mammalian cells. Compared to lipofection and electroporation methods, plasma transfection showed a better uptake efficiency and less cell death in the transfection of oligonucleotides. We demonstrated that the level of extracellular aqueous reactive oxygen species (ROS) produced by gas plasma is correlated with the uptake efficiency and that this is achieved through an increase of intracellular ROS levels and the resulting increase in cell membrane permeability. This finding was supported by the use of ROS scavengers, which reduced CAP-based uptake efficiency. In addition, we found that cold atmospheric plasma could transfer oligonucleotides such as siRNA and miRNA into cells even in 3D cultures, thus suggesting the potential for unique applications of CAP beyond those provided by standard transfection techniques. Together, our results suggest that cold plasma might provide an efficient technique for the delivery of siRNA and miRNA in 2D and 3D culture models. PMID:27296089

  1. Rise characteristics of gas bubbles in a 2D rectangular column: VOF simulations vs experiments

    Energy Technology Data Exchange (ETDEWEB)

    Krishna, R.; Baten, J.M. van

    1999-10-01

    About five centuries ago, Leonardo da Vinci described the sinuous motion of gas bubbles rising in water. The authors have attempted to simulate the rise trajectories of bubbles of 4, 5, 7, 8, 9, 12, and 20 mm in diameter rising in a 2D rectangular column filled with water. The simulations were carried out using the volume-of-fluid (VOF) technique developed by Hirt and Nichols (J. Computational Physics, 39, 201--225 (1981)). To solve the Navier-Stokes equations of motion the authors used a commercial solver, CFX 4.1c of AEA Technology, UK. They developed their own bubble-tracking algorithm to capture sinuous bubble motions. The 4 and 5 mm bubbles show large lateral motions observed by Da Vinci. The 7, 8 and 9 mm bubble behave like jellyfish. The 12 mm bubble flaps its wings like a bird. The extent of lateral motion of the bubbles decreases with increasing bubble size. Bubbles larger than 20 mm in size assume a spherical cap form and simulations of the rise characteristics match experiments exactly. VOF simulations are powerful tools for a priori determination of the morphology and rise characteristics of bubbles rising in a liquid. Bubble-bubble interactions are also properly modeled by the VOF technique.

  2. Two-Dimensional Plasmonics in Massive and Massless Electron Gases

    Science.gov (United States)

    Yoon, Hosang

    Plasmonic waves in solid-state are caused by collective oscillation of mobile charges inside or at the surface of conductors. In particular, surface plasmonic waves propagating at the skin of metals have recently attracted interest, as they reduce the wavelength of electromagnetic waves coupled to them by up to ˜10 times, allowing one to create miniaturized wave devices at optical frequencies. In contrast, plasmonic waves on two-dimensional (2D) conductors appear at much lower infrared and THz-GHz frequencies, near or in the electronics regime, and can achieve far stronger wavelength reduction factor reaching well above 100. In this thesis, we study the unique machinery of 2D plasmonic waves behind this ultra-subwavelength confinement and explore how it can be used to create various interesting devices. To this end, we first develop a physically intuitive theoretical formulation of 2D plasmonic waves, whose two main components---the Coulomb restoration force and inertia of the collectively oscillating charges---are combined into a transmission-line-like model. We then use this formulation to create various ultra-subwavelength 2D plasmonic devices. For the 2D conductor, we first choose GaAs/AlGaAs heterostructure---a 2D electron gas consisting of massive (m* > 0) electrons---demonstrating plasmonic bandgap crystals, interferometers, and negatively refracting metamaterials. We then examine a 2D plasmonic device based on graphene, a 2D electron gas consisting of effectively massless (m* = 0) electrons. We theoretically show and experimentally demonstrate that the massless electrons in graphene can surprisingly exhibit a collective mass when subjected to a collective excitation, providing the inertia that is essential for the propagation of 2D plasmonic waves. Lastly, we theoretically investigate the thermal current fluctuation behaviors in massive and massless electron gases. While seemingly unrelated on first sight, we show that the thermal current fluctuation is

  3. Fabrication of Novel 2D NiO Nanosheet Branched on 1D-ZnO Nanorod Arrays for Gas Sensor Application

    Directory of Open Access Journals (Sweden)

    Le Thuy Hoa

    2014-01-01

    Full Text Available Fabrication of 3D structures composed of 1D n-type ZnO nanorods (NRs and 2D p-type NiO nanosheets (NSs by a low-cost, low-temperature, and large-area scalable hydrothermal process and its use in highly sensitive NO2 gas sensors were studied. The p-n heterojunctions formed by NiO-ZnO interfaces as well as large area two-dimensional NiO NSs themselves increased the adsorption of NO2. Moreover, the charge transfer between NiO and ZnO enhanced the responsivity and sensitivity of NO2 sensing even at a concentration of 1 ppm. The 30-min NiO NS growth on ZnO NRs in the hybrid sensor showed the highest sensitivity due to the formation of optimum p-n heterojunctions between ZnO NRs and NiO NSs for gas adsorption and carrier transport. Low responsivity toward reducing gases was also observed.

  4. Verification of electrical spin injection into InGaAs two-dimensional electron gas from CoFe electrode by four-terminal non-local geometry

    Science.gov (United States)

    Hidaka, S.; Kondo, T.; Akabori, M.; Yamada, S.

    2013-12-01

    We performed electrical spin injection into In0.75Ga0.25As two-dimensional electron gases from Co0.8Fe0.2 electrodes by four-terminal non-local spin-valve (NLSV) measurement. We observed clear SV signals in NL resistance at 1.5 K. From the electrode spacing dependence of the signals, we estimated spin diffusion length and spin polarization to be ˜5.1 μm and ˜5.7 %, respectively. These are larger than those reported in similar systems.

  5. Verification of electrical spin injection into InGaAs two-dimensional electron gas from CoFe electrode by four-terminal non-local geometry

    Energy Technology Data Exchange (ETDEWEB)

    Hidaka, S.; Kondo, T.; Akabori, M.; Yamada, S. [Center for Nano Materials and Technology (CNMT), Japan Advanced Institute of Science and Technology (JAIST), Asahidai, Nomi, Ishikawa 923-1292 (Japan)

    2013-12-04

    We performed electrical spin injection into In{sub 0.75}Ga{sub 0.25}As two-dimensional electron gases from Co{sub 0.8}Fe{sub 0.2} electrodes by four-terminal non-local spin-valve (NLSV) measurement. We observed clear SV signals in NL resistance at 1.5 K. From the electrode spacing dependence of the signals, we estimated spin diffusion length and spin polarization to be ∼5.1 μm and ∼5.7 %, respectively. These are larger than those reported in similar systems.

  6. 2D numerical simulation of gas flow interaction with a solid wall by regularized Grad's set of equations

    Science.gov (United States)

    Timokhin, M. Yu.; Ivanov, I. E.; Kryukov, I. A.

    2012-11-01

    This study is devoted to the two-dimensional numerical simulation of gas flow in the transition regime with solid wall interaction. The regularized 13-moment Grad's set of equations (R13) [1,2] was chosen as a mathematical model. A variant of explicit high order Godunov-type scheme with linear flow parameter reconstruction is used for the numerical solution of this set of equations. Numerical method for wall boundary conditions is based on Newton's iterative method suggested here. Couette and Poiseuille flows and lid-driven cavity flow were solved as test examples with this numerical scheme.

  7. Nonlocal bottleneck effect in two-dimensional turbulence

    CERN Document Server

    Biskamp, D; Schwarz, E

    1998-01-01

    The bottleneck pileup in the energy spectrum is investigated for several two-dimensional (2D) turbulence systems by numerical simulation using high-order diffusion terms to amplify the effect, which is weak for normal diffusion. For 2D magnetohydrodynamic (MHD) turbulence, 2D electron MHD (EMHD) turbulence and 2D thermal convection, which all exhibit direct energy cascades, a nonlocal behavior is found resulting in a logarithmic enhancement of the spectrum.

  8. Formation of nitric oxide in an industrial burner measured by 2-D laser induced fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, A.; Bombach, R.; Kaeppeli, B. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    We have performed two-dimensional Laser Induced Fluorescence (2-D LIF) measurements of nitric oxide and hydroxyl radical distributions in an industrial burner at atmospheric pressure. The relative 2-D LIF data of NO were set to an absolute scale by calibration with probe sampling combined with gas analysis. (author) 3 figs., 7 refs.

  9. c2d Spitzer IRS spectra of embedded low-mass young stars : gas-phase emission lines

    NARCIS (Netherlands)

    Lahuis, F.; van Dishoeck, E. F.; Jorgensen, J. K.; Blake, G. A.; Evans, N. J.

    2010-01-01

    Context. A survey of mid-infrared gas-phase emission lines of H(2), H(2)O and various atoms toward a sample of 43 embedded low-mass young stars in nearby star-forming regions is presented. The sources are selected from the Spitzer "Cores to Disks" (c2d) legacy program. Aims. The environment of embed

  10. Two-Dimensional Mesoscale-Ordered Conducting Polymers

    NARCIS (Netherlands)

    Liu, Shaohua; Zhang, Jian; Dong, Renhao; Gordiichuk, Pavlo; Zhang, Tao; Zhuang, Xiaodong; Mai, Yiyong; Liu, Feng; Herrmann, Andreas; Feng, Xinliang

    2016-01-01

    Despite the availability of numerous two-dimensional (2D) materials with structural ordering at the atomic or molecular level, direct construction of mesoscale-ordered superstructures within a 2D monolayer remains an enormous challenge. Here, we report the synergic manipulation of two types of assem

  11. Two-Dimensional Mesoscale-Ordered Conducting Polymers

    NARCIS (Netherlands)

    Liu, Shaohua; Zhang, Jian; Dong, Renhao; Gordiichuk, Pavlo; Zhang, Tao; Zhuang, Xiaodong; Mai, Yiyong; Liu, Feng; Herrmann, Andreas; Feng, Xinliang

    2016-01-01

    Despite the availability of numerous two-dimensional (2D) materials with structural ordering at the atomic or molecular level, direct construction of mesoscale-ordered superstructures within a 2D monolayer remains an enormous challenge. Here, we report the synergic manipulation of two types of

  12. TreePM Method for Two-Dimensional Cosmological Simulations

    Indian Academy of Sciences (India)

    Suryadeep Ray

    2004-09-01

    We describe the two-dimensional TreePM method in this paper. The 2d TreePM code is an accurate and efficient technique to carry out large two-dimensional N-body simulations in cosmology. This hybrid code combines the 2d Barnes and Hut Tree method and the 2d Particle–Mesh method. We describe the splitting of force between the PM and the Tree parts. We also estimate error in force for a realistic configuration. Finally, we discuss some tests of the code.

  13. Spin-polarized two-dimensional electron gas at GdTi O3/SrTi O3 interfaces: Insight from first-principles calculations

    Science.gov (United States)

    Betancourt, J.; Paudel, T. R.; Tsymbal, E. Y.; Velev, J. P.

    2017-07-01

    Two-dimensional electron gases (2DEGs) at oxide interfaces have been a topic of intensive research due to their high carrier mobility and strong confinement. Additionally, strong correlations in the oxide materials can give rise to new and interesting physics, such as magnetism and metal-insulator transitions at the interface. Using first-principles calculations based on density functional theory, we demonstrate the presence of a highly spin-polarized 2DEG at the interface between the Mott insulator GdTi O3 and a band insulator SrTi O3 . The strong correlations in the dopant cause ferromagnetic alignment of the interface Ti atoms and result in a fully spin-polarized 2DEG. The 2DEG consists of two types of carriers distinguished by their orbital character. The majority of the interface charge is strongly localized on the Ti dx y orbitals at the interface and a smaller fraction resides on the delocalized Ti dx z ,y z states.

  14. Aroma-impact compounds in dried spice as a quality index using solid phase microextraction with olfactometry and comprehensive two-dimensional gas chromatography.

    Science.gov (United States)

    Maikhunthod, Bussayarat; Marriott, Philip J

    2013-12-15

    A systematic experimental procedure is used to identify the aroma-impact compounds, leading to a shelf quality index based on head space solid-phase microextraction. Dried (ground) fennel seeds, having shelf life of 6 months (0.5Y) and 5 years (5Y), were used as a spice model for assessment of comparative aroma quality. Aroma-impact odorants were analysed by GC-olfactometry (GC-O) in parallel with comprehensive two-dimensional GC-flame ionisation detection (GC×GC-FID) using a polar/non-polar phase combination for the GC×GC column set. Tentative identification of aroma-impact odorants involved correlating data from the GC-O/FID system with GC×GC-time-of-flight mass spectrometry analysis by means of retention indices. Major compounds responsible for aroma perception were limonene, 1,8-cineole, terpinen-4-ol, estragole and trans-anethole, and showed an average decrease of 30-50% NIF from 0.5Y to 5Y. Monoterpenes which represent 'freshness', e.g. β-pinene and β-myrcene, exhibited identifiable aroma-impact only for the 0.5Y product. Sesquiterpenes and sesquiterpene oxides are suggested as an aging index, being present in increased amounts in 5Y. p-Anisaldehyde odour intensity for both samples remained the same (aroma perception sweet creamy, floral odour and Chinese seasoning powder).

