A study of two-dimensional magnetic polaron
LIU; Tao; ZHANG; Huaihong; FENG; Mang; WANG; Kelin
2006-01-01
By using the variational method and anneal simulation, we study in this paper the self-trapped magnetic polaron (STMP) in two-dimensional anti-ferromagnetic material and the bound magnetic polaron (BMP) in ferromagnetic material. Schwinger angular momentum theory is applied to changing the problem into a coupling problem of carriers and two types of Bosons. Our calculation shows that there are single-peak and multi-peak structures in the two-dimensional STMP. For the ferromagnetic material, the properties of the two-dimensional BMP are almost the same as that in one-dimensional case; but for the anti-ferromagnetic material, the two-dimensional STMP structure is much richer than the one-dimensional case.
Torque magnetometry studies of two-dimensional electron systems
Schaapman, Maaike Ruth
2004-01-01
This thesis describes a study of the magnetization two-dimensional electron gases (2DEGs). To detect the typically small magnetization, a sensitive magnetometer with optical angular detection was developed. The magnetometer uses a quadrant detector to measure the rotation of the sample. By mounting
Torque magnetometry studies of two-dimensional electron systems
Schaapman, Maaike Ruth
2004-01-01
This thesis describes a study of the magnetization two-dimensional electron gases (2DEGs). To detect the typically small magnetization, a sensitive magnetometer with optical angular detection was developed. The magnetometer uses a quadrant detector to measure the rotation of the sample. By mounting
Two-dimensional correlation spectroscopy in polymer study
Park, Yeonju; Noda, Isao; Jung, Young Mee
2015-01-01
This review outlines the recent works of two-dimensional correlation spectroscopy (2DCOS) in polymer study. 2DCOS is a powerful technique applicable to the in-depth analysis of various spectral data of polymers obtained under some type of perturbation. The powerful utility of 2DCOS combined with various analytical techniques in polymer studies and noteworthy developments of 2DCOS used in this field are also highlighted. PMID:25815286
Statistical study of approximations to two dimensional inviscid turbulence
Glaz, H.M.
1977-09-01
A numerical technique is developed for studying the ergodic and mixing hypotheses for the dynamical systems arising from the truncated Fourier transformed two-dimensional inviscid Navier-Stokes equations. This method has the advantage of exactly conserving energy and entropy (i.e., total vorticity) in the inviscid case except for numerical error in solving the ordinary differential equations. The development of the mathematical model as an approximation to a real physical (turbulent) flow and the numerical results obtained are discussed.
Numerical Study of Two-Dimensional Viscous Flow over Dams
王利兵; 刘宇陆; 涂敏杰
2003-01-01
In this paper, the characteristics of two-dimensional viscous flow over two dams were numerically investigated. The results show that the behavior of the vortices is closely related to the space between two dams, water depth, Fr number and Reynolds number. In addition, the flow properties behind each dam are different, and the changes over two dams are more complex than over one dam. Finally, the relevant turbulent characteristics were analyzed.
Two-dimensional transport study of scrape off layer plasmas
Yamamoto, Nobuyuki [Interdisciplinary Graduate School of Advanced Energy Engineering Sciences, Kyushu University, Fukuoka (Japan); Yagi, Masatoshi; Itoh, Sanae-I. [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics
1999-09-01
Two-dimensional transport code is developed to analyzed the heat pulse propagation in the scrape-off layer plasma. The classical and anomalous transport models are considered as a thermal diffusivity perpendicular to the magnetic field. On the other hand, the classical transport model is chosen as a thermal diffusivity parallel to the magnetic field. The heat deposition profiles are evaluated for various kinds of transport models. It is found that the heat pulse which arrives at the divertor plate due to the classical transport is largest compared with other models. The steady state temperate profiles of the electron and ion are also discussed. (author)
Sequentially generated states for the study of two dimensional systems
Banuls, Mari-Carmen; Cirac, J. Ignacio [Max-Planck-Institut fuer Quantenoptik, Garching (Germany); Perez-Garcia, David [Depto. Analisis Matematico, Universidad Complutense de Madrid (Spain); Wolf, Michael M. [Niels Bohr Institut, Copenhagen (Denmark); Verstraete, Frank [Fakultaet fuer Physik, Universitaet Wien (Austria)
2009-07-01
The family of Matrix Product States represents a powerful tool for the study of physical one-dimensional quantum many-body systems, such as spin chains. Besides, Matrix Product States can be defined as the family of quantum states that can be sequentially generated in a one-dimensional system. We have introduced a new family of states which extends this sequential definition to two dimensions. Like in Matrix Product States, expectation values of few body observables can be efficiently evaluated and, for the case of translationally invariant systems, the correlation functions decay exponentially with the distance. We show that such states are a subclass of Projected Entangled Pair States and investigate their suitability for approximating the ground states of local Hamiltonians.
Theoretical and experimental study of the normal modes in a coupled two-dimensional system
Giménez, Marcos H; Gómez-Tejedor, José Antonio; Velazquez, Luisberis; Monsoriu, Juan A
2016-01-01
In this work, the normal modes of a two-dimensional oscillating system have been studied from a theoretical and experimental point of view. The normal frequencies predicted by the Hessian matrix for a coupled two-dimensional particle system are compared to those obtained for a real system consisting of two oscillating smartphones coupled one to the other by springs. Experiments are performed on an air table in order to remove the friction forces. The oscillation data are captured by the acceleration sensor of the smartphones and exported to file for further analysis. The experimental frequencies compare reasonably well with the theoretical predictions, namely, within 1.7 % of discrepancy.
Tuset-Sanchis, Luis; Castro-Palacio, Juan C.; Gómez-Tejedor, José A.; Manjón, Francisco J.; Monsoriu, Juan A.
2015-01-01
A smartphone acceleration sensor is used to study two-dimensional harmonic oscillations. The data recorded by the free android application, Accelerometer Toy, is used to determine the periods of oscillation by graphical analysis. Different patterns of the Lissajous curves resulting from the superposition of harmonic motions are illustrated for…
A δ-function-like peak in the specific heat of two-dimensional vortex lattice： Monte carlo study
梁彦天; 曹义刚; 焦正宽
2002-01-01
A repulsive vortex-vortex interaction model was used to numerically study the melting transition of the two-dimensional vortex system with Monte Carlo method. Then a δ-function-like peak in the specific heat was observed and the internal energy showed a sharp drop at the melting temperature, whieh indicated that there exists a first-order melting transition at finite temperatures. The Lindemarm criterion was also investigated and valid, but different from previous simulation results.
Analytical Studies of Two-Dimensional Channel Turbulent Flow Subjected to Coriolis Force
鬼頭, 修己; 中林, 功一; キトウ, オサミ; Kito, Osami
1992-01-01
Coriolis effects on fully developed turbulent flow in a two-dimensional channel rotating about an axis perpendicular to its axis are considered. The Coriolis force has stabilizing/destabilizing effects on turbulence, and the mean velocity distribution changes accordingly. Experimental and numerical studies on the velocity characteristics have already been conducted by other researchers for various conditions. However, we cannot assemble the overall picture of the Coriolis effect on the veloci...
Studies of two-dimensional MoGe superconductors in a magnetic field
Kapitulnik, A. (Stanford Univ., CA (United States). Dept. of Applied Physics); Yazdani, A. (Stanford Univ., CA (United States). Dept. of Applied Physics); Urbach, J.S. (Stanford Univ., CA (United States). Dept. of Applied Physics); White, W.R. (Stanford Univ., CA (United States). Dept. of Applied Physics); Beasley, M.R. (Stanford Univ., CA (United States). Dept. of Applied Physics)
1994-03-01
The H-T phase diagram of two-dimensional amorphous MoGe superconductors is studied near H[sub c2] and near the melting line of the vortex lattice. Good agreement with the lowest Landau level approximation is found for the broadening of the specific heat in a field. We also find that melting of the vortex lattice can be observed only on short enough length scales, shorter than the disorder-mediated lattice correlation length. (orig.)
First-principles study of two-dimensional van der Waals heterojunctions
Hu, Wei; Yang, Jinlong
2015-01-01
Research on graphene and other two-dimensional (2D) materials, such as silicene, germanene, phosphorene, hexagonal boron nitride (h-BN), graphitic carbon nitride (g-C3N4), graphitic zinc oxide (g-ZnO) and molybdenum disulphide (MoS2), has recently received considerable interest owing to their outstanding properties and wide applications. Looking beyond this field, combining the electronic structures of 2D materials in ultrathin van der Waals heterojunctions has also emerged to widely study th...
Numerical Study of Two-Dimensional Volterra Integral Equations by RDTM and Comparison with DTM
Reza Abazari
2013-01-01
Full Text Available The two-dimensional Volterra integral equations are solved using more recent semianalytic method, the reduced differential transform method (the so-called RDTM, and compared with the differential transform method (DTM. The concepts of DTM and RDTM are briefly explained, and their application to the two-dimensional Volterra integral equations is studied. The results obtained by DTM and RDTM together are compared with exact solution. As an important result, it is depicted that the RDTM results are more accurate in comparison with those obtained by DTM applied to the same Volterra integral equations. The numerical results reveal that the RDTM is very effective, convenient, and quite accurate compared to the other kind of nonlinear integral equations. It is predicted that the RDTM can be found widely applicable in engineering sciences.
Substrate influence on two-dimensional solids and liquids: A Monte Carlo simulation study
Vives, E.; Lindgård, Per-Anker
1991-01-01
A general model for two-dimensional solids and liquids on a substrate is studied by means of Monte Carlo simulation. The results can be applied to the case of adsorbed atoms or molecules on surfaces as well as intercalated compounds. We have focused on the study of the melting of a commensurate...... square-root 3 X square-root 3 structure on a triangular lattice with 1/3 coverage. The evolution of the energy, order parameters, and structure factor has been followed in a wide range of temperatures and substrate-potential strengths. The phase diagram exhibits a broad transition region between...
Numerical and experimental study of Lamb wave propagation in a two-dimensional acoustic black hole
Yan, Shiling; Lomonosov, Alexey M.; Shen, Zhonghua
2016-06-01
The propagation of laser-generated Lamb waves in a two-dimensional acoustic black-hole structure was studied numerically and experimentally. The geometrical acoustic theory has been applied to calculate the beam trajectories in the region of the acoustic black hole. The finite element method was also used to study the time evolution of propagating waves. An optical system based on the laser-Doppler vibration method was assembled. The effect of the focusing wave and the reduction in wave speed of the acoustic black hole has been validated.
Simulation study of scalings in scrape-off layer plasma by two-dimensional transport code
Itoh, S.-I.; Ueda, Noriaki; Itoh, Kimitaka (National Inst. for Fusion Science, Nagoya (Japan))
1990-07-01
Scrape-off Layer (SOL) plasma and divertor plasma in Tokamaks were numerically analyzed using a two-dimensional time-dependent transport code (UEDA code). Plasma transport in the SOL and the divertor region was studied for given particle and heat sources from the main plasma. A scaling study of the density, the temperature and their fall-off lengths was carried out for the JFT-2M Tokamak. The results show the inter-relations between the divertor plasma parameters and core plasma confinement. The operational conditions of the core necessary to guarantee the divertor performance are discussed. (author).
Ko, Malcolm K. W.; Weisenstein, Debra K.; Sze, Nein Dak; Shia, Run-Lie; Rodriguez, Jose M.; Heisey, Curtis
1991-01-01
The AER two-dimensional chemistry-transport model is used to study the effect of supersonic and subsonic aircraft operation in the 2010 atmosphere on stratospheric ozone (O3). The results show that: (1) the calculated O3 response is smaller in the 2010 atmosphere compared to previous calculations performed in the 1980 atmosphere; (2) with the emissions provided, the calculated decrease in O3 column is less than 1 percent; and (3) the effect of model grid resolution on O3 response is small provided that the physics is not modified.
Song Gao; Hui Xiang; Bo Xu; Yi-Dong Xia; Jiang Yin; Zhi-Guo Liu
2016-01-01
The carrier mobility of two-dimensional tetragonal carbon allotrope (T-CA) from porous graphene is investigated by first-principles calculations.T-CA can be constructed from divacancy and Stone-Thrower-Wales defects from graphene.T-CA is a direct semiconductor with a band gap of 0.4 eV at Γ point.T-CA possesses a high carrier mobility of the order of 104 cm2 V-1s-1.As our study demonstrates,T-CA has potential applications for next-generation electronic materials.
Numerical study for the c-dependence of fractal dimension in two-dimensional quantum gravity
Kawamoto, N; Kawamoto, Noboru; Yotsuji, Kenji
2002-01-01
We numerically investigate the fractal structure of two-dimensional quantum gravity coupled to matter central charge c for $-2 \\leq c \\leq 1$. We reformulate Q-state Potts model into the model which can be identified as a weighted percolation cluster model and can make continuous change of Q, which relates c, on the dynamically triangulated lattice. The c-dependence of the critical coupling is measured from the percolation probability and susceptibility. The c-dependence of the string susceptibility of the quantum surface is evaluated and has very good agreement with the theoretical predictions. The c-dependence of the fractal dimension based on the finite size scaling hypothesis is measured and has excellent agreement with one of the theoretical predictions previously proposed except for the region near $c\\approx 1$.
Butkus, Vytautas; Augulis, Ramūnas; Gall, Andrew; Büchel, Claudia; Robert, Bruno; Zigmantas, Donatas; Valkunas, Leonas; Abramavicius, Darius
2015-01-01
The energy transfer processes and coherent phenomena in the fucoxanthin-chlorophyll protein complex, which is responsible for the light harvesting function in marine algae diatoms, were investigated at 77 K by using two-dimensional electronic spectroscopy. Experiments performed on the femtosecond and picosecond timescales led to separation of spectral dynamics, witnessing evolutions of coherence and population states of the system in the spectral region of ${\\rm Q}_{y}$ transitions of chlorophylls $a$ and $c$. Analysis of the coherence dynamics allowed us to identify chlorophyll (Chl) $a$ and fucoxanthin intramolecular vibrations dominating over the first few picoseconds. Closer inspection of the spectral region of the ${\\rm Q}_{y}$ transition of Chl $c$ revealed previously not identified mutually non-interacting chlorophyll $c$ states participating in femtosecond or picosecond energy transfer to the Chl $a$ molecules. Consideration of separated coherent and incoherent dynamics allowed us to hypothesize the v...
Butkus, Vytautas; Gelzinis, Andrius; Augulis, Ramūnas; Gall, Andrew; Büchel, Claudia; Robert, Bruno; Zigmantas, Donatas; Valkunas, Leonas; Abramavicius, Darius
2015-06-07
Energy transfer processes and coherent phenomena in the fucoxanthin-chlorophyll protein complex, which is responsible for the light harvesting function in marine algae diatoms, were investigated at 77 K by using two-dimensional electronic spectroscopy. Experiments performed on femtosecond and picosecond timescales led to separation of spectral dynamics, witnessing evolutions of coherence and population states of the system in the spectral region of Qy transitions of chlorophylls a and c. Analysis of the coherence dynamics allowed us to identify chlorophyll (Chl) a and fucoxanthin intramolecular vibrations dominating over the first few picoseconds. Closer inspection of the spectral region of the Qy transition of Chl c revealed previously not identified, mutually non-interacting chlorophyll c states participating in femtosecond or picosecond energy transfer to the Chl a molecules. Consideration of separated coherent and incoherent dynamics allowed us to hypothesize the vibrations-assisted coherent energy transfer between Chl c and Chl a and the overall spatial arrangement of chlorophyll molecules.
Novel two-dimensional silicon and germanium allotropes: a first-principles study
Gimbert, Florian; Lee, Chi-Cheng; Friedlein, Rainer; Fleurence, Antoine; Yamada-Takamura, Yukiko; Ozaki, Taisuke
2014-03-01
Graphene has been extensively studied but its integration into Si-based device technologies is difficult. It has been recently predicted by first-principles calculations that freestanding silicene and germanene, the counterparts of graphene made of Si and Ge atoms respectively, have graphene-like electronic structure with a low buckled structure. So far, the models predicted by first-principles calculations were not able to describe completely the experimental results. These difficulties tend to suggest a more complex phase diagram for freestanding silicene or for silicene on a substrate than the simple buckled phase. We report for the first time a novel two-dimensional silicon and germanium allotropes, with a structure similar of that of MoS2 layer. After investigating a large range of lattice constants by first-principles calculations with OpenMX code, we show that this structure is the ground state for freestanding two-dimensional silicon and germanium layers instead of the usually considered low buckled silicene and germanene.
Ab initio thermodynamic study on two-dimensional atomic nucleation on ZnO polar surfaces
Zhu, Rui; Zhao, Qing; Xu, Jun; Liu, Banggui; Leprince-Wang, Yamin; Yu, Dapeng
2017-08-01
Structures of the two-dimensional atomic nuclei on ZnO (0001)-Zn and (000 1 bar)-O polar surfaces were studied by first principles density functional theory. The polarity-dependent nucleation dynamics was investigated by simulating two-dimensional (2D) nuclei consisting of 1-8 ZnO monomers on both polar surfaces. According to total energy calculations, average binding energy per ZnO monomer of the surface nuclei was analyzed to investigate if the nucleation and growth will proceed reasonably in physics. We found nucleation on (0001)-Zn surface was easier than that on (000 1 bar)-O surface. By using atomistic thermodynamics analysis, we calculated the Gibbs free energy of formation of these nuclei and made a comparison between the two polar surfaces. On (0001)-Zn surface, the critical Gibbs free energy of formation is much lower than that on (000 1 bar)-O surface under the same supersaturation, which leads to a much larger ZnO growth rate and rougher morphology, in accordance with experimental results. In addition, energetic analysis of nucleation at real thermodynamic conditions was achieved by introducing the temperature- and pressure-dependent chemical potentials of ZnO precursors.
Xi, Caiping; Zhang, Shunning; Xiong, Gang; Zhao, Huichang
2016-07-01
Multifractal detrended fluctuation analysis (MFDFA) and multifractal detrended moving average (MFDMA) algorithm have been established as two important methods to estimate the multifractal spectrum of the one-dimensional random fractal signal. They have been generalized to deal with two-dimensional and higher-dimensional fractal signals. This paper gives a brief introduction of the two-dimensional multifractal detrended fluctuation analysis (2D-MFDFA) and two-dimensional multifractal detrended moving average (2D-MFDMA) algorithm, and a detailed description of the application of the two-dimensional fractal signal processing by using the two methods. By applying the 2D-MFDFA and 2D-MFDMA to the series generated from the two-dimensional multiplicative cascading process, we systematically do the comparative analysis to get the advantages, disadvantages and the applicabilities of the two algorithms for the first time from six aspects such as the similarities and differences of the algorithm models, the statistical accuracy, the sensitivities of the sample size, the selection of scaling range, the choice of the q-orders and the calculation amount. The results provide a valuable reference on how to choose the algorithm from 2D-MFDFA and 2D-MFDMA, and how to make the schemes of the parameter settings of the two algorithms when dealing with specific signals in practical applications.
Nebija, D; Noe, C R; Lachmann, B
2015-08-01
Medicinal products obtained by recombinant DNA technology are complex molecules and demonstrate a high degree of molecular heterogeneity. Charge heterogeneity and isoform pattern of this class of medicines, are parameters important for their quality, safety, and efficacy. In this study we report the application of two-dimensional gel electrophoresis (2-D electrophoresis) for the quality assessment, identification, charge heterogeneity and isoform pattern study of recombinant protein, CTLA4-Ig (abatacept), which has been selected as an example of the drug class, known as Fc-fusion proteins. In order to achieve an efficient separation of this complex analyte,2-D electrophoresis was optimized employing different experimental conditions regarding the selection of an immobilized pH gradient (IPG), sample pretreatment, presentation and detection procedure. Experimental datadocumented that 2-D electrophoresis is a suitable method for the assessment of identity, purity, structural integrity, isoform pattern and to monitor charge heterogeneity and post-translational glycosylation of the Fc-fusion protein, abatacept.
Pairing in the two-dimensional Hubbard model: An exact diagonalization study
Lin, H. Q.; Hirsch, J. E.; Scalapino, D. J.
1988-05-01
We have studied the pair susceptibilities for all possible pair wave functions that fit on a two-dimensional (2D) eight-site Hubbard cluster by exact diagonalization of the Hamiltonian. Band fillings corresponding to four and six electrons were studied (two or four holes in the half-filled band) for a wide range of Hubbard interaction strengths and temperatures. Our results show that all pairing susceptibilities are suppressed by the Hubbard repulsion. We have also carried out perturbation-theory calculations which show that the leading-order U2 contributions to the d-wave pair susceptibility suppresses d-wave pairing over a significant temperature range. These results are consistent with recent Monte Carlo results and provide further evidence suggesting that the 2D Hubbard model does not exhibit superconductivity.
Experimental study on two-dimensional film flow with local measurement methods
Yang, Jin-Hwa, E-mail: evo03@snu.ac.kr [Nuclear Thermal-Hydraulic Engineering Laboratory, Seoul National University, Gwanak 599, Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of); Korea Atomic Energy Research Institute, 989-111, Daedeok-daero, Yuseong-gu, Daejeon 305-600 (Korea, Republic of); Cho, Hyoung-Kyu [Nuclear Thermal-Hydraulic Engineering Laboratory, Seoul National University, Gwanak 599, Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of); Kim, Seok [Korea Atomic Energy Research Institute, 989-111, Daedeok-daero, Yuseong-gu, Daejeon 305-600 (Korea, Republic of); Euh, Dong-Jin, E-mail: djeuh@kaeri.re.kr [Korea Atomic Energy Research Institute, 989-111, Daedeok-daero, Yuseong-gu, Daejeon 305-600 (Korea, Republic of); Park, Goon-Cherl [Nuclear Thermal-Hydraulic Engineering Laboratory, Seoul National University, Gwanak 599, Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of)
2015-12-01
Highlights: • An experimental study on the two-dimensional film flow with lateral air injection was performed. • The ultrasonic thickness gauge was used to measure the local liquid film thickness. • The depth-averaged PIV (Particle Image Velocimetry) method was applied to measure the local liquid film velocity. • The uncertainty of the depth-averaged PIV was quantified with a validation experiment. • Characteristics of two-dimensional film flow were classified following the four different flow patterns. - Abstract: In an accident condition of a nuclear reactor, multidimensional two-phase flows may occur in the reactor vessel downcomer and reactor core. Therefore, those have been regarded as important issues for an advanced thermal-hydraulic safety analysis. In particular, the multi-dimensional two-phase flow in the upper downcomer during the reflood phase of large break loss of coolant accident appears with an interaction between a downward liquid and a transverse gas flow, which determines the bypass flow rate of the emergency core coolant and subsequently, the reflood coolant flow rate. At present, some thermal-hydraulic analysis codes incorporate multidimensional modules for the nuclear reactor safety analysis. However, their prediction capability for the two-phase cross flow in the upper downcomer has not been validated sufficiently against experimental data based on local measurements. For this reason, an experimental study was carried out for the two-phase cross flow to clarify the hydraulic phenomenon and provide local measurement data for the validation of the computational tools. The experiment was performed in a 1/10 scale unfolded downcomer of Advanced Power Reactor 1400 (APR1400). Pitot tubes, a depth-averaged PIV method and ultrasonic thickness gauge were applied for local measurement of the air velocity, the liquid film velocity and the liquid film thickness, respectively. The uncertainty of the depth-averaged PIV method for the averaged
Ionothermal Synthesis and Magnetic Studies of Novel Two-Dimensional Metal-Formate Frameworks
Calderone, P.; Feygenson, M.; Forster, P.M.; Borkowski, L.A.; Teat, S.J. Aronson, M.C.; Parise, J.B.
2011-03-21
Five novel two-dimensional frameworks containing formate-bridged metal-centered octahedra are synthesized ionothermally from two ionic liquids previously unused as solvents in hybrid synthesis, 2-hydroxyethylammonium (HEA) formate, and 1-hydroxy-3-proplyammonium (HPA) formate. Templating effects of the cation from each ionic liquid drive the formation of different structures. [NH{sub 3}C{sub 2}H{sub 4}OH]{sub 2}[M(CHO{sub 2}){sub 4}] (1: M = Co, 2: M = Ni) exhibit the same stoichiometry and connectivity as their manganese analogue (3: M = Mn), but the manganese form exhibits a different topology from 1 and 2. [NH{sub 3}C{sub 3}H6OH][M(CHO{sub 2}){sub 3}(H{sub 2}O)] (4: M = Co, 5: M = Mn) were synthesized using the HPA formate ionic liquid with a metal-formate connectivity related to those of 1-3. Canted antiferromagnetic ordering occurs at low temperatures (1: T{sub N} = 7.0 K, 2: T{sub N} = 4.6 K, 3: T{sub N} = 8.0 K, 4: T{sub N} = 7.0 K, 5: T{sub N} = 9.2 K), similar to the magnetic properties previously reported for other metal-formate hybrid materials.
Ionothermal synthesis and magnetic studies of novel two-dimensional metal-formate frameworks.
Calderone, Paul J; Forster, Paul M; Borkowski, Lauren A; Teat, Simon J; Feygenson, Mikhail; Aronson, Meigan C; Parise, John B
2011-03-21
Five novel two-dimensional frameworks containing formate-bridged metal-centered octahedra are synthesized ionothermally from two ionic liquids previously unused as solvents in hybrid synthesis, 2-hydroxyethylammonium (HEA) formate, and 1-hydroxy-3-proplyammonium (HPA) formate. Templating effects of the cation from each ionic liquid drive the formation of different structures. [NH(3)C(2)H(4)OH](2)[M(CHO(2))(4)] (1: M = Co, 2: M = Ni) exhibit the same stoichiometry and connectivity as their manganese analogue (3: M = Mn), but the manganese form exhibits a different topology from 1 and 2. [NH(3)C(3)H(6)OH][M(CHO(2))(3)(H(2)O)] (4: M = Co, 5: M = Mn) were synthesized using the HPA formate ionic liquid with a metal-formate connectivity related to those of 1-3. Canted antiferromagnetic ordering occurs at low temperatures (1: T(N) = 7.0 K, 2: T(N) = 4.6 K, 3: T(N) = 8.0 K, 4: T(N) = 7.0 K, 5: T(N) = 9.2 K), similar to the magnetic properties previously reported for other metal-formate hybrid materials.
Kunal Pathak
2016-09-01
Full Text Available The calcium signaling plays a crucial role in expansion and contraction of cardiac myocytes. This calcium signaling is achieved by calcium diffusion, buffering mechanisms and influx in cardiac myocytes. The various calcium distribution patterns required for achieving calcium signaling in myocytes are still not well understood. In this paper an attempt has been made to develop a model of calcium distribution in myocytes incorporating diffusion of calcium, point source and excess buffer approximation. The model has been developed for a two dimensional unsteady state case. Appropriate boundary conditions and initial condition have been framed. The finite element method has been employed to obtain the solution. The numerical results have been used to study the effect of buffers and source amplitude on calcium distribution in myocytes.
Numerical simulations of Kelvin-Helmholtz instability: a two-dimensional parametric study
Tian, Chunlin
2016-01-01
Using two-dimensional simulations, we numerically explore the dependences of Kelvin-Helmholtz instability upon various physical parameters, including viscosity, width of sheared layer, flow speed, and magnetic field strength. In most cases, a multi-vortex phase exists between the initial growth phase and final single-vortex phase. The parametric study shows that the evolutionary properties, such as phase duration and vortex dynamics, are generally sensitive to these parameters except in certain regimes. An interesting result is that for supersonic flows, the phase durations and saturation of velocity growth approach constant values asymptotically as the sonic Mach number increases. We confirm that the linear coupling between magnetic field and Kelvin-Helmholtz modes is negligible if the magnetic field is weak enough. The morphological behaviour suggests that the multi-vortex coalescence might be driven by the underlying wave-wave interaction. Based on these results, we make a preliminary discussion about seve...
Wind Tunnel Study on Flows over Various Two-dimensional Idealized Urban-liked Surfaces
Ho, Yat-Kiu; Liu, Chun-Ho
2013-04-01
Extensive human activities (e.g. increased traffic emissions) emit a wide range of pollutants resulting in poor urban area air quality. Unlike open, flat and homogenous rural terrain, urban surface is complicated by the presence of buildings, obstacles and narrow streets. The irregular urban surfaces thus form a random roughness that further modifies the near-surface flows and pollutant dispersion. In this study, a physical modelling approach is employed to commence a series of wind tunnel experiments to study the urban-area air pollution problems. The flow characteristics over different hypothetical urban roughness surfaces were studied in a wind tunnel in isothermal conditions. Preliminary experiments were conducted based on six types of idealized two-dimensional (2D) street canyon models with various building-height-to-street-width (aspect) ratios (ARs) 1, 1/2, 1/4, 1/8, 1/10 and 1/12. The main instrumentation is an in-house 90o X-hotwire anemometry. In each set of configuration, a sampling street canyon was selected near the end of the streamwise domain. Its roof level, i.e. the transverse between the mid points of the upstream and downstream buildings, was divided into eight segments. The measurements were then recorded on the mid-plane of the spannwise domain along the vertical profile (from building roof level to the ceiling of wind tunnel) of the eight segments. All the data acquisition processes were handled by the NI data acquisition modules, NI 9239 and CompactDAQ-9188 hardware. Velocity calculation was carried out in the post-processing stage on a digital computer. The two-component flow velocities and velocity fluctuations were calculated at each sampling points, therefore, for each model, a streamwise average of eight vertical profiles of mean velocity and velocity fluctuations was presented. A plot of air-exchange rate (ACH) against ARs was also presented in order to examine the ventilation performance of different tested models. Preliminary results
Butkus, Vytautas; Gelzinis, Andrius; Valkunas, Leonas [Department of Theoretical Physics, Faculty of Physics, Vilnius University, Sauletekio Ave. 9-III, 10222 Vilnius (Lithuania); Center for Physical Sciences and Technology, Savanoriu Ave. 231, 02300 Vilnius (Lithuania); Augulis, Ramūnas [Center for Physical Sciences and Technology, Savanoriu Ave. 231, 02300 Vilnius (Lithuania); Gall, Andrew; Robert, Bruno [Institut de Biologie et Technologies de Saclay, Bât 532, Commissariat à l’Energie Atomique Saclay, 91191 Gif sur Yvette (France); Büchel, Claudia [Institut für Molekulare Biowissenschaften, Universität Frankfurt, Max-von-Laue-Straße 9, Frankfurt (Germany); Zigmantas, Donatas [Department of Chemical Physics, Lund University, P.O. Box 124, 22100 Lund (Sweden); Abramavicius, Darius, E-mail: darius.abramavicius@ff.vu.lt [Department of Theoretical Physics, Faculty of Physics, Vilnius University, Sauletekio Ave. 9-III, 10222 Vilnius (Lithuania)
2015-06-07
Energy transfer processes and coherent phenomena in the fucoxanthin–chlorophyll protein complex, which is responsible for the light harvesting function in marine algae diatoms, were investigated at 77 K by using two-dimensional electronic spectroscopy. Experiments performed on femtosecond and picosecond timescales led to separation of spectral dynamics, witnessing evolutions of coherence and population states of the system in the spectral region of Q{sub y} transitions of chlorophylls a and c. Analysis of the coherence dynamics allowed us to identify chlorophyll (Chl) a and fucoxanthin intramolecular vibrations dominating over the first few picoseconds. Closer inspection of the spectral region of the Q{sub y} transition of Chl c revealed previously not identified, mutually non-interacting chlorophyll c states participating in femtosecond or picosecond energy transfer to the Chl a molecules. Consideration of separated coherent and incoherent dynamics allowed us to hypothesize the vibrations-assisted coherent energy transfer between Chl c and Chl a and the overall spatial arrangement of chlorophyll molecules.
Trobo, Marta L.; Albano, Ezequiel V.; Binder, Kurt
2016-05-01
As a simplified model of a liquid nanostripe adsorbed on a chemically structured substrate surface, a two-dimensional Ising system with two boundaries at which surface fields act is studied. At the upper boundary, the surface field is uniformly negative, while at the lower boundary (a distance L apart), the surface field is negative only outside a range of extension b , where a positive surface stabilizes a droplet of the phase with positive magnetization for temperatures T exceeding the critical temperature Tw of the wetting transition of this model. We investigate the local order parameter profiles across the droplet, both in the directions parallel and perpendicular to the substrate, varying both b and T . Also, precursor effects to droplet formation as T approaches Tw from below are studied. In accord with theoretical predictions, for T >Tw the droplet is found to have the shape of a semiellipse, where the width (distance of the interface from the substrate) scale is proportional to b (b1 /2). So, the area of the droplet is proportional to b3 /2, and the temperature dependence of the corresponding prefactor, which also involves the interfacial stiffness, is studied.
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.
Ca2+ movement in smooth muscle cells studied with one- and two-dimensional diffusion models.
Kargacin, G; Fay, F S
1991-11-01
Although many of the processes involved in the regulation of Ca2+ in smooth muscle have been studied separately, it is still not well known how they are integrated into an overall regulatory system. To examine this question and to study the time course and spatial distribution of Ca2+ in cells after activation, one- and two-dimensional diffusion models of the cell that included the major processes thought to be involved in Ca regulation were developed. The models included terms describing Ca influx, buffering, plasma membrane extrusion, and release and reuptake by the sarcoplasmic reticulum. When possible these processes were described with known parameters. Simulations with the models indicated that the sarcoplasmic reticulum Ca pump is probably primarily responsible for the removal of cytoplasmic Ca2+ after cell activation. The plasma membrane Ca-ATPase and Na/Ca exchange appeared more likely to be involved in the long term regulation of Ca2+. Pumping processes in general had little influence on the rate of rise of Ca transients. The models also showed that spatial inhomogeneities in Ca2+ probably occur in cells during the spread of the Ca signal following activation and during the subsequent return of Ca2+ to its resting level.
Yan, Wei; Zhang, Jianfeng; Jing, Chuanyong
2013-01-15
Adsorption of Enrofloxacin (ENR) on minerals dominates the fate and transport of ENR in the environment. In this study, the sorption process of ENR on montmorillonite and the impact of dissolved organic matters (DOMs) on ENR-montmorillonite interactions were investigated using in situ ATR-FTIR spectroscopy and two-dimensional correlation analysis (2D-COS). Negative peaks were observed in the 3400-2900 cm(-1) region due to the loss of hydrated protons at montmorillonite surfaces. The primary characteristic peaks of adsorbed ENR molecules were resolved in the 1800-1100 cm(-1) range. The results of 2D-COS suggested the sorption process was initiated by the interaction of hydrated protons on montmorillonite surfaces with diverse moieties of ENR molecules depending on pH. The sorption mechanism of ENR was mainly cation exchange at acidic condition, charge neutralization at neutral condition, and proton transfer at alkaline condition. DOM could interact with piperazinyl amine groups of dissolved ENR, which changed the interaction sequence of ENR molecule with montmorillonite surfaces. Electrostatic interaction was the predominant driving force for the interaction between DOM and dissolved ENR. H-donor-acceptor interaction and π-π interaction may also be responsible to this interaction. Insights gained from this study improve our understandings on sorption mechanism of ENR and similar ionic organic pollutants in soil systems.
Murata Kazuya
2011-11-01
Full Text Available Abstract Background Sodium channel blockers augment ST-segment elevation in the right precordial leads in patients undergoing Brugada-type electrocardiography (ECG. However, their effect on echocardiographic features is not known. We address this by assessing global and regional ventricular function using conventional Doppler and two- dimensional (2D speckle tracking techniques. Methods Thirty-one patients with Brugada-type ECG were studied. A pure sodium channel blocker, pilsicainide, was used to provoke an ECG response. The percentage longitudinal systolic myocardial strain at the base of both the right ventricular (RV free wall and the interventricular septum wall was measured using 2D speckle tracking. Left ventricular (LV and RV myocardial performance (TEI indices were also measured. Results The pilsicainide challenge provoked a positive ECG response in 13 patients (inducible group. In the inducible group, longitudinal strain was significantly reduced only at the RV (-27.3 ± 5.4% vs -22.1 ± 3.6%, P P P Conclusions Temporal and spatial analysis using the TEI index and 2D strain imaging revealed the deterioration of global ventricular function associated with conduction disturbance and RV regional function in patients with Brugada-type ECG and coved type ST elevation due to administration of a sodium channel blocker.
Tan, Qing-Tian; Tian, Zhen-Hua; Li, Guo-Ying
2011-04-01
Conformational changes and specific interactions in the collagen/hyaluronic acid blends were studied by two-dimensional infrared correlation spectroscopy with the interruption of the component of hyaluronic acid in collagen/ hyaluronic acid blends. It was found that the synchronous cross-peaks, derived from stretching vibrations of C=O at 1 694 cm(-1), wagging of N-H at 1 524 cm(-1) and in-plane deformation of N-H at 1 241 cm(-1) of collagen, were indicative of local conformational changes of collagen. The synchronous negative cross-peak between stretching vibrations of C-OH of hyaluronic acid at 1 045 cm(-1) and streching vibrations of C=O of collagen at 1 694 cm(-1) suggested that the interaction of hydrogen bonding existing between O-H of HA and C=O of collagen with the content of HA varied from 0% to 50%. With the content of HA more than 50%, the cross-peak at 1 045 cm(-1) disappeared in synchronous correlation spectra while the intensity of cross-peak at (1 694, 1 524), (1 694, 1 241), (1 524, 1 241) increased, which indicated that no interaction was found between O-H of HA and collagen, however, the interactions of hydrogen bonding existed between C=O of HA and N-H of collagen, resulting in the conformational changes of collagen.
Numerical Studies of Collective Phenomena in Two-Dimensional Electron and Cold Atom Systems
Rezayi, Edward
2013-07-25
Numerical calculations were carried out to investigate a number of outstanding questions in both two-dimensional electron and cold atom systems. These projects aimed to increase our understanding of the properties of and prospects for non-Abelian states in quantum Hall matter.
Li, Zhenyu; Abramavicius, Darius; Zhuang, Wei; Mukamel, Shaul
2007-11-15
The two dimensional (2D) photon echo spectrum of the amide ultraviolet (UV) bands of proteins are simulated. Two effective exciton Hamiltonian parameter sets developed by Woody and Hirst, which predict similar CD spectra, may be distinguished by their very different 2DUV spectra. These differences are enhanced in specific configurations of pulse polarizations which provide chirality-induced signals.
T, M P Ramirez
2012-01-01
Using a conjecture that allows to approach separable-variables conductivity functions, the elements of the Modern Pseudoanalytic Function Theory are used, for the first time, to numerically solve the Dirichlet boundary value problem of the two-dimensional Electrical Impedance Equation, when the conductivity function arises from geometrical figures, located within bounded domains.
A two-dimensional global simulation study of inductive-dynamic magnetosphere-ionosphere coupling
Tu, Jiannan; Song, Paul
2016-12-01
We present the numerical methods and results of a global two-dimensional multifluid-collisional-Hall magnetohydrodynamic (MHD) simulation model of the ionosphere-thermosphere system, an extension of our one-dimensional three-fluid MHD model. The model solves, self-consistently, Maxwell's equations, continuity, momentum, and energy equations for multiple ion and neutral species incorporating photochemistry, collisions among the electron, ion and neutral species, and various heating sources in the energy equations. The inductive-dynamic approach (solving self-consistently Faraday's law and retaining inertia terms in the plasma momentum equations) used in the model retains all possible MHD waves, thus providing faithful physical explanation (not merely description) of the magnetosphere-ionosphere/thermosphere (M-IT) coupling. In the present study, we simulate the dawn-dusk cross-polar cap dynamic responses of the ionosphere to imposed magnetospheric convection. It is shown that the convection velocity at the top boundary launches velocity, magnetic, and electric perturbations propagating with the Alfvén speed toward the bottom of the ionosphere. Within the system, the waves experience reflection, penetration, and rereflection because of the inhomogeneity of the plasma conditions. The reflection of the Alfvén waves may cause overshoot (stronger than the imposed magnetospheric convection) of the plasma velocity in some regions. The simulation demonstrates dynamic propagation of the field-aligned currents and ionospheric electric field carried by the Alfvén waves, as well as formation of closure horizontal currents (Pedersen currents in the E region), indicating that in the dynamic stage the M-I coupling is via the Alfvén waves instead of field-aligned currents or electric field mapping as described in convectional M-I coupling models.
Gorshkov, V. N.; Navadeh, N.; Fallah, A. S.
2017-09-01
Phononic metamaterials are synthesised materials in which locally resonant units are arranged in a particular geometry of a substratum lattice and connected in a predefined topology. This study investigates dispersion surfaces in two-dimensional anisotropic acoustic metamaterials involving mass-in-mass units connected by massless springs in K3 topology. The reasons behind the particular choice of this topology are explained. Two sets of solutions for the eigenvalue problem | {\\boldsymbol{D}}({ω }2,{\\boldsymbol{k}})| =0 are obtained and the existence of absolutely different mechanisms of gap formation between acoustic and optical surface frequencies is shown as a bright display of quantum effects like strong coupling, energy splitting, and level crossings in classical mechanical systems. It has been concluded that a single dimensionless parameter i.e. relative mass controls the order of formation of gaps between different frequency surfaces. If the internal mass of the locally resonant mass-in-mass unit, m, increases relative to its external mass, M, then the coupling between the internal and external vibrations in the whole system rises sharply, and a threshold {μ }* is reached so that for m/M> {μ }* the optical vibrations break the continuous spectrum of ‘acoustic phonons’ creating the gap between them for any value of other system parameters. The methods to control gap parameters and polarisation properties of the optical vibrations created over these gaps were investigated. Dependencies of morphology and width of gaps for several anisotropic cases have been expounded and the physical meaning of singularity at the point of tangential contact between two adjacent frequency surfaces has been provided. Repulsion between different frequency band curves, as planar projections of surfaces, has been explained. The limiting case of isotropy has been discussed and it has been shown that, in the isotropic case, the lower gap always forms, irrespective of the value
Danon, M.J.; Giometti, C.S.; Manaligod, J.R.; Perurena, O.H.; Skosey, J.L.
1981-12-01
A 65-year-old woman with progressive muscle weakness and a diffuse rash of three years' duration was examined. Muscle tissue was studied with histochemical techniques, phase-contrast microscopy, electron microscopy, and two-dimensional electrophoresis. Histochemical studies showed numerous nemaline rods, with a normal ratio of types I and II fibers. Two-dimensional electrophoresis revealed abnormalities in the myosin light chain and tropomyosin protein patterns when compared with normal and diseased muscle biopsy samples, including those from two patients with adult-onset dermatomyositis.
Interaction of two-dimensional turbulence with a sheared channel flow: a numerical study
Kamp, Leon; Marques Rosas Fernandes, Vitor; van Heijst, Gertjan; Clercx, Herman
2015-11-01
Interaction of large-scale flows with turbulence is of fundamental and widespread importance in geophysical fluid dynamics and also, more recently for the dynamics of fusion plasma. More specifically the interplay between two-dimensional turbulence and so-called zonal flows has gained considerable interest because of its relevance for transport and associated barriers. We present numerical results on the interaction of driven two-dimensional turbulence with typical sheared channel flows (Couette and Poiseuille). It turns out that a linear shear rate that is being sustained by moving channel walls (Couette flow) is far more effective in suppressing turbulence and associated transport than a Poiseuille flow. We explore the mechanisms behind this in relation to the width of the channel and the strength of the shear of the background flow. Also the prominent role played by the no-slip boundaries and the Reynolds stress is discussed.
Xiang MA; Ye-fei ZHU; Jia-hao SHA; Zuo-min ZHOU; Jia-yin LIU
2003-01-01
Objective To apply two-dimensional electrophoresis and mass spectrometry in the ovary proteome research Methods Protein extractions from mouse ovaries were run in IPGphor isoelectric focus system with 11 cm and 24 cm IPG strips respectively (pH 3～10, 0.3 mm thick), then the protein spots were identified by mass spectrometry.Results The ovary protein exactions separated by two-dimensional electrophoresis have got high resolution, and identifing protein by mass spectrometry was highly efficient and facilitly.These two techniques should facilitate further investigation of female reproduction proteome research.Conclusion These two rapid high resolutions and efficient techniques have a variety of applications foreground in female reproduction proteome pattern research.
Further studies of stall flutter and nonlinear divergence of two-dimensional wings
Dugundji, J.; Chopra, I.
1975-01-01
An experimental investigation is made of the purely torsional stall flutter of a two-dimensional wing pivoted about the midchord, and also of the bending-torsion stall flutter of a two-dimensional wing pivoted about the quarterchord. For the purely torsional flutter case, large amplitude limit cycles ranging from + or - 11 to + or - 160 degrees were observed. Nondimensional harmonic coefficients were extracted from the free transient vibration tests for amplitudes up to 80 degrees. Reasonable nondimensional correlation was obtained for several wing configurations. For the bending-torsion flutter case, large amplitude coupled limit cycles were observed with torsional amplitudes as large as + or - 40 degrees. The torsion amplitudes first increased, then decreased with increasing velocity. Additionally, a small amplitude, predominantly torsional flutter was observed when the static equilibrium angle was near the stall angle.
Votsish, A.D.; Kolesnikov, Yu.B.
1977-01-01
Results are given for an experimental study of two-dimensional turbulent flow with shifts in a plane duct in an azimuthal magnetic field. The turbulent flow was shown to become practically equal to zero in a sufficiently strong field whereas the intensity of the pulsation rate has a finite value. This is explained by the fact that the magnetic field transforms the structure of turbulence into a two-dimensional structure whose maintenance merely requires an insignificant portion of medium flow energy. 4 illustrations, 8 references.
A Study of Two-Dimensional Unsteady Breaking Waves in Finite-Depth Water
2010-01-01
1880). [8] J. H. Duncan, “An experimental investigation of breaking waves produced by a towed hydrofoil ,” Proc. R. Soc. London, Ser. A 377, 331(1981...measured the drag per unit length due to quasi-steady breaking waves generated with a submerged hydrofoil . His measurements illustrated that the... hydrofoil . Proc. R. Soc. London Ser. A 377, 331-348. DUNCAN, J. H. 1983 The breaking and non-breaking wave resistance of a two- dimensional hydrofoil . J
Design and experimental study of a two-dimensional position sensitive X-ray detector
无
2008-01-01
A prototype of a two-dimensional position sensitive X-ray detector was designed and constructed for small angle X-ray scattering experiments at BSFR (Beijing Synchrotron Radiation Facility). The detector is based on MWPC with cathode strip readout, and has a sensitive area of 200 mmx200 mm. The spatial resolution (FWHM) of about 210 μm along the anode wire direction was obtained from the 55Fe X-ray test of the detector.
The mean field study of phase transitions in two dimensional Kagome lattice under local anisotropy
S. Mortezapour
2007-06-01
Full Text Available In this work we investigated the critical properties of the anti-ferromagnetic XY model on a two dimensional Kagome lattice under single-ion easy-axes anisotropy. Employing the mean field theory, we found that this model shows a second order phase transition from disordered to all-in all-out state for any value of anisotropy.
A Comparative Study of Stability Testing Approaches of Two-Dimensional Recursive Digital Filters
K. R. Santhi; M.Ponnavaikko; N. Gangatharan
2008-01-01
There are many problems in science and engineering whose solution is applied in the design of Multi-Dimensional (MD) digital filters. Digital filtering finds an important position in the field of digital signal and image processing. Recently there had been a great deal of interest in the design and stability analysis of Two-Dimensional (2-D) recursive digital filters. The design techniques for stable One Dimensional (1-D) digital filters are relatively well developed; but their extension to 2...
Wu, Haiping, E-mail: mrhpwu@njust.edu.cn [Department of Applied Physics, Nanjing University of Science and Technology, Nanjing 210094 (China); State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Qian, Yan, E-mail: qianyan@njust.edu.cn [Department of Applied Physics, Nanjing University of Science and Technology, Nanjing 210094 (China); Lu, Ruifeng; Tan, Weishi [Department of Applied Physics, Nanjing University of Science and Technology, Nanjing 210094 (China)
2016-02-15
Motivated by the recent synthesis of bulk MoN{sub 2} which exhibits the layered structure just like the bulk MoS{sub 2}, the monolayered MoN{sub 2} exfoliated from the bulk counterpart is investigated systematically by using density-functional calculations in this work. The result shows that the ground-state two-dimensional monolayered MoN{sub 2} behaves as an indirect band gap semiconductor with the energy gap of ∼0.12 eV. Subsequently, the external strain from −6% to 6% is employed to engineer the band structure, and the energy gap can be efficiently tuned from 0 to 0.70 eV. Notably, when the strain is beyond 5% or −3%, the two-dimensional monolayered MoN{sub 2} would transfer from an indirect band gap to a direct band gap semiconductor. This work introduces a new member of two-dimensional transition-metal family, which is important for industry applications, especially for the utilization in the long-wavelength infrared field. - Highlights: • The 2D MoN{sub 2} behaves as an indirect band gap semiconductor with the energy gap of ∼0.12 eV. • The energy gap can be efficiently tuned from 0 to 0.70 eV by small strain. • The band gap would transfer from an indirect to a direct one when the strain is beyond 5% or −3%.
Teixeira, Rogério; Monteiro, Ricardo; Dinis, Paulo; Santos, Maria José; Botelho, Ana; Quintal, Nuno; Cardim, Nuno; Gonçalves, Lino
2016-11-24
Vascular mechanics assessed with two-dimensional speckle tracking echocardiography (2D-STE) could be used as a new imaging surrogate of vascular stiffening. The CHA2DS2-VASc score is considered accurate as an estimate of stroke risk in non-valvular AF, although many potential stroke risk factors have not been included in this scoring method. The purpose of this research is to study the feasibility of evaluating vascular mechanics at the descending aorta in non-valvular AF patients using transesophageal 2D-STE and to analyze the association between descending aortic mechanics and stroke. We prospectively recruited a group of 44 patients referred for a transesophageal echocardiogram (TEE) in the context of cardioversion for non-valvular AF. A short-axis view of the descending aorta, one to two centimeters after the aortic arch was selected for the vascular mechanics assessment with the 2D-STE methodology. The vascular mechanics parameters analyzed were circumferential aortic strain (CAS) and early circumferential aortic strain rate (CASR). A clinical assessment was performed with focus on the past stroke history and the CHA2DS2-VASc score. The mean age of our cohort was 65 ± 13 years and 75% were men; AF was known for 2.8 ± 2.5 years and it was considered paroxystic in 41% of cases. Waveforms adequate for measuring 2D-STE were present in 85% of the 264 descending aortic wall segments. The mean CAS was 3.5 ± 1.2% and the mean CASR was 0.7 ± 0.3 s(-1). The inter- and intra-observer variability for aortic mechanics was considered adequate. The median CHA2DS2VASc score was 2 (2-3). As the score increased we noted that both the CAS (r = -0.38, P = 0.01) and the CASR (r = -0.42, P mechanics assessed with transesophageal 2D-STE.
Kah, Cherno Baba; Yu, M.; Jayanthi, C. S.; Wu, S. Y.
2014-03-01
Our previous study on one-dimensional icosahedral B12 cluster (α-B12) based chain [Bulletin of APS Annual Meeting, p265 (2013)] and ring structures has prompted us to study the two-dimensional (2D) α-B12 based structures. Recently, we have carried out a systematic molecular dynamics study on the structural stabilities and electronic properties of the 2D α-B12 based structures using the SCED-LCAO method [PRB 74, 15540 (2006)]. We have considered several types of symmetry for these 2D structures such as δ3, δ4, δ6 (flat triangular), and α' types. We have found that the optimized structures are energetically in the order of δ6 < α' < δ3 < δ4 which is different from the energy order of α'< δ6 < δ4 < δ3 found in the 2D boron monolayer sheets [ACS Nano 6, 7443 (2012)]. A detailed discussion of this study will be presented. The first author acknowledges the McSweeny Fellowship for supporting his research in this work.
YANG XunYu; WANG Fang; CHEN QiuXia; WANG LiYan; WANG ZhiQiang
2007-01-01
We described the formation of self-organized two-dimensional (2D) assemblies of N-(2,3,5,6-tetrafluoro- 4-iodophenyl)hexadecylamine and 1-dodecyl-imidazole at the liquid/HOPG interface. The two-dimen- sional assemblies showed a fishbone-like pattern structure as revealed by high-resolution scanning tunneling microscopy. Although different interactions can drive the formation of 2D assemblies,as far as we know,this is the first report on halogen bond-driven 2D assemblies.
Contreras, Anthony Marshall [Univ. of California, Berkeley, CA (United States)
2006-05-20
In order to better understand the fundamental components that govern catalytic activity, two-dimensional model platinum nanocatalyst arrays have been designed and fabricated. These catalysts arrays are meant to model the interplay of the metal and support important to industrial heterogeneous catalytic reactions. Photolithography and sub-lithographic techniques such as electron beam lithography, size reduction lithography and nanoimprint lithography have been employed to create these platinum nanoarrays. Both in-situ and ex-situ surface science techniques and catalytic reaction measurements were used to correlate the structural parameters of the system to catalytic activity.