  15. TWO-DIMENSIONAL MAPPING OF YOUNG STARS IN THE INNER 180 pc OF NGC 1068: CORRELATION WITH MOLECULAR GAS RING AND STELLAR KINEMATICS

    Energy Technology Data Exchange (ETDEWEB)

    Storchi-Bergmann, Thaisa; Riffel, Rogerio; Vale, Tiberio Borges [Departamento de Astronomia, Universidade Federal do Rio Grande do Sul, IF, CP 15051, 91501-970 Porto Alegre, RS (Brazil); Riffel, Rogemar A.; Diniz, Marlon R. [Departamento de Fisica, Centro de Ciencias Naturais e Exatas, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS (Brazil); McGregor, Peter J., E-mail: thaisa@ufrgs.br [Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston Creek, ACT 2611 (Australia)

    2012-08-20

    We report the first two-dimensional mapping of the stellar population and non-stellar continua within the inner 180 pc (radius) of NGC 1068 at a spatial resolution of 8 pc, using integral field spectroscopy in the near-infrared. We have applied the technique of spectral synthesis to data obtained with the instrument NIFS and the adaptive optics module ALTAIR at the Gemini North Telescope. Two episodes of recent star formation are found to dominate the stellar population contribution: the first occurred 300 Myr ago, extending over most of the nuclear region; the second occurred just 30 Myr ago, in a ring-like structure at Almost-Equal-To 100 pc from the nucleus, where it is coincident with an expanding ring of H{sub 2} emission. Inside the ring, where a decrease in the stellar velocity dispersion is observed, the stellar population is dominated by the 300 Myr age component. In the inner 35 pc, the oldest age component (age {>=} 2 Gyr) dominates the mass, while the flux is dominated by blackbody components with temperatures in the range 700 K {<=} T {<=} 800 K which we attribute to the dusty torus. We also find some contribution from blackbody and power-law components beyond the nucleus which we attribute to dust emission and scattered light.

  16. Qualitative characteristics and comparison of volatile fraction of vodkas made from different botanical materials by comprehensive two-dimensional gas chromatography and the electronic nose based on the technology of ultra-fast gas chromatography.

    Science.gov (United States)

    Wiśniewska, Paulina; Śliwińska, Magdalena; Dymerski, Tomasz; Wardencki, Waldemar; Namieśnik, Jacek

    2017-03-01

    Vodka is a spirit-based beverage made from ethyl alcohol of agricultural origin. At present, increasingly more vodka brands have labels that specify the botanical origin of the product. Until now, the techniques for distinguishing between vodkas of different botanical origin have been costly, time-consuming and insufficient for making a distinction between vodka produced from similar raw materials. Therefore, it is of utmost importance to find a fast and relatively inexpensive technique for conducting such tests. In the present study, we employed comprehensive two-dimensional gas chromatography (GC×GC) and an electronic nose based on the technology of ultra-fast GC with chemometric methods such as partial least square discriminant analysis, discriminant function analysis and soft independent modeling of class analogy. Both techniques allow a distinction between the vodkas produced from different raw materials. In the case of GC×GC, the differences between vodkas were more noticeable than in the analysis by electronic nose; however, the electronic nose allowed the significantly faster analysis of vodkas. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  17. Theory of two-dimensional transformations

    OpenAIRE

    Kanayama, Yutaka J.; Krahn, Gary W.

    1998-01-01

    The article of record may be found at http://dx.doi.org/10.1109/70.720359 Robotics and Automation, IEEE Transactions on This paper proposes a new "heterogeneous" two-dimensional (2D) transformation group ___ to solve motion analysis/planning problems in robotics. In this theory, we use a 3×1 matrix to represent a transformation as opposed to a 3×3 matrix in the homogeneous formulation. First, this theory is as capable as the homogeneous theory, Because of the minimal size, its implement...

  18. Chemical Gated Field Effect Transistor by Hybrid Integration of One-Dimensional Silicon Nanowire and Two-Dimensional Tin Oxide Thin Film for Low Power Gas Sensor.

    Science.gov (United States)

    Han, Jin-Woo; Rim, Taiuk; Baek, Chang-Ki; Meyyappan, M

    2015-09-30

    Gas sensors based on metal-oxide-semiconductor transistor with the polysilicon gate replaced by a gas sensitive thin film have been around for over 50 years. These are not suitable for the emerging mobile and wearable sensor platforms due to operating voltages and powers far exceeding the supply capability of batteries. Here we present a novel approach to decouple the chemically sensitive region from the conducting channel for reducing the drive voltage and increasing reliability. This chemically gated field effect transistor uses silicon nanowire for the current conduction channel with a tin oxide film on top of the nanowire serving as the gas sensitive medium. The potential change induced by the molecular adsorption and desorption allows the electrically floating tin oxide film to gate the silicon channel. As the device is designed to be normally off, the power is consumed only during the gas sensing event. This feature is attractive for the battery operated sensor and wearable electronics. In addition, the decoupling of the chemical reaction and the current conduction regions allows the gas sensitive material to be free from electrical stress, thus increasing reliability. The device shows excellent gas sensitivity to the tested analytes relative to conventional metal oxide transistors and resistive sensors.

  19. Novel analytical methods for flame retardants and plasticizers based on gas chromatography, comprehensive two-dimensional gas chromatography, and direct probe coupled to atmospheric pressure chemical ionization-high resolution time-of-flight-mass spectrometry.

    Science.gov (United States)

    Ballesteros-Gómez, Ana; de Boer, Jacob; Leonards, Pim E G

    2013-10-15

    In this study, we assess the applicability of different analytical techniques, namely, direct probe (DP), gas chromatography (GC), and comprehensive two-dimensional gas chromatography (GC × GC) coupled to atmospheric pressure chemical ionization (APCI) with a high resolution (HR)-time-of-flight (TOF)-mass spectrometry (MS) for the analysis of flame retardants and plasticizers in electronic waste and car interiors. APCI-HRTOFMS is a combination scarcely exploited yet with GC or with a direct probe for screening purposes and to the best of our knowledge, never with GC × GC to provide comprehensive information. Because of the increasing number of flame retardants and questions about their environmental fate, there is a need for the development of wider target and untargeted screening techniques to assess human exposure to these compounds. With the use of the APCI source, we took the advantage of using a soft ionization technique that provides mainly molecular ions, in addition to the accuracy of HRMS for identification. The direct probe provided a very easy and inexpensive method for the identification of flame retardants without any sample preparation. This technique seems extremely useful for the screening of solid materials such as electrical devices, electronics and other waste. GC-APCI-HRTOF-MS appeared to be more sensitive compared to liquid chromatography (LC)-APCI/atmospheric pressure photoionization (APPI)-HRTOF-MS for a wider range of flame retardants with absolute detection limits in the range of 0.5-25 pg. A variety of tri- to decabromodiphenyl ethers, phosphorus flame retardants and new flame retardants were found in the samples at levels from microgram per gram to milligram per gram levels.

  20. Predicting Two-Dimensional Silicon Carbide Monolayers.

    Science.gov (United States)

    Shi, Zhiming; Zhang, Zhuhua; Kutana, Alex; Yakobson, Boris I

    2015-10-27

    Intrinsic semimetallicity of graphene and silicene largely limits their applications in functional devices. Mixing carbon and silicon atoms to form two-dimensional (2D) silicon carbide (SixC1-x) sheets is promising to overcome this issue. Using first-principles calculations combined with the cluster expansion method, we perform a comprehensive study on the thermodynamic stability and electronic properties of 2D SixC1-x monolayers with 0 ≤ x ≤ 1. Upon varying the silicon concentration, the 2D SixC1-x presents two distinct structural phases, a homogeneous phase with well dispersed Si (or C) atoms and an in-plane hybrid phase rich in SiC domains. While the in-plane hybrid structure shows uniform semiconducting properties with widely tunable band gap from 0 to 2.87 eV due to quantum confinement effect imposed by the SiC domains, the homogeneous structures can be semiconducting or remain semimetallic depending on a superlattice vector which dictates whether the sublattice symmetry is topologically broken. Moreover, we reveal a universal rule for describing the electronic properties of the homogeneous SixC1-x structures. These findings suggest that the 2D SixC1-x monolayers may present a new "family" of 2D materials, with a rich variety of properties for applications in electronics and optoelectronics.

  1. Comprehensive two-dimensional gas chromatography-mass spectrometry analysis of volatile constituents in Thai vetiver root oils obtained by using different extraction methods.

    Science.gov (United States)

    Pripdeevech, Patcharee; Wongpornchai, Sugunya; Marriott, Philip J

    2010-01-01

    Vetiver root oil is known as one of the finest fixatives used in perfumery. This highly complex oil contains more than 200 components, which are mainly sesquiterpene hydrocarbons and their oxygenated derivatives. Since conventional GC-MS has limitation in terms of separation efficiency, the comprehensive two-dimensional GC-MS (GC x GC-MS) was proposed in this study as an alternative technique for the analysis of vetiver oil constituents. To evaluate efficiency of the hyphenated GC x GC-MS technique in terms of separation power and sensitivity prior to identification and quantitation of the volatile constituents in a variety of vetiver root oil samples. METHODOLOGY. Dried roots of Vetiveria zizanioides were subjected to extraction using various conditions of four different methods; simultaneous steam distillation, supercritical fluid, microwave-assisted, and Soxhlet extraction. Volatile components in all vetiver root oil samples were separated and identified by GC-MS and GC x GC-MS. The relative contents of volatile constituents in each vetiver oil sample were calculated using the peak volume normalization method. Different techniques of extraction had diverse effects on yield, physical and chemical properties of the vetiver root oils obtained. Overall, 64 volatile constituents were identified by GC-MS. Among the 245 well-resolved individual components obtained by GC x GC-MS, the additional identification of 43 more volatiles was achieved. In comparison with GC-MS, GC x GC-MS showed greater ability to differentiate the quality of essential oils obtained from diverse extraction conditions in terms of their volatile compositions and contents.

  2. FACE RECOGNITION USING TWO DIMENSIONAL LAPLACIAN EIGENMAP

    Institute of Scientific and Technical Information of China (English)

    Chen Jiangfeng; Yuan Baozong; Pei Bingnan

    2008-01-01

    Recently,some research efforts have shown that face images possibly reside on a nonlinear sub-manifold. Though Laplacianfaces method considered the manifold structures of the face images,it has limits to solve face recognition problem. This paper proposes a new feature extraction method,Two Dimensional Laplacian EigenMap (2DLEM),which especially considers the manifold structures of the face images,and extracts the proper features from face image matrix directly by using a linear transformation. As opposed to Laplacianfaces,2DLEM extracts features directly from 2D images without a vectorization preprocessing. To test 2DLEM and evaluate its performance,a series of ex-periments are performed on the ORL database and the Yale database. Moreover,several experiments are performed to compare the performance of three 2D methods. The experiments show that 2DLEM achieves the best performance.

  3. The Rare Two-Dimensional Materials with Dirac Cones

    OpenAIRE

    Wang, Jinying; Deng, Shibin; Liu, Zhongfan; Liu, Zhirong

    2014-01-01

    Inspired by the great development of graphene, more and more works have been conducted to seek new two-dimensional (2D) materials with Dirac cones. Although 2D Dirac materials possess many novel properties and physics, they are rare compared with the numerous 2D materials. To provide explanation for the rarity of 2D Dirac materials as well as clues in searching for new Dirac systems, here we review the recent theoretical aspects of various 2D Dirac materials, including graphene, silicene, ger...

  4. Two-dimensional signal analysis

    CERN Document Server

    Garello, René

    2010-01-01

    This title sets out to show that 2-D signal analysis has its own role to play alongside signal processing and image processing.Concentrating its coverage on those 2-D signals coming from physical sensors (such as radars and sonars), the discussion explores a 2-D spectral approach but develops the modeling of 2-D signals and proposes several data-oriented analysis techniques for dealing with them. Coverage is also given to potential future developments in this area.

  5. Probing 2D Quantum Turbulence in Atomic Superfluid Gas using Bragg Scattering

    CERN Document Server

    Seo, Sang Won; Kim, Joon Hyun; Shin, Yong-il

    2016-01-01

    We demonstrate the use of spatially resolved Bragg spectroscopy for detection of the quantum vortex circulation signs in an atomic Bose-Einstein condensate (BEC). High-velocity atoms near the vortex cores are resonantly scattered from the BEC, and the vortex signs are determined from the scattered atom positions relative to the corresponding vortex cores. Using this method, we investigate decaying 2D quantum turbulence in a highly oblate BEC at temperatures of $\\sim 0.5 T_c$, where $T_c$ is the critical temperature of the trapped sample. Clustering of like-sign vortices is not observed; rather, the measured vortex configurations reveal weak pair correlations between the vortices and antivortices in the turbulent BEC. Our Bragg scattering method enables a direct experimental study of 2D quantum turbulence in BECs.

  6. A 2d model for the effect of gas diffusion on mobility of foam for EOR

    NARCIS (Netherlands)

    Nonnekes, L.E.; Cox, S.J.; Rossen, W.R.

    2012-01-01

    Transport of gas across liquid films between bubbles is cited as one reason why CO2 foams for enhanced oil recovery (EOR) are usually weaker than N2 foams and why steam foams are weaker than foams of steam mixed with N2. We examine here the effect of inter-bubble gas diffusion on flowing bubbles in

  7. Black tea volatiles fingerprinting by comprehensive two-dimensional gas chromatography - Mass spectrometry combined with high concentration capacity sample preparation techniques: Toward a fully automated sensomic assessment.

    Science.gov (United States)

    Magagna, Federico; Cordero, Chiara; Cagliero, Cecilia; Liberto, Erica; Rubiolo, Patrizia; Sgorbini, Barbara; Bicchi, Carlo

    2017-06-15

    Tea prepared by infusion of dried leaves of Camellia sinensis (L.) Kuntze, is the second world's most popular beverage, after water. Its consumption is associated with its chemical composition: it influences its sensory and nutritional quality addressing consumer preferences, and potential health benefits. This study aims to obtain an informative chemical signature of the volatile fraction of black tea samples from Ceylon by applying the principles of sensomics. In particular, several high concentration capacity (HCC) sample preparation techniques were tested in combination with GC×GC-MS to investigate chemical signatures of black tea volatiles. This platform, using headspace solid phase microextraction (HS-SPME) with multicomponent fiber as sampling technique, recovers 95% of the key-odorants in a fully automated work-flow. A group 123 components, including key-odorants, technological and botanical tracers, were mapped. The resulting 2D fingerprints were interpreted by pattern recognition tools (i.e. template matching fingerprinting and scripting) providing highly informative chemical signatures for quality assessment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Quantum Oscillations in a Two-Dimensional Electron Gas at the Rocksalt/Zincblende Interface of PbTe/CdTe (111) Heterostructures.

    Science.gov (United States)

    Zhang, Bingpo; Lu, Ping; Liu, Henan; Jiao, Lin; Ye, Zhenyu; Jaime, M; Balakirev, F F; Yuan, Huiqiu; Wu, Huizhen; Pan, Wei; Zhang, Yong

    2015-07-08

    Quantum oscillations are observed in the 2DEG system at the interface of novel heterostructures, PbTe/CdTe (111), with nearly identical lattice parameters (a(PbTe) = 0.6462 nm, a(CdTe) = 0.648 nm) but very different lattice structures (PbTe: rock salt, CdTe: zinc blende). The 2DEG formation mechanism, a mismatch in the bonding configurations of the valence electrons at the interface, is uniquely different from the other known 2DEG systems. The aberration-corrected scanning transmission electron microscope (AC-STEM) characterization indicates an abrupt interface without cation interdiffusion due to a large miscibility gap between the two constituent materials. Electronic transport measurements under magnetic field up to 60 T, with the observation of Landau level filling factor ν = 1, unambiguously reveal a π Berry phase, suggesting the Dirac Fermion nature of the 2DEG at the heterostructure interface, and the PbTe/CdTe heterostructure being a new candidate for 2D topological crystalline insulators.

  9. Two-dimensional liquid chromatography

    DEFF Research Database (Denmark)

    Græsbøll, Rune

    of this thesis is on online comprehensive two-dimensional liquid chromatography (online LC×LC) with reverse phase in both dimensions (online RP×RP). Since online RP×RP has not been attempted before within this research group, a significant part of this thesis consists of knowledge and experience gained...

  10. Long-range ordering of topological excitations in a two-dimensional superfluid far from equilibrium

    Science.gov (United States)

    Salman, Hayder; Maestrini, Davide

    2016-10-01

    We study the relaxation of a two-dimensional (2D) ultracold Bose gas from a nonequilibrium initial state containing vortex excitations in experimentally realizable square and rectangular traps. We show that the subsystem of vortex gas excitations results in the spontaneous emergence of a coherent superfluid flow with a nonzero coarse-grained vorticity field. The stream function of this emergent quasiclassical 2D flow is governed by a Poisson-Boltzmann equation. This equation reveals that maximum entropy states of a neutral vortex gas that describe the spectral condensation of energy can be classified into types of flow depending on whether or not the flow spontaneously acquires angular momentum. Numerical simulations of a neutral point vortex model and a Bose gas governed by the 2D Gross-Pitaevskii equation in a square reveal that a large-scale monopole flow field with net angular momentum emerges that is consistent with predictions of the Poisson-Boltzmann equation. The results allow us to characterize the spectral energy condensate in a 2D quantum fluid that bears striking similarity to similar flows observed in experiments of 2D classical turbulence. By deforming the square into a rectangular region, the resulting maximum entropy state switches to a dipolar flow field with zero net angular momentum.

  11. Identifying Shallow Gas Reservoir Using 2D Seismic data and Seismic Attribute Analysis over Shahbazpur Structure, Bhola, Southern Bangladesh.

    Science.gov (United States)

    Rahman, M.; Imam, B.; Kabir, S. M. M.; Mustaque, S.; Gazi, M. Y.

    2016-12-01

    The Shahbazpur structure is a subsurface anticlinal structure situated in the middle of the Bhola Island in the northern margin of Hatia trough of Bengal Foredeep. Bangladesh petroleum exploration and production company Ltd. (BAPEX) discovered the Shahbazpur gas field in its exploration well Shahbazpur-1, in which commercial gas pools were tested positively from depth range of 3154m to 3212m below surface. A method is established to delineate the structural mapping precisely by interpreting Eight 2D seismic lines that are acquired over Shahbazpur structure. Moreover direct hydrocarbon indicators (DHI) related attributes are analyzed for further confirmation for presence of hydrocarbon in shallow to moderate depth. To do this synthetic seismogram generation, seismic to well tie, velocity modelling and depth conversion are performed. A limited number of seismic attributes functions that are available in an academic version of Petrel software are applied to analyze attributes. Seismic attribute analyses that are used in this interpretation mainly are associated to bright spot detection. Seismic indication of gas accumulation in 2D seismic line; RMS amplitude and Envelope attribute map from seismic attribute analysis shows presence of bright spots or high amplitude anomaly above the present Shahbazpur structure reservoir zone. This signature will play a very important role in next well planning on the same structure to test the shallow accumulation of hydrocarbon. For better understanding of this shallow reserve, it is suggested to acquire 3D seismic data over Shahbazpur structure which will help to evaluate the hydrocarbon accumulation and to identify gas migration pathways.

  12. Quantum and Transport Mobilities of a Two-Dimensional Electron Gas in the Presence of the Rashba Spin-Orbit Interaction

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A systematic theoretical approach is developed to study the electronic and transport properties of a twodimensional electron gas (2DEG) in the presence of spin-orbit interactions induced by the Rashba effect. The standard random-phase approximation is employed to calculate the screening length caused by electron-electron interaction in different transition channels. The quantum and transport mobilities in different spin branches are evaluated using the momentum-balance equation derived from the Boltzmann equation,in which the electron interactions with both the remote and background impurities are taken into account in an InAlAs/InGaAs heterojunction at low-temperatures.

  13. Acousto-exciton interaction in a gas of 2D indirect dipolar excitons in the presence of disorder

    Energy Technology Data Exchange (ETDEWEB)

    Kovalev, V. M.; Chaplik, A. V., E-mail: chaplik@isp.nsc.ru [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

    2016-03-15

    A theory for the linear and quadratic responses of a 2D gas of indirect dipolar excitons to an external surface acoustic wave perturbation in the presence of a static random potential is considered. The theory is constructed both for high temperatures, definitely greater than the exciton gas condensation temperature, and at zero temperature by taking into account the Bose–Einstein condensation effects. The particle Green functions, the density–density correlation function, and the quadratic response function are calculated by the “cross” diagram technique. The results obtained are used to calculate the absorption of Rayleigh surface waves and the acoustic exciton gas drag by a Rayleigh wave. The damping of Bogoliubov excitations in an exciton condensate due to theirs scattering by a random potential has also been determined.

  14. Retrospective analysis by data processing tools for comprehensive two-dimensional gas chromatography coupled to high resolution time-of-flight mass spectrometry: a challenge for matrix-rich sediment core sample from Tokyo Bay.

    Science.gov (United States)

    Zushi, Yasuyuki; Hashimoto, Shunji; Tamada, Masafumi; Masunaga, Shigeki; Kanai, Yutaka; Tanabe, Kiyoshi

    2014-04-18

    Data processing tools for non-target analysis using comprehensive two-dimensional gas chromatography coupled with high-resolution time-of-flight mass spectrometry (GC×GC-HRTOFMS) were developed and applied to a sediment core in Tokyo Bay, focusing on chlorinated compounds in this study. The processing tools were classified in two different methods: (1) the consecutive use of mass defect filter followed by artificial neutral loss scan (MDF/artificial NLS) as a qualitative non-target screening method and (2) Entire Domain Combined Spectra Extraction and Integration Program (ComSpec) and two-dimensional peak sentinel (T-SEN) as a semi-quantitative target screening method. MDF/artificial NLS as a non-target screening approach revealed that PCBs, followed by octachlorodibenzo dioxin (OCDD), were the main chlorinated compounds present in all sediment layers. Furthermore, unknown peaks thought to be chlorinated compounds were found in increasing numbers, some in increasing amounts. T-SEN and ComSpec as a target screening approach were adapted for automatic semi-quantitative analysis showed that, in decreasing concentration order, PCBs, OCDD, and dichlorodiphenyltrichloroethane and its metabolites (DDEs, DDDs) were the main chlorinated pollutants in the sediments. The complementary use of both techniques allows us to extract significant chlorinated pollutants, including non-targeted compounds. This retrospective analysis by this approach performed well even on matrix-rich sediment samples and provided us an interesting insight of historical trends of pollution in Tokyo Bay.

  15. Determination of emerging contaminants in wastewater utilizing comprehensive two-dimensional gas-chromatography coupled with time-of-flight mass spectrometry.

    Science.gov (United States)

    Prebihalo, Sarah; Brockman, Adrienne; Cochran, Jack; Dorman, Frank L

    2015-11-06

    An analytical method for identification of emerging contaminants of concern, such as pesticides and organohalogens has been developed and utilized for true discovery-based analysis. In order to achieve the level of sensitivity and selectivity necessary for detecting compounds in complex samples, comprehensive gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) was utilized to analyze wastewater samples obtained from the Pennsylvania State University wastewater treatment facility (WWTF). Determination of emerging contaminants through a process of combining samples which represent "normal background" and comparing this to new samples was developed. Results show the presence of halogenated benzotriazoles in wastewater samples as well as soil samples from Pennsylvania State University agricultural fields. The trace levels of chlorinated benzotriazoles observed in the monitoring wells present on the property indicate likely environmental degradation of the chlorinated benzotriazoles. Preliminary investigation of environmental fate of the substituted benzotriazoles indicates their likely degradation into phenol; an Environmental Protection Agency (USEPA) priority pollutant.

  16. Anisotropic electrical transport properties of a two-dimensional electron gas at SrTiO3-LaAlO3 interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Brinks, Peter [University of Twente, Enschede, Netherlands; Siemons, Wolter [ORNL; Kleibeuker, Josee [University of Twente, Enschede, Netherlands; Koster, Gertjan [University of Twente, Enschede, Netherlands; Rijnders, Guus [MESA+ University of Twente, Enschede, Netherlands; Huijben, Mark [University of Twente, Enschede, Netherlands

    2011-01-01

    Experimental evidence of strong in-plane anisotropy in electrical properties of the confined electron gas at the SrTiO{sub 3}-LaAlO{sub 3} interface on top of (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 3}){sub 0.7} substrates is provided by detailed transport measurements. Structured measurement geometries in multiple directions are used to show dependence of the sheet resistance with the in-plane angle {theta}, which is fitted with a sine function with a period of 180{sup o}. The carrier density remains constant and a directional dependence of the carrier mobility of more than one order of magnitude is determined with respect to the orientation of the unit cell height steps present at the SrTiO{sub 3}-LaAlO{sub 3} interface.

  17. Two-Dimensional Materials for Sensing: Graphene and Beyond

    Directory of Open Access Journals (Sweden)

    Seba Sara Varghese

    2015-09-01

    Full Text Available Two-dimensional materials have attracted great scientific attention due to their unusual and fascinating properties for use in electronics, spintronics, photovoltaics, medicine, composites, etc. Graphene, transition metal dichalcogenides such as MoS2, phosphorene, etc., which belong to the family of two-dimensional materials, have shown great promise for gas sensing applications due to their high surface-to-volume ratio, low noise and sensitivity of electronic properties to the changes in the surroundings. Two-dimensional nanostructured semiconducting metal oxide based gas sensors have also been recognized as successful gas detection devices. This review aims to provide the latest advancements in the field of gas sensors based on various two-dimensional materials with the main focus on sensor performance metrics such as sensitivity, specificity, detection limit, response time, and reversibility. Both experimental and theoretical studies on the gas sensing properties of graphene and other two-dimensional materials beyond graphene are also discussed. The article concludes with the current challenges and future prospects for two-dimensional materials in gas sensor applications.

  18. Two-Dimensional Atomic-Layered Alloy Junctions for High-Performance Wearable Chemical Sensor.

    Science.gov (United States)

    Cho, Byungjin; Kim, Ah Ra; Kim, Dong Jae; Chung, Hee-Suk; Choi, Sun Young; Kwon, Jung-Dae; Park, Sang Won; Kim, Yonghun; Lee, Byoung Hun; Lee, Kyu Hwan; Kim, Dong-Ho; Nam, Jaewook; Hahm, Myung Gwan

    2016-08-03

    We first report that two-dimensional (2D) metal (NbSe2)-semiconductor (WSe2)-based flexible, wearable, and launderable gas sensors can be prepared through simple one-step chemical vapor deposition of prepatterned WO3 and Nb2O5. Compared to a control device with a Au/WSe2 junction, gas-sensing performance of the 2D NbSe2/WSe2 device was significantly enhanced, which might have resulted from the formation of a NbxW1-xSe2 transition alloy junction lowering the Schottky barrier height. This would make it easier to collect charges of channels induced by molecule adsorption, improving gas response characteristics toward chemical species including NO2 and NH3. 2D NbSe2/WSe2 devices on a flexible substrate provide gas-sensing properties with excellent durability under harsh bending. Furthermore, the device stitched on a T-shirt still performed well even after conventional cleaning with a laundry machine, enabling wearable and launderable chemical sensors. These results could pave a road toward futuristic gas-sensing platforms based on only 2D materials.