Water-channel study of flow and turbulence past a two-dimensional array of obstacles
Di Bernardino, Annalisa; Leuzzi, Giovanni; Querzoli, Giorgio
2016-01-01
A neutral boundary layer was generated in the laboratory to analyze the mean velocity field and the turbulence field within and above an array of two-dimensional obstacles simulating an urban canopy. Different geometrical configurations were considered in order to investigate the main characteristics of the flow as a function of the aspect ratio (AR) of the canopy. To this end, a summary of the two-dimensional fields of the fundamental turbulence parameters is given for AR ranging from 1 to 2. The results show that the flow field depends strongly on AR only within the canyon, while the outer flow seems to be less sensitive to this parameter. This is not true for the vertical momentum flux, which is one of the parameters most affected by AR, both within and outside the canyon. The experiments also indicate that, when (i.e. the skimming flow regime), the roughness sub-layer extends up to a height equal to 1.25 times the height of the obstacles (H), surmounted by an inertial sub-layer that extends up to 2.7 H. I...
Vyalikh, D V [Institute of Solid State Physics, Dresden University of Technology, D-01062 Dresden (Germany); Kirchner, A [BioNanotechnology and Structure Formation Group, Max Bergmann Centre of Biomaterials, Dresden University of Technology, D-01062 Dresden (Germany); Kade, A [Institute of Solid State Physics, Dresden University of Technology, D-01062 Dresden (Germany); Danzenbaecher, S [Institute of Solid State Physics, Dresden University of Technology, D-01062 Dresden (Germany); Dedkov, Yu S [Institute of Solid State Physics, Dresden University of Technology, D-01062 Dresden (Germany); Mertig, M [BioNanotechnology and Structure Formation Group, Max Bergmann Centre of Biomaterials, Dresden University of Technology, D-01062 Dresden (Germany); Molodtsov, S L [Institute of Solid State Physics, Dresden University of Technology, D-01062 Dresden (Germany)
2006-04-05
Photoemission (PE) and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy were applied to characterize electronic properties of the regular two-dimensional bacterial surface protein layer (S layer) of Bacillus sphaericus NCTC 9602, which is widely used as a protein template for the bottom-up fabrication of advanced metallic and hybrid nanostructures. PE and NEXAFS at the C 1s, O 1s, and N 1s core levels show similar chemical states for each oxygen atom and also for each nitrogen atom, while carbon atoms exhibit a range of chemical environments in different functional groups of the amino acids. A series of characteristic NEXAFS peaks were assigned to particular molecular orbitals of the amino acids by applying a phenomenological building-block model. It was found that the {pi} clouds of aromatic rings make the main contribution to both the lowest unoccupied and highest occupied molecular orbitals. The two-dimensional protein crystal shows a semiconductor-like behaviour with a gap value of {approx}3.0 eV and the Fermi energy close to the bottom of the LUMO.
Xiao, Qian; Gu, Xiaohong; Tan, Suo
2014-12-01
Drying process of aqueous sodium alginate solutions at 50°C was investigated by ATR-FTIR spectroscopy and two-dimensional correlation infrared spectroscopy. Two-dimensional asynchronous spectrum at 1,800-1,350 cm(-1) wavenumber could be resolved into five separate bands, which were assigned to O-H bending vibrations in water (around 1,645 cm(-1)), antisymmetric and symmetric stretching vibrations of free and hydrogen-bonded COO(-) groups of alginate (around 1,595, 1,412, 1,572 and 1,390 cm(-1), respectively). As the drying process progressed, absorbance bands at around 1,127 and 1,035 cm(-1) significantly shifted to lower wavenumbers (1120 and 1027cm(-1), respectively). Suggesting that oxygen atoms at the 2th and 3th position in the pyranose ring might have hydrogen bonded with water or alginate chains. Further analysis using 2D asynchronous correlation spectroscopy between 1800-1500 and 1200-960 cm(-1) wavenumber regions revealed the sequence of spectral changes during the drying process. Copyright © 2014 Elsevier Ltd. All rights reserved.
Nebular Spectra of SN 1998bw Revisited: Detailed Study by One and Two Dimensional Models
Maeda, K; Mazzali, P A; Deng, J
2006-01-01
Refined one- and two-dimensional models for the nebular spectra of the hyper-energetic Type Ic supernova (SN) 1998bw, associated with the gamma-ray burst GRB980425, from 125 to 376 days after B-band maximum are presented. One dimensional, spherically symmetric spectrum synthesis calculations show that reproducing features in the observed spectra, i.e., the sharply peaked [OI] 6300\\AA doublet and MgI] 4570\\AA emission, and the broad [FeII] blend around 5200\\AA, requires the existence of a high-density O-rich core expanding at low velocities ($\\lsim 8,000$ km s$^{-1}$) and of Fe-rich material moving faster than the O-rich material. Synthetic spectra at late phases from aspherical (bipolar) explosion models are also computed with a two-dimensional spectrum synthesis code. The above features are naturally explained by the aspherical model if the explosion is viewed from a direction close to the axis of symmetry ($\\sim 30^{\\rm o}$), since the aspherical model yields a high-density O-rich region confined along the ...
Hybrid-space density matrix renormalization group study of the doped two-dimensional Hubbard model
Ehlers, G.; White, S. R.; Noack, R. M.
2017-03-01
The performance of the density matrix renormalization group (DMRG) is strongly influenced by the choice of the local basis of the underlying physical lattice. We demonstrate that, for the two-dimensional Hubbard model, the hybrid-real-momentum-space formulation of the DMRG is computationally more efficient than the standard real-space formulation. In particular, we show that the computational cost for fixed bond dimension of the hybrid-space DMRG is approximately independent of the width of the lattice, in contrast to the real-space DMRG, for which it is proportional to the width squared. We apply the hybrid-space algorithm to calculate the ground state of the doped two-dimensional Hubbard model on cylinders of width four and six sites; at n =0.875 filling, the ground state exhibits a striped charge-density distribution with a wavelength of eight sites for both U /t =4.0 and 8.0 . We find that the strength of the charge ordering depends on U /t and on the boundary conditions. Furthermore, we investigate the magnetic ordering as well as the decay of the static spin, charge, and pair-field correlation functions.
Study on Absorption Heat transfer of Two-Dimensionally Constant Curvature Surface Tubes-1
Ogawa, Kiyoshi; Isshiki, Naotsugu
In order to get better heat transfer coefficient of absorption in actual apparatus, it is considered that the wettability of the surface should be high, and that the thickness of liquid film should not be too thin or too thick all over the surface. So, new conception of two-dimensionally constant curvature surface (CCS) for absorption heat transfer has been introduced for the first time by the authors. First, theoretical CCS section curves of CCS tubes were calculated, and some of them were manufactured for the test. The wettability of CCS is tested and compared to the other finned tubes (radial fin tubes of triangular and rectangular profiles). As may be seen from photographs and compared to the other finned tubes, on the CCS surface, the thickness of liquid has shown to be even all over the surface without creating paticulary thick or thin place, so that, liquid films are very wettable on the CCS surface.
Study on electro-optic properties of two-dimensional PLZT photonic crystal band structure
TONG Kai; WU Xiao-gang; WANG Mei-ting
2011-01-01
The band characteristics of two-dimensional (2D) lead lanthanum zirconate titanate (PLZT) photonic cystals are analyzed by finite element method. The electro-optic effect of PLZT can cause the refractive index change when it is imposed by the applied electric field, and the band structure of 2D photonic crystals based on PLZT varies accordingly. The effect of the applied electric field on the structural characteristics of the first and second band gaps in 2D PLZT photonic crystals is analyzed in detail. And the results show that for each band gap, the variations of start wavelength, cut-off wavelength and bandwidth are proportional to quadratic of the electric field.
A numerical study of the alpha model for two-dimensional magnetohydrodynamic turbulent flows
Mininni, P D; Pouquet, A G
2004-01-01
We explore some consequences of the ``alpha model,'' also called the ``Lagrangian-averaged'' model, for two-dimensional incompressible magnetohydrodynamic (MHD) turbulence. This model is an extension of the smoothing procedure in fluid dynamics which filters velocity fields locally while leaving their associated vorticities unsmoothed, and has proved useful for high Reynolds number turbulence computations. We consider several known effects (selective decay, dynamic alignment, inverse cascades, and the probability distribution functions of fluctuating turbulent quantities) in magnetofluid turbulence and compare the results of numerical solutions of the primitive MHD equations with their alpha-model counterparts' performance for the same flows, in regimes where available resolution is adequate to explore both. The hope is to justify the use of the alpha model in regimes that lie outside currently available resolution, as will be the case in particular in three-dimensional geometry or for magnetic Prandtl number...
Michel, K. H.; ćakır, D.; Sevik, C.; Peeters, F. M.
2017-03-01
The elastic constant C11 and piezoelectric stress constant e1 ,11 of two-dimensional (2D) dielectric materials comprising h-BN, 2 H -MoS2 , and other transition-metal dichalcogenides and dioxides are calculated using lattice dynamical theory. The results are compared with corresponding quantities obtained with ab initio calculations. We identify the difference between clamped-ion and relaxed-ion contributions with the dependence on inner strains which are due to the relative displacements of the ions in the unit cell. Lattice dynamics allows us to express the inner-strain contributions in terms of microscopic quantities such as effective ionic charges and optoacoustical couplings, which allows us to clarify differences in the piezoelectric behavior between h-BN and MoS2. Trends in the different microscopic quantities as functions of atomic composition are discussed.
A two-dimensional model for the study of interpersonal attraction.
Montoya, R Matthew; Horton, Robert S
2014-02-01
We describe a model for understanding interpersonal attraction in which attraction can be understood as a product of the initial evaluations we make about others. The model posits that targets are evaluated on two basic dimensions, capacity and willingness, such that affective and behavioral attraction result from evaluations of (a) a target's capacity to facilitate the perceiver's goals/needs and (b) a target's potential willingness to facilitate those goals/needs. The plausibility of the two-dimensional model of attraction is evaluated vis-à-vis the extant literature on various attraction phenomena including the reciprocity of liking effect, pratfall effect, matching hypothesis, arousal effects, and similarity effect. We conclude that considerable evidence across a wide range of phenomena supports the idea that interpersonal attraction is principally determined by inferences about the target's capacity and willingness.
Kallin, Ann B; Hyatt, Katharine; Singh, Rajiv R P; Melko, Roger G
2013-03-29
We develop a method to calculate the bipartite entanglement entropy of quantum models, in the thermodynamic limit, using a numerical linked-cluster expansion (NLCE) involving only rectangular clusters. It is based on exact diagonalization of all n×m rectangular clusters at the interface between entangled subsystems A and B. We use it to obtain the Renyi entanglement entropy of the two-dimensional transverse field Ising model, for arbitrary real Renyi index α. Extrapolating these results as a function of the order of the calculation, we obtain universal pieces of the entanglement entropy associated with lines and corners at the quantum critical point. They show NLCE to be one of the few methods capable of accurately calculating universal properties of arbitrary Renyi entropies at higher dimensional critical points.
Finite Element Model for Failure Study of Two-Dimensional Triaxially Braided Composite
Li, Xuetao; Binienda, Wieslaw K.; Goldberg, Robert K.
2010-01-01
A new three-dimensional finite element model of two-dimensional triaxially braided composites is presented in this paper. This meso-scale modeling technique is used to examine and predict the deformation and damage observed in tests of straight sided specimens. A unit cell based approach is used to take into account the braiding architecture as well as the mechanical properties of the fiber tows, the matrix and the fiber tow-matrix interface. A 0 deg / plus or minus 60 deg. braiding configuration has been investigated by conducting static finite element analyses. Failure initiation and progressive degradation has been simulated in the fiber tows by use of the Hashin failure criteria and a damage evolution law. The fiber tow-matrix interface was modeled by using a cohesive zone approach to capture any fiber-matrix debonding. By comparing the analytical results to those obtained experimentally, the applicability of the developed model was assessed and the failure process was investigated.
Roslyak, O.; Gumbs, Godfrey; Mukamel, S.
2012-05-01
We study the localization of dressed Dirac electrons in a cylindrical quantum dot (QD) formed on monolayer and bilayer graphene by spatially different potential profiles. Short lived excitonic states which are too broad to be resolved in linear spectroscopy are revealed by cross peaks in the photon-echo nonlinear technique. Signatures of the dynamic gap in the two-dimensional spectra are discussed. The effect of the Coulomb induced exciton-exciton scattering and the formation of biexciton molecules are demonstrated.
The MHD Kelvin-Helmholtz instability a two-dimensional numerical study
Frank, A I; Ryu, D; Gaalaas, J B; Frank, Adam; Ryu, Dongsu; Gaalaas, Joseph B
1995-01-01
Using a new numerical code we have carried out two-dimensional simulations of the nonlinear evolution of unstable sheared magnetohydrodynamic flows. We considered two cases: a strong magnetic field (Alfven Mach number, M_a = 2.5) and a weak field (M_a =5). Each flow rapidly evolves until it reaches a nearly steady condition, which is fundamentally different from the analogous gasdynamic state. Both MHD flows relax to a stable, laminar flow on timescales less than or of the order of 15 linear growth times, measured from saturation of the instability. That timescale is several orders of magnitude less than the nominal dissipation time for these simulated flows, so this condition represents an quasi-steady relaxed state. The strong magnetic field case reaches saturation as magnetic tension in the displaced flow boundary becomes sufficient to stabilize it. That flow then relaxes in a straightforward way to the steady, laminar flow condition. The weak magnetic field case, on the other hand, begins development of t...
Experimental study of two-dimensional quantum Wigner solid in zero magnetic field
Huang, Jian [Department of Physics and Astronomy, Wayne State University, Detroit, MI 48201 (United States); Pfeiffer, L. N.; West, K. W. [Department of Electrical Engineering, Princeton University, Princeton, NJ 08544 (United States)
2014-03-31
At temperatures T → 0, strongly interacting two-dimensional (2D) electron systems manifest characteristic insulating behaviors that are key for understanding the nature of the ground state in light of the interplay between disorder and electron-electron interaction. In contrast to the hopping conductance demonstrated in the insulating side of the metal-to-insulator transition, the ultra-high quality 2D systems exhibit nonactivated T-dependence of the conductivity even for dilute carrier concentrations down to 7×10{sup 8} cm{sup −2}. The apparent metal-to-insulator transition (MIT) occurs for a large r{sub s} value around 40 for which a Wigner Crystalllization is expected. The magnetoresistance for a series of carrier densities in the vicinity of the transition exhibits a characteristic sign change in weak perpendicular magnetic field. Within the Wigner Crystallization regime (with r{sub s} > 40), we report an experimental observation of a characteristic nonlinear threshold behavior from a high-resolution dc dynamical response as an evidence for aWigner crystallization in high-purity GaAs 2D hole systems in zero magnetic field. The system under an increasing current drive exhibits voltage oscillations with negative differential resistance. They confirm the coexistence of a moving crystal along with striped edge states as observed for electrons on helium surfaces. Moreover, the threshold is well below the typical classical levels due to a different pinning and depinning mechanism that is possibly related to quantum processes.
Experimental study of two-dimensional quantum Wigner solid in zero magnetic field
Huang, Jian; Pfeiffer, L. N.; West, K. W.
2014-03-01
At temperatures T → 0, strongly interacting two-dimensional (2D) electron systems manifest characteristic insulating behaviors that are key for understanding the nature of the ground state in light of the interplay between disorder and electron-electron interaction. In contrast to the hopping conductance demonstrated in the insulating side of the metal-to-insulator transition, the ultra-high quality 2D systems exhibit nonactivated T-dependence of the conductivity even for dilute carrier concentrations down to 7×108 cm-2. The apparent metal-to-insulator transition (MIT) occurs for a large rs value around 40 for which a Wigner Crystalllization is expected. The magnetoresistance for a series of carrier densities in the vicinity of the transition exhibits a characteristic sign change in weak perpendicular magnetic field. Within the Wigner Crystallization regime (with rs > 40), we report an experimental observation of a characteristic nonlinear threshold behavior from a high-resolution dc dynamical response as an evidence for aWigner crystallization in high-purity GaAs 2D hole systems in zero magnetic field. The system under an increasing current drive exhibits voltage oscillations with negative differential resistance. They confirm the coexistence of a moving crystal along with striped edge states as observed for electrons on helium surfaces. Moreover, the threshold is well below the typical classical levels due to a different pinning and depinning mechanism that is possibly related to quantum processes.
Two-dimensional Kagome phosphorus and its edge magnetism: a density functional theory study.
Yu, Guodong; Jiang, Liwei; Zheng, Yisong
2015-07-01
By means of density functional theory calculations, we predict a new two-dimensional phosphorus allotrope with the Kagome-like lattice(Kagome-P). It is an indirect gap semiconductor with a band gap of 1.64 eV. The gap decreases sensitively with the compressive strain. In particular, shrinking the lattice beyond 13% can drive it into metallic state. In addition, both the AA and AB stacked Kagome-P multi-layer structures exhibit a bandgap much smaller than 1.64 eV. Edges in the Kagome-P monolayer probably suffer from the edge reconstruction. An isolated zigzag edge can induce antiferromagnetic (AF) ordering with a magnetic transition temperature of 23 K. More importantly, when applying a stretching strain beyond 4%, such an edge turns to possess a ferromagnetic ground state. A very narrow zigzag-edged Kagome-P ribbon displays the spin moment distribution similar to the zigzag-edged graphene nanoribbon because of the coupling between the opposites edges. But the inter-edge coupling in the Kagome-P ribbon vanishes more rapidly as the ribbon width increases. These properties make it a promising material in spintronics.
Two-dimensional Kagome phosphorus and its edge magnetism: a density functional theory study
Yu, Guodong; Jiang, Liwei; Zheng, Yisong
2015-06-01
By means of density functional theory calculations, we predict a new two-dimensional phosphorus allotrope with the Kagome-like lattice(Kagome-P). It is an indirect gap semiconductor with a band gap of 1.64 eV. The gap decreases sensitively with the compressive strain. In particular, shrinking the lattice beyond 13% can drive it into metallic state. In addition, both the AA and AB stacked Kagome-P multi-layer structures exhibit a bandgap much smaller than 1.64 eV. Edges in the Kagome-P monolayer probably suffer from the edge reconstruction. An isolated zigzag edge can induce antiferromagnetic (AF) ordering with a magnetic transition temperature of 23 K. More importantly, when applying a stretching strain beyond 4%, such an edge turns to possess a ferromagnetic ground state. A very narrow zigzag-edged Kagome-P ribbon displays the spin moment distribution similar to the zigzag-edged graphene nanoribbon because of the coupling between the opposites edges. But the inter-edge coupling in the Kagome-P ribbon vanishes more rapidly as the ribbon width increases. These properties make it a promising material in spintronics.
Weisz, K; Shafer, R H; Egan, W; James, T L
1992-08-25
Phase-sensitive two-dimensional nuclear Overhauser enhancement (2D NOE) and double-quantum-filtered correlated (2QF-COSY) spectra were recorded at 500 MHz for the DNA duplex d(CATTTGCATC).d(GATGCAAATG), which contains the octamer element of immunoglobulin genes. Exchangeable and nonexchangeable proton resonances including those of the H5' and H5" protons were assigned. Overall, the decamer duplex adopts a B-type DNA conformation. Scalar coupling constants for the sugar protons were determined by quantitative simulations of 2QF-COSY cross-peaks. These couplings are consistent with a two-state dynamic equilibrium between a minor N- and a major S-type conformer for all residues. The pseudorotation phase angle P of the major conformer is in the range 117-135 degrees for nonterminal pyrimidine nucleotides and 153-162 degrees for nonterminal purine nucleotides. Except for the terminal residues, the minor conformer comprises less than 25% of the population. Distance constraints obtained by a complete relaxation matrix analysis of the 2D NOE intensities with the MARDIGRAS algorithm confirm the dependence of the sugar pucker on pyrimidine and purine bases. Averaging by fast local motions has at most small effects on the NOE-derived interproton distances.
Simulation study of localization of electromagnetic waves in two-dimensional random dipolar systems.
Wang, Ken Kang-Hsin; Ye, Zhen
2003-12-01
We study the propagation and scattering of electromagnetic waves by random arrays of dipolar cylinders in a uniform medium. A set of self-consistent equations, incorporating all orders of multiple scattering of the electromagnetic waves, is derived from first principles and then solved numerically for electromagnetic fields. For certain ranges of frequencies, spatially localized electromagnetic waves appear in such a simple but realistic disordered system. Dependence of localization on the frequency, radiation damping, and filling factor is shown. The spatial behavior of the total, coherent, and diffusive waves is explored in detail, and found to comply with a physical intuitive picture. A phase diagram characterizing localization is presented, in agreement with previous investigations on other systems.
Mobility anisotropy of two-dimensional semiconductors
Lang, Haifeng; Zhang, Shuqing; Liu, Zhirong
2016-12-01
The carrier mobility of anisotropic two-dimensional semiconductors under longitudinal acoustic phonon scattering was theoretically studied using deformation potential theory. Based on the Boltzmann equation with the relaxation time approximation, an analytic formula of intrinsic anisotropic mobility was derived, showing that the influence of effective mass on mobility anisotropy is larger than those of deformation potential constant or elastic modulus. Parameters were collected for various anisotropic two-dimensional materials (black phosphorus, Hittorf's phosphorus, BC2N , MXene, TiS3, and GeCH3) to calculate their mobility anisotropy. It was revealed that the anisotropic ratio is overestimated by the previously described method.
Neumann, A.U.; Derrida, B.
1988-10-01
We study the time evolution of two configurations submitted to the same thermal noise for several two dimensional models (Ising ferromagnet, symmetric spin glass, non symmetric spin glass). For all these models, we find a non zero critical temperature above which the two configurations always meet. Using finite size scaling ideas, we determine for these three models this dynamical phase transition and some of the critical exponents. For the ferromagnet, the transition T/sub c/ approx. = 2.25 coincides with the Curie temperature whereas for the two spin glass models +- J distribution of bonds) we obtain T/sub c/ approx. = 1.5-1.7.
Ren, Guo-Dong; Guo, Ai-Ling; Geng, Fang; Ma, Mei-Hu; Huang, Qun; Wu, Xiao-Fen
2012-07-01
The conformation changes of Apo-Ovotransferrin and Holo-Ovotransferrin were studied with the heat treatment 25-95 degrees C by using Fourier transform infrared spectroscopy (FTIR) and two-dimensional correlation spectroscopy analyzer. The results of one-dimensional infrared spectroscopy showed that with the increase in temperature, the peak at 3 300 cm(-1) of Apo-Ovo-transferrin shifted more than that of Holo-Ovotransferrin. The peak at 3 300 cm(-1) derived from stretching vibrations of N-H and O-H indicates that iron-binding enhanced the role of hydrogen bonds and resistance to heat. The changing order of the secondary structure of ovotransferrin was determined by analyzing two-dimensional infrared spectra,witch is beta-sheet>amide II >-CH2 - bending vibration. In addition, it was found that the cross-peaks at 1 652 and 1 688 cm(-1) are different in synchronous and asynchronous counter maps by comparing Apo-Ovotransferrin with Holo-Ovotransferrin. It was suggested that the temperature made less impact on the alpha-helix in Holo-Ovotransferrin than on that in Apo-Ovotransferrin, however, the beta-turn in Holo-Ovotransferrin was more sensitive to temperature.
Li, Weizhen; Wu, Peiyi
2009-08-01
The crystal structure transition of syndiotactic polystyrene film from the helical conformation to the more stable planar zigzag conformation during a heating process was studied using Fourier transform infrared (FT-IR) spectroscopy in combination with two-dimensional (2D) correlation analysis and perturbation-correlation moving-window 2D analysis. The sequence of different conformations during the transition was investigated by analyzing two-dimensional FT-IR correlation spectra in the spectral ranges of 800-700 cm(-1) and 600-500 cm(-1). It was observed that the conformation of delta helical changes prior to gamma helical, and the gamma helical phase is faster than the alpha' planar zigzag phase. By utilizing the 2D asynchronous correlation spectra, the 744 cm(-1) band, which is usually incorporated in the broad 750 cm(-1) band, can now be uniquely attributed as the alpha' zigzag configuration for the first time. Furthermore, by employing thermal perturbation, the shorter helical segments consisting of m = 7-12 and m = 12-20 monomeric units were disturbed in a shorter time than the longer helical segments m = 20-30 during the heating process.
A Theoretical Study of the Two-Dimensional Point Focusing by Two Multilayer Laue Lenses.
Yan,H.; Maser, J.; Kang, H.C.; Macrader, A.; Stephenson, B.
2008-08-10
Hard x-ray point focusing by two crossed multilayer Laue lenses is studied using a full-wave modeling approach. This study shows that for a small numerical aperture, the two consecutive diffraction processes can be decoupled into two independent ones in respective directions. Using this theoretical tool, we investigated adverse effects of various misalignments on the 2D focus profile and discussed the tolerance to them. We also derived simple expressions that described the required alignment accuracy.
A Two-Dimensional Landau-Lifshitz Model in Studying Thin Film Micromagnetics
Jingna Li
2009-01-01
equation which was first raised by A. DeSimone and F. Otto, and so fourth, when studying thin film micromagnetics. We get the existence of a local weak solution by approximating it with a higher-order equation. Penalty approximation and semigroup theory are employed to deal with the higher-order equation.
Sedghi, Aliasghar [Islamic Azad University, Shabestar (Iran, Islamic Republic of); Valiaghaie, Soma [Islamic Azad University, Sanandaj (Iran, Islamic Republic of); Soufiani, Ahad Rounaghi [Islamic Azad University, Sufian (Iran, Islamic Republic of)
2014-10-15
By virtue of the efficiency of the Dirichlet-to-Neumann map method, we have calculated, for H-polarization (TE mode), the band structure of 2D photonic crystals with a square lattice composed of metallic rods embedded in an air background. The rod in the unit cell is chosen to be circular in shape. Here, from a practical point of view, in order to obtain maximum band gaps, we have studied the band structure as a function of the size of the rods. We have also studied the flat bands appearing in the band structures and have shown that for frequencies around the surface plasmon frequency, the modes are highly localized at the interface between the metallic rods and the air background.
Sedghi, Aliasghar; Valiaghaie, Soma; Soufiani, Ahad Rounaghi
2014-10-01
By virtue of the efficiency of the Dirichlet-to-Neumann map method, we have calculated, for H-polarization (TE mode), the band structure of 2D photonic crystals with a square lattice composed of metallic rods embedded in an air background. The rod in the unit cell is chosen to be circular in shape. Here, from a practical point of view, in order to obtain maximum band gaps, we have studied the band structure as a function of the size of the rods. We have also studied the flat bands appearing in the band structures and have shown that for frequencies around the surface plasmon frequency, the modes are highly localized at the interface between the metallic rods and the air background.
Gupta, Akanksha; Ganesh, Rajaraman; Joy, Ashwin
2016-11-01
In Navier-Stokes fluids, shear flows are known to become unstable leading to instability and eventually to turbulence. A class of flow namely, Kolmogorov Flows (K-Flows) exhibit such transition at low Reynolds number. Using fluid and molecular dynamics, we address the physics of transition from laminar to turbulent regime in strongly correlated-liquids such as in multi-species plasmas and also in naturally occurring plasmas with K-Flows as initial condition. A 2D phenomenological generalized hydrodynamic model is invoked wherein the effect of strong correlations is incorporated via a viscoelastic memory. To study the stability of K-Flows or in general any shear flow, a generalized eigenvalue solver has been developed along with a spectral solver for the full nonlinear set of fluid equations. A study of the linear and nonlinear features of K-Flow in incompressible and compressible limit exhibits cyclicity and nonlinear pattern formation in vorticity. A first principles based molecular dynamics simulation of particles interacting via Yukawa potential is performed with features such as configurational and kinetic thermostats for K-Flows. This work reveals several interesting similarities and differences between hydrodynamics and molecular dynamics studies.
Yang, H.; Chemia, Zurab; Artemieva, Irina
and geophysical studies, the geodynamic origin and evolution of the BRZ is still debated. We applytwo-dimensional finite difference code to model the lithosphere-scale de-formation in several locations across the strike of the Baikal Rift zone. The model se-tup takes an advantage of regional geophysical models...... to determinethe set of parameters that may define regional li-thosphere evolution towards the present lithosphere structure, which we further con-trol by gravity data, regional volcanism, and the age of the BRZ formation. We dem-onstrate the roleof pre-existing faults on the BRZ evolution and on formation of "off...
Dear, J. P.; Field, J. E.; Swallowe, G. M.
1985-02-01
The techniques described in this paper were developed during a study of high velocity liquid/solid impact. This form of impact is relevant to a number of technological problems such as the rain erosion of aircraft, the erosion of steam turbine blades, cavitation damage and the cleaning, cutting or fragmentation of materials using high velocity liquid jets. There are advantages in creating two-dimensional impact geometries since these enable processes occurring inside the impacted liquid mass and the onset of jetting to be studied in detail. Liquid wedge and drop geometries are produced by first casting water/gelatine sheets and then cutting out the required shapes. The impacting solid is a plate fired from a rectangular bore gas gun. The impact is viewed at high magnification using high speed photography at microsecond framing rates with an Imacon camera, and the shocks are visulised using Schlieren photography. The results give information on the shock structures produced, the "water hammer" and "edge" pressures and the critical conditions for jetting. The two-dimensional techniques have also been applied to studies of cavity collapse. In this case, a single cavity, or an array of cavities, is formed in the gelatine layer. An advantage of the technique is that the cavity size and spacing can be accurately controlled. It is well known that when a shock passes over a cavity, a jet is formed in the direction of the shock, by involution of the cavity surface. The impact of this jet onto a solid surface is an important feature of cavitation damage. In our experiments, we have also studied shocks passing over an array of cavities. Cavity collapse is also important as an ignition mechanism with explosives and as a source of "hot-spots" which aid the build-up to, and propagation of, fast reaction in explosives. However, there is still controversy about the relative importance of adiabatic heating of the gas in the cavity and shock heating when the jet impacts the far side
Study and characterization of interfaces in a two-dimensional generalized voter model
Bordogna, Clelia M.; Albano, Ezequiel V.
2011-04-01
We propose and study, by means of numerical simulations, the time evolution of interfaces in a generalized voter model in d=2 dimensions. In this model, a randomly selected voter can change his or her opinion (state) with a certain probability that is an algebraic function of the average opinion of his or her nearest neighbors. By starting with well-defined (sharp) interfaces between two different states of opinion, we measure the time dependence of the interface width (w), which behaves as a power law, i.e., w∝tδ. In this way we characterized three different types of interfaces: (i) between an ordered phase (consensus) and a disordered one (δ=1/2); (ii) between ordered phases having different states of opinion (δ=1/2), which corresponds to interface coarsening without surface tension; and (iii) as in (ii) but considering surface tension. Here, we observe a finite-size induced crossover with exponents δ=1/4 and δ=1/2 for early and longer times, respectively. So, our study allows for the characterization of interfaces of quite different nature in a unified fashion, providing insight into the understanding of interface coarsening with and without surface tension.
Experimental study of two-dimensional helium mixture films adsorbed on graphite
Patel, H
2002-01-01
sup 3 He- sup 4 He mixture films adsorbed on graphite were studied down to temperatures below 1 mK using heat capacity and nuclear magnetic resonance (NMR) to probe the system. This work represents the first measurements in this temperature range of the various systems studied. The work focused on two types of mixtures, sup 3 He- sup 4 He mixtures within the second layer, and sup 3 He floating on three layers of sup 4 He. For mixtures within the layer, a homogeneous mixed phase was observed, followed by a phase interpreted as a Fermi liquid of sup 3 He quasiparticle excitations tunneling within a solid sup 4 He lattice. For the second type of mixture, the expected occupancy of the first excited surface normal state was observed. This is accompanied by anomalous behaviour at low temperatures (T < 10 mK) which arises due to a low concentration of sup 3 He atoms being pushed into the third superfluid sup 4 He layer. An NMR spectrometer utilising a cooled differential preamplifier operating at 4 K was develope...
Study of deformed quasi-periodic Fibonacci two dimensional photonic crystals
Ben Abdelaziz, K.; Bouazzi, Y.; Kanzari, M.
2015-09-01
Quasi-periodic photonic crystals are not periodic structures. These structures are generally obtained by the arrangement of layers according to a recursive rule. Properties of these structures make more attention the researchers especially in the case when applying defects. So, photonic crystals with defects present localized modes in the band gap leading to many potential applications such light localization. The objective of this work is to study by simulation the effect of the global deformation introduced in 2D quasiperiodic photonic crystals. Deformation was introduced by applying a power law, so that the coordinates y of the deformed object were determined through the coordinates x of the non-deformed structure in accordance with the following rule: y = x1+k. Here k is the coefficient defining the deformation. Therefore, the objective is to study the effect of this deformation on the optical properties of 2D quasiperiodic photonic crystals, constructed by Fibonacci generation. An omnidirectional mirror was obtained for optimization Fibonacci iteration in a part of visible spectra.
Shukla, Chandrasekhar; Das, Amita, E-mail: amita@ipr.res.in [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India); Patel, Kartik [Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)
2015-11-15
Relativistic electron beam propagation in plasma is fraught with several micro instabilities like two stream, filamentation, etc., in plasma. This results in severe limitation of the electron transport through a plasma medium. Recently, however, there has been an experimental demonstration of improved transport of Mega Ampere of electron currents (generated by the interaction of intense laser with solid target) in a carbon nanotube structured solid target [G. Chatterjee et al., Phys. Rev. Lett. 108, 235005 (2012)]. This then suggests that the inhomogeneous plasma (created by the ionization of carbon nanotube structured target) helps in containing the growth of the beam plasma instabilities. This manuscript addresses this issue with the help of a detailed analytical study and 2-D Particle-In-Cell simulations. The study conclusively demonstrates that the growth rate of the dominant instability in the 2-D geometry decreases when the plasma density is chosen to be inhomogeneous, provided the scale length 1/k{sub s} of the inhomogeneous plasma is less than the typical plasma skin depth (c/ω{sub 0}) scale. At such small scale lengths channelization of currents is also observed in simulation.
Two-dimensional wetting with binary disorder: a numerical study of the loop statistics
Garel, T.; Monthus, C.
2005-07-01
We numerically study the wetting (adsorption) transition of a polymer chain on a disordered substrate in 1+1 dimension. Following the Poland-Scheraga model of DNA denaturation, we use a Fixman-Freire scheme for the entropy of loops. This allows us to consider chain lengths of order N ˜105 to 106, with 104 disorder realizations. Our study is based on the statistics of loops between two contacts with the substrate, from which we define Binder-like parameters: their crossings for various sizes N allow a precise determination of the critical temperature, and their finite size properties yields a crossover exponent φ=1/(2-α) ≃0.5. We then analyse at criticality the distribution of loop length l in both regimes l ˜O(N) and 1 ≪l ≪N, as well as the finite-size properties of the contact density and energy. Our conclusion is that the critical exponents for the thermodynamics are the same as those of the pure case, except for strong logarithmic corrections to scaling. The presence of these logarithmic corrections in the thermodynamics is related to a disorder-dependent logarithmic singularity that appears in the critical loop distribution in the rescaled variable λ=l/N as λ↦1.
Delucia, James
We study various aspects of the linear and 2D (helically symmetric) nonlinear development of m = 1 resistive instabilities in the cylindrical spheromak. The cylindrical spheromak is a fictitious configuration in which the toroidal spheromak has been cut and straightened out to become a circular cylinder of radius a, length 2(pi)R, and with periodic boundary conditions. It has proven to be a usefull model for studying spheromak instabilities in which toroidal effects are not important. The majority of interest in this area lies in attempting to understand the effect that the resistive interchange instability has on confinement in the spheromak, the reason being that finite pressure spheromak configurations are always unstable to this mode. Therefore, most of the results presented in this thesis pertain to the nonlinear development of the resistive interchange mode. Our goal is to understand the quasilinear modifications of the equilibrium profile due to the growth of this instability, and the subsequent effect that the equilibrium modification has on the growth rate and eigenfunctions. Our studies of the resistive interchange mode reveal that mode saturation can occur due to the quasilinear flattening of the pressure profile in the vicinity of the mode rational surface. However, this saturation process is defeated when the plasma overheats and in regions of the plasma where the shear is low. Also, we found that fluid compression plays a significant, and optomistic role in the long term nonlinear development of this mode. Finally, in a tearing mode stable cylindrical spheromak configuration with an axial beta value of 6%, complete overlap of the m = 1 islands occurs in about 3% of the resistive skin time for a magnetic Reynold's number of S = 10('5). For typical parameters of the S-1 device at Princeton, this time corresponds to nearly one millisecond. We show that incorporation of the Hall terms into the resistive MHD model can stabilize the m = 1 resistive
A study of solar preflare activity using two-dimensional radio and SMM-XRP observations
Kundu, M. R.; Gopalswamy, N.; Saba, J. L. R.; Schmelz, J. T. S.; Strong, K. T.
1987-01-01
A study of type III activity at meter-decameter wavelengths in the preflare phase of the February 3, 1986 flare is presented, using data obtained with the Clark Lake Multifrequency Radioheliograph. This activity is compared with similar type III burst activity during the impulsive phase, and it is found that there is a displacement of burst sources between the onset and end times of the activity. A comparison of this displacement at three frequencies suggests that the type III emitting electrons gain access progressively to diverging and different field lines relative to the initial field lines. The energetics of the type III emitting electrons are inferred from observations and compared with those of the associated hard X-ray emitting electrons. The soft X-ray data from SMM-XRP show enhanced emission measure, density, and temperature in the region associated with the preflare type III activity.
Booi, Rebecca C; Carson, Paul L; O'Donnell, Matthew; Roubidoux, Marilyn A; Hall, Anne L; Rubin, Jonathan M
2008-01-01
Although simple cysts are easily identified using sonography, description and management of nonsimple cysts remains uncertain. This study evaluated whether the correlation coefficient differences between breast tissue and lesions, obtained from 2D breast elastography, could potentially distinguish nonsimple cysts from cancers and fibroadenomas. We hypothesized that correlation coefficients in cysts would be dramatically lower than surrounding tissue because noise, imaging artifacts, and particulate matter move randomly and decorrelate quickly under compression, compared with solid tissue. For this preliminary study, 18 breast lesions (7 nonsimple cysts, 4 cancers, and 7 fibroadenomas) underwent imaging with 2D elastography at 7.5 MHz through a TPX (a polymethyl pentene copolymer) 2.5 mm mammographic paddle. Breasts were compressed similar to mammographic positioning and then further compressed for elastography by 1 to 7%. Images were correlated using 2D phase-sensitive speckle tracking algorithms and displacement estimates were accumulated. Correlation coefficient means and standard deviations were measured in the lesion and adjacent tissue, and the differential correlation coefficient (DCC) was introduced as the difference between these values normalized to the correlation coefficient of adjacent tissue. Mean DCC values in nonsimple cysts were 24.2 +/- 11.6%, 5.7 +/- 6.3% for fibroadenomas, and 3.8 +/- 2.9 % for cancers (p < 0.05). Some of the cysts appeared smaller in DCC images than gray-scale images. These encouraging results demonstrate that characterization of nonsimple breast cysts may be improved by using DCC values from 2D elastography, which could potentially change management options of these cysts from intervention to imaging follow-up. A dedicated clinical trial to fully assess the efficacy of this technique is recommended.
High-field studies of quantum oscillations in quasi-two-dimensional organic metals
Sandhu, Pravindrajit
The organic metals derived from the molecule BEDT-TTF (or ET for short) are important as model systems for the study of low-dimensional phenomena. These materials are molecular crystals with a low Fermi energy (10--100 meV), high mobility (˜104 cm2/Vs) and highly anisotropic Fermi surfaces. We have conducted experimental studies of ( i) the Shubnikov-de Haas (SdH) effect in pulsed fields up to 50 T and (ii) the de Haas-van Alphen (dHvA) effect in steady fields up to 33 T on alpha - (ET)2 MHg(SCN) 4 (where M = K, Tl and NH4) and kappa - (ET)2 Cu (NCS)2. At these high fields, the wave shape as well as the temperature and field-dependence of the oscillations deviate from the behavior predicted by the standard Lifshitz-Kosevich theory. These measurements reveal the limits of the conventional theory of metals and lay the ground-work for extending the theory to low-dimensional systems. We have also performed extended Huckel tight-binding calculations to model the effects of pressure and uniaxial stress on the electronic band structure of kappa - (ET)2 KHg (SCN)4 and kappa - (ET)2 Cu (NCS)2. The calculated changes in the Fermi surface topology are in excellent agreement with the experimental values determined from SdH measurements. We also report predictions of the effects of uniaxial stress in the transverse directions and discuss the behavior of the effective mass and magnetic breakdown probability. Finally, we have investigated the origin of anomalous magnetic breakdown frequencies in the dHvA effect that are forbidden according to semi-classical theories. We construct a tight-binding model based on the realistic band-structure of the system, which is then solved numerically to compute the field-dependence of the magnetization. This model provides a natural description for the phenomenon of magnetic breakdown between co-existing closed and open Fermi surfaces and accounts for the anomalous frequencies that are observed experimentally. The occurrence of these
Wetting transition in the two-dimensional Blume-Capel model: A Monte Carlo study
Albano, Ezequiel V.; Binder, Kurt
2012-06-01
The wetting transition of the Blume-Capel model is studied by a finite-size scaling analysis of L×M lattices where competing boundary fields ±H1 act on the first or last row of the L rows in the strip, respectively. We show that using the appropriate anisotropic version of finite-size scaling, critical wetting in d=2 is equivalent to a “bulk” critical phenomenon with exponents α=-1, β=0, and γ=3. These concepts are also verified for the Ising model. For the Blume-Capel model, it is found that the field strength H1c(T) where critical wetting occurs goes to zero when the bulk second-order transition is approached, while H1c(T) stays nonzero in the region where in the bulk a first-order transition from the ordered phase, with nonzero spontaneous magnetization, to the disordered phase occurs. Interfaces between coexisting phases then show interfacial enrichment of a layer of the disordered phase which exhibits in the second-order case a finite thickness only. A tentative discussion of the scaling behavior of the wetting phase diagram near the tricritical point is also given.
Tu, J.; Song, P.
2016-12-01
We have developed a new numerical simulation model of the ionosphere/thermosphere by using an inductive-dynamic approach (including self-consistent solutions of Faraday's law and retaining inertia terms in ion momentum equations), that is, based on magnetic field B and plasma velocity v (B, v paradigm), which is distinctive from the conventional modeling based on electric field E and current j. The model solves self-consistently time-dependent continuity, momentum, and energy equations for multiple species of ions and neutrals including photochemistry, and Maxwell's equations. The governing equations solved in the model are a set of multifluid-collisional-Hall MHD equations which are one of unique features of our ionosphere/thermosphere model. With such an inductive-dynamic approach, not only sound wave mode but also all possible MHD wave modes are retained in the solutions of the governing equations so that the dynamic coupling between the magnetosphere and ionosphere and among different regions of the ionosphere can be self-consistently investigated. In the present study, we demonstrate dynamic propagation of field-aligned currents and ionospheric electric field carried by Alfven waves, as well as formation of closure horizontal currents (Pedersen currents in the E-region), indicating that the M-I coupling is via the Alfven waves instead of the field-aligned currents or electric field mapping. The simulation results also show that the Poynting flux and strongest energy dissipation in the ionosphere/thermosphere is in the regions of the largest ion velocities and not necessarily in the auroral oval where the field-aligned currents reside. The frictional heating increases plasma temperature and thus drives ion upflows. The frictional heating also increase neutral temperature and produces neutral upflows but in a much longer time scale. Furthermore, the coupling of high-to-low latitude ionosphere is investigated in terms of propagation of fast MHD waves.
Dumont, Maitena; Laurin, Michel; Jacques, Florian; Pellé, Eric; Dabin, Willy; de Buffrénil, Vivian
2013-05-01
Inner vertebral architecture is poorly known, except in human and laboratory animals. In order to document this topic at a broad comparative level, a 2D-histomorphometric study of vertebral centra was conducted in a sample of 98 therian mammal species, spanning most of the size range and representing the main locomotor adaptations known in therian taxa. Eleven variables relative to the development and geometry of trabecular networks were extracted from CT scan mid-sagittal sections. Phylogeny-informed statistical tests were used to reveal the respective influences of phylogeny, size, and locomotion adaptations on mammalian vertebral structure. The use of random taxon reshuffling and squared change parsimony reveals that 9 of the 11 characteristics (the two exceptions are total sectional area and structural polarization) contain a phylogenetic signal. Linear discriminant analyses suggest that the sampled taxa can be arranged into three categories with respect to locomotion mode: a) terrestrial + flying + digging + amphibious forms, b) coastal oscillatory aquatic taxa, and c) pelagic oscillatory aquatic forms represented by oceanic cetaceans. Pairwise comparison tests and linear regressions show that, when specific size increases, the length of trabecular network (Tt.Tb.Le), as well as trabecular proliferation in total sections (Pr.Tb.Tt), increase with positive allometry. This process occurs in all locomotion categories but is particularly pronounced in pelagic oscillators. Conversely, mean trabecular width has a lesser increase with size in pelagic oscillators. Trabecular orientation is not influenced by size. All tests were corrected for multiple testing. By using six structural variables or indices, locomotion mode can be predicted with a 97.4% success rate for terrestrial forms, 66.7% for coastal oscillatory, and 81.3% for pelagic oscillatory. The possible functional meaning of these results and their potential use for paleobiological inference of locomotion in
K. R. pardasani
2005-01-01
Full Text Available In this study, a two dimensional infinite element model has been developed to study thermal effect in human dermal regions due to tumors. This model incorporates the effect of blood mass flow rate, metabolic heat generation and thermal conductivity of the tissues.The dermal region is divided into three natural layers, namely, epidermis, dermis and subdermal tissues. A uniformly perfused tumor is assumed to be present in the dermis. The domain is assumed to be finite along the depth and infinite along the breadth. The whole dermis region involving tumor is modelled with the help of triangular finite elements to incorporate the geometry of the region. These elements are surrounded by infinite domain elements along the breadth. Appropriate boundary conditions has been incorporated. A computer program has been developed to obtain the numerical results.
Kong, Wei; Yang, Fang; Liu, Songfen; Shi, Feng
2016-10-01
A Langevin dynamics simulation method is used to study the two-dimensional (2D) equilibrium structure of complex plasmas while considering an external magnetic field. The traditional Yukawa potential and a modified Yukawa potential according to Shukla et al. [Phys. Lett. A 291, 413 (2001); Shukla and Mendonca, Phys. Scr. T113 82 (2004)] and Salimullah et al. [Phys. Plasmas 10, 3047 (2003)] respectively, are employed to account for the interaction of the charged dust particles. It is found that the collisions between neutral gas and charged dust particles have minor effects on the 2D equilibrium structure of the system. Based on the modified Yukawa potential, studies on the 2D equilibrium structure show that the traditional Yukawa potential is still suitable for describing the magnetized complex plasmas, even if the shielding distance of charged dust particles is affected by the strong external magnetic field.
Picariello, Gianluca; De Martino, Alessandra; Mamone, Gianfranco; Ferranti, Pasquale; Addeo, Francesco; Faccia, Michele; Spagnamusso, Salvatore; Di Luccia, Aldo
2006-03-20
In the present study, an alternative procedure for two-dimensional (2D) electrophoretic analysis in proteomic investigation of the most represented basic muscle water-soluble proteins is suggested. Our method consists of Acetic acid-Urea-Triton polyacrylamide gel (AUT-PAGE) analysis in the first dimension and standard sodium dodecyl sulphate polyacrylamide gel (SDS-PAGE) in the second dimension. Although standard two-dimensional Immobilized pH Gradient-Sodium Dodecyl-Sulphate (2D IPG-SDS) gel electrophoresis has been successfully used to study these proteins, most of the water-soluble proteins are spread on the alkaline part of the 2D map and are poorly focused. Furthermore, the similarity in their molecular weights impairs resolution of the classical approach. The addition of Triton X-100, a non-ionic detergent, into the gel induces a differential electrophoretic mobility of proteins as a result of the formation of mixed micelles between the detergent and the hydrophobic moieties of polypeptides, separating basic proteins with a criterion similar to reversed phase chromatography based on their hydrophobicity. The acid pH induces positive net charges, increasing with the isoelectric point of proteins, thus allowing enhanced resolution in the separation. By using 2D AUT-PAGE/SDS electrophoresis approach to separate water-soluble proteins from fresh pork and from dry-cured products, we could spread proteins over a greater area, achieving a greater resolution than that obtained by IPG in the pH range 3-10 and 6-11. Sarcoplasmic proteins undergoing proteolysis during the ripening of products were identified by Matrix Assisted Laser Desorption/Ionization-Time of Flight (MALDI-ToF) mass spectrometry peptide mass fingerprinting in a easier and more effective way. Two-dimensional AUT-PAGE/SDS electrophoresis has allowed to simplify separation of sarcoplasmic protein mixtures making this technique suitable in the defining of quality of dry-cured pork products by immediate
Wang, Pengfei; Semenova, Yuliya; Zheng, Jie; Wu, Qiang; Muhamad Hatta, Agus; Farrell, Gerald
2011-06-01
A numerical study is carried out to compare the two-dimensional (2-D) case and three-dimensional (3-D) case for the modelling of an ion-exchanged glass waveguide. It is shown that different waveguide widths on the photomask correspond to different ion concentration distributions after an annealing process. A numerical example is presented of two waveguide sections with different widths indicates that due to the abrupt change of the waveguide width, a 3-D theoretical model is required for an accurate prediction of the parameters of ion-exchanged glass waveguides. The good agreement between the modelled and measured results proves that the developed 3-D numerical model can be beneficially utilized in the generalized design of optical devices based on ion-exchange waveguides.
Küchler, Sebastian; Meurer, Thomas; Jacobs, Laurence J; Qu, Jianmin
2009-03-01
This study investigates two-dimensional wave propagation in an elastic half-space with quadratic nonlinearity. The problem is formulated as a hyperbolic system of conservation laws, which is solved numerically using a semi-discrete central scheme. These numerical results are then analyzed in the frequency domain to interpret the nonlinear effects, specifically the excitation of higher-order harmonics. To quantify and compare the nonlinearity of different materials, a new parameter is introduced, which is similar to the acoustic nonlinearity parameter beta for one-dimensional longitudinal waves. By using this new parameter, it is found that the nonlinear effects of a material depend on the point of observation in the half-space, both the angle and the distance to the excitation source. Furthermore it is illustrated that the third-order elastic constants have a linear effect on the acoustic nonlinearity of a material.
Chih-Wen Chiang
2012-01-01
Full Text Available Uncertain physical properties of methane hydrate (MH above a bottom simulating reflector should be estimated for detecting MH-bearing formations. In contrast to general marine sediments, MH-bearing formations have a relatively high electrical resistivity. Therefore, marine electrical resistivity imaging (MERI is a well-suited method for MH exploration. The authors conducted sensitivity testing of sub-seafloor MH exploration using a two-dimensional (2D inversion algorithm with the Wenner, Pole-Dipole (PD and Dipole-Dipole (DD arrays. The results of the Wenner electrode array show the poorest resolution in comparison to the PD and DD arrays. The results of the study indicate that MERI is an effective geophysical method for exploring the sub-seafloor electrical structure and specifically for delineating resistive anomalies that may be present because of MH-bearing formations at a shallow depth beneath the seafloor.
Nejati, Ammar; 10.1007/s11192-009-0103-1
2013-01-01
The quantity and quality of scientific output of the topmost 50 countries in the four basic sciences (agricultural and biological sciences, chemistry, mathematics, and physics and astronomy) are studied in the period of the recent 12 years (1996-2007). In order to rank the countries, a novel two-dimensional method is proposed, which is inspired by the H-index and other methods based on quality and quantity measures. The countries data are represented in a "quantity-quality diagram", and partitioned by a conventional statistical algorithm (k-means), into three clusters, members of which are rather the same in all of the basic sciences. The results offer a new perspective on the global positions of countries with regards to their scientific output.
Marcus, K.A.; Barends, M.; Morava, E.; Feuth, T.; Korte, C.L. de; Kapusta, L.
2011-01-01
BACKGROUND: Myocardial dysfunction in children diagnosed with mitochondrial disease is an ominous sign and has been associated with substantial increased mortality rates. Early detection of cardiac involvement would therefore be desirable. Two dimensional strain echocardiography (2DSTE) has proven t
Marcus, K.A.; Janousek, J.; Barends, M.E.; Weijers, G.; Korte, C.L. de; Kapusta, L.
2012-01-01
Two-dimensional speckle tracking echocardiography (2DSTE) offers valuable information in the echocardiographic assessment of ventricular myocardial function. It enables the quantification and timing of systolic ventricular myocardial deformation. In addition, 2DSTE can be used to identify mechanical
LIN Chang; ZHANG Xiu-Lian
2005-01-01
The nonlinear dust acoustic waves in two-dimensional dust plasma with dust charge variation is analytically investigated by using the formally variable separation approach. New analytical solutions for the governing equation of this system have been obtained for dust acoustic waves in a dust plasma for the first time. We derive exact analytical expressions for the general case of the nonlinear dust acoustic waves in two-dimensional dust plasma with dust charge variation.