  19. Two-dimensional investigation of forced bubble oscillation under microgravity

    Institute of Scientific and Technical Information of China (English)

    HONG Ruoyu; Masahiro KAWAJI

    2003-01-01

    Recent referential studies of fluid interfaces subjected to small vibration under microgravity conditions are reviewed. An experimental investigation was carried out aboard the American Space Shuttle Discovery. Two-dimensional (2-D) modeling and simulation were conducted to further understand the experimental results. The oscillation of a bubble in fluid under surface tension is governed by the incompressible Navier-Stokes equations. The SIMPLEC algorithm was used to solve the partial differential equations on an Eulerian mesh in a 2-D coordinate. Free surfaces were represented with the volume of fluid (VOF) obtained by solving a kinematic equation. Surface tension was modeled via a continuous surface force (CSF) algorithm that ensures robustness and accuracy. A new surface reconstruction scheme, alternative phase integration (API) scheme, was adopted to solve the kinematic equation, and was compared with referential schemes. Numerical computations were conducted to simulate the transient behavior of an oscillating gas bubble in mineral oil under different conditions. The bubble positions and shapes under different external vibrations were obtained numerically. The computed bubble oscillation amplitudes were compared with experimental data.

  20. Qualitative Characterization of the Aqueous Fraction from Hydrothermal Liquefaction of Algae Using 2D Gas Chromatography with Time-of-flight Mass Spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Maddi, Balakrishna; Panisko, Ellen; Albrecht, Karl; Howe, Daniel

    2016-01-01

    Two-dimensional gas chromatography coupled with time of flight mass spectrometry is a powerful tool for identifying and quantifying components in complex mixtures. It has been used to analyze gasoline, jet fuel, diesel, bio-diesel and organic fraction of bio-crude/bio-oil. In these experiments, the first dimension of separation was non-polar, followed by a polar separation. Aqueous fractions of bio-crude and other aqueous samples have been examined with similar column combinations. However, sample preparation techniques such as derivatization, solvent extraction, and solid-phase extraction were necessary prior to analysis. In this study, aqueous fraction obtained from hydrothermal liquefaction of algae was characterized by two-dimensional gas chromatography coupled with time of flight mass spectrometry without prior sample preparation techniques using a polar separation in the first dimension followed by a non-polar separation. Two-dimensional plots from this analysis were compared with those obtained from the more traditional column combination. Results from qualitative characterization aqueous fractions of algal bio-crude are discussed in detail. The advantages of using a polar separation followed by a non-polar separation for characterization of organics in aqueous samples by two-dimensional gas chromatography coupled with time of flight mass spectrometry are highlighted.

  1. Flexible Two-Dimensional Square-Grid Coordination Polymers: Structures and Functions

    Science.gov (United States)

    Kajiro, Hiroshi; Kondo, Atsushi; Kaneko, Katsumi; Kanoh, Hirofumi

    2010-01-01

    Coordination polymers (CPs) or metal-organic frameworks (MOFs) have attracted considerable attention because of the tunable diversity of structures and functions. A 4,4′-bipyridine molecule, which is a simple, linear, exobidentate, and rigid ligand molecule, can construct two-dimensional (2D) square grid type CPs. Only the 2D-CPs with appropriate metal cations and counter anions exhibit flexibility and adsorb gas with a gate mechanism and these 2D-CPs are called elastic layer-structured metal-organic frameworks (ELMs). Such a unique property can make it possible to overcome the dilemma of strong adsorption and easy desorption, which is one of the ideal properties for practical adsorbents. PMID:21152303

  2. Flexible Two-Dimensional Square-Grid Coordination Polymers: Structures and Functions

    Directory of Open Access Journals (Sweden)

    Hiroshi Kajiro

    2010-09-01

    Full Text Available Coordination polymers (CPs or metal-organic frameworks (MOFs have attracted considerable attention because of the tunable diversity of structures and functions. A 4,4'-bipyridine molecule, which is a simple, linear, exobidentate, and rigid ligand molecule, can construct two-dimensional (2D square grid type CPs. Only the 2D-CPs with appropriate metal cations and counter anions exhibit flexibility and adsorb gas with a gate mechanism and these 2D-CPs are called elastic layer-structured metal-organic frameworks (ELMs. Such a unique property can make it possible to overcome the dilemma of strong adsorption and easy desorption, which is one of the ideal properties for practical adsorbents.

  3. Graphene and Two-Dimensional Materials for Optoelectronic Applications

    Directory of Open Access Journals (Sweden)

    Andreas Bablich

    2016-03-01

    Full Text Available This article reviews optoelectronic devices based on graphene and related two-dimensional (2D materials. The review includes basic considerations of process technology, including demonstrations of 2D heterostructure growth, and comments on the scalability and manufacturability of the growth methods. We then assess the potential of graphene-based transparent conducting electrodes. A major part of the review describes photodetectors based on lateral graphene p-n junctions and Schottky diodes. Finally, the progress in vertical devices made from 2D/3D heterojunctions, as well as all-2D heterostructures is discussed.

  4. Two dimensional unstable scar statistics.

    Energy Technology Data Exchange (ETDEWEB)

    Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Kotulski, Joseph Daniel; Lee, Kelvin S. H. (ITT Industries/AES Los Angeles, CA)

    2006-12-01

    This report examines the localization of time harmonic high frequency modal fields in two dimensional cavities along periodic paths between opposing sides of the cavity. The cases where these orbits lead to unstable localized modes are known as scars. This paper examines the enhancements for these unstable orbits when the opposing mirrors are both convex and concave. In the latter case the construction includes the treatment of interior foci.

  5. Two-Dimensional Vernier Scale

    Science.gov (United States)

    Juday, Richard D.

    1992-01-01

    Modified vernier scale gives accurate two-dimensional coordinates from maps, drawings, or cathode-ray-tube displays. Movable circular overlay rests on fixed rectangular-grid overlay. Pitch of circles nine-tenths that of grid and, for greatest accuracy, radii of circles large compared with pitch of grid. Scale enables user to interpolate between finest divisions of regularly spaced rule simply by observing which mark on auxiliary vernier rule aligns with mark on primary rule.

  6. Contribution of alloy clustering to limiting the two-dimensional electron gas mobility in AlGaN/GaN and InAlN/GaN heterostructures: Theory and experiment

    Energy Technology Data Exchange (ETDEWEB)

    Ahmadi, Elaheh; Mishra, Umesh K. [Electrical and Computer Engineering Department, University of California, Santa Barbara, California 93106 (United States); Chalabi, Hamidreza [Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305 (United States); Kaun, Stephen W.; Shivaraman, Ravi; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2014-10-07

    The influence of alloy clustering on fluctuations in the ground state energy of the two-dimensional electron gas (2DEG) in AlGaN/GaN and InAlN/GaN heterostructures is studied. We show that because of these fluctuations, alloy clustering degrades the mobility even when the 2DEG wavefunction does not penetrate the alloy barrier unlike alloy disorder scattering. A comparison between the results obtained for AlGaN/GaN and InAlN/GaN heterostructures shows that alloy clustering limits the 2DEG mobility to a greater degree in InAlN/GaN heterostructures. Our study also reveals that the inclusion of an AlN interlayer increases the limiting mobility from alloy clustering. Moreover, Atom probe tomography is used to demonstrate the random nature of the fluctuations in the alloy composition.

  7. Caracterização de amostras petroquímicas e derivados utilizando cromatografia gasosa bidimensional abrangente (GCxGC Characterization of petrochemical samples and their derivatives by comprehensive two-dimensional gas chromatography

    Directory of Open Access Journals (Sweden)

    Carin von Mühlen

    2006-07-01

    Full Text Available The goal of this article is to discuss the application of comprehensive two-dimensional gas chromatography (GCxGC to petrochemical samples. The use of GCxGC for petroleum and petroleum derivatives characterization, through group type analysis, or BTEX (benzene, toluene, ethylbenzene, xylenes, total aromatic hydrocarbons, polyaromatic hydrocarbons, sulfur-containing, oxygen-containing, and nitrogen-containing compounds is presented. The capability of GCxGC to provide additional specific chemical information regarding petroleum processing steps, such as dehydrogenation of linear alkanes, the Fischer-Tropsch process, hydrogenation and oligomerization is also described. In addition, GCxGC analyses of petrochemical biomarkers and environmental pollutants derived from petrochemicals are reported.

  8. Qualitative analysis of a sulfur-fumigated Chinese herbal medicine by comprehensive two-dimensional gas chromatography and high-resolution time of flight mass spectrometry using colorized fuzzy difference data processing.

    Science.gov (United States)

    Cai, Hao; Cao, Gang; Zhang, Hong-Yan

    2017-04-01

    To investigate the chemical transformation of volatile compounds in sulfur-fumigated Radix Angelicae Sinensis. A comprehensive two-dimensional gas chromatography (GC×GC) and high-resolution time-of-flight mass spectrometry (HR-TOF/MS) with colorized fuzzy difference (CFD) method was used to investigate the effect of sulfur-fumigation on the volatile components from Radix Angelicae Sinensis. Twenty-five compounds that were found in sun-dried samples disappeared in sulfur-fumigated samples. Seventeen volatile components including two sulfur-containing compounds were newly generated for the first time in volatile oils of sulfur-fumigated Radix Angelicae Sinensis. The strategy can be successfully applied to rapidly and holistically discriminate sun-dried and sulfur-fumigated Radix Angelicae Sinensis. GC×GC-HR-TOF/MS based CFD is a powerful and feasible approach for the global quality evaluation of Radix Angelicae Sinensis as well as other herbal medicines.

  9. A purge and trap technique to capture volatile compounds combined with comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry to investigate the effect of sulfur-fumigation on Radix Angelicae Dahuricae.

    Science.gov (United States)

    Cao, Gang; Li, Qinglin; Zhang, Jida; Cai, Hao; Cai, Baochang

    2014-09-01

    Sulfur-fumigation is known to reduce volatile compounds that are the main active components in herbs used in herbal medicine. We investigated changes in chemical composition between sun-dried and sulfur-fumigated Radix Angelicae Dahuricae using a purge and trap technique to capture volatile compounds, and two-dimensional gas chromatography/time-of-flight mass spectrometry for identification. Using sun-dried Radix Angelicae Dahuricae samples as a reference, the results showed that 73 volatile compounds, including 12 sulfide compounds, were found to be present only in sulfur-fumigated samples. Furthermore, 32 volatile compounds that were found in sun-dried Radix Angelicae Dahuricae samples disappeared after sulfur-fumigation. The proposed method can be applied to accurately discriminate sulfur-fumigated Radix Angelicae Dahuricae from different commercial sources.

  10. The ferroelectric field effect on the two-dimensional electron gas at LaAlO3/SrTiO3 (001) interface: Insights from first principle simulations

    Science.gov (United States)

    Gao, Yu-Qiang; Li, Pan; Wang, Nan; Xing, Hui; Chen, Chang-Le

    2016-06-01

    We perform first-principles calculations to explore the possibility of tuning the two-dimensional electron gas at the LaAlO3/SrTiO3 (001) interface through BaTiO3 substrate. A metal-to-insulator transition is found at the interface as the polarization of BaTiO3 reverses. Through the potential analysis of the LaAlO3/SrTiO3/BaTiO3 superstructure, we find that the intrinsic electric field of LaAlO3 is significantly suppressed as the polarization points away from the LaAlO3/SrTiO3 interface, while it is enhanced with the polarization pointing to the interface. The ferroelectric field control of the intrinsic electric field, and therefore the electronic reconstructions at the interface, originating from the screening of polarization charges, opens the way to the development of novel nanoscale electronic devices.

  11. 2D Time-lapse Resistivity Monitoring of an Organic Produced Gas Plume in a Landfill using ERT.

    Science.gov (United States)

    Amaral, N. D.; Mendonça, C. A.; Doherty, R.

    2014-12-01

    This project has the objective to study a landfill located on the margins of Tietê River, in São Paulo, Brazil, using the electroresistivity tomography method (ERT). Due to huge organic matter concentrations in the São Paulo Basin quaternary sediments, there is subsurface depth related biogas accumulation (CH4 and CO2), induced by anaerobic degradation of the organic matter. 2D resistivity sections were obtained from a test area since March 2012, a total of 7 databases, being the last one dated from October 2013. The studied line has the length of 56m, the electrode interval is of 2m. In addition, there are two boreholes along the line (one with 3 electrodes and the other one with 2) in order to improve data quality and precision. The boreholes also have a multi-level sampling system that indicates the fluid (gas or water) presence in relation to depth. With our results it was possible to map the gas plume position and its area of extension in the sections as it is a positive resistivity anomaly, with the gas level having approximately 5m depth. With the time-lapse analysis (Matlab script) between the obtained 2D resistivity sections from the site, it was possible to map how the biogas volume and position change in the landfill in relation to time. Our preliminary results show a preferential gas pathway through the subsurface studied area. A consistent relation between the gas depth and obtained microbiological data from archea and bacteria population was also observed.

  12. Subsurface Gas Flow and Ice Grain Acceleration within Enceladus and Europa Fissures: 2D DSMC Models

    Science.gov (United States)

    Tucker, O. J.; Combi, M. R.; Tenishev, V.

    2014-12-01

    The ejection of material from geysers is a ubiquitous occurrence on outer solar system bodies. Water vapor plumes have been observed emanating from the southern hemispheres of Enceladus and Europa (Hansen et al. 2011, Roth et al. 2014), and N2plumes carrying ice and ark particles on Triton (Soderblom et al. 2009). The gas and ice grain distributions in the Enceladus plume depend on the subsurface gas properties and the geometry of the fissures e.g., (Schmidt et al. 2008, Ingersoll et al. 2010). Of course the fissures can have complex geometries due to tidal stresses, melting, freezing etc., but directly sampled and inferred gas and grain properties for the plume (source rate, bulk velocity, terminal grain velocity) can be used to provide a basis to constrain characteristic dimensions of vent width and depth. We used a 2-dimensional Direct Simulation Monte Carlo (DSMC) technique to model venting from both axi-symmetric canyons with widths ~2 km and narrow jets with widths ~15-40 m. For all of our vent geometries, considered the water vapor source rates (1027­ - 1028 s-1) and bulk gas velocities (~330 - 670 m/s) obtained at the surface were consistent with inferred values obtained by fits of the data for the plume densities (1026 - 1028 s-1, 250 - 1000 m/s) respectively. However, when using the resulting DSMC gas distribution for the canyon geometries to integrate the trajectories of ice grains we found it insufficient to accelerate submicron ice grains to Enceladus' escape speed. On the other hand, the gas distributions in the jet like vents accelerated grains > 10 μm significantly above Enceladus' escape speed. It has been suggested that micron-sized grains are ejected from the vents with speeds comparable to the Enceladus escape speed. Here we report on these results including comparisons to results obtained from 1D models as well as discuss the implications of our plume model results. We also show preliminary results for similar considerations applied to Europa

  13. Development of a selftriggered high counting rate ASIC for readout of 2D gas microstrip neutron detectors

    CERN Document Server

    Brogna, AS; Dabrowski, W; Fiutowski, T; Gebauer, B; Mindur, B; Schmidt, Ch J; Schulz, Ch; Soltveit, H K; Szczygiel, R; Trunk, U; Wiacek, P

    2007-01-01

    In the frame of the DETNI project a 32-channel ASIC suitable for readout of a novel 2D thermal neutron detector based on a hybrid low-pressure Micro-Strip Gas Chamber with solid 157Gd converter has been developed. Each channel delivers position information, a fast time stamp of 2 ns resolution and the signal amplitude (called energy below). The time stamp is used for correlating the signals from X and Y strips while the amplitude is used for finding the center of gravity of a cluster of strips. The timing and energy information are stored in derandomizing buffers and read out via token ring architecture.

  14. metAlignID: a high-throughput software tool set for automated detection of trace level contaminants in comprehensive LECO two-dimensional gas chromatography time-of-flight mass spectrometry data.

    Science.gov (United States)

    Lommen, Arjen; van der Kamp, Henk J; Kools, Harrie J; van der Lee, Martijn K; van der Weg, Guido; Mol, Hans G J

    2012-11-09

    A new alternative data processing tool set, metAlignID, is developed for automated pre-processing and library-based identification and concentration estimation of target compounds after analysis by comprehensive two-dimensional gas chromatography with mass spectrometric detection. The tool set has been developed for and tested on LECO data. The software is developed to run multi-threaded (one thread per processor core) on a standard PC (personal computer) under different operating systems and is as such capable of processing multiple data sets simultaneously. Raw data files are converted into netCDF (network Common Data Form) format using a fast conversion tool. They are then preprocessed using previously developed algorithms originating from metAlign software. Next, the resulting reduced data files are searched against a user-composed library (derived from user or commercial NIST-compatible libraries) (NIST=National Institute of Standards and Technology) and the identified compounds, including an indicative concentration, are reported in Excel format. Data can be processed batch wise. The overall time needed for conversion together with processing and searching of 30 raw data sets for 560 compounds is routinely within an hour. The screening performance is evaluated for detection of pesticides and contaminants in raw data obtained after analysis of soil and plant samples. Results are compared to the existing data-handling routine based on proprietary software (LECO, ChromaTOF). The developed software tool set, which is freely downloadable at www.metalign.nl, greatly accelerates data-analysis and offers more options for fine-tuning automated identification toward specific application needs. The quality of the results obtained is slightly better than the standard processing and also adds a quantitative estimate. The software tool set in combination with two-dimensional gas chromatography coupled to time-of-flight mass spectrometry shows great potential as a highly

  15. A Complete 2D Stability Analysis of Fast MHD Shocks in an Ideal Gas

    Science.gov (United States)

    Trakhinin, Yuri

    An algorithm of numerical testing of the uniform Lopatinski condition for linearized stability problems for 1-shocks is suggested. The algorithm is used for finding the domains of uniform stability, neutral stability, and instability of planar fast MHD shocks. A complete stability analysis of fast MHD shock waves is first carried out in two space dimensions for the case of an ideal gas. Main results are given for the adiabatic constant γ=5/3 (mono-atomic gas), that is most natural for the MHD model. The cases γ=7/5 (two-atomic gas) and γ>5/3 are briefly discussed. Not only the domains of instability and linear (in the usual sense) stability, but also the domains of uniform stability, for which a corresponding linearized stability problem satisfies the uniform Lopatinski condition, are numerically found for different given angles of inclination of the magnetic field behind the shock to the planar shock front. As is known, uniform linearized stability implies the nonlinear stability, that is local existence of discontinuous shock front solutions of a quasilinear system of hyperbolic conservation laws.

  16. Acoustic 2D full waveform inversion to solve gas cloud challenges

    Directory of Open Access Journals (Sweden)

    Srichand Prajapati

    2015-09-01

    Full Text Available The existing conventional inversion algorithm does not provide satisfactory results due to the complexity of propagated wavefield though the gas cloud. Acoustic full waveform inversion has been developed and applied to a realistic synthetic offshore shallow gas cloud feature with Student-t approach, with and without simultaneous sources encoding. As a modeling operator, we implemented the grid based finite-difference method in frequency domain using second order elastic wave equation. Jacobin operator and its adjoint provide a necessary platform for solving full waveform inversion problem in a reduced Hessian matrix. We invert gas cloud model in 5 frequency band selected from 1 to 12 Hz, each band contains 3 frequencies. The inversion results are highly sensitive to the misfit. The model allows better convergence and recovery of amplitude losses. This approach gives better resolution then the existing least-squares approach. In this paper, we implement the full waveform inversion for low frequency model with minimum number of iteration providing a better resolution of inversion results.

  17. Photodetectors based on two dimensional materials

    Science.gov (United States)

    Zheng, Lou; Zhongzhu, Liang; Guozhen, Shen

    2016-09-01

    Two-dimensional (2D) materials with unique properties have received a great deal of attention in recent years. This family of materials has rapidly established themselves as intriguing building blocks for versatile nanoelectronic devices that offer promising potential for use in next generation optoelectronics, such as photodetectors. Furthermore, their optoelectronic performance can be adjusted by varying the number of layers. They have demonstrated excellent light absorption, enabling ultrafast and ultrasensitive detection of light in photodetectors, especially in their single-layer structure. Moreover, due to their atomic thickness, outstanding mechanical flexibility, and large breaking strength, these materials have been of great interest for use in flexible devices and strain engineering. Toward that end, several kinds of photodetectors based on 2D materials have been reported. Here, we present a review of the state-of-the-art in photodetectors based on graphene and other 2D materials, such as the graphene, transition metal dichalcogenides, and so on. Project supported by the National Natural Science Foundation of China (Nos. 61377033, 61574132, 61504136) and the State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences.

  18. Molecular assembly on two-dimensional materials

    Science.gov (United States)

    Kumar, Avijit; Banerjee, Kaustuv; Liljeroth, Peter

    2017-02-01

    Molecular self-assembly is a well-known technique to create highly functional nanostructures on surfaces. Self-assembly on two-dimensional (2D) materials is a developing field driven by the interest in functionalization of 2D materials in order to tune their electronic properties. This has resulted in the discovery of several rich and interesting phenomena. Here, we review this progress with an emphasis on the electronic properties of the adsorbates and the substrate in well-defined systems, as unveiled by scanning tunneling microscopy. The review covers three aspects of the self-assembly. The first one focuses on non-covalent self-assembly dealing with site-selectivity due to inherent moiré pattern present on 2D materials grown on substrates. We also see that modification of intermolecular interactions and molecule–substrate interactions influences the assembly drastically and that 2D materials can also be used as a platform to carry out covalent and metal-coordinated assembly. The second part deals with the electronic properties of molecules adsorbed on 2D materials. By virtue of being inert and possessing low density of states near the Fermi level, 2D materials decouple molecules electronically from the underlying metal substrate and allow high-resolution spectroscopy and imaging of molecular orbitals. The moiré pattern on the 2D materials causes site-selective gating and charging of molecules in some cases. The last section covers the effects of self-assembled, acceptor and donor type, organic molecules on the electronic properties of graphene as revealed by spectroscopy and electrical transport measurements. Non-covalent functionalization of 2D materials has already been applied for their application as catalysts and sensors. With the current surge of activity on building van der Waals heterostructures from atomically thin crystals, molecular self-assembly has the potential to add an extra level of flexibility and functionality for applications ranging

  19. Two-Dimensional Numerical Simulation of Gas/Liquid Interface Instability%二维气/液界面不稳定性数值模拟

    Institute of Scientific and Technical Information of China (English)

    王涛; 柏劲松; 李平

    2008-01-01

    以多介质的体积分数方法和三阶PPM(Piecewise Parabolic Method)方法为基础,给出了适用于多介质流体动力学数值模拟的计算方法和程序MFPPM.利用MFPPM程序对在高压气体冲击作用下的气体/液体交界面的Richtmyer-Meshkov (RM) 不稳定性及其引起的流体混合现象进行了数值模拟研究.主要研究在不同的初始扰动情况下流体混合区的发展,并细致研究了流体混合区的宽度、气泡和尖钉高度随时间的增长情况及不同初始扰动对它们的影响;同时还研究了网格尺度不同时混合区、气泡以及尖钉的构型和高度的增长情况.通过对计算结果的分析得出,流体混合区、气泡以及尖钉的发展与初始扰动有密切的关系,特别是在后期影响更为显著;混合区宽度的变化过程和尖钉相似,而气泡高度的变化基本上呈线性增长趋势,且受初始扰动的影响比较小,但是其构型却有明显差别;网格的影响也主要体现在对混合区、气泡和尖钉的构型上.%On the basis of multi-fluid volume fraction(VOF) and piecewise parabolic method(PPM),a multi-fluid hydrodynamic program MFPPM(Multi-Fluid Piecewise Parabolic Method) was developed and performed to study the Richtmyer-Meshkov instability of gas/liquid interface.The influences of initial perturbations and grids on the fluid mixing zone(FMZ) were mainly researched when it is accelerated by shock waves,and the FMZ width,bubble and spike height growing with time were presented simultaneously.By comparing the computational results,it shows that the initial perturbations affect the FMZ growth rate extremely,especially at late times.The evolution of spike is similar to the FMZ,the bubble height increases linearly with time basically,and influenced little by initial perturbations,but the configuration is quite different,and as the effect of grid size is.

  20. 2D Sn-doped ZnO ultrathin nanosheet networks for enhanced acetone gas sensing application

    KAUST Repository

    Al-Hadeethi, Yas

    2016-11-10

    In this paper, we report the synthesis, characterizations and gas sensing application of 2D Sn-doped ZnO ultrathin nanosheet networks synthesized by a simple and facile hydrothermal process. The synthesized nanosheets were characterized using several techniques in terms of their morphological, structural, optical and compositional properties. The detailed characterizations confirmed that the nanosheets are pure, grown in high-density, possessing well-crystalline wurtzite hexagonal phase and exhibiting good optical properties. Further, the synthesized nanosheets were used as functional material to develop nanosensor device by coating it on the alumina substrate with suitable electrodes. The fabricated sensor device was tested towards acetone gas which exhibited a maximum sensitivity of 5.556 (Ra/Rg) for 200 ppm of acetone at 320 °C.

  1. 2D fluid simulations of discharges at atmospheric pressure in reactive gas mixtures

    Science.gov (United States)

    Bourdon, Anne

    2015-09-01

    Since a few years, low-temperature atmospheric pressure discharges have received a considerable interest as they efficiently produce many reactive chemical species at a low energy cost. This potential is of great interest for a wide range of applications as plasma assisted combustion or biomedical applications. Then, in current simulations of atmospheric pressure discharges, there is the need to take into account detailed kinetic schemes. It is interesting to note that in some conditions, the kinetics of the discharge may play a role on the discharge dynamics itself. To illustrate this, we consider the case of the propagation of He-N2 discharges in long capillary tubes, studied for the development of medical devices for endoscopic applications. Simulation results put forward that the discharge dynamics and structure depend on the amount of N2 in the He-N2 mixture. In particular, as the amount of N2 admixture increases, the discharge propagation velocity in the tube increases, reaches a maximum for about 0 . 1 % of N2 and then decreases, in agreement with experiments. For applications as plasma assisted combustion with nanosecond repetitively pulsed discharges, there is the need to handle the very different timescales of the nanosecond discharge with the much longer (micro to millisecond) timescales of combustion processes. This is challenging from a computational point of view. It is also important to better understand the coupling of the plasma induced chemistry and the gas heating. To illustrate this, we present the simulation of the flame ignition in lean mixtures by a nanosecond pulsed discharge between two point electrodes. In particular, among the different discharge regimes of nanosecond repetitively pulsed discharges, a ``spark'' regime has been put forward in the experiments, with an ultra-fast local heating of the gas. For other discharge regimes, the gas heating is much weaker. We have simulated the nanosecond spark regime and have observed shock waves

  2. Configurational entropy of a set of dipoles placed on a two-dimensional lattice

    Science.gov (United States)

    Dammig Quiña, P. L.; Irurzun, I. M.; Mola, E. E.

    2017-01-01

    In the present work we calculate the configurational entropy of an arbitrary number of dipoles placed on a square lattice. We use a quasi-two-dimensional (Q2D) space to capture the main features determining the occupation statistics of this system. We show that our result is in agreement with both, lattice-gas predictions at low coverages and the exact value derived in the close-packed limit as well. Therefore our equation provides a substantial improvement to the most recent calculations based on semiempirical models and Monte Carlo simulations.