Maloth, Saritha; Ganapathy, K S
2011-01-01
The present study was conducted to determine the most accurate bite mark overlay fabrication technique by studying two physical characteristics, i.e., area and rotation of biting edges of anterior teeth of thirty volunteers. The objective of the study was to evaluate the reliability and efficacy of five commonly used methods of human bite mark overlays using two dimensional (2D) digital images of dental study casts as a gold standard, to rank different methods according to statistically based determination of relative accuracy of each method and to determine its feasibility in Forensic science. Overlays were produced from the biting surfaces of six upper and six lower anterior teeth of 30 volunteers using the following five methods: a) hand tracing from study casts, b) hand tracing from wax impressions, c) xerographic method, d) radiopaque impression method and e) 2D computer-based method. Area of the biting edges of the anterior teeth and relative rotation of each anterior tooth were measured and compared. The xerographic method was determined to be the more accurate method with respect to tooth area and rotation. Hand tracing methods, from either wax impressions of teeth or directly from study casts, were determined to be inaccurate and subjective. It is recommended that forensic odontologists discontinue the use of hand tracing overlays in bite mark comparison cases as there is lot of scope for manipulation and observer bias.
D'Andrea, Antonello; D'Alto, Michele; Di Maio, Marco; Vettori, Serena; Benjamin, Nicola; Cocchia, Rosangela; Argiento, Paola; Romeo, Emanuele; Di Marco, Giovanni; Russo, Maria Giovanna; Valentini, Gabriele; Calabrò, Raffaele; Bossone, Eduardo; Grünig, Ekkehard
2016-07-01
Enlargement and dysfunction of the right atrium might be an early sign for pulmonary hypertension in systemic sclerosis (SSc). This is the first study to analyse right atrial morphology and function in SSc patients compared to healthy controls by speckle-tracking two-dimensional strain echocardiography (2DSE) at rest and during exercise. Furthermore, right atrial function was correlated with further clinical findings. Adult patients with SSc for >3 years (n = 90) and 55 age- and gender-matched healthy controls underwent a panel of non-invasive assessments including transthoracic echocardiography, pulsed Doppler myocardial imaging and 2DSE at rest and during exercise. Furthermore, serological tests and high-resolution chest computed tomography were performed. SSc patients showed significant impairment of right atrial function and the right atrial enlargement, measured by 2DSE at rest and during exercise compared to controls (both p right atrial lateral strain was significantly associated with PAPs during effort, right atrial area, left ventricle stroke volume and inferior vena cava diameter using multivariable analysis. The findings of this study suggest that a high proportion of SSc patients reveal right atrial dysfunction even without manifest pulmonary hypertension. Impaired right atrial function occurred mostly in patients with pulmonary fibrosis and/or elevated PAPs during exercise, was independently associated with prognostic factors and may therefore be useful for risk stratification. Further studies are needed to analyse if right atrial dysfunction assessed by 2DSE may help to improve early diagnosis of pulmonary hypertension.
Diverse anisotropy of phonon transport in two-dimensional group IV-VI compounds: A comparative study
Qin, Guangzhao; Qin, Zhenzhen; Fang, Wu-Zhang; Zhang, Li-Chuan; Yue, Sheng-Ying; Yan, Qing-Bo; Hu, Ming; Su, Gang
2016-05-01
New classes of two-dimensional (2D) materials beyond graphene, including layered and non-layered, and their heterostructures, are currently attracting increasing interest due to their promising applications in nanoelectronics, optoelectronics and clean energy, where thermal transport is a fundamental physical parameter. In this paper, we systematically investigated the phonon transport properties of the 2D orthorhombic group IV-VI compounds of GeS, GeSe, SnS and SnSe by solving the Boltzmann transport equation (BTE) based on first-principles calculations. Despite their similar puckered (hinge-like) structure along the armchair direction as phosphorene, the four monolayer compounds possess diverse anisotropic properties in many aspects, such as phonon group velocity, Young's modulus and lattice thermal conductivity (κ), etc. Especially, the κ along the zigzag and armchair directions of monolayer GeS shows the strongest anisotropy while monolayer SnS and SnSe show almost isotropy in phonon transport. The origin of the diverse anisotropy is fully studied and the underlying mechanism is discussed in details. With limited size, the κ could be effectively lowered, and the anisotropy could be effectively modulated by nanostructuring, which would extend the applications to nanoscale thermoelectrics and thermal management. Our study offers fundamental understanding of the anisotropic phonon transport properties of 2D materials, and would be of significance for further study, modulation and applications in emerging technologies.
Douglas, Amber M.
Graphene is a two-dimensional (2D) sp2-hybridized carbon-based material possessing properties which include high electrical conductivity, ballistic thermal conductivity, tensile strength exceeding that of steel, high flexural strength, optical transparency, and the ability to adsorb and desorb atoms and molecules. Due to the characteristics of said material, graphene is a candidate for applications in integrated circuits, electrochromic devices, transparent conducting electrodes, desalination, solar cells, thermal management materials, polymer nanocomposites, and biosensors. Despite the above mentioned properties and possible applications, very few technologies have been commercialized utilizing graphene due to the high cost associated with the production of graphene. Therefore, a great deal of effort and research has been performed to produce a material that provides similar properties, reduced graphene oxide due (RGO) to the ease of commercial scaling of the production processes. This material is typically prepared through the oxidation of graphite in an aqueous media to graphene oxide (GO) followed by reduction to yield RGO. Although this material has been extensively studied, there is a lack of consistency in the scientific community regarding the analysis of the resulting RGO material. In this dissertation, a study of the reduction methods for GO and an alternate 2D carbon-based material, humic acid (HA), followed by analysis of the materials using Raman spectroscopy and Energy Dispersive X-ray Spectroscopy (EDS). Means of reduction will include chemical and thermal methods. Characterization of the material has been carried out on both before and after reduction.
Palma, G; Zambrano, D
2008-12-01
In this paper we propose a method to study critical systems numerically, which combines collective-mode algorithms and renormalization group on the lattice. This method is an improved version of the Monte Carlo renormalization group in the sense that it has all the advantages of cluster algorithms. As an application we considered the 2D Ising model and studied whether scale invariance or universality are possible underlying mechanisms responsible for the approximate "universal fluctuations" close to a so-called bulk temperature T(L) . "Universal fluctuations" were first proposed in the work of Bramwell, Holdsworth, and Pinton [Nature (London) 396, 552 (1998)] and stated that the probability density function of a global quantity for very dissimilar systems, such as a confined turbulent flow and a two-dimensional (2D) magnetic system, properly normalized to the first two moments, becomes similar to the "universal distribution," originally obtained for magnetization in the 2D XY model in the low-temperature region. The results for the critical exponents and the renormalization-group flow of the probability density function are very accurate and show no evidence to support that the approximate common shape of the PDF should be related to both scale invariance or universal behavior.
Qin, Mingpu; Zhang, Shiwei
2016-01-01
Ground state properties of the Hubbard model on a two-dimensional square lattice are studied by the auxiliary-field quantum Monte Carlo method. Accurate results for energy, double occupancy, effective hopping, magnetization, and momentum distribution are calculated for interaction strengths of U/t from 2 to 8, for a range of densities including half-filling and n = 0.3, 0.5, 0.6, 0.75, and 0.875. At half-filling, the results are numerically exact. Away from half-filling, the constrained path Monte Carlo method is employed to control the sign problem. Our results are obtained with several advances in the computational algorithm, which are described in detail. We discuss the advantages of generalized Hartree-Fock trial wave functions and its connection to pairing wave functions, as well as the interplay with different forms of Hubbard-Stratonovich decompositions. We study the use of different twist angle sets when applying the twist averaged boundary conditions. We propose the use of quasi-random sequences, whi...
Hetland, Øyvind S; Nordam, Tor; Simonsen, Ingve
2016-01-01
The scattering of polarized light incident from one dielectric medium on its two-dimensional randomly rough interface with a second dielectric medium is studied. A reduced Rayleigh equation for the scattering amplitudes is derived for the case where p- or s-polarized light is incident on this interface, with no assumptions being made regarding the dielectric functions of the media. Rigorous, purely numerical, nonperturbative solutions of this equation are obtained. They are used to calculate the reflectivity and reflectance of the interface, the mean differential reflection coefficient, and the full angular distribution of the intensity of the scattered light. These results are obtained for both the case where the medium of incidence is the optically less dense medium, and in the case where it is the optically more dense medium. Optical analogues of the Yoneda peaks observed in the scattering of x-rays from metal surfaces are present in the results obtained in the latter case. Brewster scattering angles for d...
Magnetic and Structural Studies on Two-Dimensional Antiferromagnets (MCl)LaNb2O7 (M = Mn, Co, Cr)
Kitada, Atsushi; Tsujimoto, Yoshihiro; Nishi, Masakazu; Matsuo, Akira; Kindo, Koichi; Ueda, Yutaka; Ajiro, Yoshitami; Kageyama, Hiroshi
2016-03-01
We report magnetic and structural studies on the two-dimensional antiferromagnets (MCl)LaNb2O7 (M = Mn, Cr, Co), prepared by topochemical reactions of a layered perovskite RbLaNb2O7. Electron diffraction of these oxyhalides revealed a superstructure with a √{2}a × √{2}a cell for M = Mn and Co, and a 2a × 2a cell for M = Cr, indicating that the MCl networks are distorted from an ideal square lattice. Neutron diffraction experiments showed that M = Mn and Co exhibit a (π 0 π ) antiferromagnetic order as observed for the S = 1/2 counterparts. (CoCl)LaNb2O7 with a strong spin anisotropy shows an antiferro to weak-ferromagnetic transition at low field, followed by novel two-step metamagnetic transitions likely associated with a 1/2 plateau for 27-54 T. Possible spin structures under magnetic field are discussed in terms of an Ising-type model. By contrast, (CrCl)LaNb2O7 exhibits a (π π π ) order, which is the first observation among related oxyhalides, and a spin-flop transition at 12 T due to a weak spin anisotropy. These results suggest that a slight difference in the MCl structure and spin anisotropy provides a crucial influence on the magnetic properties.
Ab initio electronic transport study of two-dimensional silicon carbide-based p–n junctions
Zhou, Hanming; Lin, Xiao; Guo, Hongwei; Lin, Shisheng; Sun, Yiwei; Xu, Yang
2017-03-01
Two-dimensional silicon carbide (2d-SiC) is a viable material for next generation electronics due to its moderate, direct bandgap with huge potential. In particular, its potential for p–n junctions is yet to be explored. In this paper, three types of 2d-SiC-based p–n junctions with different doping configuration are modeled. The doping configurations refer to partially replacing carbon with boron or nitrogen atoms along the zigzag or armchair direction, respectively. By employing density functional theory, we calculate the transport properties of the SiC based p–n junctions and obtain negative differential resistance and high rectification ratio. We also find that the junction along the zigzag direction with lower doping density exhibits optimized rectification performance. Our study suggests that 2d-SiC is a promising candidate as a material platform for future nano-devices. Project supported by the National Science Foundation of China (Nos. 61474099, 61674127) and the ZJ-NSF (No. Z17F04003).
Xun, X; Erwin, J K; Bletscher, W; Choi, J; Kallenbach, S; Mansuripur, M
2001-12-10
We present the results of crystallization studies in thin-film samples of amorphous and crystalline Ge(x)Sb(y)Te(z). The experiments, conducted at moderately elevated temperatures, are based on measurements of the first-order diffraction efficiency from a two-dimensional periodic array of recorded marks. When the samples are slowly heated above room temperature, changes in the efficiencies of various diffracted orders give information about the on-going crystallization process within the sample. Two different compositions of the GeSbTe alloy are used in these experiments. Measurements on Ge(2)Sb(2.3)Te(5) films show crystallization dominated by nucleation. For the Sb-rich eutectic composition Ge-(SbTe), crystallization is found to be dominated by growth from crystalline boundaries. We also show that crystalline marks written by relatively high-power laser pulses are different in their optical properties from the regions crystallized by slow heating of the sample to moderate temperatures.
Kalyani Kathirgamanathan
2015-01-01
Full Text Available In this study two-dimensional FTIR analysis was applied to understand the temperature effects on processing cellulose solutions in imidazolium-based ionic liquids. Analysis of the imidazolium ion νC2–H peak revealed hydrogen bonding within cellulose solutions to be dynamic on heating and cooling. The extent of hydrogen bonding was stronger on heating, consistent with greater ion mobility at higher temperature when the ionic liquid network structure is broken. At ambient temperatures a blue shifted νC2–H peak was indicative of greater cation-anion interactions, consistent with the ionic liquid network structure. Both cellulose and water further impact the extent of hydrogen bonding in these solutions. The FTIR spectral changes appeared gradual with temperature and contrast shear induced rheology changes which were observed on heating above 70°C and cooling below 40°C. The influence of cellulose on solution viscosity was not distinguished on initial heating as the ionic liquid network structure dominates rheology behaviour. On cooling, the quantity of cellulose has a greater influence on solution rheology. Outcomes suggest processing cellulose in ionic liquids above 40°C and to reduce the impacts of cation-anion effects and enhance solubilisation, processing should be done at 70°C.
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
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.
Hadamard States and Two-dimensional Gravity
Salehi, H
2001-01-01
We have used a two-dimensional analog of the Hadamard state-condition to study the local constraints on the two-point function of a linear quantum field conformally coupled to a two-dimensional gravitational background. We develop a dynamical model in which the determination of the state of the quantum field is essentially related to the determination of a conformal frame. A particular conformal frame is then introduced in which a two-dimensional gravitational equation is established.
Topological defects in two-dimensional crystals
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.
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
Baykal, Cüneyt; Ergin, Ayşen; Güler, Işikhan
2014-01-01
transformation model, a two-dimensional depth-averaged numerical waveinduced circulation model, a sediment transport model, and a bottom evolution model. To validate and verify the numerical model, it is applied to several cases of laboratory experiments. Later, the model is applied to a shoreline change problem...
Wang, Hong-mei; Liu, Yue-jie; Wang, Hong-xia; Zhao, Jing-xiang; Cai, Qing-hai; Wang, Xuan-zhang
2013-12-01
Motivated by the great advance in graphene hydroxide--a versatile material with various applications--we performed density functional theory (DFT) calculations to study the functionalization of the two-dimensional hexagonal boron nitride (h-BN) sheet with hydroxyl (OH) radicals, which has been achieved experimentally recently. Particular attention was paid to searching for the most favorable site(s) for the adsorbed OH radicals on a h-BN sheet and addressing the roles of OH radical coverage on the stability and properties of functionalized h-BN sheet. The results indicate that, for an individual OH radica, the most stable configuration is that it is adsorbed on the B site of the h-BN surface with an adsorption energy of -0.88 eV and a magnetic moment of 1.00 μ(B). Upon adsorption of more than one OH radical on a h-BN sheet, however, these adsorbates prefer to adsorb in pairs on the B and its nearest N atoms from both sides of h-BN sheet without magnetic moment. An energy diagram of the average adsorption energy of OH radicals on h-BN sheet as a function of its coverage indicates that when the OH radical coverage reaches to 60 %, the functionalized h-BN sheet is the most stable among all studied configurations. More importantly, this configuration exhibits good thermal and dynamical stability at room temperature. Owing to the introduction of certain impurity levels, the band gap of h-BN sheet gradually decreases with increasing OH coverage, thereby enhancing its electrical conductivity.
Prokhorov, Valery V; Perelygina, Olga M; Pozin, Sergey I; Mal'tsev, Eugene I; Vannikov, Anatoly V
2015-12-01
Polymorphic J-aggregates of monomethine cyanine dye 3,3'-di(γ-sulfopropyl)-5,5'-dichlorotiamonomethinecyanine (TC) have been studied by fluorescence optical microscopy (FOM) and by atomic force microscopy (AFM). The in situ FOM observations in a solution drop distinguish two J-aggregate morphology classes: flexible strips and rigid rods. The AFM imaging of dried samples reveals a strong J-aggregate structural rearrangement under adsorption on a mica surface with the strips self-folding and the rods squashing into rectangular bilayers and much deeper destruction. In the present work, the following structural conclusions have been drawn on the basis of careful consideration of strip crystal habits and various structural features of squashed/destructed rods: (1) the tubular morphology of TC rods is directly proved by FOM measurements in the solution bulk; (2) the staircase model of molecular arrangement in strips is proposed explaining the characteristic ∼44° skew angle in strip vertices; (3) a model of tube formation by a close-packed helical winding of flexible monolayer strips is proposed and justified which explains the observed J-aggregate polymorphism and strip-to-rod polymorphic transformations in a wide spatiotemporal scale; (4) at a nanoscale, an unexpectedly complex quasi-one-dimensional organization in J-aggregate two-dimensional monolayers is observed by high-resolution AFM imaging of constituent nanostrips separated by a characteristic distance in the range of 6-10 nm. The obtained results indicate that the underlying monolayer structure is the same for all J-aggregate polymorphs.
Gorcester, Jeff; Rananavare, Shankar B.; Freed, Jack H.
1989-05-01
Electron spin-echo (ESE) and two-dimensional electron-electron double resonance (2D ELDOR) experiments have been performed as a function of director orientation and temperature in the smectic A phase of the liquid crystal S2 for the spin-probe PD-tempone(2×10-3 M). Over the entire temperature range studied (288-323 K) we observe significant 2D ELDOR cross peaks only for ΔMI =±1 indicative of 14N spin-relaxation and negligible Heisenberg exchange. From the angular dependent 14N spin-relaxation rates we obtain the dipolar spectral densities at the hyperfine (hf) frequency, whereas from a combination of ESE and 2D ELDOR we obtain the dipolar and Zeeman-dipolar spectral densities at zero frequency. The angular dependent spectral densities were successfully decomposed into their basic components in accordance with theory. The angular dependent spectral densities at the hf frequency are not predicted by a model of anisotropic rotational diffusion in a nematic orienting potential, but are consistent with predictions of a model due to Moro and Nordio of solute rototranslational diffusion in a McMillan-type potential. The angular dependence also indicates that order director fluctuations in the smectic phase are suppressed at frequencies on the order of 10 MHz. An additional contribution to solute reorientation due to cooperative hydrocarbon chain fluctuations is suggested to account for the behavior of the observed spectral densities at zero frequency. An evaluation of the relevance of several other dynamical models to this experimental work is also presented.
Huang, Yan [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); School of Information Science and Engineering, Dalian Polytechnic University, Dalian 116034 (China); Sun, Jizhong, E-mail: jsun@dlut.edu.cn [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Hu, Wanpeng; Sang, Chaofeng [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Wang, Dezhen, E-mail: wangdez@dlut.edu.cn [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)
2016-01-15
Highlights: • Thermal performance of three edge-shaped divertor tiles was assessed numerically. • All the divertor tiles exposed to type-I ELMs like ITER's will melt. • The rounded edge tile thermally performs the best in all tiles of interest. • The incident energy flux density was evaluated with structural effects considered. - Abstract: Thermal performance of the divertor tile with different edge shapes was assessed numerically along the poloidal direction by a two-dimensional heat conduction model with considering the geometrical effects of castellated divertor tiles on the properties of its adjacent plasma. The energy flux density distribution arriving at the castellated divertor tile surface was evaluated by a two-dimension-in-space and three-dimension-in-velocity particle-in-cell plus Monte Carlo Collisions code and then the obtained energy flux distribution was used as input for the heat conduction model. The simulation results showed that the divertor tiles with any edge shape of interest (rectangular edge, slanted edge, and rounded edge) would melt, especially, in the edge surface region of facing plasma poloidally under typical heat flux density of a transient event of type-I ELMs for ITER, deposition energy of 1 MJ/m{sup 2} in a duration of 600 μs. In comparison with uniform energy deposition, the vaporizing erosion was reduced greatly but the melting erosion was aggravated noticeably in the edge area of plasma facing diveror tile. Of three studied edge shapes, the simulation results indicated that the divertor plate with rounded edge was the most resistant to the thermal erosion.
Johnson, Matthew C; Rudolph, Frederik; Dreaden, Tina M; Zhao, Gengxiang; Barry, Bridgette A; Schmidt-Krey, Ingeborg
2010-10-29
Electron crystallography has evolved as a method that can be used either alternatively or in combination with three-dimensional crystallization and X-ray crystallography to study structure-function questions of membrane proteins, as well as soluble proteins. Screening for two-dimensional (2D) crystals by transmission electron microscopy (EM) is the critical step in finding, optimizing, and selecting samples for high-resolution data collection by cryo-EM. Here we describe the fundamental steps in identifying both large and ordered, as well as small 2D arrays, that can potentially supply critical information for optimization of crystallization conditions. By working with different magnifications at the EM, data on a range of critical parameters is obtained. Lower magnification supplies valuable data on the morphology and membrane size. At higher magnifications, possible order and 2D crystal dimensions are determined. In this context, it is described how CCD cameras and online-Fourier Transforms are used at higher magnifications to assess proteoliposomes for order and size. While 2D crystals of membrane proteins are most commonly grown by reconstitution by dialysis, the screening technique is equally applicable for crystals produced with the help of monolayers, native 2D crystals, and ordered arrays of soluble proteins. In addition, the methods described here are applicable to the screening for 2D crystals of even smaller as well as larger membrane proteins, where smaller proteins require the same amount of care in identification as our examples and the lattice of larger proteins might be more easily identifiable at earlier stages of the screening.
Kaneko, Yuta
2014-01-01
Introducing a Clebsch-like parameterization, we have formulated a canonical Hamiltonian system on a symplectic leaf of reduced magnetohydrodynamics. An interesting structure of the equations is in that the Lorentz-force, which is a quadratic nonlinear term in the conventional formulation, appears as a linear term -{\\Delta}Q, just representing the current density (Q is a Clebsch variable, and {\\Delta} is the two-dimensional Laplacian); omitting this term reduces the system into the two-dimensional Euler vorticity equation of a neutral fluid. A heuristic estimate shows that current sheets grow exponentially (even in a fully nonlinear regime) together with the action variable P that is conjugate to Q. By numerical simulation, the predicted behavior of the canonical variables, yielding exponential growth of current sheets, has been demonstrated.
Two-dimensional superconductivity of SmFeAsO0.85 single crystals: A fluctuation-conductivity study
Lee, Hyun-Sook; Park, Jae-Hyun; Lee, Jae-Yeap; Kim, Ju-Young; Sung, Nak-Heon; Cho, B. K.; Lee, Hu-Jong
2010-12-01
Temperature dependence of the in-plane conductance of a SmFeAsO0.85 single crystal is measured in c-axis and planar magnetic fields up to 7 T. The conductivity near the superconducting transition is well described by two-dimensional (2D) thermal-fluctuation theory. The 2D superconductivity arises as the c-axis coherence length is much shorter than the spacing between neighboring FeAs layers.
水坝绕流的数值研究%Numerical Study of Two-Dimensional Viscous Flow over Dams
王利兵; 刘宇陆; 涂敏杰
2003-01-01
In this paper, the characteristics of two-dimensional viscous flow over two dams were numerically investigated. The results show that the behavior of the vortices is closely related to the space between two dams, water depth, Fr number and Reynolds number. In addition, the flow properties behind each dam are different, and the changes over two dams are more complex than over one dam. Finally, the relevant turbulent characteristics were analyzed.
Madan Pal
2015-06-01
Full Text Available Aim: The objective of the study was to obtain and compare the two-dimensional (2D and three-dimensional (3D ultrasonographic images of pathological conditions of the stomach in dogs in clinical cases. Materials and Methods: In our study, 12 clinical conditions of the stomach were recorded using ultrasonography. The ultrasound machine used for this study was 3D ultrasound machine (Nemio-XG: Toshiba, Japan having four-dimensional volumetric transducer. Results: Present study was done to compare 2D and 3D ultrasonographic images in different gastric affections in dogs. In case of uremic gastropathy due to inflammatory response, the wall of the stomach was 0.6 cm thick and hyperechoic and gastric folds were also hyperechoic indicative of gastritis. In second, third, and fourth case of gastritis the wall of the stomach was 0.7, 0.6, and 0.55 cm, respectively thick and hyperechoic. In fifth and sixth case of gastritis, inflammatory response due to ingestion of polythene and sand led to gastritis and ultrasonographically, the wall of the stomach was 0.6 cm and 0.7 cm thick, respectively, and hyperechoic. In case of gastric ulcer, ultrasonographically, there was a disruption of gastric mucosal layer. In cases of gastric dilatation, anechoic content indicating fluid was seen in stomach area and due to dilatation boundary of the stomach was not clear and the increase in the lumen of the stomach was observed. In case of foreign body, ultrasonographically the wall of the stomach was 0.55 cm thick and hyperechoic. In the middle of the stomach, multiple hyperechoic shadows of the foreign bodies i.e. leather and bunch of straw of grass were observed. In case of pyloric stenosis ultrasonographically, anechoic lumen of the pylorus surrounded by 0.5 cm hypoechoic thickened muscle. In some cases, 3D ultrasonography was not diagnostic i.e. gastric foreign bodies and gastric dilatation. These conditions were better visualized on the 2D sonogram. Conclusion: The
Weakly disordered two-dimensional Frenkel excitons
Boukahil, A.; Zettili, Nouredine
2004-03-01
We report the results of studies of the optical properties of weakly disordered two- dimensional Frenkel excitons in the Coherent Potential Approximation (CPA). An approximate complex Green's function for a square lattice with nearest neighbor interactions is used in the self-consistent equation to determine the coherent potential. It is shown that the Density of States is very much affected by the logarithmic singularities in the Green's function. Our CPA results are in excellent agreement with previous investigations by Schreiber and Toyozawa using the Monte Carlo simulation.
Two-dimensional optical spectroscopy
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.
Peng, Yun; Sun, Bingjie; Wu, Peiyi
2008-03-01
Poly(vinylidene fluoride) (PVDF) converts easily into a thermo-reversible gel through crystallization by standing at room temperature in cyclohexanone. In this study, the Fourier transform infrared (FT-IR) spectra were measured continuously at room temperature during the conversion of the solution into a gel. The IR difference spectra derived from these spectra by absorbance subtraction clearly indicate the presence of PVDF alpha-crystallites in the gel due to the presence of absorption bands corresponding to the TG+TG- conformation of the alpha-phase. In the time interval from 25 to 45 min after the beginning of the experiment, the IR bands of PVDF increased dramatically, indicating the conversion of polymer chains from random statistical coils to the ordered TG+TG- conformation (alpha-form). In the time interval from 45 to 90 min, the IR bands of PVDF increased slowly, reflecting no further crystallization. Using two-dimensional (2D) IR analysis, it could be shown that the nu(C=O) absorption band of cyclohexanone changed during the gelation process. During the conformational ordering process (25-45 min), the nu(C=O) absorption band of the cyclohexanone dimer (1707 cm(-1)) decreased while the corresponding band of the monomer at 1718 cm(-1) increased. Furthermore, a new band at 1695 cm(-1) increased, which could be assigned to C=O groups of the solvent interacting with the CF2 groups in the polymer chain. The bands of the crystalline PVDF share positive cross-peaks with the bands of cyclohexanone, which indicates that the chain of PVDF changed prior to the cyclohexanone molecules during the conformational ordering process. However, these positive cross-peaks disappeared during the crystallization process, which means that the chain of PVDF changed synchronously with the solvent molecules. As for the bands of PVDF chains, the band at 762 cm(-1) varied prior to the bands at 873 cm(-1) and 796 cm(-1) during the conformational ordering process. The 762 cm(-1
Sawyer, Karma Rae [Univ. of California, Berkeley, CA (United States)
2008-12-01
Understanding chemical reactions requires the knowledge of the elementary steps of breaking and making bonds, and often a variety of experimental techniques are needed to achieve this goal. The initial steps occur on the femto- through picosecond time-scales, requiring the use of ultrafast spectroscopic methods, while the rate-limiting steps often occur more slowly, requiring alternative techniques. Ultrafast one and two-dimensional infrared and step-scan FTIR spectroscopies are used to investigate the photochemical reactions of four organometallic complexes. The analysis leads to a detailed understanding of mechanisms that are general in nature and may be applicable to a variety of reactions.
A Study of Electron and Phonon Dynamics by Broadband Two-Dimensional THz Time-Domain Spectroscopy
Fu, Zhengping
Terahertz (THz) wave interacts with semiconductors in many ways, such as resonant excitation of lattice vibration, intraband transition and polaron formation. Different from the optical waves, THz wave has lower photon energy (1 THz = 4.14 meV) and is suitable for studying dynamics of low-energy excitations. Recently the studies of the interaction of THz wave and semiconductors have been extending from the linear regime to the nonlinear regime, owing to the advance of the high-intensity THz generation and detection methods. Two-dimensional (2D) spectroscopy, as a useful tool to unravel the nonlinearity of materials, has been well developed in nuclear magnetic resonance and infrared region. However, the counterpart in THz region has not been well developed and was only demonstrated at frequency around 20 THz due to the lack of intense broadband THz sources. Using laser-induced plasma as the THz source, we developed collinear broadband 2D THz time-domain spectroscopy covering from 0.5 THz to 20 THz. Broadband intense THz pulses emitted from laser-induced plasma provide access to a variety of nonlinear properties of materials. Ultrafast optical and THz pulses make it possible to resolve the transient change of the material properties with temporal resolution of tens of femtoseconds. This thesis focuses on the linear and nonlinear interaction of the THz wave with semiconductors. Since a great many physical processes, including vibrational motion of lattice and plasma oscillation, has resonant frequency in the THz range, rich physics can be studies in our experiment. The thesis starts from the linear interaction of the THz wave with semiconductors. In the narrow band gap semiconductor InSb, the plasma absorption edge, Restrahlen band and dispersion of polaritons are observed. The nonlinear response of InSb in high THz field is verified in the frequency-resolved THz Z-scan experiment. The third harmonic generations due to the anharmonicity of plasma oscillation and the
Pan, Tsorng-Whay
2016-01-01
In this article we present a numerical method for simulating the sedimentation of circular particles in two-dimensional channel filled with a viscoelastic fluid of FENE-CR type, which is generalized from a domain/distributed Lagrange multiplier method with a factorization approach for Oldroyd-B fluids developed in [J. Non-Newtonian Fluid Mech. 156 (2009) 95]. Numerical results suggest that the polymer extension limit L for the FENE-CR fluid has no effect on the final formation of vertical chain for the cases of two disks and three disks in two-dimensional narrow channel, at least for the values of L considered in this article; but the intermediate dynamics of particle interaction before having a vertical chain can be different for the smaller values of L when increasing the relaxation time. For the cases of six particles sedimenting in FENE-CR type viscoelastic fluid, the formation of chain of 4 to 6 disks does depend on the polymer extension limit L. For the smaller values of L, FENE-CR type viscoelastic flu...
Diverse anisotropy of phonon transport in two-dimensional IV-VI compounds: A first-principles study
Qin, Guangzhao; Fang, Wu-Zhang; Zhang, Li-Chuan; Yue, Sheng-Ying; Yan, Qing-Bo; Hu, Ming; Su, Gang
2016-01-01
New class two-dimensional (2D) materials beyond graphene, including layered and non-layered, and their heterostructures, are currently attracting increasing interest due to their promising applications in nanoelectronics, optoelectronics and clean energy, where thermal transport property is one of the fundamental physical parameters. In this paper, we systematically investigated the phonon transport properties of 2D orthorhombic IV-VI compounds of $GeS$, $GeSe$, $SnS$ and $SnSe$ by solving the Boltzmann transport equation (BTE) based on first-principles calculations. Despite the similar puckered (hinge-like) structure along the armchair direction as phosphorene, the four monolayer compounds possess diverse anisotropic properties in many aspects, such as group velocity, Young's modulus and lattice thermal conductivity ($\\kappa$), etc. Especially, the $\\kappa$ along the zigzag and armchair directions of monolayer $GeS$ shows the strongest anisotropy while monolayer $SnS$ and $SnSe$ shows an almost isotropy in p...
Takaki, Tomohiro; Ohno, Munekazu; Shibuta, Yasushi; Sakane, Shinji; Shimokawabe, Takashi; Aoki, Takayuki
2016-05-01
Selections of growing crystals during directional solidification of a polycrystalline binary alloy were numerically investigated using two-dimensional phase-field simulations. To accelerate the simulations, parallel graphics processing unit (GPU) simulations were performed using the GPU-rich supercomputer TSUBAME2.5 at the Tokyo Institute of Technology. Twenty simulations with a combination of five sets of different seed orientation distributions and four different temperature gradients covering dendritic and cellular growth regions were performed. The unusual grain selection phenomenon, in which the unfavorably oriented grains preferentially grow instead of the favorably oriented grains, was observed frequently. The unusual selection was more remarkable in the cellular structure than in the dendritic structure.
Parz, P.; Faller, M. J.; Pippan, R.; Puff, W.; Würschum, R.
High-pressure torsion (HPT) was applied to the structural refinement of an age-hardenable Al-Cu alloy. HPT deformation gives rise to a grain refinement down to sizes of 100 nm and introduces various types of open volume defects. Positron annihilation spectroscopy (PAS), especially the chemical sensitive method of two-dimensional Doppler-broadening spectroscopy (2d-DB), was used for a detailed analysis of the deformation-induced vacancy-type defects and the vacancy-solute interaction. The correlation between microstructure and thermal annealing is discussed. HPT-deformed Al-3wt%Cu shows predominantly deformation-induced positron traps with a strongly reduced copper environment in comparison with the undeformed sample.
Dynamical phase transitions in the two-dimensional ANNNI model
Barber, M.N.; Derrida, B.
1988-06-01
We study the phase diagram of the two-dimensional anisotropic next-nearest neighbor Ising (ANNNI) model by comparing the time evolution of two distinct spin configurations submitted to the same thermal noise. We clearly se several dynamical transitions between ferromagnetic, paramagnetic, antiphase, and floating phases. These dynamical transitions seem to occur rather close to the transition lines determined previously in the literature.
Two-Dimensional Planetary Surface Lander
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.
PDF417码识别算法研究%Study on the Recognition Algorithms for Two-Dimensional Barcode
陈俊梅
2015-01-01
Along with the vigorous development of computer technology and signal processing technology,barcode,especially the two-dimensional barcode,is used more and more widely,in order to ensure the accuracy of the recognition of two-dimensional barcode,the recognition algorithms should be learned.Using an ordinary camera equipment, a PDF417 barcode image can be got with a lot of noise points,through the image processing which is realized by the MATLAB, the source code of the image can be got.During the process,different algorithms such as filtering , stratifing can be reduced to ensure the accuracy of the image decoding,and a series of problems which are caused by external disturbance such as image distortion,noise,motion artifacts can be reduced too.%随着计算机技术和信号处理技术的蓬勃发展，条形码尤其是二维条码在各个领域中的使用范围越来越广，为了保证对二维条码中所含信息识别的准确性，需要对条码的识别算法加以研究。本文以PDF417码为例，在普通的摄入环境下采集到干扰比较大的图像，利用MATLAB通过滤波、分层等算法对这样得到图像进行的一系列处理，最终得到图像的源代码。在处理过程中，保证了图像解码的准确性，减少了在普通摄入环境下可能产生的图像畸变、噪声干扰、运动伪影等干扰对条码识别的影响。
Wang, Li-Ping; Shen, Qi-Rong; Yu, Guang-Hui; Ran, Wei; Xu, Yang-Chun
2012-02-01
Detailed knowledge of the molecular events during composting is important in improving the efficiency of this process. By combining two-dimensional Fourier transform infrared (FTIR) correlation spectroscopy and multiple fluorescent labeling, it was possible to study the degradation of biopolymers during rapeseed meal and wheat bran composting. Two-dimensional FTIR correlation spectroscopy provided structural information and was used to deconvolute overlapping bands found in the compost FTIR spectra. The degradation of biopolymers in rapeseed meal and wheat bran composts followed the sequence: cellulose, heteropolysaccharides, and proteins. Fluorescent labeling suggested that cellulose formed an intact network-like structure and the other biopolymers were embedded in the core of this structure. The sequence of degradation of biopolymers during composting was related to their distribution patterns.
Kenfack Tsobnang, Patrice; Wenger, Emmanuel; Biache, Coralie; Lambi Ngolui, John; Ponou, Siméon; Dahaoui, Slimane; Lecomte, Claude
2014-10-01
The stacked two-dimensional supramolecular compound catena-{Co(amp)3Cr(ox)3·6H2O} (amp = 2-picolylamine, ox = oxalate) has been synthesized from the bimolecular approach using hydrogen bonds. It is built from layers in which both Co(amp)(3+) (D) and Cr(ox)(3-) (A) ions are bonded in a repeating DADADA… pattern along the a and c axes by multiple hydrogen bonds. These layers host a well resolved R12 dodecameric discrete ring of water clusters built by six independent molecules located around the 2c centrosymmetric Wyckoff positions of the P21/n space group in which the compound crystallizes. These clusters are ranged along the [001] direction, occupy 733.5 Å(3) (22.0%) of the unit cell and have a chair conformation via 12 hydrogen bonds. The water molecules of the cluster are linked with stronger hydrogen bonds than those between the cluster and its host, which explains the single continuous step of the dehydration process of the compound.
Abramavicius, Darius; Mukamel, Shaul
2009-04-30
Electronic excitations and the optical properties of the photosynthetic complex PSI are analyzed using an effective exciton model developed by Vaitekonis et al. [Photosynth. Res. 2005, 86, 185]. States of the reaction center, the linker states, the highly delocalized antenna states and the red states are identified and assigned in absorption and circular dichroism spectra by taking into account the spectral distribution of density of exciton states, exciton delocalization length, and participation ratio in the reaction center. Signatures of exciton cooperative dynamics in nonchiral and chirality-induced two-dimensional (2D) photon-echo signals are identified. Nonchiral signals show resonances associated with the red, the reaction center, and the bulk antenna states as well as transport between them. Spectrally overlapping contributions of the linker and the delocalized antenna states are clearly resolved in the chirality-induced signals. Strong correlations are observed between the delocalized antenna states, the linker states, and the RC states. The active space of the complex covering the RC, the linker, and the delocalized antenna states is common to PSI complexes in bacteria and plants.
Ozevin, Didem; Fazel, Hossein; Cox, Justin; Hardman, William; Kessler, Seth S.; Timmons, Alan
2014-04-01
Gearbox components of aerospace structures are typically made of brittle materials with high fracture toughness, but susceptible to fatigue failure due to continuous cyclic loading. Structural Health Monitoring (SHM) methods are used to monitor the crack growth in gearbox components. Damage detection methodologies developed in laboratory-scale experiments may not represent the actual gearbox structural configuration, and are usually not applicable to real application as the vibration and wave properties depend on the material, structural layers and thicknesses. Also, the sensor types and locations are key factors for frequency content of ultrasonic waves, which are essential features for pattern recognition algorithm development in noisy environments. Therefore, a deterministic damage detection methodology that considers all the variables influencing the waveform signature should be considered in the preliminary computation before any experimental test matrix. In order to achieve this goal, we developed two dimensional finite element models of a gearbox cross section from front view and shaft section. The cross section model consists of steel revolving teeth, a thin layer of oil, and retention plate. An ultrasonic wave up to 1 MHz frequency is generated, and waveform histories along the gearbox are recorded. The received waveforms under pristine and cracked conditions are compared in order to analyze the crack influence on the wave propagation in gearbox, which can be utilized by both active and passive SHM methods.
Arnab Roy; Umesh Varshney; Debnath Pal
2014-09-01
Acidic region streaking (ARS) is one of the lacunae in two-dimensional gel electrophoresis (2DE) of bacterial proteome. This streaking is primarily caused by nucleic acid (NuA) contamination and poses major problem in the downstream processes like image analysis and protein identification. Although cleanup and nuclease digestion are practiced as remedial options, these strategies may incur loss in protein recovery and perform incomplete removal of NuA. As a result, ARS has remained a common observation across publications, including the recent ones. In this work, we demonstrate how ultrasound wave can be used to shear NuA in plain ice-cooled water, facilitating the elimination of ARS in the 2DE gels without the need for any additional sample cleanup tasks. In combination with a suitable buffer recipe, IEF program and frequent paper-wick changing approach, we are able to reproducibly demonstrate the production of clean 2DE gels with improved protein recovery and negligible or no ARS. We illustrate our procedure using whole cell protein extracts from two diverse organisms, Escherichia coli and Mycobacterium smegmatis. Our designed protocols are straightforward and expected to provide good 2DE gels without ARS, with comparable times and significantly lower cost.
NONE
1998-03-01
The paper investigated/studied `space light modulation materials,` `dynamic hologram/memory materials,` `optical waveguide path materials,` etc. which become key materials in the high speed two dimensional processing. As to electrooptical materials proposed in this investigational study, the external electric field and the electric charges generated make quality of molecules themselves directly change to memory strong/weak signals of light. Therefore, the response velocity becomes less than a millionth of that of the liquid crystal display, and high speed which is needed for realtime moving image processing is anticipated. Hologram includes the phase information in addition to information on light strength. Therefore, it is a large capacity record medium and at the same time a record medium which can read/write two dimensional information as it is. With optical fiber, images cannot be transmitted as they are. Light waveguide path materials are those that accumulate roles of mirror and lens in a sheet of the material and construct a system which is strong in vibration, as optical parts connecting among materials for two dimensional data processing. 273 refs., 107 figs., 17 tabs.
Kraft, T; Xu, S; Brenner, B; Yu, L C
1999-03-01
To study possible structural changes in weak cross-bridge attachment to actin upon activation of the thin filament, two-dimensional (2D) x-ray diffraction patterns of skinned fibers from rabbit psoas muscle were recorded at low and high calcium concentration in the presence of saturating concentrations of MgATPgammaS, a nucleotide analog for weak binding states. We also studied 2D x-ray diffraction patterns recorded under relaxing conditions at an ionic strength above and below 50 mM, because it had been proposed from solution studies that reducing ionic strength below 50 mM also induces activation of the thin filament. For this project a novel preparation had to be established that allows recording of 2D x-ray diffraction patterns from single muscle fibers instead of natural fiber bundles. This was required to minimize substrate depletion or product accumulation within the fibers. When the calcium concentration was raised, the diffraction patterns recorded with MgATPgammaS revealed small changes in meridional reflections and layer line intensities that could be attributed in part to the effects of calcium binding to the thin filament (increase in I380, decrease in first actin layer line intensity, increase in I59) and in part to small structural changes of weakly attached cross-bridges (e.g., increase in I143 and I72). Calcium-induced small-scale structural rearrangements of cross-bridges weakly attached to actin in the presence of MgATPgammaS are consistent with our previous observation of reduced rate constants for attachment and detachment of cross-bridges with MgATPgammaS at high calcium. Yet, no evidence was found that weakly attached cross-bridges change their mode of attachment toward a stereospecific conformation when the actin filament is activated by adding calcium. Similarly, reducing ionic strength to less than 50 mM does not induce a transition from nonstereospecific to stereospecific attachment.
Tian, Zhenhua; Wu, Kun; Liu, Wentao; Shen, Lirui; Li, Guoying
2015-04-05
The thermal stability of collagen solution (5 mg/mL) crosslinked by glutaraldehyde (GTA) [GTA/collagen (w/w)=0.5] was measured by differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR), and the thermally induced structural changes were analyzed using two-dimensional (2D) correlation spectra. The denaturation temperature (Td) and enthalpy change (ΔH) of crosslinked collagen were respectively about 27°C and 88 J/g higher than those of native collagen, illuminating the thermal stability increased. With the increase of temperature, the red-shift of absorption bands and the decreased AIII/A1455 value obtained from FTIR spectra indicated that hydrogen bonds were weakened and the unwinding of triple helix occurred for both native and crosslinked collagens; whereas the less changes in red-shifting and AIII/A1455 values for crosslinked collagen also confirmed the increase in thermal stability. Additionally, the 2D correlation analysis provided information about the thermally induced structural changes. In the 2D synchronous spectra, the intensities of auto-peaks at 1655 and 1555 cm(-1), respectively assigned to amide I band (CO stretching vibration) and amide II band (combination of NH bending and CN stretching vibrations) in helical conformation were weaker for crosslinked collagen than those for native collagen, indicating that the helical structure of crosslinked collagen was less sensitive to temperature. Moreover, the sequence of the band intensity variations showed that the band at 1555 cm(-1) moved backwards owing to the addition of GTA, demonstrating that the response of helical structure of crosslinked collagen to the increased temperature lagged. It was speculated that the stabilization of collagen by GTA was due to the reinforcement of triple helical structure.
Two-dimensional function photonic crystals
Liu, Xiao-Jing; Liang, Yu; Ma, Ji; Zhang, Si-Qi; Li, Hong; Wu, Xiang-Yao; Wu, Yi-Heng
2017-01-01
In this paper, we have studied two-dimensional function photonic crystals, in which the dielectric constants of medium columns are the functions of space coordinates , that can become true easily by electro-optical effect and optical kerr effect. We calculated the band gap structures of TE and TM waves, and found the TE (TM) wave band gaps of function photonic crystals are wider (narrower) than the conventional photonic crystals. For the two-dimensional function photonic crystals, when the dielectric constant functions change, the band gaps numbers, width and position should be changed, and the band gap structures of two-dimensional function photonic crystals can be adjusted flexibly, the needed band gap structures can be designed by the two-dimensional function photonic crystals, and it can be of help to design optical devices.
AlGaAs/GaAs two-dimensional electron gas structures studied by photo reflectance spectroscopy
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.
Sadhukhan, Banasree; Singh, Prashant; Nayak, Arabinda; Datta, Sujoy; Johnson, Duane D.; Mookerjee, Abhijit
2017-08-01
We present a real-space formulation for calculating the electronic structure and optical conductivity of random alloys based on Kubo-Greenwood formalism interfaced with augmented space recursion technique [Mookerjee, J. Phys. C 6, 1340 (1973), 10.1088/0022-3719/6/8/003] formulated with the tight-binding linear muffin-tin orbital basis with the van Leeuwen-Baerends corrected exchange potential [Singh, Harbola, Hemanadhan, Mookerjee, and Johnson, Phys. Rev. B 93, 085204 (2016), 10.1103/PhysRevB.93.085204]. This approach has been used to quantitatively analyze the effect of chemical disorder on the configuration averaged electronic properties and optical response of two-dimensional honeycomb siliphene SixC1 -x beyond the usual Dirac-cone approximation. We predicted the quantitative effect of disorder on both the electronic structure and optical response over a wide energy range, and the results are discussed in the light of the available experimental and other theoretical data. Our proposed formalism may open up a facile way for planned band-gap engineering in optoelectronic applications.
Kraft, T; Xu, S.; Brenner, B; Yu, L C
1999-01-01
To study possible structural changes in weak cross-bridge attachment to actin upon activation of the thin filament, two-dimensional (2D) x-ray diffraction patterns of skinned fibers from rabbit psoas muscle were recorded at low and high calcium concentration in the presence of saturating concentrations of MgATPgammaS, a nucleotide analog for weak binding states. We also studied 2D x-ray diffraction patterns recorded under relaxing conditions at an ionic strength above and below 50 mM, because...
Gourgue, O.; Baeyens, W.; Chen, M. S.; de Brauwere, A.; de Brye, B.; Deleersnijder, E.; Elskens, M.; Legat, V.
2013-12-01
This paper presents the sediment module designed for the two-dimensional depth-averaged and one-dimensional section-averaged components of the finite-element model SLIM (Second-generation Louvain-la-Neuve Ice-ocean Model) in the framework of its application to the tidal part of the Scheldt Basin. This sediment transport module focuses on fine-grained, cohesive sediments. It is a necessary tool to undertake environmental biogeochemical studies, in which fine sediment dynamics play a crucial role.
Bu, Gui-jun; Yu, Jing; Di, Hui-hui; Luo, Shi-jia; Zhou, Da-zhai; Xiao, Qiang
2015-02-01
The composition and structure of humic acids formed during composting play an important influence on the quality and mature of compost. In order to explore the composition and evolution mechanism, municipal solid wastes were collected to compost and humic and fulvic acids were obtained from these composted municipal solid wastes. Furthermore, fourier transform infrared spectra and two-dimensional correlation analysis were applied to study the composition and transformation of humic and fulvic acids during composting. The results from fourier transform infrared spectra showed that, the composition of humic acids was complex, and several absorbance peaks were observed at 2917-2924, 2844-2852, 2549, 1662, 1622, 1566, 1454, 1398, 1351, 990-1063, 839 and 711 cm(-1). Compared to humic acids, the composition of fulvci acids was simple, and only three peaks were detected at 1725, 1637 and 990 cm(-1). The appearance of these peaks showed that both humic and fulvic acids comprised the benzene originated from lignin and the polysaccharide. In addition, humic acids comprised a large number of aliphatic and protein which were hardly detected in fulvic acids. Aliphatic, polysaccharide, protein and lignin all were degraded during composting, however, the order of degradation was different between humic and fulvci acids. The result from two-dimensional correlation analysis showed that, organic compounds in humic acids were degraded in the following sequence: aliphatic> protein> polysaccharide and lignin, while that in fulvic acids was as following: protein> polysaccharide and aliphatic. A large number of carboxyl, alcohols and ethers were formed during the degradation process, and the carboxyl was transformed into carbonates. It can be concluded that, fourier transform infrared spectra coupled with two-dimensional correlation analysis not only can analyze the function group composition of humic substances, but also can characterize effectively the degradation sequence of these
The separation of whale myoglobins with two-dimensional electrophoresis.
Spicer, G S
1988-10-01
Five myoglobins (sperm whale, Sei whale, Hubbs' beaked whale, pilot whale, and Amazon River dolphin) were examined using two-dimensional electrophoresis. Previous reports indicated that none of these proteins could be separated by using denaturing (in the presence of 8-9 M urea) isoelectric focusing. This result is confirmed in the present study. However, all the proteins could be separated by using denaturing nonequilibrium pH-gradient electrophoresis in the first dimension. Additionally, all the myoglobins have characteristic mobilities in the second dimension (sodium dodecyl sulfate), but these mobilities do not correspond to the molecular weights of the proteins. We conclude that two-dimensional electrophoresis can be more sensitive to differences in primary protein structure than previous studies indicate and that the assessment seems to be incorrect that this technique can separate only proteins that have a unit charge difference.
Yamada, K.; Ahmad, M. M.; Ogiso, Y.; Okuda, T.; Chikami, J.; Miehe, G.; Ehrenberg, H.; Fuess, H.
2004-07-01
RbSn2F5 is a two-dimensional fluoride ion conductor. It undergoes a first-order phase transition to a superionic state at 368 K. The structure of the low temperature phase has been determined from the Rietveld analysis of the X-ray powder diffraction. The dynamic properties of the fluoride ions in RbSn2F5 have been studied by impedance spectroscopy and solid state NMR. The dc ionic conductivity of this sample shows an abrupt increase at the phase transition temperature. We have obtained the hopping frequency and the concentration of the charge carriers (F- ions) at different temperatures from the analysis of the conductivity spectra using Almond-West formalism. The estimated values of the charge carriers’ concentration agree well with that determined from the structure and were found to be independent of temperature. The relatively small value of the power-law exponent, n ≈ 0.55, supports the two-dimensional property of the investigated material. Furthermore, 19F NMR with simulation has suggested the diffusive motions of the fluoride ions between different sites. In contrast, 119Sn and 87Rb NMR spectra below 250 K supported the intrinsic disordered nature due to the random distribution of the fluoride ion vacancies.
Vergentev, Tikhon; Bronwald, Iurii; Chernyshov, Dmitry; Gorfman, Semen; Ryding, Stephanie H M; Thompson, Paul; Cernik, Robert J
2016-10-01
Synchrotron X-rays on the Swiss Norwegian Beamline and BM28 (XMaS) at the ESRF have been used to record the diffraction response of the PMN-PT relaxor piezoelectric 67% Pb(Mg1/3Nb2/3)O3-33% PbTiO3 as a function of externally applied electric field. A DC field in the range 0-18 kV cm(-1) was applied along the [001] pseudo-cubic direction using a specially designed sample cell for in situ single-crystal diffraction experiments. The cell allowed data to be collected on a Pilatus 2M area detector in a large volume of reciprocal space using transmission geometry. The data showed good agreement with a twinned single-phase monoclinic structure model. The results from the area detector were compared with previous Bragg peak mapping using variable electric fields and a single detector where the structural model was ambiguous. The coverage of a significantly larger section of reciprocal space facilitated by the area detector allowed precise phase analysis.
Vergentev, Tikhon; Bronwald, Iurii; Chernyshov, Dmitry; Gorfman, Semen; Ryding, Stephanie H. M.; Thompson, Paul; Cernik, Robert J.
2016-01-01
Synchrotron X-rays on the Swiss Norwegian Beamline and BM28 (XMaS) at the ESRF have been used to record the diffraction response of the PMN–PT relaxor piezoelectric 67% Pb(Mg1/3Nb2/3)O3–33% PbTiO3 as a function of externally applied electric field. A DC field in the range 0–18 kV cm−1 was applied along the [001] pseudo-cubic direction using a specially designed sample cell for in situ single-crystal diffraction experiments. The cell allowed data to be collected on a Pilatus 2M area detector in a large volume of reciprocal space using transmission geometry. The data showed good agreement with a twinned single-phase monoclinic structure model. The results from the area detector were compared with previous Bragg peak mapping using variable electric fields and a single detector where the structural model was ambiguous. The coverage of a significantly larger section of reciprocal space facilitated by the area detector allowed precise phase analysis. PMID:27738414
TWO-DIMENSIONAL TOPOLOGY OF COSMOLOGICAL REIONIZATION
Wang, Yougang; Xu, Yidong; Chen, Xuelei [Key Laboratory of Computational Astrophysics, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012 China (China); Park, Changbom [School of Physics, Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 130-722 (Korea, Republic of); Kim, Juhan, E-mail: wangyg@bao.ac.cn, E-mail: cbp@kias.re.kr [Center for Advanced Computation, Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 130-722 (Korea, Republic of)
2015-11-20
We study the two-dimensional topology of the 21-cm differential brightness temperature for two hydrodynamic radiative transfer simulations and two semi-numerical models. In each model, we calculate the two-dimensional genus curve for the early, middle, and late epochs of reionization. It is found that the genus curve depends strongly on the ionized fraction of hydrogen in each model. The genus curves are significantly different for different reionization scenarios even when the ionized faction is the same. We find that the two-dimensional topology analysis method is a useful tool to constrain the reionization models. Our method can be applied to the future observations such as those of the Square Kilometre Array.