  3. Two-dimensional fourier transform spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    DeFlores, Lauren; Tokmakoff, Andrei

    2016-10-25

    The present invention relates to a system and methods for acquiring two-dimensional Fourier transform (2D FT) spectra. Overlap of a collinear pulse pair and probe induce a molecular response which is collected by spectral dispersion of the signal modulated probe beam. Simultaneous collection of the molecular response, pulse timing and characteristics permit real time phasing and rapid acquisition of spectra. Full spectra are acquired as a function of pulse pair timings and numerically transformed to achieve the full frequency-frequency spectrum. This method demonstrates the ability to acquire information on molecular dynamics, couplings and structure in a simple apparatus. Multi-dimensional methods can be used for diagnostic and analytical measurements in the biological, biomedical, and chemical fields.

  4. Two-dimensional fourier transform spectrometer

    Science.gov (United States)

    DeFlores, Lauren; Tokmakoff, Andrei

    2013-09-03

    The present invention relates to a system and methods for acquiring two-dimensional Fourier transform (2D FT) spectra. Overlap of a collinear pulse pair and probe induce a molecular response which is collected by spectral dispersion of the signal modulated probe beam. Simultaneous collection of the molecular response, pulse timing and characteristics permit real time phasing and rapid acquisition of spectra. Full spectra are acquired as a function of pulse pair timings and numerically transformed to achieve the full frequency-frequency spectrum. This method demonstrates the ability to acquire information on molecular dynamics, couplings and structure in a simple apparatus. Multi-dimensional methods can be used for diagnostic and analytical measurements in the biological, biomedical, and chemical fields.

  5. The ionized gas in the central region of NGC 5253: 2D mapping of the physical and chemical properties

    CERN Document Server

    Monreal-Ibero, Ana; Vilchez, Jose M

    2012-01-01

    ABRIDGED: NGC5253 was previously studied by our group with the aim to elucidate in detail the starburst interaction processes. Some open issues regarding the 2D structure of the main properties of the ionized gas remain to be addressed. Using IFS data obtained with FLAMES, we derived 2D maps for different tracers of electron density (n_e), electron temperature (T_e) and ionization degree. The maps for n_e as traced by several line ratios are compatible with a 3D stratified view of the nebula with the highest n_e in the innermost layers and a decrease of n_e outwards. To our knowledge, this is the first time that a T_e map based on [SII] lines for an extragalactic object is presented. The joint interpretation of our two T_e maps is consistent with a T_e structure in 3D with higher temperatures close to the main ionizing source surrounded by a colder and more diffuse component. The highest ionization degree is found at the peak of emission for the gas with relatively high ionization in the main GHIIR and lower ...

  6. Divorticity and dihelicity in two-dimensional hydrodynamics

    DEFF Research Database (Denmark)

    Shivamoggi, B.K.; van Heijst, G.J.F.; Juul Rasmussen, Jens

    2010-01-01

    A framework is developed based on the concepts of divorticity B (≡×ω, ω being the vorticity) and dihelicity g (≡vB) for discussing the theoretical structure underlying two-dimensional (2D) hydrodynamics. This formulation leads to the global and Lagrange invariants that could impose significant...

  7. On the continua in two-dimensional nonadiabatic magnetohydrodynamic spectra

    NARCIS (Netherlands)

    De Ploey, A.; Van der Linden, R. A. M.; Belien, A. J. C.

    2000-01-01

    The equations for the continuous subspectra of the linear magnetohydrodynamic (MHD) normal modes spectrum of two-dimensional (2D) plasmas are derived in general curvilinear coordinates, taking nonadiabatic effects in the energy equation into account. Previously published derivations of continuous sp

  8. Bounds on the capacity of constrained two-dimensional codes

    DEFF Research Database (Denmark)

    Forchhammer, Søren; Justesen, Jørn

    2000-01-01

    Bounds on the capacity of constrained two-dimensional (2-D) codes are presented. The bounds of Calkin and Wilf apply to first-order symmetric constraints. The bounds are generalized in a weaker form to higher order and nonsymmetric constraints. Results are given for constraints specified by run...

  9. Linkage analysis by two-dimensional DNA typing

    NARCIS (Netherlands)

    te Meerman, G J; Mullaart, E; van der Meulen, M A; den Daas, J H; Morolli, B; Uitterlinden, A G; Vijg, J

    1993-01-01

    In two-dimensional (2-D) DNA typing, genomic DNA fragments are separated, first according to size by electrophoresis in a neutral polyacrylamide gel and second according to sequence by denaturing gradient gel electrophoresis, followed by hybridization analysis using micro- and minisatellite core pro

  10. Complex quantum transport in a modulation doped strained Ge quantum well heterostructure with a high mobility 2D hole gas

    Science.gov (United States)

    Morrison, C.; Casteleiro, C.; Leadley, D. R.; Myronov, M.

    2016-09-01

    The complex quantum transport of a strained Ge quantum well (QW) modulation doped heterostructure with two types of mobile carriers has been observed. The two dimensional hole gas (2DHG) in the Ge QW exhibits an exceptionally high mobility of 780 000 cm2/Vs at temperatures below 10 K. Through analysis of Shubnikov de-Haas oscillations in the magnetoresistance of this 2DHG below 2 K, the hole effective mass is found to be 0.065 m0. Anomalous conductance peaks are observed at higher fields which deviate from standard Shubnikov de-Haas and quantum Hall effect behaviour due to conduction via multiple carrier types. Despite this complex behaviour, analysis using a transport model with two conductive channels explains this behaviour and allows key physical parameters such as the carrier effective mass, transport, and quantum lifetimes and conductivity of the electrically active layers to be extracted. This finding is important for electronic device applications, since inclusion of highly doped interlayers which are electrically active, for enhancement of, for example, room temperature carrier mobility, does not prevent analysis of quantum transport in a QW.

  11. Two-dimensional liquid chromatography

    DEFF Research Database (Denmark)

    Græsbøll, Rune

    Two-dimensional liquid chromatography has received increasing interest due to the rise in demand for analysis of complex chemical mixtures. Separation of complex mixtures is hard to achieve as a simple consequence of the sheer number of analytes, as these samples might contain hundreds or even...... dimensions. As a consequence of the conclusions made within this thesis, the research group has, for the time being, decided against further development of online LC×LC systems, since it was not deemed ideal for the intended application, the analysis of the polar fraction of oil. Trap-and...

  12. ``SAFFMAN-TAYLOR'' Finger in 2d Parallel Viscous: BGK Lattice Gas Simulations

    Science.gov (United States)

    Salin, Dominique; Rakotomalala, Nicole; Watzky, Philippe

    1996-11-01

    We study the displacement of miscible fluids between two parallel plates for different values of the Peclet number Pe and of the viscosity ratio M. The full Navier-Stokes problem is addressed. We use the BGK lattice gas method, which is well suited for miscible fluids and allows to introduce molecular diffusion at the microscopic scale of the lattice. This numerical experiment leads to a symmetric concentration profile about the middle of the gap between the plates. At Pe numbers of the order of 1, mixing involves diffusion and advection in the flow direction. At large Pe, the fluids do not mix and an interface between them can be defined. Moreover, above M ~ 10, the interface becomes a well defined finger, the reduced width of which tends to λ_∞=0.56 at large values of M. Assuming that miscible fluids at high Pe numbers are similar to immiscible fluids at high capillary numbers, we find the analytical shape of the finger, using an extrapolation of the Reinelt-Saffman calculations for a Stokes immiscible flow. Surprisingly, the result is that our finger can be deduced from the celebrated Saffman-Taylor' s one, obtained in a potential flow, by a streching in the flow direction by a numerical factor of 2.125.

  13. Two-dimensional capillary origami

    Energy Technology Data Exchange (ETDEWEB)

    Brubaker, N.D., E-mail: nbrubaker@math.arizona.edu; Lega, J., E-mail: lega@math.arizona.edu

    2016-01-08

    We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid. - Highlights: • Full solution set of the two-dimensional capillary origami problem. • Fluid does not necessarily wet the entire plate. • Global energy approach provides exact differential equations satisfied by minimizers. • Bifurcation diagrams highlight three different regimes. • Conditions for spontaneous encapsulation are identified.

  14. Ultrafast two dimensional infrared chemical exchange spectroscopy

    Science.gov (United States)

    Fayer, Michael

    2011-03-01

    The method of ultrafast two dimensional infrared (2D IR) vibrational echo spectroscopy is described. Three ultrashort IR pulses tuned to the frequencies of the vibrational transitions of interest are directed into the sample. The interaction of these pulses with the molecular vibrational oscillators produces a polarization that gives rise to a fourth pulse, the vibrational echo. The vibrational echo pulse is combined with another pulse, the local oscillator, for heterodyne detection of the signal. For fixed time between the second and third pulses, the waiting time, the first pulse is scanned. Two Fourier transforms of the data yield a 2D IR spectrum. The waiting time is increased, and another spectrum is obtained. The change in the 2D IR spectra with increased waiting time provides information on the time evolution of the structure of the molecular system under observation. In a 2D IR chemical exchange experiment, two species A and B, are undergoing chemical exchange. A's are turning into B's, and B's are turning into A's, but the overall concentrations of the species are not changing. The kinetics of the chemical exchange on the ground electronic state under thermal equilibrium conditions can be obtained 2D IR spectroscopy. A vibration that has a different frequency for the two species is monitored. At very short time, there will be two peaks on the diagonal of the 2D IR spectrum, one for A and one for B. As the waiting time is increased, chemical exchange causes off-diagonal peaks to grow in. The time dependence of the growth of these off-diagonal peaks gives the chemical exchange rate. The method is applied to organic solute-solvent complex formation, orientational isomerization about a carbon-carbon single bond, migration of a hydrogen bond from one position on a molecule to another, protein structural substate interconversion, and water hydrogen bond switching between ions and water molecules. This work was supported by the Air Force Office of Scientific

  15. Brewster Angle Microscope Investigations of Two Dimensional Phase Transitions

    Science.gov (United States)

    Schuman, Adam William

    The liquid-liquid interface is investigated by microscopic and thermodynamic means to image and measure interfacial properties when the system undergoes a two-dimensional (2D) phase transition of a Gibbs monolayer by varying the sample temperature. An in-house Brewster angle microscope (BAM) is constructed to visualize the interface during this transition while a quasi-elastic light scattering technique is used to determine the interfacial tension. These results complement x-ray investigations of the same systems. Evidence of interfacial micro-separated structure, microphases, comes from observations across a hexane-water interface with the inclusion of a long-chain fluorinated alcohol surfactant into the bulk hexane. Microphases take the form of spatially modulated structure to the density of the surfactant as it spans laterally across the interface. The surfactant monolayer exhibits microphase morphology over a range of a couple degrees as the temperature of the system is scanned through the 2D gas-solid phase transition. Microphase structure was observed for heating and cooling the hexane-water system and structural comparisons are given when the temperature step and quench depth of the cooling process is varied. A complete sequence of morphological structure was observed from 2D gas to cluster to labyrinthine stripe to a 2D solid mosaic pattern. Two characteristic length scales emerge giving rise to speculation of an elastic contribution to the standard repulsive and attractive competitive forces stabilizing the microphase. The benefit of BAM to laterally image very thin films across the surface of an interface on the micrometer length scale nicely complements x-ray reflectivity methods that average structural data transverse to the liquid interface on a molecular scale. To properly analyze x-ray reflectivity data, the interface is required to be laterally homogeneous. BAM can sufficiently characterize the interface for this purpose as is done for a Langmuir

  16. Perspective: Two-dimensional resonance Raman spectroscopy

    Science.gov (United States)

    Molesky, Brian P.; Guo, Zhenkun; Cheshire, Thomas P.; Moran, Andrew M.

    2016-11-01

    Two-dimensional resonance Raman (2DRR) spectroscopy has been developed for studies of photochemical reaction mechanisms and structural heterogeneity in complex systems. The 2DRR method can leverage electronic resonance enhancement to selectively probe chromophores embedded in complex environments (e.g., a cofactor in a protein). In addition, correlations between the two dimensions of the 2DRR spectrum reveal information that is not available in traditional Raman techniques. For example, distributions of reactant and product geometries can be correlated in systems that undergo chemical reactions on the femtosecond time scale. Structural heterogeneity in an ensemble may also be reflected in the 2D spectroscopic line shapes of both reactive and non-reactive systems. In this perspective article, these capabilities of 2DRR spectroscopy are discussed in the context of recent applications to the photodissociation reactions of triiodide and myoglobin. We also address key differences between the signal generation mechanisms for 2DRR and off-resonant 2D Raman spectroscopies. Most notably, it has been shown that these two techniques are subject to a tradeoff between sensitivity to anharmonicity and susceptibility to artifacts. Overall, recent experimental developments and applications of the 2DRR method suggest great potential for the future of the technique.

  17. Elastic models of defects in two-dimensional crystals

    Science.gov (United States)

    Kolesnikova, A. L.; Orlova, T. S.; Hussainova, I.; Romanov, A. E.

    2014-12-01

    Elastic models of defects in two-dimensional (2D) crystals are presented in terms of continuum mechanics. The models are based on the classification of defects, which is founded on the dimensionality of the specification region of their self-distortions, i.e., lattice distortions associated with the formation of defects. The elastic field of an infinitesimal dislocation loop in a film is calculated for the first time. The fields of the center of dilatation, dislocation, disclination, and circular inclusion in planar 2D elastic media, namely, nanofilms and graphenes, are considered. Elastic fields of defects in 2D and 3D crystals are compared.

  18. Two dimensional soft material: new faces of graphene oxide.

    Science.gov (United States)

    Kim, Jaemyung; Cote, Laura J; Huang, Jiaxing

    2012-08-21

    Graphite oxide sheets, now called graphene oxide (GO), can be made from chemical exfoliation of graphite by reactions that have been known for 150 years. Because GO is a promising solution-processable precursor for the bulk production of graphene, interest in this old material has resurged. The reactions to produce GO add oxygenated functional groups to the graphene sheets on their basal plane and edges, and this derivatization breaks the π-conjugated network, resulting in electrically insulating but highly water-dispersible sheets. Apart from making graphene, GO itself has many intriguing properties. Like graphene, GO is a two-dimensional (2D) sheet with feature sizes at two abruptly different length scales. The apparent thickness of the functionalized carbon sheet is approximately 1 nm, but the lateral dimensions can range from a few nanometers to hundreds of micrometers. Therefore, researchers can think of GO as either a single molecule or a particle, depending on which length scale is of greater interest. At the same time, GO can be viewed as an unconventional soft material, such as a 2D polymer, highly anisotropic colloid, membrane, liquid crystal, or amphiphile. In this Account, we highlight the soft material characteristics of GO. GO consists of nanographitic patches surrounded by largely disordered, oxygenated domains. Such structural characteristics effectively make GO a 2D amphiphile with a hydrophilic periphery and largely hydrophobic center. This insight has led to better understanding of the solution properties of GO for making thin films and new applications of GO as a surfactant. Changes in pH and sheet size can tune the amphiphilicity of GO, leading to intriguing interfacial activities. In addition, new all-carbon composites made of only graphitic nanostructures using GO as a dispersing agent have potential applications in photovoltaics and energy storage. On the other hand, GO can function as a 2D random diblock copolymer, one block graphitic and

  19. Two-dimensional growth of germanium under a diffusion limited aggregation environment

    Science.gov (United States)

    Lee, Jaejun; Kim, Sung Wook; Park, Youn Ho; Park, Jeong Min; Kim, Yeon Joo; Park, Sangwon; Yang, Jeen Moon; Choi, Heon-Jin

    2017-01-01

    The discovery of graphene has triggered immense interest in two-dimensional (2D) nanomaterials. However, the 2D growth of several layerstructured crystals such as graphene, MoS2, and black phosphorus is difficult and limited. Here, we report the gas-phase 2D growth of germanium (Ge) with a cubic structure to form Ge nanosheets (GeNSs) using the chemical vapor deposition method. Our investigation revealed that a diffusion limited aggregation (DLA) environment is essential for the 2D growth of Ge that induces a dendritic growth in the direction and suppresses the growth in the [111] direction. The growth behavior was similar to the 2D growth of silicon reported previously. Thus, it can be concluded that a DLA environment is essential for the 2D growth of cubic structured materials. The electron density and mobility of GeNSs were found to be 1.3 × 1015 cm-3 and 792 cm2/Vs, respectively, and their resistivity varied with the intensity of light. [Figure not available: see fulltext.

  20. Two-dimensional quantum repeaters

    Science.gov (United States)

    Wallnöfer, J.; Zwerger, M.; Muschik, C.; Sangouard, N.; Dür, W.

    2016-11-01

    The endeavor to develop quantum networks gave rise to a rapidly developing field with far-reaching applications such as secure communication and the realization of distributed computing tasks. This ultimately calls for the creation of flexible multiuser structures that allow for quantum communication between arbitrary pairs of parties in the network and facilitate also multiuser applications. To address this challenge, we propose a two-dimensional quantum repeater architecture to establish long-distance entanglement shared between multiple communication partners in the presence of channel noise and imperfect local control operations. The scheme is based on the creation of self-similar multiqubit entanglement structures at growing scale, where variants of entanglement swapping and multiparty entanglement purification are combined to create high-fidelity entangled states. We show how such networks can be implemented using trapped ions in cavities.

  1. Two-dimensional capillary origami

    Science.gov (United States)

    Brubaker, N. D.; Lega, J.

    2016-01-01

    We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid.

  2. c2d Spitzer IRS spectra of embedded low-mass young stars: gas-phase emission lines

    CERN Document Server

    Lahuis, Fred; Jørgensen, Jes K; Blake, Geoffrey A; Evans, Neal J

    2010-01-01

    A survey of mid-IR gas-phase emission lines of H2, H2O and various atoms toward a sample of 43 embedded low-mass young stars in nearby star-forming regions is presented. The sources are selected from the Spitzer "Cores to Disks" (c2d) legacy program. The environment of embedded protostars is complex both in its physical structure (envelopes, outflows, jets, protostellar disks) and the physical processes (accretion, irradiation by UV and/or X-rays, excitation through slow and fast shocks) which take place. A key point is to spatially resolve the emission in the Spitzer-IRS spectra. An optimal extraction method is used to separate both spatially unresolved (compact, up to a few 100 AU) and spatially resolved (extended, 1000 AU or more) emission from the IRS spectra. The results are compared with the c2d disk sample and literature PDR and shock models to address the physical nature of the sources. Both compact and extended emission features are observed. Warm (Tex few 100 K) H2, observed through the pure rotatio...

  3. Optical Spectroscopy of Two Dimensional Graphene and Boron Nitride

    Science.gov (United States)

    Ju, Long

    This dissertation describes the use of optical spectroscopy in studying the physical properties of two dimensional nano materials like graphene and hexagonal boron nitride. Compared to bulk materials, atomically thin two dimensional materials have a unique character that is the strong dependence of physical properties on external control. Both electronic band structure and chemical potential can be tuned in situ by electric field-which is a powerful knob in experiment. Therefore the optical study at atomic thickness scale can greatly benefit from modern micro-fabrication technique and electric control of the material properties. As will be shown in this dissertation, such control of both gemometric and physical properties enables new possibilities of optical spectroscopic measurement as well as opto-electronic studies. Other experimental techniques like electric transport and scanning tunneling microscopy and spectroscopy are also combined with optical spectroscopy to reveal the physics that is beyond the reach of each individual technique. There are three major themes in the dissertation. The first one is focused on the study of plasmon excitation of Dirac electrons in monolayer graphene. Unlike plasmons in ordinary two dimensional electron gas, plasmons of 2D electrons as in graphene obey unusual scaling laws. We fabricate graphene micro-ribbon arrays with photolithography technique and use optical absorption spectroscopy to study its absorption spectrum. The experimental result demonstrates the extraordinarily strong light-plasmon coupling and its novel dependence on both charge doping and geometric dimensions. This work provides a first glance at the fundamental properties of graphene plasmons and forms the basis of an emerging subfield of graphene research and applications such as graphene terahertz metamaterials. The second part describes the opto-electronic response of heterostructures composed of graphene and hexagonal boron nitride. We found that there is

  4. Use of Comprehensive Two-Dimensional Gas Chromatography with Time-of-Flight Mass Spectrometric Detection and Random Forest Pattern Recognition Techniques for Classifying Chemical Threat Agents and Detecting Chemical Attribution Signatures.

    Science.gov (United States)

    Strozier, Erich D; Mooney, Douglas D; Friedenberg, David A; Klupinski, Theodore P; Triplett, Cheryl A

    2016-07-19

    In this proof of concept study, chemical threat agent (CTA) samples were classified to their sources with accuracies of 87-100% by applying a random forest statistical pattern recognition technique to analytical data acquired by comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometric detection (GC × GC-TOFMS). Three organophosphate pesticides, chlorpyrifos, dichlorvos, and dicrotophos, were used as the model CTAs, with data collected for 4-6 sources per CTA and 7-10 replicate analyses per source. The analytical data were also evaluated to determine tentatively identified chemical attribution signatures for the CTAs by comparing samples from different sources according to either the presence/absence of peaks or the relative responses of peaks. These results demonstrate that GC × GC-TOFMS analysis in combination with a random forest technique can be useful in sample classification and signature identification for pesticides. Furthermore, the results suggest that this combination of analytical chemistry and statistical approaches can be applied to forensic analysis of other chemicals for similar purposes.

  5. Analysis of volatile organic compounds released from the decay of surrogate human models simulating victims of collapsed buildings by thermal desorption-comprehensive two-dimensional gas chromatography-time of flight mass spectrometry.

    Science.gov (United States)

    Agapiou, A; Zorba, E; Mikedi, K; McGregor, L; Spiliopoulou, C; Statheropoulos, M

    2015-07-01

    Field experiments were devised to mimic the entrapment conditions under the rubble of collapsed buildings aiming to investigate the evolution of volatile organic compounds (VOCs) during the early dead body decomposition stage. Three pig carcasses were placed inside concrete tunnels of a search and rescue (SAR) operational field terrain for simulating the entrapment environment after a building collapse. The experimental campaign employed both laboratory and on-site analytical methods running in parallel. The current work focuses only on the results of the laboratory method using thermal desorption coupled to comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (TD-GC×GC-TOF MS). The flow-modulated TD-GC×GC-TOF MS provided enhanced separation of the VOC profile and served as a reference method for the evaluation of the on-site analytical methods in the current experimental campaign. Bespoke software was used to deconvolve the VOC profile to extract as much information as possible into peak lists. In total, 288 unique VOCs were identified (i.e., not found in blank samples). The majority were aliphatics (172), aromatics (25) and nitrogen compounds (19), followed by ketones (17), esters (13), alcohols (12), aldehydes (11), sulfur (9), miscellaneous (8) and acid compounds (2). The TD-GC×GC-TOF MS proved to be a sensitive and powerful system for resolving the chemical puzzle of above-ground "scent of death".

  6. Tile-Based Fisher Ratio Analysis of Comprehensive Two-Dimensional Gas Chromatography Time-of-Flight Mass Spectrometry (GC × GC – TOFMS) Data using a Null Distribution Approach

    Energy Technology Data Exchange (ETDEWEB)

    Parsons, Brendon A.; Marney, Luke C.; Siegler, William C.; Hoggard, Jamin C.; Wright, Bob W.; Synovec, Robert E.

    2015-04-07

    Multi-dimensional chromatographic instrumentation produces information-rich, and chemically complex data containing meaningful chemical signals and/or chemical patterns. Two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC – TOFMS) is a prominent instrumental platform that has been applied extensively for discovery-based experimentation, where samples are sufficiently volatile or amenable to derivatization. Use of GC × GC – TOFMS and associated data analysis strategies aim to uncover meaningful chemical signals or chemical patterns. However, for complex samples, meaningful chemical information is often buried in a background of less meaningful chemical signal and noise. In this report, we utilize the tile-based F-ratio software in concert with the standard addition method by spiking non-native chemicals into a diesel fuel matrix at low concentrations. While the previous work studied the concentration range of 100-1000 ppm, the current study focuses on the 0 ppm to 100 ppm analyte spike range. This study demonstrates the sensitivity and selectivity of the tile-based F-ratio software for discovery of true positives in the non-targeted analysis of a chemically complex and analytically challenging sample matrix. By exploring the low concentration spike levels, we gain a better understanding of the limit of detection (LOD) of the tile-based F-ratio software with GC × GC – TOFMS data.

  7. Ripening-dependent metabolic changes in the volatiles of pineapple (Ananas comosus (L.) Merr.) fruit: I. Characterization of pineapple aroma compounds by comprehensive two-dimensional gas chromatography-mass spectrometry.

    Science.gov (United States)

    Steingass, Christof Björn; Carle, Reinhold; Schmarr, Hans-Georg

    2015-03-01

    Qualitative ripening-dependent changes of pineapple volatiles were studied via headspace solid-phase microextraction and analyzed by comprehensive two-dimensional gas chromatography quadrupole mass spectrometry (HS-SPME-GC×GC-qMS). Early green-ripe stage, post-harvest ripened, and green-ripe fruits at the end of their commercial shelf-life were compared to air-freighted pineapples harvested at full maturity. In total, more than 290 volatiles could be identified by mass spectrometry and their linear retention indices. The majority of compounds comprise esters (methyl and ethyl esters of saturated and unsaturated fatty acids, acetates), terpenes, alcohols, aldehydes, 2-ketones, free fatty acids, and miscellaneous γ- and δ-lactones. The structured separation space obtained by GC×GC allowed revealing various homologous series of compound classes as well as clustering of sesquiterpenes. Post-harvest ripening increased the diversity of the volatile profile compared to both early green-ripe maturity stages and on-plant ripened fruits.

  8. A comparative study of volatile components in green, oolong and black teas by using comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry and multivariate data analysis.

    Science.gov (United States)

    Zhang, Lei; Zeng, Zhongda; Zhao, Chunxia; Kong, Hongwei; Lu, Xin; Xu, Guowang

    2013-10-25

    The difference of volatile components in green, oolong and black teas was studied by using comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS). Simultaneous distillation extraction was proved to be a suitable technique to extract the analytes with interest. A total of 450 compounds were tentatively identified with comparison to the standard mass spectra in available databases, retention index on the first dimension and structured chromatogram. 33 tea samples, including 12, 12 and 9 samples of green, oolong and black tea were analyzed by using GC×GC-TOFMS. After peak alignment, around 3600 peaks were detected. Partial least squares - discriminant analysis and hierarchical cluster analysis were used to classify these samples, then non-parametric hypothesis test (Mann-Whitney U test) and the variable importance in the projection (VIP) were applied to discover the key components to distinguish the three types of tea with significant difference amongst them. 74 differential compounds are defined to interpret the chemical differences of 3 types of tea. This study shows the power of GC×GC-TOFMS method combined with multivariate data analysis to investigate natural products with high complexity for information extraction.

  9. Analysis of organic compounds of water-in-crude oil emulsions separated by microwave heating using comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry.

    Science.gov (United States)

    Freitas, Lisiane S; Von Mühlen, Carin; Bortoluzzi, Janaína H; Zini, Claudia A; Fortuny, Montserrat; Dariva, Claudio; Coutinho, Raquel C C; Santos, Alexandre F; Caramão, Elina B

    2009-04-03

    In this work the higher peak capacity and resolution of comprehensive two-dimensional gas chromatography (GCxGC) has been successfully applied, for the first time, to tentatively identify several polar organic compounds of organic extracts of aqueous phases resulting from microwave demulsification process of water-in-crude oil emulsions. Results have shown that higher temperatures and longer exposure time to microwave irradiation produced water phases with a wider variety of polar organic compounds. The microwave process showed to be suitable for the extraction of several polar compounds classes of petroleum. The proposed microwave extraction method and GCxGC identification of polar compounds of petroleum samples are of practical interest for the petrochemical industry due to corrosion and related problems associated with these polar compounds in refinery equipments. The GCxGC/time-of-flight MS technique shows to be very important in the total separation of different classes of compounds and allows the identification of many compounds in these classes.