Two dimensional topology of cosmological reionization
Wang, Yougang; Xu, Yidong; Chen, Xuelei; Kim, Juhan
2015-01-01
We study the two-dimensional topology of the 21-cm differential brightness temperature for two hydrodynamic radiative transfer simulations and two semi-numerical models. In each model, we calculate the two dimensional genus curve for the early, middle and late epochs of reionization. It is found that the genus curve depends strongly on the ionized fraction of hydrogen in each model. The genus curves are significantly different for different reionization scenarios even when the ionized faction is the same. We find that the two-dimensional topology analysis method is a useful tool to constrain the reionization models. Our method can be applied to the future observations such as those of the Square Kilometer Array.
Celis, J E; Gesser, B; Dejgaard, K;
1989-01-01
Human cellular protein databases have been established using computer-analyzed 2D gel electrophoresis. These databases, which include information on various properties of proteins, offer a global approach to the study of regulation of cell proliferation and differentiation. Furthermore, thanks...
Towards two-dimensional search engines
Ermann, Leonardo; Chepelianskii, Alexei D.; Shepelyansky, Dima L.
2011-01-01
We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way the ranking of nodes becomes two-dimensional that paves the way for development of two-dimensional search engines of new type. Statistical properties of inf...
Girardi, D.; Branco, N. S.
2011-06-01
We study the Potts model on a rectangular lattice with aperiodic modulations in its interactions along one direction. Numerical results are obtained using the Wolff algorithm and for many lattice sizes, allowing for a finite-size scaling analyses to be carried out. Three different self-dual aperiodic sequences are employed, which leads to more precise results, since the exact critical temperature is known. We analyze two models, with 6 and 15 number of states: both present first-order transitions on their uniform versions. We show that the Harris-Luck criterion, originally introduced in the study of continuous transitions, is obeyed also for first-order ones. Also, we show that the new universality class that emerges for relevant aperiodic modulations depends on the number of states of the Potts model, as obtained elsewhere for random disorder, and on the aperiodic sequence. We determine the occurrence of log-periodic behavior, as expected for models with aperiodic modulated interactions.
Sabet Safa
2016-03-01
Full Text Available In the present study, the fluid flow in a periodic, non-isotropic dual scale porous media consisting of permeable square rods in inline arrangement is analyzed to determine permeability, numerically. The continuity and Navier-Stokes equations are solved to obtain the velocity and pressure distributions in the unit structures of the dual scale porous media for flows within Darcy region. Based on the obtained results, the intrinsic inter and intraparticle permeabilities and the bulk permeability tensor of the dual scale porous media are obtained for different values of inter and intraparticle porosities. The study is performed for interparticle porosities between 0.4 and 0.75 and for intraparticle porosities from 0.2 to 0.8. A correlation based on Kozeny-Carman relationship in terms of inter and intraparticle porosities and permeabilities is proposed to determine the bulk permeability tensor of the dual scale porous media.
Girardi, D; Branco, N S
2011-06-01
We study the Potts model on a rectangular lattice with aperiodic modulations in its interactions along one direction. Numerical results are obtained using the Wolff algorithm and for many lattice sizes, allowing for a finite-size scaling analyses to be carried out. Three different self-dual aperiodic sequences are employed, which leads to more precise results, since the exact critical temperature is known. We analyze two models, with 6 and 15 number of states: both present first-order transitions on their uniform versions. We show that the Harris-Luck criterion, originally introduced in the study of continuous transitions, is obeyed also for first-order ones. Also, we show that the new universality class that emerges for relevant aperiodic modulations depends on the number of states of the Potts model, as obtained elsewhere for random disorder, and on the aperiodic sequence. We determine the occurrence of log-periodic behavior, as expected for models with aperiodic modulated interactions.
Two-dimensional liquid chromatography
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...
Two-dimensional subwavelength plasmonic lattice solitons
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
Ali Ben Moussa
2012-10-01
Full Text Available In this work, the problem of hydrodynamic, heat and mass transfer and stability in a salt gradient solar pond has been numerically studied by means of computational fluid dynamics in transient regime. The body of the simulated pond is an enclosure of height H and length L wherein an artificial salinity gradient is created in order to suppress convective motions induced by solar radiation absorption and to stabilize the solar pond during the period of operation. Here we show the distribution of velocity, temperature and salt concentration fields during energy collection and storage in a solar pond filled with water and constituted by three different salinity zones. The bottom of the pond is blackened and the free-surface is subjected to heat losses by convection, evaporation and radiation while the vertical walls are adiabatic and impermeable. The governing equations of continuity, momentum, thermal energy and mass transfer are discretized by finite–volume method in transient regime. Velocity vector fields show the presence of thin convective cells in the upper convective zone (UCZ and large convective cells in the lower convective zone (LCZ. This study shows the importance of buoyancy ratio in the decrease of temperature in the UCZ and in the preservation of high temperature in the LCZ. It shows also the importance of the thickness of Non-Convective Zone (NCZ in the reduction of the upwards heat losses.
Hung, Ming-Jui; Ko, Ta; Liang, Chung-Yu; Kao, Yu-Cheng
2017-10-01
Although transient reduction in the left ventricular ejection fraction is characteristic of Takotsubo cardiomyopathy, little is known about the time-course changes of myocardial deformation in coronary vasospasm-related Takotsubo cardiomyopathy. We retrospectively analyzed the time-course changes in left ventricle, right ventricle, and left atrium strain values in a patient with coronary vasospasm-related Takotsubo cardiomyopathy. We found that not only left ventricular strain but also left atrial strain was abnormal during acute Takotsubo cardiomyopathy due to coronary vasospasm. Right ventricular free wall strain was normal. Coronary vasospasm-related Takotsubo cardiomyopathy. A serial echocardiographic study. The left ventricular strain was still subnormal despite a normalized left ventricular ejection fraction 2 months later. The left atrial strain was normal when the left ventricular ejection fraction normalized. From this limited experience, it is suggested that echocardiographic myocardial deformation analysis can provide more information than the standard ejection fraction in evaluating myocardial contractile function.
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.
Zheng Rui; Liu Bang-Gui
2012-01-01
In order to gain a deeper understanding of the quantum criticality in the explicitly staggered dimerized Heisenberg models,we study a generalized staggered dimer model named the J0 J1-J2 model,which corresponds to the staggered J J’ model on a square lattice and a honeycomb lattice when J1/J0 equals 1 and 0,respectively.Using the quantum Monte Carlo method,we investigate all the quantum critical points of these models with J1/J0 changing from 0 to 1as a function of coupling ratio α =J2/J0.We extract all the critical values of the coupling ratio αc for these models,and we also obtain the critical exponents v,β/v,and η using different finite-size scaling ans(a)tz,.All these exponents are not consistent with the three-dimensional Heisenberg universality class,indicating some unconventional quantum ciritcial points in these models.
Schoenfelder, Wiete; Gläser, Hans-Reinhard; Mitreiter, Ivonne; Stallmach, Frank
2008-06-01
Limestones and karstified limestones (dolostones) from a Permian aquifer in Central Germany were studied by 1H 2D NMR relaxometry and PFG NMR diffusometry, aiming at a non-destructive characterization of the pore space. Information concerning pore size distribution and water diffusion were in accord for different samples of each type of rock, but differed fundamentally between limestones and dolostones. The results of the 2D relaxometry measurements revealed a ratio of surface relaxation times Ts1/ Ts2 of about 2 for the limestones and about 4.5 for the dolostones, mirroring the different content of iron and manganese in the solid pore walls. In consideration of thin section interpretation, the corresponding fraction in the T1- T2 relaxation time distributions was attributed to interparticle porosity. Porosity of large vugs is clearly displayed by relaxation times longer than 1 s in the dolostones only. A third fraction of the total water-saturated pore space in the dolostones, which is clearly displayed in the 2D relaxation time distributions at the smallest relaxation times and a Ts1/ Ts2 ratio of about 12, is attributed to intrafossil porosity. The porosity classification, basing on non-destructive NMR experiments, is verified by mercury intrusion porosimetry and thin section interpretation.
McEwan, Neil A; Lu, Yi-Fang; Nuttall, Tim
2009-10-01
The aim of this study was to determine the dimensions of corneocytes collected from healthy dogs and cats, and from dogs suffering from atopic dermatitis. Samples were collected from the inner pinna, lateral thorax and the groin. D-Squame adhesive discs were used to collect corneocytes from the skin surface and image analysis software was used for measurements. Two differently shaped cells were identified in both animal species. The most common cell type was polygonal, often hexagonal or pentagonal and regular while the second type was smaller, elongated and variable in size and shape. The polygonal cells are corneocytes which probably originate from the interfollicular epidermis. The mean diameter and surface area for healthy canine polygonal corneocytes were 38-43.5 microm and 1092-1436 microm(2). The equivalent Figures for cats were 39.6-48.5 microm and 1183-1772 microm(2). Feline polygonal corneocytes were generally larger than those of the dog. Both feline and canine polygonal corneocytes collected from the ear were generally smaller than those from other body sites. Atopic canine polygonal corneocytes collected from the groin were significantly smaller than healthy groin corneocytes. In healthy dogs the mean length, breadth and surface area of elongated cells were 26.6-35.9 microm, 7.6-10.3 microm and 168.6-240.2 microm(2). The equivalent values for cats were 20.0-37.8 microm, 6.8-9.9 microm and 117.6-245.6 microm(2). The exact nature of the elongated cells is not known but they may be cell fragments or folded corneocytes. They were more common in densely haired skin suggesting the hair follicle as their origin.
Wan, Xiaoliang; Yu, Haijun; Weinan, E.
2015-05-01
In this work, we study the nonlinear instability of two-dimensional (2D) wall-bounded shear flows from the large deviation point of view. The main idea is to consider the Navier-Stokes equations perturbed by small noise in force and then examine the noise-induced transitions between the two coexisting stable solutions due to the subcritical bifurcation. When the amplitude of the noise goes to zero, the Freidlin-Wentzell (F-W) theory of large deviations defines the most probable transition path in the phase space, which is the minimizer of the F-W action functional and characterizes the development of the nonlinear instability subject to small random perturbations. Based on such a transition path we can define a critical Reynolds number for the nonlinear instability in the probabilistic sense. Then the action-based stability theory is applied to study the 2D Poiseuille flow in a short channel.
Two-dimensional materials and their prospects in transistor electronics.
Schwierz, F; Pezoldt, J; Granzner, R
2015-05-14
During the past decade, two-dimensional materials have attracted incredible interest from the electronic device community. The first two-dimensional material studied in detail was graphene and, since 2007, it has intensively been explored as a material for electronic devices, in particular, transistors. While graphene transistors are still on the agenda, researchers have extended their work to two-dimensional materials beyond graphene and the number of two-dimensional materials under examination has literally exploded recently. Meanwhile several hundreds of different two-dimensional materials are known, a substantial part of them is considered useful for transistors, and experimental transistors with channels of different two-dimensional materials have been demonstrated. In spite of the rapid progress in the field, the prospects of two-dimensional transistors still remain vague and optimistic opinions face rather reserved assessments. The intention of the present paper is to shed more light on the merits and drawbacks of two-dimensional materials for transistor electronics and to add a few more facets to the ongoing discussion on the prospects of two-dimensional transistors. To this end, we compose a wish list of properties for a good transistor channel material and examine to what extent the two-dimensional materials fulfill the criteria of the list. The state-of-the-art two-dimensional transistors are reviewed and a balanced view of both the pros and cons of these devices is provided.
Piezoelectricity in Two-Dimensional Materials
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.
Kronecker Product of Two-dimensional Arrays
Lei Hu
2006-01-01
Kronecker sequences constructed from short sequences are good sequences for spread spectrum communication systems. In this paper we study a similar problem for two-dimensional arrays, and we determine the linear complexity of the Kronecker product of two arrays. Our result shows that similar good property on linear complexity holds for Kronecker product of arrays.
Furtlehner, C. [Paris-6 Univ., 75 (France)
1997-09-24
This thesis deals with the two-dimensional problem of a charged particle coupled to a random magnetic field. Various situations are considered, according to the relative importance of the mean value of field and random component. The last one is conceived as a distribution of magnetic impurities (punctual vortex), having various statistical properties (local or non-local correlations, Poisson distribution, etc). The study of this system has led to two distinct situations: - the case of the charged particle feeling the influence of mean field that manifests its presence in the spectrum of broadened Landau levels; - the disordered situation in which the spectrum can be distinguished from the free one only by a low energy Lifshits behaviour. Additional properties are occurring in the limit of `strong` mean field, namely a non-conventional low energy behaviour (in contrast to Lifshits behaviour) which was interpreted in terms of localized states. (author) 78 refs.
Drichko, Natalia [Ioffe Physico-Technical Institute, Polytekhnicheskaya 26, 194021 St. Petersburg (Russian Federation); 1. Physikalisches Institut, Universitaet Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart (Germany)], E-mail: drichko@pi1.physik.uni-stuttgart.de; Dumm, Michael; Faltermeier, Daniel; Dressel, Martin [1. Physikalisches Institut, Universitaet Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart (Germany); Merino, Jaime [Dept. de Fisica Teorica de la Materia Condensada, Universidad Autonoma de Madrid (Spain); Greco, Andres [Facultad de Ciencias Exactas Ingenieria y Agrimensura e Instituto de Fisica Rosario (UNR-CONICET), Rosario (Argentina)
2007-09-01
We explore the effects of electronic correlations in quasi-two-dimensional BEDT-TTF-based organic conductors with half, quarter and 1/5-filled bands. Close to the Mott transition but still on the metallic side, quasiparticles are observed in the 1/2-filled systems only at temperatures well below 100 K, with a considerable growth of the Drude-like contribution. In contrast, the 1/4-filled conductors show a zero-frequency conduction peak already at room temperature which increases slightly upon cooling. Basically no change with temperature is observed for the Drude contribution of the 1/5-filled compound. Optical studies allow us to investigate the formation of quasiparticles at low temperature for systems of different filling. The strongest effect is observed in 1/2-filled compounds, it becomes weaker in 1/4 filled, while in the 1/5-filled compound no change of the Dude-peak on temperature is seen.
Celis, J E; Rasmussen, H H; Olsen, E
1994-01-01
The master two-dimensional (2-D) gel database of human keratinocytes currently lists 3087 cellular proteins (2168 isoelectric focusing, IEF; and 919 none-quilibrium pH gradient electrophoresis, NEPHGE), many of which correspond to posttranslational modifications, 890 polypeptides have been...... identified (protein name, organelle components, etc.) using one or a combination of procedures that include (i) comigration with known human proteins, (ii) 2-D gel immunoblotting using specific antibodies (iii) microsequencing of Coomassie Brilliant Blue stained proteins, (iv) mass spectrometry and (v...... in the database. We also report a database of proteins recovered from the medium of noncultured, unfractionated keratinocytes. This database lists 398 polypeptides (309 IEF; 89 NEPHGE) of which 76 have been identified. The aim of the comprehensive databases is to gather, through a systematic study...
Two-dimensional electron gas generated by La-doping at SrTiO3(001 surface: A first-principles study
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.
Zhang, Chun-hui; Zhang, Gui-jun; Sun, Su-qin; Tu, Ya
2010-07-01
2D-IR correlation spectroscopy was used to do the research on crude and prepared drug of radix scutellariae and the extracts of them. The results show that the holistic shape of peaks among them are similar in the FTIR spectra. In second derivative spectra, the two absorption peaks: 1,745 and 1,411 cm(-1) of processed products move to the bigger wavenumber direction, while 1,357 cm(-1) of processed products moves to the smaller wavenumber direction; There are conspicuous differences in Two-dimensional infrared correlation spectroscopy among them: Four characteristic peaks are shown between 1,300 and 1,800 cm(-1). The intensity of peak at 1,575 cm(-1) is the strongest. There are three main districts about the autopeaks of sliced scutellariae. Wine-fried scutellariae has two auto-peak districts, in which all the auto-peaks are positively correlated. The FTIR spectra of total glycoside extract of different samples present characteristic peaks at 1,615, 1,585, 1,450 cm(-1) (vibration of phenyl framework) and 1,658 cm(-1) (=C-O ) respectively, therefore, the authors speculated that their mutual component is the compound of phenolic glycoside. The two-dimensional infrared correlation spectra present five automatic peaks (vibration of phenyl framework) in 800-1,800 cm(-1) (1,366, 1,420, 1,508, 1,585, 1,669 cm(-1)). So the authors can conclude that a lot of information can be provided by macro-fingerprint technology of infrared spectroscopy which can evaluate overall quality of radix scutellariae accurately and be used to study the characteristics of relevance of crude and prepared scutellariae.
Two dimensional unstable scar statistics.
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.
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.
Hosako, Mutsumi; Muto, Taika; Nakamura, Yukiko; Tsuta, Koji; Tochigi, Naobumi; Tsuda, Hitoshi; Asamura, Hisao; Tomonaga, Takeshi; Kawai, Akira; Kondo, Tadashi
2012-01-04
To investigate the proteomic background of malignancies of the pleura, we examined and compared the proteomic profile of malignant pleural mesothelioma (MPM)(10 cases), lung adenocarcinoma (11 cases), squamous cell carcinoma of the lung (13 cases), pleomorphic carcinoma of the lung (3 cases) and synovial sarcoma (6 cases). Cellular proteins were extracted from specific populations of tumor cells recovered by laser microdissection. The extracted proteins were labeled with CyDye DIGE Fluor saturation dyes and subjected to two-dimensional difference gel electrophoresis (2D-DIGE) using a large format electrophoresis device. Among 3875 protein spots observed, the intensity of 332 was significantly different (Wilcoxon p value less than 0.05) and with more than two-fold inter-sample-group average difference between the different histology groups. Among these 332, 282 were annotated by LC-MS/MS and included known biomarker proteins for MPM, such as calretinin, as well as proteins previously uncharacterized in MPM. Tissue microarray immunohistochemistry revealed that the expression of cathepsin D was lower in MPM than in lung adenocarcinoma (15% vs. 44% of cases respectively in immunohistochemistry). In conclusion, we examined the protein expression profile of MPM and other lung malignancies, and identified cathepsin D to distinguish MPM from most popular lung cancer such as lung adenocarcinoma. Copyright © 2011 Elsevier B.V. All rights reserved.
Two Dimensional Lattice Boltzmann Method for Cavity Flow Simulation
Panjit MUSIK
2004-01-01
Full Text Available This paper presents a simulation of incompressible viscous flow within a two-dimensional square cavity. The objective is to develop a method originated from Lattice Gas (cellular Automata (LGA, which utilises discrete lattice as well as discrete time and can be parallelised easily. Lattice Boltzmann Method (LBM, known as discrete Lattice kinetics which provide an alternative for solving the Navier–Stokes equations and are generally used for fluid simulation, is chosen for the study. A specific two-dimensional nine-velocity square Lattice model (D2Q9 Model is used in the simulation with the velocity at the top of the cavity kept fixed. LBM is an efficient method for reproducing the dynamics of cavity flow and the results which are comparable to those of previous work.
Two-dimensional liquid chromatography
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...
The convolution theorem for two-dimensional continuous wavelet transform
ZHANG CHI
2013-01-01
In this paper , application of two -dimensional continuous wavelet transform to image processes is studied. We first show that the convolution and correlation of two continuous wavelets satisfy the required admissibility and regularity conditions ,and then we derive the convolution and correlation theorem for two-dimensional continuous wavelet transform. Finally, we present numerical example showing the usefulness of applying the convolution theorem for two -dimensional continuous wavelet transform to perform image restoration in the presence of additive noise.
Two-dimensional capillary origami
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.
Studies on Inverse Opal and Two-Dimensional Nonlinear Photonic Crystals%反Opal及二维非线性光子晶体的研究
倪培根; 程丙英; 张道中
2006-01-01
通过向SiO2 Opal模板中填充钛酸乙酯制备TiO2光子晶体,观测到光子晶体带隙位置的移动达62nm,并发现光子晶体的有序度随填充率的升高而下降.向聚苯乙烯Opal模板中填充钛酸乙酯,制备成当时填充率最高、带隙最短的紫外波段TiO2反Opal光子晶体(中心波长～380nm),并根据测量的其透射谱估算出其填充率约为12%,即Opal模板孔隙的50%被填充.本文还对二维PPLN光子晶体进行了研究.建立了一套高压极化装置和电压数据采集装置,通过外加电场极化法成功制备出了具有正方形和矩形两种晶格形状二维PPLN光子晶体.利用二维PPLN的二阶准相位匹配,测量了其对1.064μm激光的二次谐波转换效率,并研究了晶体的温度、激光的入射角度及占空比对二次谐波转换效率的影响.利用矩形晶格实现了多方向、多波长倍频高效输出.%In this paper, we report some results on inverse opal photonic crystal and two-dimensional periodically poled lithium niobate photonic crystal. First, the process of infiltrating TiO2 into SiO2 Opal was systematically studied. Because of the infiltration of TiO2, the gap of SiO2 Opal was shifted to longer wavelength and a maximum shift of 62nm was observed. Furthermore, an inverse TiO2 Opal with larger filling fraction, ～ 12%, was fabricated, whose band gap in the Γ-L direction is located in the ultraviolet region ( ～ 380nm). Then two-dimensional nonlinear photonic crystals of lithium nlobate with uniform square lattices were fabricated by applying external electric fields. The variations of second-harmonic output with crystal temperatures, incident angles and reversed duty cycles were measured. Red, yellow,green, blue, and violet coherent radiations were generated in the nonlinear photonic crystal with rectangular lattice in the collinearly and non-collinearly quasi-phase matching geometries. The results showed that two-dimensional nonlinear photonic crystal
Two-Dimensional Scheduling: A Review
Zhuolei Xiao
2013-07-01
Full Text Available In this study, we present a literature review, classification schemes and analysis of methodology for scheduling problems on Batch Processing machine (BP with both processing time and job size constraints which is also regarded as Two-Dimensional (TD scheduling. Special attention is given to scheduling problems with non-identical job sizes and processing times, with details of the basic algorithms and other significant results.
Wu, Bin; Li, Huiying; Du, Xiaoming; Zhong, Lirong; Yang, Bin; Du, Ping; Gu, Qingbao; Li, Fasheng
2016-02-01
During the process of surfactant enhanced aquifer remediation (SEAR), free phase dense non-aqueous phase liquid (DNAPL) may be mobilized and spread. The understanding of the impact of DNAPL spreading on the SEAR remediation is not sufficient with its positive effect infrequently mentioned. To evaluate the correlation between DNAPL spreading and remediation efficiency, a two-dimensional sandbox apparatus was used to simulate the migration and dissolution process of 1,2-DCA (1,2-dichloroethane) DNAPL in SEAR. Distribution area of DNAPL in the sandbox was determined by digital image analysis and correlated with effluent DNAPL concentration. The results showed that the effluent DNAPL concentration has significant positive linear correlation with the DNAPL distribution area, indicating the mobilization of DNAPL could improve remediation efficiency by enlarging total NAPL-water interfacial area for mass transfer. Meanwhile, the vertical migration of 1,2-DCA was limited within the boundary of aquifer in all experiments, implying that by manipulating injection parameters in SEAR, optimal remediation efficiency can be reached while the risk of DNAPL vertical migration is minimized. This study provides a convenient visible and quantitative method for the optimization of parameters for SEAR project, and an approach of rapid predicting the extent of DNAPL contaminant distribution based on the dissolved DNAPL concentration in the extraction well.
Levshov, Dmitry I.; Avramenko, Marina V.; Than, Xuan-Tinh; Michel, Thierry; Arenal, Raul; Paillet, Matthieu; Rybkovskiy, Dmitry V.; Osadchy, Alexander V.; Rochal, Sergei B.; Yuzyuk, Yuri I.; Sauvajol, Jean-Louis
2016-01-01
Radial breathing modes (RBMs) are widely used for the atomic structure characterization and index assignment of single-walled carbon nanotubes (SWNTs) from resonant Raman spectroscopy. However, for double-walled carbon nanotubes (DWNTs), the use of conventional ωRBM(d) formulas is complicated due to the van der Waals interaction between the layers, which strongly affects the frequencies of radial modes and leads to new collective vibrations. This paper presents an alternative way to theoretically study the collective radial breathing-like modes (RBLMs) of DWNTs and to account for interlayer interaction, namely the continuous two-dimensional membrane theory. We obtain an analytical ωRBLM(do,di) relation, being the equivalent of the conventional ωRBM(d) expressions, established for SWNTs. We compare our theoretical predictions with Raman data, measured on individual index-identified suspended DWNTs, and find a good agreement between experiment and theory. Moreover, we show that the interlayer coupling in individual DWNTs strongly depends on the interlayer distance, which is manifested in the frequency shifts of the RBLMs with respect to the RBMs of the individual inner and outer tubes. In terms of characterization, this means that the combination of Raman spectroscopy data and predictions of continuous membrane theory may give additional criteria for the index identification of DWNTs, namely the interlayer distance.
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.
Zhu, S; Yang, Y; Khambay, B
2017-03-01
Clinicians are accustomed to viewing conventional two-dimensional (2D) photographs and assume that viewing three-dimensional (3D) images is similar. Facial images captured in 3D are not viewed in true 3D; this may alter clinical judgement. The aim of this study was to evaluate the reliability of using conventional photographs, 3D images, and stereoscopic projected 3D images to rate the severity of the deformity in pre-surgical class III patients. Forty adult patients were recruited. Eight raters assessed facial height, symmetry, and profile using the three different viewing media and a 100-mm visual analogue scale (VAS), and appraised the most informative viewing medium. Inter-rater consistency was above good for all three media. Intra-rater reliability was not significantly different for rating facial height using 2D (P=0.704), symmetry using 3D (P=0.056), and profile using projected 3D (P=0.749). Using projected 3D for rating profile and symmetry resulted in significantly lower median VAS scores than either 3D or 2D images (all Pstereoscopic 3D projection was the preferred method for rating. The reliability of assessing specific characteristics was dependent on the viewing medium. Clinicians should be aware that the visual information provided when viewing 3D images is not the same as when viewing 2D photographs, especially for facial depth, and this may change the clinical impression.
Kumari, Babita; Adlakha, Neeru
2015-02-01
Thermoregulation is a complex mechanism regulating heat production within the body (chemical thermoregulation) and heat exchange between the body and the environment (physical thermoregulation) in such a way that the heat exchange is balanced and deep body temperatures are relatively stable. The external heat transfer mechanisms are radiation, conduction, convection and evaporation. The physical activity causes thermal stress and poses challenges for this thermoregulation. In this paper, a model has been developed to study temperature distribution in SST regions of human limbs immediately after physical exercise under cold climate. It is assumed that the subject is doing exercise initially and comes to rest at time t = 0. The human limb is assumed to be of cylindrical shape. The peripheral region of limb is divided into three natural components namely epidermis, dermis and subdermal tissues (SST). Appropriate boundary conditions have been framed based on the physical conditions of the problem. Finite difference has been employed for time, radial and angular variables. The numerical results have been used to obtain temperature profiles in the SST region immediately after continuous exercise for a two-dimensional unsteady state case. The results have been used to analyze the thermal stress in relation to light, moderate and vigorous intensity exercise.
Pavlidis, Mitrofanis
2016-01-01
Purpose. To evaluate comparative aspiration flow performance and also vitrectomy operating time efficiency using a double-cutting open port vitreous cutting system incorporated in a two-dimensional cutting (TDC, DORC International) vitrectome design versus standard vitreous cutter. Methods. In vitro investigations compared aspiration flow rates in artificial vitreous humor at varying cutter speeds and vacuum levels using a TDC vitrectome and a standard vitrectome across different aspiration pump systems. A prospective single-centre clinical study evaluated duration of core vitrectomy in 80 patients with macular pucker undergoing 25-gauge or 27-gauge vitrectomy using either a TDC vitrectome at 16,000 cuts per minute (cpm) or standard single-cut vitrectome, combined with a Valve Timing intelligence (VTi) pump system (EVA, DORC International). Results. Aspiration flow rates remained constant independent of TDC vitrectome cut rate, while flow rates decreased linearly at higher cutter speeds using a classic single-blade vitrectome. Mean duration of core vitrectomy surgeries using a TDC vitreous cutter system was significantly (p < 0.001) shorter than the mean duration of core vitrectomy procedures using a single-cut vitrectome of the same diameter (reduction range, 34%-50%). Conclusion. Vitrectomy surgery performed using a TDC vitrectome was faster than core vitrectomy utilizing a standard single-action vitrectome at similar cut speeds.
Mitrofanis Pavlidis
2016-01-01
Full Text Available Purpose. To evaluate comparative aspiration flow performance and also vitrectomy operating time efficiency using a double-cutting open port vitreous cutting system incorporated in a two-dimensional cutting (TDC, DORC International vitrectome design versus standard vitreous cutter. Methods. In vitro investigations compared aspiration flow rates in artificial vitreous humor at varying cutter speeds and vacuum levels using a TDC vitrectome and a standard vitrectome across different aspiration pump systems. A prospective single-centre clinical study evaluated duration of core vitrectomy in 80 patients with macular pucker undergoing 25-gauge or 27-gauge vitrectomy using either a TDC vitrectome at 16,000 cuts per minute (cpm or standard single-cut vitrectome, combined with a Valve Timing intelligence (VTi pump system (EVA, DORC International. Results. Aspiration flow rates remained constant independent of TDC vitrectome cut rate, while flow rates decreased linearly at higher cutter speeds using a classic single-blade vitrectome. Mean duration of core vitrectomy surgeries using a TDC vitreous cutter system was significantly (p<0.001 shorter than the mean duration of core vitrectomy procedures using a single-cut vitrectome of the same diameter (reduction range, 34%–50%. Conclusion. Vitrectomy surgery performed using a TDC vitrectome was faster than core vitrectomy utilizing a standard single-action vitrectome at similar cut speeds.
Gao, Haigen; Yue, Zhenxing; Li, Longtu
2016-03-01
A first-principles method is employed to study the mechanism of screening depolarizing field in two-dimensional BaTiO3 nanosheets. The geometric structures and ferroelectric properties show that the low-dimensional BaTiO3 with thickness m = 3 is a freestanding ultrathin film. Therefore, the scale of BaTiO3 nanosheets is defined as m = 1 and 2. The stable domain period corresponding to m = 1, 2, and 3 is 2, 2, and 6, respectively. When m = 1 and 2, only the spontaneous polarizations perpendicular to the surfaces are observed, and they are ˜6 and 15 μC/cm2, respectively. This indicates that the depolarizing field still has an effect on spontaneous polarizations. The difference in macroscopic charge density distribution between ferroelectric and paraelectric phases reveals that a dipole is formed at the ferroelectric domain wall, which leads to a decrease in the depolarizing field in the direction [001]. As a consequence, the critical thickness disappears.
Li, Xiaoming; Shen, Qirong; Zhang, Dongqing; Mei, Xinlan; Ran, Wei; Xu, Yangchun; Yu, Guanghui
2013-01-01
While the properties of biochar are closely related to its functional groups, it is unclear under what conditions biochar develops its properties. In this study, two-dimensional (2D) (13)C nuclear magnetic resonance (NMR) correlation spectroscopy was for the first time applied to investigate the development of functional groups and establish their relationship with biochar properties. The results showed that the agricultural biomass carbonized to biochars was a dehydroxylation/dehydrogenation and aromatization process, mainly involving the cleavage of O-alkylated carbons and anomeric O-C-O carbons in addition to the production of fused-ring aromatic structures and aromatic C-O groups. With increasing charring temperature, the mass cleavage of O-alkylated groups and anomeric O-C-O carbons occurred prior to the production of fused-ring aromatic structures. The regression analysis between functional groups and biochar properties (pH and electrical conductivity) further demonstrated that the pH and electrical conductivity of rice straw derived biochars were mainly determined by fused-ring aromatic structures and anomeric O-C-O carbons, but the pH of rice bran derived biochars was determined by both fused-ring aromatic structures and aliphatic O-alkylated (HCOH) carbons. In summary, this work suggests a novel tool for characterising the development of functional groups in biochars.
Xiaoming Li
Full Text Available While the properties of biochar are closely related to its functional groups, it is unclear under what conditions biochar develops its properties. In this study, two-dimensional (2D (13C nuclear magnetic resonance (NMR correlation spectroscopy was for the first time applied to investigate the development of functional groups and establish their relationship with biochar properties. The results showed that the agricultural biomass carbonized to biochars was a dehydroxylation/dehydrogenation and aromatization process, mainly involving the cleavage of O-alkylated carbons and anomeric O-C-O carbons in addition to the production of fused-ring aromatic structures and aromatic C-O groups. With increasing charring temperature, the mass cleavage of O-alkylated groups and anomeric O-C-O carbons occurred prior to the production of fused-ring aromatic structures. The regression analysis between functional groups and biochar properties (pH and electrical conductivity further demonstrated that the pH and electrical conductivity of rice straw derived biochars were mainly determined by fused-ring aromatic structures and anomeric O-C-O carbons, but the pH of rice bran derived biochars was determined by both fused-ring aromatic structures and aliphatic O-alkylated (HCOH carbons. In summary, this work suggests a novel tool for characterising the development of functional groups in biochars.
Chen, Yi-Hui; Tian, Hui-Lin; Li, Ji-Heng; Li, Guo-Ying
2012-06-01
The Fourier transform infrared spectroscopy and two dimensional correlation analysis method were applied to study a denaturing process of uncross-linked collagen and cross-linked collagen during varying temperature. It was found that the intensity of typically characteristic absorptions of collagen decreased and its peak shifted to low frequency, The amide II central absorbance peak moved to a lower frequency by about 10 cm(-1), which indicated that the inter-chain hydrogen bonds which stabilized the triple helix conformation of collagen were disrupted during thermal denaturation, resulting in a conformational change. The intensity of auto-peak at 1 515 cm(-1) was maximum, which suggested that the temperature had a big impact on amide II. In comparison with uncross-linked collagen, the intensity of cross-peaks of cross-linked collagen was weaker, which demonstrated that the effect of temperature on the structure of cross-linked collagen was smaller, and the thermal stability properties of collagen solution could be improved by cross-linking. While the order of second structure changes of cross-linked collagen was different. These fundamental data should provide available information for understanding the relationship between the structure and function of cross-linked collagen.
Rao, C N R; Gopalakrishnan, K; Maitra, Urmimala
2015-04-22
Novel properties of graphene have been well documented, whereas the importance of nanosheets of MoS2 and other chalcogenides is increasingly being recognized over the last two to three years. Borocarbonitrides, BxCyNz, with insulating BN and conducting graphene on either side are new materials whose properties have been attracting attention. These two-dimensional (2D) materials contain certain common features. Thus, graphene, MoS2, and borocarbonitrides have all been used in supercapacitor applications, oxygen reduction reactions (ORRs), and lithium-ion batteries. It is instructive, therefore, to make a comparative study of some of the important properties of these layered materials. In this article, we discuss properties related to energy devices at length. We examine the hydrogen evolution reaction facilitated by graphene, MoS2, and related materials. We also discuss gas and radiation sensors based on graphene and MoS2 as well as gas storage properties of graphene and borocarbonitrides. The article should be useful in making a judicious choice of which 2D material to use for a particular application.
Laban, Mohamed; Alanwar, Ahmed A; Etman, Mohamed K; Elsokkary, Mohammed S; Elkotb, Ahmed M; Hasanien, Ahmad S; KhalafAllah, Ali E; Noah, Nancy M
2017-07-27
This study aimed to evaluate accuracy of five-dimensional long bones (5D LB) compared to two-dimensional ultrasound (2DUS) biometry to predict fetal weight among normal term women. Fifty six normal term women were recruited at Ain Shams Maternity Hospital, Egypt from 14 May to 30 November 2015. Fetal weight was estimated by Hadlock's IV formula using 2DUS and 5D LB. Estimated fetal weights (EFW) by 2DUS and 5D LB were compared with actual birth weights (ABW). Mean femur length (FL) was 7.07 ± 0.73 cm and 6.74 ± 0.67 cm by 2DUS and 5D LB (p = .02). EFW was 3309.86 ± 463.06 g by 2DUS and 3205.46 ± 447.85 g by 5D LB (p = .25). No statistical difference was observed between ABW and EFW by 2DUS (p = .7) or 5D LB (p = .45). Positive correlation was found between EFW by 2DUS, 5D LB, and ABW (r = 0.67 and 0.7; p ABW (p = .15). 2DUS and 5D LB had same accuracy for fetal weight estimation at normal term pregnancy.
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.
First-Principles Study of Novel Two-Dimensional (C4H9NH3)2PbX4 Perovskites for Solar Cell Absorbers.
Wang, Da; Wen, Bo; Zhu, Ya-Nan; Tong, Chuan-Jia; Tang, Zhen-Kun; Liu, Li-Min
2017-02-16
Low-dimensional perovskites (A2BX4), in which the A cations are replaced by different organic cations, may be used for photovoltaic applications. In this contribution, we systematically study the two-dimensional (2D) (C4H9NH3)2PbX4 (X═Cl, Br and I) hybrid perovskites by density functional theory (DFT). A clear structures-properties relationship, with the photophysical characteristics directly related to the dimensionality and material compositions, was established. The strong s-p antibonding couplings in both bulk and monolayer (C4H9NH3)2PbI4 lead to low effective masses for both holes (mh*) and electrons (me*). However, mh* increases in proportion to the decreasing inorganic layer thickness, which eventually leads to a slightly shifted band edge emission found in 2D perovskites. Notably, the 2D (C4H9NH3)2PbX4 perovskites exhibit strong optical transitions in the visible light spectrum, and the optical absorption tunings can be achieved by varying the compositions and the layer thicknesses. Such work paves an important way to uncover the structures-properties relationship in 2D perovskites.
Afonso, Luis; Briasoulis, Alex; Mahajan, Nitin; Kondur, Ashok; Siddiqui, Fayez; Siddiqui, Sabeeh; Alesh, Issa; Cardozo, Shaun; Kottam, Anupama
2015-12-01
Hypertrophic cardiomyopathy (HCM) affects the right ventricle (RV) because of the anatomically hypertrophied septum and plausibly by extension of the myopathic process to the RV. We sought to investigate RV strain in patients with left ventricular hypertrophy secondary to either HCM or hypertension (H-LVH). Our cross-sectional study included 32 patients with HCM, 21 patients with H-LVH, and 11 healthy subjects, who were evaluated with transthoracic echocardiography. Using a dedicated software package, bi-dimensional acquisitions were analyzed to measure segmental longitudinal strain in apical views. Right ventricular global longitudinal strain (GLS) was calculated by averaging septal and right free wall strains. The HCM and H-LVH groups were comparable for age and demographic characteristics. Right ventricular tricuspid annular plane systolic excursion was not significantly different between HCM and H-LVH subjects. Moreover, RV GLS, septal and lateral RV myocardial strain were significantly impaired in patients with HCM (all p 14.9% differentiated HCM and H-LVH with a 90% sensitivity and a 95% specificity (p < 0.001). RV strain parameters are impaired in patients with HCM. Assessment of two-dimensional RV strain parameters could help differentiate between HCM and H-LVH.
Kacem, N S; Mauro, S; Muhovski, Y; Delporte, F; Renaut, J; Djekoun, A; Watillon, B
2016-09-01
Acclimatization to stress is associated with profound changes in proteome composition. The use of plant cell and tissue culture offers a means to investigate the physiological and biochemical processes involved in the adaptation to osmotic stress. We employed a new proteomic approach to further understand the response of calli to dehydration induced by polyethylene glycol (PEG6000). Calli of three durum wheat genotypes Djenah Khetifa, Oued Zenati and Waha were treated with two concentrations of polyethylene glycol to mimic osmotic stress. Changes in protein relative abundance were analyzed using a new electrophoretic approach named diagonal two-dimensional electrophoresis (D-2DE), combined with mass spectrometry. Total proteins were extracted from 30-day-old calli from three durum wheat genotypes that showed contrasting levels of drought stress tolerance in the field. The combination of one-dimensional electrophoresis and D-2DE gave a specific imprint of the protein extracts under osmotic stress, as well as characterizing and identifying individual target proteins. Of the variously expressed proteins, three were selected (globulin, GAPDH and peroxidase) and further analyzed using qRT-PCR at the transcriptome level in order to compare the results with the proteomic data. Western blot analysis was used to further validate the differences in relative abundance pattern. The proteins identified through this technique provide new insights as to how calli respond to osmotic stress. Our method of study provides an original and relevant approach of analyzing the osmotic-responsive mechanisms at the cellular level of durum wheat with agronomic perspectives.
Wu, Bin; Li, Huiying; Du, Xiaoming; Zhong, Lirong; Yang, Bin; Du, Ping; Gu, Qingbao; Li, Fasheng
2016-02-01
During the process of surfactant enhanced aquifer remediation (SEAR), free phase dense non-aqueous phase liquid (DNAPL) may be mobilized and spread. The understanding of the impact of DNAPL spreading on the SEAR remediation is not sufficient with its positive effect infrequently mentioned. To evaluate the correlation between DNAPL spreading and remediation efficiency, a two-dimensional sandbox apparatus was used to simulate the migration and dissolution process of 1,2-DCA (1,2-dichloroethane) DNAPL in SEAR. Distribution area of DNAPL in the sandbox was determined by digital image analysis and correlated with effluent DNAPL concentration. The results showed that the effluent DNAPL concentration has significant positive linear correlation with the DNAPL distribution area, indicating the mobilization of DNAPL could improve remediation efficiency by enlarging total NAPL-water interfacial area for mass transfer. Meanwhile, the vertical migration of 1,2-DCA was limited within the boundary of aquifer in all experiments, implying that by manipulating injection parameters in SEAR, optimal remediation efficiency can be reached while the risk of DNAPL vertical migration is minimized. This study provides a convenient visible and quantitative method for the optimization of parameters for SEAR project, and an approach of rapid predicting the extent of DNAPL contaminant distribution based on the dissolved DNAPL concentration in the extraction well.
Strongly correlated two-dimensional plasma explored from entropy measurements.
Kuntsevich, A Y; Tupikov, Y V; Pudalov, V M; Burmistrov, I S
2015-06-23
Charged plasma and Fermi liquid are two distinct states of electronic matter intrinsic to dilute two-dimensional electron systems at elevated and low temperatures, respectively. Probing their thermodynamics represents challenge because of lack of an adequate technique. Here, we report a thermodynamic method to measure the entropy per electron in gated structures. Our technique appears to be three orders of magnitude superior in sensitivity to a.c. calorimetry, allowing entropy measurements with only 10(8) electrons. This enables us to investigate the correlated plasma regime, previously inaccessible experimentally in two-dimensional electron systems in semiconductors. In experiments with clean two-dimensional electron system in silicon-based structures, we traced entropy evolution from the plasma to Fermi liquid regime by varying electron density. We reveal that the correlated plasma regime can be mapped onto the ordinary non-degenerate Fermi gas with an interaction-enhanced temperature-dependent effective mass. Our method opens up new horizons in studies of low-dimensional electron systems.
Two-dimensional ranking of Wikipedia articles
Zhirov, A. O.; Zhirov, O. V.; Shepelyansky, D. L.
2010-10-01
The Library of Babel, described by Jorge Luis Borges, stores an enormous amount of information. The Library exists ab aeterno. Wikipedia, a free online encyclopaedia, becomes a modern analogue of such a Library. Information retrieval and ranking of Wikipedia articles become the challenge of modern society. While PageRank highlights very well known nodes with many ingoing links, CheiRank highlights very communicative nodes with many outgoing links. In this way the ranking becomes two-dimensional. Using CheiRank and PageRank we analyze the properties of two-dimensional ranking of all Wikipedia English articles and show that it gives their reliable classification with rich and nontrivial features. Detailed studies are done for countries, universities, personalities, physicists, chess players, Dow-Jones companies and other categories.
Towards two-dimensional search engines
Ermann, Leonardo; Shepelyansky, Dima L
2011-01-01
We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way the ranking of nodes becomes two-dimensional that paves the way for development of two-dimensional search engines of new type. Information flow properties on PageRank-CheiRank plane are analyzed for networks of British, French and Italian Universities, Wikipedia, Linux Kernel, gene regulation and other networks. Methods of spam links control are also analyzed.
Toward two-dimensional search engines
Ermann, L.; Chepelianskii, A. D.; Shepelyansky, D. L.
2012-07-01
We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way, the ranking of nodes becomes two dimensional which paves the way for the development of two-dimensional search engines of a new type. Statistical properties of information flow on the PageRank-CheiRank plane are analyzed for networks of British, French and Italian universities, Wikipedia, Linux Kernel, gene regulation and other networks. A special emphasis is done for British universities networks using the large database publicly available in the UK. Methods of spam links control are also analyzed.
Peng-Fei Hou
2014-11-01
Full Text Available Two-dimensional Green's functions for a line heat source applied in the fluid and pyroelectric two-phase plane are presented in this paper. By virtue of the two-dimensional general solutions which are expressed in harmonic functions, six newly introduced harmonic functions with undetermined constants are constructed. Then, all the pyroelectric components in the fluid and pyroelectric two-phase plane can be derived by substituting these harmonic functions into the corresponding general solutions. And the undetermined constants can be obtained by the interface compatibility conditions and the mechanical, electric, and thermal equilibrium conditions. Numerical results are given graphically by contours.
Two-dimensional quantum repeaters
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.
Two-dimensional capillary origami
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.
Two-dimensional cubic convolution.
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.
Topological aspect of disclinations in two-dimensional crystals
Qi Wei-Kai; Zhu Tao; Chen Yong; Ren Ji-Rong
2009-01-01
By using topological current theory, this paper studies the inner topological structure of disclinations during the melting of two-dimensional systems. From two-dimensional elasticity theory, it finds that there are topological currents for topological defects in homogeneous equation. The evolution of disclinations is studied, and the branch conditions for generating, annihilating, crossing, splitting and merging of disclinations are given.
Kalyanapu, A. J.; Dullo, T. T.; Thornton, J. C.; Auld, L. A.
2015-12-01
Obion River, is located in the northwestern Tennessee region, and discharges into the Mississippi River. In the past, the river system was largely channelized for agricultural purposes that resulted in increased erosion, loss of wildlife habitat and downstream flood risks. These impacts are now being slowly reversed mainly due to wetland restoration. The river system is characterized by a large network of "loops" around the main channels that hold water either from excess flows or due to flow diversions. Without data on each individual channel, levee, canal, or pond it is not known where the water flows from or to. In some segments along the river, the natural channel has been altered and rerouted by the farmers for their irrigation purposes. Satellite imagery can aid in identifying these features, but its spatial coverage is temporally sparse. All the alterations that have been done to the watershed make it difficult to develop hydraulic models, which could predict flooding and droughts. This is especially true when building one-dimensional (1D) hydraulic models compared to two-dimensional (2D) models, as the former cannot adequately simulate lateral flows in the floodplain and in complex terrains. The objective of this study therefore is to study the performance of 1D and 2D flood models in this complex river system, evaluate the limitations of 1D models and highlight the advantages of 2D models. The study presents the application of HEC-RAS and HEC-2D models developed by the Hydrologic Engineering Center (HEC), a division of the US Army Corps of Engineers. The broader impacts of this study is the development of best practices for developing flood models in channelized river systems and in agricultural watersheds.
Okuda, Masaki; Ohta, Kaoru; Tominaga, Keisuke
2016-09-01
Dynamics of the hydration structure around small vibrational probes have been extensively studied over the past few decades. However, we need to gain insight into how vibrational dynamics is affected by the molecular nature of the probe molecules in water. In this study, 2-nitro-5-thiocyanate benzoic acid (NTBA), which has an SCN group attached to an aromatic ring, and thiocyanate ion (SCN-) were used to investigate the vibrational dynamics of two vibrational probes, including vibrational frequency fluctuations and rotational relaxation. By performing two-dimensional infrared spectroscopic measurements, the vibrational frequency fluctuations of the SCN anti-stretching modes of these solutes were compared. The frequency-frequency time correlation function (FFTCF) of these solutes can be modeled by a delta function plus an exponential function and a constant. The FFTCF of NTBA was characterized by a time constant of 1.1 ps, which is similar to that of SCN-. Moreover, no component was longer than this constant. Consequently, the loss of the correlation in frequency fluctuations of the SCN anti-stretching mode of NTBA may be controlled by a mechanism similar to that of the ionic probe, which involves the hydrogen bonding dynamics of water. Polarization-controlled IR pump-probe measurements were performed for these vibrational probes in water to study the vibrational energy relaxation (VER) and reorientational relaxation processes. The VER rate of NTBA is much smaller than that of SCN-, which indicates that the intramolecular relaxation process is significant for VER of NTBA. Based on the rotational relaxation time of NTBA being shorter than that of SCN-, the internal rotational motion of the SCN group around the Cphenyl-S bond axis, where Cphenyl denotes a carbon atom of the aromatic ring to which the SCN group is attached, may play an important role in the anisotropic decay of NTBA in H2O.
Field analysis of two-dimensional integrated optical gratings
Borsboom, P.-P.; Frankena, H. J.
1995-05-01
A rigorous technique to determine the field scattered by a two-dimensional rectangular grating made up of many corrugations was developed. In this method, the grating was deemed as a sequence of two types of waveguide sections, alternatingly connected by step discontinuities. A matrix was derived that described the entire rectangular grating by integrating the separate steps and waveguide sections. With the proposed technique, several configuration were analyzed. The obtained results showed good consistency with the consequences of previous studies. Furthermore, to examine the numerical stability of the proposed method, the length of the grating was increased and obtained results for a grating with 100 periods.
Wee, Tae-Kwon; Kuo, Ying-Hwa; Lee, Dong-Kyou
2010-12-01
A two-dimensional curved ray tracer (CRT) is developed to study the propagation path of radio signals across a heterogeneous planetary atmosphere. The method, designed to achieve improvements in both computational efficiency and accuracy over conventional straight-line methods, takes rays' first-order bending into account to better describe curved raypaths in the stratified atmosphere. CRT is then used to simulate the phase path from GPS radio occultation (RO). The merit of the ray tracing approach in GPS RO is explicit consideration of horizontal variation in the atmosphere, which may lead to a sizable error but is disregarded in traditional retrieval schemes. In addition, direct modeling of the phase path takes advantage of simple error characteristics in the measurement. With provision of ionospheric and neutral atmospheric refractive indices, in this effort, rays are traced along the full range of GPS-low Earth orbiting (LEO) radio links just as the measurements are made in real life. Here, ray shooting is employed to realize the observed radio links with controlled accuracy. CRT largely reproduces the very measured characteristics of GPS signals. When compared, the measured and simulated phases show remarkable agreement. The cross validation between CRT and GPS RO has confirmed not only the strength of CRT but also the high accuracy of GPS RO measurements. The primary motivation for this study is enabling effective quality control for GPS RO data, overcoming a complicated error structure in the high-level data. CRT has also shown a great deal of potential for improved utilization of GPS RO data for geophysical research.
García-Peñarrubia, Pilar; Gálvez, Juan J; Gálvez, Jesús
2014-09-01
Cell signalling processes involve receptor trafficking through highly connected networks of interacting components. The binding of surface receptors to their specific ligands is a key factor for the control and triggering of signalling pathways. But the binding process still presents many enigmas and, by analogy with surface catalytic reactions, two different mechanisms can be conceived: the first mechanism is related to the Eley-Rideal (ER) mechanism, i.e. the bulk-dissolved ligand interacts directly by pure three-dimensional (3D) diffusion with the specific surface receptor; the second mechanism is similar to the Langmuir-Hinshelwood (LH) process, i.e. 3D diffusion of the ligand to the cell surface followed by reversible ligand adsorption and subsequent two-dimensional (2D) surface diffusion to the receptor. A situation where both mechanisms simultaneously contribute to the signalling process could also occur. The aim of this paper is to perform a computational study of the behavior of the signalling response when these different mechanisms for ligand-receptor interactions are integrated into a model for signal transduction and ligand transport. To this end, partial differential equations have been used to develop spatio-temporal models that show trafficking dynamics of ligands, cell surface components, and intracellular signalling molecules through the different domains of the system. The mathematical modeling developed for these mechanisms has been applied to the study of two situations frequently found in cell systems: (a) dependence of the signal response on cell density; and (b) enhancement of the signalling response in a synaptic environment.