  10. Non-targeted analysis of electronics waste by comprehensive two-dimensional gas chromatography combined with high-resolution mass spectrometry: Using accurate mass information and mass defect analysis to explore the data.

    Science.gov (United States)

    Ubukata, Masaaki; Jobst, Karl J; Reiner, Eric J; Reichenbach, Stephen E; Tao, Qingping; Hang, Jiliang; Wu, Zhanpin; Dane, A John; Cody, Robert B

    2015-05-22

    Comprehensive two-dimensional gas chromatography (GC×GC) and high-resolution mass spectrometry (HRMS) offer the best possible separation of their respective techniques. Recent commercialization of combined GC×GC-HRMS systems offers new possibilities for the analysis of complex mixtures. However, such experiments yield enormous data sets that require new informatics tools to facilitate the interpretation of the rich information content. This study reports on the analysis of dust obtained from an electronics recycling facility by using GC×GC in combination with a new high-resolution time-of-flight (TOF) mass spectrometer. New software tools for (non-traditional) Kendrick mass defect analysis were developed in this research and greatly aided in the identification of compounds containing chlorine and bromine, elements that feature in most persistent organic pollutants (POPs). In essence, the mass defect plot serves as a visual aid from which halogenated compounds are recognizable on the basis of their mass defect and isotope patterns. Mass chromatograms were generated based on specific ions identified in the plots as well as region of the plot predominantly occupied by halogenated contaminants. Tentative identification was aided by database searches, complementary electron-capture negative ionization experiments and elemental composition determinations from the exact mass data. These included known and emerging flame retardants, such as polybrominated diphenyl ethers (PBDEs), hexabromobenzene, tetrabromo bisphenol A and tris (1-chloro-2-propyl) phosphate (TCPP), as well as other legacy contaminants such as polychlorinated biphenyls (PCBs) and polychlorinated terphenyls (PCTs).

  11. Chemical fingerprinting of naphthenic acids at an oil sands end pit lake by comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC×GC/TOFMS)

    Science.gov (United States)

    Bowman, D. T.; Arriaga, D.; Morris, P.; Risacher, F.; Warren, L. A.; McCarry, B. E.; Slater, G.

    2016-12-01

    Naphthenic acids (NAs) are naturally occurring in Athabasca oil sands and accumulate in tailings as a result of water-based extraction processes. NAs contribute to the toxicity of tailings and oil sands process-affected water (OSPW). NAs exist as a complex mixture, so the development of an analytical technique to characterize them has been an on-going challenge. The monitoring of individual NAs and their associated isomers through multidimensional chromatography has the potential to provide greater insight into the behavior of NAs in the environment. For NAs whose proportions do not change during environmental processing, NA ratios may provide a means to develop fingerprints characteristic of specific sources. Alternatively, relative changes in the proportions of NAs may provide a tracer of their occurrence and extent of removal. As yet, only a few studies have begun to explore these possibilities. In this study, comprehensive two dimensional gas chromatography/time-of-flight mass spectrometry was used to monitor individual naphthenic acids in an end pit lake in Alberta, Canada. NA profiles from different depths and sampling locations were compared to evaluate the spatial variations at the site.

  12. Quantized conductance doubling and hard gap in a two-dimensional semiconductor-superconductor heterostructure

    DEFF Research Database (Denmark)

    Kjærgaard, Morten; Nichele, F; Suominen, Henri Juhani;

    2016-01-01

    Coupling a two-dimensional (2D) semiconductor heterostructure to a superconductor opens new research and technology opportunities, including fundamental problems in mesoscopic superconductivity, scalable superconducting electronics, and new topological states of matter. One route towards...... topological matter is by coupling a 2D electron gas with strong spin-orbit interaction to an s-wave superconductor. Previous efforts along these lines have been adversely affected by interface disorder and unstable gating. Here we show measurements on a gateable InGaAs/InAs 2DEG with patterned epitaxial Al......, yielding devices with atomically pristine interfaces between semiconductor and superconductor. Using surface gates to form a quantum point contact (QPC), we find a hard superconducting gap in the tunnelling regime. When the QPC is in the open regime, we observe a first conductance plateau at 4e(2)/h...

  13. An extended two-dimensional mathematical model of vertical ring furnaces

    Science.gov (United States)

    Peter, S.; Charette, A.; Bui, R. T.; Tomsett, A.; Potocnik, V.

    1996-04-01

    An extended two-dimensional (2-D+) mathematical model of vertical anode baking furnaces has been developed. The work was motivated by the fact that a previous 2-D model was unable to predict the nonuniform baking in the transverse direction, i.e., perpendicular to the longitudinal axis of the furnace. The modeling strategy based on dividing each section in four zones (underlid, pit, underpit, head wall and fire shaft zones) and introducing two symmetry planes in the exterior pits is explained. The basic heat-transfer relations used are also detailed. Selected results shown include draught and oxygen concentration profiles in the flue, gas and anode temperature distributions and fuel consumption in the back fire ramp. Simulation and experimental results are compared.

  14. A Two-Dimensional Post-Stack Seismic Inversion for Acoustic Impedance of Gas and Hydrate Bearing Deep-Water Sediments Within the Continental Slope of the Ulleung Basin, East Sea, Korea

    Directory of Open Access Journals (Sweden)

    Keumsuk Lee

    2013-01-01

    Full Text Available A post-stack inversion of 2D seismic data was conducted to estimate the spatial distribution of acoustic impedance associated with gas and hydrates in the Ulleung Basin, East Sea, Korea constrained by logs from three boreholes drilled on its continental margin. A model-based inversion was applied to a Plio-Quaternary succession composed of alternations of unconsolidated mass-flow deposits/turbidites. A comparison of seismic reflections and synthetic data computed from impedance logs is shown for two zones. An upper (steep slope zone contains a moderately continuous, possibly bottom-simulating reflector feature along the corresponding section. This feature may be associated with a lithology boundary near a drill site in addition to, or instead of, a stability boundary of gas hydrates (i.e., gas below and hydrates above. The lower (gentle slope zone has locally cross-cutting reflection patterns that are more likely to be attributed to gas- and hydrate-related physical phenomena than to spatiotemporal changes in lithology. This seismic inversion is informative and useful, making a contribution to enhance the interpretability of the seismic profiles for a potential hydrate recovery.

  15. The ionized gas in the central region of NGC 5253. 2D mapping of the physical and chemical properties

    Science.gov (United States)

    Monreal-Ibero, A.; Walsh, J. R.; Vílchez, J. M.

    2012-08-01

    Context. Blue compact dwarf (BCD) galaxies constitute the ideal laboratories to test the interplay between massive star formation and the surrounding gas. As one of the nearest BCD galaxies, NGC 5253 was previously studied with the aim to elucidate in detail the starburst interaction processes. Some open issues regarding the properties of its ionized gas still remain to be addressed. Aims: The 2D structure of the main physical and chemical properties of the ionized gas in the core of NGC 5253 has been studied. Methods: Optical integral field spectroscopy (IFS) data has been obtained with FLAMES Argus and lower resolution gratings of the Giraffe spectrograph. Results: We derived 2D maps for different tracers of electron density (ne), electron temperature (Te) and ionization degree. The maps for ne as traced by [O ii], [S ii], [Fe iii], and [Ar iv] line ratios are compatible with a 3D stratified view of the nebula with the highest ne in the innermost layers and a decrease of ne outwards. 2D maps of Te were measured from [O iii] and [S ii] line ratios; to our knowledge, this is the first time that a Te map based on [S ii] lines for an extragalactic object has been presented. The joint interpretation of the Te([S ii]) and Te([O iii]) maps is consistent with a Te structure in 3D with higher temperatures close to the main ionizing source surrounded by a colder and more diffuse component. The highest ionization degree is found at the peak of emission for the gas with relatively high ionization in the main Giant H ii Region and lower ionization degree delineating the more extended diffuse component. We derived abundances of oxygen, neon, argon, and nitrogen. Abundances for O, Ne and Ar are constant over the mapped area within ≲0.1 dex. The mean 12 + log (O/H) is 8.26 ± 0.04 while the relative abundances of log (N/O), log (Ne/O) and log (Ar/O) were ~-1.32 ± 0.05, -0.65 ± 0.03 and -2.33 ± 0.06, respectively. There are two locations with enhanced N/O. The first (log (N

  16. Vibrational Properties of a Two-Dimensional Silica Kagome Lattice.

    Science.gov (United States)

    Björkman, Torbjörn; Skakalova, Viera; Kurasch, Simon; Kaiser, Ute; Meyer, Jannik C; Smet, Jurgen H; Krasheninnikov, Arkady V

    2016-12-27

    Kagome lattices are structures possessing fascinating magnetic and vibrational properties, but in spite of a large body of theoretical work, experimental realizations and investigations of their dynamics are scarce. Using a combination of Raman spectroscopy and density functional theory calculations, we study the vibrational properties of two-dimensional silica (2D-SiO2), which has a kagome lattice structure. We identify the signatures of crystalline and amorphous 2D-SiO2 structures in Raman spectra and show that, at finite temperatures, the stability of 2D-SiO2 lattice is strongly influenced by phonon-phonon interaction. Our results not only provide insights into the vibrational properties of 2D-SiO2 and kagome lattices in general but also suggest a quick nondestructive method to detect 2D-SiO2.

  17. Emergent elemental two-dimensional materials beyond graphene

    Science.gov (United States)

    Zhang, Yuanbo; Rubio, Angel; Le Lay, Guy

    2017-02-01

    Two-dimensional (2D) materials may offer the ultimate scaling beyond the 5 nm gate length. The difficulty of reliably opening a band gap in graphene has led to the search for alternative, semiconducting 2D materials. Emerging classes of elemental 2D materials stand out for their compatibility with existing technologies and/or for their diverse, tunable electronic structures. Among this group, black phosphorene has recently shown superior semiconductor performances. Silicene and germanene feature Dirac-type band dispersions, much like graphene. Calculations show that most group IV and group V elements have one or more stable 2D allotropes, with properties potentially suitable for electronic and optoelectronic applications. Here, we review the advances in these fascinating elemental 2D materials and discuss progress and challenges in their applications in future opto- and nano-electronic devices.

  18. Computationally Driven Two-Dimensional Materials Design: What Is Next?

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Jie [Materials Science; Lany, Stephan [Materials Science; Qi, Yue [Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, Michigan 48824, United States

    2017-07-17

    Two-dimensional (2D) materials offer many key advantages to innovative applications, such as spintronics and quantum information processing. Theoretical computations have accelerated 2D materials design. In this issue of ACS Nano, Kumar et al. report that ferromagnetism can be achieved in functionalized nitride MXene based on first-principles calculations. Their computational results shed light on a potentially vast group of materials for the realization of 2D magnets. In this Perspective, we briefly summarize the promising properties of 2D materials and the role theory has played in predicting these properties. In addition, we discuss challenges and opportunities to boost the power of computation for the prediction of the 'structure-property-process (synthesizability)' relationship of 2D materials.

  19. Classifying Two-dimensional Hyporeductive Triple Algebras

    CERN Document Server

    Issa, A Nourou

    2010-01-01

    Two-dimensional real hyporeductive triple algebras (h.t.a.) are investigated. A classification of such algebras is presented. As a consequence, a classification of two-dimensional real Lie triple algebras (i.e. generalized Lie triple systems) and two-dimensional real Bol algebras is given.

  20. Correlation of rocket propulsion fuel properties with chemical composition using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry followed by partial least squares regression analysis

    Energy Technology Data Exchange (ETDEWEB)

    Kehimkar, Benjamin; Hoggard, Jamin C.; Marney, Luke C.; Billingsley, Matthew; Fraga, Carlos G.; Bruno, Thomas J.; Synovec, Robert E.

    2014-01-31

    There is an increased need to more fully assess and control the composition of kerosene based rocket propulsion fuels, namely RP-1 and RP-2. In particular, it is crucial to be able to make better quantitative connections between the following three attributes: (a) fuel performance, (b) fuel properties (flash point, density, kinematic viscosity, net heat of combustion, hydrogen content, etc) and (c) the chemical composition of a given fuel (i.e., specific chemical compounds and compound classes present as a result of feedstock blending and processing). Indeed, recent efforts in predicting fuel performance through modeling put greater emphasis on detailed and accurate fuel properties and fuel compositional information. In this regard, advanced distillation curve (ADC) metrology provides improved data relative to classical boiling point and volatility curve techniques. Using ADC metrology, data obtained from RP-1 and RP-2 fuels provides compositional variation information that is directly relevant to predictive modeling of fuel performance. Often, in such studies, one-dimensional gas chromatography (GC) combined with mass spectrometry (MS) is typically employed to provide chemical composition information. Building on approaches using GC-MS, but to glean substantially more chemical composition information from these complex fuels, we have recently studied the use of comprehensive two dimensional gas chromatography combined with time-of-flight mass spectrometry (GC × GC - TOFMS) to provide chemical composition data that is significantly richer than that provided by GC-MS methods. In this report, by applying multivariate data analysis techniques, referred to as chemometrics, we are able to readily model (correlate) the chemical compositional information from RP-1 and RP-2 fuels provided using GC × GC - TOFMS, to the fuel property information such as that provided by the ADC method and other specification properties. We anticipate that this new chemical analysis