Korkiakoski, A.; Niinimaeki, J.; Karppinen, J.; Korpelainen, R.; Haapea, M.; Natri, A.; Tervonen, O. (Inst. of Clinical Sciences, Dept. of Physical and Rehabilitation Medicine, Univ. of Oulu, Oulu (Finland))
2009-01-15
Background: Recent studies indicate that diminished blood flow may cause low back symptoms and intervertebral disc degeneration. Purpose: To explore the association between lumbar arterial stenosis as detected by two-dimensional time-of-flight magnetic resonance angiography (2D TOF-MRA) and lumbar pain symptoms in an occupational cohort of middle-aged Finnish males. Material and Methods: 228 male subjects aged 36 to 55 years (mean 47 years) were imaged with 2D TOF-MRA. Additionally, 20 randomly selected subjects were scanned with contrast-enhanced MRA (ceMRA). In each subject, the first (L1) to fourth (L4) segmental lumbar arteries were evaluated for lumbar artery stenosis using a dichotomic scale. One subject was excluded because of poor image quality, reducing the study population to 227 subjects. Logistic regression analysis was used to evaluate the association between arterial stenosis in 2D TOF-MRA and low back pain and sciatica symptoms (intensity, duration, frequency). Results: Comparing 2D TOF-MRA and ceMRA images, the kappa value (95% confidence interval) was 0.52 (0.31-0.73). The intraobserver reliability kappa value for 2D TOF-MRA was 0.85 (0.77-0.92), and interobserver kappa was 0.57 (0.49-0.65). The sensitivity of 2D TOF-MRA in detecting stenosis was 0.58, the accuracy 0.89, and the specificity 0.94. In 97 (43%) subjects all arteries were normal, whereas 130 (57%) had at least one stenosed artery. The left L4 artery was most often affected. The degree of arterial stenosis was associated with intensity of low back and sciatic pain, and sciatica pain duration during the past 3 months. Conclusion: 2D TOF-MRA is an acceptable imaging method for arterial stenosis compared to ceMRA. Arterial stenosis was associated with subjective pain symptoms, indicating a role of decreased nutrition in spinal disorders
Tou, S; Tou, W; Mah, D; Karatassas, A; Hewett, P
2013-05-01
The use of multimedia information provided preoperatively can potentially reduce anxiety in patients and improve the hospital experience. However, the use of two-dimensional (2D) animation (cartoon) to provide information to patients undergoing colorectal surgery has not been investigated. This study investigated the effect of preoperative 2D information on anxiety and knowledge retention in patients undergoing bowel surgery. Patients were randomized to one of two groups; the video group watched a 13-min cartoon animation whereas the nonvideo group did not. Anxiety levels were measured at the preadmission clinic, postvideo, on the day of admission for surgery, within 24-h after surgery and before discharge using the Spielberger state-trait anxiety inventory and visual analogue scale. Both groups completed a knowledge retention questionnaire and the video group completed a feedback questionnaire about the animation. Thirty-one patients (16 video, 15 nonvideo) participated in the study. There was no significant difference in baseline anxiety score between two groups. An immediate reduction (P = 0.03) in anxiety score was observed in the video group after watching the video compared with baseline. There was a significant reduction in anxiety score in the video group at discharge compared with the nonvideo group (P = 0.03). There was no significant difference in knowledge retention between two groups. Eighty-eight per cent of patients who watched the video found it beneficial. 2D animation is an effective medium for delivering information to patients undergoing bowel surgery and can potentially reduce anxiety related to surgery and improve the hospital experience. Colorectal Disease © 2013 The Association of Coloproctology of Great Britain and Ireland.
Li, Yuman; Xie, Mingxing; Wang, Xinfang; Lu, Qing; Zhang, Li; Ren, Pingping
2015-01-01
Early detection of right ventricular (RV) and left ventricular (LV) dysfunction in patients with repaired tetralogy of Fallot (TOF) is essential because dysfunction is correlated with a poor clinical outcome. The aim of this study was to assess RV and LV function in asymptomatic children with repaired TOF by two-dimensional ultrasound speckle tracking echocardiography (STE). Fifty-six asymptomatic children with a preserved biventricular ejection fraction (EF) after repair of TOF and 35 healthy control subjects were studied. RV and LV strain and strain rate were measured by STE. RVEF and pulmonary regurgitation (PR) were assessed using cardiac magnetic resonance imaging. Compared with the control subjects, RV regional longitudinal strain and strain rate and global longitudinal strain (GLS) and strain rate (GLSR) were impaired in children with repaired TOF. Likewise, LV circumferential and radial strain and strain rate were reduced in patients with TOF. In contrast, longitudinal strain and strain rate did not differ between the groups. RV and LV GLSR were correlated with postoperative follow-up period (r1 = -0.44; r2 = -0.48). RV GLS and GLSR were associated with RVEF (r1 = 0.64; r2 = 0.60) and PR (r1 = -0.48; r2 = -0.49). LV circumferential strain rate was related to PR (r = -0.45). STE can identify abnormalities that may represent early impairment of RV and LV systolic function in postoperative TOF patients with a preserved EF. PR is associated with decreased biventricular performance in repaired patients. STE-derived strain and strain rate may be useful indices for detecting the early deterioration of biventricular performance in patients with TOF. © 2014, Wiley Periodicals, Inc.
Spatiotemporal surface solitons in two-dimensional photonic lattices.
Mihalache, Dumitru; Mazilu, Dumitru; Lederer, Falk; Kivshar, Yuri S
2007-11-01
We analyze spatiotemporal light localization in truncated two-dimensional photonic lattices and demonstrate the existence of two-dimensional surface light bullets localized in the lattice corners or the edges. We study the families of the spatiotemporal surface solitons and their properties such as bistability and compare them with the modes located deep inside the photonic lattice.
E Taghizdehsiskht
2013-09-01
Full Text Available In recent years, semiconductor nanostructures have become the model systems of choice for investigation of electrical conduction on short length scales. Quantum transport is studied in a two dimensional electron gas because of the combination of a large Fermi wavelength and large mean free path. In the present work, a numerical method is implemented in order to contribute to the understanding of quantum transport in narrow channels in different conditions of disorder and magnetic fields. We have used an approach that has proved to be very useful in describing mesoscopic transport. We have assumed zero temperature and phase coherent transport. By using the trick that a conductor connected to infinite leads can be replaced by a finite conductor with the effect of the leads incorporated through a 'self-energy' function, a convenient method was provided for evaluating the Green's function of the whole device numerically. Then, Fisher-Lee relations was used for calculating the transmission coefficients through coherent mesoscopic conductors. Our calculations were done in a model system with Hard-wall boundary conditions in the transverse direction, and the Anderson model of disorder was used in disordered samples. We have presented the results of quantum transport for different strengths of disorder and introduced magnetic fields. Our results confirmed the Landauer formalism for calculation of electronic transport. We observed that weak localization effect can be removed by application of a weak perpendicular magnetic field. Finally, we numerically showed the transition to the integral quantum Hall effect regime through the suppression of backscattering on a disordered model system by calculating the two terminal conductance of a quasi-one-dimensional quantum conductor as a strong magnetic field is applied. Our results showed that this regime is entered when there is a negligible overlap between electron edge states localized at opposite sides of
Domański, J.; Badziak, J.; Jabloński, S.
2016-04-01
Laser-driven generation of high-energy ion beams has recently attracted considerable interest due to a variety of potential applications including proton radiography, ICF fast ignition, nuclear physics or hadron therapy. The ion beam parameters depend on both laser pulse and target parameters, and in order to produce the ion beam of properties required for a particular application the laser and target parameters must be carefully selected, and the mechanism of the ion beam generation should be well understood and controlled. Convenient and commonly used tools for studies of the ion acceleration process are particle-in-cell (PIC) codes. Using two-dimensional PIC simulations, the properties of a proton beam generated from a thin erbium hydride (ErH3) target irradiated by a 25fs laser pulse of linear or circular polarization and of intensity ranging from 1020 to 1021 W/cm2 are investigated and compared with the features of a proton beam produced from a hydrocarbon (CH) target. It has been found that using erbium hydride targets instead of hydrocarbon ones creates an opportunity to generate more compact proton beams of higher mean energy, intensity and of better collimation. This is especially true for the linear polarization of the laser beam, for which the mean proton energy, the amount of high energy protons and the intensity of the proton beam generated from the hydride target is by an order of magnitude higher than for the hydrocarbon target. For the circular polarization, the proton beam parameters are lower than those for the linear one, and the effect of target composition on the acceleration process is weaker.
Classifying Two-dimensional Hyporeductive Triple Algebras
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.
Application Mode Study of Mobile Two-dimensional Barcode%手机二维码应用模式研究
姜美莲; 周知宇; 郑晗
2012-01-01
手机二维码是把二维码技术与移动终端手机相结合的产物,以借助手机使用的便利性来充分发挥二维码识别技术的优越性.本文分析了手机二维码在我国的主要应用模式,分别为解码识读信息、解码链接上网、解码验证真伪,并探讨了其在应用中存在的问题,再针对这些问题提出了我国手机二维码业务的发展策略,为推动手机二维码的应用普及提供参考.摘要:手机二维码是把二维码技术与移动终端手机相结合的产物,以借助手机使用的便利性来充分发挥二维码识别技术的优越性.本文分析了手机二维码在我国的主要应用模式,分别为解码识读信息、解码链接上网、解码验证真伪,并探讨了其在应用中存在的问题,再针对这些问题提出了我国手机二维码业务的发展策略,为推动手机二维码的应用普及提供参考.%The mobile two-dimensional barcode is the integration of two-dimensional barcode technology and mobile terminal, this can make full use of the superiority of the two-dimensional barcode recognition technology with the help of mobile phone. This paper analyses the main application mode of mobile two-dimensional barcode in China.those are decoding to read information, decoding to link Internet and decoding to verify the authenticity,and then discusses the problems in its application, aims at these problems and puts forward the strategy of developing mobile two-dimensional barcode business , provides reference for promoting the application and popularization of mobile two-dimensional barcode.
Two-dimensional function photonic crystals
Wu, Xiang-Yao; Liu, Xiao-Jing; Liang, Yu
2016-01-01
In this paper, we have firstly proposed two-dimensional function photonic crystals, which the dielectric constants of medium columns are the functions of space coordinates $\\vec{r}$, it is different from the two-dimensional conventional photonic crystals constituting by the medium columns of dielectric constants are constants. We find the band gaps of two-dimensional function photonic crystals are different from the two-dimensional conventional photonic crystals, and when the functions form of dielectric constants are different, the band gaps structure should be changed, which can be designed into the appropriate band gaps structures by the two-dimensional function photonic crystals.
Lee, Hyun-Sook; Park, Jae-Hyun; Lee, Jae-Yeap [Department of Physics, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Kim, Ju-Young; Sung, Nak-Heon; Cho, B.K. [Department of Materials Science and Engineering, GIST, Gwangju 500-712 (Korea, Republic of); Lee, Hu-Jong, E-mail: hjlee@postech.ac.k [Department of Physics, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of)
2010-12-15
Temperature dependence of the in-plane conductance of a SmFeAsO{sub 0.85} single crystal is measured in c-axis and planar magnetic fields up to 7 T. The conductivity near the superconducting transition is well described by two-dimensional (2D) thermal-fluctuation theory. The 2D superconductivity arises as the c-axis coherence length is much shorter than the spacing between neighboring FeAs layers.
Invariant Subspaces of the Two-Dimensional Nonlinear Evolution Equations
Chunrong Zhu
2016-11-01
Full Text Available In this paper, we develop the symmetry-related methods to study invariant subspaces of the two-dimensional nonlinear differential operators. The conditional Lie–Bäcklund symmetry and Lie point symmetry methods are used to construct invariant subspaces of two-dimensional differential operators. We first apply the multiple conditional Lie–Bäcklund symmetries to derive invariant subspaces of the two-dimensional operators. As an application, the invariant subspaces for a class of two-dimensional nonlinear quadratic operators are provided. Furthermore, the invariant subspace method in one-dimensional space combined with the Lie symmetry reduction method and the change of variables is used to obtain invariant subspaces of the two-dimensional nonlinear operators.
Cugno, Graziano; Parreira, José R.; Ferlizza, Enea; Hernández-Castellano, Lorenzo E.; Carneiro, Mariana; Renaut, Jenny; Castro, Noemí; Arguello, Anastasio; Capote, Juan
2016-01-01
Seasonal weight loss (SWL) is the most important limitation to animal production in the Tropical and Mediterranean regions, conditioning producer’s incomes and the nutritional status of rural communities. It is of importance to produce strategies to oppose adverse effects of SWL. Breeds that have evolved in harsh climates have acquired tolerance to SWL through selection. Most of the factors determining such ability are related to changes in biochemical pathways as affected by SWL. In this study, a gel based proteomics strategy (BN: Blue-Native Page and 2DE: Two-dimensional gel electrophoresis) was used to characterize the mitochondrial proteome of the secretory tissue of the goat mammary gland. In addition, we have conducted an investigation of the effects of weight loss in two goat breeds with different levels of adaptation to nutritional stress: Majorera (tolerant) and Palmera (susceptible). The study used Majorera and Palmera dairy goats, divided in 4 sets, 2 for each breed: underfed group fed on wheat straw (restricted diet, so their body weight would be 15–20% reduced by the end of experiment), and a control group fed with an energy-balanced diet. At the end of the experimental period (22 days), mammary gland biopsies were obtained for all experimental groups. The proteomic analysis of the mitochondria enabled the resolution of a total of 277 proteins, and 148 (53%) were identified by MALDI-TOF/TOF mass spectrometry. Some of the proteins were identified as subunits of the glutamate dehydrogenase complex and the respiratory complexes I, II, IV, V from mitochondria, as well as numerous other proteins with functions in: metabolism, development, localization, cellular organization and biogenesis, biological regulation, response to stimulus, among others, that were mapped in both BN and 2DE gels. The comparative proteomics analysis enabled the identification of several proteins: NADH-ubiquinone oxidoreductase 75 kDa subunit and lamin B1 mitochondrial (up
Two-dimensional ranking of Wikipedia articles
Zhirov, A O; Shepelyansky, D L
2010-01-01
The Library of Babel, described by Jorge Luis Borges, stores an enormous amount of information. The Library exists {\\it ab aeterno}. Wikipedia, a free online encyclopaedia, becomes a modern analogue of such a Library. Information retrieval and ranking of Wikipedia articles become the challenge of modern society. We analyze the properties of two-dimensional ranking of all Wikipedia English articles and show that it gives their reliable classification with rich and nontrivial features. Detailed studies are done for countries, universities, personalities, physicists, chess players, Dow-Jones companies and other categories.
Mobility anisotropy of two-dimensional semiconductors
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.
Kellar, S.A. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley National Lab., CA (United States). Advanced Light Source Div.
1997-05-01
This thesis report the surface-structure determination of three, ultra-thin magnetic transition-metal films, Fe/Au(100), Mn/Ni(100), and Mn/Cu(100) using Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) and photoelectron holography. These structural studies are the first to use non-s initial states in the ARPEFS procedure. This thesis also reports an ARPEFS surface-structure determination of a two-dimensional transition-metal oxide, [(1 x 1)O/W(110)] x 12. The authors have analyzed the ARPFES signal from the Au 4f{sub 7/5} core level of the Au(1 ML)/Fe(15 ML)/Au(100) system. The analysis shows that the Fe grows layer by layer with one monolayer of gold, acting as a surfactant, remaining on top of the growing Fe layers. These surface gold atoms sit in the four-fold hollow site, 1.67 {+-} 0.02 A above the iron surface. The grown Fe layer is very much like the bulk, bcc iron, with an interlayer spacing of 1.43 {+-} 0.03 A. Analysis of the Mn 3p ARPEFS signals from c(2 x 2)Mn/Ni(100) and c(2 x 2)Mn/Cu(100) shows that the Mn forms highly corrugated surface alloys. The corrugation of the Mn/Ni(100) and Mn/Cu(100) systems are 0.24 {+-} 0.02 A and 0.30 {+-} 0.04 A respectively. In both cases the Mn is sticking above the plane of the surface substrate atoms. For the Mn/Ni(100) system the first layer Ni is contracted 4% from the bulk value. The Mn/Cu(100) system shows bulk spacing for the substrate Cu. Photoelectron holography shows that the Mn/Ni interface is very abrupt with very little Mn leaking into the second layer, while the Mn/Cu(100) case has a significant amount of Mn leaking into the second layer. A new, five-element electrostatic electron lens was developed for hemispherical electron-energy analyzers. This lens system can be operated at constant transverse or constants angular magnification, and has been optimized for use with the very small photon-spot sizes. Improvements to the hemispherical electron-energy analyzer are also discussed.
Adebayo RA
2013-07-01
Full Text Available Rasaaq Ayodele Adebayo,1 Patience Olayinka Akinwusi,2 Michael Olabode Balogun,1 Anthony Olubunmi Akintomide,1 Victor Oladeji Adeyeye,1 Olugbenga Olusola Abiodun,1 Luqman Adeleke Bisiriyu,3 Suraj Adefabi Ogunyemi,1 Ebenezer Adekunle Ajayi,4 Olufemi Eyitayo Ajayi,1 Adebayo Tolulope Oyedeji5 1Cardiology Unit, Department of Medicine, Obafemi Awolowo University Teaching Hospitals Complex, Ile-Ife, Osun State, 2Cardiology Unit, Department of Medicine, Osun State University, Osogbo, Osun State, 3Department of Demography and Social Statistics, Obafemi Awolowo University, Ile-Ife, Osun State, 4Cardiology Unit, Department of Medicine, Ekiti State University Teaching Hospital, Ado-Ekiti, Ekiti State, 5Cardiology Unit, Department of Medicine, LAUTECH Teaching Hospital, Osogbo, Osun State, Nigeria Background: Echocardiography remains a key noninvasive cardiac investigative tool in the management of patients, especially in a developing economy like Nigeria. In this study, we investigated the indications for transthoracic echocardiography and spectrum of cardiac disease found in patients referred to our cardiac unit for echocardiography. Methods: A prospective two-dimensional, pulsed, continuous, and color-flow Doppler echocardiographic evaluation was done using the transthoracic approach in 2501 patients over an eight-year period. Univariate data analysis was performed for mean age, gender, clinical indications, and diagnoses. Results: The subject age range was less than 12 months to 97 years (mean 52.39 years. There were 1352 (54.06% males and 1149 (45.94% females. The most common indication for echocardiography was hypertension (52.1% followed by congestive cardiac failure (13.9%. Others were for screening (6.1%, arrhythmias (5%, cerebrovascular disease (5%, chest pain (3.3%, chronic kidney disease (3.2%, congenital heart disease (2.6%, cardiomyopathy (1.8%, rheumatic heart disease (1.7%, diabetes mellitus (1.3%, thyrocardiac disease (1.2%, ischemic heart
Two-dimensional discrete gap breathers in a two-dimensional discrete diatomic Klein-Gordon lattice
XU Quan; QIANG Tian
2009-01-01
We study the existence and stability of two-dimensional discrete breathers in a two-dimensional discrete diatomic Klein-Gordon lattice consisting of alternating light and heavy atoms, with nearest-neighbor harmonic coupling.Localized solutions to the corresponding nonlinear differential equations with frequencies inside the gap of the linear wave spectrum, i.e. two-dimensional gap breathers, are investigated numerically. The numerical results of the corresponding algebraic equations demonstrate the possibility of the existence of two-dimensional gap breathers with three types of symmetries, i.e., symmetric, twin-antisymmetric and single-antisymmetric. Their stability depends on the nonlinear on-site potential (soft or hard), the interaction potential (attractive or repulsive)and the center of the two-dimensional gap breather (on a light or a heavy atom).
Schins, A.G.; Nielsen, M.; Arts, A.F.M.
1992-01-01
A neutron scattering study of the magnetic order in the randomly mixed two-dimensional ferromagnet-antiferromagnet Rb2Cu1-xCoxF4 has been performed. For x = 0.037, 0.083, and 0.88, the system enters an oblique ferromagnetic phase, an axial ferromagnetic, and an axial antiferromagnetic phase...
Ito, A.; Anma, T.
1987-03-01
Mössbauer measurements have been made on a two-dimensional (2D) random mixture K2Ni1- x Fe x F4 with competing spin anisotropies. The concentration versus temperature phase diagram predicted by Oguchi and Ishikawa for mixed systems with competition between orthorhombic anisotropies has been shown to exist in K2Ni1- x Fe x F4. The coexistence of two kinds of Mössbauer spectra is seen in the transition regions, and is believed to be an intrinsic property of this system.
Pendergraft, Odis C., Jr.; Burley, James R., II; Bare, E. Ann
1986-01-01
An investigation has been conducted in the Langley 16-Foot Transonic Tunnel to determine the effects of upper and lower external nozzle flap geometry on the external afterbody/nozzle drag of nonaxisymmetric two-dimensional convergent-divergent exhaust nozzles having parallel external sidewalls installed on a generic twin-engine, fighter-aircraft model. Tests were conducted over a Mach number range from 0.60 to 1.20 and over an angle-of-attack range from -5 to 9 deg. Nozzle pressure ratio was varied from jet off (1.0) to approximately 10.0, depending on Mach number.
Jost, G.; Tran, T.M.; Appert, K. [Ecole Polytechnique Federale, Lausanne (Switzerland). Centre de Recherche en Physique des Plasma (CRPP); Wuethrich, S. [CRAY Research, PATP/PSE, EPFL, Lausanne (Switzerland)
1996-12-01
A two-dimensional PIC code aimed at the investigation of electron-cyclotron beam instabilities in gyrotrons and their effects on the beam quality is presented. The code is based on recently developed techniques for handling charge conservation and open boundaries and uses an electromagnetic field which is decomposed in its transverse magnetic (TM) and electric (TE) components. The code has been implemented on the massively parallel computer CRAY T3D, and on the CRAY Y-MP. (author) figs., tabs., refs.
CHENG Yan-li; BAI Yu-hua; LI Jin-long; LIU Zhao-rong
2007-01-01
A modified two-dimensional Eulerian air quality model was used to simulate both the gaseous and particulate pollutant concentrations during October 21-24, 2004 in the Pearl River Delta (PRD) region, China. The most significant improvement to the model is the added capability to predict the secondary organic aerosols (SOA) concentrations because of the inclusion of the SOA formation chemistry. The meteorological input data were prepared using the CALMET meteorological model. The concentrations of aerosol-bound species such as NO3-, NH4+, SO42-, and SOA were calculated in the fine particle size range (＜2.5 μm). The results of the two-dimensional model were compared to the measurements at the ground level during the PRD Intensive Monitoring Campaign (IMC). Overall, there were good agreements between the measured and modeled concentrations of inorganic aerosol components and O3. Both the measured and the modeled results indicated that the maximum hourly O3 concentrations exceeded the China National Air Quality Standard. The predicted 24-h average SOA concentrations were in reasonable agreement with those predicted by the method of minimum OC/EC ratio.
Cao, Sheng; Zhou, Qing; Chen, Jin-Ling; Hu, Bo; Guo, Rui-Qiang
2016-09-01
To evaluate left atrial (LA) function in patients with ischemic (ICM) or idiopathic dilated (DCM) cardiomyopathy via two-dimensional speckle-tracking imaging. We measured the LA maximum volume, minimum volume, and volume before the atrial systole, and calculated total emptying volume, expansion index, active emptying volume, and fraction. We measured strain and strain rate during systole and late diastole using two-dimensional speckle-tracking imaging, and analyzed correlations between variables. We found no significant differences in LA size, left ventricle (LV) end-diastole diameter, LV ejection fraction (EF), E/A, E/e', deceleration time of the E wave, and effective mitral regurgitant orifice area between the DCM and the ICM group. However, the LA expansion index, active EF, systolic and late diastolic strain, and strain rate were lower in the ICM group (p speckle-tracking imaging is a promising method to differentiate these patients. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 44:437-445, 2016. © 2016 Wiley Periodicals, Inc.
A Numerical Solution of the Two-Dimensional Fusion Problem with Convective Boundary Conditions
Gülkaç, Vildan
2010-01-01
In this paper, we present an LOD method for solving the two-dimensional fusion problem with convective boundary conditions. In this study, we extend our earlier work [1] on the solution of the two-dimensional fusion problem by considering a class of time-split finite-difference methods, namely locally one-dimensional (LOD) schemes. In addition, following the idea of Douglas [2, 3], a Douglas-like splitting scheme is presented. A stability analysis by Fourier series method (von Neumann stability) of the scheme is also investigated. Computational results obtained by the present method are in excellent agreement with the results reported previously by other research.
Espinoza, A.; Beeksma, B.; Petasecca, M.; Fuduli, I.; Porumb, C.; Cutajar, D.; Lerch, M. L. F.; Rosenfeld, A. B. [Centre for Medical Radiation Physics, University of Wollongong, New South Wales 2522 (Australia); Corde, S.; Jackson, M. [Department of Radiation Oncology, Prince of Wales Hospital, New South Wales 2031 (Australia)
2013-11-15
Purpose: High dose rate (HDR) brachytherapy is a radiation treatment technique capable of delivering large dose rates to the tumor. Radiation is delivered using remote afterloaders to drive highly active sources (commonly {sup 192}Ir with an air KERMA strength range between 20 000 and 40 000 U, where 1 U = 1 μGy m{sup 2}/h in air) through applicators directly into the patient's prescribed region of treatment. Due to the obvious ramifications of incorrect treatment while using such an active source, it is essential that there are methods for quality assurance (QA) that can directly and accurately verify the treatment plan and the functionality of the remote afterloader. This paper describes the feasibility study of a QA system for HDR brachytherapy using a phantom based two-dimensional 11 × 11 epitaxial diode array, named “magic phantom.”Methods: The HDR brachytherapy treatment plan is translated to the phantom with two rows of 10 (20 in total) HDR source flexible catheters, arranged above and below the diode array “magic plate” (MP). Four-dimensional source tracking in each catheter is based upon a developed fast iterative algorithm, utilizing the response of the diodes in close proximity to the {sup 192}Ir source, sampled at 100 ms intervals by a fast data acquisition (DAQ) system. Using a {sup 192}Ir source in a solid water phantom, the angular response of the developed epitaxial diodes utilized in the MP and also the variation of the MP response as a function of the source-to-detector distance (SDD) were investigated. These response data are then used by an iterative algorithm for source dwelling position determination. A measurement of the average transit speed between dwell positions was performed using the diodes and a fast DAQ.Results: The angular response of the epitaxial diode showed a variation of 15% within 360°, with two flat regions above and below the detector face with less than 5% variation. For SDD distances of between 5 and 30 mm
UPWIND DISCONTINUOUS GALERKIN METHODS FOR TWO DIMENSIONAL NEUTRON TRANSPORT EQUATIONS
袁光伟; 沈智军; 闫伟
2003-01-01
In this paper the upwind discontinuous Galerkin methods with triangle meshes for two dimensional neutron transport equations will be studied.The stability for both of the semi-discrete and full-discrete method will be proved.
Entanglement Entropy for time dependent two dimensional holographic superconductor
Mazhari, N S; Myrzakulov, Kairat; Myrzakulov, R
2016-01-01
We studied entanglement entropy for a time dependent two dimensional holographic superconductor. We showed that the conserved charge of the system plays the role of the critical parameter to have condensation.
Decoherence in a Landau Quantized Two Dimensional Electron Gas
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.
Second invariant for two-dimensional classical super systems
S C Mishra; Roshan Lal; Veena Mishra
2003-10-01
Construction of superpotentials for two-dimensional classical super systems (for ≥ 2) is carried out. Some interesting potentials have been studied in their super form and also their integrability.
Sastry, V. S. S.; Polimeno, Antonino; Crepeau, Richard H.; Freed, Jack H.
1996-10-01
Two-dimensional Fourier transform (2D-FT)-electron spin resonance (ESR) studies on the small globular spin probe perdeuterated tempone (PDT) in the liquid crystal solvent 4O,8 (butoxy benzylidene octylaniline) are reported. These experiments, over the temperature range of 95 °C to 24 °C, cover the isotropic (I), nematic (N), smectic A (SA), smectic B (SB), and crystal (C) phases. The 2D-ELDOR (two-dimensional electron-electron double resonance) spectra confirm the anomalously rapid reorientation of PDT, especially in the lower temperature phases. The model of a slowly relaxing local structure (SRLS) leads to generally very good non-linear least squares (NLLS) global fits to the sets of 2D-ELDOR spectra obtained at each temperature. These fits are significantly better than those achieved by the standard model of Brownian reorientation in a macroscopic orienting potential. The SRLS model is able to account for anomalies first observed in an earlier 2D-ELDOR study on PDT in a different liquid crystal in its smectic phases. Although it is instructional to extract the various spectral densities from the COSY (correlation spectroscopy) and 2D-ELDOR spectra, the use of NLLS global fitting to a full set of 2D-ELDOR spectra is shown to be more reliable and convenient for obtaining optimum model parameters, especially in view of possible (incipient) slow motional effects from the SRLS or dynamic cage. The cage potential is found to remain fairly constant at about kBT over the various phases (with only a small drop in the SB phase), but its asymmetry increases with decreasing temperature T. This value is significantly larger than the weak macroscopic orienting potential which increases from 0.1 to 0.3kBT with decreasing T. The cage relaxation rate, given by Rc is about 3×107 s-1 in the I phase, but increases to about 108 s-1 in the SA, SB, and C phases. The rotational diffusion tensor for PDT shows only a small T-independent asymmetry, and its mean rotational diffusion
Li, Xiaofan; Shen, Xinyong; Liu, Jia
2014-05-01
Rainfall responses to doubled atmospheric carbon dioxide concentration were investigated through the analysis of two pairs of two-dimensional cloud-resolving model sensitivity experiments. One pair of experiments simulated pre-summer heavy rainfall over southern China around the summer solstice, whereas the other pair of experiments simulated tropical rainfall around the winter solstice. The analysis of the time and model domain mean heat budget revealed that the enhanced local atmospheric warming was associated with doubled carbon dioxide through the weakened infrared radiative cooling during the summer solstice. The weakened mean pre-summer rainfall corresponded to the weakened mean infrared radiative cooling. Doubled carbon dioxide increased the mean tropical atmospheric warming via the enhanced mean latent heat in correspondence with the strengthened mean infrared radiative cooling during the winter solstice. The enhanced mean tropical rainfall was associated with the increased mean latent heat.
Yuan-Xiang Jin; Yu-Yin Chen; Meng-Kui Xu; Yong-Huang Jiang
2004-03-01
Qualitative and quantitative differences in proteins expressed in the middle silkglands of male and female silkworm larvae that differ in silk colour were investigated by high resolution two-dimensional polyacrylamide gel electrophoresis (2-D PAGE), followed by computer assisted image analysis. About 1000 protein spots were resolved in both the sexes and most proteins were shown to be distributed in the area from 15 kDa to 70 kDa and pH 4–8. It was found that some proteins displayed higher expression in yellow cocoon, while two proteins were only expressed in female silkworm silkgland tissue through the comparison and analysis by two-D software. These proteins especially existed in female silkworm middle silkgland tissue of yellow cocoon. Furthermore, these proteins might be involved in the expression of cocoon colour phenotype.
Chrzanowska, Agnieszka
2017-06-01
A replica method for calculation of smectic liquid crystal properties within the Onsager theory has been presented and applied to an exemplary case of two-dimensional perfectly aligned needlelike boomerangs. The method allows one to consider the complete influence of the interaction terms in contrast to the Fourier expansion method which uses mostly first or second order terms of expansion. The program based on the replica algorithm is able to calculate a single representative layer as an equivalent set of layers, depending on the size of the considered width of the sample integration interval. It predicts successfully smectic density distributions, energies, and layer thicknesses for different types of layer arrangement—of the antiferroelectric or of the smectic A order type. Specific features of the algorithm performance and influence of the numerical accuracy on the physical properties are presented. Future applications of the replica method to freely rotating molecules are discussed.
Jiang, Eric Y.; Rieppo, Jarno
2006-11-01
This paper explores a new application of two-dimensional correlation spectroscopy (2DCOS) in FTIR spectroscopic imaging analysis of biological samples. A particular example demonstrated in this paper is the characterization of concentration gradients of collagen and proteoglycans in human patellar cartilage. A focal plane array detector-based FTIR imaging system has been proven to be an efficient tool to detect early collagen and proteoglycans degradation in developing osteoarthrosis through evaluating compositional changes of osteoarthritic cartilage along the depth. However, the closely overlapped bands of collagen and proteoglycans make normal spectral and spatial analysis difficult. With 2DCOS analysis of the imaging data, it is possible to enhance the spectral resolution and reveal distinctive compositional changes that are normally hidden with conventional approaches. The combined technique, FTIR imaging enhanced with 2DCOS, provides new possibilities to solve challenging problems in the analysis of complex biological systems.
Yanagisawa, Takashi
2016-11-01
The ground state of the two-dimensional (2D) Hubbard model is investigated by adopting improved wave functions that take into account intersite electron correlation beyond the Gutzwiller ansatz. The ground-state energy is lowered considerably, giving the best estimate of the ground-state energy for the 2D Hubbard model. There is a crossover from weakly to strongly correlated regions as the on-site Coulomb interaction U increases. The antiferromagnetic correlation induced by U is reduced for hole doping when U is large, being greater than the bandwidth, thus increasing the kinetic energy gain. The spin and charge fluctuations are induced in the strongly correlated region. These antiferromagnetic and kinetic charge fluctuations induce electron pairings, which results in high-temperature superconductivity.
Dai, Jin; Dyakov, Sergey A.; Bozhevolnyi, Sergey I.; Yan, Min
2016-09-01
Metamaterials possess artificial bulk and surface electromagnetic states. Tamed dispersion properties of surface waves allow one to achieve a controllable super-Planckian radiative heat transfer (RHT) process between two closely spaced objects. We numerically demonstrate enhanced RHT between two two-dimensional grooved metal plates by a full-wave scattering approach. The enhancement originates from both transverse-magnetic spoof surface-plasmon polaritons and a series of transverse-electric bonding- and anti-bonding-waveguide modes at surfaces. The RHT spectrum is frequency selective and highly geometrically tailorable. Our simulation also reveals thermally excited nonresonant surface waves in constituent metallic materials may play a prevailing role for RHT at an extremely small separation between two metal plates, rendering metamaterial modes insignificant for the energy-transfer process.
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.
Bankura, Arindam; Chandra, Amalendu, E-mail: amalen@iitk.ac.in [Department of Chemistry, Indian Institute of Technology, Kanpur 208016 (India)
2015-01-28
The dynamics of proton transfer (PT) through hydrogen bonds in a two-dimensional water layer confined between two graphene sheets at room temperature are investigated through ab initio and quantum-classical simulations. The excess proton is found to be mostly solvated as an Eigen cation where the hydronium ion donates three hydrogen bonds to the neighboring water molecules. In the solvation shell of the hydronium ion, the three coordinated water molecules with two donor hydrogen bonds are found to be properly presolvated to accept a proton. Although no hydrogen bond needs to be broken for transfer of a proton to such presolvated water molecules from the hydronium ion, the PT rate is still found to be not as fast as it is for one-dimensional chains. Here, the PT is slowed down as the probability of finding a water with two donor hydrogen bonds in the solvation shell of the hydronium ion is found to be only 25%-30%. The hydroxide ion is found to be solvated mainly as a complex anion where it accepts four H-bonds through its oxygen atom and the hydrogen atom of the hydroxide ion remains free all the time. Here, the presolvation of the hydroxide ion to accept a proton requires that one of its hydrogen bonds is broken and the proton comes from a neighboring water molecule with two acceptor and one donor hydrogen bonds. The coordination number reduction by breaking of a hydrogen bond is a slow process, and also the population of water molecules with two acceptor and one donor hydrogen bonds is only 20%-25% of the total number of water molecules. All these factors together tend to slow down the hydroxide ion migration rate in two-dimensional water layers compared to that in three-dimensional bulk water.
Bankura, Arindam; Chandra, Amalendu
2015-01-01
The dynamics of proton transfer (PT) through hydrogen bonds in a two-dimensional water layer confined between two graphene sheets at room temperature are investigated through ab initio and quantum-classical simulations. The excess proton is found to be mostly solvated as an Eigen cation where the hydronium ion donates three hydrogen bonds to the neighboring water molecules. In the solvation shell of the hydronium ion, the three coordinated water molecules with two donor hydrogen bonds are found to be properly presolvated to accept a proton. Although no hydrogen bond needs to be broken for transfer of a proton to such presolvated water molecules from the hydronium ion, the PT rate is still found to be not as fast as it is for one-dimensional chains. Here, the PT is slowed down as the probability of finding a water with two donor hydrogen bonds in the solvation shell of the hydronium ion is found to be only 25%-30%. The hydroxide ion is found to be solvated mainly as a complex anion where it accepts four H-bonds through its oxygen atom and the hydrogen atom of the hydroxide ion remains free all the time. Here, the presolvation of the hydroxide ion to accept a proton requires that one of its hydrogen bonds is broken and the proton comes from a neighboring water molecule with two acceptor and one donor hydrogen bonds. The coordination number reduction by breaking of a hydrogen bond is a slow process, and also the population of water molecules with two acceptor and one donor hydrogen bonds is only 20%-25% of the total number of water molecules. All these factors together tend to slow down the hydroxide ion migration rate in two-dimensional water layers compared to that in three-dimensional bulk water.
Strongly interacting two-dimensional Dirac fermions
Lim, L.K.; Lazarides, A.; Hemmerich, Andreas; de Morais Smith, C.
2009-01-01
We show how strongly interacting two-dimensional Dirac fermions can be realized with ultracold atoms in a two-dimensional optical square lattice with an experimentally realistic, inherent gauge field, which breaks time reversal and inversion symmetries. We find remarkable phenomena in a temperature
Topology optimization of two-dimensional waveguides
Jensen, Jakob Søndergaard; Sigmund, Ole
2003-01-01
In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss.......In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss....
Controlled Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers
2016-06-15
polymers . 2. Introduction . Research objectives: This research aims to study the physical (van der Waals forces: crystal epitaxy and π-π...AFRL-AFOSR-JP-TR-2016-0071 Controlled Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers Cheolmin Park YONSEI UNIVERSITY...Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA2386-14-1-4054 5c. PROGRAM ELEMENT
Phonon hydrodynamics in two-dimensional materials.
Cepellotti, Andrea; Fugallo, Giorgia; Paulatto, Lorenzo; Lazzeri, Michele; Mauri, Francesco; Marzari, Nicola
2015-03-06
The conduction of heat in two dimensions displays a wealth of fascinating phenomena of key relevance to the scientific understanding and technological applications of graphene and related materials. Here, we use density-functional perturbation theory and an exact, variational solution of the Boltzmann transport equation to study fully from first-principles phonon transport and heat conductivity in graphene, boron nitride, molybdenum disulphide and the functionalized derivatives graphane and fluorographene. In all these materials, and at variance with typical three-dimensional solids, normal processes keep dominating over Umklapp scattering well-above cryogenic conditions, extending to room temperature and more. As a result, novel regimes emerge, with Poiseuille and Ziman hydrodynamics, hitherto typically confined to ultra-low temperatures, characterizing transport at ordinary conditions. Most remarkably, several of these two-dimensional materials admit wave-like heat diffusion, with second sound present at room temperature and above in graphene, boron nitride and graphane.
Two-dimensional position sensitive neutron detector
A M Shaikh; S S Desai; A K Patra
2004-08-01
A two-dimensional position sensitive neutron detector has been developed. The detector is a 3He + Kr filled multiwire proportional counter with charge division position readout and has a sensitive area of 345 mm × 345 mm, pixel size 5 mm × 5 mm, active depth 25 mm and is designed for efficiency of 70% for 4 Å neutrons. The detector is tested with 0.5 bar 3He + 1.5 bar krypton gas mixture in active chamber and 2 bar 4He in compensating chamber. The pulse height spectrum recorded at an anode potential of 2000 V shows energy resolution of ∼ 25% for the 764 keV peak. A spatial resolution of 8 mm × 6 mm is achieved. The detector is suitable for SANS studies in the range of 0.02–0.25 Å-1.
Janus Spectra in Two-Dimensional Flows
Liu, Chien-Chia; Cerbus, Rory T.; Chakraborty, Pinaki
2016-09-01
In large-scale atmospheric flows, soap-film flows, and other two-dimensional flows, the exponent of the turbulent energy spectra, α , may theoretically take either of two distinct values, 3 or 5 /3 , but measurements downstream of obstacles have invariably revealed α =3 . Here we report experiments on soap-film flows where downstream of obstacles there exists a sizable interval in which α transitions from 3 to 5 /3 for the streamwise fluctuations but remains equal to 3 for the transverse fluctuations, as if two mutually independent turbulent fields of disparate dynamics were concurrently active within the flow. This species of turbulent energy spectra, which we term the Janus spectra, has never been observed or predicted theoretically. Our results may open up new vistas in the study of turbulence and geophysical flows.
Afchain, St
2005-02-15
The Hubbard model is the simplest model to describe the behaviour of fermions on a network, it takes into account only fermion scattering and only interactions with other fermions located on the same site. Half-filling means that the total number of fermions is equal to half the number of sites. In the first chapter we show how we can pass trough successive approximations from a very general Hamiltonian to the Hubbard Hamiltonian. The second chapter is dedicated to the passage from the Hamiltonian formalism to the Grassmanian functional formalism. The main idea is to show that the correlation functions of the Hamiltonian approach can be described through fermionic functional integrals which implies the possibility of speaking of the model in terms of field theory. The chapter 3 deals with the main constructive techniques that allow the strict and consistent construction of models inside the frame of field theory. We show by proving the violation of a condition concerning self-energy, that the two-dimensional Hubbard model at half-filling has not the behaviour of a Fermi liquid in the Landau's interpretation. (A.C.)
Zhang, C.; Taki, S. [Hiroshima Univ. (Japan). Dept. of Mech. Eng.
2000-11-01
The numerical simulation for the starting process of the ram accelerator in Hiroshima University (HURAMAC) has being made for almost the same conditions as the experiments, where CH{sub 4}-O{sub 2}-CO{sub 2} gas mixtures are used. The finite difference method is used for solving the Navier-Stokes equations including chemical reactions in the two-dimensional Cartesian coordinates. At first a test simulation is carried for the case of a cold shot with the same condition of our experiment. The structure of shock waves and the formation of expansion waves are clearly demonstrated. The simulation of a starting process of a hot shot is done for the similar conditions to one of the experiments. Numerical results show that the ignition source is formed just in front of the igniter although another high temperature region appears in the rear area of projectile. The normal shock wave is produced in front of the igniter, then it propagates forwards depending on the combustion heat release. Thermally choking mode is gradually established when the flame propagates whole cross section of the tube with the sabot ejected away from the projectile. The calculated pressure history is compared with the measured one at the middle point of the ignition tube. Very good agreement is found both in the time scale and the pressure amplitude. (orig.)
Shinzawa, Hideyuki; Awa, Kimie; Noda, Isao; Ozaki, Yukihiro
2013-02-01
Transient water absorption by cellulosic samples manufactured under varying pressure was monitored by near-infrared spectroscopy to explore the absorption behavior affected by the pressure. A substantial level of variation of the spectral features was induced by the water absorption and changes in the pressure. The detail of the spectral changes was analyzed with a multiple-perturbation, two-dimensional (2D) correlation method to determine the underlying mechanism. The 2D correlation spectra indicated that the compression of the cellulose increased the packing density of the samples, preventing the penetration of water. In addition, the compression substantially disintegrated its crystalline structure and eventually resulted in the development of inter- and intrachain hydrogen-bonded structures arising from an interaction between the water and cellulose. Consequently, the cellulose samples essentially underwent an evolutionary change in the polymer structure as well as in the packing density during the compression. This structural change, in turn, led to the seemingly complicated absorption trends, depending on the pressure.
Tomita, Yukio; Ishibashi, Yukio; Saito, Eiji; Saito, Toshio
1988-02-25
For elucidation of the flow behavior of a magnetic fluid as a one-phase fluid, water base ferrofluids were introduced in a two-dimensional channel and the action of a uniform vertical magnetic field axial magnetic field, and both fields inclined at various angles to examine the laminar flow region. The ferrofluids used in the experiment were prepared by dispersing 17.5 weight % of Fe/sub 3/ O/sub 4/ fine particles of about 100A in diameter into ion-exchange water, and adding an anionic sodium oleate to stabilize the dispersion. Under no action of the magnetic fields, ferrofluids having a higher concentration than the above value exhibited plastic fluid. As the direction of the magnetic field acting on the fluid approached the vertical, so the pressure loss was increased. The pipe friction coefficient could be expressed by the empirical formula of which the variables are the ratios of inertia force/viscous force and magnetic force/viscous force, and the inclination of the magnetic poles. (15 figs, 14 refs)
Two-Dimensional Materials for Sensing: Graphene and Beyond
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.
On the continua in two-dimensional nonadiabatic magnetohydrodynamic spectra
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
Two-dimensional wave propagation in layered periodic media
Quezada de Luna, Manuel
2014-09-16
We study two-dimensional wave propagation in materials whose properties vary periodically in one direction only. High order homogenization is carried out to derive a dispersive effective medium approximation. One-dimensional materials with constant impedance exhibit no effective dispersion. We show that a new kind of effective dispersion may arise in two dimensions, even in materials with constant impedance. This dispersion is a macroscopic effect of microscopic diffraction caused by spatial variation in the sound speed. We analyze this dispersive effect by using highorder homogenization to derive an anisotropic, dispersive effective medium. We generalize to two dimensions a homogenization approach that has been used previously for one-dimensional problems. Pseudospectral solutions of the effective medium equations agree to high accuracy with finite volume direct numerical simulations of the variable-coeffi cient equations.
Two Dimensional Plasmonic Cavities on Moire Surfaces
Balci, Sinan; Kocabas, Askin; Karabiyik, Mustafa; Kocabas, Coskun; Aydinli, Atilla
2010-03-01
We investigate surface plasmon polariton (SPP) cavitiy modes on two dimensional Moire surfaces in the visible spectrum. Two dimensional hexagonal Moire surface can be recorded on a photoresist layer using Interference lithography (IL). Two sequential exposures at slightly different angles in IL generate one dimensional Moire surfaces. Further sequential exposure for the same sample at slightly different angles after turning the sample 60 degrees around its own axis generates two dimensional hexagonal Moire cavity. Spectroscopic reflection measurements have shown plasmonic band gaps and cavity states at all the azimuthal angles (omnidirectional cavity and band gap formation) investigated. The plasmonic band gap edge and the cavity states energies show six fold symmetry on the two dimensional Moire surface as measured in reflection measurements.
Wang, Xiaoxiao; Wang, Huan; Huang, Jinfeng; Zhou, Yifeng; Tzvetanov, Tzvetomir
2017-01-01
The contrast sensitivity function that spans the two dimensions of contrast and spatial frequency is crucial in predicting functional vision both in research and clinical applications. In this study, the use of Bayesian inference was proposed to determine the parameters of the two-dimensional contrast sensitivity function. Two-dimensional Bayesian inference was extensively simulated in comparison to classical one-dimensional measures. Its performance on two-dimensional data gathered with different sampling algorithms was also investigated. The results showed that the two-dimensional Bayesian inference method significantly improved the accuracy and precision of the contrast sensitivity function, as compared to the more common one-dimensional estimates. In addition, applying two-dimensional Bayesian estimation to the final data set showed similar levels of reliability and efficiency across widely disparate and established sampling methods (from classical one-dimensional sampling, such as Ψ or staircase, to more novel multi-dimensional sampling methods, such as quick contrast sensitivity function and Fisher information gain). Furthermore, the improvements observed following the application of Bayesian inference were maintained even when the prior poorly matched the subject's contrast sensitivity function. Simulation results were confirmed in a psychophysical experiment. The results indicated that two-dimensional Bayesian inference of contrast sensitivity function data provides similar estimates across a wide range of sampling methods. The present study likely has implications for the measurement of contrast sensitivity function in various settings (including research and clinical settings) and would facilitate the comparison of existing data from previous studies. PMID:28119563
Ruiz, Osvaldo; Schouwenaars, Rafael; Ramírez, Edgar I.; Jacobo, Víctor H.; Ortiz, Armando
2011-10-01
Trabecular bone, rather than being considered as a homogeneous material, must be analysed as a structure of interconnected beam and plate-like elements. The arrangement and morphology of these elements depend on the specific tissue studied as well as on the physiology of the individual. It is therefore impossible to define the mechanical properties trabecular bone in general. To estimate the properties of an individual structure, flexible numerical models must be developed, which allow the calculation of elastic constants and resistance of tissue previously characterised by non-destructive observation. Voxel-based modelling of structures observed by X-ray microtomography is computation intensive. Here, synthetic 2D-microstructures are analysed, constructed as a collection of Voronoi-cells obtained from the observation of plane sections of cancellous bone. The effect of architecture (vertebra and femur), bone density and loss of trabecular connectivity was researched. The study confirms findings of earlier experimental and numerical studies relating to the effect of these parameters; the technique is efficient in terms of experimental effort and numerical analysis. Consequently, the use of synthetic microstructures based on a Voronoi-cell approximation of the real bone architecture may be a promising approach for the prediction of the mechanical properties of trabecular bone.
A Study on the New Two-Dimensional Hall Angular Detector%一种新型两维霍尔角度传感器研究
赖宗声; 蔡彦; 景圳; 贺德洪; 郑筱莉
2001-01-01
A new contactless two-dimensional integrated Hall Angular Detector was presented. A radial permanent magnet is attached to the axis whose angle position α is to be determined. Two orthogonal vertical Hall devices in cross shape, which active sensing area is 150μm×150 μm, measure the magnetic field X,Y components paralled to the chip surface and therefore the angular position α of the axis. When the permanent magnet was rotating, the measured output voltages V\\-x,V\\-y by the two pairs of vertical Hall plates were changed correspondingly. The angle α could be obtained by calculating the arc tangent of the signal ratio V\\-X/V\\-Y through the software and PC processor. The experimental results show an angular measurement accuracy of ±1° over a full 360° operating range.%本文研制了一种无触点的十字型两维集成垂直霍尔器件，它对平行于芯片表面的磁场敏感.当与被测转角α的物件轴向相固连的径向永久磁铁转动时，平行于芯片表面的磁场分量B\\-x、B\\-y大小将发生相对变化，以致集成的两对霍尔板输出电量也产生相应地变化.这时传感器件给出了相对于被测量角度α的两种信号电压(sinα和cosα)，通过arctgn(V\\-x/V\\-y)可求得转角α，从而达到测量角度的目的.测量结果表明利用该角度传感器件与PC机组成的测量系统其测量角度的精度可达±1°.
Cryptography Using Multiple Two-Dimensional Chaotic Maps
Ibrahim S. I. Abuhaiba
2012-08-01
Full Text Available In this paper, a symmetric key block cipher cryptosystem is proposed, involving multiple two-dimensional chaotic maps and using 128-bits external secret key. Computer simulations indicate that the cipher has good diffusion and confusion properties with respect to the plaintext and the key. Moreover, it produces ciphertext with random distribution. The computation time is much less than previous related works. Theoretic analysis verifies its superiority to previous cryptosystems against different types of attacks.
Previous studies underestimate BMAA concentrations in cycad flour.
Cheng, Ran; Banack, Sandra Anne
2009-01-01
The traditional diet of the Chamorro people of Guam has high concentrations of the neurotoxin BMAA, beta-methyl-amino-L-alanine, in cycad tortillas and from animals that feed on cycad seeds. We measured BMAA concentration in washed cycad flour and compared different extraction methods used by previous researchers in order to determine how much BMAA may have been unaccounted for in prior research. Samples were analyzed with AQC precolumn derivatization using HPLC-FD detection and verified with UPLC-UV, UPLC-MS, and triple quadrupole LC/MS/MS. Although previous workers had studied only the free amino acid component of BMAA in washed cycad flour, we detected significant levels of protein-associated BMAA in washed cycad flour. These data support a link between ALS/PDC and exposure to BMAA.
Bonetti, S.; Braggiotti, A.; Buckley, E.; Campanella, M.; Carugno, G.; Cecchet, G.; Cennini, P.; Centro, S.; Ciocio, A.; Cittolin, S.; Dainese, B.; Ferro-Luzzi, M.; Gasparini, F.; Gonidec, A.; Manfredi, P. F.; Meroni, E.; Muñoz, R.; Perreau, J.-M.; Pietropaolo, F.; Ptohos, F.; Ragusa, F.; Rossi, P.; Rubbia, C.; Schinzel, D.; Schmidt, W. F.; Seidl, W.
1990-01-01
We have tested a liquid argon time projection chamber with a novel wire configuration based on electrostatic focussing which allows the realization of a nondestructive detection of the electron image produced by ionizing events. The chamber was tested in a 5 GeV pion beam at the CERN proton synchrotron. The measured pulse shapes at both 200 V/cm and 500 V/cm were in very good agreement with the expected shapes, calculated taking into account the electron lifetime, the response of the electronics and the longitudinal diffusion of the electron cloud. The measured electron drift velocity was in good agreement with the results of other workers as well as with our previous measurements. We have also analysed a sample of events containing delta rays in order to study the behaviour of low-energy electrons in the liquid argon. We find that for electron energies greater than 5 MeV the measured energy spectrum agrees very well with the predicted spectrum after corrections for acceptance and energy loss, hence demonstrating the feasibility of recognizing low-energy electrons in liquid argon.
Qian Wan
2015-04-01
Full Text Available Research on shock wave mitigation in channels has been a topic of much attention in the shock wave community. One approach to attenuate an incident shock wave is to use obstacles of various geometries arranged in different patterns. This work is inspired by the study from Chaudhuri et al. (2013, in which cylinders, squares and triangles placed in staggered and non-staggered subsequent columns were used to attenuate a planar incident shock wave. Here, we present numerical simulations using a different obstacle pattern. Instead of using a matrix of obstacles, an arrangement of square or cylindrical obstacles placed along a logarithmic spiral curve is investigated, which is motivated by our previous work on shock focusing using logarithmic spirals. Results show that obstacles placed along a logarithmic spiral can delay both the transmitted and the reflected shock wave. For different incident shock Mach numbers, away from the logarithmic spiral design Mach number, this shape is effective to either delay the transmitted or the reflected shock wave. Results also confirm that the degree of attenuation depends on the obstacle shape, effective flow area and obstacle arrangement, much like other obstacle configurations.
Sastry, V. S. S.; Polimeno, Antonino; Crepeau, Richard H.; Freed, Jack H.
1996-10-01
Two-dimensional Fourier transform (2D-FT) electron spin resonance (ESR) studies on the rigid rodlike cholestane (CSL) spin-label in the liquid crystal solvent 4O,8 (butoxy benzylidene octylaniline) are reported. These experiments were performed over a wide temperature range: 96 °C to 25 °C covering the isotropic (I), nematic (N), smectic A (SA), smectic B (SB), and crystal (C) phases. It is shown that 2D-FT-ESR, especially in the form of 2D-ELDOR (two-dimensional electron-electron double resonance) provides greatly enhanced sensitivity to rotational dynamics than previous cw-ESR studies on this and related systems. This sensitivity is enhanced by obtaining a series of 2D-ELDOR spectra as a function of mixing time, Tm, yielding essentially a three-dimensional experiment. Advantage is taken of this sensitivity to study the applicability of the model of a slowly relaxing local structure (SRLS). In this model, a dynamic cage of solvent molecules, which relaxes on a slower time scale than the CSL solute, provides a local orienting potential in addition to that of the macroscopic aligning potential in the liquid crystalline phase. The theory of Polimeno and Freed for SRLS in the ESR slow motional regime is extended by utilizing the theory of Lee et al. to include 2D-FT-ESR experiments, and it serves as the basis for the analysis of the 2D-ELDOR experiments. It is shown that the SRLS model leads to significantly improved non-linear least squares fits to experiment over those obtained with the standard model of Brownian reorientation in a macroscopic aligning potential. This is most evident for the SA phase, and the use of the SRLS model also removes the necessity of fitting with the unreasonably large CSL rotational asymmetries in the smectic phases that are required in both the cw-ESR and 2D-ELDOR fits with the standard model. The cage potential is found to vary from about kBT in the isotropic phase to greater than 2kBT in the N and SA phases, with an abrupt drop to
Interpolation by two-dimensional cubic convolution
Shi, Jiazheng; Reichenbach, Stephen E.
2003-08-01
This paper presents results of image interpolation with an improved method for two-dimensional cubic convolution. Convolution with a piecewise cubic is one of the most popular methods for image reconstruction, but the traditional approach uses a separable two-dimensional convolution kernel that is based on a one-dimensional derivation. The traditional, separable method is sub-optimal for the usual case of non-separable images. The improved method in this paper implements the most general non-separable, two-dimensional, piecewise-cubic interpolator with constraints for symmetry, continuity, and smoothness. The improved method of two-dimensional cubic convolution has three parameters that can be tuned to yield maximal fidelity for specific scene ensembles characterized by autocorrelation or power-spectrum. This paper illustrates examples for several scene models (a circular disk of parametric size, a square pulse with parametric rotation, and a Markov random field with parametric spatial detail) and actual images -- presenting the optimal parameters and the resulting fidelity for each model. In these examples, improved two-dimensional cubic convolution is superior to several other popular small-kernel interpolation methods.
On final states of two-dimensional decaying turbulence
Yin, Z.
2004-12-01
Numerical and analytical studies of final states of two-dimensional (2D) decaying turbulence are carried out. The first part of this work is trying to give a definition for final states of 2D decaying turbulence. The functional relation of ω-ψ, which is frequently adopted as the characterization of those final states, is merely a sufficient but not necessary condition; moreover, it is not proper to use it as the definition. It is found that the method through the value of the effective area S covered by the scatter ω-ψ plot, initially suggested by Read, Rhines, and White ["Geostrophic scatter diagrams and potential vorticity dynamics," J. Atmos. Sci. 43, 3226 (1986)] is more general and suitable for the definition. Based on this concept, a definition is presented, which covers all existing results in late states of decaying 2D flows (including some previous unexplainable weird double-valued ω-ψ scatter plots). The remaining part of the paper is trying to further study 2D decaying turbulence with the assistance of this definition. Some numerical results, leading to "bar" final states and further verifying the predictive ability of statistical mechanics [Yin, Montgomery, and Clercx, "Alternative statistical-mechanical descriptions of decaying two-dimensional turbulence in terms of patches and points," Phys. Fluids 15, 1937 (2003)], are reported. It is realized that some simulations with narrow-band energy spectral initial conditions result in some final states that cannot be very well interpreted by the statistical theory (meanwhile, those final states are still in the scope of the definition).
Two-Dimensional Phononic Crystals: Disorder Matters.
Wagner, Markus R; Graczykowski, Bartlomiej; Reparaz, Juan Sebastian; El Sachat, Alexandros; Sledzinska, Marianna; Alzina, Francesc; Sotomayor Torres, Clivia M
2016-09-14
The design and fabrication of phononic crystals (PnCs) hold the key to control the propagation of heat and sound at the nanoscale. However, there is a lack of experimental studies addressing the impact of order/disorder on the phononic properties of PnCs. Here, we present a comparative investigation of the influence of disorder on the hypersonic and thermal properties of two-dimensional PnCs. PnCs of ordered and disordered lattices are fabricated of circular holes with equal filling fractions in free-standing Si membranes. Ultrafast pump and probe spectroscopy (asynchronous optical sampling) and Raman thermometry based on a novel two-laser approach are used to study the phononic properties in the gigahertz (GHz) and terahertz (THz) regime, respectively. Finite element method simulations of the phonon dispersion relation and three-dimensional displacement fields furthermore enable the unique identification of the different hypersonic vibrations. The increase of surface roughness and the introduction of short-range disorder are shown to modify the phonon dispersion and phonon coherence in the hypersonic (GHz) range without affecting the room-temperature thermal conductivity. On the basis of these findings, we suggest a criteria for predicting phonon coherence as a function of roughness and disorder.
Perspective: Two-dimensional resonance Raman spectroscopy
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.
Janus spectra in two-dimensional flows
Liu, Chien-Chia; Chakraborty, Pinaki
2016-01-01
In theory, large-scale atmospheric flows, soap-film flows and other two-dimensional flows may host two distinct types of turbulent energy spectra---in one, $\\alpha$, the spectral exponent of velocity fluctuations, equals $3$ and the fluctuations are dissipated at the small scales, and in the other, $\\alpha=5/3$ and the fluctuations are dissipated at the large scales---but measurements downstream of obstacles have invariably revealed $\\alpha = 3$. Here we report experiments on soap-film flows where downstream of obstacles there exists a sizable interval in which $\\alpha$ has transitioned from $3$ to $5/3$ for the streamwise fluctuations but remains equal to $3$ for the transverse fluctuations, as if two mutually independent turbulent fields of disparate dynamics were concurrently active within the flow. This species of turbulent energy spectra, which we term the Janus spectra, has never been observed or predicted theoretically. Our results may open up new vistas in the study of turbulence and geophysical flows...
Comparative Two-Dimensional Fluorescence Gel Electrophoresis.
Ackermann, Doreen; König, Simone
2018-01-01
Two-dimensional comparative fluorescence gel electrophoresis (CoFGE) uses an internal standard to increase the reproducibility of coordinate assignment for protein spots visualized on 2D polyacrylamide gels. This is particularly important for samples, which need to be compared without the availability of replicates and thus cannot be studied using differential gel electrophoresis (DIGE). CoFGE corrects for gel-to-gel variability by co-running with the sample proteome a standardized marker grid of 80-100 nodes, which is formed by a set of purified proteins. Differentiation of reference and analyte is possible by the use of two fluorescent dyes. Variations in the y-dimension (molecular weight) are corrected by the marker grid. For the optional control of the x-dimension (pI), azo dyes can be used. Experiments are possible in both vertical and horizontal (h) electrophoresis devices, but hCoFGE is much easier to perform. For data analysis, commercial software capable of warping can be adapted.
Radiation effects on two-dimensional materials
Walker, R.C. II; Robinson, J.A. [Department of Materials Science, Penn State, University Park, PA (United States); Center for Two-Dimensional Layered Materials, Penn State, University Park, PA (United States); Shi, T. [Department of Mechanical and Nuclear Engineering, Penn State, University Park, PA (United States); Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI (United States); Silva, E.C. [GlobalFoundries, Malta, NY (United States); Jovanovic, I. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI (United States)
2016-12-15
The effects of electromagnetic and particle irradiation on two-dimensional materials (2DMs) are discussed in this review. Radiation creates defects that impact the structure and electronic performance of materials. Determining the impact of these defects is important for developing 2DM-based devices for use in high-radiation environments, such as space or nuclear reactors. As such, most experimental studies have been focused on determining total ionizing dose damage to 2DMs and devices. Total dose experiments using X-rays, gamma rays, electrons, protons, and heavy ions are summarized in this review. We briefly discuss the possibility of investigating single event effects in 2DMs based on initial ion beam irradiation experiments and the development of 2DM-based integrated circuits. Additionally, beneficial uses of irradiation such as ion implantation to dope materials or electron-beam and helium-beam etching to shape materials have begun to be used on 2DMs and are reviewed as well. For non-ionizing radiation, such as low-energy photons, we review the literature on 2DM-based photo-detection from terahertz to UV. The majority of photo-detecting devices operate in the visible and UV range, and for this reason they are the focus of this review. However, we review the progress in developing 2DMs for detecting infrared and terahertz radiation. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Predicting Two-Dimensional Silicon Carbide Monolayers.
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.
Spectral Radiative Properties of Two-Dimensional Rough Surfaces
Xuan, Yimin; Han, Yuge; Zhou, Yue
2012-12-01
Spectral radiative properties of two-dimensional rough surfaces are important for both academic research and practical applications. Besides material properties, surface structures have impact on the spectral radiative properties of rough surfaces. Based on the finite difference time domain algorithm, this paper studies the spectral energy propagation process on a two-dimensional rough surface and analyzes the effect of different factors such as the surface structure, angle, and polarization state of the incident wave on the spectral radiative properties of the two-dimensional rough surface. To quantitatively investigate the spatial distribution of energy reflected from the rough surface, the concept of the bidirectional reflectance distribution function is introduced. Correlation analysis between the reflectance and different impact factors is conducted to evaluate the influence degree. Comparison between the theoretical and experimental data is given to elucidate the accuracy of the computational code. This study is beneficial to optimizing the surface structures of optoelectronic devices such as solar cells.
Two-dimensional x-ray diffraction
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
Matching Two-dimensional Gel Electrophoresis' Spots
Dos Anjos, António; AL-Tam, Faroq; Shahbazkia, Hamid Reza
2012-01-01
This paper describes an approach for matching Two-Dimensional Electrophoresis (2-DE) gels' spots, involving the use of image registration. The number of false positive matches produced by the proposed approach is small, when compared to academic and commercial state-of-the-art approaches. This ar......This paper describes an approach for matching Two-Dimensional Electrophoresis (2-DE) gels' spots, involving the use of image registration. The number of false positive matches produced by the proposed approach is small, when compared to academic and commercial state-of-the-art approaches...
Nonlinear excitations in two-dimensional molecular structures with impurities
Gaididei, Yuri Borisovich; Rasmussen, Kim; Christiansen, Peter Leth
1995-01-01
We study the nonlinear dynamics of electronic excitations interacting with acoustic phonons in two-dimensional molecular structures with impurities. We show that the problem is reduced to the nonlinear Schrodinger equation with a varying coefficient. The latter represents the influence of the imp......We study the nonlinear dynamics of electronic excitations interacting with acoustic phonons in two-dimensional molecular structures with impurities. We show that the problem is reduced to the nonlinear Schrodinger equation with a varying coefficient. The latter represents the influence...... excitations. Analytical results are in good agreement with numerical simulations of the nonlinear Schrodinger equation....
ZHOU Peng; MEI Hu; TIAN Feifei; WANG Jiaona; WU Shirong; LI Zhiliang
2007-01-01
Based on two-dimensional topological characters,a novel method called molecular electronegativityinteraction vector(MEIV)is proposed to parameterize molecular structures.Applying MEIV into quantitative structure-spectrometry relationship studies on ion mobility spectrometry collision cross-sections of 113 singly protonated peptides,three models were strictly obtained,with correlative coefficient r and leave-one-out cross-validation q of 0.983,0.979,0.981,0.979 and 0.980,0.978,respectively.Thus,the MEIV is confirmed to be potent to structural characterizations and property predictions for organic and biologic molecules.
Density of States of Weakly Disordered Two-Dimensional Frenkel Excitons
Zettili, Nouredine; Boukahil, A.
2005-03-01
The Coherent Potential Approximation (CPA) is used to study the optical properties of weakly disordered two-dimensional Frenkel exciton systems with nearest neighbor interactions. The transition frequencies are assumed to have Gaussian distribution. An approximate complex logarithmic Green's function for a square lattice with nearest neighbor interactions is used in the CPA self-consistent equation to determine the coherent potential. We show that the CPA results are in excellent agreement with previous numerical investigations.
Non perturbative methods in two dimensional quantum field theory
Abdalla, Elcio; Rothe, Klaus D
1991-01-01
This book is a survey of methods used in the study of two-dimensional models in quantum field theory as well as applications of these theories in physics. It covers the subject since the first model, studied in the fifties, up to modern developments in string theories, and includes exact solutions, non-perturbative methods of study, and nonlinear sigma models.
Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.
Wang, Qing Hua; Kalantar-Zadeh, Kourosh; Kis, Andras; Coleman, Jonathan N; Strano, Michael S
2012-11-01
The remarkable properties of graphene have renewed interest in inorganic, two-dimensional materials with unique electronic and optical attributes. Transition metal dichalcogenides (TMDCs) are layered materials with strong in-plane bonding and weak out-of-plane interactions enabling exfoliation into two-dimensional layers of single unit cell thickness. Although TMDCs have been studied for decades, recent advances in nanoscale materials characterization and device fabrication have opened up new opportunities for two-dimensional layers of thin TMDCs in nanoelectronics and optoelectronics. TMDCs such as MoS(2), MoSe(2), WS(2) and WSe(2) have sizable bandgaps that change from indirect to direct in single layers, allowing applications such as transistors, photodetectors and electroluminescent devices. We review the historical development of TMDCs, methods for preparing atomically thin layers, their electronic and optical properties, and prospects for future advances in electronics and optoelectronics.
Control Operator for the Two-Dimensional Energized Wave Equation
Sunday Augustus REJU
2006-07-01
Full Text Available This paper studies the analytical model for the construction of the two-dimensional Energized wave equation. The control operator is given in term of space and time t independent variables. The integral quadratic objective cost functional is subject to the constraint of two-dimensional Energized diffusion, Heat and a source. The operator that shall be obtained extends the Conjugate Gradient method (ECGM as developed by Hestenes et al (1952, [1]. The new operator enables the computation of the penalty cost, optimal controls and state trajectories of the two-dimensional energized wave equation when apply to the Conjugate Gradient methods in (Waziri & Reju, LEJPT & LJS, Issues 9, 2006, [2-4] to appear in this series.
A two-dimensional spin liquid in quantum kagome ice.
Carrasquilla, Juan; Hao, Zhihao; Melko, Roger G
2015-06-22
Actively sought since the turn of the century, two-dimensional quantum spin liquids (QSLs) are exotic phases of matter where magnetic moments remain disordered even at zero temperature. Despite ongoing searches, QSLs remain elusive, due to a lack of concrete knowledge of the microscopic mechanisms that inhibit magnetic order in materials. Here we study a model for a broad class of frustrated magnetic rare-earth pyrochlore materials called quantum spin ices. When subject to an external magnetic field along the [111] crystallographic direction, the resulting interactions contain a mix of geometric frustration and quantum fluctuations in decoupled two-dimensional kagome planes. Using quantum Monte Carlo simulations, we identify a set of interactions sufficient to promote a groundstate with no magnetic long-range order, and a gap to excitations, consistent with a Z2 spin liquid phase. This suggests an experimental procedure to search for two-dimensional QSLs within a class of pyrochlore quantum spin ice materials.
Schumacher, O.
2007-07-20
In this thesis magneto-resistance studies on evenly curved two-dimensional electron systems in cylindric geometry are presented and discussed. A principle first introduced by Prinz and co-workers in 1998 enables us to roll up thin semiconductor layer systems by taking advantage of internal elastic strain. The radius of such a semiconductor tube can be adjusted ranging from a few nanometers up to several micrometers. The tubes' shape and place on the substrate can be defined by lithographic methods which are presented in this work. Furthermore, we show rolled-up structures containing a two-dimensional electron system in the tube wall. With a special lithographic procedure we are able to structure, to contact and to roll up these 2D-electron-gases in Hall geometry. As a result, a cylindric two-dimensional electron system is produced, which experiences a modulation of the perpendicular magnetic field component. The radius of curvature of our structures is about 10 {mu}m, the carrier mobility is optimized to values up to 125,000 cm{sup 2}/Vs. In transport experiments on curved Hall bars containing two dimensional electron systems two Hall bar orientations, with respect to the curvature, may be distinguished. In this work both orientations, i.e. with a Hall bar along the tube curvature as well as a Hall bar along the tube axis, are presented and discussed. Measurements on Hall bars along the curvature show signatures in the longitudinal resistance, which can be understood with the help of the Landauer-Buttiker-formalism and the model of magnetic barriers. For Hall bars oriented along the tube axis the perpendicular magnetic field component averaged over the width of the bar defines the minimum position of the Shubnikov-de Haas-oscillations as well as the slope of the Hall resistance. Furthermore, measurements on so-called van the Pauw-lamellas are presented. In this geometry the magneto-resistance shows a slope which refers to highly mobile conditions at the zero
Singular analysis of two-dimensional bifurcation system
无
2010-01-01
Bifurcation properties of two-dimensional bifurcation system are studied in this paper.Universal unfolding and transition sets of the bifurcation equations are obtained.The whole parametric plane is divided into several different persistent regions according to the type of motion,and the different qualitative bifurcation diagrams in different persistent regions are given.The bifurcation properties of the two-dimensional bifurcation system are compared with its reduced one-dimensional system.It is found that the system which is reduced to one dimension has lost many bifurcation properties.
Critical Behaviour of a Two-Dimensional Random Antiferromagnet
Als-Nielsen, Jens Aage; Birgeneau, R. J.; Guggenheim, H. J.
1976-01-01
A neutron scattering study of the order parameter, correlation length and staggered susceptibility of the two-dimensional random antiferromagnet Rb2Mn0.5Ni0.5F4 is reported. The system is found to exhibit a well-defined phase transition with critical exponents identical to those of the isomorphou...... pure materials K2NiF4 and K2MnF4. Thus, in these systems, which have the asymptotic critical behaviour of the two-dimensional Ising model, randomness has no measurable effect on the phase-transition behaviour....
Two-Dimensional Toda-Heisenberg Lattice
Vadim E. Vekslerchik
2013-06-01
Full Text Available We consider a nonlinear model that is a combination of the anisotropic two-dimensional classical Heisenberg and Toda-like lattices. In the framework of the Hirota direct approach, we present the field equations of this model as a bilinear system, which is closely related to the Ablowitz-Ladik hierarchy, and derive its N-soliton solutions.
A novel two dimensional particle velocity sensor
Pjetri, Olti; Wiegerink, Remco J.; Lammerink, Theo S.; Krijnen, Gijs J.
2013-01-01
In this paper we present a two wire, two-dimensional particle velocity sensor. The miniature sensor of size 1.0x2.5x0.525 mm, consisting of only two crossed wires, shows excellent directional sensitivity in both directions, thus requiring no directivity calibration, and is relatively easy to fabrica
Two-dimensional microstrip detector for neutrons
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.
Two-dimensional magma-repository interactions
Bokhove, O.
2001-01-01
Two-dimensional simulations of magma-repository interactions reveal that the three phases --a shock tube, shock reflection and amplification, and shock attenuation and decay phase-- in a one-dimensional flow tube model have a precursor. This newly identified phase ``zero'' consists of the impact of
A two-dimensional Dirac fermion microscope
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...
Forensic potential of comprehensive two-dimensional gas chromatography
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
Forensic potential of comprehensive two-dimensional gas chromatography
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
Mapping two-dimensional polar active fluids to two-dimensional soap and one-dimensional sandblasting
Chen, Leiming; Lee, Chiu Fan; Toner, John
2016-07-01
Active fluids and growing interfaces are two well-studied but very different non-equilibrium systems. Each exhibits non-equilibrium behaviour distinct from that of their equilibrium counterparts. Here we demonstrate a surprising connection between these two: the ordered phase of incompressible polar active fluids in two spatial dimensions without momentum conservation, and growing one-dimensional interfaces (that is, the 1+1-dimensional Kardar-Parisi-Zhang equation), in fact belong to the same universality class. This universality class also includes two equilibrium systems: two-dimensional smectic liquid crystals, and a peculiar kind of constrained two-dimensional ferromagnet. We use these connections to show that two-dimensional incompressible flocks are robust against fluctuations, and exhibit universal long-ranged, anisotropic spatio-temporal correlations of those fluctuations. We also thereby determine the exact values of the anisotropy exponent ζ and the roughness exponents χx,y that characterize these correlations.
李未; 陈小玲
2011-01-01
利用二维三角晶格介质柱光子晶体TE偏振的禁带与介质柱半径的变化关系,分析了二维光子晶体的带隙分布及斜边耦合特性.结果表明,光子禁带的大小受到构成光子晶体的介电材料的空间排列分布以及介质柱半径大小的影响;束缚在光子晶体中的光波可以在波导和谐振腔中进行传输,达到选择输出光波的目的.%The paper study the relation between two dimensional triangular lattice photonic crystal band gap for TE polarizationand dielectric cylinder radius, and study distribution of two dimensional photonic crystal defect state. Results show, the photonic crystal band gaps were distributed by dielectric material space distribution and medium size of the radius; Tied in the photon crystals of light waves can transmission in waveguides and resonator cavity to select the output of light waves.
Interaction of two-dimensional magnetoexcitons
Dumanov, E. V.; Podlesny, I. V.; Moskalenko, S. A.; Liberman, M. A.
2017-04-01
We study interaction of the two-dimensional magnetoexcitons with in-plane wave vector k→∥ = 0 , taking into account the influence of the excited Landau levels (ELLs) and of the external electric field perpendicular to the surface of the quantum well and parallel to the external magnetic field. It is shown that the account of the ELLs gives rise to the repulsion between the spinless magnetoexcitons with k→∥ = 0 in the Fock approximation, with the interaction constant g decreasing inverse proportional to the magnetic field strength B (g (0) ∼ 1 / B) . In the presence of the perpendicular electric field the Rashba spin-orbit coupling (RSOC), Zeeman splitting (ZS) and nonparabolicity of the heavy-hole dispersion law affect the Landau quantization of the electrons and holes. They move along the new cyclotron orbits, change their Coulomb interactions and cause the interaction between 2D magnetoexcitons with k→∥ = 0 . The changes of the Coulomb interactions caused by the electrons and by the holes moving with new cyclotron orbits are characterized by some coefficients, which in the absence of the electric field turn to be unity. The differences between these coefficients of the electron-hole pairs forming the magnetoexcitons determine their affinities to the interactions. The interactions between the homogeneous, semihomogeneous and heterogeneous magnetoexcitons forming the symmetric states with the same signs of their affinities are attractive whereas in the case of different sign affinities are repulsive. In the heterogeneous asymmetric states the interactions have opposite signs in comparison with the symmetric states. In all these cases the interaction constant g have the dependence g (0) 1 /√{ B} .
Rezaei, M. P.; Zamanian, M.
2017-01-01
In this paper, the influences of nonideal boundary conditions (due to flexibility) on the primary resonant behavior of a piezoelectrically actuated microbeam have been studied, for the first time. The structure has been assumed to treat as an Euler-Bernoulli beam, considering the effects of geometric nonlinearity. In this work, the general nonideal supports have been modeled as a the combination of horizontal, vertical and rotational springs, simultaneously. Allocating particular values to the stiffness of these springs provides the mathematical models for the majority of boundary conditions. This consideration leads to use a two-dimensional analysis of the multiple scales method instead of previous works' method (one-dimensional analysis). If one neglects the nonideal effects, then this paper would be an effort to solve the two-dimensional equations of motion without a need of a combination of these equations using the shortening or stretching effect. Letting the nonideal effects equal to zero and comparing their results with the results of previous approaches have been demonstrated the accuracy of the two-dimensional solutions. The results have been identified the unique effects of constraining and stiffening of boundaries in horizontal, vertical and rotational directions. This means that it is inaccurate to suppose the nonideality of supports only in one or two of these directions like as previous works. The findings are of vital importance as a better prediction of the frequency response for the nonideal supports. Furthermore, the main findings of this effort can help to choose appropriate boundary conditions for desired systems.
Numerical blowup in two-dimensional Boussinesq equations
Yin, Zhaohua
2009-01-01
In this paper, we perform a three-stage numerical relay to investigate the finite time singularity in the two-dimensional Boussinesq approximation equations. The initial asymmetric condition is the middle-stage output of a $2048^2$ run, the highest resolution in our study is $40960^2$, and some signals of numerical blowup are observed.
Exact two-dimensional superconformal R symmetry and c extremization.
Benini, Francesco; Bobev, Nikolay
2013-02-08
We uncover a general principle dubbed c extremization, which determines the exact R symmetry of a two-dimensional unitary superconformal field theory with N=(0,2) supersymmetry. To illustrate its utility, we study superconformal theories obtained by twisted compactifications of four-dimensional N=4 super-Yang-Mills theory on Riemann surfaces and construct their gravity duals.
Zero sound in a two-dimensional dipolar Fermi gas
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
Magnetic order in two-dimensional nanoparticle assemblies
Georgescu, M
2008-01-01
This thesis involves a fundamental study of two-dimensional arrays of magnetic nanoparticles using non-contact Atomic Force Microscopy, Magnetic Force Microscopy, and Atomic Force Spectroscopy. The goal is to acquire a better understanding of the interactions between magnetic nanoparticles and the
Two-dimensional static black holes with pointlike sources
Melis, M
2004-01-01
We study the static black hole solutions of generalized two-dimensional dilaton-gravity theories generated by pointlike mass sources, in the hypothesis that the matter is conformally coupled. We also discuss the motion of test particles. Due to conformal coupling, these follow the geodesics of a metric obtained by rescaling the canonical metric with the dilaton.
Magnetic order in two-dimensional nanoparticle assemblies
Georgescu, M
2008-01-01
This thesis involves a fundamental study of two-dimensional arrays of magnetic nanoparticles using non-contact Atomic Force Microscopy, Magnetic Force Microscopy, and Atomic Force Spectroscopy. The goal is to acquire a better understanding of the interactions between magnetic nanoparticles and the r
Two-dimensional effects in nonlinear Kronig-Penney models
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...
Two Dimensional F(R) Horava-Lifshitz Gravity
Kluson, J
2016-01-01
We study two-dimensional F(R) Horava-Lifshitz gravity from the Hamiltonian point of view. We determine constraints structure with emphasis on the careful separation of the second class constraints and global first class constraints. We determine number of physical degrees of freedom and also discuss gauge fixing of the global first class constraints.
Boundary-value problems for two-dimensional canonical systems
Hassi, Seppo; De Snoo, H; Winkler, Henrik
2000-01-01
The two-dimensional canonical system Jy' = -lHy where the nonnegative Hamiltonian matrix function H(x) is trace-normed on (0,∞) has been studied in a function-theoretic way by L. de Branges. We show that the Hamiltonian system induces a closed symmetric relation which can be reduced to a, not necess
Two-dimensional manifold with point-like defects
Gani, Vakhid A; Rubin, Sergei G
2014-01-01
We study a class of two-dimensional extra spaces isomorphic to the $S^2$ sphere in the framework of the multidimensional gravitation. We show that there exists a family of stationary metrics that depend on the initial (boundary) conditions. All these geometries have a singular point. We also discuss the possibility for these deformed extra spaces to be considered as dark matter candidates.
Discovery of intrinsic ferromagnetism in two-dimensional van der Waals crystals
Gong, Cheng; Li, Lin; Li, Zhenglu; Ji, Huiwen; Stern, Alex; Xia, Yang; Cao, Ting; Bao, Wei; Wang, Chenzhe; Wang, Yuan; Qiu, Z. Q.; Cava, R. J.; Louie, Steven G.; Xia, Jing; Zhang, Xiang
2017-06-01
The realization of long-range ferromagnetic order in two-dimensional van der Waals crystals, combined with their rich electronic and optical properties, could lead to new magnetic, magnetoelectric and magneto-optic applications. In two-dimensional systems, the long-range magnetic order is strongly suppressed by thermal fluctuations, according to the Mermin-Wagner theorem; however, these thermal fluctuations can be counteracted by magnetic anisotropy. Previous efforts, based on defect and composition engineering, or the proximity effect, introduced magnetic responses only locally or extrinsically. Here we report intrinsic long-range ferromagnetic order in pristine Cr2Ge2Te6 atomic layers, as revealed by scanning magneto-optic Kerr microscopy. In this magnetically soft, two-dimensional van der Waals ferromagnet, we achieve unprecedented control of the transition temperature (between ferromagnetic and paramagnetic states) using very small fields (smaller than 0.3 tesla). This result is in contrast to the insensitivity of the transition temperature to magnetic fields in the three-dimensional regime. We found that the small applied field leads to an effective anisotropy that is much greater than the near-zero magnetocrystalline anisotropy, opening up a large spin-wave excitation gap. We explain the observed phenomenon using renormalized spin-wave theory and conclude that the unusual field dependence of the transition temperature is a hallmark of soft, two-dimensional ferromagnetic van der Waals crystals. Cr2Ge2Te6 is a nearly ideal two-dimensional Heisenberg ferromagnet and so will be useful for studying fundamental spin behaviours, opening the door to exploring new applications such as ultra-compact spintronics.
Electromagnetic Wave Propagation in Two-Dimensional Photonic Crystals
Stavroula Foteinopoulou
2003-12-12
In this dissertation, they have undertaken the challenge to understand the unusual propagation properties of the photonic crystal (PC). The photonic crystal is a medium where the dielectric function is periodically modulated. These types of structures are characterized by bands and gaps. In other words, they are characterized by frequency regions where propagation is prohibited (gaps) and regions where propagation is allowed (bands). In this study they focus on two-dimensional photonic crystals, i.e., structures with periodic dielectric patterns on a plane and translational symmetry in the perpendicular direction. They start by studying a two-dimensional photonic crystal system for frequencies inside the band gap. The inclusion of a line defect introduces allowed states in the otherwise prohibited frequency spectrum. The dependence of the defect resonance state on different parameters such as size of the structure, profile of incoming source, etc., is investigated in detail. For this study, they used two popular computational methods in photonic crystal research, the Finite Difference Time Domain method (FDTD) and the Transfer Matrix Method (TMM). The results for the one-dimensional defect system are analyzed, and the two methods, FDTD and TMM, are compared. Then, they shift their attention only to periodic two-dimensional crystals, concentrate on their band properties, and study their unusual refractive behavior. Anomalous refractive phenomena in photonic crystals included cases where the beam refracts on the ''wrong'' side of the surface normal. The latter phenomenon, is known as negative refraction and was previously observed in materials where the wave vector, the electric field, and the magnetic field form a left-handed set of vectors. These materials are generally called left-handed materials (LHM) or negative index materials (NIM). They investigated the possibility that the photonic crystal behaves as a LHM, and how this behavior relates
Ma, Q.; Boulet, C.; Tipping, R. H.
2014-01-01
The refinement of the Robert-Bonamy (RB) formalism by considering the line coupling for isotropic Raman Q lines of linear molecules developed in our previous study [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013)] has been extended to infrared P and R lines. In these calculations, the main task is to derive diagonal and off-diagonal matrix elements of the Liouville operator iS1 - S2 introduced in the formalism. When one considers the line coupling for isotropic Raman Q lines where their initial and final rotational quantum numbers are identical, the derivations of off-diagonal elements do not require extra correlation functions of the ^S operator and their Fourier transforms except for those used in deriving diagonal elements. In contrast, the derivations for infrared P and R lines become more difficult because they require a lot of new correlation functions and their Fourier transforms. By introducing two dimensional correlation functions labeled by two tensor ranks and making variable changes to become even functions, the derivations only require the latters' two dimensional Fourier transforms evaluated at two modulation frequencies characterizing the averaged energy gap and the frequency detuning between the two coupled transitions. With the coordinate representation, it is easy to accurately derive these two dimensional correlation functions. Meanwhile, by using the sampling theory one is able to effectively evaluate their two dimensional Fourier transforms. Thus, the obstacles in considering the line coupling for P and R lines have been overcome. Numerical calculations have been carried out for the half-widths of both the isotropic Raman Q lines and the infrared P and R lines of C2H2 broadened by N2. In comparison with values derived from the RB formalism, new calculated values are significantly reduced and become closer to measurements.
Modeling two-dimensional water flow and bromide transport in a heterogeneous lignitic mine soil
Buczko, U.; Gerke, H.H. [Brandenburg University of Technology, Cottbus (Germany)
2006-02-15
Water and solute fluxes in lignitic mine soils and in many other soils are often highly heterogeneous. Here, heterogeneity reflects dumping-induced inclined structures and embedded heterogeneous distributions of sediment mixtures and of lignitic fragments. Such two-scale heterogeneity effects may be analyzed through the application of two-dimensional models for calculating water and solute fluxes. The objective of this study was to gain more insight to what extent spatial heterogeneity of soil hydraulic parameters contributes to preferential flow at a lignitic mine soil. The simulations pertained to the 'Barenbrucker Hohe' site in Germany where previously water fluxes and applied tracers had been monitored with a cell lysimeter, and from where a soil block had been excavated for detailed two-dimensional characterization of the hydraulic parameters using pedotransfer functions. Based on those previous studies, scenarios with different distributions of hydraulic parameters were simulated. The results show that spatial variability of hydraulic parameters alone can hardly explain the observed flow patterns. The observed preferential flow at the site was probably caused by additional factors such as hydrophobicity, the presence of root channels, anisotropy in the hydraulic conductivity, and heterogeneous root distributions. To study the relative importance of these other factors by applying two-dimensional flow models to such sites, the experimental database must be improved. Single-continuum model approaches may be insufficient for such sites.
Electronics based on two-dimensional materials.
Fiori, Gianluca; Bonaccorso, Francesco; Iannaccone, Giuseppe; Palacios, Tomás; Neumaier, Daniel; Seabaugh, Alan; Banerjee, Sanjay K; Colombo, Luigi
2014-10-01
The compelling demand for higher performance and lower power consumption in electronic systems is the main driving force of the electronics industry's quest for devices and/or architectures based on new materials. Here, we provide a review of electronic devices based on two-dimensional materials, outlining their potential as a technological option beyond scaled complementary metal-oxide-semiconductor switches. We focus on the performance limits and advantages of these materials and associated technologies, when exploited for both digital and analog applications, focusing on the main figures of merit needed to meet industry requirements. We also discuss the use of two-dimensional materials as an enabling factor for flexible electronics and provide our perspectives on future developments.
Two-Dimensional NMR Lineshape Analysis
Waudby, Christopher A.; Ramos, Andres; Cabrita, Lisa D.; Christodoulou, John
2016-04-01
NMR titration experiments are a rich source of structural, mechanistic, thermodynamic and kinetic information on biomolecular interactions, which can be extracted through the quantitative analysis of resonance lineshapes. However, applications of such analyses are frequently limited by peak overlap inherent to complex biomolecular systems. Moreover, systematic errors may arise due to the analysis of two-dimensional data using theoretical frameworks developed for one-dimensional experiments. Here we introduce a more accurate and convenient method for the analysis of such data, based on the direct quantum mechanical simulation and fitting of entire two-dimensional experiments, which we implement in a new software tool, TITAN (TITration ANalysis). We expect the approach, which we demonstrate for a variety of protein-protein and protein-ligand interactions, to be particularly useful in providing information on multi-step or multi-component interactions.
A two-dimensional Dirac fermion microscope
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.
A two-dimensional Dirac fermion microscope.
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.
Anisotropic States of Two-Dimensional Electrons in High Magnetic Fields
Ettouhami, A. M.; Doiron, C. B.; Klironomos, F. D.; Côté, R.; Dorsey, Alan T.
2006-05-01
We study the collective states formed by two-dimensional electrons in Landau levels of index n≥2 near half filling. By numerically solving the self-consistent Hartree-Fock (HF) equations for a set of oblique two-dimensional lattices, we find that the stripe state is an anisotropic Wigner crystal (AWC), and determine its precise structure for varying values of the filling factor. Calculating the elastic energy, we find that the shear modulus of the AWC is small but finite (nonzero) within the HF approximation. This implies, in particular, that the long-wavelength magnetophonon mode in the stripe state vanishes like q3/2 as in an ordinary Wigner crystal, and not like q5/2 as was found in previous studies where the energy of shear deformations was neglected.
Two dimensional fermions in four dimensional YM
Narayanan, R
2009-01-01
Dirac fermions in the fundamental representation of SU(N) live on a two dimensional torus flatly embedded in $R^4$. They interact with a four dimensional SU(N) Yang Mills vector potential preserving a global chiral symmetry at finite $N$. As the size of the torus in units of $\\frac{1}{\\Lambda_{SU(N)}}$ is varied from small to large, the chiral symmetry gets spontaneously broken in the infinite $N$ limit.
Two-dimensional Kagome photonic bandgap waveguide
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....
String breaking in two-dimensional QCD
Hornbostel, K J
1999-01-01
I present results of a numerical calculation of the effects of light quark-antiquark pairs on the linear heavy-quark potential in light-cone quantized two-dimensional QCD. I extract the potential from the Q-Qbar component of the ground-state wavefunction, and observe string breaking at the heavy-light meson pair threshold. I briefly comment on the states responsible for the breaking.
Two-dimensional supramolecular electron spin arrays.
Wäckerlin, Christian; Nowakowski, Jan; Liu, Shi-Xia; Jaggi, Michael; Siewert, Dorota; Girovsky, Jan; Shchyrba, Aneliia; Hählen, Tatjana; Kleibert, Armin; Oppeneer, Peter M; Nolting, Frithjof; Decurtins, Silvio; Jung, Thomas A; Ballav, Nirmalya
2013-05-07
A bottom-up approach is introduced to fabricate two-dimensional self-assembled layers of molecular spin-systems containing Mn and Fe ions arranged in a chessboard lattice. We demonstrate that the Mn and Fe spin states can be reversibly operated by their selective response to coordination/decoordination of volatile ligands like ammonia (NH3). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Rubin, P., E-mail: rubin@fi.tartu.ee; Sherman, A.
2014-11-07
The spin-1 Heisenberg model on a triangular lattice with the ferromagnetic nearest-neighbor and antiferromagnetic third-nearest-neighbor exchange interactions, J{sub 1}=−(1−p)J and J{sub 2}=pJ, J>0(0≤p≤1), is studied with the use of the SPINPACK code. This model is applicable for the description of the magnetic properties of NiGa{sub 2}S{sub 4}. The ground, low-lying excited state energies and spin-spin correlation functions have been found for lattices with N=16 and N=20 sites with the periodic boundary conditions. These results are in qualitative agreement with earlier authors' results obtained with Mori's projection operator technique. - Highlights: • The S=1J{sub 1}–J{sub 3} Heisenberg model on a triangular lattice is studied. • The ferromagnetic nearest and AF 3rd-nearest-neighbor couplings are considered. • The exact diagonalization study of finite lattices was done. • The SPINPACK code using Lanczos' method is used for calculations. • The obtained results are in agreement with those obtained by Mori's approach.
Two dimensional echocardiographic detection of intraatrial masses.
DePace, N L; Soulen, R L; Kotler, M N; Mintz, G S
1981-11-01
With two dimensional echocardiography, a left atrial mass was detected in 19 patients. Of these, 10 patients with rheumatic mitral stenosis had a left atrial thrombus. The distinctive two dimensional echocardiographic features of left atrial thrombus included a mass of irregular nonmobile laminated echos within an enlarged atrial cavity, usually with a broad base of attachment to the posterior left atrial wall. Seven patients had a left atrial myxoma. Usually, the myxoma appeared as a mottled ovoid, sharply demarcated mobile mass attached to the interatrial septum. One patient had a right atrial angiosarcoma that appeared as a nonmobile mass extending from the inferior vena caval-right atrial junction into the right atrial cavity. One patient had a left atrial leiomyosarcoma producing a highly mobile mass attached to the lateral wall of the left atrium. M mode echocardiography detected six of the seven myxomas, one thrombus and neither of the other tumors. Thus, two dimensional echocardiography appears to be the technique of choice in the detection, localization and differentiation of intraatrial masses.
Study of cystic artery by arteriography. Importance of previous cholecystography
Machado, G.O.
An oral cholecystography previously to celiac and mesenteric arteriography is performed, in order to identify the cystic artery, in 42 patients with pancreatitis, according Seldinger technique. The cystic artery was identified in all the cases, the pattern being the outlet of the cystic artery from the right hepatic artery. Infusion pump and seriography were not used.
Zhu, Jia; Zhang, Hui; Zhao, Ling; Xiong, Wei; Huang, Xin; Wang, Bin; Zhang, Yongfan
2016-08-01
Periodic density functional theory calculations have been performed to study the electronic properties of bimetallic oxide CrW2O9 clusters adsorbed on MgO/Ag(001) ultrathin films (activities with respect to that of pure W3O9 clusters. As a consequence, present results reveal that the adsorption of bimetallic oxide CrW2O9 clusters on the MgO/Ag(001) ultrathin films provide a new perspective to tune and modify the properties and chemical reactivity of bimetallic oxide adsorbates as a function of the thickness of the oxide films.
Long, Jean-Alexandre; Moreau-Gaudry, Alexandre; Troccaz, Jocelyne; Rambeaud, Jean-Jacques; Descotes, Jean-Luc
2007-01-01
OBJECTIVE: This study evaluated the accuracy in localisation and distribution of real-time three-dimensional (4-D) ultrasound-guided biopsies on a prostate phantom. METHODS: A prostate phantom was created. A three-dimensional real-time ultrasound system with a 5.9MHz probe was used, making it possible to see several reconstructed orthogonal viewing planes in real time. Fourteen operators performed biopsies first under 2-D then 4-D transurethral ultrasound (TRUS) guidance (336 biopsies). The biopsy path was modelled using segmentation in a 3-D ultrasonographic volume. Special software was used to visualise the biopsy paths in a reference prostate and assess the sampled area. A comparative study was performed to examine the accuracy of the entry points and target of the needle. Distribution was assessed by measuring the volume sampled and a redundancy ratio of the sampled prostate. RESULTS: A significant increase in accuracy in hitting the target zone was identified using 4-D ultrasonography as compared to 2-D....
Boriakoff, Valentin
1994-01-01
The goal of this project was the feasibility study of a particular architecture of a digital signal processing machine operating in real time which could do in a pipeline fashion the computation of the fast Fourier transform (FFT) of a time-domain sampled complex digital data stream. The particular architecture makes use of simple identical processors (called inner product processors) in a linear organization called a systolic array. Through computer simulation the new architecture to compute the FFT with systolic arrays was proved to be viable, and computed the FFT correctly and with the predicted particulars of operation. Integrated circuits to compute the operations expected of the vital node of the systolic architecture were proven feasible, and even with a 2 micron VLSI technology can execute the required operations in the required time. Actual construction of the integrated circuits was successful in one variant (fixed point) and unsuccessful in the other (floating point).
Yi, Xin; Gao, Huajian
2014-06-01
A fundamental understanding of cell-nanomaterial interaction is essential for biomedical diagnostics, therapeutics, and nanotoxicity. Here, we perform a theoretical analysis to investigate the phase diagram and morphological evolution of an elastic rod-shaped nanoparticle wrapped by a lipid membrane in two dimensions. We show that there exist five possible wrapping phases based on the stability of full wrapping, partial wrapping, and no wrapping states. The wrapping phases depend on the shape and size of the particle, adhesion energy, membrane tension, and bending rigidity ratio between the particle and membrane. While symmetric morphologies are observed in the early and late stages of wrapping, in between a soft rod-shaped nanoparticle undergoes a dramatic symmetry breaking morphological change while stiff and rigid nanoparticles experience a sharp reorientation. These results are of interest to the study of a range of phenomena including viral budding, exocytosis, as well as endocytosis or phagocytosis of elastic particles into cells.
Isaaz, K; Cloez, J L; Danchin, N; Marçon, F; Worms, A M; Pernot, C
1985-09-15
Evaluation of the right ventricular (RV) outflow tract in congenital heart disease is extremely important for surgical management. Therefore, the value of 2-dimensional echocardiography (2-D echo) to assess the RV outflow tract was studied using a new approach: the subcostal elongated right oblique view. Twenty normal children and 49 children with congenital heart disease, aged 1 day to 11 years, were studied. Significant pulmonary infundibular obstruction was present in 22 patients with conotruncal malformations. To obtain the subcostal elongated right oblique view from the short-axis view at the aortic valve level, the transducer was slightly rotated clockwise with an anterior angulation of about 30 degrees so that the ascending aorta was seen in its long axis, providing an image similar to that obtained by a right ventriculogram in the elongated right anterior oblique view. The deviation of infundibular septum was appreciated by measurement of the angle alpha, defined by the long axis of the infundibular septum and the plane of aortic cusps. This view could be obtained in 64 patients (92%). In correlation with angiographic or anatomic data, the subcostal elongated right oblique view permitted recognition of several types of RV outflow tract: type I--normally formed RV outflow tract; type II--disorganized RV outflow tract with obstruction (alpha less than 90 degrees); type III and IV--disorganized RV outflow tract with obstruction (alpha greater than 90 degrees). This view could visualize the crista supraventricularis in type I, but also the anatomic components of RV outflow tract that may contribute to obstruction in the other types: infundibular septum, septoparietal trabeculations and trabecula septomarginalis.(ABSTRACT TRUNCATED AT 250 WORDS)
Xiao, Zewen; Meng, Weiwei; Wang, Jianbo; Yan, Yanfa
2016-10-07
Recently, solar cells based on 2D (CH3NH3)2Pb(SCN)2I2 perovskite have realized a power conversion efficiency of 3.23%. In this work, we study the defect properties of (CH3NH3)2Pb(SCN)2I2 through density-functional theory calculations. It is found that the lower crystal structure dimensionality of (CH3NH3)2Pb(SCN)2I2 makes the valence band maximum lower and the conduction band minimum higher as compared to its 3D CH3NH3PbI3 perovskite counterpart, resulting in relatively deeper defect transition levels. Our calculated defect formation energies suggest that if the 2D (CH3NH3)2Pb(SCN)2I2 perovskite absorbers are synthesized under Pb-poor and I-rich conditions, the dominant defects should be Pb vacancies, which create shallow levels. The resultant perovskite films are expected to exhibit p-type conductivity with a relatively long carrier lifetime.
Higo, Y.; Ueno, H. [Hiroshima University, Hiroshima (Japan). Faculty of Engineering; Koda, M. [Asahi Glass Co. Ltd., Tokyo (Japan); Nakamori, K. [Nippon Denro MFG. Co. Ltd., Osaka (Japan)
1996-10-01
Analyses and discussions were given on characteristics of loads as a result of seaquake acting on a floating body. In the present study, propagation of pressure waves due to vibration in sea bottom ground as propagation of underwater sound waves, and pressures in wave motion fields and loads due to seaquake acting on the floating body were derived by using the Green function which satisfies free surface conditions and sea bottom conditions. In addition, the boundary element method was used to conduct similar calculations to verify the methodological reasonability. As a result of discussions, the following results were obtained: a seaquake load has a resonant point which corresponds to an intrinsic value of the boundary value problem in a closed region; the resonant point moves according to width of the floating body, and the frequency moves to higher frequency side when water depth is shallower; compressibility of fluid cannot be ignored in the vicinity of the frequency for the resonant point; the seaquake load is proportional to width of a vibrating ground on the sea bottom, and the load in the vertical direction decreases when the center of the floating body is separated from the vibrating ground; a load in the horizontal direction presents no problems in a floating body with a shallow draft; and a moment in the lateral direction may present a larger problem than in the load in the vertical direction. 8 refs., 8 figs.
Kawashima Masatou
2005-01-01
Full Text Available Aims : Three-dimensional reconstruction of intracranial vessels is of interest for evaluation of aneurysms. This study determined diagnostic difference of three-dimensional digital subtraction angiography (3D-DSA, volume-rendering image versus 2D-DSA for evaluating ruptured intracranial aneurysms, particularly focusing on the size of aneurysms as depicted in both images. Settings and Design : Sixty-nine patients underwent 3D-DSA and 2D-DSA. The relative size of an aneurysm, which is the ratio of the maximal diameter of an aneurysm to the diameter of a major vessel, was compared between imaging techniques. In addition, relative sizes of smaller aneurysms (10 mm. Statistical analysis used : For comparison of aneurysm size and location of aneurysm, statistical analysis was performed with the Yates chi square test; statistical significance was set with a P value of less than 0.05. Results: Sixty-three (73.3% of the 86 total aneurysms were bigger when measured with 3D-DSA versus 2D-DSA. When measured with 3D-DSA, 28 (84.8% of the 33 smaller aneurysms were bigger, and 50% of the larger aneurysms were bigger versus measurements of 2D-DSA images ( P P Conclusions : 3D-DSA, especially volume-rendering images, tends to depict ruptured intracranial aneurysms bigger than 2D-DSA. This is particularly true with cerebral aneurysms that are <5 mm in size and are located in the anterior circulation, especially ICA and ACA territories.
Xia, Huihui; Xu, Zhenyu; Kan, Ruifeng; He, Yabai; Liu, Jianguo; Zhang, Guangle
2015-09-01
The principle of gas temperature and concentration measurement based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) is introduced. Combining Computed Tomography (CT) with TDLAS, herein referred to as Tunable Diode Laser Absorption Tomography (TDLAT), reconstructs temperature and concentration distribution which are assumed as Gaussian function or paraboloid function. A pair of water absorption lines (7153.722 cm-1 and 7153.748 cm-1 and 7154.354 cm-1) is selected to measure temperature by means of two-line technique. Radon transform is used to calculate projections of different path for reconstructing temperature distribution based on filtered backprojection algorithm. With a general normalization process, water vapor concentration distribution can be obtained simultaneously. The reconstruction results agree well with the original model. In consideration of laboratory verification and experimental condition, the TDLAT data consist of 13 projection angles and 11 parallel rays at each angle is discussed in this article, obtaining distribution map with a resolution of 20 × 20. Although the reconstruction value of the edge deviates a little from the original parameters, this method achieves relatively satisfactory outcome in general. The reconstruction error roughly increases with decreasing projection angles and parallel rays, additionally, the reconstruction accuracy is more dependent on the parallel ray number at each angle than the projection angle number. Appropriate grid partition is also important in reconstruction study, the optimal grid partition is 30 × 30 or near this magnitude when the system contains totally 18 projection angles and 27 parallel rays at each angle. This work proposes a feasible formula for reconstruction research with a small amount of projections and rays, theoretically, laying a foundation for experimental validation in the future.
Liu, Y J; Leng, X P; Du, G Q; Wang, X D; Tian, J W; Ren, M
2015-02-01
The reperfusion injury that occurs in the early reperfusion often results in myocardial dysfunction. This study evaluated global and regional left ventricular (LV) function using speckle tracking echocardiography (STE) in a rabbit ischemia-reperfusion (I/R) model with and without ischemic postconditioning (I-PostC). The aim is to investigate the potential benefit of I-PostC for myocardial function and validate whether regional longitudinal strain is an appropriate index to indicate myocardial dysfunction. Forty rabbits were divided into an ischemia-reperfusion group (group I) and an I-PostC group (group II). After the coronary arteries were ligated, LV systolic strain and twist parameters decreased, and absolute value of strain rate of isovolumetric relaxation period (SRivr) and post-systolic strain index (PSI) increased significantly in both groups (all pstrain rate (SRsys), systolic strain (Ssys), LV twist and untwisting rate increased, and SRivr and PSI decreased in group II. These changes were not seen in group I. All STE parameters were correlated with area of necrosis (AN)/area at risk (AR) (all p0.8 or 0.6. The sensitivities of GSRsys, GSsys, SRsys, Ssys, and LV twist to detect the myocardial infarction were 81.3%, 62.5%, 87.5%, 93.8% and 81.3%, respectively. And the specificities of those parameters were 75.0%, 81.2%, 75.0%, 87.5% and 68.7%. These results indicate that STE is useful for quantitative detection on myocardial function improvement induced by I-PostC in a rabbit I/R model. The regional index-Ssys is an appropriate parameter to indicate myocardial dysfunction because of its sensitivity, specificity, and repeatability.
Butz, T; van Buuren, F; Mellwig, K P; Langer, C; Plehn, G; Meissner, A; Trappe, H J; Horstkotte, D; Faber, L
2011-01-01
Two-dimensional strain (2DS) is a novel method to measure strain from standard two-dimensional echocardiographic images by speckle tracking, which is less angle dependent and more reproducible than conventional Doppler-derived strain. The objective of our study was to characterize global and regional function abnormalities using 2DS and strain rate analysis in patients (pts) with pathological left ventricular hypertrophy (LVH) caused by non-obstructive hypertrophic cardiomyopathy (HCM), in top level athletes, and in healthy controls. The hypothetical question was, if 2DS might be useful as additional tool in differentiating between pathologic and physiologic hypertrophy in top-level athletes. We consecutively studied 53 subjects, 15 pts with hypertrophic cardiomyopathy (HCM), 20 competitive top-level athletes, and a control group of 18 sedentary normal subjects by standard echocardiography according to ASE guidelines. Global longitudinal strain (GLS) and regional peak systolic strain (PSS) was assessed by 2DS in the apical four-chamber-view using a dedicated software. All components of strain were significantly reduced in pts with HCM (GLS: -8.1 ± 3.8%; P < 0.001) when compared with athletes (-15.2 ± 3.6%) and control subjects (-16.0 ± 2.8%). In general, there was no significant difference between the strain values of the athletes and the control group, but in some of the segments, the strain values of the control group were significantly higher than those in the athletes. A cut-off value of GLS less than -10% for the diagnosis of pathologic hypertrophy (HCM) resulted in a sensitivity of 80.0% and a specificity of 95.0%. The combination of TDI (averaged S', E') and 2DS (GLS) cut-off values for the detection of pathologic LVH in HCM demonstrated a sensitivity of 100%, and a specificity of 95%. Two-dimensional strain is a new simple and rapid method to measure GLS and PSS as components of systolic strain. This technique could offer a unique approach to quantify
On the critical behaviour of two-dimensional liquid crystals
A.l. Fariñas-Sánchez
2010-01-01
Full Text Available The Lebwohl-Lasher (LL model is the traditional model used to describe the nematic-isotropic transition of real liquid crystals. In this paper, we develop a numerical study of the temperature behaviour and of finite-size scaling of the two-dimensional (2D LL-model. We discuss two possible scenarios. In the first one, the 2D LL-model presents a phase transition similar to the topological transition appearing in the 2D XY-model. In the second one, the 2D LL-model does not exhibit any critical transition, but its low temperature behaviour is rather characterized by a crossover from a disordered phase to an ordered phase at zero temperature. We realize and discuss various comparisons with the 2D XY-model and the 2D Heisenberg model. Having added finite-size scaling behaviour of the order parameter and conformal mapping of order parameter profile to previous studies, we analyze the critical scaling of the probability distribution function, hyperscaling relations and stiffness order parameter and conclude that the second scenario (no critical transition is the most plausible.
New study reveals twice as many asteroids as previously believed
2002-05-01
The ISO satellite Credits: ESA ISO An artist's impression of the ISO spacecraft. The ISO Deep Asteroid Search indicates that there are between 1.1 million and 1.9 million 'space rocks' larger than 1 kilometre in diameter in the so-called 'main asteroid belt', about twice as many as previously believed. However, astronomers think it is premature to revise current assessments of the risk of the Earth being hit by an asteroid. Despite being in our own Solar System, asteroids can be more difficult to study than very distant galaxies. With sizes of up to one thousand kilometres in diameter, the brightness of these rocky objects may vary considerably in just a few minutes. They move very quickly with respect to the stars - they have been dubbed 'vermin of the sky' because they often appear as trails on long exposure images. This elusiveness explains why their actual number and size distribution remains uncertain. Most of the almost 40,000 asteroids catalogued so far (1) orbit the Sun forming the 'main asteroid belt', between Mars and Jupiter, too far to pose any threat to Earth. However, space-watchers do keep a closer eye on another category of asteroids, the 'Near Earth Asteroids' or 'NEAs', which are those whose orbits cross, or are likely to cross, that of our planet. The ISO Deep Asteroid Search (IDAS), the first systematic search for these objects performed in infrared light, focused on main belt asteroids. Because it is impossible to simply point the telescope at the whole main belt and count, astronomers choose selected regions of the belt and then use a theoretical model to extrapolate the data to the whole belt. Edward Tedesco (TerraSystems, Inc., New Hampshire, United States) and François-Xavier Desert (Observatoire de Grenoble, France) observed their main belt selected areas in 1996 and 1997 with ESA's ISO. They found that in the middle region of the belt the density of asteroids was 160 asteroids larger than 1 kilometre per square degree - an area of the
Band Gap Engineering of Two-Dimensional Nitrogene
Li, Jie-Sen; Wang, Wei-Liang; Yao, Dao-Xin
2016-01-01
In our previous study, we have predicted the novel two-dimensional honeycomb monolayers of pnictogen. In particular, the structure and properties of the honeycomb monolayer of nitrogen, which we call nitrogene, are very unusual. In this paper, we make an in-depth investigation of its electronic structure. We find that the band structure of nitrogene can be engineered in several ways: controlling the stacking of monolayers, application of biaxial tensile strain, and application of perpendicular electric field. The band gap of nitrogene is found to decrease with the increasing number of layers. The perpendicular electric field can also reduce the band gap when it is larger than 0.18 V/Å, and the gap closes at 0.35 V/Å. A nearly linear dependence of the gap on the electric field is found during the process. Application of biaxial strain can decrease the band gap as well, and eventually closes the gap. After the gap-closing, we find six inequivalent Dirac points in the Brillouin zone under the strain between 17% and 28%, and the nitrogene monolayer becomes a Dirac semimetal. These findings suggest that the electronic structure of nitrogene can be modified by several techniques, which makes it a promising candidate for electronic devices. PMID:27680297
Two-dimensional photonic crystal surfactant detection.
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.
Theory of two-dimensional transformations
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...
Sums of two-dimensional spectral triples
Christensen, Erik; Ivan, Cristina
2007-01-01
construct a sum of two dimensional modules which reflects some aspects of the topological dimensions of the compact metric space, but this will only give the metric back approximately. At the end we make an explicit computation of the last module for the unit interval in. The metric is recovered exactly......, the Dixmier trace induces a multiple of the Lebesgue integral but the growth of the number of eigenvalues is different from the one found for the standard differential operator on the unit interval....
Binding energy of two-dimensional biexcitons
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....
Dynamics of film. [two dimensional continua theory
Zak, M.
1979-01-01
The general theory of films as two-dimensional continua are elaborated upon. As physical realizations of such a model this paper examines: inextensible films, elastic films, and nets. The suggested dynamic equations have enabled us to find out the characteristic speeds of wave propagation of the invariants of external and internal geometry and formulate the criteria of instability of their shape. Also included herein is a detailed account of the equation describing the film motions beyond the limits of the shape stability accompanied by the formation of wrinkles. The theory is illustrated by examples.
Two-dimensional motion of unstable steps induced by flow in solution
Sato, Masahide
2011-01-01
By carrying out Monte Carlo simulation, we study step instabilities during crystal growth from solution. In previous studies [M. Sato. J. Phys. Soc. Jpn. 79 (2010) 064606; M. Sato, J. Cryst. Growth 318 (2011) 5; M. Sato. J. Phys. Soc. Jpn. 80 (2011) 024604], we used a one-dimensional model, so that we were unable to study another type of instability, step wandering. In this research, we use a two-dimensional model to study both step wandering and step bunching. When the flow of solutes is in ...
Two-dimensional gauge theoretic supergravities
Cangemi, D.; Leblanc, M.
1994-05-01
We investigate two-dimensional supergravity theories, which can be built from a topological and gauge invariant action defined on an ordinary surface. One is the N = 1 supersymmetric extension of the Jackiw-Teitelboim model presented by Chamseddine in a superspace formalism. We complement the proof of Montano, Aoaki and Sonnenschein that this extension is topological and gauge invariant, based on the graded de Sitter algebra. Not only do the equations of motion correspond to the supergravity ones and do gauge transformations encompass local supersymmetries, but we also identify the ∫-theory with the superfield formalism action written by Chamseddine. Next, we show that the N = 1 supersymmetric extension of string-inspired two-dimensional dilaton gravity put forward by Park and Strominger cannot be written as a ∫-theory. As an alternative, we propose two topological and gauge theories that are based on a graded extension of the extended Poincaré algebra and satisfy a vanishing-curvature condition. Both models are supersymmetric extensions of the string-inspired dilaton gravity.
Two-Dimensional Theory of Scientific Representation
A Yaghmaie
2013-03-01
Full Text Available Scientific representation is an interesting topic for philosophers of science, many of whom have recently explored it from different points of view. There are currently two competing approaches to the issue: cognitive and non-cognitive, and each of them claims its own merits over the other. This article tries to provide a hybrid theory of scientific representation, called Two-Dimensional Theory of Scientific Representation, which has the merits of the two accounts and is free of their shortcomings. To do this, we will argue that although scientific representation needs to use the notion of intentionality, such a notion is defined and realized in a simply structural form contrary to what cognitive approach says about intentionality. After a short introduction, the second part of the paper is devoted to introducing theories of scientific representation briefly. In the third part, the structural accounts of representation will be criticized. The next step is to introduce the two-dimensional theory which involves two key components: fixing and structural fitness. It will be argued that fitness is an objective and non-intentional relation, while fixing is intentional.
Two-dimensional shape memory graphene oxide
Chang, Zhenyue; Deng, Junkai; Chandrakumara, Ganaka G.; Yan, Wenyi; Liu, Jefferson Zhe
2016-06-01
Driven by the increasing demand for micro-/nano-technologies, stimuli-responsive shape memory materials at nanoscale have recently attracted great research interests. However, by reducing the size of conventional shape memory materials down to approximately nanometre range, the shape memory effect diminishes. Here, using density functional theory calculations, we report the discovery of a shape memory effect in a two-dimensional atomically thin graphene oxide crystal with ordered epoxy groups, namely C8O. A maximum recoverable strain of 14.5% is achieved as a result of reversible phase transition between two intrinsically stable phases. Our calculations conclude co-existence of the two stable phases in a coherent crystal lattice, giving rise to the possibility of constructing multiple temporary shapes in a single material, thus, enabling highly desirable programmability. With an atomic thickness, excellent shape memory mechanical properties and electric field stimulus, the discovery of a two-dimensional shape memory graphene oxide opens a path for the development of exceptional micro-/nano-electromechanical devices.
Zero- n bar band gap in two-dimensional metamaterial photonic crystals
Mejía-Salazar, J. R.; Porras-Montenegro, N.
2015-04-01
We have theoretically studied metamaterial photonic crystals (PCs) composed by air and double negative (DNG) material. Numerical data were obtained by means of the finite difference time-domain (FDTD) method, with results indicating the possibility for the existence of the zero- n bar non-Bragg gap in two-dimensional metamaterial PCs, which has been previously observed only in one-dimensional photonic superlattices. Validity of the present FDTD algorithm for the study of one-dimensional metamaterial PCs is shown by comparing with results for the transmittance spectra obtained by means of the well known transfer matrix method (TMM). In the case of two-dimensional metamaterial PCs, we have calculated the photonic band structure (PBS) in the limiting case of a one-dimensional photonic superlattice and for a nearly one-dimensional PC, showing a very similar dispersion relation. Finally, we show that due to the strong electromagnetic field localization on the constitutive rods, the zero- n bar non-Bragg gap may only exist in two-dimensional systems under strict geometrical conditions.
Dynamics of kinks in one- and two-dimensional hyperbolic models with quasidiscrete nonlinearities.
Rotstein, H G; Mitkov, I; Zhabotinsky, A M; Epstein, I R
2001-06-01
We study the evolution of fronts in the Klein-Gordon equation when the nonlinear term is inhomogeneous. Extending previous works on homogeneous nonlinear terms, we describe the derivation of an equation governing the front motion, which is strongly nonlinear, and, for the two-dimensional case, generalizes the damped Born-Infeld equation. We study the motion of one- and two-dimensional fronts finding a much richer dynamics than in the homogeneous system case, leading, in most cases, to the stabilization of one phase inside the other. For a one-dimensional front, the function describing the inhomogeneity of the nonlinear term acts as a "potential function" for the motion of the front, i.e., a front initially placed between two of its local maxima asymptotically approaches the intervening minimum. Two-dimensional fronts, with radial symmetry and without dissipation can either shrink to a point in finite time, grow unboundedly, or their radius can oscillate, depending on the initial conditions. When dissipation effects are present, the oscillations either decay spirally or not depending on the value of the damping dissipation parameter. For fronts with a more general shape, we present numerical simulations showing the same behavior.
XU Quan; TIAN Qiang
2007-01-01
Two-dimensional compact-like discrete breathers in discrete two-dimensional monatomic square lattices are investigated by discussing a generafized discrete two-dimensional monatomic model.It is proven that the twodimensional compact-like discrete breathers exist not only in two-dimensional soft Ф4 potentials but also in hard two-dimensional Ф4 potentials and pure two-dimensional K4 lattices.The measurements of the two-dimensional compact-like discrete breather cores in soft and hard two-dimensional Ф4 potential are determined by coupling parameter K4,while those in pure two-dimensional K4 lattices have no coupling with parameter K4.The stabilities of the two-dimensional compact-like discrete breathers correlate closely to the coupling parameter K4 and the boundary condition of lattices.
The Persistence Problem in Two-Dimensional Fluid Turbulence
Perlekar, Prasad; Mitra, Dhrubaditya; Pandit, Rahul
2010-01-01
We present a natural framework for studying the persistence problem in two-dimensional fluid turbulence by using the Okubo-Weiss parameter {\\Lambda} to distinguish between vortical and extensional regions. We then use a direct numerical simulation (DNS) of the two-dimensional, incompressible Navier-Stokes equation with Ekman friction to study probability distribution functions (PDFs) of the persistence times of vortical and extensional regions by employing both Eulerian and Lagrangian measurements. We find that, in the Eulerian case, the persistence-time PDFs have exponential tails; by contrast, this PDF for Lagrangian particles, in vortical regions, has a power-law tail with a universal exponent {\\theta} = 3.1 \\pm 0.2.
Statistical mechanics of two-dimensional and geophysical flows
Bouchet, Freddy
2011-01-01
The theoretical study of the self-organization of two-dimensional and geophysical turbulent flows is addressed based on statistical mechanics methods. This review is a self-contained presentation of classical and recent works on this subject; from the statistical mechanics basis of the theory up to applications to Jupiter's troposphere and ocean vortices and jets. Emphasize has been placed on examples with available analytical treatment in order to favor better understanding of the physics and dynamics. The equilibrium microcanonical measure is built from the Liouville theorem. On this theoretical basis, we predict the output of the long time evolution of complex turbulent flows as statistical equilibria. This is applied to make quantitative models of two-dimensional turbulence, the Great Red Spot and other Jovian vortices, ocean jets like the Gulf-Stream, and ocean vortices. We also present recent results for non-equilibrium situations, for the studies of either the relaxation towards equilibrium or non-equi...
Lyapunov Computational Method for Two-Dimensional Boussinesq Equation
Mabrouk, Anouar Ben
2010-01-01
A numerical method is developed leading to Lyapunov operators to approximate the solution of two-dimensional Boussinesq equation. It consists of an order reduction method and a finite difference discretization. It is proved to be uniquely solvable and analyzed for local truncation error for consistency. The stability is checked by using Lyapunov criterion and the convergence is studied. Some numerical implementations are provided at the end of the paper to validate the theoretical results.
Complex dynamical invariants for two-dimensional complex potentials
J S Virdi; F Chand; C N Kumar; S C Mishra
2012-08-01
Complex dynamical invariants are searched out for two-dimensional complex potentials using rationalization method within the framework of an extended complex phase space characterized by $x = x_{1} + ip_{3}. y = x_{2} + ip_{4}, p_{x} = p_{1} + ix_{3}, p_{y} = p_{2} + ix_{4}$. It is found that the cubic oscillator and shifted harmonic oscillator admit quadratic complex invariants. THe obtained invariants may be useful for studying non-Hermitian Hamiltonian systems.
Chronology Protection in Two-Dimensional Dilaton Gravity
Mishima, T; Mishima, Takashi; Nakamichi, Akika
1994-01-01
The global structure of 1 + 1 dimensional compact Universe is studied in two-dimensional model of dilaton gravity. First we give a classical solution corresponding to the spacetime in which a closed time-like curve appears, and show the instability of this spacetime due to the existence of matters. We also observe quantum version of such a spacetime having closed timelike curves never reappear unless the parameters are fine-tuned.
Phase Transitions in Two-Dimensional Traffic Flow Models
Cuesta, J A; Molera, J M; Cuesta, José A; Martinez, Froilán C; Molera, Juan M
1993-01-01
Abstract: We introduce two simple two-dimensional lattice models to study traffic flow in cities. We have found that a few basic elements give rise to the characteristic phase diagram of a first-order phase transition from a freely moving phase to a jammed state, with a critical point. The jammed phase presents new transitions corresponding to structural transformations of the jam. We discuss their relevance in the infinite size limit.
Phase Transitions in Two-Dimensional Traffic Flow Models
Cuesta, José A; Molera, Juan M; Escuela, Angel Sánchez; 10.1103/PhysRevE.48.R4175
2009-01-01
We introduce two simple two-dimensional lattice models to study traffic flow in cities. We have found that a few basic elements give rise to the characteristic phase diagram of a first-order phase transition from a freely moving phase to a jammed state, with a critical point. The jammed phase presents new transitions corresponding to structural transformations of the jam. We discuss their relevance in the infinite size limit.
Thermal diode from two-dimensional asymmetrical Ising lattices.
Wang, Lei; Li, Baowen
2011-06-01
Two-dimensional asymmetrical Ising models consisting of two weakly coupled dissimilar segments, coupled to heat baths with different temperatures at the two ends, are studied by Monte Carlo simulations. The heat rectifying effect, namely asymmetric heat conduction, is clearly observed. The underlying mechanisms are the different temperature dependencies of thermal conductivity κ at two dissimilar segments and the match (mismatch) of flipping frequencies of the interface spins.
Interior design of a two-dimensional semiclassic black hole
Levanony, Dana; 10.1103/PhysRevD.80.084008
2009-01-01
We look into the inner structure of a two-dimensional dilatonic evaporating black hole. We establish and employ the homogenous approximation for the black-hole interior. The field equations admit two types of singularities, and their local asymptotic structure is investigated. One of these singularities is found to develop, as a spacelike singularity, inside the black hole. We then study the internal structure of the evaporating black hole from the horizon to the singularity.
Velocity Statistics in the Two-Dimensional Granular Turbulence
Isobe, Masaharu
2003-01-01
We studied the macroscopic statistical properties on the freely evolving quasi-elastic hard disk (granular) system by performing a large-scale (up to a few million particles) event-driven molecular dynamics systematically and found that remarkably analogous to an enstrophy cascade process in the decaying two-dimensional fluid turbulence. There are four typical stages in the freely evolving inelastic hard disk system, which are homogeneous, shearing (vortex), clustering and final state. In the...
Topological defect motifs in two-dimensional Coulomb clusters
Radzvilavičius, A; 10.1088/0953-8984/23/38/385301
2012-01-01
The most energetically favourable arrangement of low-density electrons in an infinite two-dimensional plane is the ordered triangular Wigner lattice. However, in most instances of contemporary interest one deals instead with finite clusters of strongly interacting particles localized in potential traps, for example, in complex plasmas. In the current contribution we study distribution of topological defects in two-dimensional Coulomb clusters with parabolic lateral confinement. The minima hopping algorithm based on molecular dynamics is used to efficiently locate the ground- and low-energy metastable states, and their structure is analyzed by means of the Delaunay triangulation. The size, structure and distribution of geometry-induced lattice imperfections strongly depends on the system size and the energetic state. Besides isolated disclinations and dislocations, classification of defect motifs includes defect compounds --- grain boundaries, rosette defects, vacancies and interstitial particles. Proliferatio...
On Dirichlet eigenvectors for neutral two-dimensional Markov chains
Champagnat, Nicolas; Miclo, Laurent
2012-01-01
We consider a general class of discrete, two-dimensional Markov chains modeling the dynamics of a population with two types, without mutation or immigration, and neutral in the sense that type has no influence on each individual's birth or death parameters. We prove that all the eigenvectors of the corresponding transition matrix or infinitesimal generator \\Pi\\ can be expressed as the product of "universal" polynomials of two variables, depending on each type's size but not on the specific transitions of the dynamics, and functions depending only on the total population size. These eigenvectors appear to be Dirichlet eigenvectors for \\Pi\\ on the complement of triangular subdomains, and as a consequence the corresponding eigenvalues are ordered in a specific way. As an application, we study the quasistationary behavior of finite, nearly neutral, two-dimensional Markov chains, absorbed in the sense that 0 is an absorbing state for each component of the process.
Extension of modified power method to two-dimensional problems
Zhang, Peng; Lee, Hyunsuk; Lee, Deokjung
2016-09-01
In this study, the generalized modified power method was extended to two-dimensional problems. A direct application of the method to two-dimensional problems was shown to be unstable when the number of requested eigenmodes is larger than a certain problem dependent number. The root cause of this instability has been identified as the degeneracy of the transfer matrix. In order to resolve this instability, the number of sub-regions for the transfer matrix was increased to be larger than the number of requested eigenmodes; and a new transfer matrix was introduced accordingly which can be calculated by the least square method. The stability of the new method has been successfully demonstrated with a neutron diffusion eigenvalue problem and the 2D C5G7 benchmark problem.
Transport behavior of water molecules through two-dimensional nanopores
Zhu, Chongqin; Li, Hui; Meng, Sheng, E-mail: smeng@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)
2014-11-14
Water transport through a two-dimensional nanoporous membrane has attracted increasing attention in recent years thanks to great demands in water purification and desalination applications. However, few studies have been reported on the microscopic mechanisms of water transport through structured nanopores, especially at the atomistic scale. Here we investigate the microstructure of water flow through two-dimensional model graphene membrane containing a variety of nanopores of different size by using molecular dynamics simulations. Our results clearly indicate that the continuum flow transits to discrete molecular flow patterns with decreasing pore sizes. While for pores with a diameter ≥15 Å water flux exhibits a linear dependence on the pore area, a nonlinear relationship between water flux and pore area has been identified for smaller pores. We attribute this deviation from linear behavior to the presence of discrete water flow, which is strongly influenced by the water-membrane interaction and hydrogen bonding between water molecules.
Transport behavior of water molecules through two-dimensional nanopores
Zhu, Chongqin; Li, Hui; Meng, Sheng
2014-11-01
Water transport through a two-dimensional nanoporous membrane has attracted increasing attention in recent years thanks to great demands in water purification and desalination applications. However, few studies have been reported on the microscopic mechanisms of water transport through structured nanopores, especially at the atomistic scale. Here we investigate the microstructure of water flow through two-dimensional model graphene membrane containing a variety of nanopores of different size by using molecular dynamics simulations. Our results clearly indicate that the continuum flow transits to discrete molecular flow patterns with decreasing pore sizes. While for pores with a diameter ≥15 Å water flux exhibits a linear dependence on the pore area, a nonlinear relationship between water flux and pore area has been identified for smaller pores. We attribute this deviation from linear behavior to the presence of discrete water flow, which is strongly influenced by the water-membrane interaction and hydrogen bonding between water molecules.
Thermodynamics of two-dimensional Yukawa systems across coupling regimes
Kryuchkov, Nikita P.; Khrapak, Sergey A.; Yurchenko, Stanislav O.
2017-04-01
Thermodynamics of two-dimensional Yukawa (screened Coulomb or Debye-Hückel) systems is studied systematically using molecular dynamics (MD) simulations. Simulations cover very broad parameter range spanning from weakly coupled gaseous states to strongly coupled fluid and crystalline states. Important thermodynamic quantities, such as internal energy and pressure, are obtained and accurate physically motivated fits are proposed. This allows us to put forward simple practical expressions to describe thermodynamic properties of two-dimensional Yukawa systems. For crystals, in addition to numerical simulations, the recently developed shortest-graph interpolation method is applied to describe pair correlations and hence thermodynamic properties. It is shown that the finite-temperature effects can be accounted for by using simple correction of peaks in the pair correlation function. The corresponding correction coefficients are evaluated using MD simulation. The relevance of the obtained results in the context of colloidal systems, complex (dusty) plasmas, and ions absorbed to interfaces in electrolytes is pointed out.
Phase separation under two-dimensional Poiseuille flow.
Kiwata, H
2001-05-01
The spinodal decomposition of a two-dimensional binary fluid under Poiseuille flow is studied by numerical simulation. We investigated time dependence of domain sizes in directions parallel and perpendicular to the flow. In an effective region of the flow, the power-law growth of a characteristic length in the direction parallel to the flow changes from the diffusive regime with the growth exponent alpha=1/3 to a new regime. The scaling invariance of the growth in the perpendicular direction is destroyed after the diffusive regime. A recurrent prevalence of thick and thin domains which determines log-time periodic oscillations has not been observed in our model. The growth exponents in the infinite system under two-dimensional Poiseuille flow are obtained by the renormalization group.
Two-dimensional localized structures in harmonically forced oscillatory systems
Ma, Y.-P.; Knobloch, E.
2016-12-01
Two-dimensional spatially localized structures in the complex Ginzburg-Landau equation with 1:1 resonance are studied near the simultaneous presence of a steady front between two spatially homogeneous equilibria and a supercritical Turing bifurcation on one of them. The bifurcation structures of steady circular fronts and localized target patterns are computed in the Turing-stable and Turing-unstable regimes. In particular, localized target patterns grow along the solution branch via ring insertion at the core in a process reminiscent of defect-mediated snaking in one spatial dimension. Stability of axisymmetric solutions on these branches with respect to axisymmetric and nonaxisymmetric perturbations is determined, and parameter regimes with stable axisymmetric oscillons are identified. Direct numerical simulations reveal novel depinning dynamics of localized target patterns in the radial direction, and of circular and planar localized hexagonal patterns in the fully two-dimensional system.
Optimal excitation of two dimensional Holmboe instabilities
Constantinou, Navid C
2010-01-01
Highly stratified shear layers are rendered unstable even at high stratifications by Holmboe instabilities when the density stratification is concentrated in a small region of the shear layer. These instabilities may cause mixing in highly stratified environments. However these instabilities occur in tongues for a limited range of parameters. We perform Generalized Stability analysis of the two dimensional perturbation dynamics of an inviscid Boussinesq stratified shear layer and show that Holmboe instabilities at high Richardson numbers can be excited by their adjoints at amplitudes that are orders of magnitude larger than by introducing initially the unstable mode itself. We also determine the optimal growth that obtains for parameters for which there is no instability. We find that there is potential for large transient growth regardless of whether the background flow is exponentially stable or not and that the characteristic structure of the Holmboe instability asymptotically emerges for parameter values ...
Probabilistic Universality in two-dimensional Dynamics
Lyubich, Mikhail
2011-01-01
In this paper we continue to explore infinitely renormalizable H\\'enon maps with small Jacobian. It was shown in [CLM] that contrary to the one-dimensional intuition, the Cantor attractor of such a map is non-rigid and the conjugacy with the one-dimensional Cantor attractor is at most 1/2-H\\"older. Another formulation of this phenomenon is that the scaling structure of the H\\'enon Cantor attractor differs from its one-dimensional counterpart. However, in this paper we prove that the weight assigned by the canonical invariant measure to these bad spots tends to zero on microscopic scales. This phenomenon is called {\\it Probabilistic Universality}. It implies, in particular, that the Hausdorff dimension of the canonical measure is universal. In this way, universality and rigidity phenomena of one-dimensional dynamics assume a probabilistic nature in the two-dimensional world.
Two-dimensional heterostructures for energy storage
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.
Rationally synthesized two-dimensional polymers.
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.
Local doping of two-dimensional materials
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.
Two-dimensional fourier transform spectrometer
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.
Two-dimensional fourier transform spectrometer
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.
FACE RECOGNITION USING TWO DIMENSIONAL LAPLACIAN EIGENMAP
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.
Equivalency of two-dimensional algebras
Santos, Gildemar Carneiro dos; Pomponet Filho, Balbino Jose S. [Universidade Federal da Bahia (UFBA), BA (Brazil). Inst. de Fisica
2011-07-01
Full text: Let us consider a vector z = xi + yj over the field of real numbers, whose basis (i,j) satisfy a given algebra. Any property of this algebra will be reflected in any function of z, so we can state that the knowledge of the properties of an algebra leads to more general conclusions than the knowledge of the properties of a function. However structural properties of an algebra do not change when this algebra suffers a linear transformation, though the structural constants defining this algebra do change. We say that two algebras are equivalent to each other whenever they are related by a linear transformation. In this case, we have found that some relations between the structural constants are sufficient to recognize whether or not an algebra is equivalent to another. In spite that the basis transform linearly, the structural constants change like a third order tensor, but some combinations of these tensors result in a linear transformation, allowing to write the entries of the transformation matrix as function of the structural constants. Eventually, a systematic way to find the transformation matrix between these equivalent algebras is obtained. In this sense, we have performed the thorough classification of associative commutative two-dimensional algebras, and find that even non-division algebra may be helpful in solving non-linear dynamic systems. The Mandelbrot set was used to have a pictorial view of each algebra, since equivalent algebras result in the same pattern. Presently we have succeeded in classifying some non-associative two-dimensional algebras, a task more difficult than for associative one. (author)
Surface Plasmon Polaritons of Two-Dimensional Three-Order Dendritic Structures
王敏凤; 周鲁卫
2011-01-01
We study surface plasmon polaritons excited on two-dimensional three-order dendritic structures. Previous studies show that split ring resonators （SRRs） can be used to obtain magnetic resonance, thus sustairdng surface waves behaving like surface plasmon polaritons （SPPs）. In this paper, we obtain detailed results on surface plasmon polaritons of several different grating structures and theoretically prove that this kind of structures can sustain SPPs. Besides, since dendritic structures can be fabricated by double template-assisted electrochemical deposition, it is worth noting that fabrication of SPP-based materials might be much easier.
A two-dimensional analytical model of petroleum vapor intrusion
Yao, Yijun; Verginelli, Iason; Suuberg, Eric M.
2016-02-01
In this study we present an analytical solution of a two-dimensional petroleum vapor intrusion model, which incorporates a steady-state diffusion-dominated vapor transport in a homogeneous soil and piecewise first-order aerobic biodegradation limited by oxygen availability. This new model can help practitioners to easily generate two-dimensional soil gas concentration profiles for both hydrocarbons and oxygen and estimate hydrocarbon indoor air concentrations as a function of site-specific conditions such as source strength and depth, reaction rate constant, soil characteristics and building features. The soil gas concentration profiles generated by this new model are shown in good agreement with three-dimensional numerical simulations and two-dimensional measured soil gas data from a field study. This implies that for cases involving diffusion dominated soil gas transport, steady state conditions and homogenous source and soil, this analytical model can be used as a fast and easy-to-use risk screening tool by replicating the results of 3-D numerical simulations but with much less computational effort.
Two-Dimensional Identification of Fetal Tooth Germs.
Seabra, Mariana; Vaz, Paula; Valente, Francisco; Braga, Ana; Felino, António
2017-03-01
To demonstrate the efficiency and applicability of two-dimensional ultrasonography in the identification of tooth germs and in the assessment of potential pathology. Observational, descriptive, cross-sectional study. Prenatal Diagnosis Unit of Centro Hospitalar de Vila Nova de Gaia / Espinho-Empresa Pública in Portugal. A total of 157 white pregnant women (median age, 32 years; range, 14 to 47 years) undergoing routine ultrasound exams. Description of the fetal tooth germs, as visualized by two-dimensional ultrasonography, including results from prior fetal biometry and detailed screening for malformations. In the first trimester group, ultrasonography identified 10 tooth germs in the maxilla and 10 tooth germs in the mandible in all fetuses except for one who presented eight maxillary tooth germs. This case was associated with a chromosomal abnormality (trisomy 13) with a bilateral cleft palate. In the second and third trimesters group, ultrasonography identified a larger range of tooth germs: 81.2% of fetuses showed 10 tooth germs in the maxilla and 85.0% of fetuses had 10 tooth germs in the mandible. Hypodontia was more prevalent in the maxilla than in the mandible, which led us to use qualitative two-dimensional ultrasonography to analyze the possible association between hypodontia and other variables such as fetal pathology, markers, head, nuchal, face, and spine. We recommend using this method as the first exam to evaluate fetal morphology and also to help establish accurate diagnosis of abnormalities in pregnancy.
Commensurability oscillations in a two-dimensional lateral superlattice
Davies, John; Long, Andrew; Grant, David; Chowdhury, Suja
2000-03-01
We have calculated and measured conduction in a two-dimensional electron gas subject to a weak two-dimensional periodic potential and a normal magnetic field. Simulations with a potential Vx \\cos(2π x/a) + Vy \\cos(2π y/a) show the usual commensurability oscillations in ρ_xx(B) with Vx alone. The introduction of Vy suppresses these oscillations, rather than introducing the additional oscillations in ρ_yy(B) expected from previous perturbation theories. We explain this in terms of drift of the guiding center of cyclotron motion along contours of an effective potential: open orbits of the guiding center contribute to conduction but closed orbits do not. All orbits are closed in a symmetric superlattice with |V_x| = |V_y| and commensurability oscillations are therefore quenched. Experiments on etched superlattices confirm this picture. Conventional lattice-matched samples give a symmetric potential and weak oscillations; the symmetry is broken by the piezoelectric effect in stressed samples, leading to strong oscillations. Periodic modulation of the magnetic field can be treated in the same way, which explains previous experimental results.
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.
Two-Dimensional Wang-Landau Sampling of AN Asymmetric Ising Model
Tsai, Shan-Ho; Wang, Fugao; Landau, D. P.
We study the critical endpoint behavior of an asymmetric Ising model with two- and three-body interactions on a triangular lattice, in the presence of an external field. We use a two-dimensional Wang-Landau sampling method to determine the density of states for this model. An accurate density of states allowed us to map out the phase diagram accurately and observe a clear divergence of the curvature of the spectator phase boundary and of the derivative of the magnetization coexistence diameter near the critical endpoint, in agreement with previous theoretical predictions.
On numerical evaluation of two-dimensional phase integrals
Lessow, H.; Rusch, W.; Schjær-Jacobsen, Hans
1975-01-01
The relative advantages of several common numerical integration algorithms used in computing two-dimensional phase integrals are evaluated.......The relative advantages of several common numerical integration algorithms used in computing two-dimensional phase integrals are evaluated....
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
Unger, Miriam; Siesler, Heinz W
2009-12-01
In the present study, the orientation of a poly(3-hydroxybutyrate) (PHB)/poly(epsilon-caprolactone) (PCL) blend was monitored during uniaxial elongation by rheo-optical Fourier transform infrared (FT-IR) spectroscopy and analyzed by generalized two-dimensional correlation spectroscopy (2D-COS). The dichroism of the delta(CH(2)) absorption bands of PHB and PCL was employed to determine the polymer chain orientation in the PHB/PCL blend during the elongation up to 267% strain. From the PHB and PCL specific orientation functions it was derived that the PCL chains orient into the drawing direction while the PHB chains orient predominantly perpendicular to the applied strain. To extract more detailed information about the polymer orientation during uniaxial elongation, 2D-COS analysis was employed for the dichroic difference of the polarization spectra recorded during the drawing process. In the corresponding synchronous and asynchronous 2D correlation plots, absorption bands characteristic of the crystalline and amorphous regions of PHB and PCL were separated. Furthermore, the 2D-COS analysis revealed that during the mechanical treatment the PCL domains orient before the PHB domains.
Two-dimensional hexagonal semiconductors beyond graphene
Nguyen, Bich Ha; Hieu Nguyen, Van
2016-12-01
The rapid and successful development of the research on graphene and graphene-based nanostructures has been substantially enlarged to include many other two-dimensional hexagonal semiconductors (THS): phosphorene, silicene, germanene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDCs) such as MoS2, MoSe2, WS2, WSe2 as well as the van der Waals heterostructures of various THSs (including graphene). The present article is a review of recent works on THSs beyond graphene and van der Waals heterostructures composed of different pairs of all THSs. One among the priorities of new THSs compared to graphene is the presence of a non-vanishing energy bandgap which opened up the ability to fabricate a large number of electronic, optoelectronic and photonic devices on the basis of these new materials and their van der Waals heterostructures. Moreover, a significant progress in the research on TMDCs was the discovery of valley degree of freedom. The results of research on valley degree of freedom and the development of a new technology based on valley degree of freedom-valleytronics are also presented. Thus the scientific contents of the basic research and practical applications os THSs are very rich and extremely promising.
Two-dimensional topological photonic systems
Sun, Xiao-Chen; He, Cheng; Liu, Xiao-Ping; Lu, Ming-Hui; Zhu, Shi-Ning; Chen, Yan-Feng
2017-09-01
The topological phase of matter, originally proposed and first demonstrated in fermionic electronic systems, has drawn considerable research attention in the past decades due to its robust transport of edge states and its potential with respect to future quantum information, communication, and computation. Recently, searching for such a unique material phase in bosonic systems has become a hot research topic worldwide. So far, many bosonic topological models and methods for realizing them have been discovered in photonic systems, acoustic systems, mechanical systems, etc. These discoveries have certainly yielded vast opportunities in designing material phases and related properties in the topological domain. In this review, we first focus on some of the representative photonic topological models and employ the underlying Dirac model to analyze the edge states and geometric phase. On the basis of these models, three common types of two-dimensional topological photonic systems are discussed: 1) photonic quantum Hall effect with broken time-reversal symmetry; 2) photonic topological insulator and the associated pseudo-time-reversal symmetry-protected mechanism; 3) time/space periodically modulated photonic Floquet topological insulator. Finally, we provide a summary and extension of this emerging field, including a brief introduction to the Weyl point in three-dimensional systems.
Photodetectors based on two dimensional materials
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.
Asymptotics for Two-dimensional Atoms
Nam, Phan Thanh; Portmann, Fabian; Solovej, Jan Philip
2012-01-01
We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E^{\\TF}(\\lambd......We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E......^{\\TF}(\\lambda)$ is given by a Thomas-Fermi type variational problem and $c^{\\rm H}\\approx -2.2339$ is an explicit constant. We also show that the radius of a two-dimensional neutral atom is unbounded when $Z\\to \\infty$, which is contrary to the expected behavior of three-dimensional atoms....
Vibrational wave packet induced oscillations in two-dimensional electronic spectra. I. Experiments
Nemeth, Alexandra; Mancal, Tomas; Lukes, Vladimir; Hauer, Juergen; Kauffmann, Harald F; Sperling, Jaroslaw
2010-01-01
This is the first in a series of two papers investigating the effect of electron-phonon coupling in two-dimensional Fourier transformed electronic spectroscopy. We present a series of one- and two-dimensional nonlinear spectroscopic techniques for studying a dye molecule in solution. Ultrafast laser pulse excitation of an electronic transition coupled to vibrational modes induces a propagating vibrational wave packet that manifests itself in oscillating signal intensities and line-shapes. For the two-dimensional electronic spectra we can attribute the observed modulations to periodic enhancement and decrement of the relative amplitudes of rephasing and non-rephasing contributions to the total response. Different metrics of the two-dimensional signals are shown to relate to the frequency-frequency correlation function which provides the connection between experimentally accessible observations and the underlying microscopic molecular dynamics. A detailed theory of the time-dependent two-dimensional spectral li...
Electronic Transmission Properties of Two-Dimensional Quasi-Lattice
侯志林; 傅秀军; 刘有延
2002-01-01
In the framework of the tight binding model, the electronic transmission properties of two-dimensional Penrose lattices with free boundary conditions are studied using the generalized eigenfunction method (Phys. Rev. B 60(1999)13444). The electronic transmission coefficients for Penrose lattices with different sizes and widths are calculated, and the result shows strong energy dependence because of the quasiperiodic structure and quantum coherent effect. Around the Fermi level E = 0, there is an energy region with zero transmission amplitudes,which suggests that the studied systems are insulating. The spatial distributions of several typical electronic states with different transmission coefficients are plotted to display the propagation process.
Two-dimensional conformal field theory and the butterfly effect
Roberts, Daniel A
2014-01-01
We study chaotic dynamics in two-dimensional conformal field theory through out-of-time order thermal correlators of the form $\\langle W(t)VW(t)V\\rangle$. We reproduce bulk calculations similar to those of [1], by studying the large $c$ Virasoro identity block. The contribution of this block to the above correlation function begins to decrease exponentially after a delay of $\\sim t_* - \\frac{\\beta}{2\\pi}\\log \\beta^2E_w E_v$, where $t_*$ is the scrambling time $\\frac{\\beta}{2\\pi}\\log c$, and $E_w,E_v$ are the energy scales of the $W,V$ operators.
Two-Dimensional Gel Electrophoresis: A Reference Protocol.
Saia-Cereda, Veronica M; Aquino, Adriano; Guest, Paul C; Martins-de-Souza, Daniel
2017-01-01
Two-dimensional gel electrophoresis (2DE) has been a mainstay of proteomic techniques for more than four decades. It was even in use for several years before the term proteomics was actually coined in the early 1990s. Over this time, it has been used in the study of many diseases including cancer, diabetes, heart disease, and psychiatric disorders through the proteomic analysis of body fluids and tissues. This chapter presents a general protocol which can be applied in the study of biological samples such as blood serum or plasma and multiple tissues including the brain.
7 Å resolution in protein two-dimensional-crystal X-ray diffraction at Linac Coherent Light Source.
Pedrini, Bill; Tsai, Ching-Ju; Capitani, Guido; Padeste, Celestino; Hunter, Mark S; Zatsepin, Nadia A; Barty, Anton; Benner, W Henry; Boutet, Sébastien; Feld, Geoffrey K; Hau-Riege, Stefan P; Kirian, Richard A; Kupitz, Christopher; Messerschmitt, Marc; Ogren, John I; Pardini, Tommaso; Segelke, Brent; Williams, Garth J; Spence, John C H; Abela, Rafael; Coleman, Matthew; Evans, James E; Schertler, Gebhard F X; Frank, Matthias; Li, Xiao-Dan
2014-07-17
Membrane proteins arranged as two-dimensional crystals in the lipid environment provide close-to-physiological structural information, which is essential for understanding the molecular mechanisms of protein function. Previously, X-ray diffraction from individual two-dimensional crystals did not represent a suitable investigational tool because of radiation damage. The recent availability of ultrashort pulses from X-ray free-electron lasers (XFELs) has now provided a means to outrun the damage. Here, we report on measurements performed at the Linac Coherent Light Source XFEL on bacteriorhodopsin two-dimensional crystals mounted on a solid support and kept at room temperature. By merging data from about a dozen single crystal diffraction images, we unambiguously identified the diffraction peaks to a resolution of 7 Å, thus improving the observable resolution with respect to that achievable from a single pattern alone. This indicates that a larger dataset will allow for reliable quantification of peak intensities, and in turn a corresponding increase in the resolution. The presented results pave the way for further XFEL studies on two-dimensional crystals, which may include pump-probe experiments at subpicosecond time resolution. © 2014 The Author(s) Published by the Royal Society. All rights reserved.
Pseudo-two-dimensional random dimer lattices
Naether, U., E-mail: naether@unizar.es [Instituto de Ciencia de Materiales de Aragón and Departamento de Física de la Materia Condensada, CSIC – Universidad de Zaragoza, 50009 Zaragoza (Spain); Mejía-Cortés, C.; Vicencio, R.A. [Departamento de Física and MSI – Nucleus for Advanced Optics, Center for Optics and Photonics (CEFOP), Facultad de Ciencias, Universidad de Chile, Santiago (Chile)
2015-06-05
We study the long-time wave transport in correlated and uncorrelated disordered 2D arrays. When a separation of dimensions is applied to the model, we find that the previously predicted 1D random dimer phenomenology also appears in so-called pseudo-2D arrays. Therefore, a threshold behavior is observed in terms of the effective size for eigenmodes, as well as in long-time dynamics. A minimum system size is required to observe this threshold, which is very important when considering a possible experimental realization. For the long-time evolution, we find that for correlated lattices a super-diffusive long-range transport is observed. For completely uncorrelated disorder 2D transport becomes sub-diffusive within the localization length and for random binary pseudo-2D arrays localization is observed.
卢明倩; 黄桂媛; 王巧贞; 许超; 黄庶识
2016-01-01
Abtract:[Objective]The aim of this study is to analyze the interaction between the different groups ofβ-carotene in the heating process.[Methods]Two-dimensional correlation spectrosco-py was applied to study the dynamic spectral changes ofβ-carotene from 30℃ to 100℃.[Re-sults]The changes of absorption characteristic peaks ofβ-carotene were inconspicuous in the conventional FTIR spectra and second derivative FTIR spectra during 30℃ to 100℃,which in-dicated that they had no oxidation reation.Two-dimensional correlation analysis showed that the changes of absorption peaks at 968 cm-1 ,1 442 cm-1 ,2 9 6 6 cm-1 and 3 0 1 2 cm-1 were more sen-sitive to temperature.Meanwhile,the order of different groups changes induced by temperature were as follows:the spectral changes of methyl-ene were faster than methyl,the spectral changes of methyl C-H symmetric stretching vibration in low wavenumber were faster than methyl anti-symmetric stretching vibration in high wavenumber,and olefin hydrocarbon symmetric stretching vibration were prior to olefin hydrocarbon anti-symmetric stretching vibration.[Con-clusion]This provides experimental basis for the mechanism of the conformational change ofβ-carotene in heating process.%【目的】了解在升温过程中β-胡萝卜素分子内不同基团之间的相互影响。【方法】采用二维相关红外光谱分析技术,研究β-胡萝卜素在30~100℃变温微扰过程中的动态光谱变化。【结果】β-胡萝卜素分子的吸收特征峰在一维红外光谱和二阶导数谱上变化不明显,表明其没有发生氧化反应。二维相关分析表明,反式共轭烯烃C—H 面外弯曲振动的968 cm-1,烯烃C—H 基团反对称弯曲振动的1442cm-1,甲基C—H 反对称伸缩振动的2966 cm-1和烯烃C—H 的对称伸缩振动的3012 cm-1,这些吸收峰的光谱变化对温度比较敏感。同时在微扰过程中,不同基团变化的先后顺序：亚甲基热运动引起的光谱变化快于
Two-dimensional dispersive shock waves in dissipative optical media
Kartashov, Yaroslav V
2013-01-01
We study generation of two-dimensional dispersive shock waves and oblique dark solitons upon interaction of tilted plane waves with negative refractive index defects embedded into defocusing material with linear gain and two-photon absorption. Different evolution regimes are encountered including the formation of well-localized disturbances for input tilts below critical one, and generation of extended shock waves containing multiple intensity oscillations in the "upstream" region and gradually vanishing oblique dark solitons in "downstream" region for input tilts exceeding critical one. The generation of stable dispersive shock waves is possible only below certain critical defect strength.
Logarithmic divergent thermal conductivity in two-dimensional nonlinear lattices.
Wang, Lei; Hu, Bambi; Li, Baowen
2012-10-01
Heat conduction in three two-dimensional (2D) momentum-conserving nonlinear lattices are numerically calculated via both nonequilibrium heat-bath and equilibrium Green-Kubo algorithms. It is expected by mainstream theories that heat conduction in such 2D lattices is divergent and the thermal conductivity κ increases with lattice length N logarithmically. Our simulations for the purely quartic lattice firmly confirm it. However, very robust finite-size effects are observed in the calculations for the other two lattices, which well explain some existing studies and imply the extreme difficulties in observing their true asymptotic behaviors with affordable computation resources.
Theories on Frustrated Electrons in Two-Dimensional Organic Solids
Chisa Hotta
2012-08-01
Full Text Available Two-dimensional quarter-filled organic solids are a promising class of materials to realize the strongly correlated insulating states called dimer Mott insulator and charge order. In their conducting layer, the molecules form anisotropic triangular lattices, harboring geometrical frustration effect, which could give rise to many interesting states of matter in the two insulators and in the metals adjacent to them. This review is concerned with the theoretical studies on such issue over the past ten years, and provides the systematic understanding on exotic metals, dielectrics, and spin liquids, which are the consequences of the competing correlation and fluctuation under frustration.
Corner wetting transition in the two-dimensional Ising model
Lipowski, Adam
1998-07-01
We study the interfacial behavior of the two-dimensional Ising model at the corner of weakened bonds. Monte Carlo simulations results show that the interface is pinned to the corner at a lower temperature than a certain temperature Tcw at which it undergoes a corner wetting transition. The temperature Tcw is substantially lower than the temperature of the ordinary wetting transition with a line of weakened bonds. A solid-on-solid-like model is proposed, which provides a supplementary description of the corner wetting transition.
Absolute band gaps in two-dimensional graphite photonic crystal
Gaoxin Qiu(仇高新); Fanglei Lin(林芳蕾); Hua Wang(王华); Yongping Li(李永平)
2003-01-01
The off-plane propagation of electromagnetic (EM) waves in a two-dimensional (2D) graphite photoniccrystal structure was studied using transfer matrix method. Transmission spectra calculations indicatethat such a 2D structure has a common band gap from 0.202 to 0.2035 c/a for both H and E polarizationsand for all off-plane angles form 0° up to 90°. The presence of such an absolute band gap implies that 2Dgraphite photonic crystal, which is much easier and more feasible to fabricate, can exhibit some propertiesof a three-dimensional (3D) photonic crystal.
Size-dispersity effects in two-dimensional melting.
Watanabe, Hiroshi; Yukawa, Satoshi; Ito, Nobuyasu
2005-01-01
In order to investigate the effect of size dispersity on two-dimensional melting transitions, hard-disk systems with equimolar bidispersity are studied by means of particle dynamics simulations. From the nonequilibrium relaxation behaviors of bond-orientational order parameters, we find that (i) there is a critical dispersity at which the melting transition of the hexagonal solid vanishes and (ii) the quadratic structure is metastable in a certain region of the dispersity-density parameter space. These results suggest that the dispersity not only destroys order but produces new structures under certain specific conditions.
Quantum computation with two-dimensional graphene quantum dots
Li Jie-Sen; Li Zhi-Bing; Yao Dao-Xin
2012-01-01
We study an array of graphene nano sheets that form a two-dimensional S =1/2 Kagome spin lattice used for quantum computation.The edge states of the graphene nano sheets axe used to form quantum dots to confine electrons and perform the computation.We propose two schemes of bang-bang control to combat decoherence and realize gate operations on this array of quantum dots.It is shown that both schemes contain a great amount of information for quantum computation.The corresponding gate operations are also proposed.
Complex Saddles in Two-dimensional Gauge Theory
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.
Quantum skyrmions in two-dimensional chiral magnets
Takashima, Rina; Ishizuka, Hiroaki; Balents, Leon
2016-10-01
We study the quantum mechanics of magnetic skyrmions in the vicinity of the skyrmion-crystal to ferromagnet phase boundary in two-dimensional magnets. We show that the skyrmion excitation has an energy dispersion that splits into multiple bands due to the combination of magnus force and the underlying lattice. Condensation of the skyrmions can give rise to an intermediate phase between the skyrmion crystal and ferromagnet: a quantum liquid, in which skyrmions are not spatially localized. We show that the critical behavior depends on the spin size S and the topological number of the skyrmion. Experimental signatures of quantum skyrmions in inelastic neutron-scattering measurements are also discussed.
Local kinetic effects in two-dimensional plasma turbulence.
Servidio, S; Valentini, F; Califano, F; Veltri, P
2012-01-27
Using direct numerical simulations of a hybrid Vlasov-Maxwell model, kinetic processes are investigated in a two-dimensional turbulent plasma. In the turbulent regime, kinetic effects manifest through a deformation of the ion distribution function. These patterns of non-Maxwellian features are concentrated in space nearby regions of strong magnetic activity: the distribution function is modulated by the magnetic topology, and can elongate along or across the local magnetic field. These results open a new path on the study of kinetic processes such as heating, particle acceleration, and temperature anisotropy, commonly observed in astrophysical and laboratory plasmas.
Drift modes of a quasi-two-dimensional current sheet
Artemyev, A. V.; Malova, Kh. V.; Popov, V. Yu.; Zelenyi, L. M. [Russian Academy of Sciences, Space Research Institute (Russian Federation)
2012-03-15
Stability of a plasma configuration consisting of a thin one-dimensional current sheet embedded into a two-dimensional background current sheet is studied. Drift modes developing in plasma as unstable waves along the current direction are considered. Dispersion relations for kink and sausage perturbation modes are obtained depending on the ratio of parameters of thin and background current sheets. It is shown that the existence of the background sheet results in a decrease in the instability growth rates and a significant increase in the perturbation wavelengths. The role of drift modes in the excitation of oscillations observed in the current sheet of the Earth's magnetotail is discussed.
Magnetic quantum dot in two-dimensional topological insulators
Li, Guo; Zhu, Jia-Lin; Yang, Ning
2017-03-01
Magnetic quantum dots in two-dimensional band and topological insulators are studied by solving the modified Dirac model under nonuniform magnetic fields. The Landau levels split into discrete states with certain angular momentum. The states splitting from the zero Landau levels lie in the energy gap for topological insulators but are out of the gap for band insulators. It is found that the ground states oscillate between the spin-up and spin-down states when the magnetic field or the dot size changes. The oscillation manifests itself as changes of sign and strength of charge currents near the dot's edge.
Smoothed Particle Hydrodynamics Method for Two-dimensional Stefan Problem
Tarwidi, Dede
2016-01-01
Smoothed particle hydrodynamics (SPH) is developed for modelling of melting and solidification. Enthalpy method is used to solve heat conduction equations which involved moving interface between phases. At first, we study the melting of floating ice in the water for two-dimensional system. The ice objects are assumed as solid particles floating in fluid particles. The fluid and solid motion are governed by Navier-Stokes equation and basic rigid dynamics equation, respectively. We also propose a strategy to separate solid particles due to melting and solidification. Numerical results are obtained and plotted for several initial conditions.
Müller, Cristina Emöke Erika; Aranha, Maria Fernanda Montans; Gavião, Maria Beatriz Duarte
2015-04-01
Chronic pain has been often associated with myofascial pain syndrome (MPS), which is determined by myofascial trigger points (MTrP). New features have been tested for MTrP diagnosis. The aim of this study was to evaluate two-dimensional ultrasonography (2D US) and ultrasound elastography (UE) images and elastograms of upper trapezius MTrP during electroacupuncture (EA) and acupuncture (AC) treatment. 24 women participated, aged between 20 and 40 years (M ± SD = 27.33 ± 5.05) with a body mass index ranging from 18.03 to 27.59 kg/m2 (22.59 ± 3.11), a regular menstrual cycle, at least one active MTrP at both right (RTPz) and left trapezius (LTPz) and local or referred pain for up to six months. Subjects were randomized into EA and AC treatment groups and the control sham AC (SHAM) group. Intensity of pain was assessed by visual analogue scale; MTrP mean area and strain ratio (SR) by 2D US and UE. A significant decrease of intensity in general, RTPz, and LTPz pain was observed in the EA group (p = 0.027; p < 0.001; p = 0.005, respectively) and in general pain in the AC group (p < 0.001). Decreased MTrP area in RTPz and LTPz were observed in AC (p < 0.001) and EA groups (RTPz, p = 0.003; LTPz, p = 0.005). Post-treatment SR in RTPz and LTPz was lower than pre-treatment in both treatment groups. 2D US and UE effectively characterized MTrP and surrounding tissue, pointing to the possibility of objective confirmation of subjective EA and AC treatment effects. © The Author(s) 2014.
Atom-Based Geometrical Fingerprinting of Conformal Two-Dimensional Materials
Mehboudi, Mehrshad
The shape of two-dimensional materials plays a significant role on their chemical and physical properties. Two-dimensional materials are basic meshes that are formed by mesh points (vertices) given by atomic positions, and connecting lines (edges) between points given by chemical bonds. Therefore the study of local shape and geometry of two-dimensional materials is a fundamental prerequisite to investigate physical and chemical properties. Hereby the use of discrete geometry to discuss the shape of two-dimensional materials is initiated. The local geometry of a surface embodied in 3D space is determined using four invariant numbers from the metric and curvature tensors which indicates how much the surface is stretched and curved under a deformation as compared to a reference pre-deformed conformation. Many different disciplines advance theories on conformal two-dimensional materials by relying on continuum mechanics and fitting continuum surfaces to the shape of conformal two-dimensional materials. However two-dimensional materials are inherently discrete. The continuum models are only applicable when the size of two-dimensional materials is significantly large and the deformation is less than a few percent. In this research, the knowledge of discrete differential geometry was used to tell the local shape of conformal two-dimensional materials. Three kind of two-dimensional materials are discussed: 1) one atom thickness structures such as graphene and hexagonal boron nitride; 2) high and low buckled 2D meshes like stanene, leadene, aluminum phosphate; and, 3) multi layer 2D materials such as Bi2Se3 and WSe2. The lattice structures of these materials were created by designing a mechanical model - the mechanical model was devised in the form of a Gaussian bump and density-functional theory was used to inform the local height; and, the local geometries are also discussed.
Qi, Wei; Ishimaru, Ichiro
2010-02-01
We propose an image-producing Fourier spectroscopic technology that enables two-dimensional spectroscopic images to be obtained within the focusing plane alone. This technology incorporates auto-correlational phase-shift interferometry that uses only object light generated by the bright points that optically make up the object. We are currently involved in studies of non-invasive technologies used to measure blood components such as glucose and lipids, which are measured for use in daily living. Previous studies have investigated non-invasive technologies that measure blood glucose levels by utilizing near-infrared light that permeates the skin well. It has been confirmed that subtle changes in the concentration of a glucose solution, a sample used to measure the glucose level, can be measured by analyzing the spectroscopic characteristics of near-infrared light; however, when applied to a biomembrane, technology such as this is incapable of precisely measuring the glucose level because light diffusion within the skin disturbs the measurement. Our proposed technology enables two-dimensional spectroscopy to a limited depth below the skin covered by the measurement. Specifically, our technology concentrates only on the vascular territory near the skin surface, which is only minimally affected by light diffusion, as discussed previously; the spectroscopic characteristics of this territory are obtained and the glucose level can be measured with good sensitivity. In this paper we propose an image-producing Fourier spectroscopy method that is used as the measuring technology in producing a three-dimensional spectroscopic image.
Ultrafast two dimensional infrared chemical exchange spectroscopy
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
Molecular assembly on two-dimensional materials
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
The encoding complexity of two dimensional range minimum data structures
Brodal, Gerth Stølting; Brodnik, Andrej; Davoodi, Pooya
2013-01-01
In the two-dimensional range minimum query problem an input matrix A of dimension m ×n, m ≤ n, has to be preprocessed into a data structure such that given a query rectangle within the matrix, the position of a minimum element within the query range can be reported. We consider the space complexity...... of the encoding variant of the problem where queries have access to the constructed data structure but can not access the input matrix A, i.e. all information must be encoded in the data structure. Previously it was known how to solve the problem with space O(mn min {m,logn}) bits (and with constant query time...
Two-dimensional nuclear magnetic resonance of quadrupolar systems
Wang, Shuanhu
1997-09-17
This dissertation describes two-dimensional nuclear magnetic resonance theory and experiments which have been developed to study quadruples in the solid state. The technique of multiple-quantum magic-angle spinning (MQMAS) is extensively reviewed and expanded upon in this thesis. Specifically, MQMAS is first compared with another technique, dynamic-angle spinning (DAS). The similarity between the two techniques allows us to extend much of the DAS work to the MQMAS case. Application of MQMAS to a series of aluminum containing materials is then presented. The superior resolution enhancement through MQMAS is exploited to detect the five- and six-coordinated aluminum in many aluminosilicate glasses. Combining the MQMAS method with other experiments, such as HETCOR, greatly expands the possibility of the use of MQMAS to study a large range of problems and is demonstrated in Chapter 5. Finally, the technique switching-angle spinning (SAS) is applied to quadrupolar nuclei to fully characterize a quadrupolar spin system in which all of the 8 NMR parameters are accurately determined. This dissertation is meant to demonstrate that with the combination of two-dimensional NMR concepts and new advanced spinning technologies, a series of multiple-dimensional NMR techniques can be designed to allow a detailed study of quadrupolar nuclei in the solid state.
Dirac quasinormal modes of two-dimensional charged dilatonic black holes
Becar, Ramon [Universidad Catolica de Temuco, Departamento de Ciencias Matematicas y Fisicas, Temuco (Chile); Gonzalez, P.A. [Universidad Diego Portales, Facultad de Ingenieria, Santiago (Chile); Vasquez, Yerko [Universidad de La Serena, Departamento de Fisica, Facultad de Ciencias, La Serena (Chile)
2014-06-15
We study charged fermionic perturbations in the background of two-dimensional charged dilatonic black holes, and we present the exact Dirac quasinormal modes. Also, we study the stability of these black holes under charged fermionic perturbations. (orig.)
Capillary-driven two-dimensional buoyancy in vertical soap films
Adami, N.; Caps, H.
2014-05-01
The present study aims to investigate the capillary-driven buoyant effects in nearly two-dimensional systems. The case of rising rings in vertical soap films is studied both experimentally and theoretically. Since the pioneering works of Mysels and coworkers, the thickness differences and related two-dimensional densities are considered as the motor leading to two-dimensional buoyancy. We show how this effect can be re-interpreted in terms of the surface tension profiles present at the film interfaces. We propose a model involving surface tension profiles, as well as an adapted expression for the mass of the rising rings, and compare it to experimental data.
Comparative Skeletal Muscle Proteomics Using Two-Dimensional Gel Electrophoresis.
Murphy, Sandra; Dowling, Paul; Ohlendieck, Kay
2016-09-09
The pioneering work by Patrick H. O'Farrell established two-dimensional gel electrophoresis as one of the most important high-resolution protein separation techniques of modern biochemistry (Journal of Biological Chemistry1975, 250, 4007-4021). The application of two-dimensional gel electrophoresis has played a key role in the systematic identification and detailed characterization of the protein constituents of skeletal muscles. Protein changes during myogenesis, muscle maturation, fibre type specification, physiological muscle adaptations and natural muscle aging were studied in depth by the original O'Farrell method or slightly modified gel electrophoretic techniques. Over the last 40 years, the combined usage of isoelectric focusing in the first dimension and sodium dodecyl sulfate polyacrylamide slab gel electrophoresis in the second dimension has been successfully employed in several hundred published studies on gel-based skeletal muscle biochemistry. This review focuses on normal and physiologically challenged skeletal muscle tissues and outlines key findings from mass spectrometry-based muscle proteomics, which was instrumental in the identification of several thousand individual protein isoforms following gel electrophoretic separation. These muscle-associated protein species belong to the diverse group of regulatory and contractile proteins of the acto-myosin apparatus that forms the sarcomere, cytoskeletal proteins, metabolic enzymes and transporters, signaling proteins, ion-handling proteins, molecular chaperones and extracellular matrix proteins.
Confinement and dynamical regulation in two-dimensional convective turbulence
Bian, N.H.; Garcia, O.E.
2003-01-01
In this work the nature of confinement improvement implied by the self-consistent generation of mean flows in two-dimensional convective turbulence is studied. The confinement variations are linked to two distinct regulation mechanisms which are also shown to be at the origin of low-frequency bur......In this work the nature of confinement improvement implied by the self-consistent generation of mean flows in two-dimensional convective turbulence is studied. The confinement variations are linked to two distinct regulation mechanisms which are also shown to be at the origin of low......-frequency bursting in the fluctuation level and the convective heat flux integral, both resulting in a state of large-scale intermittency. The first one involves the control of convective transport by sheared mean flows. This regulation relies on the conservative transfer of kinetic energy from tilted fluctuations...... to the mean component of the flow. Bursting can also result from the quasi-linear modification of the linear instability drive which is the mean pressure gradient. For each bursting process the relevant zero-dimensional model equations are given. These are finally coupled in a minimal model of convection...
Two-dimensional gas of massless Dirac fermions in graphene.
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.
Comparative Skeletal Muscle Proteomics Using Two-Dimensional Gel Electrophoresis
Sandra Murphy
2016-09-01
Full Text Available The pioneering work by Patrick H. O’Farrell established two-dimensional gel electrophoresis as one of the most important high-resolution protein separation techniques of modern biochemistry (Journal of Biological Chemistry 1975, 250, 4007–4021. The application of two-dimensional gel electrophoresis has played a key role in the systematic identification and detailed characterization of the protein constituents of skeletal muscles. Protein changes during myogenesis, muscle maturation, fibre type specification, physiological muscle adaptations and natural muscle aging were studied in depth by the original O’Farrell method or slightly modified gel electrophoretic techniques. Over the last 40 years, the combined usage of isoelectric focusing in the first dimension and sodium dodecyl sulfate polyacrylamide slab gel electrophoresis in the second dimension has been successfully employed in several hundred published studies on gel-based skeletal muscle biochemistry. This review focuses on normal and physiologically challenged skeletal muscle tissues and outlines key findings from mass spectrometry-based muscle proteomics, which was instrumental in the identification of several thousand individual protein isoforms following gel electrophoretic separation. These muscle-associated protein species belong to the diverse group of regulatory and contractile proteins of the acto-myosin apparatus that forms the sarcomere, cytoskeletal proteins, metabolic enzymes and transporters, signaling proteins, ion-handling proteins, molecular chaperones and extracellular matrix proteins.
Comprehensive two-dimensional liquid chromatographic analysis of poloxamers.
Malik, Muhammad Imran; Lee, Sanghoon; Chang, Taihyun
2016-04-15
Poloxamers are low molar mass triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), having number of applications as non-ionic surfactants. Comprehensive one and two-dimensional liquid chromatographic (LC) analysis of these materials is proposed in this study. The separation of oligomers of both types (PEO and PPO) is demonstrated for several commercial poloxamers. This is accomplished at the critical conditions for one of the block while interaction for the other block. Reversed phase LC at CAP of PEO allowed for oligomeric separation of triblock copolymers with regard to PPO block whereas normal phase LC at CAP of PPO renders oligomeric separation with respect to PEO block. The oligomeric separation with regard to PEO and PPO are coupled online (comprehensive 2D-LC) to reveal two-dimensional contour plots by unconventional 2D IC×IC (interaction chromatography) coupling. The study provides chemical composition mapping of both PEO and PPO, equivalent to combined molar mass and chemical composition mapping for several commercial poloxamers.
Configuration of Shock Waves in Two-Dimensional Overexpanded Jets
Masashi Kashitani; Yutaka Yamaguchi; Yoshiaki Miyazato; Mitsuharu Masuda; Kazuyasu Matsuo
2003-01-01
An experimental and analytical study has been carried out to obtain the clear understanding of a shock wave transition associated with a steady two-dimensional overexpanded flow. Two-dimensional inviscid theory with respect to a shock wave reflection is used in the present study on the characteristic of shock waves. The results obtained from the flow analysis are compared with those obtained from flow visualizations. It is shown that in the region of regular reflection, the angle of an incident shock wave becomes lower than that calculated by two shock theory with an increment in the ratio pe/pb of the nozzle exit pressure pe to the back pressure pb. It is indicated that the configuration of shock waves in overexpanded jets is influenced by the divergent angle at the nozzle exit. Also it is shown from the flow visualization that a series of shock waves move into the nozzle inside with a decrease in pressure ratio pe/pb, even if the pe/pb is under overexpanded conditions.
Extending models for two-dimensional constraints
Forchhammer, Søren
2009-01-01
Random fields in two dimensions may be specified on 2 times 2 elements such that the probabilities of finite configurations and the entropy may be calculated explicitly. The Pickard random field is one example where probability of a new (non-boundary) element is conditioned on three previous...... elements. To extend the concept we consider extending such a field such that a vector or block of elements is conditioned on a larger set of previous elements. Given a stationary model defined on 2 times 2 elements, iterative scaling is used to define the extended model. The extended model may be used...
Quantum creep in a highly crystalline two-dimensional superconductor
Saito, Yu; Kasahara, Yuichi; Ye, Jianting; Iwasa, Yoshihiro; Nojima, Tsutomu
Conventional studies on quantum phase transitions, especially on superconductor-insulator or superconductor-metal-insulator transitions have been performed in deposited metallic thin films such as Bismuth or MoGe. Although the techniques of thin films deposition have been considerably improved, unintentional disorder such as impurities and deficiencies, generating the pinning centers, seems to still exist in such systems. The mechanical exfoliated highly crystalline two-dimensional material can be a good candidate to realize a less-disordered 2D superconductor with extremely weak pinning, combined with transfer method or ionic-liquid gating. We report on the quantum metal, namely, magnetic-field-induced metallic state observed in an ion-gated two-dimensional superconductor based on an ultra-highly crystalline layered band insulator, ZrNCl. We found that the superconducting state is extremely fragile against external magnetic fields; that is, zero resistance state immediately disappears, once an external magnetic field switches on. This is because the present system is relatively clean and the pinning potential is extremely weak, which cause quantum tunneling and flux flow of vortices, resulting in metallic ground state.
Unpacking of a Crumpled Wire from Two-Dimensional Cavities.
Thiago A Sobral
Full Text Available The physics of tightly packed structures of a wire and other threadlike materials confined in cavities has been explored in recent years in connection with crumpled systems and a number of topics ranging from applications to DNA packing in viral capsids and surgical interventions with catheter to analogies with the electron gas at finite temperature and with theories of two-dimensional quantum gravity. When a long piece of wire is injected into two-dimensional cavities, it bends and originates in the jammed limit a series of closed structures that we call loops. In this work we study the extraction of a crumpled tightly packed wire from a circular cavity aiming to remove loops individually. The size of each removed loop, the maximum value of the force needed to unpack each loop, and the total length of the extracted wire were measured and related to an exponential growth and a mean field model consistent with the literature of crumpled wires. Scaling laws for this process are reported and the relationship between the processes of packing and unpacking of wire is commented upon.
Two-Dimensional Gel Electrophoresis and 2D-DIGE.
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.
Unpacking of a Crumpled Wire from Two-Dimensional Cavities.
Sobral, Thiago A; Gomes, Marcelo A F; Machado, Núbia R; Brito, Valdemiro P
2015-01-01
The physics of tightly packed structures of a wire and other threadlike materials confined in cavities has been explored in recent years in connection with crumpled systems and a number of topics ranging from applications to DNA packing in viral capsids and surgical interventions with catheter to analogies with the electron gas at finite temperature and with theories of two-dimensional quantum gravity. When a long piece of wire is injected into two-dimensional cavities, it bends and originates in the jammed limit a series of closed structures that we call loops. In this work we study the extraction of a crumpled tightly packed wire from a circular cavity aiming to remove loops individually. The size of each removed loop, the maximum value of the force needed to unpack each loop, and the total length of the extracted wire were measured and related to an exponential growth and a mean field model consistent with the literature of crumpled wires. Scaling laws for this process are reported and the relationship between the processes of packing and unpacking of wire is commented upon.
杨仁杰; 杨延荣; 杜艳红; 常若葵; 张志勇
2011-01-01
将红外光谱与二维相关谱技术结合起来对牛奶中掺杂的目标物三聚氰胺进行了检测。配置浓度为3g/L三聚氰胺牛奶溶液，并采集样品在不同温度下的红外光谱图。以温度为外扰，分别构建纯牛奶与掺杂三聚氰胺牛奶的二维相关谱，研究了各自的二维相关特性，并进行对比、分析。结果表明：在14001800cm-1区间内，掺杂三聚氰胺牛奶在同步图上出现3个自相关峰，分别在1448cm-1，1552cm-1和1640cm-1，这三个峰是牛奶中掺杂三聚氰胺的特征吸收。该方法可实现对纯牛奶与掺杂牛奶的正确识别，对提高乳制品的质量和保护消费者的利益具有重要的意义。%In this paper, Fourier transform infrared spectroscopy combined with two-dimensional （2D） correlation spectroscopy was used to investigate the melamine of milk. The sample adulterated with concentration of melamine （3 g/L ） was prepared and the infrared spectra were measured at different temperature. Then the 2D correlation spectroscopy was calculated under the perturbation of temperature. In the range between 1 400 and 1 800 cm-1, three autopeaks were aroused at 1 448 cm-1, 1 552 cm-2 and 1 640 cm-2 in synchronous spectrum, which are the absorbance features of melamine in milk. The method can be used for a correct discrimination on whether the milk is adulterated. The study is important to improve the quality of dairy products and to protect the benefits of consumers.
Hinrichsen, B [Max-Planck-Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart (Germany); Dinnebier, R E [Max-Planck-Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart (Germany); Rajiv, P [Max-Planck-Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart (Germany); Hanfland, M [European Synchrotron Radiation Facility, 6 rue Jules Horowitz, BP220, 38043 Grenoble Cedex (France); Grzechnik, A [Departamento de Fisica de la Materia Condensada, Facultad de Ciencia y Technologia, Universidad del Pais Vasco, Apartado 644, E-48080 Bilbao (Spain); Jansen, M [Max-Planck-Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart (Germany)
2006-06-28
Methods have been developed to facilitate the data analysis of multiple two-dimensional powder diffraction images. These include, among others, automatic detection and calibration of Debye-Scherrer ellipses using pattern recognition techniques, and signal filtering employing established statistical procedures like fractile statistics. All algorithms are implemented in the freely available program package Powder3D developed for the evaluation and graphical presentation of large powder diffraction data sets. As a case study, we report the pressure dependence of the crystal structure of iron antimony oxide FeSb{sub 2}O{sub 4} (p{<=}21 GPa, T = 298 K) using high-resolution angle dispersive x-ray powder diffraction. FeSb{sub 2}O{sub 4} shows two phase transitions in the measured pressure range. The crystal structures of all modifications consist of frameworks of Fe{sup 2+}O{sub 6} octahedra and irregular Sb{sup 3+}O{sub 4} polyhedra. At ambient conditions, FeSb{sub 2}O{sub 4} crystallizes in space group P4{sub 2}/mbc (phase I). Between p = 3.2 GPa and 4.1 GPa it exhibits a displacive second order phase transition to a structure of space group P 2{sub 1}/c (phase II, a = 5.7792(4) A, b = 8.3134(9) A, c = 8.4545(11) A, {beta} = 91.879(10){sup 0}, at p = 4.2 GPa). A second phase transition occurs between p = 6.4 GPa and 7.4 GPa to a structure of space group P4{sub 2}/m (phase III, a = 7.8498(4) A, c = 5.7452(5) A, at p = 10.5 GPa). A nonlinear compression behaviour over the entire pressure range is observed, which can be described by three Vinet equations in the ranges from p = 0.52 GPa to p 3.12 GPa, p = 4.2 GPa to p = 6.3 GPa and from p = 7.5 GPa to p = 19.8 GPa. The extrapolated bulk moduli of the high-pressure phases were determined to K{sub 0} = 49(2) GPa for phase I, K{sub 0} = 27(3) GPa for phase II and K{sub 0} = 45(2) GPa for phase III. The crystal structures of all phases are refined against x-ray powder data measured at several pressures between p = 0.52 GPa
Hinrichsen, B; Dinnebier, R E; Rajiv, P; Hanfland, M; Grzechnik, A; Jansen, M
2006-06-28
Methods have been developed to facilitate the data analysis of multiple two-dimensional powder diffraction images. These include, among others, automatic detection and calibration of Debye-Scherrer ellipses using pattern recognition techniques, and signal filtering employing established statistical procedures like fractile statistics.All algorithms are implemented in the freely available program package Powder3D developed for the evaluation and graphical presentation of large powder diffraction data sets.As a case study, we report the pressure dependence of the crystal structure of iron antimony oxide FeSb(2)O(4) (p≤21 GPa, T = 298 K) using high-resolution angle dispersive x-ray powder diffraction. FeSb(2)O(4) shows two phase transitions in the measured pressure range. The crystal structures of all modifications consist of frameworks of Fe(2+)O(6) octahedra and irregular Sb(3+)O(4) polyhedra. At ambient conditions, FeSb(2)O(4) crystallizes in space group P4(2)/mbc (phase I). Between p = 3.2 GPa and 4.1 GPa it exhibits a displacive second order phase transition to a structure of space group P 2(1)/c (phase II, a = 5.7792(4) Å, b = 8.3134(9) Å, c = 8.4545(11) Å, β = 91.879(10)°, at p = 4.2 GPa). A second phase transition occurs between p = 6.4 GPa and 7.4 GPa to a structure of space group P4(2)/m (phase III, a = 7.8498(4) Å, c = 5.7452(5) Å, at p = 10.5 GPa). A nonlinear compression behaviour over the entire pressure range is observed, which can be described by three Vinet equations in the ranges from p = 0.52 GPa to p = 3.12 GPa, p = 4.2 GPa to p = 6.3 GPa and from p = 7.5 GPa to p = 19.8 GPa. The extrapolated bulk moduli of the high-pressure phases were determined to K(0) = 49(2) GPa for phase I, K(0) = 27(3) GPa for phase II and K(0) = 45(2) GPa for phase III. The crystal structures of all phases are refined against x-ray powder data measured at several pressures between p = 0.52 GPa, and 10.5 GPa.
刘艳; 赵鹏飞; 王晓放
2012-01-01
Cavitating flows around a two-dimensional NACA66 hydrofoil with an angle of attack of 6.5° are studied using the mixture multiphase model and cavitation model.The Singhal′s full cavitation model（FCM） and the Zwart-Gerber-Belamri（Z-G-B） cavitation model are applied,and based on experimental data,results obtained from the two models are compared in terms of pressure distribution coefficient on the surface of the hydrofoil,lift and drag coefficients and flow field structures.The experimental results show that for the FCM,the value of mass fraction of noncondensible gases has some effects on computational results.The length of cavitation zone becomes smaller with the mass fraction of noncondensible gases decreasing.For the Z-G-B model,both vaporization and condensation coefficients have influence on results.In general,both cavitation models give satisfactory prediction results by choosing reasonable empirical coefficients.%采用混合多相流模型和空化模型对攻角为6.5°的NACA66型二维水翼的空化流动进行数值研究.使用Singhal全空化模型（FCM）和Zwart-Gerber-Belamri（Z-G-B）空化模型,以实验数据为基准,对这两种空化模型得到的翼型表面压力分布系数和升、阻力系数以及流场结构进行了比较和分析,结果表明：FCM中,不凝结气体质量分数对计算结果影响较大,空化区长度随着不凝结气体质量分数的减小而变小;Z-G-B空化模型中,蒸发系数和凝结系数对结果有较大影响.总体说来,通过选取合理的经验系数,两种空化模型都给出了令人满意的空化流动结果.
ON CONVERGENCE RATE OF APPROXIMATION FOR TWO-DIMENSIONAL BASKAKOV OPERATORS
Feng Guo
2003-01-01
In this paper, we study the convergence rate of two-dimensional Baskakov operators with Jacobiweights making use of multivariate decompose skills and results of one-dimensional Baskakov operators, and obtain the direct approximationtheorem.
Pineda, Inti; Dagdug, Leonardo [Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, Apartado Postal 55-534, 09340 México Distrito Federal (Mexico)
2014-01-14
Diffusive transport of particles is a ubiquitous feature of physical, chemical and biological systems. Typical structures like pores, tubes or fibers, are quasi one-dimensional, such that we need to solve 2+1 or 3+1 dimensional differential equations to describe correctly transport along them. The so-called Fick-Jacobs approach dramatically simplifies the problem if one assumes that a solute distribution in any cross-section of the channel is uniform at equilibrium. That study focuses on the mapping of the diffusion equation in a two-dimensional narrow asymmetric channel of varying cross section onto the longitudinal coordinate. We present a generalization to the case of an asymmetric channel using the projection method introduced earlier by Kalinay and Percus. We derive an expansion of the effective diffusion coefficient, which represents corrections to the Fick-Jacobs equation and contains the well-known previous results as special cases. Finally, we study numerically some specific two-dimensional asymmetric channel configurations to test and show the broader applicability of this effective diffusion coefficient formula.
Two-dimensional, isothermal, multi-component model for a polymer electrolyte membrane fuel cell
Mahinpey, N.; Jagannathan, A.; Idem, R. [Regina Univ., SK (Canada). Faculty of Engineering
2007-07-01
A fuel cell is an electrochemical energy conversion device which is more efficient than an internal combustion engine in converting fuel to power. Numerous fuel cell models have been developed by a number of authors accounting for the various physical processes. Earlier models were restricted to being one dimensional, steady-state, and isothermal while more recent two-dimensional models had several limitations. This paper presented the results of a study that developed a two-dimensional computational fluid dynamics model of a polymer electrolyte membrane fuel cell using a finite element method to solve a multi-component transport model coupled with flow in porous media, charge balance, electrochemical kinetics, and rigorous water balance in the membrane. The mass transport, momentum transport, and electrochemical processes occurring in the membrane electrolyte and catalyst layers were modeled. The local equilibrium was assumed at the interfaces and the model was combined with the kinetics and was analytically solved for the anodic and cathodic current using an agglomerate spherical catalyst pellet. The paper compared the modeling results with previously published experimental data. The study investigated the effects of channel and bipolar plate shoulder size, porosity of the electrodes, temperature, relative humidity and current densities on the cell performance. It was concluded that smaller sized channels and bipolar plate shoulders were required to obtain higher current densities, although larger channels were satisfactory at moderate current densities. 13 refs., 5 figs.
Validating two-dimensional leadership models on three-dimensionally structured fish schools
Nagy, Máté; Holbrook, Robert I.; Biro, Dora; Burt de Perera, Theresa
2017-01-01
Identifying leader–follower interactions is crucial for understanding how a group decides where or when to move, and how this information is transferred between members. Although many animal groups have a three-dimensional structure, previous studies investigating leader–follower interactions have often ignored vertical information. This raises the question of whether commonly used two-dimensional leader–follower analyses can be used justifiably on groups that interact in three dimensions. To address this, we quantified the individual movements of banded tetra fish (Astyanax mexicanus) within shoals by computing the three-dimensional trajectories of all individuals using a stereo-camera technique. We used these data firstly to identify and compare leader–follower interactions in two and three dimensions, and secondly to analyse leadership with respect to an individual's spatial position in three dimensions. We show that for 95% of all pairwise interactions leadership identified through two-dimensional analysis matches that identified through three-dimensional analysis, and we reveal that fish attend to the same shoalmates for vertical information as they do for horizontal information. Our results therefore highlight that three-dimensional analyses are not always required to identify leader–follower relationships in species that move freely in three dimensions. We discuss our results in terms of the importance of taking species' sensory capacities into account when studying interaction networks within groups.
Generalized geometry of two-dimensional vacua
Rosa, Dario
2013-01-01
We derive the conditions for unbroken supersymmetry for a Mink_2, (2,0) vacuum, arising from Type II supergravity on a compact eight-dimensional manifold M_8. When specialized to internal manifolds enjoying SU(4)xSU(4) structure the resulting system is elegantly rewritten in terms of generalized complex geometry. This particular class of vacua violates the correspondence between supersymmetry conditions and calibrations conditions of D branes (supersymmetry-calibrations correspondence). Our analysis includes and extends previous results about the failure of the supersymmetry-calibrations correspondence, and confirms the existence of a precise relation between such a failure and a subset of the supersymmetry conditions.
Celis, J E; Madsen, Peder; Rasmussen, H H
1991-01-01
proteins in alphabetical order), "basal cell markers", "differentiation markers", "proteins highly up-regulated in psoriatic skin", "microsequenced proteins" and "human autoantigens". For reference, we have also included 2-D gel (isoelectric focusing) patterns of cultured normal and psoriatic keratinocytes......A two-dimensional (2-D) gel database of cellular proteins from noncultured, unfractionated normal human epidermal keratinocytes has been established. A total of 2651 [35S]methionine-labeled cellular proteins (1868 isoelectric focusing, 783 nonequilibrium pH gradient electrophoresis) were resolved...
The Chandrasekhar's Equation for Two-Dimensional Hypothetical White Dwarfs
De, Sanchari
2014-01-01
In this article we have extended the original work of Chandrasekhar on the structure of white dwarfs to the two-dimensional case. Although such two-dimensional stellar objects are hypothetical in nature, we strongly believe that the work presented in this article may be prescribed as Master of Science level class problem for the students in physics.
Beginning Introductory Physics with Two-Dimensional Motion
Huggins, Elisha
2009-01-01
During the session on "Introductory College Physics Textbooks" at the 2007 Summer Meeting of the AAPT, there was a brief discussion about whether introductory physics should begin with one-dimensional motion or two-dimensional motion. Here we present the case that by starting with two-dimensional motion, we are able to introduce a considerable…
Explorative data analysis of two-dimensional electrophoresis gels
Schultz, J.; Gottlieb, D.M.; Petersen, Marianne Kjerstine;
2004-01-01
Methods for classification of two-dimensional (2-DE) electrophoresis gels based on multivariate data analysis are demonstrated. Two-dimensional gels of ten wheat varieties are analyzed and it is demonstrated how to classify the wheat varieties in two qualities and a method for initial screening...
Mechanics of Apparent Horizon in Two Dimensional Dilaton Gravity
Cai, Rong-Gen
2016-01-01
In this article, we give a definition of apparent horizon in a two dimensional general dilaton gravity theory. With this definition, we construct the mechanics of the apparent horizon by introducing a quasi-local energy of the theory. Our discussion generalizes the apparent horizons mechanics in general spherically symmetric spactimes in four or higher dimensions to the two dimensional dilaton gravity case.
Evidence of two-dimensional quantum Wigner Crystal in a zero magnetic field
Huang, Jian; Pfeiffer, Loren; West, Ken
2014-03-01
In disorder-dominated cases, Anderson localization occurs as a result of destructive interference effects caused by (short-ranged) random disorders. On the other hand, in interaction-dominated scenarios, striking manifestations of quantum physics emerge in response to strong inter-particle Coulomb energy (EC). The most prominent interaction-driven effect is the Wigner crystallization (WC) of electrons, an electron solid made up with spatially separated charges settling in a form of a lattice. The classical version of the crystallization, with the Debye temperature ΘD
A two-dimensional CA model for traffic flow with car origin and destination
In-nami, Junji; Toyoki, Hiroyasu
2007-05-01
Dynamic phase transitions in a two-dimensional traffic flow model defined on a decorated square-lattice are studied numerically. The square-lattice point and the decorated site denote intersections and roads, respectively. In the present model, a car has a finite deterministic path between the origin and the destination, which is assigned to the car from the beginning. In this new model, we found a new phase between the free-flow phase and the frozen-jam phase that is absent from previous models. The new model is characterized by the persistence of a macroscopic cluster. Furthermore, the behavior in this macroscopic cluster phase is classified into three regions characterized by the shape of the cluster. The boundary of the three regions is phenomenologically estimated. When the trip length is short and the car density is high, both ends of the belt-like cluster connect to each other through the periodic boundary with some probability. This type of cluster is classified topologically as a string on a two-dimensional torus.
Two-dimensional habitat modeling in the Yellowstone/Upper Missouri River system
Waddle, T. J.; Bovee, K.D.; Bowen, Z.H.
1997-01-01
This study is being conducted to provide the aquatic biology component of a decision support system being developed by the U.S. Bureau of Reclamation. In an attempt to capture the habitat needs of Great Plains fish communities we are looking beyond previous habitat modeling methods. Traditional habitat modeling approaches have relied on one-dimensional hydraulic models and lumped compositional habitat metrics to describe aquatic habitat. A broader range of habitat descriptors is available when both composition and configuration of habitats is considered. Habitat metrics that consider both composition and configuration can be adapted from terrestrial biology. These metrics are most conveniently accessed with spatially explicit descriptors of the physical variables driving habitat composition. Two-dimensional hydrodynamic models have advanced to the point that they may provide the spatially explicit description of physical parameters needed to address this problem. This paper reports progress to date on applying two-dimensional hydraulic and habitat models on the Yellowstone and Missouri Rivers and uses examples from the Yellowstone River to illustrate the configurational metrics as a new tool for assessing riverine habitats.
Wave-induced response of a floating two-dimensional body with a moonpool
Fredriksen, Arnt G.; Kristiansen, Trygve; Faltinsen, Odd M.
2015-01-01
Regular wave-induced behaviour of a floating stationary two-dimensional body with a moonpool is studied. The focus is on resonant piston-mode motion in the moonpool and rigid-body motions. Dedicated two-dimensional experiments have been performed. Two numerical hybrid methods, which have previously been applied to related problems, are further developed. Both numerical methods couple potential and viscous flow. The semi-nonlinear hybrid method uses linear free-surface and body-boundary conditions. The other one uses fully nonlinear free-surface and body-boundary conditions. The harmonic polynomial cell method solves the Laplace equation in the potential flow domain, while the finite volume method solves the Navier–Stokes equations in the viscous flow domain near the body. Results from the two codes are compared with the experimental data. The nonlinear hybrid method compares well with the data, while certain discrepancies are observed for the semi-nonlinear method. In particular, the roll motion is over-predicted by the semi-nonlinear hybrid method. Error sources in the semi-nonlinear hybrid method are discussed. The moonpool strongly affects heave motions in a frequency range around the piston-mode resonance frequency of the moonpool. No resonant water motions occur in the moonpool at the piston-mode resonance frequency. Instead large moonpool motions occur at a heave natural frequency associated with small damping near the piston-mode resonance frequency. PMID:25512594
An intrinsic growth instability in isotropic materials leads to quasi-two-dimensional nanoplatelets
Riedinger, Andreas; Ott, Florian D.; Mule, Aniket; Mazzotti, Sergio; Knüsel, Philippe N.; Kress, Stephan J. P.; Prins, Ferry; Erwin, Steven C.; Norris, David J.
2017-07-01
Colloidal nanoplatelets are atomically flat, quasi-two-dimensional sheets of semiconductor that can exhibit efficient, spectrally pure fluorescence. Despite intense interest in their properties, the mechanism behind their highly anisotropic shape and precise atomic-scale thickness remains unclear, and even counter-intuitive for commonly studied nanoplatelets that arise from isotropic crystal structures (such as zincblende CdSe and lead halide perovskites). Here we show that an intrinsic instability in growth kinetics can lead to such highly anisotropic shapes. By combining experimental results on the synthesis of CdSe nanoplatelets with theory predicting enhanced growth on narrow surface facets, we develop a model that explains nanoplatelet formation as well as observed dependencies on time and temperature. Based on standard concepts of volume, surface and edge energies, the resulting growth instability criterion can be directly applied to other crystalline materials. Thus, knowledge of this previously unknown mechanism for controlling shape at the nanoscale can lead to broader libraries of quasi-two-dimensional materials.
Jamming patterns in a two-dimensional hopper
Kiwing To
2005-06-01
We report experimental studies of jamming phenomenon of monodisperse metal disks falling through a two-dimensional hopper when the hopper opening is larger than three times the size of the disks. For each jamming event, the configuration of the arch formed at the hopper opening is studied. The cumulative distribution functions () for hoppers of opening size d are measured. (Here is the horizontal component of the arch vector, which is defined as the displacement vector from the center of the first disk to the center of the last disk in the arch.) We found that the distribution of () can be collasped into a master curve () = ()() that decays exponentially for > 4. The scaling factor () is a decreasing function of d and is approximately proportional to the jamming probability.
Thermal conductivity of disordered two-dimensional binary alloys.
Zhou, Yang; Guo, Zhi-Xin; Cao, Hai-Yuan; Chen, Shi-You; Xiang, Hong-Jun; Gong, Xin-Gao
2016-10-20
Using non-equilibrium molecular dynamics simulations, we have studied the effect of disorder on the thermal conductivity of two-dimensional (2D) C1-xNx alloys. We find that the thermal conductivity not only depends on the substitution concentration of nitrogen, but also strongly depends on the disorder distribution. A general linear relationship is revealed between the thermal conductivity and the participation ratio of phonons in 2D alloys. Localization mode analysis further indicates that the thermal conductivity variation in the ordered alloys can be attributed to the number of inequivalent atoms. As for the disordered alloys, we find that the thermal conductivity variation can be described by a simple linear formula with the disorder degree and the substitution concentration. The present study suggests some general guidance for phonon manipulation and thermal engineering in low dimensional alloys.
Nematic Equilibria on a Two-Dimensional Annulus
Lewis, A. H.
2017-01-16
We study planar nematic equilibria on a two-dimensional annulus with strong and weak tangent anchoring, in the Oseen–Frank theoretical framework. We analyze a radially invariant defect-free state and compute analytic stability criteria for this state in terms of the elastic anisotropy, annular aspect ratio, and anchoring strength. In the strong anchoring case, we define and characterize a new spiral-like equilibrium which emerges as the defect-free state loses stability. In the weak anchoring case, we compute stability diagrams that quantify the response of the defect-free state to radial and azimuthal perturbations. We study sector equilibria on sectors of an annulus, including the effects of weak anchoring and elastic anisotropy, giving novel insights into the correlation between preferred numbers of boundary defects and the geometry. We numerically demonstrate that these sector configurations can approximate experimentally observed equilibria with boundary defects.
Isolated structures in two-dimensional optical superlattice
Zou, Xin-Hao; Yang, Bao-Guo; Xu, Xia; Tang, Peng-Ju; Zhou, Xiao-Ji
2017-10-01
Overlaying commensurate optical lattices with various configurations called superlattices can lead to exotic lattice topologies and, in turn, a discovery of novel physics. In this study, by overlapping the maxima of lattices, a new isolated structure is created, while the interference of minima can generate various "sublattice" patterns. Three different kinds of primitive lattices are used to demonstrate isolated square, triangular, and hexagonal "sublattice" structures in a two-dimensional optical superlattice, the patterns of which can be manipulated dynamically by tuning the polarization, frequency, and intensity of laser beams. In addition, we propose the method of altering the relative phase to adjust the tunneling amplitudes in "sublattices". Our configurations provide unique opportunities to study particle entanglement in "lattices" formed by intersecting wells and to implement special quantum logic gates in exotic lattice geometries.
Pattern Coarsening in a Two Dimensional Hexagonal System
Chaikin, Paul
2008-03-01
We have been studying the ordering, annealing, coarsening and alignment of two dimensional periodically ordered structures in thin films of diblock copolymers*. Coarsening by dislocation and disclination annihilation is clearly observed in AFM studies of monolayer films of cylindrical patterns with a time dependence given by t^α, with α about 1/4. However in hexagonal structures the mechanism is less well defined and appears to involve the collapse of small grains entrained in the grain boundaries of larger domains. Remarkably the exponent of α about 1/4 remains. We also report on shear aligned samples and samples quenched in a gradient after alignment. * Harrison C, Angelescu DE, Trawick M, Cheng ZD, Huse DA, Chaikin PM, Vega DA, Sebastian JM, Register RA, Adamson DH, EUROPHYSICS LETTERS 67 800-806 (2004)
Diffusion in the two-dimensional nonoverlapping Lorentz gas
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.
Isolated Structures in Two-Dimensional Optical Superlattice
Zou, Xinhao; Xu, Xia; Tang, Pengju; Zhou, Xiaoji
2016-01-01
Overlaying commensurate optical lattices with various configurations called superlattices can lead to exotic lattice topologies and, in turn, a discovery of novel physics. In this study, by overlapping the maxima of lattices, a new isolated structure is created, while the interference of minima can generate various "sublattice" patterns. Three different kinds of primitive lattices are used to demonstrate isolated square, triangular, and hexagonal "sublattice" structures in a two-dimensional optical superlattice, the patterns of which can be manipulated dynamically by tuning the polarization, frequency, and intensity of laser beams. In addition, we propose the method of altering the relative phase to adjust the tunneling amplitudes in "sublattices." Our configurations provide unique opportunities to study particle entanglement in "lattices" formed by intersecting wells and to implement special quantum logic gates in exotic lattice geometries.
Critical phenomena in the majority voter model on two-dimensional regular lattices.
Acuña-Lara, Ana L; Sastre, Francisco; Vargas-Arriola, José Raúl
2014-05-01
In this work we studied the critical behavior of the critical point as a function of the number of nearest neighbors on two-dimensional regular lattices. We performed numerical simulations on triangular, hexagonal, and bilayer square lattices. Using standard finite-size scaling theory we found that all cases fall in the two-dimensional Ising model universality class, but that the critical point value for the bilayer lattice does not follow the regular tendency that the Ising model shows.
Performance of Thomas-Fermi and linear response approaches in periodic two-dimensional systems
Calderin, L; Stott, M J [Department of Physics, Queen' s University, Kingston, Ontario, K7 L 3N6 (Canada)], E-mail: calderin@physics.queensu.ca, E-mail: stott@mjs.phy.queensu.ca
2010-04-16
A study of the performance of Thomas-Fermi and linear response theories in the case of a two-dimensional periodic model system is presented. The calculated density distribution and total energy per unit cell compare very well with exact results except when there is a small number of particles per cell, even though the potential has narrow tight-binding bands. The results supplement earlier findings of Koivisto and Stott for a localized impurity in a two-dimensional uniform gas.
Visualising the strain distribution in suspended two-dimensional materials under local deformation
Elibol, Kenan; Bayer, Bernhard C.; Hummel, Stefan; Kotakoski, Jani; Argentero, Giacomo; Meyer, Jannik C.
2016-06-01
We demonstrate the use of combined simultaneous atomic force microscopy (AFM) and laterally resolved Raman spectroscopy to study the strain distribution around highly localised deformations in suspended two-dimensional materials. Using the AFM tip as a nanoindentation probe, we induce localised strain in suspended few-layer graphene, which we adopt as a two-dimensional membrane model system. Concurrently, we visualise the strain distribution under and around the AFM tip in situ using hyperspectral Raman mapping via the strain-dependent frequency shifts of the few-layer graphene’s G and 2D Raman bands. Thereby we show how the contact of the nm-sized scanning probe tip results in a two-dimensional strain field with μm dimensions in the suspended membrane. Our combined AFM/Raman approach thus adds to the critically required instrumental toolbox towards nanoscale strain engineering of two-dimensional materials.
Electrical and optoelectronic properties of two-dimensional materials
Wang, Qiaoming
Electrical and optoelectronic properties of bulk semiconductor materials have been extensively explored in last century. However, when reduced to one-dimensional and two-dimensional, many semiconductors start to show unique electrical and optoelectronic behaviors. In this dissertation, electrical and optoelectronic properties of one-dimensional (nanowires) and two-dimensional semiconductor materials are investigated by various techniques, including scanning photocurrent microscopy, scanning Kelvin probe microscopy, Raman spectroscopy, photoluminescence, and finite-element simulations. In our work, gate-tunable photocurrent in ZnO nanowires has been observed under optical excitation in the visible regime, which originates from the nanowire/substrate interface states. This gate tunability in the visible regime can be used to enhance the photon absorption efficiency, and suppress the undesirable visible-light photodetection in ZnO-based solar cells. The power conversion efficiency of CuInSe2/CdS core-shell nanowire solar cells has been investigated. The highest power conversion efficiency per unit area/volume is achieved with core diameter of 50 nm and the thinnest shell thickness. The existence of the optimal geometrical parameters is due to a combined effect of optical resonances and carrier transport/dynamics. Significant current crowding in two-dimensional black phosphorus field-effect transistors has been found, which has been significantly underestimated by the commonly used transmission-line model. This current crowding can lead to Joule heating close to the contacts. New van der Waals metal-semiconductor junctions have been mechanically constructed and systematically studied. The photocurrent on junction area has been demonstrated to originate from the photothermal effect rather than the photovoltaic effect. Our findings suggest that a reasonable control of interface/surface state properties can enable new and beneficial functionalities in nanostructures. We
Optical Spectroscopy of Two Dimensional Graphene and Boron Nitride
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
Discrete Holomorphicity at Two-Dimensional Critical Points
Cardy, John
2009-12-01
After a brief review of the historical role of analyticity in the study of critical phenomena, an account is given of recent discoveries of discretely holomorphic observables in critical two-dimensional lattice models. These are objects whose correlation functions satisfy a discrete version of the Cauchy-Riemann relations. Their existence appears to have a deep relation with the integrability of the model, and they are presumably the lattice versions of the truly holomorphic observables appearing in the conformal field theory (CFT) describing the continuum limit. This hypothesis sheds light on the connection between CFT and integrability, and, if verified, can also be used to prove that the scaling limit of certain discrete curves in these models is described by Schramm-Loewner evolution (SLE).
Two-dimensional static deformation of an anisotropic medium
Kuldip Singh; Dinesh Kumar Madan; Anita Goel; Nat Ram Garg
2005-08-01
The problem of two-dimensional static deformation of a monoclinic elastic medium has been studied using the eigenvalue method, following a Fourier transform. We have obtained expressions for displacements and stresses for the medium in the transformed domain. As an application of the above theory, the particular case of a normal line-load acting inside an orthotropic elastic half-space has been considered in detail and closed form expressions for the displacements and stresses are obtained. Further, the results for the displacements for a transversely isotropic as well as for an isotropic medium have also been derived in the closed form. The use of matrix notation is straightforward and avoids unwieldy mathematical expressions. To examine the effect of anisotropy, variations of dimensionless displacements for an orthotropic, transversely isotropic and isotropic elastic medium have been compared numerically and it is found that anisotropy affects the deformation signiﬁcantly.
Cooperation in two-dimensional mixed-games
Amaral, Marco A; Wardil, Lucas
2015-01-01
Evolutionary game theory is a common framework to study the evolution of cooperation, where it is usually assumed that the same game is played in all interactions. Here, we investigate a model where the game that is played by two individuals is uniformly drawn from a sample of two different games. Using the master equation approach we show that the random mixture of two games is equivalent to play the average game when (i) the strategies are statistically independent of the game distribution and (ii) the transition rates are linear functions of the payoffs. We also use Monte-Carlo simulations in a two dimensional lattice and mean-field techniques to investigate the scenario when the two above conditions do not hold. We find that even outside of such conditions, several quantities characterizing the mixed-games are still the same as the ones obtained in the average game when the two games are not very different.
Analysis of Two-Dimensional Electrophoresis Gel Images
Pedersen, Lars
2002-01-01
This thesis describes and proposes solutions to some of the currently most important problems in pattern recognition and image analysis of two-dimensional gel electrophoresis (2DGE) images. 2DGE is the leading technique to separate individual proteins in biological samples with many biological...... the methods developed in the literature specifically for matching protein spot patterns, the focus is on a method based on neighbourhood relations. These methods are applied to a range of 2DGE protein spot data in a comparative study. The point pattern matching requires segmentation of the gel images...... and since the correct image segmentation can be difficult, a new alternative approach, exploiting prior knowledge from a reference gel about the protein locations to segment an incoming gel image, is proposed....
Superfluid phase transition in two-dimensional excitonic systems
Apinyan, V.; Kopeć, T.K., E-mail: kopec@int.pan.wroc.pl
2014-03-01
We study the superfluid phase transition in the two-dimensional (2D) excitonic system. Employing the extended Falicov–Kimball model (EFKM) and considering the local quantum correlations in the system composed of conduction band electrons and valence band holes we demonstrate the existence of the excitonic insulator (EI) state in the system. We show that at very low temperatures, the particle phase stiffness in the pure-2D excitonic system, governed by the non-local cross correlations, is responsible for the vortex–antivortex binding phase-field state, known as the Berezinskii–Kosterlitz–Thouless (BKT) superfluid state. We demonstrate that the existence of excitonic insulator phase is a necessary prerequisite, leading to quasi-long-range order in the 2D excitonic system.
Symmetry breaking of solitons in two-dimensional complex potentials
Yang, Jianke
2014-01-01
Symmetry breaking is reported for continuous families of solitons in the nonlinear Schr\\"odinger equation with a two-dimensional complex potential. This symmetry-breaking bifurcation is forbidden in generic complex potentials. However, for a special class of partially parity-time-symmetric potentials, such symmetry breaking is allowed. At the bifurcation point, two branches of asymmetric solitons bifurcate out from the base branch of symmetry-unbroken solitons. Stability of these solitons near the bifurcation point are also studied, and two novel stability properties for the bifurcated asymmetric solitons are revealed. One is that at the bifurcation point, zero and simple imaginary linear-stability eigenvalues of asymmetric solitons can move directly into the complex plane and create oscillatory instability. The other is that the two bifurcated asymmetric solitons, even though having identical powers and being related to each other by spatial mirror reflection, can possess different types of unstable eigenval...
Two dimensional fractional projectile motion in a resisting medium
Rosales, Juan; Guía, Manuel; Gómez, Francisco; Aguilar, Flor; Martínez, Juan
2014-07-01
In this paper we propose a fractional differential equation describing the behavior of a two dimensional projectile in a resisting medium. In order to maintain the dimensionality of the physical quantities in the system, an auxiliary parameter k was introduced in the derivative operator. This parameter has a dimension of inverse of seconds (sec)-1 and characterizes the existence of fractional time components in the given system. It will be shown that the trajectories of the projectile at different values of γ and different fixed values of velocity v 0 and angle θ, in the fractional approach, are always less than the classical one, unlike the results obtained in other studies. All the results obtained in the ordinary case may be obtained from the fractional case when γ = 1.
Mechanically driven growth of quasi-two dimensional microbial colonies
Farrell, F D C; Marenduzzo, D; Waclaw, B
2013-01-01
We study colonies of non-motile, rod-shaped bacteria growing on solid substrates. In our model, bacteria interact purely mechanically, by pushing each other away as they grow, and consume a diffusing nutrient. We show that mechanical interactions control the velocity and shape of the advancing front, which leads to features that cannot be captured by established Fisher-Kolmogorov models. In particular, we find that the velocity depends on the elastic modulus of bacteria or their stickiness to the surface. Interestingly, we predict that the radius of an incompressible, strictly two-dimensional colony cannot grow linearly in time. Importantly, mechanical interactions can also account for the nonequilibrium transition between circular and branching colonies, often observed in the lab.
Vibrational Properties of a Two-Dimensional Silica Kagome Lattice.
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.
Entropic Barriers for Two-Dimensional Quantum Memories
Brown, Benjamin J.; Al-Shimary, Abbas; Pachos, Jiannis K.
2014-03-01
Comprehensive no-go theorems show that information encoded over local two-dimensional topologically ordered systems cannot support macroscopic energy barriers, and hence will not maintain stable quantum information at finite temperatures for macroscopic time scales. However, it is still well motivated to study low-dimensional quantum memories due to their experimental amenability. Here we introduce a grid of defect lines to Kitaev's quantum double model where different anyonic excitations carry different masses. This setting produces a complex energy landscape which entropically suppresses the diffusion of excitations that cause logical errors. We show numerically that entropically suppressed errors give rise to superexponential inverse temperature scaling and polynomial system size scaling for small system sizes over a low-temperature regime. Curiously, these entropic effects are not present below a certain low temperature. We show that we can vary the system to modify this bound and potentially extend the described effects to zero temperature.